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Effects of seeding rate and time of nitrogen fertilizer application on winter wheat in south coastal… Tarus, Hoseah Kibett 1991

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EFFECTS OF SEEDING RATE AND TIME OF NITROGEN FERTILIZER APPLICATION ON WINTER WHEAT IN SOUTH COASTAL BRITISH COLUMBIA by Hoseah Kibett Tarus B.Sc.(Agric), Illinois State University, 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Soil Science) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August 1991 ©Hoseah Kibett Tarus In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of S o i l Science The University of British Columbia Vancouver, Canada Date August 12, 1991 DE-6 (2/88) ii ABSTRACT A two year field experiment was carried out in Delta Municipality approximately 30 km south of Vancouver, British Columbia on a Crescent silty clay loam. The study was designed to investigate the effects of seeding rate and time of N application on intensively managed winter wheat (Triticum aestivum L.) cv. Monopol. In 1988-89, seeding rates were: 200, 250 and 300 seeds m"2, while in 1989-90 they were 150, 300 and 450 seeds m"2. Nitrogen treatments consisted of 0 or 225 kg N ha"1 as ammonium nitrate split-applied at Zadoks growth stages (GS) 22,31 or 37 (0/0/0; 0/125/100; 25/125/75; 50/125/50 kg N ha"*). The number of established plants significantly increased with increasing seeding rate in both years. Shoot counts (main stem + tillers) were not significantly influenced by seeding rate in 1988-89, but a linear relationship existed in 1989-90. Shoot mortality, however, was higher at the high seeding rate and commenced earlier in the season. Time of N application had no effect on shoot production, nevertheless, N application enhanced shoot survival. Without N , disease incidence was higher at the lower seeding rate in 1988-89, while N application increased disease incidence over the control in 1989-90. Grain yield and yield components were not significantly influenced by seeding rate in 1988-89. In 1989-90, grain yield and grains m~2 significantly decreased with increasing seeding rate, while number of heads n r 2 and number of grains head"1 were not significantly affected. In both years, thousand grain weights were maximized at the lower seeding rate with added N . Grain yield and yield components, except for number of grains head"1 in 1988-89, were sigTuficantly increased with N application over the control in both years, however, time of N application had no significant effect. i i i Dry matter yields at GS 31 in 1988-89 and GS 37 in 1989-90 linearly increased with increasing seeding rate. At the lowest seeding rate, dry matter yield increased with N3 compared with N2 at GS 37 in 1989-90. Delayed N significantly reduced dry matter yields at GS 37 in both years and at GS 69 in 1989-90. With added N , dry matter yields significantly decreased with increasing seeding rate at GS 85 and at GS 92 in 1989-90. N uptake linearly increased with increasing seeding rate at GS 31 in 1988-89. Delayed N significantly reduced N uptake at GS 31 in 1988-89 and at GS 37 in both years. Harvest index was not significantly influenced by seeding rate in 1988-89, but it decreased significantly with increasing seeding rate in 1989-90. In both years, harvest index was increased with N application and in 1988-89 it was maximized with delayed N. While grain protein was increased with N application in both years, it was maximized in 1989-90 by delaying the first N application until GS 31. N application significantly increased soil mineral N at GS 37 in 1988-89 and throughout the growth period in 1989-90. Low levels of mineral N , as calculated by the difference method, remained in the top 0-50 cm of soil at the end of each season. iv TABLE OF CONTENTS Page ABSTRACT ii TABLE OF CONTENTS iv LIST OF TABLES vi LIST OF FIGURES vii LIST OF APPENDICES viii ACKNOWLEDGEMENTS xi 1.0 INTRODUCTION 1 1.1 The Significance of Winter Wheat in South Coastal B.C 1 1.2 Objectives 2 2.0 LITERATURE REVIEW 3 2.1 An Overview of Intensive Cereal Management 3 2.2 Studies Involving Seeding Rates and Nitrogen Fertilization for Winter Wheat 6 2.3 Specific Effects of Seeding Rate 9 2.3.1 TiUering 9 2.3.2 Yield and yield components 10 2.3.3 Total dry matter yield 12 2.3.4 Harvest index 12 2.3.5 Nitrogen uptake 13 2.3.6 Lodging 13 2.3.7 Diseases 14 2.4 Specific Effects of Time of Nitrogen Fertilizer Application 14 2.4.1 Tillering 14 V Page 2.4.2 Yield and yield components 15 2.4.3 Total dry matter yield 16 2.4.4 Harvest index 17 2.4.5 Nitrogen uptake . . 