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The effects of nutrients and moisture on soil nutrient availability, nutrient uptake, tissue nutrient… Brockley, Robert Peter 1981

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THE EFFECTS OF NUTRIENTS AND MOISTURE ON SOIL NUTRIENT AVAILABILITY, NUTRIENT UPTAKE, TISSUE NUTRIENT CONCEN-TRATION, AND GROWTH OF DOUGLAS-FIR SEEDLINGS ROBERT PETER BROCKLEY B.S.F., The University of B r i t i s h Columbia, 1976 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF FORESTRY i n • THE FACULTY OF GRADUATE STUDIES (Faculty of Forestry) We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA (c) Robert Peter Brockley, 1981 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. I t i s understood that copying or p u b l i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of fh^e^ST^y  The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 ^ e ^ T E ^ i a f e / e i l i 1 7 % / DE-6 (2/79) / i i ABSTRACT A k x 4 f a c t o r i a l experiment was established to study the effects of s o i l nutrients (N) and s o i l moisture (M) on s o i l nutrient a v a i l a b i l i t y , seedling growth, nutrient uptake, and tissue nutrient concentration. Other objectives of the study were to test for the existence and significance of a. nutrient x moisture i n t e r a c t i o n , to attempt to correlate some mea.sures of seedling growth with l e v e l s of s p e c i f i c nutrients i n seedling tissue and s o i l , and to ascertain whether certain correlations are affected by s o i l moisture l e v e l . The sixteen treatment combinations of nutrients and moisture were applied to potted Douglas-fir seedlings and arranged i n a. randomized complete block design on a greenhouse bench. S o i l and tissue parameters generally displayed highly s i g n i f i c a n t differences due to both moisture and nutrients. The magnitude of difference and the d i r e c t i o n of change varied depending on the p a r t i c u l a r nutrient and moisture treatment ( i . e . N x M interactions were generally highly s i g n i f i c a n t ) , and the parameter i n question. With tissue nutrient l e v e l s , differences also varied with the type of tissue ( i . e . folia.ge, stems, or roots), and whether the l e v e l of the p a r t i c u l a r nutrient wa.s expressed as concentration or content. S o i l moisture was shown to have a. strong i n d i r e c t / i i i influence on the amount of available s o i l nitrogen as well as the form i n which i t i s taken up by seedlings. The form of nitrogen not only appeared to influence seedling growth but may have also affected the upta.ke of other plant nutrients (e.g. P and Ca). High concentrations of a v a i l -able s o i l nitrogen appeared to upset delicate nutrient balances within seedlings, r e s u l t i n g i n induced nutrient deficiencies and reduced seedling growth. Direct antagon-isms between s p e c i f i c nutrients (e.g. N and P, K and Ca.) were also demonstrated. Increa.sed s o i l nutrient supply generally had a. strong negative influence on mean seedling root weight and root/shoot r a t i o . Mso, s o i l moisture and nutrients generally ha.d favorable and unfavorable eff e c t s , respec-t i v e l y , on seedling mycorrhizae. Under conditions of moisture stress, f o l i a r concentrations were shown to p a r t i a l l y mask nutrient d e f i c i e n c i e s . Only when the growth-limiting effect of s o i l moisture wa.s a l l e v i a t e d did f o l i a r concentrations of the l i m i t i n g nutrient(s) f a l l to severe deficiency l e v e l s , even though the upta.ke of the defic i e n t nutrient(s) gen-e r a l l y increased. These r e s u l t s suggested a. closer exam-ina t i o n of the moisture-supplying a b i l i t y of a. s i t e may be warranted when evaluating the results of f o l i a r anal-y s i s . C r i t i c a l f o l i a r concentrations of some nutrients may i n fa c t vary depending on s i t e moisture conditions. / i v Highly s i g n i f i c a n t p o s i t i v e correlations between f o l i a r nutrient content and seedling growth were generally obtained only for those s o i l nutrients which were i n -adequately supplied. Correlations were generally strong-est i n those treatments where s o i l moisture was not a. growth-limiting factor. Results suggest that the higher s i t e productivity often evident on 'seepage s i t e s ' might often be l a r g e l y due to the favorable influence of s o i l moisture on nut-r i e n t a v a i l a b i l i t y and uptake, rather than to the i n -creased amounts of nutrients supplied i n the seepage water. A TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS v LIST OF TABLES v i i i LIST OF FIGURES x v i i ACKNOWLEDGEMENTS x v i i i INTRODUCTION 1 CHAPTER 1. LITERATURE REVIEW 4 • 1.1 Introduction 4 1.2 S o i l Analysis 5 1.3 F o l i a r Analysis 7 1.4 S o i l Moisture 14 1.41 Nutrient Transport 14 1.42 Root Growth and Function 17 1.-+3 S o i l Solution Concentration 18 1.44 Microbial A c t i v i t y 19 1.45 Effect of S o i l Moisture on Nutrient Uptake and Tissue Nutrient Concen-t r a t i o n 22 2. METHODS AND MATERIALS 27 2.1 Experimental Design 27 2.2 Experimental Preparations 28 2.21 S o i l Preparation 28 2 .22 : S o i l Nutrients 29 2 .23 S o i l Moisture Regulation 30 2.24 Seedling Germination 39 2 .3 Experimental Environment 4 l 2 . 4 Seedling Harvest 43 A i Table of Contents (cont'd) Page 2.5 S o i l Analysis 45 2 .6 Seedling Tissue Analysis 46 2.61 Preparation 46 2.62 Tissue Digestion 46 2.63 Analysis 49 2 .7 S t a t i s t i c a l Analysis 51 3. RESULTS AND DISCUSSION: EFFECTS OF NUTRIENT AND MOISTURE REGIMES ON SOIL AND TISSUE 52 3.1 Summary of Main Eff e c t s 52 3.2 Exchangeable S o i l Cations 57 J.3 S o i l Ammonium Nitrogen , 60 3 .4 S o i l Nitrate Nitrogen 62 3.5 Total 'Available' Nitrogen i n S o i l 65 3 .6 S o i l pH 71 3.7 S o i l E l e c t r i c a l Conductivity 74 3.8 F o l i a r Damage 77 3.9 Seedling Growth 80 3.10 Tissue Nitrogen 90 3.11 Tissue Phosphorus 97 3.12 Tissue Potassium 108 3.13 Tissue Calcium H 4 3.14 Tissue Magnesium 124 3.15 Tissue Manganese 129 4. RESULTS AND DISCUSSION: CORRELATIONS INVOLVING OTHER RELATIONSHIPS BETWEEN VARIABLES 133 4.1 Introduction 133 4 .2 F o l i a r Nutrients versus Seedling Weight.... 134 4 .3 S o i l Nutrient A v a i l a b i l i t y versus Seedling Weight.. 136 4 . 4 S o i l Nutrients versus F o l i a r Nutrients 138 5. CONCLUSIONS 140 LITERATURE CITED 144 / v i i Table of Contents (cont'd) Page APPENDICES 1 S o i l analys is p r i o r to nutr ient addit ions 163 2 Water re tent ion curve of experimental s o i l 165 3 Types and amounts of nutr ient solut ions added to the experimental s o i l 167 k Hygrometer c a l i b r a t i o n 169 / v i i i LIST OF TABLES Table Page 1 Amount of nutrient added r e l a t i v e to a v a i l -able (N,P) or exchangeable (Ca,Mg) amount i n i t i a l l y present i n the s o i l 31 2 Analysis of variance of s o i l and tissue nutrient and seedling growth parameters.... 53 3 Exchangeable s o i l K (meq/lOOg), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and mois-ture regime (M) 58 4 Exchangeable s o i l Ca (meq/lOOg), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and mois-ture regime (M) 58 5 Exchangeable s o i l Mg (meq/lOOg), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and mois-ture regime (M) 61 6 Exchangeable s o i l NH^-N (ppm), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and mois-ture regime (M) 61 7 Extractable s o i l NO^-N (ppm), i n r e l a t i o n . to r e l a t i v e nutrient regime (N) and mois-ture regime (M) 63 8 Sum of exchangeable s o i l NH^-N (ppm) and extractable s o i l NO^-N (ppm), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and mois-ture regime (M) 66 A x L i s t of Tables (cont'd) : Table Page 9 Percentage of added N recovered at the end of the experiment, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and mois-ture regime (M) 67 10 S o i l pH, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 72 11 S o i l e l e c t r i c a l conductivity (micromhos), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 75 12 F o l i a r damage, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 78 13 Seedling shoot height (cm), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and mois-ture regime (M) 82 lk Amount of seedling shoot growth (cm) during the treatment period, i n r e l a t i o n to r e l -ative nutrient regime (N) and moisture regime (M) 82 15 Seedling root length (cm), i n r e l a t i o n to r e l a t i v e nutrient regime (PJ) and moisture regime (M) . . . 83 A L i s t of Tables (cont'd) Table Page 16 Seedling stem diameter (cm), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) 33 17 Seedling root weight (g), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and mois-ture regime (M) 84 18 Seedling stem weight (g), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and mois-ture regime (M) 84 19 Live fo l iage weight per seedl ing (g) , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) ^x. and moisture regime (M) 85 20 Dead fo l iage weight per seedl ing (g) , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) 85 21 T o t a l seedl ing weight (g), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and mois-ture regime (M) 86 22 Seedling root/shoot r a t i o (g/g), i n r e l -a t ion to r e l a t i v e nutr ient regime (N) and moisture regime (M) 86 23. Concentration (%) of ni trogen i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) 91 A i L i s t of Tables (cont'd) Tables Page 24 Concentration \%) of nitrogen i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 91 25 Concentration {%) of nitrogen i n roots, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 92 26 Weight (mg) of nitrogen per seedling i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 92 27 Weight (mg) of nitrogen per seedling i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 93 28 Weight (mg) of nitrogen per seedling i n roots, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) •• 93 29 Total weight (mg) of nitrogen per seedling, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 94 30 T o t a l weight (mg) of phosphorus per seed-l i n g , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 94 31 Weight (mg) of phosphorus per seedling i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 100 / x i i L i s t of Tables (cont'd) Table Page 32 Weight (mg) of phosphorus per seedling i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 100 33 Weight (mg) of phosphorus per seedling i n roots, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 101 34 Concentration {%) of phosphorus i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 101 35 Concentration {%) of phosphorus i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M). . 102 36 Concentration {%) of phosphorus i n roots, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 102 37 Nitrogen/phosphorus r a t i o i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 106 38 Concentration {%) of potassium i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 106 ,39 Concentration {%) of potassium i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 109 / x i i i L i s t of Tables (cont'd) Table Page 40 Concentration (%) of potassium i n roots, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 109 41 Weight (mg) of potassium per seedling i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) I l l 42 Weight (mg) of potassium per seedling i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) I l l 43 Weight (mg) of potassium per seedling i n roots, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M.) 112 44 Total weight (mg) of potassium per seedling, i n r e l a t i o n to r e l a t i v e nutrient regime (N_) and moisture regime (M) 112 45 Concentration {%) of calcium i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N_) and moisture regime (M) •> 115 46 Concentration {%) of calcium i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 115 47 Concentration {%) of calcium i n roots, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 116 / x i v L i s t of Tables (cont'd) Table - Page 48 Weight (mg) of calcium per seedl ing i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nut-r i e n t regime (N) and moisture regime (M).... 116 ^9 Weight (mg) of calcium per seedl ing i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) 117 50 Weight (mg) of calcium per seedl ing i n root s , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) 117 51 T o t a l weight (mg) of calcium per seedl ing , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) 122 52 Concentration {%) of magnesium i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) _ 122 53 Concentration {%) of magnesium i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) 125 5^ Concentration {%) of magnesium i n roots , . i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) 125 55 Weight (mg) of magnesium per seedl ing i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) 126 /xv L i s t of Tables (cont'd) Table Page 56 Weight (rag) of magnesium per seedling i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 126 57 Weight (mg) of magnesium per seedling i n roots, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 127 58 Total weight (mg) of magnesium per seedling, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime , (M) 127 59 Concentration (ppm) of manganese i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 130 60 Concentration (ppm) of manganese i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) 130 61 Concentration (ppm) of manganese i n roots, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) . 131 62 Correlations between mean seedling weight and f o l i a r nutrient concentrations and contents 135 63 Correlations between mean seedling weight and s o i l nutrients 137 / x v i L i s t of Tables (cont'd) Table Page 64 Correla.tions between s o i l nutr ients and f o l i a r nutr ients 139 / x v i i LIST OF FIGURES Figure Page 1 Schematic r e l a t i o n s h i p "between growth and f o l i a r nutr ient concentration 8 2 C a l i b r a t i o n curve showing r e l a t i o n s h i p between microvoltmeter' output U v ) and osmotic p o t e n t i a l (bars) 36 3 T y p i c a l mycorrhizal development i n low nutr ient - high moisture treatments 9 8 4 T y p i c a l mycorrhizal development i n high nutr ient - high moisture treatments 105 / x v i i i ACKNOWLEDGEMENTS The f i n a n c i a l assistance of the Facul ty of Forestry and the U n i v e r s i t y of B r i t i s h Columbia i s g ra te fu l ly ac-knowledged. Experimentation and laboratory analyses were great ly f a c i l i t a t e d by the advice and cooperation of Bernie von Spindler , Va ler ie M i l e s , and B i l l Cheang. I would l i k e to thank my committee members for t h e i r ass istance. I am e spec i a l ly grate fu l to my thes i s advisor , Dr. T .M. B a l l a r d , for hi s sage advice at the beginning of the pro jec t , and h i s guidance during the var-ious stages of the research. I also thank my daughter, L i s a , who unknowingly provided me with a much needed burst of energy during the l a t t e r stages of my work. F i n a l l y , I of fer my warm appreciat ion to my wife , Susan, for reviewing and typing the manuscript and without whose patience and encouragement t h i s endeavour would not have been pos s ib le . /I INTRODUCTION S o i l and f o l i a r analysis techniques have been used extensively to evaluate s o i l f e r t i l i t y and tree nutrient status, and to diagnose nutrient d e f i c i e n c i e s l i m i t i n g tree growth. The value of these techniques r e l i e s on the existence of a dir e c t r e l a t i o n s h i p between s o i l and/or f o l i a r nutrient status and tree growth. I f t h i s r e l a t i o n s h i p can be demonstrated, i t should be possible, through further study, to es t a b l i s h ' c r i t i c a l ' soil,and f o l i a r l e v e l s for various nutrients, and to use these methods to predict p o t e n t i a l responsiveness of forest trees to the addition of nutrient amendments. While s o i l , and e s p e c i a l l y f o l i a r , analyses have met with some success i n forestry, these techniques often do not accurately r e f l e c t nutrient a v a i l a b i l i t y , tree n u t r i t i o n , or growth response p o t e n t i a l . These f a i l i n g s can be at least p a r t i a l l y explained by defective or inconsistent f o l i a r and s o i l sampling techniques and/or inadequate knowledge of the mechanisms and strategies involved i n the uptake of nutrients by tree roots i n forest s o i l s . However, while further investigations related to the above problems are undoubtedly warranted, i t i s very apparent that diagnostic inconsistencies are lar g e l y due to factors other than these. One important factor which was i n s u f f i c i e n t l y studied i n some previous work i s s o i l water. While many /2 workers have shown that s o i l water can he an important factor l i m i t i n g tree growth, fewer studies have examined the ef fects of s o i l moisture on tree n u t r i t i o n . S o i l water not only i s important i n terms of the p h y s i o l o g i c a l funct ioning of t rees , "but also influences nutr ient a v a i l a b i l i t y , t ransport , uptake, and t i ssue nutr ient concentrat ion. Therefore, i t would seem important that further inves t iga t ions regarding the n u t r i t i o n a l status and growth of forest trees "be conducted within a s o i l moisture - s o i l nutr ient framework. Nutr ients and moisture are two of the most important factors in f luenc ing tree growth and n u t r i t i o n . Though the i n d i v i d u a l ro le s of each have been extensively s tudied , t h e i r combined ef fects have l a rge ly been ignored. Nutr ients and moisture have been shown to have both a separate and combined effect on s o i l nutr ient a v a i l a b i l i t y , seedl ing growth, nutr ient uptake and t i ssue nutr ient . * concentrat ion. Lack of understanding of s o i l nutr ient x moisture in terac t ions prevents c lear i d e n t i f i c a t i o n of the way i n which growth and f o l i a r nutr ient composition are regulated, which i n turn l i m i t s the p o t e n t i a l for refinement of f o l i a r analys i s as a diagnost ic t o o l . Thi s thes i s reports r e su l t s of a study which was s p e c i f i c a l l y designed to examine some of the above questions. /3 The objectives of the experiment were threefold: 1) To study the i n d i v i d u a l e f f e c t s of s o i l moisture and s o i l nutrients on s o i l nutrient a v a i l a b i l i t y , seedling growth, nutrient uptake, and tissue nutrient concentration. 2')> To test for the existence and significance of a nutrient x moisture i n t e r a c t i o n , and study the mechanisms involved i n the i n t e r a c t i o n . 3) To attempt to correlate some measures of seedling growth with l e v e l s of s p e c i f i c nutrients i n seedling tissue and s o i l , and to study whether certain correlations are affected by s o i l moisture l e v e l . These objectives were accomplished by establishing a f a c t o r i a l experiment with four l e v e l s of s o i l nutrients and four l e v e l s of s o i l moisture. The various treatment combinations were applied to potted Douglas-fir seedlings and arranged i n a randomized complete block design on a greenhouse bench. A CHAPTER 1 LITERATURE REVIEW 1.1 Introduction This review out l ines the role of s o i l and f o l i a r analys is techniques as diagnost ic tool s i n evaluating the nutr ient- supply ing a b i l i t y of s o i l and the n u t r i t i o n a l status of p lant s . The separate and combined ef fects that s o i l moisture and s o i l nutr ient s may have on s o i l nutr ient a v a i l a b i l i t y , nutr ient uptake and t i s sue nutr ient concentrat ion, and t h e i r influence on the diagnost ic ef fect iveness of s o i l and f o l i a r analyses are also reviewed. /5 1.2 S o i l Analys i s Cor re l a t ion of s o i l nutr ient status with tree growth, and hence the usefulness of s o i l analys i s i n nutr ient def ic iency diagnosis , has met with l imi ted success (Armson 1973)• Some success has been experienced on s i t e s where r e l a t i v e l y acute, as opposed to i n c i p i e n t , s p e c i f i c nutr ient de f i c i enc ie s occur (Heiberg and Leaf I 9 6 O ; White and Leaf 1964; Wilde et a l . 1964a,b; P r i t c h e t t 1968; Ba l l a rd and P r i t c h e t t 1975)» and i n greenhouse bio-assay t r i a l s where more homogeneous condit ions exis t (Youngberg and Dyrness 1965; W i l l and Youngberg 1979) ' S o i l analys i s has been used extensively i n a g r i c u l t u r e , where the root ing depth, and hence nutr ient uptake of a g r i c u l t u r a l crops, i s general ly confined to a rather homogeneous plough l a y e r . A g r i c u l t u r a l crop y i e l d can be compared with s o i l chemical analys i s data y e a r l y , so that the technique of nutr ient def ic iency diagnosis and f e r t i l i z e r p r e s c r i p t i o n for a p a r t i c u l a r s o i l ser ies can be ' f ine-tuned* i n a matter of years (Bal lard 1979)• S o i l ex t rac t ion techniques most c lo se ly resembling the ' a v a i l a b i l i t y of s o i l nutr ient s to a g r i c u l t u r a l crops have been developed and tested over a number of years . The successful use of s o i l analys i s i n fores try i s complicated by many fac tor s . F i r s t of a l l , a g r i c u l t u r a l s o i l ex t rac t ion techniques may be unrepresentative of the a v a i l -a b i l i t y of nutr ient s i n forest s o i l s to trees (Viro 1961; /6 Ralston 1964; Z o t t l 1973). The 'layered' nature of forest s o i l s , mycorrhizal n u t r i t i o n , and deeper and less'homogeneous rooting habits of forest trees further complicate the picture (Waring and Youngberg 1 9 7 2 ; Armson 1973; Ballard 1979). Also, forest s o i l s have generally been found to exhibit large s p a t i a l v a r i a b i l i t y , making the procurement of representative s o i l samples d i f f i c u l t (Mader 1963; McFee and Stone 1965; Hart et a l . 1969; Usher 1970). Lastly, due to the slow growth of forest crops, ' fine-tuning 'if may require decades. Factors other than s o i l f e r t i l i t y have been shown to play important roles i n c o n t r o l l i n g forest productivity. Many workers have successfully related s o i l physical properties and topographic c h a r a c t e r i s t i c s with productivity (Gessel and Lloyd 1950; Coile 1952; Carmean 1954; Mader and Owen 1961; Pawluk and Arneman 1961; E i s 1962; Steinbrenner 1963; Ballard 1971s Brown and Lowenstein 1978). However, s o i l moisture, i n p a r t i c u l a r , i s generally singled out as having a great influence on tree growth and s i t e productivity (Waring and Youngberg 1 9 7 2 ) . The tremendous e f f e c t s o i l moisture may have on tree growth i s undoubtedly largely responsible for the limited diagnostic usefulness of s o i l analysis i n forestry. /7 1.3 F o l i a r Analysis F o l i a r analysis i s a. method used to f i n d r e lationships "between plant growth and s o i l f e r t i l i t y using a.s diagnostic c r i t e r i a mineral nutrient concentrations and "balances i n fo l i a g e (van den Burg 1976) . It i s based on the concept that the plant i t s e l f i s the best indicator of nutrient a v a i l a b i l i t y ( Smith 1962) . F o l i a r analysis has become a. popular tool f o r evaluating tree nutrient status beca.use, unlike s o i l analysis, i t r e f l e c t s nutrient a.bsorp-t i o n from the whole volume of s o i l permeated by tree roots (Ba.ule and Fricker 1970) . While other tissues such as buds, roots, and bark have been used with some success (Leaf 1 9 7 3 ) » f o l i a g e has generally been found to provide the most sen-s i t i v e and convenient measure of plant nutrient status. F o l i a r analysis has been used extensively f o r both diagnostic and predictive purposes - diagnostic i n that i t may be used to determine nutrient requirements of plants and to diagnose s p e c i f i c nutrient d e f i c i e n c i e s , and predictive i n that i t may be used to predict which plants exhibit greatest p o t e n t i a l f o r growth response to nutrient addition (Richards and Bevege 1972). The basis f o r interpretation of f o l i a r analysis i s dependent on two fac t o r s : 1) the uptake and d i s t r i b u t i o n of nutrients by plants a.nd 2) the quantitative r e l a t i o n s h i p /8 between f o l i a r nutr ient concentration and growth (Lundegardh 195^ from Smith 1962). Figure 1 schematical ly depicts the l a t t e r . FIGURE 1. Schematic r e l a t i o n s h i p between growth and f o l i a r nutr ient concentration C A Nutrient Concentration i n Foliage Macy (1936) f e l t the key to i n t e r p r e t i n g such a r e l a t i o n s h i p was to d iv ide the curve into four d i s t i n c t zones ( F i g . 1 ) . He f e l t a c r i t i c a l l e v e l for a given nutr ient i n each kind of plant could be i d e n t i f i e d "above which there i s a luxury consumption and below which there i s poverty adjustment, which i s almost proport ional to the def ic iency u n t i l minimum percentage i s reached." Within the zone of extreme def ic iency (A i n F i g . 1 ) , / 9 nutr ient transport into the fo l iage i s just s u f f i c i e n t to keep pace with shoot or fo l iage expansion or r e d i s t r i b u t i o n wi th in the plant (Timmer and Stone 1978). Within t h i s zone, f o l i a r nutr ient concentration i s maintained at a minimum percentage, or may ac tua l ly decrease with increas ing growth. Such a decrease i n l ea f concentration of a p a r t i c u l a r element fo l lowing addi t ion of that element, and accompanied by an increase i n y i e l d , i s general ly referred to as the 'Steenbjerg e f f ec t 1 (Steenbjerg 1954). The zone of mild def ic iency (B i n F i g . 1) i s defined as that port ion of the curve where addi t ion of a nutr ient element known to be d e f i c i e n t , r e su l t s i n an increase i n f o l i a r concentration of that element as we l l as an accompanying increase i n y i e l d . This corresponds to Macy's (1936) zone of 'poverty adjustment' , and i s the por t ion of the curve most useful i n nutr ient def ic iency diagnosis . An increase i n t i s sue nutr ient concentration above the ' c r i t i c a l l e v e l ' does not re su l t i n further growth response, and therefore represents luxury consumption (C i n F i g . 1 ) . A fo l iage nutr ient concentration may eventual ly be reached above which t o x i c i t y and growth reduction occur (D i n F i g . 1 ) . F o l i a r nutr ient concentration at the c r i t i c a l l e v e l represents 'optimum' n u t r i t i o n , since maximum y i e l d i s attained with minimum input of n u t r i e n t s . However, many / l O workers ( U l r i c h 1968; Richards and Bevege 1972) have argued that a s p e c i f i c optimum l e v e l does not ex i s t , but rather a c r i t i c a l range i n f o l i a r nutrient concentration can be i d e n t i f i e d , below which growth i s s i g n i f i c a n t l y depressed. In t h i s regard, f o l i a r concentrations known to represent ' c r i t i c a l l e v e l s ' f or growth, or ranges of concentrations known to represent nutrient d e f i c i e n c i e s , have been i d e n t i f i e d for many nutrients and tree species (Ingestad 1959, I960; Tamm 1968; van den Driessche 1969a,b; Swan 1972a,b,c,d; Everard 1973)* Nutrient concentration r a t i o s (e.g. N/S, N/P, Ca/Mg, K/Ca) have also been shown to have diagnostic value (Leyton 1957; Heilman and Gessel 1963; Ingestad 1967; Lavender 1970; K e l l y and Lambert 1972; Turner et a l . 1977) . However, much of t h i s work has been undertaken with tree seedlings grown i n a r t i f i c i a l conditions, thereby possibly l i m i t i n g i t s a p p l i c a b i l i t y to natural forest stands (Tamm 1964; Mead and Pr i t c h e t t 1971) . F o l i a r nutrient composition can be expressed i n re l a t i v e terms such as concentration ( i . e . percentage or ppm based on the mass of oven-dry foliage) or i n absolute terms such as content ( i . e . mg per leaf or per plant or per 100 needles). Unfortunately, these two terms have often been used interchangeably i n the forestry l i t e r a t u r e , leading to confusion i n the interpretation of re s u l t s (Armson 1973; Leaf 1973)• Content may best r e f l e c t actual plant uptake of / I I a nutrient, but interpretation i s generally based on f o l i a r nutrient concentration (see reviews by Leaf 1973 and van den Driessche 1974) . From a n u t r i t i o n a l viewpoint, absolute uptake of nutrients i s less important than t h e i r concentration i n the plant t i s s u e . Although t o t a l f o l i a r content of a given nutrient may be greater i n one tree than another, i t i s possible, due to d i l u t i o n e f f e c t s , for the tissue nutrient concentration of the former to be lower than that of the l a t t e r (Schomaker 1969) . F o l i a r concentration may indicate n u t r i t i o n a l stress i n the f i r s t instance and luxury consumption i n the second instance. Unfortunately, the use of f o l i a r . concentration alone does not allow d i l u t i o n e f f e c t s to be separated from antagonistic e f f e c t s (Cain 1959)- Comparison of content and concentration data i s necessary before t h i s difference can be recognized (Timmer and Stone 1978) . In actual practice, many d i f f i c u l t i e s arise i n the use and interpretation of f o l i a r analysis. Before i t can be used successfully as a diagnostic t o o l , i t must be calibrated, so that a p a r t i c u l a r a n a l y t i c a l value can be cor r e c t l y interpreted (Ballard 1979) . Under natural conditions, many sampling problems must be addressed i n order to reduce sampling v a r i a b i l i t y and 'fine-tune' the rel a t i o n s h i p between f o l i a r nutrient status and growth. In t h i s regard, the influence of factors such as crown class (Lowry and Avard 1968; Lavender 1 9 7 ° ) 1 crown ' /12 p o s i t i o n (Lowry and Avard 1965; Lavender and Carmichael 1966) , foliage age (Leyton and Armson 1955; Lavender and Carmichael 1966; Morrison 1972) , and time of year (Lowry and Avard 1969; Waring and Youngberg 197 2 ) on f o l i a r nutrient concentration have been documented. The general lack of standardized international f o l i a r sampling methods i s re f l e c t e d i n the large inventory of methods compiled byivan Goor e_t a l . (1971)-However, standardized f o l i a r sampling guidelines suggested by Gessel et_ a l . ( i960) and Heilman (1971) have gained general acceptance i n the P a c i f i c Northwest. Factors associated with sample preparation and analysis, such as laboratory technique and the choice of extraction and a n a l y t i c a l methods, may affect not only the preci s i o n and accuracy of re s u l t s but also t h e i r comparability with r e s u l t s obtained by other methods (Jones and Steyn 1973; Leaf 1973; van den Burg 1976) . Although the existence of standardized f o l i a r sampling and a n a l y t i c a l methods would undoubtedly improve the interpretive value of f o l i a r analysis, other complicating factors also hinder the successful c a l i b r a t i o n of the technique. F o l i a r nutrient concentration i s a parameter that i s not e a s i l y interpreted unless a l l factors which produced i t are known (van den Burg 1976) . Webber (197^) attributed poor c o r r e l a t i o n of s o i l and f o l i a r nutrient status with s i t e productivity to s o i l moisture stress. / l 3 van den Driessche (1974) f e l t that i f the eff e c t s of s o i l moisture could be is o l a t e d , greater precision could be achieved with f o l i a r analysis. Armson (1973) stated that "the moisture-supplying a b i l i t y of a s o i l i s one of the most common factors to affect tree growth and interact with nutrient l e v e l s . " According to Waring (1969), f o l i a r nutrient composition i s probably as much influenced by s o i l moisture as by the supply of available s o i l nutrients. /14 1.4 S o i l Moisture S o i l moisture affects plant n u t r i t i o n through i t s influence on nutrient transport to, and absorption by, plant roots, concentration of available plant nutrients i n the s o i l s olution, and s o i l microbial a c t i v i t y . Although water and nutrient absorption by plants are i n fact independent processes (except where some forms of some elements may be transported into the root by mass flow), t h e i r intimate r e l a t i o n s h i p makes i t extremely d i f f i c u l t to separate the importance of s o i l water into i t s role i n plant n u t r i t i o n and i t s role i n other plant physiological processes (Viets 1972) . The effects of s o i l water on germination, water and nutrient absorption, translocation of minerals and food, t r a n s p i r a t i o n , photosynthesis, and r e s p i r a t i o n directly; or i n d i r e c t l y affect growth (Crafts I 968 ) i A great deal of research has documented the effects of water d e f i c i t s on plant growth (see Kozlowski 1968a,b; 1972; 1976) . Excessive s o i l water has also been shown to affect physiological processes and hence growth, mainly through i t s influence on the functioning of plant roots as absorbing elements ('Black 1968) . 1.41 Nutrient Transport The uptake of nutrients by plant roots depends largely on the rate at which nutrients may move from the / 1 5 surrounding s o i l to the root surface. The a n i l i t y of s o i l water to influence the amount and rate of nutrient transport to tree roots v i a processes of mass flow and d i f f u s i o n has been discussed by Barber ( I962 ) , Gardner (1965)1 Olsen and Kemper (1968) , and others. A l l other factors being equal, increasing s o i l moisture w i l l increase the nutrient '• supply to tree roots up to the point where root aeration i s l i m i t e d . Low s o i l water content ( i . e . low s o i l water potential) l i m i t s hydra.ulic conductivity i n s o i l , thereby reducing the ea.se with which water may move to plant roots. A reduction i n transport of nutrients by mass flow ( i . e . the passive transport of nutrients i n moving water, e.g. water drawn toward roots of tr a n s p i r i n g plants ) may depend d i r e c t l y on t h i s e f f e c t of decreased water content on the s o i l ' s hydraulic conductivity, and also on the reduced s o i l water potential's e f f e c t on the water p o t e n t i a l difference between s o i l and plant. The rate of d i f f u s i o n ( i . e . the movement of soluble nutrients along nutrient concentration gradients) i n s o i l i s d i r e c t l y dependent on s o i l water content. D i f f u s i o n decrea.ses with decreased s o i l water potential due to the effe c t of s o i l water on the cross-sectional area available for d i f f u s i v e transport, the tortuos i t y of the d i f f u s i o n pathway, v i s c o s i t y of s o i l water, and ion exclusion phenomena. (Olsen and Kemper I968) . A 6 Under conditions of fa.vora.ble s o i l moisture and f e r t i l i t y , mass flow may account for v i r t u a l l y a l l of the nutrient uptake by plant roots. In f a c t , the rate of nutrient supply- under these conditions may be so great as to exceed the rate at which they can be absorbed. This would r e s u l t i n a buildup i n nutrient concentration at the root surface thereby i n i t i a t i n g a backward d i f f u s i o n of nut-r i e n t s away from the root. Under conditions of lower nutrient supply, d i f f u s i o n would be expected to play a much more important role i n nutrient transport toward roots. The r e l a t i v e importance of mass flow and d i f f u s i o n i n the transport of the various nutrient elements to plant roots i s l a r g e l y dependent on factors such as nutrient s o l u b i l i t y and plant nutrient requirements. Ions such as n i t r a t e (N0^~) generally ex i s t almost exclusively i n the solution phase (except i n s o i l s e x h i b i ting considerable anion exchange capacity) allowing them to be supplied to roots l a r g e l y by mass flow. Conversely, a r e l a t i v e l y insoluble nutrient ion such as phosphate has a. low concentration i n the s o i l s olution, necessitating that a. larger portion of i t s transport be supplied by d i f f u s i o n . Barber et a l . (1963) reported that mass flow may account f o r most of the transport of Ca, Mg, and N to a g r i c u l t u r a l crops but r e l a t i v e l y l i t t l e of the transport of P and K. The reasoning for the differences i n transport A 7 pathways between such elements as Ca and K was based largely on r e l a t i v e crop requirements for these elements. The r e l a t i v e l y low requirements for Ca would be largely met by mass flow transport. However, mass flow transport of K would generally be inadequate to s a t i s f y plant requirements. Calculated mass flow values reported by Ballard and Cole (1974) for a forest s o i l generally agree with those presented by Barber e_t a l . (1963) for calcium and potassium, but d i f f e r s u bstantially for N and P. Discrepancies may be largely attributable to differences i n the form of available nitrogen (N0-^ ~ vs. NHlj,+) , lower N a v a i l a b i l i t y , and lower P uptake by vegetation i n forest s o i l s compared with a g r i c u l t u r a l s o i l s . 1.42 Root Growth and Function S o i l water also influences the growth and function of plant roots. Inadequate s o i l moisture has been shown to affect adversely the growth and elongation of roots i n s o i l (Thorup 1 9 6 9 ; Brown 1970)* However, i t i s often not clear whether t h i s i s only a d i r e c t effect of s o i l water p o t e n t i a l , or whether i t also involves the greater mechanical strength of the d r i e r s o i l (Eavis 1972) . Whatever the cause, r e s t r i c t e d root growth reduces the a b i l i t y of roots to f u l l y e xploit the s o i l volume i n search of water and nutrients, thereby l i m i t i n g the p o t e n t i a l for nutrient transport to root / 18 surfaces. Ion uptake by plants i s an active process, requiring the expenditure of metabolic energy (Salisbury and Ross 1969) . However, i f s o i l water pote n t i a l f a l l s and plant water stress r i s e s to the point where metabolic a c t i v i t y i s in h i b i t e d , ion uptake w i l l be reduced. Olsen et a l . (1962) reported lower uptake of P by roots at low s o i l water potential even though the concentration of P at the root surface was greater than at higher potentials. Wet s o i l s have also been shown to injure roots and hence affect t h e i r functioning as absorbing elements. Because of reduced oxygen supply and root r e s p i r a t i o n , root growth and elongation as well as water and nutrient uptake may be reduced i n excessively wet s o i l s (Hosner and Leaf 1962; Hosner e_t a l . 1965; Grable and Siemer 1968) . 1.43 S o i l Solution Concentration The concentration of the s o i l solution increases with a decrease i n s o i l moisture, and vice versa (Black 1968). Few studies however, appear to have documented the ef f e c t s of s o i l moisture on s o i l nutrient concentration. Reitemeier and Richards (1944) did f i n d that concentrations of K, Mg, Na, and C l i n pressure membrane s o i l extracts did increase with decreased i n i t i a l water content. One effect of an excessively high s o i l solution concentration would be to induce greater resistance to water uptake by plant roots r e s u l t i n g from / 1 9 reduced s o i l osmotic p o t e n t i a l ( H i l l e l 1971). Schomaker (I969) found that heavy f e r t i l i z a t i o n of white pine seed-li n g s growing i n a very dry s o i l resulted i n a more serious moisture stress s i t u a t i o n than i n les s heavily f e r t i l i z e d seedlings. 1.44 Microbial A c t i v i t y S o i l microbes play many dire c t and i n d i r e c t roles i n s o i l nutrient a v a i l a b i l i t y . F i r s t of a l l , the chemical form and concentration i n which many nutrients exist i n the s o i l solution is affected by chemical reductions undertaken by s o i l microbes functioning under anaerobic conditions. As a r e s u l t of these reactions, oxygen-containing compounds may accept electrons and lose oxygen (e.g. N0^~-» NC^ ^ O - ^ ^ ) - In addition, some high-valency inorganic cations may accept electrons and become reduced to lower valency states (e.g. Mn^4"-* Mn2 + ; Fe^ +-> F e 2 + ) (Russell 1973) . These reactions have important implications i n terms of n u t r i -ent a v a i l a b i l i t y . For example, the reduction of f e r r i c (Fe-^+) iron and manganic (Mn^+) manganese to lower valency states increases the s o l u b i l i t y of these nutrients, since ions of the higher valency state generally exist as insoluble compounds i n s o i l (e.g. Fe^O^, MnOg). The reduction of s o i l n i t r a t e nitrogen has many important implications. Nitrate reduction may lead to the /zo l i b e r a t i o n of nitrogen gases to the atmosphere (Cooper and Smith 1963)» and a resultant decrease i n t o t a l available s o i l nitrogen. S o i l b a c t e r i a l populations are also regulated by-s o i l moisture. Both excessively wet and excessively dry conditions tend to i n h i b i t a c t i v i t y of many s o i l bacteria and hence i n h i b i t various nutrient transformations important i n terms of nutrient a v a i l a b i l i t y and plant n u t r i t i o n ( M i l l e r and Johnson 1964; Stanford and Epstein 19?4). The water films surrounding s o i l p a r t i c l e s i n dry s o i l s are very t h i n , r e s t r i c t i n g the movement of bacteria (Hamdi 1971)• Thin water films also r e s t r i c t the d i f f u s i o n of soluble nutrients to the b a c t e r i a l surface. Excess moisture prevents b a c t e r i a l growth by lowering the supply of oxygen necessary f o r aerobic b i o l o g i c a l processes. Although anaerobic bacteria may continue to carry out many important functions i n very wet s o i l (some of which have already been discussed), i t i s the aerobic bacteria which are largely involved i n the processes of mineralization, immobilization, and n i t r i f i c a t i o n . Very wet and very dry s o i l s are s i m i l a r l y p r o h i b i t i v e to the growth of s o i l fungi, a fact which plays an important i n d i r e c t role i n plant n u t r i t i o n . Within the rhizosphere of many plants, there generally exist p a r t i c u l a r specialized fungi capable of forming s p e c i f i c associations /21 with roots called "raycorrhizae" (Harley 1969) . Research has shown that the mycorrhizal association has a very favorable e f f e c t on the n u t r i t i o n of the host plant (Hatch 1937; M i t c h e l l et a l . 