17 2.4.6 Grain protein content .18 2.4.7 Lodging 19 2.4.8 Diseases 19 2.5 Recovery of Applied Fertilizer N 20 2.6 Summary and Relevance to South Coastal B.C 21 3.0 MATERIALS A N D METHODS 23 3.1 Site Description 23 3.2 Experimental Layout 23 3.3 Field Sampling 24 3.4 Laboratory Methods 26 3.5 Statistical Analysis 28 4.0 RESULTS 29 4.1 Weather Conditions 29 4.2 1988-89 Experiment 29 4.3 1989-90 Experiment 35 5.0 DISCUSSION 47 6.0 CONCLUSIONS 55 7.0 RECOMMENDATIONS 57 8.0 LITERATURE CITED 58 APPENDICES 67 vi LIST OF TABLES Page Table 3.1 Nitrogen fertilizer treatments applied as ammonium nitrate . . . . 24 Table 3.2 Growth stages and corresponding sampling dates 25 Table 4.1 Main effects of seeding rate and N treatments on grain yield and some yield characteristics in 1988-89 30 Table 4.2 Main effects of seeding rate and N treatments on dry matter yields in 1988-89 31 Table 4.3 Main effects of seeding rate and N treatments on N uptake in 1988-89 34 Table 4.4 Main effects of seeding rate and N treatments on soil N H 4 - N + N 0 3 - N (0-50 cm) in 1988-89 36 Table 4.5 Balance of applied fertilizer N (%) in 1988-89 36 Table 4.6 Main effects of seeding rate and N treatments on grain yield and some yield characteristics in 1989-90 39 Table 4.7 Main effects of seeding rate and N treatments on dry matter yields in 1989-90 40 Table 4.8 Significant (P <0.05) interactions between seeding rate and N application on dry matter yields in 1989-90 40 Table 4.9 Main effects of seeding rate and N treatments on N uptake in 1989-90 43 Table 4.10 Main effects of seeding rate and N treatments on disease incidence at GS 83 in 1989-90 44 Table 4.11 Main effects of seeding rate and N treatments on soil N H 4 - N + NO3 -N (0-50 cm) in 1989-90 46 Table 4.12 Balance of applied fertilizer N (%) in 1989-90 46 vii LIST OF FIGURES Page Figure 4.1 Interaction between seeding rate and N application for thousand grain weight in 1988-89 32 Figure 4.2 Interaction between seeding rate and N application for disease rating in 1988-89 33 Figure 4.3 Effect of seeding rate on shoot counts in 1989-90 37 Figure 4.4 Effect of N treatments on shoot counts in 1989-90 37 Figure 4.5 Interaction between seeding rate and N application for grain yield in 1989-90 41 Figure 4.6 Interaction between seeding rate and N application for thousand grain weight in 1989-90 41 Figure 4.7 Interaction between early N application and seeding rate for dry matter at GS 37 in 1989-90 42 viii LIST OF APPENDICES Page Appendix 1 Some chemical properties of composite soil samples taken from control plots in early spring 67 Appendix 2 Mean monthly air temperatures (°C) and precipitation (mm) during the 1988-89 growing season compared with the mean data for the 1951-1980 period 68 Appendix 3 Mean monthly air temperatures (°C) and precipitation (mm) during the 1989-90 growing season compared with the mean data for the 1951-1980 period 68 Appendix 4 Analysis of variance for dry matter yield at GS 31 in 1988-89 . . 69 Appendix 5 Analysis of variance for dry matter yield at GS 37 in 1988-89 . . 69 Appendix 6 Analysis of variance for dry matter yield at GS 92 in 1988-89 . . 70 Appendix 7 Analysis of variance for N uptake at GS 31 in 1988-89 70 Appendix 8 Analysis of variance for N uptake at GS 37 in 1988-89 71 Appendix 9 Analysis of variance for N uptake at GS 92 in 1988-89 71 Appendix 10 Analysis of variance for soil N H 4 - N + NO3-N (0-50 cm) at GS 31 in 1988-89 72 Appendix 11 Analysis of variance for soil N H 4 - N + NO3-N (0-50 cm) at GS 37 in 1988-89 72 Appendix 12 Analysis of variance for soil N H 4 - N + N 0 3 - N (0-50 cm) at GS 92 in 1988-89 73 Appendix 13 Analysis of variance for grain yield in 1988-89 73 Appendix 14 Analysis of variance for thousand grain weight in 1988-89 . . . 74 Appendix 15 Analysis of variance for number of heads n r 2 in 1988-89 . . . . 74 Appendix 16 Analysis of variance for number of grains head"1 in 1988-89 . . 