1937; Lamb and Richards 1971) . Hatch (1937) , i n his experiments with Pinus strobus, found that mycorrhizal roots absorbed 86, 75 . and 234 per cent more nitrogen, potassium, and phosphorus respectively than non-mycorrhizal roots. He proposed that the increased n u t r i t i o n a l response of mycorrhizal roots was due to 1) increased absorbing surface caused by greater diameter and branching of mycorrhizal roots, 2) greater longevity of mycorrhizal roots, and 3) extensive growth of fungal hyphae (which may also act as absorbing elements) into the s o i l . The greater s o i l nutrient exploitative potential exhibited by mycorrhizal roots may of f e r them an advantage i n competition with s o i l microbes and non-mycorrhizal species for s o i l nutrients (Ritter and Lyr 1965; Bowen 1973)* The a b i l i t y of mycorrhizae to u t i l i z e c ertain forms of organic nitrogen and phosphorus has been well documented (Lundeberg 1970) . Also, mycorrhizae have been shown to promote s o l u b i l i t y of inorganic nutrients (Voigt 1968) . Roots growing i n either very wet or very dry s o i l generally have few mycorrhizae (Worley and Hacskaylo 1959; Meyer 1973)- I n f a c t , there i s evidence to suggest that /Z2 most mycorrhizal-forming fungi are more affected by a lack of s o i l moisture than other s o i l fungi (Meyer 1973)* Therefore, t h e i r a b i l i t y to exploit the nutrient-supplying potential of a s o i l may be low when conditions are either very wet or very dry. 1.45 E f f e c t of S o i l Moisture on Nutrient Uptake and Tissue  Nutrient Concentration Some in t e r r e l a t i o n s h i p s between s o i l moisture, growth, and plant n u t r i t i o n can be shown by the ef f e c t of varying s o i l moisture on f o l i a r nutrients. While i t i s d i f f i c u l t to establish whether plant growth i s more closely controlled by nutrients or moisture, some f e e l i n g f o r the r e l a t i v e importance of each can be gained by studying tissue nutrient content and concentration. A decline in both nutrient uptake and f o l i a r nutrient concentration with decreased moisture supply i s an i n d i c a t i o n that s o i l moisture d e f i c i t i n h i b i t s nutrient a v a i l a b i l i t y and uptake more than growth, and inadequate n u t r i t i o n may be at least p a r t i a l l y responsible f o r any growth reduction associated with the moisture d e f i c i t . Hibbard and Nour (1958) observed concentrations of phos-phorus and potassium i n peach and apple leaves f a l l to c r i t i c a l l e v e l s under severe moisture stress, even though supplies of these nutrients i n the s o i l were abundant. On /23 the other hand, f a i r l y adequate f o l i a r concentrations were maintained with r e l a t i v e l y low s o i l nutrient supply so long as moisture was kept high. Conversely, f o l i a r nutrient concentrations have often been found to increase with decreased s o i l moisture supply, even though the actual nutrient uptake has remained unchanged or decreased (Walker 1962; Zinke 1962; Pharis and Kramer 1 9 6 4 ; Hosner e_t a l . 1 9 6 5 ; Hoyle 1 9 6 5 ; Barnes and Bengtson I 9 6 8 ; Heiner I 9 6 8 ; Broadfoot and Farmer 1 9 6 9 ; Schomaker 1 9 6 9 ; Waring and Youngberg 1 9 7 2 ; McClain and Armson 1 9 7 6 ) . This condition may be caused by continued absorption and translocation of nutrients even after growth and metabolism have been slowed as a res u l t of moisture d e f i c i t (Schomaker 1969). In instances such as these, growth i s presumably i n h i b i t e d more by a lack of s o i l moisture than by inadequate nutrient supply, since some studies have shown that under severe moisture stress f o l i a r nutrient concentrations have re f l e c t e d luxury consumption (Schomaker I969) . However, increases i n f o l i a r nutrient concentration w i l l not necessarily be s u f f i c i e n t to com-1. p l e t e l y r e l i e v e a severe nutrient deficiency. Obviously, f o l i a r nutrient concentrations w i l l be correlated rather poorly with growth under conditions of moisture stress. To what extent growth i s limited by low nutrient a v a i l a b i l i t y during periods of moisture stress i s not well /2k understood, since the demand for nutrients w i l l also change (Brix 1980). It i s conceivable that demand i s reduced more than the a v a i l a b i l i t y , thus improving the mineral status of the plant (Viets 1972). There i s no simple rule governing the effect of decreased moisture supply on f o l i a r nutrient concentration. Bengtson and Voigt (1962) showed the re l a t i o n s h i p between moisture supply and f o l i a r nutrient concentration to vary according to the a v a i l a b i l i t y or s o l u b i l i t y of the nutrient i n question. When the nutrient was i n highly soluble form, f o l i a r concentration increased with decreased moisture supply. Many workers have shown f o l i a r nutrient concentra-tions to be decreased with increased moisture supply, even though t o t a l uptake may increase (Steenbjerg 1951; Schomaker 1969; Leaf et a l . 1970; McClain and Armson 1976; Timmer and Stone 1978). This i s one example of what i s termed a 'd i l u t i o n e f f e c t ' , since the f o l i a r nutrient concentration has been diluted by the additional growth r e s u l t i n g from increased moisture. Under these circumstances, growth p r i o r to the supply of additional moisture was undoubtedly most limited by lack of s o i l moisture. As the d i l u t i o n progresses, however, the f o l i a r concentration of a p a r t i c u l a r nutrient may become so low that i t may i n turn l i m i t growth. In t h i s regard, the a l l e v i a t i o n of one growth l i m i t i n g factor (e.g. moisture) may i n fact induce a nutrient deficiency not pre-viously evident. / 2 5 Schomaker ( I969 ) , i n a greenhouse study with white pine seedlings, demonstrated highly s i g n i f i c a n t i n t e r a c t i o n between i r r i g a t i o n and nutrient treatments i n the cases of f o l i a r N,K, and Mn concentrations. He concluded that under certain nutrient regimes, a c r i t i c a l examination of s o i l moisture conditions may be necessary before interpreting r e s u l t s of f o l i a r analysis. He f e l t further research i n t h i s area would possibly r e s u l t i n i d e n t i f i c a t i o n of di f f e r e n t c r i t i c a l ranges of f o l i a r nutrient concentration for various s o i l moisture regimes. In t h i s way, misinterpretation of f o l i a r analysis r e s u l t s could be largely avoided (Ulrich 1952). In t h e i r study of the influence of f e r t i l i z a t i o n on European l a r c h at d i f f e r e n t l e v e l s of water supply., F i e d l e r and Czerney (1973) found that, i f moisture supply was ad-equate, the optimum f o l i a r N concentration was 1.5%. Under conditions of moisture stress,-the optimum N concentration was 2 . 6 - 3 . 4 ^ . From the above discussion, i t i s evident that f o l -iage samples taken from plants which have been under moisture stress may r e f l e c t the moisture conditions as well as the nutrient-supplying power of the s o i l . Therefore, changes in s o i l moisture, e s p e c i a l l y from one growing season to the next, may seriously a l t e r growth-nutrient relationships (Schomaker I969; Armson 1973)* However, when moisture conditions are sim i l a r , the rel a t i o n s h i p may be much improved. I f s o i l /26 moisture could be taken into account the diagnostic useful-ness of f o l i a r analysis would probably be greatly increased (van den Driessche 1974) . / 2 7 CHAPTER 2 METHODS AND MATERIALS 2.1 Experimental Design This study was designed as a complete f a c t o r i a l experiment with the two factors, s o i l nutrients (N) and s o i l moisture (M), each assigned four l e v e l s ( i . e . 4 x 4 complete f a c t o r i a l ) . The sixteen treatment combinations were r e p l i c a t e d three times, a t o t a l of 48 experimental units. Each unit was represented by one pot. The treatments were arranged i n a. randomized complete block design on the greenhouse bench. /28 2.2 Experimental Preparations 2.21 S o i l Preparation Preliminary chemical analyses were undertaken on s o i l samples collected from several locations throughout the U.B.C. Research Forest at Haney, B.C. A l l samples were collected from exposed road cuts, and therefore did not represent s p e c i f i c horizons but rather composites of several mineral s o i l horizons. The selected s o i l was characterized by i t s sandy loam texture, low f e r t i l i t y , moderately low CEC (cation exchange capacity), and low base saturation. Mineral s o i l s i n the immediate v i c i n i t y of the selected road cut have been c l a s s i f i e d as Humo-Ferric Podzols (Canada S o i l Survey Committee 1978) , derived from g l a c i a l t i l l of predominantly igneous i n t r u s i v e o r i g i n . The s o i l was sieved to 5 mm i n the f i e l d , thoroughly mixed i n a large box, and a i r - d r i e d . Further chemical analyses were undertaken on the <2 mm f r a c t i o n (Appendix 1 ) . P a r t i c l e size analysis and s o i l moisture determination were undertaken and a s o i l water retention curve was obtained (Appendix 2 ) . Each of 48 s i x - l i t r e p l a s t i c pots was packed with 5800 g pf air-dry, <5 mm s o i l to a bulk density of approximately 1300 kg/rn^. /29 2.22 S o i l N u t r i e n t s The s o i l u s e d i n t h i s s t u d y was s e l e c t e d s p e c i f i c a l l y f o r i t s l o w n u t r i e n t s t a t u s . ' A v a i l a b l e ; 1 s o i l n u t r i e n t c o n c e n t r a t i o n s were f o u n d t o be so l o w t h a t s e e d l i n g g r o w t h was l i k e l y t o be s e v e r e l y l i m i t e d . H o w e v e r , w i t h t h e p o s s i b l e e x c e p t i o n o f n i t r o g e n r e l a t i o n s h i p s , i t was assumed t h e r a t i o s o f t h e v a r i o u s n u t r i e n t e l e m e n t s were n o t s e r i o u s l y o u t o f b a l a n c e . F o r e s t f e r t i l i z a t i o n t r i a l s on s o i l s o f t h e g l a c i a t e d r e g i o n g e n e r a l l y s u p p o r t s u c h an i n f e r e n c e ( G e s s e l e t a l . 1965; R e g i o n a l F o r e s t N u t r i t i o n P r o j e c t 1976) . The u n f e r t i l i z e d s o i l r e p r e s e n t e d t h e l o w e s t n u t r i e n t t r e a t m e n t l e v e l . N u t r i e n t s o l u t i o n s o f t h r e e p r o g r e s s i v e l y h i g h e r c o n c e n t r a t i o n s were added t o t h e u n -f e r t i l i z e d s o i l t o a t t a i n t h e h i g h e r n u t r i e n t t r e a t m e n t l e v e l s . E a c h o f t h e n u t r i e n t s o l u t i o n s c o n t a i n e d d i f f e r e n t a b s o l u t e amounts o f t h e p a r t i c u l a r n u t r i e n t e l e m e n t s . H o w e v e r , w i t h t h e e x c e p t i o n o f n i t r o g e n and p h o s p h o r u s , n u t r i e n t r a t i o s were m a i n t a i n e d a t t h e v a l u e s p r e s e n t i n t h e u n f e r t i l i z e d s o i l , t h e r e b y a l l o w i n g f e r t i l i t y t o be a d j u s t e d u pward w i t h o u t d i s r u p t i n g n u t r i e n t b a l a n c e s . No m i c r o n u t r i e n t a d d i t i o n s were made. S i n c e 'optimum' s o i l n u t r i e n t l e v e l s have n o t b e e n d e t e r m i n e d f o r most t r e e s p e c i e s , none o f t h e n u t r i e n t t r e a t m e n t s a t t e m p t e d t o a p p r o x i m a t e an 'optimum' l e v e l . /30 The f o u r n u t r i e n t r e g i m e s ( d e s i g n a t e d I N , 2N, e t a r e shown i n T a b l e 1. A f t e r a d d i t i o n o f n u t r i e n t s i n d i l u t e s o l u t i o n , s o i l was t h o r o u g h l y m i x e d t o e n s u r e u n i f o r m d i s t r i b u t i o n . A l l n u t r i e n t s were a d d e d p r i o r t o t h e s t a r t o f t h e e x p e r i m e n t , w i t h no f u r t h e r a d d i t i o n s a s t h e e x p e r i m e n t p r o g r e s s e d , C o m p o s i t i o n o f t h e n u t r i e n t s o l u t i o n s i s shown i n A p p e n d i x 3- N i t r o g e n was a d d e d p r e d o m i n a n t l y as ammonium s u l p h a t e . The r e a s o n s f o r t h i s were t w o f o l d . F i r s t l y , t h e a d d i t i o n o f s u l p h u r w o u l d h e l p t o m a i n t a i n t h N/S r a t i o , shown b y some w o r k e r s ( D i j k s h o o r n and v a n W i j k 1967; K e l l y and L a m b e r t 1972; T u r n e r e t a l . 1977) t o be c r i t i c a l i n p l a n t n u t r i t i o n . S e c o n d l y , most r e s e a r c h s u g g e s t s D o u g l a s - f i r a t t a i n s i t s b e s t g r o w t h when t h e m a j o r i t y o f n i t r o g e n i s s u p p l i e d a s a.mmonium-N ( v a n d e n D r i e s s c h e 1971; v a n d e n D r i e s s c h e and D a n g e r f i e l d 1975)• 2.23 S o i l M o i s t u r e R e g u l a t i o n F o u r s o i l m o i s t u r e r e g i m e s a s e x p r e s s e d b y s p e c i f i c r a n g e s o f s o i l w a t e r p o t e n t i a l were m a i n t a i n e d t h r o u g h o u t t h e c o u r s e o f t h e e x p e r i m e n t . These r e g i m e s ( d e s i g n a t e d 1M, 2M, e t c . ) w e re a s f o l l o w s : 1M -1500 J ' k g - 1 t o -2000 J ' k g - 1 (-1.5 t o - 2 . 0 MPa.) 2M -300 J ' k g - 1 t o -600 J ' k g - 1 ( - 0 . 3 t o - 0 . 6 MPa.) 3M -30 J - k g - 1 t o -50 J ' k g " 1 ( - 0 . 0 3 t o - 0 . 0 5 MPa.) /3 l TABLE 1. Amount o f n u t r i e n t added r e l a t i v e t o ' a v a i l a b l e ' (N,P) o r e x c h a n g e a b l e (Ca,Mg) amount i n i t i a l l y p r e s e n t i n t h e s o i l NUTRIENT TREATMENT LEVEL l N a 2N 3N 4 N 0(1) 30 (2.25) 50 (3) 85 (4. P C 0 2 3 5 K 0 0.5 1 2 C a 0 0.5 l 2 Mg 0 0.5 1 2 a F o r a b s o l u t e m a g n i t u d e s o f o r i g i n a l l e v e l s i n s o i l , see A p p e n d i x 1. b A p r e l i m i n a r y e x p e r i m e n t showed o n l y k% o f added n i t r o g e n was r e c o v e r e d as a v a i l a b l e N two weeks a f t e r a d d i t i o n . L o s s e s were a t t r i b u t e d t o d e n i t r i f i c a t i o n a n d / o r i m m o b i l i z a t i o n . T h i s l o s s f a c t o r was a p p l i e d when e s t i m a t i n g t h e a c t u a l i n c r e a s e i n a v a i l a b i l i t y as n u t r i e n t l e v e l was i n c r e a s e d . E s t i m a t e d r e l a t i v e a v a i l a b l e l e v e l s a f t e r t r e a t m e n t a r e shown i n p a r e n t h e s e s . c A p r e l i m i n a r y e x p e r i m e n t showed 0% o f added P was r e c o v e r e d as a v a i l a b l e P two weeks a f t e r a d d i t i o n . P o o r r e c o v e r y was a t t r i b u t e d t o f i x a t i o n b y Fe and A l . T h e r e f o r e , t h e P a d d i t i o n s shown f o r t h e h i g h e r n u t r i e n t t r e a t m e n t s p r o b a b l y do n o t a c t u a l l y r e p r e s e n t h i g h e r s o i l P a v a i l a b i l i t y . /32 km -3 J ' k g - 1 t o -5 J ' k g 1 (-0.003 t o -0.005 MPa.) C a l c u l a t i o n s s u g g e s t e d t h a t t h e w e t t e s t t r e a t m e n t (km) m i g h t h a v e b e e n t o p w e t for.maximum r o o t r e s p i r a t i o n . T o t a l s o i l p o r o s i t y i s r e p r e s e n t e d b y l - ( B u l k D e n s i t y / P a r t i c l e D e n s i t y ) . W i t h t h e s o i l i n t h e t r e a t m e n t p o t s p a c k e d t o a b u l k d e n s i t y o f 1300 kg/m^ and assumed p a r t i c l e d e n s i t y o f 2600 kg/m^, t o t a l s o i l p o r o s i t y w o u l d be a p p r o x i m a t e l y 50%. The s o i l w a t e r r e t e n t i o n c u r v e showed s o i l w a t e r c o n t e n t t o be 39f° b y v o l u m e a t a s o i l w a t e r p o t e n t i a l o f -5 k P a , r e s u l t i n g i n a n a i r - f i l l e d p o r o s i t y o f o n l y 11%. The m o i s t t r e a t m e n t ( 3 M ) p r o b a b l y o f f e r e d n e a r o ptimum m o i s t u r e c o n d i t i o n s f o r s e e d l i n g g r o w t h a.nd n u t r i e n t u p t a l c e . J a r v i s and J a r v i s (1963) f o u n d t h a t y o u n g P i n u s  s y l v e s t r i s and P i c e a . a b i e s s e e d l i n g s a t t a i n e d maximum g r o w t h i n s o i l s a l l o w e d t o d r y t o -0.05 MPa b e f o r e w e t t i n g . K r a j i n a . (1969) r e p o r t e d t h a t D o u g l a s - f i r a t t a i n e d maximum g r o w t h u n d e r m o i s t t o m o d e r a t e l y w et m o i s t u r e r e g i m e s . The d r y t r e a t m e n t (2M) a p p r o x i m a t e d a l e v e l o f s o i l m o i s t u r e w h e r e s e e d l i n g g r o w t h w o u l d be e x p e c t e d t o be c o n s i d e r a b l y r e d u c e d . S a n ds a n d R u t t e r (1959) r e p o r t e d t h a t p r o d u c t i o n o f s h o o t s i n y o u n g P i n u s s y l v e s t r i s s e e d l i n g s was r e d u c e d more t h a n 50% i n s o i l a l l o w e d t o d r y t o -0.15 MPa. J a r v i s a n d J a r v i s (1963) r e p o r t e d a. d e c r e a s e i n c o n i f e r s e e d l i n g b i o m a s s o f a b o u t 1/3 i n s o i l d r i e d t o -0.17 MPa. S t r a n s k y and W i l s o n (1964) f o u n d a. /33 s o i l w a t e r p o t e n t i a l o f -O.35 MPa s t o p p e d s h o o t e l o n g a t i o n i n P i n u s t a e d a and P i n u s e c h i n a t a . A l t h o u g h t r a n s p i r a t i o n a l and s t o m a t a l r e s p o n s e o f c o n i f e r s t o s o i l m o i s t u r e d e f i c i t s h a s b e e n shown t o v a r y w i t h s p e c i e s , t h e r a n g e o f m a t r i c p o t e n t i a l c h o s e n f o r t h e v e r y d r y t r e a t m e n t (1M) was e x p e c t e d t o e n s u r e a v e r y l a r g e r e d u c t i o n i n s e e d l i n g g r o w t h , "based on d a t a o f L o p u s h i n s k y and K l o c k (1974). The r e l a t i o n s h i p "between s o i l w a t e r p o t e n t i a l and s o i l w a t e r c o n t e n t was d e t e r m i n e d "by t h e u s e o f p r e s s u r e p l a t e a p p a r a t u s and s u b s e q u e n t p l o t t i n g o f a s o i l m o i s t u r e r e t e n t i o n c u r v e ( A p p e n d i x 2). S o i l w a t e r c o n t e n t s a t -0.01, -0.03, -0.10, and -1.5 MPa were d e t e r m i n e d u s i n g l o w and h i g h p r e s s u r e c e r a m i c p l a t e e x t r a c t o r s . U s e d i n c o n j u n c t i o n w i t h p o t w e i g h t , t h e s o i l m o i s t u r e r e t e n t i o n c u r v e e n a b l e d g r a v i m e t r i c r e g u l a t i o n o f s o i l w a t e r p o t e n t i a l . When w a t e r p o t e n t i a l ( a s r e f l e c t e d b y p o t w e i g h t ) r e a c h e d t h e s p e c i f i e d minimum l e v e l f o r a p a r t i c u l a r t r e a t m e n t , d i s t i l l e d w a t e r was added t o t h e s o i l s u r f a c e i n an amount s u f f i c i e n t t o r a i s e t h e w a t e r p o t e n t i a l t o t h e s p e c i f i e d maximum l e v e l . W e i g h i n g was u n d e r t a k e n on a h e a v y - d u t y s o l u t i o n b a l a n c e (ir 1 g) . I n o r d e r t o a c t as a c h e c k on t h e g r a v i m e t r i c m e t h o d , and t o a l l o w a d j u s t m e n t f o r g a i n s i n s e e d l i n g w e i g h t ( a n d p o t w e i g h t ) d u r i n g t h e c o u r s e o f t h e . e x p e r i m e n t , a l l t r e a t m e n t pots wi th in one of the r e p l i c a t i o n s were equipped to monitor s o i l water p o t e n t i a l d i r e c t l y . S o i l dewpoint hygrometers and tensiometers were used to monitor s o i l water p o t e n t i a l i n the two dr ie s t and two wettest moisture regimes, r e spec t ive ly . One of e i ther a tensiometer or hygrometer was i n s t a l l e d v e r t i c a l l y at a depth of 8 cm, selected to represent the average root ing depth of seedlings over time. S o i l dewpoint hygrometers (PT-51> Wescor Inc.) were used i n conjunction with a dewpoint microvoltmeter (HT-33» Wescor I n c . ) . Voltage output of the microvoltmeter i s l i n e a r l y re la ted to s o i l water p o t e n t i a l over a wide range of water p o t e n t i a l . The instrument may be used i n e i ther the dewpoint or psychrometric mode of operat ion. Due to a smaller change i n s e n s i t i v i t y with temperature change, and higher s e n s i t i v i t y at high s o i l moisture p o t e n t i a l (Nnyamah and Black 1977)» a l l measurements i n t h i s experiment were made i n the dewpoint mode of operat ion. C a l i b r a t i o n was affected by immersion of hygrometers i n d i s t i l l e d water and solut ions of 0.2 and 0.5 mol NaCl/kg water representing osmotic potent ia l s of -0.91 and -2.28 MPa, r e s p e c t i v e l y , at 25°C (Lang 1967). Hygrometers were immersed i n a p l a s t i c bot t le containing the c a l i b r a t i o n so lu t ion which was i n turn immersed i n a constant temperature water bath ( i0.02 °C) . C a l i b r a t i o n measurements were taken at 15°C and 25°C. For each hygrometer, a ser ies /35 of four measurements was made i n each solution and temperature combination. Following removal from each NaCl solution, the ceramic cups were thoroughly rinsed i n d i s t i l l e d water and a i r dried before immersion i n the next solution. Average microvolt output readings were calculated to determine the c a l i b r a t i o n slope f o r each hygrometer. Readings with d i s t i l l e d water were used to determine c a l i b r a t i o n intercept values. A t y p i c a l c a l i b r a t i o n curve (at 15°C and 25°C) i s shown i n Figure 2. Only those sensors that had slopes between 5«5 and _ i 7.5 MV-MPa , and with, less than 0.25 «*w v a r i a t i o n i n output for the four measurements i n the 0.5 molal NaCl solution were selected for use i n the experiment (Appendix 4). This v a r i a t i o n represented approximately 0.03 MPa at a water pote n t i a l of -2.28 MPa. Hygrometer i n s t a l l a t i o n was effected by wetting up the s o i l and making a 0.3-cm hole near the centre of the pot. The hygrometer cup was then forced into the hole and lead wires taped to the side of the pot to prevent movement of the cup. The s o i l was then wetted up again to ensure good contact between the s o i l and the cup. Wiebe e_t a l . (1979) suggested that, i n comparison with h o r i z o n t a l l y i n s t a l l e d hygrometers, v e r t i c a l l y i n s t a l l e d ones are more susceptible to errors associated with temperature gradients within the s o i l and heat conduction VO 25°C FIGURE 2. C a l i b r a t i o n curve showing re l a t ion-ship between microvoltmeter output (-«V) and osmotic p o t e n t i a l (Bars) .3-15°C Q> -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 Bars /37 through hygrometer lead wires . Microvoltmeter readings were therefore taken ear ly every morning i n order to minimize these e r ror s . Tensiometers were constructed using 0.6-cm (outside diameter) ceramic cups fabr icated from 1-bar porous ceramic mater i a l . They were i n s t a l l e d i n the same fashion as hygrometers. Tensiometers were connected to a mercury re servo i r by lengths of t h i n nylon tubing. The tubing was attached to a v e r t i c a l p lex ig la s s manometer scale which enabled easy measurement of the height of mercury r i s e i n the tubing i n response to changes i n s o i l water p o t e n t i a l . Height measurements of the mercury columns were taken d a i l y and converted to s o i l water p o t e n t i a l u n i t s . Di rec t measurement of s o i l water p o t e n t i a l allowed comparisons to be made with the gravimetric method of regula t ing s o i l water p o t e n t i a l . Comparisons showed that the gravimetric method cons i s tent ly underestimated s o i l water p o t e n t i a l i n the wet (4M), dry (2M) , and very dry (1M) treatments ( i . e . the s o i l was wetter than gravimetric ca l cu la t ions suggested). No adjustments were made i n the wet treatment ( i . e . s o i l moisture was maintained i n the wetter condi t ion) . However, gravimetric weighing spec i f i c a t ions for the 1M and 2M treatments were adjusted accordingly ( i . e . the pots were allowed to dry to a lower weight before rewatering ). In t h i s respect , instrumentation allowed for the ' f i n e - t u n i n g ' /38 of the gravimetric method. However, instrumentation did not take into consideration s o i l moisture gradients within the pots. Due to l i m i t a t i o n s imposed by unsaturated flow i n s o i l , i t i s extremely d i f f i c u l t to maintain a constant moisture value i n dry s o i l and even more d i f f i c u l t to express an average value that has a simple r e l a t i o n s h i p to plant growth. In order to get water to move downward reasonably quickly through a dry s o i l , the moisture content of the wetting front must be raised to f i e l d capacity, or above. Otherwise, the unsaturated conductivity w i l l be so low as to prevent any appreciable wetting at depth. Therefore, when a minimum amount of water i s added to the surface of a pot containing dry s o i l , the downward movement of the wetting front w i l l be r e s t r i c t e d , the boundary between the wet and dry s o i l being f a i r l y sharp. Moreover, the downward movement of the wetting front w i l l be l e s s , and the boundary between wet and dry s o i l sharper, i n coarse-textured s o i l s than in fine-textured s o i l s . Therefore, while the average moisture content of the pot may be maintained at or near a constant value, t h i s value may seriously underestimate the moisture content above the wetting front boundary, and seriously overestimate the moisture content of the s o i l below the boundary. The p r a c t i c a l significance of these errors w i l l depend upon the root d i s t r i b u t i o n within the s o i l . In order to best r e f l e c t the 'average' moisture / 3 9 condi t ion for the dry moisture treatments, an equi l ibr ium period fo l lowing watering was required to allow for the downward movement of the wetting f ront . E q u i l i b r a t i o n i n conjunction with the downward adjustment of gravimetric ca lcu la t ions enabled regula t ion of s o i l moisture i n the 1M and 2M moisture treatments to be improved. In order to prevent puddling of the surface s o i l as a r e su l t of watering, to reduce evaporation from the s o i l surface, and to help minimize water p o t e n t i a l gradients within the s o i l , a t h i n l ayer of polyethylene chips was spread over the s o i l surface of every pot. P l a s t i c trays were pos i t ioned beneath pots of the wettest moisture treatment (4M) to c o l l e c t leachate. Drainage water was added back to the s o i l during watering. 2.2k Seedling Germination Low e levat ion Douglas- f i r seed from the Chi l l iwack Forest (seedlot no. 1275) was obtained from the B.C. M i n i s t r y of Forests nursery at Duncan, B.C. The nutr ient requirements of t h i s species have been ref ined to a greater extent than other B.C. con i fe r s , which makes i t we l l suited to a study of t h i s type. The seed was s t r a t i f i e d for 5 weeks at 2°C, then sown 0.3 cm below the surface i n germination f l a t s containing medium s i l i c a sand. Germination was estimated to be greater A o than 95%' Two weeks after germination, 22 germinants were transplanted into each treatment pot. Following a one-month establishment period (Dec. - Jan.), during which time s o i l moisture was maintained at or near f i e l d capacity, seedlings were thinned^to 15/p°t and moisture treatments begun. 2 . 3 Experimental Environment Experimental objectives required that seedlings be grown under c a r e f u l l y controlled conditions of s o i l f e r t i l i t y and s o i l moisture. Also, time constraints required temperature and l i g h t conditions to be favorable for rapid-and continuous growth of the seedlings. For these reasons, i t was necessary that the study take the form of a greenhouse pot experiment. The greenhouse environment allowed environmental conditions to be held constant, thereby enabling any treatment e f f e c t s to be attributed s o l e l y to nutrients and/oF moisture. While re s u l t s obtained from greenhouse pot experiments may not be d i r e c t l y applicable to trees growing under f i e l d conditions, the s p e c i f i c roles that moisture and nutrients play i n growth, nutrient uptake and tissue nutrient concentrations could best be examined under the conditions afforded by the greenhouse environment. When natural daylight i s i n short supply, long-day e f f e c t s can be obtained by supplementing natural l i g h t with low i n t e n s i t y a r t i f i c i a l l i g h t (Downs' 1 9 6 2 ) . Long day-lengths provided by supplemental l i g h t keep the phytochrome (light-absorbing) l e a f pigments predominantly i n the active, far-red absorbing form, thereby avoiding dormancy. A 2 A 16-hour daylight period was maintained i n the greenhouse by the use of supplemental white fluorescent l i g h t i n g . Incandescent supplemental l i g h t i s known to be more ef f e c t i v e i n promoting growth of woody plants than fluorescent l i g h t , due to the di f f e r e n t amounts of red and far-red radiant energy emitted by the two l i g h t sources. A predominance of red (from fluorescent lamps) i n h i b i t s internode elongation. However, incandescent supplemental l i g h t radiates a great deal of heat which may i n fact be detrimental to seedling growth. Fluorescent l i g h t s can be suspended a short distance above plants, thereby providing greater i n t e n s i t y of radiant energy without the associated disadvantage of heat. It was assumed that normal daylight would provide s u f f i c i e n t far-red radiant energy to meet growth requirements. Mean greenhouse temperature was approximately 20°C. Night-time temperatures were as low as 16°C and day-time temperatures were as high as 27°C. S o i l temperature varied between 20°C and 25°C. A 3 2.4 Seedling-Harvest Moisture and nutrient treatments were maintained fo r f i v e months (Jan. - May), during which time v i s u a l observations of the vigor and health of seedlings of the various treatments were made. Immediately before harvest, a detailed f o l i a r damage assessment survey was undertaken f o r each treatment combination. Five l e v e l s of f o l i a r damage were defined as follows: 1) None - 0 - 5% of seedlings show some f o l i a r damage (<l/2 of foliage of each damaged seedling affected) 2) L i t t l e - 6 - 20% of seedlings show f o l i a r damage (>l/2 of foliage of each damaged seedling affected) 6 - 40% of seedlings show f o l i a r damage ( <-l/2 of foliage of each damaged seedling affected) 3) Moderate - 21 - 50% of seedlings show f o l i a r damage (>l/2 of foliage of each damaged seedling affected) 41 - 90% of seedlings show f o l i a r damage (<l/2 of fol i a g e of each damaged seedling affected) 4) Heavy - 51 - 80% of seedlings show f o l i a r damage I (>l/2 of foliage of each damaged seedling affected) 90%+ of seedlings show f o l i a r damage (<?l/2 of foliage of each damaged seedling affected) 5) Severe - 81$ of seedlings show f o l i a r damage ( > l / 2 of foliage of each damaged seedling affected) At the conclusion of the treatment period, the pots were emptied and the seedlings c a r e f u l l y extracted from the s o i l . T o t a l shoot height, amount of shoot growth during the treatment period, root length, and stem diameter measurements were made on every seedling i n a l l treatment units. Height and length measurements were made with a centimetre r u l e , and diameter measurements made with a micrometer. Visual observations of mycorrhizal development i n the various treatment combinations were recorded. Tops were separated from roots and both were rinsed i n d i s t i l l e d water to remove dust and s o i l p a r t i c l e s . Tops and roots from each pot were then placed i n envelopes and dried at 65°C f o r 36 hours. Following drying, foliage was removed from stems, and f o l i a g e , stems and roots weighed separately. Foliage, stems, and roots were ground to a fine powder i n an agate mortar and stored i n la b e l l e d v i a l s f o r subsequent tissue analysis. A 5 2 . 5 S o i l Analysis • At the completion of the experiment, the s o i l from each pot was rapidly a i r - d r i e d by spreading i t t h i n l y on brown paper on the greenhouse bench. After mixing, sub-samples were taken, sieved to 2mm and stored for subsequent s o i l analyses. P a r t i c l e size d i s t r i b u t i o n was done by the hydrometer method (Day 1 9 6 5 ) . E l e c t r i c a l conductivity was undertaken on the extract from a saturated s o i l paste (Jackson 1 9 5 8 ) using a Radiometer conductivity meter Type CDM 2 e . S o i l pH measurements were made i n a 1 : 2 soil:water suspension with a Porto-matic 1 7 5 pH meter. Exchangeable Ca, Mg, and K were extracted with 1 . 0 N NaCl and determined on a Perkin-Elmer atomic absorption spectrophotometer. Soluble ('available') phosphorus was extracted with. 0 . 5 M sodium bicarbonate (NaHCO^), and determined on a Turner spectrophotometer with the molybdenum blue colorimetric method, using ascorbic acid as the reducing agent (Olsen and Dean 1 9 6 5 ; Watanabe and Olsen 1 9 6 5 ) • Ammonium and n i t r a t e nitrogen were extracted with 1% KgSOij, (Makarov and Gerashchenko 1 9 7 6 ) . Ammonium-N was determined by the colorimetric phenol-hypochlorite method of Weatherburn ( 1 9 6 7 ) . Nitrate-N was determined by the chromotropic acid method (West and Ramachandran 1 9 6 6 ) . A 6 2.6 Seedling Tissue Analysis 2.61 Preparation The grinding and storage of seedling tissue was discussed previously (section 2 . 4 ) . Immediately p r i o r to tissue digestion, v i a l s were emptied into shallow aluminum trays and contents re-dried at 65°C for 3 hours. Upon removal from the oven, the tissue was immediately weighed and added to Kjeldahl digestion tubes. Each digestion rack (20 tubes) contained one duplicate sample and one blank. 2.62 Tissue Digestion T r a d i t i o n a l l y , plant tissue analyses require two or more separate digestions. Conventional methods of P, K, Ca, and Mg analysis employ wet- or dry-ashing techniques. Nitrogen determination requires a second digest, generally using a Kjeldahl procedure (Jackson 1958) ' It i s often suggested that phosphorus be dry-ashed i n the presence of magnesium acetate ('MgOAc'), which would require a t h i r d digest (Jackson 1958) . In addition to being slow and tedious, these methods also require r e l a t i v e l y large amounts of plant t i s s u e . In t h i s experiment, the weights of the separate seedling components ( i . e . f o l i a g e , stems, roots) were low, A ? even though the seedlings grown i n each pot were composited for ana lys i s . Therefore, i t was necessary to select a d iges t ion method that would enable the analys i s of several elements from a s ingle d igest . Wet d iges t ion of plant mater ia l with a sulphuric , acid - hydrogen peroxide ( H 2 S O / J / H 2 O 2 ) oxidative mixture (hereafter referred to as Caro's acid) has been shown by many workers to be a rapid and thorough method of mult ip le element determination i n a s ingle d igest . The method was f i r s t used by Koch and McMeekin (1924) and by Lindner and Harley (1942) for the analys is of n i t rogen . It was l a t e r used by Lindner (1944) for the simultaneous determination of N, P, K, Ca, and Mg i n hardwood f o l i a g e . Caro 's acid d iges t ion of coniferous t i s sue was probably f i r s t undertaken by Heilman (1961) . Recently, several modif icat ions of the Caro's acid procedure have been proposed i n the l i t e r a t u r e . Most of these involve the use of a cata lys t with or without the addi t ion of s a l t s to ra i se the b o i l i n g point of the ac id . However, Ba l l a rd (1980a) used a Caro's acid method with no addi t ives to digest coni fer f o l i a g e , and obtained very favorable r e su l t s r e l a t i v e tq_pther conventional methods of , d i ge s t ion . He found the recovery of ni trogen with Caro 's acid ranged from 97 - 101$ of that recovered by the conventional K je ldah l method. He also compared h i s method with conventional /48 dry-ashing procedures generally used to determine K, Mg, and P i n plant t i s s u e . Potassium and magnesium recovery was 26% and 2k%> higher, respectively, with the Caro's acid digestion than with dry-ashing. Recovery of P with the Caro acid method ranged from 9^% - 10k% of that recovered with dry-ashing i n the presence of MgOAc. Precision of the Caro' acid method was generally greater than that obtained from other methods. Similar H2S0i4.-H"202 digestion procedures have given comparable or improved recoveries of N, P, K, Ca, and Mg over those obtained with other conventional plant digestion procedures (Thomas et a l . 1 9 6 7 ; Parkinson and A l l e n 1 9 7 5 ; van Lierop 1 9 7 6 ) . van Lierop's data include r e s u l t s f o r a U.S. NBS orchard l e a f standard sample of 'known' composition. Associated with the advantage of the single Caro's acid digest i s the small tissue sample size required. Ballard (1980a) reported that excellent recoveries of N, P, K, Ca, and Mg could be obtained with a 0.200 g foliage sample. The digestion method tested by Ballard (1980a) was used to digest f o l i a g e , stems, and roots i n t h i s study. The-procedure used was as follows: 1) Weigh 0.200 g of tissue into a 2 5 0 ml Kjeldahl digestion tube. A 9 2) Add 15 ml cone. h^SO^, and mix on vortex. 3) Place sample rack containing tubes i n block digestor u n t i l dense SOg fumes are given o f f over top of the tubes (approx. 2 minutes). Remove rack and cool f o r 5 minutes. 4) Using a modified Oxford dispensor, c a r e f u l l y drip a t o t a l of 6 ml of 3°$ ^2^2 ^ o w n side of the tube i n 2:aml increments. Careful l y shake each tube by hand after each addition. 5) Place the sample rack i n the block digestor (preheated to 420°C) for 45 minutes. 6) Remove rack from block and cool f o r 10 minutes. Add 0.5 ml H 202 to those tubes which are not clear and c o l o r l e s s , shake by hand and replace entire rack i n block f o r 5 minutes. 7) Remove rack from block and allow to cool f o r 20 minutes. Add 40 ml d i s t i l l e d H2O (carefully) and place the rack i n a cold water bath i n sink. Mix each tube on vortex. Transfer quantitatively ( r i n s i n g at least 3 times) from digestion tubes to 100 ml volumetric f l a s k s . Make to volume after allowing s u f f i c i e n t time to cool. Pour into 125 ml p l a s t i c bottles and store f o r subsequent analysis. 2.63 Analysis T o t a l nitrogen, phosphorus, potassium, calcium, magnesium and manganese analyses were performed on the Caro's /50 acid d igest . Coloriraetric determination of ni trogen was done on a Technicon Auto Analyzer II (Technicon Corp. Inc. ) using an adaptation of the method described by Weatherburn (1967). Phosphorus was determined using a co lor imetr ic procedure s i m i l a r to that developed by John (1970). Thi s method i s based on the reduction of the ammonium molybdophosphate complex to a blue color which i s read on a spectrophotometer. The a c i d i t y of the reagent was reduced i n order to compensate for the highly a c i d i c nature of the Caro's acid d igest . Potassium, calcium, and magnesium were determined by atomic absorption spectrophotometry. An a ir-acetylene flame was found to be s u f f i c i e n t for fo l iage and stem analys i s ; however, a n i t rous oxide flame was necessary-./for Ca and Mg analys i s of root t i s sue to suppress s i l i c o n and/or aluminum inter ference . Manganese was also determined by atomic absorption spectrophotometry. However, concentration i n the Caro 's acid digest approached the instrument's s e n s i t i v i t y l i m i t for t h i s element. Quantitative analys is of i r o n , manganese, and other micronutrients requires a l arger sample s ize and further modif icat ions to the Caro 's acid procedure. / 5 l 2.7 S t a t i s t i c a l Analysis A l l variables were subjected to a two-way analysis of variance to test for significance of the main effects of nutrients and moisture, and to detect s i g n i f i c a n t nutrient x moisture interactions. I f F values were s i g n i f i c a n t at the 5% l e v e l , Duncan's Multiple Range Test was undertaken to f i n d out which main factor treatment means were d i f f e r e n t from each other. One-way analysis of variance and Duncan's Multiple Range Test were undertaken separately f o r each nutrient and moisture l e v e l to test f o r differences between i n d i v i d u a l treatment means and to study the nature of any s i g n i f i c a n t nutrient x moisture main e f f e c t interactions,. A l l variables were included i n a c o r r e l a t i o n matrix to text f o r correlations between certain growth and nutrient parameters. In an attempt to improve correlations, the data were also s t r a t i f i e d by moisture l e v e l . U.B.C. computing f a c i l i t i e s were used fo r a l l data analysis. The MFAV computer package was used for analysis of variance and Duncan's Multiple Range Tests. Correlation c o e f f i c i e n t s were computed with the Michigan Interactive Data Analysis System (MIDAS). /52 CHAPTER 3 RESULTS AND DISCUSSION: EFFECTS OF NUTRIENT AND MOISTURE REGIMES ON SOIL AND TISSUE 3.1 Summary of Main E f f e c t s Variation due to both nutrients and moisture was highly s i g n i f i c a n t (p=0.01) f o r p r a c t i c a l l y a l l of the s o i l and tissue variables tested (Table 2 ) . A highly s i g n i f i c a n t (p=0.01) i n t e r a c t i o n between nutrients and moisture was also generally detected. These r e s u l t s demonstrate the separate and combined e f f e c t s of nutrients and moisture on s o i l nutrient a v a i l a b i l i t y , seedling growth, nutrient uptake, and tissue nutrient concentration. / 5 3 TABLE 2. Analysis of variance of s o i l and tissue nutrient and seedling growth parameters Main E f f e c t s Source of v a r i a t i o n : Treatments N M NxM Block Degrees of freedom: 15 SOIL: Exchangeable K Exchangeable Ca Exchangeable Mg Exchangeable NHij, " Extractable' NO3 •Available' P E l e c t r i c a l Conductivity PH SEEDLING: Shoot Height Amount of New Growth Root Length Stem Diameter Root Weight Stem Weight Live Foliage Weight Dead Foliage Weight Total'Seedling Weight Root/Shoot TABLE 2. (cont'd) /54 Main E f f e c t s Source of v a r i a t i o n : Treatments N M NxM Block Degrees of freedom: 15 SEEDLING: foN i n Foliage foP i n Foliage %K i n Foliage %Mg i n Foliage %Ca i n Foliage Mn i n Foliage (ppm) N/P i n Foliage Weight of N i n Foliage Weight of P i n Foliage Weight of K i n Foliage Weight of Mg i n Foliage Weight of Ca i n Foliage foN i n Stems %P i n Stems foK i n Stems %Mg i n Stems %Ca i n Stems Mn i n Stems (ppm) N/P i n Stems Weight of N i n Stems ** tttt ** tt* tt* tttt tttt tttt ** tttt tttt tttt tttt ** tt* tt* ** ** tttt ** *tt tt* ** ** ** tt* ** ** tttt ** * ** ** tt* *tt ** ** tttt ** * tttt tttt tttt tt* tt* tttt tttt tt tttt tttt tttt tt* ** ** ** tttt ** *» tttt ** TABLE 2. (cont'd) / 5 5 Main E f f e c t s Source of va r i a t i o n ; Treatments N M NxM Block Degrees of freedom; 15. _2_ SEEDLING: Weight of P i n Stems Weight of K i n Stems Weight of Mg i n Stems Weight of Ca i n Stems $N i n Roots foP i n Roots foK i n Roots $Mg i n Roots $Ca i n Roots Mn i n Roots (ppm) N/P i n Roots Weight of N i n Roots Weight of P i n Roots Weight of K i n Roots Weight of Mg i n Roots Weight of Ca i n Roots Tot a l Weight of N/Seedling To t a l Weight of P/Seedling T o t a l Weight of K/Seedling To t a l Weight of Mg/Seedling ** ## ** ## #* ** #* ** ## ** ** ** *# *• ** #* #* •*# ** •*# #* ** •8-if-** #* ## #* •*# #* ## #* •»••* #* ** ** *# #«• ** ** ** TABLE 2. (cont'd) / 5 6 Source of v a r i a t i o n : Treatments Main E f f e c t s N M NxM Block Degrees of freedom; 15. SEEDLING: Tota l Weight of Ca/Seedling To t a l N/P per Seedling * S i g n i f i c a n t at p=0.05 ** S i g n i f i c a n t at p=0.01 / 5 7 3.2 Exchangeable S o i l Cations Variations i n amounts of exchangeable potassium, calcium, and magnesium due to both moisture and nutrient treatments were highly s i g n i f i c a n t (Tables 3, 4, 5 ) « The increase i n exchangeable cations with increased nutrient l e v e l was l a r g e l y a r e f l e c t i o n of the amount of cation additions p r i o r to the s t a r t of the experiment. However, the general reduction of exchangeable cations with increased moisture (most apparent at higher nutrient l e v e l s ) i s much more d i f f i c u l t to explain. Under f i e l d conditions, cation leaching would generally be expected to increase with increased s o i l moisture, thereby giving data similar i n trend to tha.t obtained i n t h i s study. Also, the wetter s o i l regimes i n th i s study were characterized by lowered pH (Table 10) which would r e s u l t i n the lowering of cation exchange capa.city and an increased supply of H + ions to displace cations from the exchange complex. Moreover, high l e v e l s of n i t r a t e (Table 7) and sulphate ions were present i n the higher nutrient treatments to accompany the cations downward through the rooting zone. However, i n th i s study, s o i l nutrients were cycled within a closed system. Drainage from the bottom of the pots was collected and added to the top of the pots as i r r i g a t i o n water. Leaching losses were . minimal, and therefore do not explain decreased cation concentration i n the wetter moisture treatments. TABLE 3. /58 Exchangeable s o i l K (meq/lOOg), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Level Relative Nutrient Level 1 0 . 038 I 0 . 0 6 5 0 . 0 8 7 0 . 1 3 4 2 0 . 0 3 0 0 . 0 6 8 0.081 0 . 1 2 9 3 0 . 0 3 3 0 . 0 6 5 0 . 0 8 2 0 . 1 2 2 4 0.0.31 0 . 0 6 6 0 . 0 8 0 0.114 Averages O.O33 0.066 0 . 0 8 3 0.125 Averages 0. 