75 ix Appendix 17 Analysis of variance for number of grains n r 2 in 1988-89 . . . . 75 Appendix 18 Analysis of variance for harvest index in 1988-89 76 Appendix 19 Analysis of variance for grain protein in 1988-89 76 Appendix 20 Analysis of variance for disease ratings (head) at GS 83 in 1988-89 77 Appendix 21 Analysis of variance for disease ratings (flag leaf) in 1988-89 77 Appendix 22 Analysis of variance for number of plants established (40 days after seeding) in 1989-90 78 Appendix 23 Analysis of variance for shoot counts (71 days after seeding) in 1989-90 78 Appendix 24 Analysis of variance for shoot counts (131 days after seeding) in 1989-90 78 Appendix 25 Analysis of variance for shoot counts (207 days after seeding) in 1989-90 78 Appendix 26 Analysis of variance for shoot counts (235 days after seeding) in 1989-90 79 Appendix 27 Analysis of variance for shoot counts (263 days after seeding) in 1989-90 79 Appendix 28 Analysis of variance for shoot counts (302 days after seeding) in 1989-90 . 80 Appendix 29 Analysis of variance for dry matter yield at GS 37 in 1989-90 . . 80 Appendix 30 Analysis of variance for dry matter yield at GS 69 in 1989-90. . 81 Appendix 31 Analysis of variance for dry matter yield at GS 85 in 1989-90 . . 81 Appendix 32 Analysis of variance for dry matter yield at GS 92 in 1989-90 . . 82 Appendix 33 Analysis of variance for N uptake at GS 37 in 1989-90 82 X Appendix 34 Analysis of variance for N uptake at GS 69 in 1989-90 83 Appendix 35 Analysis of variance for N uptake at GS 85 in 1989-90 83 Appendix 36 Analysis of variance for N uptake at GS 92 in 1989-90 84 Appendix 37 Analysis of variance for soil N H 4 - N + N 0 3 - N (0-50 cm) at GS 37 in 1989-90 84 Appendix 38 Analysis of variance for soil N H 4 - N + NO3 -N (0-50 cm) at GS 69 in 1989-90 85 Appendix 39 Analysis of variance for soil N H 4 - N + N 0 3 - N (0-50 cm) at GS 85 in 1989-90 85 Appendix 40 Analysis of variance for grain yield in 1989-90 86 Appendix 41 Analysis of variance for thousand grain weight in 1989-90 . . . 86 Appendix 42 Analysis of variance for number of heads m*2 in 1989-90 . . . . 87 Appendix 43 Analysis of variance for number of grains head"1 in 1989-90 87 Appendix 44 Analysis of variance for grains n r 2 in 1989-90 88 Appendix 45 Analysis of variance for harvest index in 1989-90 88 Appendix 46 Analysis of variance for grain protein in 1989-90 89 Appendix 47 Analysis of variance for disease ratings (head) at GS 83 in 1989-90 89 Appendix 48 Analysis of variance for disease ratings (flag leaf) at GS 83 in 1989-90 90 Appendix 49 Analysis of variance for disease ratings (penultimate leaf) at GS 83 in 1989-90 90 xi ACKNOWLEDGEMENTS I wish to thank the Government of Kenya for granting me study leave, and the Government of Canada, through CIDA, for funding my study at U.B.C. The success of my thesis is attributed largely to the guidance and support of my graduate supervisor, Dr. Art Bomke to whom I pay glowing tribute. I am also grateful to the other members of my committee: Drs. Peter Jolliffe, Les Lavkulich and Stan Freyman for their assistance and constructive criticism of the thesis. The contribution in one way or another of Dr. Wayne Temple, Rola Hogan, Orlando Schmidt, Yu Shaobing and Lawrence Redfern is greatly appreciated. I would like to thank my parents for their love and support. Lastly, special thanks go to my wife, Rebecca, for her support, encouragement and patience throughout my study period. This thesis is dedicated to my daughters Jepkosgei and Jerotich. 1 1.0 INTRODUCTION 1.1 The Significance of Winter Wheat in South Coastal B.C. South coastal British Columbia is not a major cereal grain producing area, however, the recent past has witnessed the introduction of intensively managed winter wheat (Triticum aestivum L.) mainly for soil conservation purposes. Crop production practices in the region have intensified soil degradation processes such as compaction and erosion. Compaction occurs because local farmers are forced to conduct field operations on wet soils in early spring and late fall as required for spring seeded crops. The introduction and success of winter wheat in coastal B.C. would enable the farmers to carry out field operations during the drier months of the year (July, August and September) and thus minimize soil compaction. The presence of a cover crop during the winter months would aid in reducing soil erosion. Other benefits to be derived from the introduction of winter wheat include the provision of forage for the livestock industry or grain for milling and/or feed purposes (Bomke and French, 1986). The regional climate is exceptional with respect to precipitation and temperatures. The annual precipitation ranges from 900 to 1900 mm, and about 80% falls between October and April. Mean temperatures range from 2°C in January to 18°C in July (Bomke, 1990). The potential for N0 3-N leaching is greatest during winter and early spring. Because of the mild temperatures, winter wheat generally remains vegetative over the winter months and growth commences in early spring. During this time, the crop shows visual symptoms of N deficiency. Agronomic information pertaining to winter wheat based on local research is lacking; however, information from other regions with some 2 similarities in climate is available in the literature. Such available information, however, may not be directly applicable under south coastal B.C. conditions because slight differences in soil and climatic conditions may have considerable consequences. Therefore, the success of winter wheat in the region would demand that information be generated locally. Establishment of optimum seeding rates and timing of fertilizer N application are among other management practices which must be investigated. 1.2 Objectives In order to understand how seeding rate and time of fertilizer N application affect winter wheat under south coastal B.C. edaphic and climatic conditions, this research was planned with the following objectives: (1) To quantify yield and yield component responses to seeding rates and time of fertilizer N application. (2) To determine the effect of time of fertilizer N application on soil mineral N during the course of the season. 3 2.0 LITERATURE REVIEW 2.1 An Overview of Intensive Cereal Management Intensive cereal management popularly known as ICM is a western European concept of crop production started in the early 1970's (Hall, 1990). It is based on high levels of inputs and improved management; the idea being to force the plant to produce at its maximum potential. The success of ICM in western Europe is responsible for the high cereal yields, especially winter wheat (Triticum aestivum L.) achieved under favourable European conditions (Murphy, 1984; Hall, 1990). According to Hall (1990), the world record wheat yield of over 16.91 ha"1 is held by a British farmer, while the U.K. national average yield varies between 6.7 to 7.0 t ha - 1. Murphy (1984) points out that top Western European farmers frequently produce 8 to 91 ha"1. ICM experiences in the U.S. and Canada abound in the Uterature (Frederick and Marshall, 1985; Joseph et al, 1985; Baethgen and Alley, 1989a, 1989b; Bomke and Temple, 1989 and others). However, reported yields vary depending on environmental conditions. Joseph et al (1985) reported yields ranging from 5.0 to 8.1 t ha"1 in a high potential environment. Frederick and Marshall (1985) achieved yields ranging from 2.9 to 4.2 t ha"1. Bomke and Temple (1989) reported what is considered to be a Canadian record of 13.81 ha"1. However, their yields ranged from 2.5 to 13.81 ha"1. The major components of ICM include: (a) superior varieties, (b) narrow row spacings, (c) high seeding rates, (d) high rates and timing of fertilizer application, (e) plant growth regulators, (f) fungicides, and (g) tramlines. The role of each of the components will be elucidated briefly. 