081 0.077 O.O76 0.073 TABLE 4. Exchangeable s o i l Ca (meq/lOOg), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Level 1 2 3 4 Averages Relative Nutrient Level 0.182 a 0.225 0.256| 0.343 0.166 0.214 0.233| 0.331 O.I77 a 0 .193| 0.197 0.242| 0.162 0.172| 0.202 0.217| U . i y i U.200 0.222 0.283 Averages O .252I 0.235| 0.202| 0.188| Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /59 Increased cat ion uptake by seedlings growing i n the wetter moisture treatments offers a. p a r t i a l explanation for these r e s u l t s . However, increased nutr ient uptake c l e a r l y does not account for a l l of the reduct ion i n s o i l exchangeable ca t ion concentrat ion evident at the higher moisture l e v e l s . It i s poss ible that greater microb ia l a c t i v i t y i n the higher moisture treatments could have e f f e c t i v e l y t i e d up s i g n i f i c a n t amounts of exchangeable bases. /6o 3 . 3 S o i l Ammonium N i t r o g e n V a r i a t i o n i n ammonium (NH^ +) n i t r o g e n c o n c e n t r a t i o n due t o b o t h m o i s t u r e and n u t r i e n t t r e a t m e n t s was h i g h l y s i g n i f i c a n t ( T a b l e 6), as was m o i s t u r e x n u t r i e n t i n t e r a c t i o n . Ammonium-N c o n c e n t r a t i o n i n c r e a s e d w i t h n u t r i e n t s u p p l y , e s p e c i a l l y i n t h e two d r i e s t m o i s t u r e t r e a t m e n t s . C o n v e r s e l y , NHij,+-N c o n c e n t r a t i o n d e c r e a s e d w i t h i n c r e a s e d m o i s t u r e l e v e l . These r e s u l t s are l a r g e l y a response t o the amount o f n i t r o g e n a d d i t i o n s p r i o r t o the s t a r t o f the st u d y and subsequent n i t r o g e n t r a n s f o r m a t i o n s w i t h i n the v a r i o u s m o i s t u r e t r e a t m e n t s . N i t r o g e n was added m a i n l y as NHzj,+-N at t h e b e g i n n i n g o f the ex p e r i m e n t . S o i l m o i s t u r e i n th e 1M and 2M t r e a t m e n t s was in a d e q u a t e t o enable s u b s t a n t i a l n i t r i f i c a t i o n t o ta k e p l a c e . T h e r e f o r e , n i t r o g e n remained l a r g e l y i n the form o f NH^-N th r o u g h o u t the stu d y p e r i o d . These r e s u l t s are l a r g e l y i n a c c o r d w i t h t h o s e r e p o r t e d by Sabey (1969)1 who found n i t r a t e a c c u m u l a t i o n t o be p r o g r e s s i v e -l y reduced as s o i l w a ter t e n s i o n i n c r e a s e d . C o n v e r s e l y , p l e n t i f u l s o i l m o i s t u r e e f f e c t e d s u b s t a n t i a l n i t r i f i c a t i o n a c t i v i t y i n t h e two w e t t e s t m o i s t u r e t r e a t m e n t s , r e s u l t i n g i n g e n e r a l l y low NH^+-N c o n c e n t r a t i o n s and i n s i g n i f i c a n t d i f f e r e n c e s between n u t r i e n t t r e a t m e n t s . TABLE 5« /61 Exchangeable s o i l Mg (meq/lOOg), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M.) Relative Moisture Relative Nutrient Level Averages Level 1 2 3_ 4 _ _ _ _ _ 1 0.018' 0.022 0.022 0.040 0.0261 2 0.014 0.023 0.020 0.040 0.0241 3 0.015 0.018 0.020 0 .036 0.022 4 0.014 0.016 0.021 0.031 0.021 Averages 0.015 0.020 0.021 0.036 TABLE 6. Exchangeable s o i l NH^-N (ppm), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Level 1 2 3 4 Relative Nutrient Level Averages 1 2 3 4 3.6 37.6 - 61.2 103.7| 51.51-2.2 a • 26.7 ^2.4 78.2| 39.9l 1.8 7-0 7.2 34.1| 12.5l 2.5 a 2.5 3-8 7-8| 4.1I :• 2.5 18 .4 31.1 55. 9 Averages Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /62 3-4 S o i l Nitrate Nitrogen Variation i n n i t r a t e (NO^-) nitrogen concentration due to both moisture and nutrient treatments was highly s i g n i f i c a n t (Table 7) as was moisture x nutrient i n t e r a c t i o n . Nitrate-N concentration increased with nutrient supply, es p e c i a l l y i n the two wetter moisture treatments. Nitrate-N concentration also increased with moisture supply. As with differences i n NH^+-N concentration, these r e s u l t s are larg e l y a response to the amount of nitrogen additions p r i o r to the start of the study and the effe c t of s o i l moisture on n i t r i f i c a t i o n p o t e n t i a l . The increase i n NO^~-N concentration with increased moisture l e v e l i s largely a res u l t of the b e n e f i c i a l e f f e c t s of increased s o i l moisture on n i t r i f i c a t i o n . In addition to the favorable effects of adequate s o i l moisture, n i t r i f i c a t i o n a c t i v i t y may have been enhanced by low cation exchange capacity of the s o i l . Under conditions of low CEC, NH^+-N adsorption i s small, r e s u l t i n g i n a greater amount of NH^+-N i n the s o i l solution available f o r n i t r i f i c a t i o n (Smith 1964). N i t r i f i c a t i o n i s supposedly i n h i b i t e d by poor s o i l aeration, since i s required i n both steps of the n i t r i f i c a t i o n process (Hausenbuiller 1972). Alexander (1965) reported that a l l n i t r i f y i n g bacteria, with the possible exception of one, are obligate aerobes and s o i l conditions that r e s t r i c t aeration should also r e s t r i c t n i t r i f i c a t i o n . / 6 3 TABLE 7 . Extractable s o i l N0~-N (ppm), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Relative Nutrient Level Averages Level 1 2 3 '4 1 6 . 8 24 .6 3 3 . 7 3 9 , 2 : 2 6 . l t 2 ill 3 8 . 5 5 5 - 5 ! 6 9 . 9 42 .6| 3 1 1 . 6 7 7 . 6 1 2 6 . 1 1 6 9 . 5 9 6 . 2 4 9 . 7 8 8 . 6 128 .2 1 7 9 . 7 1 0 1 . 6 Averages 8 . 7 5 7 - 3 8 5 - 9 114 .6 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p= 0 . 0 5 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at-p= 0 . 0 5 /6k In t h i s study, n i t r i f i c a t i o n did not increase beyond moisture l e v e l 3M, but the data suggest t h i s was due more to lack of an ammonium source than to a decrease i n n i t r i f i c a t i o n p o t e n t i a l (Table 6). Therefore, i t would appear that either the kM moisture treatment was not as wet as expected, or s o i l microbial r e s p i r a t i o n and seedling root r e s p i r a t i o n were not s u f f i c i e n t l y high to reduce s o i l aeration as much as might o r d i n a r i l y be expected. ] / 6 5 3 . 5 Total 'Available' Nitrogen i n S o i l Due to differences i n the amount and rate of nitrogen transformation, the r e l a t i v e amounts of NH^+-N and N03~-N varied greatly among treatments. In the wetter treatments, NO^'-N accounted f o r up to 9 7 % of the t o t a l available inorganic nitrogen. In the d r i e r treatments, up to 7 3 % of available N was in;the form of NH^+-N. Many workers have shown nitrogen form to s i g n i f i c a n t l y affect seedling growth and nutrient uptake (Krajina et a l . 1973> van den Driessche 1 9 7 1 ; van den Driessche and Dangerfield 1 9 7 5 ; Nelson and Selby 1 9 7 4 ) . I t would therefore seem probable that seedling growth and nutrient uptake differences between the various nutrient and moisture treatments were attributable not only to differences i n t o t a l available N but also to r e l a t i v e differences i n nitrogen form. Available s o i l nitrogen generally increased with s o i l moisture (Table 8 ) . Data presented i n Table 9 suggest t h i s was lar g e l y due to poor inorganic nitrogen recovery i n the d r i e r moisture treatments. At the completion of the study, as l i t t l e as 42% of the N added to the dr i e s t treatment was recovered i n s o i l and seedling t i s s u e . This phenomenon may be at least p a r t i a l l y attributable to clay f i x a t i o n of NH^ +-nitrogen. Vermiculite and other 2 : 1 type clays have the a b i l i t y to ' f i x ' NH^+ ions i n the int e r m i c e l l a r space /66 TABLE 8. Sum of exchangeable s o i l N H K - N (ppm) and extra.cta.ble s o i l N O - - N (ppm;, i n r e l a t i o n to r e l a t i v e nut r i ent regime ( N ) and mois-ture regime (M) Relat ive Moisture Relat ive Nutrient Level Averages Level 1 2 3 4 1 10.4 62.2 94.9 142.9 77.6 2 8.9 65.2 107.9 148.1 82.5 3 13.4 84.6 133.3 203.6 108.7 12.2 91.1 132.0 187.5 . 105.7 Averages 11.2 75-7 117.0 170.5 /67 TABLE 9. Percentage of added N recovered at the end of the experiment, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Relative Nutrient Level Averages Level 1 2 3 4 1 393 54 51 42 135 2 467 58 57 44 156 3 720 75 70 59 _ 231 4 747 80 72 55 238 Averages 582 67 62 50 / 6 8 of the clay c r y s t a l (Buckman and Bra'dy 1969) . Fixed ammonium i s largely unavailable f o r uptake and would not be recovered by the extraction method used i n t h i s experiment. Ammonium f i x a t i o n i s generally greatest under dry s o i l conditions (Black 1968). Upon drying, the clay c r y s t a l l a t t i c e of 2 :1 clays shrinks, e f f e c t i v e l y trapping the NH^ + ions within the in t e r m i c e l l a r space. The fact that s o i l s of the dry moisture treatments were o r i g i n a l l y wetted during nutrient addition and subsequently allowed to dry to the desired moisture l e v e l would o f f e r prime conditions for f i x a t i o n to occur. The s o i l used i n t h i s experiment had. only a f i v e per cent clay f r a c t i o n . Moreover, the mineralogy of the clay i s not known. Although Bourgeois (1969) found the clay f r a c t i o n of podzolic s o i l s at the U.B.C. Research Forest to be lar g e l y vermiculite, i t i s doubtful whether f i x a t i o n alone accounted for the low nitrogen recovery of the dr i e r moisture treatments. Low available nitrogen recoveries i n the high moisture - high nutrient treatments may be large l y attributable to d e n i t r i f i c a t i o n losses. D e n i t r i f i c a t i o n i s generally most pronounced under conditions of poor s o i l aeration and abundant NO3- supply (McGarity 1 9 6 l ; P i l o t and Patrick 1972) . Under these conditions, NO^- i s u t i l i z e d as a terminal electron acceptor by f a c u l t a t i v e anaerobes. / 6 9 Reduction-, may l e a d t o the l i b e r a t i o n o f n i t r o u s o x i d e ( N £ 0 ) and d i n i t r o g e n (N2) (Cooper and Smit h 1 9 6 7 3 ) . Under a p p r o p r i a t e c o n d i t i o n s , l a r g e d e n i t r i f i c a t i o n l o s s e s may o c c u r over a v e r y s h o r t time p e r i o d . I n t h i s e x p e r i m e n t , s u b s t a n t i a l l o s s e s may have o c c u r r e d soon a f t e r n u t r i e n t a d d i t i o n , assuming n i t r i f i c a t i o n was r a p i d . T h i s would not o n l y account f o r low n i t r o g e n r e c o v e r y i n the w e t t e r s o i l t r e a t -ments but would a l s o o f f e r a f u r t h e r e x p l a n a t i o n f o r the low n i t r o g e n r e c o v e r y i n the d r y t r e a t m e n t s . V o l a t i l i z a t i o n l o s s e s o f ammonia (NH^) have o f t e n been shown t o o c c u r f o l l o w i n g n i t r o g e n f e r t i l i z a t i o n . L o s s e s o f up t o 32$ o f the urea-N a p p l i e d t o f o r e s t s o i l s have been r e p o r t e d ( C a r r i e r and B e r n i e r 1971) ' V o l a t i l i z a t i o n l o s s e s f o l l o w i n g u r e a a p p l i c a t i o n r e s u l t from the r i s e i n pH a s s o c i a t e d w i t h u r e a h y d r o l y s i s . However, l o s s e s f o l l o w i n g (NH/j.)2^0^ f e r t i l i z a t i o n o f f o r e s t s o i l s have g e n e r a l l y been m i n i m a l ( B e r n i e r ejt a l . 1972; C a r r i e r and B e r n i e r 1971) . T h e r e f o r e , due t o the low pH o f the e x p e r i m e n t a l s o i l , i t i s u n l i k e l y t h a t v o l a t i l i z a t i o n l o s s e s , as ammonia, o f a p p l i e d n i t r o g e n were h i g h . The f a c t t h a t n i t r o g e n was added i n s o l u t i o n and t h o r o u g h l y mixed w i t h the s o i l would a l s o t e n d t o m i n i m i z e ammonia v o l a t i l i z a t i o n p o t e n t i a l . The p o t e n t i a l f o r i m m o b i l i z a t i o n o f added n i t r o g e n by s o i l m i c r o b e s i s g e n e r a l l y i n d i c a t e d by a wide r a t i o o f /70 t o t a l s o i l carbon to t o t a l s o i l nitrogen (C:N). Under these conditions, a lack of nitrogen f o r microbial growth would not only tend to l i m i t the rate of organic matter decomposition, but would also re s u l t i n what l i t t l e mineralized nitrogen there was being assimilated (immobilized) by the microbial population. The C:N r a t i o of the experimental s o i l p r i o r to nutrient addition was 26:1, which i s s i g n i f i c a n t l y higher than generally found i n a g r i c u l t u r a l s o i l s (Tisdale and Nelson 1975)• However, several workers have reported that C:N r a t i o s of t h i s magnitude favor net mineralization of N i n forest s o i l s (Lutz and Chandler 1959; Edmonds 1979, 1980; Otchere-Boateng 1980). Z o t t l (i960) observed net mineralization i n some forest humus samples having a C:N r a t i o of about 40. Since the lowest nutrient treatment i n t h i s study experienced a net mineralization of nitrogen, immobilization of large amounts of added nitrogen i n the other nutrient treatments would not be expected, unless microbial populations were subs t a n t i a l l y higher i n these other treatments. The high n i t r i f i c a t i o n rates evident i n the high moisture - high nutrient regime.sv:did i n fact suggest the existence of a large s o i l microbial population, which may have resulted i n the incorporation of available s o i l nitrogen i n microbial body tiss u e . /71 3.6 S o i l pH S o i l pH g e n e r a l l y d e c r e a s e d s i g n i f i c a n t l y w i t h i n c r e a s e d s o i l m o i s t u r e (Table 1 0 ) . T h i s was un d o u b t e d l y l a r g l e y due t o i n c r e a s e d n i t r i f i c a t i o n a c t i v i t y i n the h i g h e r m o i s t u r e t r e a t m e n t s . The c l o s e r e l a t i o n s h i p between N0^ -N and s o i l pH i s shown by the h i g h l y s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n between the s e two v a r i a b l e s (r=-0.7839). T h i s c o r r e l a t i o n was even h i g h e r when d a t a were s t r a t i f i e d by m o i s t u r e l e v e l (r=-0.9520 and -0.8551 at 3M and 4M, r e s -p e c t i v e l y ) . N i t r i f i c a t i o n i s a two-step p r o c e s s i n v o l v i n g o x i d -a t i o n o f ammonium (NH^ +) t o n i t r i t e (N02~) and the subsequent c o n v e r s i o n o f n i t r i t e t o n i t r a t e (N0^ ). The two r e a c t i o n s are r e p r e s e n t e d by the f o l l o w i n g s i m p l i f i e d e q u a t i o n s : 2NH^ + + 2 0 2 2N0 2~ + 4H + + Energy 2N0 2~ + 0 2 -» 2N0^~ + Energy As seen i n the above r e a c t i o n s , the a c i d i f y i n g e f f e c t o f n i t -r i f i c a t i o n stems f r o m t t h e f o r m a t i o n o f f r e e hydrogen (H +) i o n s . I n the case o f ammonium s u l p h a t e (NH^).2S0.y f e r t i l i z e r , n i t r a t e and s u l p h a t e a n i o n s b o t h form s t r o n g a c i d s w i t h f r e e H + i o n s . T h i s r e a c t i o n i s r e p r e s e n t e d v e r y s i m p l y as f o l l o w s : ( N H ^ ) 2S0^ + ^ 0 2 - » 2HN0 3 + H 2S0^ + 2H"20 The e x p e r i m e n t a l s o i l was c h a r a c t e r i z e d by a f a i r l y low c a t -i o n exchange c a p a c i t y (I4meq/l00g) and t h e r e f o r e was not w e l l b u f f e r e d a g a i n s t changes i n s o i l pH. C o n s e q u e n t l y , the r e a c -/72 TABLE 10. S o i l pH, i n r e l a t i o n t o r e l a t i v e n u t r i e n t regime (N) and m o i s t u r e regime (M) R e l a t i v e M o i s t u r e R e l a t i v e N u t r i e n t L e v e l Averages L e v e l 1 2 3 4 1 4.8 4.9 5.o| 5- 3| 5-o| 2 . 4.8 ah 4.4 4.6P 5.0 P 4v7| 3 4.7 4.1 4.1 4.0 4.2 4 4.7 4.1 4.0 3- 9 4.2 Averages 4.8 4.4 4.4 Means connected from each o t h e r hy at the same l i n e do p=0.05 not d i f f e r s i g n i f i c a n t l y Means marked w i t h the same l e t t e r do not d i f f e r s i g n i f i c a n t l y f rom each o t h e r at p=0.05 /73 tions associated with n i t r i f i c a t i o n generally resulted i n the formation of highly a c i d i c s o i l environments. N i t r i f i c a t i o n i s supposedly i n h i b i t e d by low s o i l pH, and therefore tends to be a. s e l f - l i m i t i n g process (Hausenbuiller 1972). However, the almost complete n i t r i f i c -a tion of ammonium ions i n the treatments with lowest pH (Tables k, 5» and 8) suggests that a c i d i c s o i l environments may not seriously impede n i t r i f i c a t i o n p o t e n t i a l provided other factors remain favorable. This phenomenon may be at le a s t p a r t i a l l y explained by the r e l a t i v e l y high exchangeable base status of s o i l i n the higher nutrient treatments. Nit-r i f y i n g b a c t e r i a require an abundance of exchangeable bases, and adequate supplies may l a r g e l y o f f s e t low s o i l pH. The response of s o i l pH to added nutrients varied with moisture treatment ( i . e . a. highly s i g n i f i c a n t nutrient x moisture i n t e r a c t i o n was evident). M the higher moisture l e v e l s , s o i l pH declined with increased nutrient l e v e l . The decline was d i r e c t l y related to the amount of (NH^gSO^ added, presumably because of sulphuric and n i t r i c acid production. In the d r i e s t moisture treatment, s o i l pH increased s i g -n i f i c a n t l y with increased nutrient regime. The higher nut-r i e n t treatments were characterized by high base saturation. When water was added fo r pH determination, hydolytic displace-ment of exchangeable bases resulted i n increased s o i l pH. 3-7 S o i l E l e c t r i c a l Conductivity E l e c t r i c a l conductivity i s a measure of the a b i l i t y of a s o i l solution to conduct an e l e c t r i c current. It i s also a useful measure of the t o t a l ion concentration of a s o i l solution, since conductivity c l o s e l y p a r a l l e l s concentration regardless of the kinds of ions present. Variation i n e l e c t r i c a l conductivity due to both moisture and nutrient treatments was highly s i g n i f i c a n t . E l e c t r i c a l conductivity increased s i g n i f i c a n t l y with nutrient supply (Table 11). This increase can be d i r e c t l y related to the greater concentrations of exchangeable bases and nitrate-N i n the higher nutrient treatments. E l e c t r i c a l conductivity also increased s i g n i f i c a n t l y with moisture supply. Reduction of iron and manganese to 2 + 2 + the highly soluble ferrous (Fe ) and manganous (Mn ) forms and increased s o l u b i l i t y of aluminum at high s o i l moisture probably contributed most to t h i s increase. A l l EC values presented i n Table 11 are well below values generally f e l t to be indi c a t i v e of s o i l s a l i n i t y problems i n agriculture (U.S. S a l i n i t y Laboratory St a f f 1954) . However, the generally accepted c r i t i c a l ^ EC value (4 millimhos/cm) must be considered as an average that i s subject to r e v i s i o n f o r s p e c i f i c circumstances / 7 5 TABLE 11. S o i l e l e c t r i c a l conductivity (micromhos), i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Relative Nutrient Level Averages Level 1 2 _ 1 4 1 61 2961 539 1 H2Zl 1 526| 2 •gl 612! 13,33 a 594| 3 12 4o6 673 1450 652 4 79 412 683 1357 a 633 Averages 69 371 628 1337 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 ) /76 (Black 1968). The moisture content of the saturat ion extract i s much higher than that present i n the lower moisture regimes of the present study. The lower the water content of the s o i l , the more concentrated are the s a l t s and the lower i s the osmotic p o t e n t i a l . Accordingly , a given s p e c i f i c conduct iv i ty of saturat ion extracts would correspond to higher e f fec t ive s a l i n i t y for plants growing i n d r i e r s o i l s (Black 1968). /II 3. 8 F o l i a r Damage Seedlings i n a l l but the nutr ient poor and/or very dry treatments showed signs of f o l i a r damage (Table 12) . High and severe damage was confined to those treatments with high nutr ients and/or high moisture. T y p i c a l damage symptoms began with a general ch loros i s and c u r l i n g upwards of needle t i p s followed by death of cotyledons and necros i s of older fo l iage beginning at needle t i p s . Purpl ing and ro se t t ing of new growth, top dieback and even seedling death occurred i n severe cases. L a t e r a l branching was stimulated i n the high nut r i en t -high moisture treatments, although many of the side branches died as f o l i a r damage progressed. The fact that f o l i a r damage was l a rge ly confined to the higher nutr ient treatments suggested some type of n u t r i t i o n a l d i sorder . Unfortunately , a d e f i n i t i v e diagnosis was not poss ible by v i s u a l observat ion, since most symptoms were general ly common to a number of elemental d e f i c i e n c i e s . However, the purp l ing of fo l iage did suggest an acute phos-phorus def ic iency (Trappe and Strand 1969; Heilman and Ekuan 1980) , and ro se t t ing of new growth was ind ica t ive of various micronutrient de f i c i enc ie s (e .g . Zn, Cu, B) documented i n other species (Stone 1968) . The stimulus of l a t e r a l branching was s i m i l a r to that reported for ca lc ium-def ic ient Douglas-f i r seedlings (Kra j ina 1959)- Top dieback and necros is of /78 TABLE 12. F o l i a r damage, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Relative Nutrient Level Averages Level 1 2 3 k 1 N N L M L 2 N M M H M 3 L M H S M k L H H S H Averages L M M H N - none L - low M - moderate H - heavy S - severe / 7 9 f o l i a g e was a l s o c o n s i s t e n t w i t h symptoms r e p o r t e d f o r calcium d e f i c i e n t f o l i a g e of other c o n i f e r s ( M i t c h e l l 1939; P u r n e l l 1958). The e f f e c t s of t i s s u e n u t r i e n t contents, concen-t r a t i o n s , and r a t i o s on f o l i a r damage, s e e d l i n g n u t r i t i o n , and growth are d i s c u s s e d i n d e t a i l under the a p p r o p r i a t e headings. /80 3-9 Seedling Growth Seedling growth was much slower than would normally "be expected under greenhouse conditions, especially in those treatments adequately supplied with s o i l moisture. The fact that the study was conducted during the winter months when the amount and duration of far-red radiant energy from natural daylight was lim i t e d , may p a r t i a l l y account f o r the general growth i n h i b i t i o n common to a l l treatments. In t h i s regard, the supplementation of fluorescent l i g h t i n g with a r t i f i c i a l incandescent l i g h t i n g possibly would have encouraged shoot extension. Many workers have reported reduction i n terminal growth, budset, and onset of dormancy i n conifer seedlings grown under conditions of moisture stress (Zahner 1962; Stransky and Wilson 1964; Lavender et a l . 