4 In order to realise high yields with ICM, cereal varieties must have the genetic potential and must also be responsive to improved management practices. In the U.K., for example, selection for shorter varieties with higher harvest indices accounts for at least 50% of yield improvement (Hall, 1990). With ICM, precision seeding is crucial and consequently the traditional way of expressing seeding rates as weight or volume per unit area has been replaced with number of viable seeds per unit area. The concept takes into consideration the fact that grain weights can vary considerably (Puri and Qualset, 1978). High seeding rate is essential in creating a high population of heads necessary for high yields. In the Netherlands, for instance, 400-500 heads n r 2 is considered optimum for high yields and the bulk of the heads originate from main stems and apparently are more productive than those originating from tillers (Darwinkel, 1978). Row spacing usually influences yields. Several researchers have reported significant yield increases due to narrow row spacings (Joseph et al, 1985; Marshall and Ohm, 1987; Johnson et al, 1988). Holiday (1963) attributed this to a better spatial arrangement which allows for better utilization of environmental resources. Narrow rows tend to delay the time of leaf and root zone overlap from neighbouring plants. Maximum benefits from narrow rows accrue when soil moisture is not a limiting factor (Roth et ah, 1984). In fact, a combination of increased seeding rate and narrow row spacing result in even higher yield increases (Marshall and Ohm, 1987). Nevertheless, narrow rows are associated with problems of trash and clods (MAFF, 1980). ICM calls for high levels of plant nutrients in order to maximize yields. The system, however, demands a greater understanding of the relationship between plant growth and fertilizer application (Hall, 1990). Among the plant 5 nutrients, nitrogen has received the greatest coverage (Ellen and Spiertz, 1980; Roth and Marshall, 1987; Baethgen and Alley, 1989a, 1989b; Bomke and Temple, 1989 and others). Source, rate and timing are the main components of nitrogen management that have been studied. Multiple applications based on plant growth stage rather than calendar date are currently a common practice especially in the humid regions. Rates of application in Western Europe range from 190 to 250 kg N ha'1 (Murphy, 1984). Use of fungicides is an integral part of ICM. A combination of high levels of nitrogen and high seeding rates generally results in dense crop canopies and high moisture conditions suitable for fungal disease development (Roth et al, 1984). Fungicide responses, however, depend on disease severity (Roth and Marshall, 1987; Cox et al, 1989). Plant growth regulators are included in ICM programmes in order to limit losses due to lodging. Intensive management systems encourage lush crop growth with spindly stems susceptible to lodging. Early lodging results in poor grain fill while late lodging hinders harvesting operations. Plant growth regulators, if applied at the correct growth stage, shorten and strengthen the stem of the wheat plant making it less likely to lodge (Nafziger et al, 1986; Bomke and Temple, 1989). Where lodging is not a problem, plant growth regulators may not be necessary but may act as an insurance factor (Bomke and Temple, 1989). Tramlines are unseeded rows through a field in which tractor and sprayer or fertilizer applicator wheels travel. Tramlines are established at seeding by blocking the seed dispensing openings that correspond to the tracks of the equipment to be used during the course of the season (Brann et al, 1987). Because ICM necessitates several trips through the field during the course of the 6 season, tramlines are essential in order to avoid crop damage due to trampling. Other equally important advantages include: (a) precise application of inputs that occur after seeding, (b) timeliness of operations, and (c) reduced soil compaction. Yield loss due to tramlines is partially compensated by increased growth of border plants along the tramlines (Watson and French, 1971; Paulsen, 1987). 2.2 Studies Involving Seeding Rates and Nitrogen Fertilization for Winter Wheat Seeding rate plays a major role in crop development (Jurgens, 1988). Early studies on the effects of seeding rate on winter wheat were reviewed by Holiday (1960). He noted that varying seeding rates had relatively small effects on grain yields, except for reductions caused by excessively high or very low seeding rates. Holiday (1963), however, noted that changes in seeding rate had larger effects on grain yields when planted in narrow rows. Effects of seeding rate on yield are generally attributed to interplant and intraplant competition for environmental resources and to lodging and disease incidences (Darwinkel, 1978; Roth et al, 1984; Broscious et al, 