1968; Young and Hanover 1978). Seedlings i n the d r i e r moisture treatments i n t h i s study formed terminal buds and ceased shoot extension completely. Growth i n h i b i t i o n induced by moisture stress i s undoubtedly largely due to stomatal closure and associated reduction i n tra n s p i r a t i o n rate and photosynthetic a c t i v i t y reported i n conifers by Lopushinsky and Klock (1974) . F o l i a r damage symptoms discussed i n the previous section strongly suggested that n u t r i t i o n a l disorders were i n large measure responsible for growth i n h i b i t i o n i n those treatments adequately supplied with moisture. /81 Many s i g n i f i c a n t treatment differences were evident even though differences were p a r t i a l l y masked "by the growth i n h i b i t i o n common to a l l treatments. A l l of the measured growth variables displayed highly s i g n i f i c a n t increases i n magnitude with increased moisture (Tables 13 to 21 ) . These data i l l u s t r a t e the importance of adequate s o i l moisture for favorable seedling growth, and are i n general agreement with those obtained by Schomaker (1969) with pine and McClain and Armson (1975) with pine and spruce. However, whereas these workers reported the favorable e f f e c t of s o i l moisture on seedling growth to be less dramatic under the low nutrient regimes, growth increases (both r e l a t i v e and absolute) with increased moisture i n t h i s study were often greatest i n the lower nutrient treatments. This difference i s undoubtedly largely due to the growth i n h i b i t i o n common to the higher nutrient l e v e l s i n t h i s study. While Schomaker (1969) reported a highly s i g n i f i c a n t increase i n seedling weight with increased moisture at the highest nutrient l e v e l , differences i n seedling weight and other growth variables i n t h i s experiment were generally i n s i g n i f i c a n t at the high nutrient l e v e l s . A l l of the measured growth variables also displayed highly s i g n i f i c a n t differences due to nutrients. / 8 2 TABLE 13. Seedling shoot height (cm), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture L e v e l 1 2 3 4 Rela t ive Nutr ient Leve l 4 . 4 0 4.76 4.86| 4.89| 4.66 5.31 5.5^1 5.54 5.55 5..61 5.86 5-83 ^•93 5.66 6.06 5.96 Averages 5.13 5*33 5.56 5-57 Averages 4.731 5.271 .5.691 5.90| TABLE 14 . Amount of seedl ing shoot growth (cm) during the treatment per iod , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture L e v e l 1 2 3 4 Relat ive Nutr ient Leve l 0.75[ 1.19P 1.61J 1.49f 1,26| l . ? 8 | 2 . 1 0 | 2.10 1.95 2.38 2.47 2.56 2 . 2 4 2.44 2.79 2.75 T75E 1 7 9 4 " Averages 1.25J 1.81J 2.34J 2.55| Averages 2.23 2.22 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /83 TABLE 15. Seedling root length (cm), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture Leve l 1 2 3 4 Rela t ive Nutr ient Leve l 14.9 14.8| 14.4 14.0 16.1 16.6| 15.5 14.2 17.6 17.8 16.2 16. o| 18.1 18.5 18.1 18. 0| Averages 1 5-61 1 6 . 9 1 18.2| Averages 16.7 16.9 16.1' 15.5 TABLE 16. Seedling stem diameter (cm), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive O.98 1.07 Moisture Rela t ive Nutr ient Leve l Averages Leve l 1 2 3 4 1 0.74] 0.82i 0.92| 0.89| 0.84| 2 0.891 0.97 1.01 1.09 0 . 9 9 1 3 1.00 1.05 1.08 1.08 1.05 4 1.03 1.07 . 1.08 1.20 1.09 Averages 0.91 1.02 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /84 TABLE 17. Seedling root weight (g), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture Rela t ive Nutr ient Leve l Averages L e v e l 1 2 3 4 1 0.058| 0 . 062b o.o6l| 0.046 0.0571 2 0.091J 0 . 0 7 8 b 0 . 0 7 3 a O.067 0 . 0 7 7 c 3 0.120| 0.105I o .097| 0.070 O.098I 4 o.lo6| 0 . 0 8 1 b 0 . 0 7 8 a 0.069 0.083° Averages 0.094 0.081 O.077 0.063 TABLE 18. Seedling- stem weight (g), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Leve l 1 2 3 4 Rela t ive Nutr ient Leve l 0.015 0.017 a 0.021| 0.020] 0.020 0.022 0.0251 0.030 0.024 0.028 0.031 0.030 0.027 0.030 0.033 0.036 a Averages 0.018] 0.024| 0.028| 0.031| Averages 0.021 0.024 0.027 0.029 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /85 TABLE 19. Live fo l i age weight per seedl ing (g), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture • ; regime (Iv!) Relative Moisture Level 1 2 3 4 Relative Nutrient Level L _2_ _3_ • J Averages 0 .030| 0.046 f 0 .052 0.041 b 0 .042 0 .046| 0.045 0 .040| 0.045 0 .044 0 .061 0.059 0 .058° 0.044 0 .056 0 .066 a. 0.053 0 . 0 6 l a c 0 .043 0 .056 Averages 0.051 0.051 0.053 0.043 TABLE 20. Dead fo l i age weight per seedl ing (g), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Relative Moisture Relative Nutrient Level Averages Level 1 2 3 4 1 0.000 0.000 . 0.002 0.005 .0.020 0.002I 2 0.000 0.009 0.018 0.012 3 0.000 0.010 0.015 0.023 0.012 4 0.000 0.014 0.014 0.025 0.013 Averages 0.000 0.007 0 .012 0.018 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p = 0 - 0 5 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p = 0 . 0 5 / 8 6 TABLE 2 1 . T o t a l seedl ing weight (g), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture L e v e l 1 2 3 4 Relat ive Nutr ient Leve l 0 . 1 0 3 b 0 . 1 2 5 a 0 . 1 3 4 0 .106P 0 .156I 0 . 1 4 5 a O . I 3 8 0.142 0 . 2 0 5 0.193 0 . 1 8 6 0.144 0 . 1 9 9 O . I 6 7 a 0 .171 0.148 0.166 0 . 1 5 7 0 . 1 5 7 ^ . 1 3 5 Averages 0 . 1 1 7 ! 0 .145| 0.182 0 .171 Averages TABLE 2 2 . Seedling root/shoot r a t i o (g/g), i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Rela t ive Nutr ient Leve l Averages L e v e l 1 2 3 4  1 I . 3 2 0 . 9 9 a 0 1 8 3 0 . 7 5 d 0 . 9 7 2 1 . 3 9 1 . 1 6 1 .14 0 . 9 0 1 . 1 5 3 1.42 1 . 2 1 1 . 1 0 0 - 9 5 1 . 1 6 4 1 .14 0 . 9 4 ac 0 . 8 3 b 0 . 8 7 z d 0 . 9 5 Averages . 1 . 3 2 1 . 0 7 O . 9 8 O .87 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /87 At the lowest moisture l e v e l (1M) , some growth parameters increased s i g n i f i c a n t l y i n magnitude with increased nutrient supply (Tables 14, 19, 2 1 ) . A similar trend was reported by Schomaker (1969), who attributed i t to "an increase i n photosynthetic a c t i v i t y and water economy with improved mineral n u t r i t i o n during a period of moisture stress." In defense of t h i s statement he cited Black ( 1968) . Viets (1962) also concluded that f e r t i l i z a t i o n can greatly increase the water use e f f i c i e n c y of a g r i c u l t u r a l crops. Whether nitrogen f e r t i l i z a t i o n of forest trees influences t h e i r water use e f f i c i e n c y i n terms of dry matter produced per unit of water used i s a question requiring further research (Gessel 1968 ) . However, a decrease i n the magnitude of many growth variables was often evident at the highest nutrient l e v e l , the decrease generally being most severe at the lowest moisture l e v e l (Tables 17 , 19, 2 1 ) . This, also, i s i n accordance with Schomaker's data, and appears to be the r e s u l t of increased s a l t concentrations i n the higher nutrient treatments. In addition to decreasing s o i l osmotic p o t e n t i a l , thereby inducing greater resistance to water uptake by roots, high s a l t concentrations may be injurious to roots ( H i l l e l 1971)• Mean seedling root weight and root/shoot ratios generally decreased s i g n i f i c a n t l y with increased nutrients (Tables 17, 2 2 ) . The strong negative c o r r e l a t i o n between /88 root/shoot and available s o i l NO^- (r=-.9520 at 2M) suggests that nitrogen i s the major nutrient responsible. These re s u l t s can be explained by 1) less need for a highly developed root system as s o i l nutrient a v a i l a b i l i t y i s increased, and 2) higher s u s c e p t i b i l i t y of roots to damage as s o i l s a l t concentration i s increased. Similar r e s u l t s are well documented i n the l i t e r a t u r e (Ingestad 1959» I960; McClain and Armson 1975; van den Driessche and Dangerfield 1975). Many workers have shown root/shoot r a t i o s to be increased by moisture stress (McClain and Armson 1965; Young and Hanover 1978). This trend was not c l e a r l y evident in t h i s study (Table 22), possibly due to the f o l i a r damage symptoms and growth i n h i b i t i o n i n the higher moisture -higher nutrient treatments. As a re s u l t of f o l i a r damage and associated growth i n h i b i t i o n , mean seedling weight did not increase with increased nutrients, except i n the driest moisture treatment (Table 21). These r e s u l t s are generally contrary to those reported by Schomaker '(1969) and McClain and Armson (1975). Visual assessment of mycorrhizae on seedling roots showed a noticeable increase i n mycorrhizal development with increased moisture, e s p e c i a l l y at the lower nutrient l e v e l s . S o i l moisture i s generally not regarded as a main factor influencing the s u s c e p t i b i l i t y of tree roots to mycorrhizal / 8 9 i n f e c t i o n ( H a r l e y 1969). H o w e v e r , e x t r e m e s o f m o i s t u r e may i n f l u e n c e t h e s u r v i v a l o f t h e f u n g a l s y m b i o n t s a n d , t h e r e b y , i n f l u e n c e t h e m y c o r r h i z a l p o t e n t i a l o f t h e s o i l ( M a r x and B r y a n 1975)• A t t h e h i g h m o i s t u r e l e v e l s , m y c o r r h i z a l i n f e c t i o n a p p e a r e d t o be i n h i b i t e d b y i n c r e a s e d n u t r i e n t s u p p l y . T h i s o b s e r v a t i o n i s i n a g r e e m e n t w i t h t h e w o r k o f F o w e l l s and K r a u s s (1959)> who r e p o r t e d t h a t u n d e r c o n d i t i o n s o f h i g h n i t r o g e n s u p p l y m y c o r r h i z a l d e v e l o p m e n t was i n h i b i t e d i n l o b l o l l y p i n e . B e n g t s o n and V o i g t (1962) f o u n d r o o t s o f s l a s h p i n e s e e d l i n g s g r o w n i n h e a v i l y f e r t i l i z e d s o i l t o be n o n - m y c o r r h i z a l . M a r x and B r y a n (1975) s t a t e t h a t e x c e s s i v e ! h i g h s o i l f e r t i l i t y w i l l r e d u c e , o r e v e n e l i m i n a t e , m y c o r r h i z d e v e l o p m e n t . / 9 0 N 3.10 Tissue Nitrogen The concentration of ni trogen i n f o l i a g e , root s , and stems increased s i g n i f i c a n t l y with increased nutr ient supply (Tables 2 3 , 2 4 , 2 5 ) . These r e su l t s are i n agreement with those obtained by Ingestad (1959» I 9 6 0 ) , Schomaker ( 1 9 6 9 ) , McClain and Armson ( 1 9 7 6 ) , and others , for f e r t i l i z e d seedlings of other species . Increased f o l i a r ni trogen concentration fo l lowing ni trogen f e r t i l i z a t i o n has also been reported i n Douglas- f i r (Heilman and Gessel 19635 Br ix 1972; van den Driessche and Dangerfield 1 9 7 5 ) . Tissue nitrogen content (mg/seedling) i n i t i a l l y rose and then general ly l e v e l l e d of f as nutr ient treatment increased, although the amount of ni trogen i n stems continued to r i s e s i g n i f i c a n t l y (Tables 2 6 , 2 7 , 28, 2 9 ) . Tissue nitrogen content and concentration general ly increased with increased moisture supply, although concentration increases were not always s i g n i f i c a n t . There was no evidence of a d i l u t i o n effect as has often been observed by others . Walker ( 1 9 6 2 ) , Pharis and Kramer ( 1 9 6 4 ) , Schomaker ( 1 9 6 9 ) , McClain and Armson ( 1 9 7 6 ) , and others a l l reported ni trogen concentration to be decreased with increased moisture supply, even though nitrogen uptake was increased. The fact that no d i l u t i o n was evident i n t h i s study was undoubtedly l a r g e l y due to the general ly repressed growth / 9 1 TABLE 23. Concentration {%) of nitrogen i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Relative Nutrient Level Averages Level 1 2 3 4 1 l . 6 o | 3.08 3.99 5.11 3.441 2 2 . 3 9 J 4.07 4.50 5.06 4.00 3 3.2?| 4.02 4.23 4.83 4.09 4 3-73J 4.44 5.22 1 5.13 4.631 Averages 2.75 3.90 4.48 5.03 TABLE 24. Concentration {%) of nitrogen i n stems, i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Relative Nutrient Level Averages Level 1 2 _3_ _4_ 1 O.77 a 1.10 1 . 4 3 | 2 . 4 2 b 1.43 2 O.63I 1.26 1.77 2.04 1.43 3 0.80 a 1.35 1.71 2.13 1.50 4 0.92 1.73 2.27| 2.56b 1.871 Averages O.78 1.36 1.79 2.29 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /92 TABLE 25 . Concentration (%) of ni trogen i n roots , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture Re la t ive Nutr ient Leve l Averages L e v e l 1 2 3 4 1 1.16 a 2.00 2.21 2.85 c d 2.05 2 1.20 " L 9 7 a 2.08 2.34 1.90J 3 1.24 1.69| 1.86 2.31 1-78| 4 1.47| 1 . 9 6 a 2.40 b 2.54 c d 2. 09 Averages 1.27 I .90 2 .14 2.51 'TABLE 26. Weight (mg) of ni trogen per seedl ing i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Rela t ive Nutr ient Leve l Averages Leve l 1 2 3 4  1 0.48| 1.40 2.08 2 . 0 9 1.52 2 1.08J • I .83 1. 80 2.25 1.74 3 2.00| 2.37 2.46 2 .14 2.241 4 2 . 4 7 | 2.47 3.19 2.22 2.59! Averages I.51 2 . 0 2 a 2.38 2 .18* Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /93 TABLE 27. Weight (mg) of ni trogen per seedl ing i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Re la t ive Nutrient L e v e l Averages L e v e l 1 2 3 4 1 0.11 0..19| 0.29 0.47 0 . 2 7 I 2 0.12 0.28| 0.43 0.61 O.36I 3 0.19 0.'38| 0.52 0.63 o.43| 0.25 0.52| 0.74J O.93J 0.6l| Averages 0.17 O.34 0.50 0.6.6 TABLE 28. Weight (mg) of ni trogen per seedl ing i n root s , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Relat ive Moisture Rela t ive Nutr ient Leve l Averages Leve l 1 2 3 4  1 0.67 1.24 r 1.35 1.29 1.14| 2 1.08 1.53 a 1.52 1-57 I.43I 3 1.49 1.77 1.81 1.62 I.67 4 1.56 1.-58 a 1.88 1.74 I.69 Averages 1.20 I.53 1.64 I.56 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 / 9 4 TABLE 29. T o t a l weight (mg) of ni trogen per seedl ing , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture Rela t ive Nutr ient Leve l Averages L e v e l 1 2 3 4 1 1.26| 2.83 3.72 3.85 2.92I 2 2.28J 3.64 3.75 4.43 3-531 3 3.68| 4.52 4.79 4.39 4.35| 4 4.28| 4.57 5.81 4.89 4.871 Averages 2.88 3.87 4.52 4.39 TABLE 30. T o t a l weight (mg) of phosphorus per seedl ing , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and mois-ture regime (M) Rela t ive Moisture Leve l Re la t ive Nutr ient Leve l Averages 1 0.101 0.098 a 0.094 0.091 O.096 2 0.108 0.091 a 0.085 0.093 0.094 3 0.142 0.128 0.117 O.O93 0.120 4 0.1.60| 0.107 a 0.118 0.101 0.122 Averages 0.128 0.106 0.103 0.094 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /95 i n the high nutrient - high moisture treatments. Since seedlings continued to accumulate nitrogen i n the high nutrient - high moisture treatments, i t i s evident that the repressed growth and f o l i a r damage common to these treatments was not due to nitrogen deficiency. In addition to the favorable e f f e c t s of increased moisture supply on nutrient uptake, nitrogen uptake has also been shown to be affected by the form of available N i n the s o i l ( i . e . NH^+-N vs. N0^~I-N) . van den Driessche and Dangerfield (1975) reported greater uptake of N0-^ ~-N than N H ! L + - N i n Douglas-fir seedlings. In t h i s experiment the majority of s o i l nitrogen i n the wetter treatments was i n the NO-^ ~-N form which may p a r t i a l l y account for the increased nitrogen uptake i n these treatments. T i s s u e nitrogen concentration was highest i n foliage and lowest i n stems, the same trend as that reported by van den Driessche ( 1 9 6 9 a ) . However, tissue nitrogen concentra-tions were much higher than reported by van den Driessche, f o l i a r l e v e l s r i s i n g as high as 5-2$ (Table 23). A c r i t i c a l f o l i a r concentration value has not yet been firmly established for Douglas-fir, but i t i s generally agreed that a concentration of i s probably adequate (Gessel et a l . I 9 6 0 ; van den Driessche 1969a; Everard 1973)' The author has been unable to fi n d any report i n the l i t e r a t u r e of f o l i a r nitrogen concentration as high as 5$> nor documented evidence that /96 young seedlings accumulate large amounts of n i t rogen. Data reviewed by van den Driessche (1969a) did suggest that N concentration i n needles of young seedlings tended to be higher than older seedl ings , which i n turn had higher concentrations than t rees , but di f ferences were not of s u f f i c i e n t magnitude to have relevance to the present study. Drought has been shown to increase Douglas- f i r f o l i a r n i t rogen concentration to 3% (Heiner 1968 from Waring and Youngberg 1972), but the highest f o l i a r N concentrations i n t h i s study were found i n the wettest treatments. Even f o l i a r ni trogen concentrations i n the lowest nutr ient treatment approached 4% at the highest moisture l e v e l , which suggests that growth i n h i b i t i o n caused by other factors has resul ted i n an accumulation of ni trogen i n seedl ing t i s sue . On the average, 50.5%, 10.2%, and 39.3% of t o t a l seedl ing ni trogen was contained i n the f o l i a g e , stems, and roots , r e spec t ive ly . /97 3-11 Tissue Phosphorus The t o t a l phosphorus content per seedl ing generally-increased with increased moisture hut decreased with increased n u t r i e n t s , although dif ferences were often not s i g n i f i c a n t (Table 3 0 ) . V a r i a t i o n due to both moisture and nutr ient treatments was greatest i n seedling roots , where phosphorus content was highest (Table 3 3 ) ' On the average, 25.1%, 15.1%, and 59 .6% of t o t a l seedl ing phosphorus was contained i n the f o l i a g e , stems, and roots , r e spec t ive ly (cf . n i t rogen) . S imi lar accumulation of P i n roots has been documented (Ingestad 19591 I 9 6 0 ) , e spec i a l ly i n mycorrhizal ones (see Harley I 9 6 9 ) . The increased phosphorus uptake evident i n the higher moisture treatments i s undoubtedly the re su l t of a combination of 1) increased mobi l i ty of P i n the s o i l s o l u t i o n , and 2) increased mycorrhizal i n f e c t i o n of seedl ings . The greatest uptake occurred i n the low nutr ient - high mois-ture treatment, i n which seedlings displayed the greatest v isual" evidence of mycorrhizae ( F i g . 3)« -Phosphorus concentration i n f o l i a g e , stems, and roots general ly decreased with increased moisture (Tables 3 ^ f 3 5 i 3 6 ) , which was consistent with d i l u t i o n ef fects reported by Schomaker ( I 9 6 9 ) . F o l i a r phosphorus concentrations i n a l l treatments were extremely low, and of magnitudes very s i m i l a r to those /98 FIGURE 3» T y p i c a l mycorrhizal development i n low nutr ient high moisture treatments / 9 9 reported by Trappe a.nd Strand (1969) and Heilman and Ekuan (198O) for severely phosphorus-deficient young Dougla.s-fir seedlings. Visual f o l i a r deficiency symptoms and t o t a l seedling dry weight attained over a. comparable period were also very si m i l a r to the r e s u l t s reported by Heilman and Ekuan (1980). The above r e s u l t s , coupled with the very good positi v e c o r r e l a t i o n evident between seedling phosphorus content and t o t a l seedling dry weight (r=0.9660 at 3M) are strong evidence tha.t seedling growth i n t h i s study was greatly influenced by seedling phosphorus content, and that general growth i n h i b i t i o n common to a l l treatments was largel y due to phosphorus deficiency. The extremely high f o l i a r N/P r a t i o s present i n most treatments (Table 37) i s further evidence of acute phosphorus deficiency. Ingestad (1967), from his work with Scots pine and Norway spruce, suggested the 'optimum' N/p r a t i o i n plants to be 7 « 7 - Waring (1972) reported that when N was added alone to a. P d e f i c i e n t s o i l , the growth of Pinus r ad iata. (D. Don) was ac t u a l l y less than that obtained i n the u n f e r t i l i z e d control, apparently the r e s u l t of the disruption of the int e r n a l nitrogen-phosphorus balance induced by the nitrogen f e r t i l i z a t i o n . The extremely low f o l i a r phosphorus l e v e l s evident i n t h i s study may be attributed to a. combination of factors. As discussed previously, d i l u t i o n of f o l i a r phosphorus concentra.tion with increased moisture has been reported. /100 TABLE 31. Weight (mg) of phosphorus per seedl ing i n fo l iage i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture L e v e l Re la t ive Nutr ient Leve l Averages 1 0.026 0 . 0 2 8 a 0.029b 0 .028 0 . 028 e 2 0.027 0 .021| 0 .021| 0 . 0 2 2 0 . 023I 3 0.033 o.029a o.029b 0 . 0 2 2 0 . 028 6 4 O.O37 3 0 . 0 2 7 a d o . o 3 i b c 0.023 a 0 . e 030 Averages 0.031 0.0261 0.027 0 . 024 r TABLE 32. Weight (mg) of phosphorus per seedl ing i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Relat ive Moisture Rela t ive Nutr ient Leve l Averages L e v e l 1 2 3 4  1 0.013 0.012 0.013 0.019 0. 014 2 0.010 0.011 . p.015 0.022 a. 0.014 3 0.011 0.015 0.018 0.019 0.016| 4 0.013 0.015 0.022 0.024 a 0.019I Averages 0.012 0.013 0.01? 0.021 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /101 TABLE 33. Weight (rag) of phosphorus per seedl ing i n root s , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture L e v e l 1 2 3 4 Rela t ive Nutr ient L e v e l Averages 0.062 o.058a 0.052 0.044 O.054 0.071 o.059a 0.049 0.049 0.057 0.098 0.084J 0.070 O.052 O.076 0.110 0.065 0.065 0.054 0.074 Averages 0.085 O.O67 O.059 O.050 TABLE 3^« Concentration {%) of phosphorus i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Relat ive Moisture L e v e l 1 2 3 4 Relat ive Nutr ient Leve l 0.087I 0 .061I 0.056 0.068| 0.058 0.048 0.050 •a 0.052 0.049^  0.054 0.050 0.051 0.055 0.050 O.05I 0.053 Averages 0.0681 0.052 0.051 0.052 Averages 0.064 O.052 O.052 O.055 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 T A B L E 35- C o n c e n t r a t i o n (fo) o f phosphorus i n stems, i n r e l a t i o n t o r e l a t i v e n u t r i e n t regime (N) and m o i s t u r e regime (M) /102 R e l a t i v e M o i s t u r e L e v e l R e l a t i v e N u t r i e n t L e v e l 0.058° OTO33 0.063 C ' 0.1776" Averages 1 0.087 3 0.066J 0.065 a 0.0991 0.079 2 0.051 0.051 0.060 0.072 0.058 0.055 , 0.059 3 0.045 0.053 0.059 0.065 k 0.050 0.051 0.068a 0.066 Averages T A B L E 36. C o n c e n t r a t i o n {%) o f phosphorus i n r o o t s , i n r e l a t i o n t o r e l a t i v e n u t r i e n t regime (N) and m o i s t u r e regime (M) R e l a t i v e M o i s t u r e R e l a t i v e N u t r i e n t L e v e l Averages L e v e l 1 2 3 4  1 0.106 0.0951. 0.086 a 0.100| 0.0971 2 0.078 0.076 0.066 0.073 O.O73 3 0.081 0.080 b 0.072 0.074 b 0.077 4 0.103 0. 082 O.O83 a 0.079 0.086! A v e r a g e s 0.092 O.O83 0.077 0.081 Means connected by t h e same l i n e do n o t d i f f e r s i g n i f i c a n t l y f rom each o t h e r a t p=0.05 Means marked w i t h t h e same l e t t e r do n o t d i f f e r s i g n i f i c a n t l y f rom each o t h e r a t p=0.05 /103 The d i l u t i o n of f o l i a r phosphorus i n response to nitrogen f e r t i l i z a t i o n has also been documented (Heilman and Gessel 1963; Brix 1972; Timmer and Stone 1978). In some cases, the d i l u t i o n of f o l i a r P concentration ma.y progress to the point where a. P deficiency i s induced. The reduction i n the uptake ( i . e . tissue nutrient content) of phosphorus with increased nutrient supply ma.y be related to 'antagonisms' between N and P reported i n the l i t e r a t u r e , van Goor (1953) reported the content of phosphorus i n the f o l i a g e of Japanese larch (Larix l e p t o l e p i seedlings to be decreased by nitrogen f e r t i l i z a . t i o n . The poorer the s o i l was i n available phosphorus, the more ra p i d l y was seedling growth decreased as the supply of nitrogen was increased. Leyton (1957)> also with Japanese la r c h , found a. marked reduction i n the absolute P content of fol i a g e with increased N supply. How f a r t h i s applied to th tree as a. whole was not tested, but as far a.s foliage i s con cerned, there was documented evidence of a. d i r e c t antagon-i s t i c influence of nitrogen f e r t i l i z a t i o n on P content of needles. A s i m i l a r phenomenon was reported by Tamm (1956) f o r spruce, van den Driessche and Dangerfield (1975) re-ported shoot P concentrations of nit r a t e - f e d Douglas-fir seedlings to be low (re l a t i v e to a.mmonium-fed seedlings). It appeared that nitra.te-N i n h i b i t e d the translocation of phosphorus to shoots, and seedling growth with nitrate-N ma.y have been reduced f o r t h i s reason. Also, Krajina. (1959) /•10k showed that while Douglas-fir seedlings attained t h e i r best growth with nitrate-N, they developed symptoms suggestive of low P and Ca. absorption. The above workers did not attempt to explain the N - P antagonism. Bengtson and Voigt (1962) , who reported that heavy N f e r t i l i z a t i o n interfered with the uptake of s o i l phosphorus by pine seedlings, observed heavily N - f e r t i l i z e d seedlings to be v i r t u a l l y non-mycorrhizal, a. phenomenon well documented i n the l i t e r a t u r e (see Harley I 9 6 9 ) . Visual observation of roots of seedlings grown i n the high nutrient -high moisture treatments i n t h i s study did suggest that mycotrophy was i n h i b i t e d (Fig. k). The f a c t that P uptake by non-mycorrhizal seedlings was not i n h i b i t e d by the high N treatments of van den Driessche and Dangerfield (1975) i s probably due to the fact that a l l nutrients (including P) were provided i n solution. Cation - anion balance may off e r a. further explanation f o r the N - P antagonism. E l e c t r i c a l n e u t r a l i t y must be maintained across the membrane during nutrient absorption by plant roots (Miller 1971) . B l a i r et a l . (1970) used t h i s f a c t to explain higher P contents i n corn plants grown with an NH^+ source of N than i n those grown with a. N0^~ source. They f e l t greater P uptake with NH^+-N was the r e s u l t of a. stimulated anion uptake (e.g. HgPO^") i n response to high cation (NH^+) absorption. Conversely, /105 FIGURE 4. T y p i c a l mycorrhizal development i n high nutr ient -high moisture treatments TABLE 37 • /106 Nitrogen/phosphorus r a t i o i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Level Relative Nutrient Level 18.551 51.291 72.09| 75-56\ 2 41.171 84.23 87.25 102.88 3 ,60.38 80.40 84.72 94.99 4 67.61 89.08 100.84| 95-55 Averages 46.93 76.25 86.23 92.41 Averages 5^ -371 78.88 80.12 88.431 TABLE 38. Concentration {%) of potassium i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutrient regime (N) and moisture regime (M) Relative Moisture Relative Nutrient Level Averages Level 1 2 3 4 1 0. 308 b C 0.175 o.25of 0.517 0.312J 2 O.392 0.375 o.475| 0.600 0.4601 3 o.325b 0.467 0.6331 0.812 0.5591 4 o.4ooa 0.-700 o.750| 0.917 0.692I Averages p.356 0.429 O.527 0.7II Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /107 N O 3 -N uptake stimulated cat ion (e .g . Ca , Mg ) absorption. In the present study, s o i l so lut ions i n the high nutr ient -high moisture treatments contained high concentrations .of N and S anions ( N O 3 and SO^ , re spect ive ly) and low 2-concentrations of P anions (H|PO/| , HPO^ , e t c . ) . Under these condi t ions , P would be at a competitive disadvantage i n anion absorption. F i n a l l y , and undoubtedly most important, the a v a i l a b i l i t y of s o i l phosphorus i n t h i s study was extremely low, even i n the highest nutr ient treatments. V i r t u a l l y a l l of the phosphorus added at the s tart of the experiment was e f f e c t i v e l y t i e d up i n an insoluble form. Low phosphorus mobi l i ty i n s o i l combined with decreased root biomass i n the higher nutr ient treatments, reduced contact of roots with s o i l phosphorus. /108 3.12 Tissue Potassium The concentration of potassium i n foliage and stems increased s i g n i f i c a n t l y with increased nutrient supply (Tables 38, 39). These r e s u l t s are i n agreement with those reported by Schomaker (1969) f o r white pine seedlings, but contrary to the reduction i n K concentration following nitrogen f e r t i l i z -ation observed by Heilman and Gessel (1963)* McClain and Armson (1976), and Timmer and Stone (1978). The addition of potassium along with nitrogen apparently o f f s e t the d i l u t i o n on f o l i a r K that i s often evident following N f e r t i l i z a t i o n . Contrary to the trend for f o l i a g e and stems, K concentration i n roots generally declined with increased nutrients, although differences were not always s i g n i f i c a n t (Table 40). Data presented i n Table 43 show decreased concentration i n roots to be c l e a r l y the r e s u l t of reduced K content rather than d i l u t i o n . Decreased K content with increased nutrient supply was s i g n i f i c a n t at a l l but the lowest moisture l e v e l . A s i m i l a r r e s u l t was obtained by Ingestad (i960) with pine seedlings, who reported that K concentration increased i n f o l i a g e but decreased i n roots with increased nitrogen supply. The K content of roots i s highly correlated with root weight, e s p e c i a l l y at the higher moisture l e v e l s (r=0.9595 at 4M). However, the f a c t that K content i n foliage and stems continued to r i s e with increased nutrients (Tables /109 TABLE 39' Concentration {%) of potassium i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture Re la t ive Nutr ient Leve l Averages L e v e l 1 2 3 4 1 0.24lf 0.177| 0.267^  0.367 0.263I 2 0.300I 0.283| 0.358| 0.392 0.3331 3 0.267| O.367I 0.417| 0.500 0.387I 4 o.325| 0.492| 0.492| O.525 0.4581 Averages 0.283 0.330 0.383 0.446 TABLE 40. Concentration {%) of potassium i n root s , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Relat ive Moisture Rela t ive Nutr ient Leve l Averages Leve l 1 2 3 4 1 0.275 ab 0 . 1 9 2 | 0.225 0 . 3 0 8 a d 0 . 2 5 0 2 0 . 2 9 2 0 . 2 6 7 0.242 0 . 2 0 8 J 0.252 3 O .3I7 0 . 4 5 0 0.442| cd 0.333 0.3851 4 0.433J 0 . 4 6 7 0.408| 0 .400) 0 . 4 2 7 | p R Averages 0 . 3 2 9 0.344 0 . 3 2 9 0 . 3 1 2 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 / n o 4l, 42) suggests that the a b i l i t y of roots to absorb K was not inh i b i t e d by reduced biomass. This i s undoubtedly large l y due to the high mobility of K ions i n s o i l . Reduced K content i n roots at the higher nutrient l e v e l s may be p a r t i a l l y attributable to e f f i c i e n t translocation of K to shoots i n response to a buildup of c i t r i c acid i n f o l i a g e . The disruption of the Krebs cycle induced by high NO^- supply may increase c i t r i c acid accumulation i n foliage and re s u l t i n a concomitant r i s e i n f o l i a r K. These phenomena are discussed i n d e t a i l i n section 3 '13-Both potassium content and concentration increased s i g n i f i c a n t l y with increased moisture supply. As with, nitrogen, the absence of any d i l u t i o n e f f e c t indicates K was not l i m i t i n g growth. Seedlings i n a l l but the lowest nutrient and moisture treatments had f o l i a r K concentrations above generally recognized deficiency l e v e l s (Ballard 1980b). On the average, 40$, 15 .7$, and 44.3$ of the t o t a l potassium per seedling was contained i n the fo l i a g e , stems, and roots, respectively. However, the r e l a t i v e proportions were shifted heavily towards roots i n the lower nutrient regimes and towards foliage i n the higher nutrient regimes. While the concentration of potassium i n foliage i s generally above the suggested deficiency l e v e l f o r Douglas-fir i / i l l TABLE 41. Weight (mg) of potassium per seedl ing i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture Leve l Re la t ive Nutr ient Leve l 1 2 3 4 1 0.094| 0.079 0.130| 0.213 2 0.177 0.131 0.188| 0.264 3 0.199 0.272| O.367I O.357 0.264} 0 . 3 8 5 ; 0.4551 0.396: 0 . i « 3 0 .217 0 . 2 8 5 0 . 3 0 7 Averages 0.129| 0.190| 0.299! 0.3751 Averages TABLE 42. Weight (mg) of potassium per seedl ing i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture L e v e l Re la t ive Nutr ient Leve l 0.035] 0.031} 0.055} 0.073 Averages 0.048J 2 0.059 0.063| 0.088} 0.117 0.082} 3 0.064 0.104| 0.1271 0.147 o . n o j 4 O.O87 0.1471 0.161| 0.188 0.146} Averages 0.061 0.086 0.108 0.131 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /112 TABLE 43. Weight (mg) of potassium per seedl ing i n roots , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive 3 4 0.381| 0.472| 0.429J 0.233  0.4591 0.3751 0.3181 0.276 0.316 07Z93 OTZEE 0.196 Moisture Rela t ive Nutr ient Leve l Averages L e v e l 1 2 3 4 1 0.158J 0.119| 0.137 0.142 0.138| 2 0.264| 0.207| 0.177 0.139 0.1971 0.380 0.357 Averages TABLE 44. T o t a l weight (mg) of potassium per seedl ing , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Rela t ive Nutr ient Leve l Averages L e v e l 1 . 2 3 4 1 -0.287?' 0.229| o.323f 0.423 0.3151 2 O.500P 0.401| 1' h 0.4531 0.520 0.4691 3 0.644P 0.848 i 0.925 cd 0.7371 0.789! 4 0.809| 0.907 0.934 0.8591 0.8771 Averages 0.560 . O.596 O.659 O.635 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /113 the proportion of K r e l a t i v e to N i s much lower than that reported to be favorable by Ingestad (1967). /Ilk 3*13 Tissue Calcium The concentration and content of calcium i n fo l iage and roots decreased s i g n i f i c a n t l y with increased nutr ient supply at a l l "but the lowest moisture l e v e l (Tables 45, 47, 48, 50)' These concentration data are s imi l a r to the d i l u t i o n i n f o l i a r Ca-concentration fo l lowing nutr ient addit ions reported i n the l i t e r a t u r e (Schomaker 1969; McClain and Armson 1976; Timmer and Stone 1978). However, the decrease i n Ca uptake at the higher nutr ient l eve l s i n t h i s study i s not consistent with past work. The f a i r l y strong negative corre la t ions "between f o l i a r Ca and K content and "between f o l i a r Ca and s o i l NO3 -N at higher moisture l e v e l s (r=-0.7776 and r=-0.8642 at 4M, respect ive ly) suggest an antagonism between Ca and both K and NO3. These phenomena may be at least p a r t i a l l y explained by the evidence of , and mechanisms involved i n , ' i r o n c h l o r o s i s ' , as reported i n the l i t e r a t u r e . There have been many instances where i t has been demonstrated that c h l o r o t i c fo l iage contains more potassium and less calcium than healthy fo l iage (Lindner and Harley 1944; I l g i n 1952; Machold and Grober 1966; Zech 1969> 1970)' In many cases, ch loros i s has been a l l ev i a ted by applying i ron to fo l iage and/or roots , even though c h l o r o t i c fo l iage may contain as much, (or more) t o t a l i ron as healthy fo l iage (Oserkowsky 1933; / H 5 TABLE 45- C o n c e n t r a t i o n {%) o f c a l c i u m i n f o l i a g e , i n r e l a t i o n t o r e l a t i v e n u t r i e n t r e g i m e (N) and m o i s t u r e r e g i m e (M) R e l a t i v e A v e r a g e s 0.1b4 0.125 0.TT5 -0.112 M o i s t u r e R e l a t i v e N u t r i e n t L e v e l A v e r a g e s L e v e l 1 2 3 4 1 0.093] 0 . 0 9 5 A 0.095 0.109 0.098| 2 0.1301 0.125s 0.116 0.089 0.115I 3 0.225 0.165] 0.137 0.123 b 0.162| 4 0.209 o.H5a 0 .111 O . I27 b 0.140| TABLE 46. C o n c e n t r a t i o n {%)' o f c a l c i u m i n s t e m s , i n r e l a t i o n t o r e l a t i v e n u t r i e n t r e g i m e (N) and mois-t u r e r e g i m e (M) R e l a t i v e M o i s t u r e L e v e l 1 2 3 , 4 R e l a t i v e N u t r i e n t L e v e l L 2 3 "4 7b tr A v e r a g e s 0.088| 0.112| 0.110 0.081| 0.0971 0.129J 0.151 0.119 0.0931 O.123I 0.188 0.167 0.159 0.151| 0.1661 0.175 a 0.183 0.162 a 0.2051 0.1811 A v e r a g e s 0.145 0.153 O . I37 O . I32 Means c o n n e c t e d b y t h e same l i n e do n o t d i f f e r s i g n i f i c a n t l y f r o m e a c h o t h e r a t p=0.05 Means m a r k e d w i t h t h e same l e t t e r do n o t d i f f e r s i g n i f i c a n t l y f r o m e a c h o t h e r a t p-0.05 /116 TABLE 47. Concentration {%) of calcium i n roots , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture L e v e l 1 2 3 4 Rela t ive Nutr ient Leve l  1 2 3 _4_ 0.173 0.0991 Q.Q971 0.Q97I Averages 0.169 0.155 0.160 0.153 0.159° 0.174 • 0.144 0.133 0.142 0.148 0.2251 0.181| 0.148 0.132 0.171° 0.117| Averages 0.I85 0.145 0.134 0.131 TABLE 48. Weight (mg) of calcium per seedl ing i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Rela t ive Nutr ient Leve l Averages L e v e l 1 2 _3_ _4_ . 1 0 . 0 2 9 0 . 0 4 3 a . 0 . 0 4 9 0 . 0 4 4 0 . 0 4 1 2 0 . 0 5 9 o . 0 5 6 a 0.046 0 . 0 4 0 0 . 0 5 0 3 0.1.38 0.098I 0 . 080 0 . 0 5 5 0 . 0 9 3 ! 4 0 . 1 3 8 0 . 0 6 3 a 0 . 0 6 8 0 . 0 5 5 0.081I Averages 0.091 0.065 0.061 0.048 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /II7 TABLE 49. Weight (mg) of calcium per seedl ing i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Leve l 1 2 3 4 Rela t ive Nutr ient Leve l o . o i 3 a o . Q 2 o a 0 . 0 2 3  0.024[ Q-.Q33J 0 . 0 2 9 0.016^ 0.0281 0 . 0 4 5 0 . 0 4 8 0 . 0 4 5 0.044[ 0 . 0 4 7 b 0 . 0 5 5 0 . 0 5 3 0.074| Averages 0.018| 0.0291 0.0451 0.0571 Averages O .032 0 . 0 3 9 O .037 0.040 TABLE 5 0 . Weight (mg) of calcium per seedl ing i n roots , i n r e l a t i o n to r e l a t i v e nutr ient regime (N)' and mois-ture regime (M) Rela t ive Moisture Rela t ive Nutr ient Leve l Averages Leve l 1 2 3 4  1 0 . 0 9 9 ! 0 . 0 9 6 0 .096° 0 . 0 6 9 ,d 0.0901 2 0 . 1 5 8 a h 0.112 0 . 0 9 7 ° 0 . 0 9 5 0 . 1 l 6 |e 3 0 . 2 4 9 | 0 . 1 9 l | 0.145| 0 . 0 9 3 0.169) 4 0 . 1 8 5 a b 0.080 0 . 0 7 5 ° 0 . 0 6 7 de 0 . 1 0 2 Averages 0 . I 7 3 0 . 1 2 0 0 . 1 0 3 0.081 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 / I I 8 Lindner and Harley 1944; Machold 1966). This has led to the "belief that only a small portion of t o t a l f o l i a r iron i s 'physiologically active'. Ferrous ( F e 2 + ) iron i s considered to be the 'active' form i n plants, i t s presence essential for the a c t i v a t i o n of the enzyme(s) required to catalyze the reactions involved i n chlorophyll synthesis (Salisbury and Ross 1969). Many workers, using a variety of extraction techniques, have shown c h l o r o t i c foliage to contain less 'active' iron than green foliage (Oserkowsky 1933; Lindner and Harley 1944; Zech 1970). Iron also appears to influence the functioning of the c i t r i c acid ( i . e . Krebs) cycle. Chlorotic, i r o n -d e f i c i e n t foliage has been shown to contain large amounts of c i t r i c acid r e l a t i v e to green foliage (McGeorge 1949; I l g i n 1951; DeKock and Morrison 1958). It i s thought that a deficiency of p h y s i o l o g i c a l l y active iron i n h i b i t s the conversion of c i t r i c acid to malic acid, r e s u l t i n g i n a buildup of the former. The enzyme known to catalyze t h i s conversion has been shown to be less active i n i r o n - d e f i c i e n t plants (Bacon et a l . 1961). The r a t i o s of c i t r i c acid to malic acid and of potassium to calcium are assumed to be linked metabolically (Palmer et a l . 1963)> perhaps because of calcium association with oxalate produced i n the g l y o x y l i c acid cycle, following malic acid synthesis. Foliage with high calcium content has A 1 9 been shown to contain large•amounts of malic acid (McGeorge 1°4Q; H g i n 1951; Palmer et a l . 1963; DeKock 1964). Conversely, i ron^def ic ient fo l iage with high l eve l s of c i t r i c acid i s often low i n calcium and high i n potassium. A r i s e i n the c i t r i c ac id/mal ic acid r a t i o i n i r o n - d e f i c i e n t fo l iage i s therefore general ly accompanied by a r i s e i n K/Ca r a t i o . The oxidat ion of i ron from the ferrous (Fe^ +) to the f e r r i c (Fe^ +) form would lower the amount of p h y s i o l o g i c a l l y active i r o n . Reduced ch lorophy l l synthesis , c i t r i c acid bui ldup, probable decrease i n f o l i a r calcium content, and increase i n f o l i a r potassium content would be the r e s u l t . Zech (1970) suggested that high NO-^-N uptake by plants may induce the high oxidat ion - reduction p o t e n t i a l necessary to inact ivate the i r o n . He c i ted research by Machold (1967) which showed that culture solut ions with n i t r a t e as a nitrogen source produced chloros i s i n tomato p lant s . S h i f t i n g to an ammonium source increased the ch lorophy l l content of the plants wi th in a few days. Since i r o n content of the leaves of c h l o r o t i c and green plants was the same, Machold concluded that NO3 -N increased the redox p o t e n t i a l of the p lants , thereby causing a def ic iency of ferrous (Fe^_+) i ron and a resul tant block i n ch lorophyl l formation. The fact that NO^'-N caused symptoms of i ron ch loros i s i n b lueberr ies (Cain 1952) lends support to t h i s /120 theory. Nelson and Selby (1974) showed that seedlings supplied with NO-^-N developed ch l o r o t i c foliage containing high l e v e l s of organic acids. The addition of iron to the culture solution decreased organic acid accumulation i n seedling t i s s u e , i n d i c a t i n g that a lack of iron may have been at least p a r t i a l l y responsible for the organic acid accumulation. They cited the competitive chelation hypothesis proposed by Wallace (1971) as a possible explanation for the iron chlorosis induced by NO-^ '-N. This theory suggests means by which various chelates can e f f e c t i v e l y t i e up iron i n fo l i a g e , thereby reducing i t s a c t i v i t y . Nelson and Selby f e l t a sim i l a r effect might occur when organic acid concentrations are increased i n fo l i a g e . However, for the theory to have v a l i d i t y i n t h i s case, NO3 -N must be the dir e c t cause of organic acid accumulation, i n turn causing iron chlorosis. This i s dif f e r e n t from the mechanism proposed by Zech (1970) and Machold (1967), which assumes that N0^~-N reduces iron a c t i v i t y , thereby causing accumulation of organic acids. Whether organic acid accumulation i s the cause or the e f f e c t of reduced iron a c t i v i t y r e s u l t i n g from NO-^ '-N uptake i s obviously the subject of debate. Regardless, the apparent e f f e c t of decreased calcium content and increased potassium content i n foliage supplied with N0-^ ~-N may /121 p a r t i a l l y explain re su l t s i n the present study. The good pos i t ive corre la t ions between f o l i a r K and s o i l NO-^- and between f o l i a r K/Ca and s o i l NO^ - at the high moisture l e v e l s (r=0.Q15^ for both at 3M) lends support to t h i s hypothesis . As discussed i n sect ion 3«12, low K content i n seedling roots may have been the re su l t of e f f i c i e n t t r ans loca t ion of K from roots to shoots i n response to a c i t r i c acid buildup i n fo l iage caused by n i t r a t e - n i t r o g e n . Concentration and content of calcium i n fo l iage and roots increased s i g n i f i c a n t l y with increased moisture, except at the highest moisture l e v e l where concentration and content were reduced (Tables 45, 47, 48, 5°)' Other than the decrease i n Ca uptake at high moisture, the re su l t s were' i n agreement with those obtained by McClain and Armson (1976) with white spruce seedl ings . The decreased root biomass characterized by the highest moisture l e v e l appeared to affect the uptake of calcium more adversely than the uptake of N, P, or K. The concentration and content of calcium i n stems were s i m i l a r to those i n fo l iage and roots , although l eve l s did not decrease"in the highest moisture treatments (Tables 45, 49). The def ic iency l e v e l for calcium i n Douglas- f i r fo l iage has not been determined, but values obtained i n t h i s study were low compared to those general ly reported (van den /122 TABLE 51« T o t a l weight (mg) of calcium per seedl ing , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Re la t ive Nutr ient Leve l Averages L e v e l 1 2 3 4 1 0 . l 4 l | 0.159a 0.168? 0 . 129 0.149| 2 0.2411 0 . 