1985). According to Willey and Heath (1969), grain and total dry matter yields respond parabolically and asymptotically respectively to increasing seeding rate. The wide range of optimum seeding rates reported in the literature can be ascribed to environmental influences, cultivar differences, strong mutual compensation among yield components and the expression of seeding rates as weight or volume per unit area (Paulsen, 1987). In low-yield environments, interplant competition limits yields at excessive seeding rates due to soil moisture depletion while in high-yield environments, lodging and disease pressure are the Umiting factors (Kolp et al, 1973; Roth et al, 1984). 7 Seeding rate recommendations for wheat in the U.S. and Canada, assuming 34.0 g 1000-1 grain weight, range from 67 seeds n r 2 in the dryland plains to 400 seeds n r 2 in eastern regions of Canada and the U.S. (Paulsen, 1987). Although a seeding rate of 200 seeds n r 2 is common in Pacific Northwest for winter wheat, adjustments are necessary depending on local conditions (Paulsen, 1987). In Western Europe, a post-winter target population of 200 to 250 plants nr 2 is suggested (MAFF, 1980; Jurgens, 1988). In Kenya, the general recommendations for spring wheat assuming 34.0 g 1000"1 grain weight, range from 294 to 368 seeds nr 2 . However, growers invariably adjust upwards depending on their own experiences (personal observations). Nitrogen is a constituent of all proteins and nucleic acids and therefore is essential for plant growth (Mengel and Kirkby, 1987; Wild, 1988). It plays a central role in regulating plant development assuming other nutritional requirements are met (Jurgens, 1988). Winter wheat is usually more responsive to the addition of nitrogen than any other element. On average, 1 kg of N produces about 15 kg of grain (Wibberley, 1989). Responses to nitrogen application are greatly influenced by environmental factors (Keeney, 1982). Rates of application depend largely on (a) target yield, (b) cultiyar, (c) soil type, (d) residual mineral N , (e) soil organic matter, and (f) climate (Olson and Kurtz, 1982; Rauschkolb et al, 1982; Halvorson et al, 1987). In arid regions, measurement of soil N 0 3 - N is routinely used to predict optimum fertilizer N applications (Dahnke and Vasey, 1973; Keeney, 1982). The determination of optimum fertilizer N , however, is a major problem in humid climates (Stanford, 1982; Baethgen, 1989b). In humid environments, the nitrogen content of the soil during winter and spring is too dynamic to serve as an indicator of N availability to the crop (Fox and Piekielek, 1978). Doll (1962) 8 attributed 20 to 23% of the yield variability in winter wheat to winter precipitation. Difficulties of soil tests for N in humid regions has led to the evaluation of plant tissue N content during spring growth as a means of assessing N requirements. Baethgen and Alley (1989b) reported critical levels of 39.5 g N kg"1 and 95 kg N ha"1 for whole plant N concentration and N uptake respectively at Zadoks growth stage (GS) 30 (Zadoks et al, 1974). Other workers have also explored the use of tissue testing for N recommendation (Donohue and Brann, 1984; Roth et al, 1989). Timing of N applications has been studied as a means of improving crop N use efficiency. Applying fertilizer N as close as possible to the time of crop N demand throughout the growing period lowers the potential for N losses through leaching, N H 3 volatilization or denitrification (Rauschkolb et al, 1982; Olson and Kurtz, 1982). Results from timing of fertilizer N application studies, however, are variable (Touchton et al, 1983; Roth and Marshall, 1987; Temple and Bomke, 1990). Experimental results assessing N requirements for optimum grain yield are generally environment-specific (Batey, 1976; Roth et al, 1984). Generally grain yields of winter wheat grown on soils low in residual N respond positively to increments of N until yield is maximized; additional N either does not affect or decreases grain yields (Batey, 1976; Roth et al, 1984). Decreased grain yields from excessive N applications are associated with lodging, stress due to excess N-stimulated vegetative growth and disease pressure (Pinthus, 1973; Frederick and Marshall, 1985). 