2 0 i a 0.172 0 . I 6 3 0.1951 3 0.432] 0.3371 O.27OJ 0 . 192 0 . 3 0 8 ! 4 0.369! 0 . l 9 8 a D 0 . 1 9 6 0 . 1 9 6 0.24o| Averages O .296 0.224 0 . 2 0 2 0 . I 7 0 TABLE 52. Concentration {%) of magnesium i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Relat ive Moisture Rela t ive Nutr ient Leve l Average L e v e l 1 2 3 4 1 0 . 0 5 3 o . o 5 o a 0 . 0 5 4 c 0.081 0 . 0 5 9 2 0 . 0 4 4 0 . 0 6 l b 0 . 0 6 4 c 0.081 0 . 0 6 2 3 0.. 091 A. 0.072I 0 . 0 7 3 0.089 d 0.0811 4 0 . 0 8 9 e ab 0 . 0 5 3 0 . 0 5 7 c 0.082 e 0 . 0 7 0 | Averages 0 . 0 6 9 0 . 0 5 9 0.062 0 .083 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /123 Driessche 1969a). Seedlings i n many of the treatments had f o l i a r Ca concentrations comparable to Douglas- f i r seedlings i n another study which l a t e r responded s i g n i f i c a n t l y to l iming (Heilman and Ekuan 1973)' A l so , the proportion of Ca r e l a t i v e to the concentration of N i n fo l iage was general ly much lower than that proposed by Ingestad (1967). On the average, 29.3%. 17-3%, and 53-4% of t o t a l seedl ing calcium was contained i n the f o l i a g e , stems, and roots r e spec t ive ly . 1 /12k <? 3 -14 Tissue Magnesium The effect of nutr ient s and moisture on the content and concentration of magnesium i n seedlings var ied considerably with the type of t i s sue . In fo l iage and root s , concentration and content of magnesium general ly decreased with nutr ient supply at the higher moisture l eve l s (Tables 52, 5^ , 55» 57) > These re su l t s are s i m i l a r to those obtained with calcium, which suggests s i m i l a r mechanisms may be involved i n the uptake of these two elements. The strong pos i t ive c o r r e l a t i o n between uptake of Ca and Mg (r=0.8635) lends support to t h i s theory. The concentration and content of magnesium i n stems (Tables 53» 56) genera l ly increased s i g n i f i c a n t l y with increased nutr ient supply. As with calcium, concentration and content of magnesium i n fo l iage and stems general ly increased with moisture l e v e l , except at the highest moisture treatment. However, unl ike calcium, the concentration of magnesium i n roots cons i s tent ly decreased with moisture supply, except at the lowest nutr ient l e v e l . This was general ly a d i l u t i o n e f f ec t , although there was a large reduction in-magnesium uptake at the highest moisture l e v e l . The decreased uptake at the highest moisture l e v e l was associated with a large decrease i n root biomass. However, the data suggest that /125 TABLE 53. Concentration {%) of magnesium i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture L e v e l Re la t ive Nutr ient Leve l 1 0.039 0 . 0 3 5 I o.o4o| 0 . . 0 5 0 I 2 0.038 0.049 0.054 0.058' 3 0.056 0.056 0.062 0.066 4 0.057 0.055 O.060 0.060 Averages 0. 04ll 0.050J 0.060 O.058 A v e r a g e s 0 . 0 4 8 0 . 0 4 9 0 . 0 5 4 0 . 0 5 9 TABLE 5^• Concentration (%) of magnesium i n roots , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Leve l Rela t ive Nutr ient Leve l 1 0.094 0.0751 o.072 a 0.073I 2 '0.083 O.057 O.056 0.055 3 0.082 0.065 0.059 A 0 . 0 5 0 k 0.090 0.0491 0.047 0.043 Averages O.U87 0.061 u.U5y U .U55 Averages 0.0791 0.063 0.064 0.057 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p-0.05 /126 TABLE 55' Weight (mg) of magnesium per seedl ing i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture Re la t ive Nutr ient Leve l Averages Leve l 1 2 3 4 1 0.016 0.022a 0.028 b 0.033 0.025 2 0.020 0.027s b 0.025 0.036 0.027 3 0.055 o.o4-3| 0.043 0.040 o.o45| 4 o. 059 0.029a 0.035 b 0.035 0.040| Averages 0.03b0.030 O.033 0.03T TABLE 56. Weight (mg) of magnesium per seedl ing i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Leve l 1 2 3 4 Relat ive Nutr ient Leve l 0.005 J)jJ)06] 0.008| 0,010 Averages 0.007J 0. 008 0.011 0.013 0.017 0.012] 0.013 0.016 0.019 0.020 0.017 0.015 0.016 0. 020 0.021 0.018 Averages 0.010 0.012 0.015 0.017 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 1 /127 TABLE 57. Weight (mg) of magnesium per seedl ing i n roots , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Re la t ive Moisture Rela t ive Nutr ient L e v e l L e v e l 1 1 0.055 2 3 4 0 .o46 b 0.043° 0.033 ? 0.075 a 0.044b 0 . 0 4 1 ° O.037 q 0.099 0.068| 0.057| 0.035 u 0.094 a o.039b 0.037° 0.029 Averages 0.044 0.049d 0.065J d 0.050 Averages 0 .081 0.049 0.045 O.033 TABLE 58. T o t a l weight (mg) of magnesium per seedl ing , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Rela t ive Nutr ient Leve l Averages Leve l 1 2 3 4 1 0.076J 0.074a 0.079b 0.076 O.O76I 2 0.103| 0 . 0 8 2 a 0.079b 0.090 O.O89I 3 O.I67 0.127| 0.U9I 0.095 0.127| 4 0.168 0 . 0 8 4 a ,0.092b 0.085 0.1081 Averages 0.129 O.092 O.092 0.086 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 /128 magnesium (and calcium) uptake i s affected more adversely by a reduction i n root weight than i s the uptake of other nut-r i e n t s . F o l i a r magnesium concentration i s usua l ly s l i g h t l y below the general ly recognized def ic iency l e v e l for Douglas- f i r (see Ba l l a rd 1980b). However, good information on the magnes-ium n u t r i t i o n of Douglas- f i r i s l a ck ing . The proport ion of magnesium r e l a t i v e to n i t rogen i n f o l i a g e , however, i s much lower than that proposed by Ingestad (I967). A 29 3.15 T i s s u e Manganese The c o n c e n t r a t i o n o f manganese i n f o l i a g e , s t e m s , and r o o t s g e n e r a l l y i n c r e a s e d s i g n i f i c a n t l y w i t h i n c r e a s e d m o i s t u r e s u p p l y ( T a b l e s 59» 60, 6l). T h e s e r e s u l t s a r e c o n t r a r y t o t h o s e o b t a i n e d b y Sc h o m a k e r (1969), who r e p o r t e d t h a t Mn c o n c e n t r a t i o n g e n e r a l l y d e c r e a s e d i n f o l i a g e w i t h an i n c r e a s e i n t h e f r e q u e n c y o f i r r i g a t i o n . I n t h e p r e s e n t s t u d y , any t e n d e n c y f o r t i s s u e Mn c o n c e n t r a t i o n t o be d i l u t e d a t t h e h i g h e r m o i s t u r e l e v e l s was a p p a r e n t l y more t h a n o f f s e t b y i n c r e a s e d s o i l manganese s o l u b i l i t y . U n d e r c o n d i t i o n s o f l o w pH and p o o r a e r a t i o n ( i . e . t h e c o n d i t i o n s p r e v a l e n t i n t h e h i g h e r m o i s t u r e r e g i m e s o f t h i s s t u d y ) , i n s o l u b l e m a n g a n i c manganese compounds a r e r e d u c e d t o s o l u b l e manganous ( M n 2 + ) f o r m s w h i c h a r e r e a d i l y a v a i l a b l e t o p l a n t s ( R u s s e l l 1973)• The s t r o n g n e g a t i v e c o r r e l a t i o n b e t w e e n pH and f o l i a r Mn c o n c e n t r a t i o n (r=-0.8833) i s e v i d e n c e o f t h i s f a c t . The c o n c e n t r a t i o n o f manganese i n f o l i a g e , s t e m s , and r o o t s g e n e r a l l y i n c r e a s e d and d e c r e a s e d w i t h s o i l n u t r i e n t s u p p l y i n t h e h i g h and l o w m o i s t u r e t r e a t m e n t s , r e s p e c t i v e l y . A t t h e h i g h m o i s t u r e l e v e l s , t h e p l e n t i f u l s u p p l y o f manganese e n a b l e d i t s c o n t i n u e d u p t a k e e v e n t h o u g h t h e g r o w t h o f s e e d l i n g s was d e c r e a s e d w i t h i n c r e a s e d n u t r i e n t s . A t t h e l o w e r m o i s t u r e l e v e l s , manganese a v a i l a b i l i t y was l o w , and r e d u c e d Mn c o n c e n t r a t i o n w i t h i n c r e a s e d n u t r i e n t s a t A 30 TABLE 59. Concentration (ppm) of manganese i n f o l i a g e , i n r e l a t i o n to r e l a t i v e nutr ient regime' (N) and moisture regime (M) Re la t ive Moisture Re la t ive Nutrient Leve l Averages L e v e l 1 2 3 4 1 73 72 48 58 63l 2 75 70 77 73 74|' 3 87 I63 165 158| 143| 4 133) 158 I63 184] 1601 Averages 92 116 113 118 TABLE 60. Concentration (ppm) of manganese i n stems, i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Rela t ive Moisture Rela t ive Nutr ient L e v e l Averages Leve l 1 2 3 4 1 32I a. 42| 20P 19 a. 28| 2 37 60 37P 30 4l| 3 28 100 100J 95 81| 4 38 108 107| 93 87! Averages 34 78 66 59 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 TABLE 61. A 3 1 Concentration (ppm) of manganese i n roots , i n r e l a t i o n to r e l a t i v e nutr ient regime (N) and moisture regime (M) Relat ive Moisture Averages Relat ive Nutrient Level 52 72 77 Leve l 1 2 _ 1 4 1 65 55 62 47| 2 62 55 63 59a 3 42 90 98 92) 4 40 90 83 67a "57" Averages 57 60 80 71 Means connected by the same l i n e do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 Means marked with the same l e t t e r do not d i f f e r s i g n i f i c a n t l y from each other at p=0.05 A 32 2N and 3N i s probably p r i m a r i l y due to d i l u t i o n . However, reduced uptake at 4N i s undoubtedly the re su l t of decreased seedl ing growth. Although manganese def ic iency l e v e l s i n Douglas- f i r have not been i d e n t i f i e d , f o l i a r Mn concentrations were much higher than def ic iency l eve l s suggested for Norway spruce (Ingestad 1958). A l s o , work undertaken by Radwan et a l . (1979) suggests Douglas- f i r can to lera te extremely high concentrations of f o l i a r manganese. A 33 CHAPTER 4 RESULTS AND DISCUSSION: CORRELATIONS INVOLVING OTHER  RELATIONSHIPS BETWEEN VARIABLES 4.1 Introduction Many workers have sought corre la t ions between t i s sue nutr ient and s o i l nutr ient contents, and between these parameters and various ind ica tor s of growth. Success i n these endeavours would go a long way toward improving the diagnost ic and pred ic t ive usefulness of s o i l and f o l i a r analys i s techniques. The fact that these attempts have so often met with such l imi ted success i s undoubtedly l a rge ly due to s o i l moisture v a r i a b i l i t y . In t h i s study, corre la t ions were undertaken within s p e c i f i c moisture treatments i n an attempt to improve the strength of corre la t ions between cer ta in parameters. A 3k k.2 F o l i a r Nutrients versus Seedling Weight F o l i a r P, Ca., and Mg contents were general ly p o s i t i v e l y corre lated with mean seedl ing weight (Table 62 ) . Corre la t ions were strongest i n those treatments where s o i l moisture was not a. growth-l imit ing f ac to r . These strong pos i t ive corre la t ions are further evidence that seedling growth was l a r g e l y contro l l ed by those elements i n de f i c i en t supply. The general lack of strong pos i t i ve cor re la t ions of f o l i a r ni trogen and potassium with seedl ing weight suggests supplies of these nutr ients were a.dequa.te. Instances where N and K corre la t ions were negative probably indicate luxury consumption of these nut r i en t s . C O TABLE 62. C o r r e l a t i o n s b e t w e e n mean s e e d l i n g w e i g h t and f o l i a r n u t r i e n t c o n c e n t r a t i o n s and c o n t e n t s C o r r e l a t i o n C o e f f i c i e n t s ( r ) M o i s t u r e L e v e l S e e d l i n g W e i g h t 11 n 11 11 1 A l l x 1M 2 2 2M 2 3M 4M2 foN i n F o l i a g e 0.1097 0.2391 -0.5517 -0.7292 -0.4439 W e i g h t o f N i n F o l i a g e 0.5983 O.5I67 -O . I363 O.39IO 0.5052 foP i n F o l i a g e 0.5322 -0.7893 0.2929 0.1852 0.4130 W e i g h t o f P i n F o l i a g e 0.5955 0.0857 0.8615 0.9404 0.9366 $K i n F o l i a g e 0.0838 -0.5031 -0.5223 -0.8525 -0.8460 W e i g h t o f K i n F o l i a g e 0.4338 -O.138O -O.2556 -0.4956 -0.4312 $Mg i n F o l i a g e 0.3644 -0.3283 -0.5109 0.0266 O.2328 W e i g h t o f Mg i n F o l i a g e 0.7875 0.3214 -0.0445 0.7955 0.7795 $ C a i n F o l i a g e 0.7541 0.0284 O.3766 0.7283 0.5749 W e i g h t o f Ca i n F o l i a g e 0.8729 O.7039 0.7530 0.8669 0.8188 o f c o r r e l a t i o n n 11 c o e f f i c i e n t 11 ( r ) a t 11 P P =0.05 i s =0.01 i s 0.2845 0.3683 o f c o r r e l a t i o n 11 11 c o e f f i c i e n t ( r ) a t it P P =0.05 i s =0.01 i s O.5760 0.7079 /136 4.3 S o i l Nutrient A v a i l a b i l i t y versus Seedling Weight Most of the s o i l nutr ient s measured were negat ively corre lated with mean seedl ing weight (Table 63)1 suggesting that supplies of these nutr ient s were adequate for seedl ing growth. The negative corre la t ions were strongest at the higher moisture l eve l s where s o i l nutr ient a v a i l a b i l i t y was greatest . In the case of extractable phosphorus, however, the concentration i n s o i l was so low as to preclude c o r r e l -a t ion . TABLE 63. Corre la t ions between mean seedling weight and s o i l nutr ients Corre la t ion Coef f ic ients (r) Moisture Level A l l 1 1M 2 2M 2 3M2 4M2 Seedling Weight: Extractable NO^" O.O983 0.4473 -O.7372 -0.73^ 7 -0.73 : Exchangeable N H ^ + -O.5365 0.1039 -O.3853 -O.738O -O.35 : Exchangeable K + -O.3832 0,0098 -0.4407 -0.8060 -0.70 : Exchangeable Mg 2 + -O.4598 -0.2032 -0.2234 -0.8559 -0.60 I Exchangeable C a 2 + -0.5201 -0.0162 -0.34o6 -0.8557 -0.59 1 C r i t i c a l value of c o r r e l a t i o n coe f f i c ient (r) at p=0.05 i s 0.2845 " p=0.01 i s O.3683 11 11 2 C r i t i c a l value of c o r r e l a t i o n coe f f i c ient (r) at p=0.05 i s O.576O " p=0.01 i s O.7079 H 11 A 38 4.4 So i l - Nutrients versus F o l i a r Nutr ients Strong pos i t ive corre la t ions were obtained between exchangeable s o i l potassium and f o l i a r potassium concentration and content (Table 64) . Corre la t ions were strongest at the higher moisture l eve l s where K uptake would not be impeded by lack of s o i l moisture. These re su l t s are s imi l a r to those of Walker (1955)i who reported good c o r r e l a t i o n between s o i l K and f o l i a r K concentration i n white pine. Strong pos i t ive corre la t ions were also obtained between f o l i a r ni trogen concentration and both s o i l NH^ -N and NO-^~-N. Corre la t ions were strongest at those moisture l e v e l s where s o i l concentrations of ammonium and n i t r a t e were highest ( i . e . low moisture for N H ^ - N and high moisture for N0 3 " - N ) . Exchangeable s o i l calcium tended to be negat ively correlated with f o l i a r calcium content and concentrat ion. The negative corre la t ions were strongest at the higher moisture l e v e l s . These r e su l t s can probably be explained by the re l a t ionsh ip s between Ca, K, and N discussed i n Sect ion 3.13. TABLE 64. Corre la t ions between s o i l nutr ients and f o l i a r nutr ients ON cn T-i \ Corre la t ion Coef f ic ients (r) Moisture Level 1 A l l x 2 1M 2 2M 2 3M 4M2 Extractable N0^~: %N i n Fol iage 0.6660 0.9308 0.9023 0.9311 0.8408 : Weight of N i n Fol iage O.5003 0.9646 0.67-54 0.2143 -0.0099 Exchangeable NH^"1": %N i n Fol iage 0.4079 0.9807 0.9H2 0.8461 0.5885 : Weight of N i n Fol iage 0.0125 0.8669 0.8101 0.0308 -O.0550 Exchangeable K + : %K i n Fol iage 0.5500 0.7083 0.7758 O.9562 0.9220 : Weight of K i n Fol iage 0.3378 0.8749 0.649-6 O.8055 0.6827 Exchangeable M g 2 + : %Mg i n Fol iage 0.3975 0.9266 0.9235 O.2297 0.2089 : Weight of Mg i n Foliage -0.0400 0.7921 0.9348 -0.5595 -0.3510 Exchangeable C a 2 + : %Ca i n Fol iage -0.4886 0.5413 -0.9109 -0.7691 -0.5046 : Weight of Ca i n Foliage -0.4887 0.7418 -0.6747 -0.8532 -0.6429 1 C r i t i c a l value of c o r r e l a t i o n coe f f i c ient it II H II II (r) at p; " • P: =0.05 i s =0.01 i s 0.2845 0.3683 2 C r i t i c a l value of c o r r e l a t i o n coe f f i c ient H II H n II (r) at p " P =0.05 i s =0.01 i s 0.5760 0.7079 /140 CHAPTER 5 CONCLUSIONS S o i l and t i s sue parameters general ly displayed h ighly s i g n i f i c a n t di f ferences due to both nutr ient s and moisture. The magnitude of dif ference and the d i r e c t i o n of change var ied depending on the p a r t i c u l a r moisture and nutr ient treatment ( i . e . Nx-M interac t ions were genera l ly h ighly s i g n i f i c a n t ) and the parameter i n question. With t i s sue nutr ient l e v e l s , d i f ferences also varied with type of t i s sue ( i . e . f o l i a g e , stems, or roo t s ) , and whether the l e v e l of the p a r t i c u l a r nutr ient was expressed as concentration or content. These \-\ r e su l t s demonstrate the separate and combined effects of nutr ient s and moisture on s o i l nutr ient a v a i l a b i l i t y , seedl ing growth, nutr ient uptake, and t i s sue nutr ient concentrat ion. While many factors preclude d i r e c t extrapolat ion of greenhouse pot t r i a l r e su l t s to f i e l d condi t ions , some speculations regarding the p r a c t i c a l s igni f icance of exper-imental r e su l t s may be worthwhile. 1. S o i l moisture may have a strong i n d i r e c t influence on the amount of ava i lab le s o i l n i t rogen as we l l as the form i n which i t i s taken up by seedl ings . The form of N may not only inf luence seedling growth response (as suggested by other workers), but may also influence the uptake of other e s s en t i a l nutr ient s (e .g . P and Ca). /141 2. Higher s i t e productivity often evident on "seepage s i t e s ' might often be l a r g e l y due to the favorable influence of s o i l moisture on nutrient a v a i l a b i l i t y and uptake rather than increased amounts of nutrients supplied i n the seepage water. 3. Increased s o i l nutrient supply generally has a strong negative influence on mean seedling root weight and root/ shoot r a t i o . Also, s o i l moisture and nutrients generally have favorable and unfavorable e f f e c t s , respectively, on seedling mycorrhizae. These re s u l t s may have p r a c t i c a l application i n the forest nursery production of conifer seedlings. 4. F e r t i l i z a t i o n of dry s i t e s may be b e n e f i c i a l up to a point, due to improved water use e f f i c i e n c y of conifer seedlings. However, extremely heavy f e r t i l i z a t i o n of droughty s i t e s may be deleterious to the growth of seedlings, since water uptake i s reduced at low s o i l osmotic p o t e n t i a l . 5. Heavy nitrogen f e r t i l i z a t i o n may upset d e l i c a t e nutrient balances within seedlings, r e s u l t i n g in induced nutrient d e f i c i e n c i e s and reduced seedling growth. While decreases i n nutr ient uptake i n t h i s study may be p a r t i a l l y a t t r i b -utable to growth reduct ion , d i r e c t antagonisms between s p e c i f i c nutr ients (e.g. N and P; K and Ca) were also dem-onstrated . 6. The diagnost ic usefulness of f o l i a r analys i s i s g rea t ly affected by s o i l moisture regime. For example, i n severely n u t r i e n t - d e f i c i e n t seedl ings , f o l i a r concentrations of l i m -i t i n g and n o n - l i m i t i n g nutr ients genera l ly decrease and increase , r e s p e c t i v e l y , with increased s o i l moisture. Under condit ions of severe moisture s t ress , therefore , f o l i a r con-centrat ions may p a r t i a l l y mask severe nutr ient d e f i c i e n c i e s . Only when the growth- l imit ing effect of s o i l moisture i s a l l e v i a t e d do f o l i a r concentrations of the l i m i t i n g nutr ient ( s f a l l to severe def ic iency l e v e l s , even though the uptake of the d e f i c i e n t nutr ient ( s ) ma.y ac tua l ly be increased. These r e s u l t s suggest a. c loser examination of the moisture-supply-ing a b i l i t y of a. s i t e may be warranted when evaluating- the r e s u l t s of f o l i a r ana lys i s . C r i t i c a l f o l i a r concentrations of some nutr ients may i n fact vary depending on s i t e moisture cond i t ion . 7. Highly s i g n i f i c a n t p o s i t i v e correla.tions between f o l i a r nutr ient content and seedl ing growth can only be expected for those nutr ients which are inadequately suppl ied . Corr-e la t ions are genera l ly strongest i n those treatments where soi moisture i s not a growth- l imit ing f ac tor . /143 8. Significa.nt pos i t ive corre la t ions between ava i lable s o i l nutr ient supply and seedl ing growth can only be expected for those nutr ients which are inadequately suppl ied . In the case of ava i lab le phosphorus, however, the range of concentrations may be so low as to preclude c o r r e l a t i o n . 9- By removing the v a r i a t i o n caused by s o i l moisture i t i s poss ib le to obtain h ighly s i g n i f i c a n t cor re la t ions between c e r t a i n s o i l and f o l i a r nu t r i en t s . 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Dec. 1973' APPENDIX 1 S o i l analysis p r i o r nutrient additions A p p e n d i x 1 -3" 1 1 1 1 1 2 2 2 2 3 3 4 ^ K C a 1 Mg Na CEC Mn Zn Cu Fe N H ^ N O ^ P ^ meq/lOOg ppm 0.06 0.09 0.02 0.04 14 .0 0.46 O.32 0.38 38.60 3.31 0.60 0.66 T o t a l T o t a l • O r g a n i c pH Sand S i l t C l a y C o a r s e C ' !N M a t t e r F r a c t i o n % _ _ _ _ _ _ % 2.6 0.10 4.45 5.1 77 18 5 28 1 E x t r a c t e d w i t h 1.ON K C 1 , N a C l 2 DTPA e x t r a c t a b l e ( L i n d s a y and N o r v e l l 1978) 3 KC1 e x t r a c t a b l e 4 E x t r a c t e d w i t h 0.5M H 2 C 0 „ ( O l s e n and Dean 1965) 5 L e c o C a r b o n 6 K j e l d a h l N i t r o g e n 7 L e c o C x 1.724 8 1:2 S o i l i H - g O 9 H y d r o m e t e r m ethod (Day 1965) Y l 65 APPENDIX 2 Water retention curve of experimental s o i l APPENDIX 3 Types and amounts of n u t r i e n t s o l u t i o n s added to the experimental s o i l /168 Appendix 3 Stock Relat ive Nutrient Regime Amount of Stock Solut ion Added / Pot Solut ion 2N 3N _N (ml) grams/ l i t re H 2 0 (NH^) 2S0^ 96.01 153.74 268.98 25 KNO^ 9.09 14.54 25.45 10 KH_PO^ 2.29 3.44 5-73 10 MgSO^^HgO 4 .14 8.27 16.55 10 C a C l 2 10.19 20.38 40.76 10 KC1 2.68 8.71 20.69 10 /169 APPENDIX k Hygrometer c a l i b r a t i o n Appendix 4 Avg. MY Output Var i a t ion - M.Y.. AAY ^A.Y Output (bar ) Hygrometer 3 output No. 0.2 Mol 0.5 Mol 0.2 Mol 0.5 Mol i n D i s t . 0.2 Mol 0.5 Mol HgO 1 6 . 8 7 12.82 0.10 0.10 - 0 . 3 0 0.75 0.58 2 5.94 15.80 0.25 0.10 -0.20 O.67 0.70 3 5 . 9 4 15*24 0.12 0.08 -0.25 0.68 0.68 4 5 « 8 7 12.29 0.15 0.10 . -0.10 0.65 0.54 5 5.32 14.50 0.25 0.10 -0.20 0 . 6 0 0.64 6 6 . 0 9 1 2 . 7 3 0 . 1 7 0 . 2 0 -0.35 0 . 7 0 0 . 5 7 7 5 - 9 2 15.51 0-20 0.22 - 0 . 2 5 0 . 6 7 0.69' 8 6.41 I 6 . 5 0 0.12 0 . 1 5 -0.10 0 . 7 1 0 . 7 2 1 2 -9.15 bars - 2 2 . 8 1 bars 

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