9 2.3 Specific Effects of Seeding Rate 2.3.1 Tillering The term tiller is not well defined in the literature but often used in reference to (a) any lateral shoot whether or not it has emerged from the subtending leaf sheath, (b) any emerged shoot, (c) a shoot in which internode elongation has taken place, (d) a shoot visible at harvest and (e) a head-bearing shoot (Simons, 1982). When used in this text, it will be in reference to (a) above. Darwinkel (1978) in the Netherlands examined the effects of a wide range of plant densities (5 to 800 plants nr 2) on patterns of tillering in winter wheat. The number of tillers n r 2 increased with increasing plant density. However, a 160-fold increase in plant density led only to a 12-fold increase in number of tillers due to abundant tillering at the lower plant densities. More shoots (main stems + tillers) were produced on a per area basis at the higher densities but more tillers per plant were produced at the lower densities. On the other hand, senescence of shoots started earlier at higher densities. At the 5 plants m"2 rate, 80% of the shoots produced heads while at the 800 plants n r 2 rate, only 45% of the shoots produced heads. Almost all tillers died at the highest seeding rate. McLaren (1981) in England investigated the effects of plant density on tiller production and survival in winter wheat. Plant densities ranged from 150 to 500 seeds m"2. At higher plant densities more tillers n r 2 were produced; however, the lower plant densities produced more tillers plant"1. The maximum number of tillers m"2 was obtained 20 to 30 days later at the lower plant densities. Tiller mortality was linearly related to the maximum number of tillers m - 2 . 10 2.3.2 Yield and yield components Winter wheat grain yield is a product of three yield components: (a) number of heads per unit area, (b) number of grains head -1, and (c) grain weight. Although compensation occurs among these components and tends to minimize yield loss, a Umitation of one component cannot be completely compensated by the others (Darwinkel, 1978). Darwinkel et al. (1977) studied the effects of sowing date and seeding rate in several experiments. Seeding rates ranged from 80 to 180 kg ha"1 of seed while sowing dates ranged from late September to mid-December. The effect of seeding rate on grain yield depended on sowing date. Seeding rate influenced grain yield only at the late sowing date with high seeding rate resulting in higher grain yield. Seeding rate had a positive effect on the number of heads n r 2 and a negative effect on the number of grains head"1 and grain weight. Darwinkel (1978) measured a 3-fold increase in grain yield (2.8 to 8.5 t ha"1) for a 160-fold increase in plant density (5 to 800 plants nr 2). The number of heads n r 2 increased with increasing plant density while grain number head"1 was reduced at higher densities. Grain weight increased and reached a maximum (44.6 g 1000"1) at 50 plants n r 2 but declined with further increases in plant density. Maximum grain yield was achieved at 100 plants nr 2 , which corresponded to 430 heads n r 2 and to about 19,000 grains m"2. Smid and Jenkinson (1979) in Ontario included seeding rates ranging from 34 to 168 kg ha"1 of seed in their study. Highest yields were obtained at 134 kg ha - 1 of seed. However, seeding rate interacted with date of seeding and showed that higher seeding rates were required with delayed seeding in agreement with the findings of Darwinkel et al. (1977). Increasing the seeding rate resulted in an increase in the number of heads n r 2 but the number of grains head"1 decreased. 11 They concluded that number of heads n r 2 was the most important yield component determining grain yield. Roth et al. (1984) in Pennsylvania investigated the effects of three seeding rates (100,168 and 235 kg ha - 1 of seed) in 15 environments. Responses to seeding rate were variable across the environments. At four locations, 235 kg ha - 1 of seed produced the highest yields while at two locations the highest yields were achieved at 100 kg ha"1 of seed. The greatest responses to seeding rate occurred following late planting or severe winters. The authors concluded that seeding rates higher than 168 kg ha - 1 of seed would only be justified where environmental conditions may limit tillering. Frederick and Marshall (1985) in Pennsylvania looked at the effects of seeding rate as one of the management practices in their study. Seeding rates ranged from 101 to 235 kg ha"1 of seed. Significant positive grain yield response to seeding rate occurred at 3 of 8 sites. As seeding rates were increased, significant linear or quadratic increases occurred for thousand grain weight at 6 sites, while linear or quadratic decreases in the number of grains head"1 occurred at all sites. The authors concluded that seeding rates beyond 101 kg ha"1 of seed would likely not increase grain yield due to decreases in the number of grains head"1. Johnson et al. (1988) in Georgia investigated the effects of two seeding rates (288 and 576 seeds m"2) on yield and yield components. Grain yield did not respond to increased seeding rate when averaged over the two years. However, the higher seeding rate resulted in higher grain yield in 1985 because of severe winter injury. Number of heads n r 2 and grain weight were increased with increasing seeding rate but the number of grains head"1 decreased. The authors 12 suggested a seeding of 500 seeds n r 2 as being adequate for high grain yields under intensive management. 2.3.3 Total dry matter yield The response of total dry matter yield to increasing plant density is asymptotic in nature (Willey and Heath, 1969). In his study, Darwinkel (1978) reported a linear increase in total dry matter over the whole range of plant densities with yields ranging from 7.1 to 23.81 ha"1. The response was attributed to more and longer stems formed at higher densities. Ellen (1987) in the Netherlands reported higher total dry matter yield at higher plant density due to a larger number of shoots m"2. Puckridge and Donald (1967) in Australia reported marked differences between low and high seeding rates at GS 32. However, at GS 83 there were no differences between the three highest densities and in fact yields started to decline. The response of the two lowest densities was asymptotic. Maximum yields for all densities occurred at GS 83. 2.3.4 Harvest index Harvest index is the ratio of grain yield (dry basis) to total above-ground dry matter yield and is considered as an expression of the efficiency of grain production (Donald and Hamblin, 1976). Darwinkel (1978) examined the effect of plant density on harvest index. With increasing plant density, harvest index increased and reached a maximum at 50 plants n r 2 and then declined. The author attributed the decline to the fact that more and longer stems were formed at higher densities which contributed to higher total aboveground yield with no influence on grain yield. At densities below 50 plants m"2, the low grain yield of the late-formed tillers depressed harvest index. McLaren (1981) recorded lower harvest indices at high densities. 13 Sharma and Smith (1987) in Oklahoma did not find a significant effect of plant density on harvest index. 2.3.5 Nitrogen uptake Nitrogen uptake generally follows the pattern of dry matter production closely. Puckridge and Donald (1967) examined a wide range of plant densities (1.4 to 1078 plants nr 2) in their study and measured N uptake. The peak value was greater for successively higher densities and occurred earlier; however, at higher densities sharper declines were observed than at lower densities. At final harvest there was no difference between the three highest densities. 2.3.6 Lodging Lodging is the state of permanent displacement of stems from their upright position. Losses due to lodging depend on the growth stage at which it occurs (Pinthus, 1973). Light intensity is a major factor influencing lodging through its effects on internodes. Low light intensity promotes internode elongation and reduces stem-wall thickness due to the action of gibberellic acid. In dense crop stands light intensity readung the lower internodes is reduced and subsequent elongation may cause lodging (Mulder, 1954; Pinthus, 1973). Smid and Jenkinson (1979) assessed the effect of seeding rate (34 to 168 kg ha - 1 of seed) on lodging. However, seeding rate did not affect lodging. Roth et al. (1984) reported increased lodging with increasing seeding rate (100 to 235 kg ha*1 of seed). Interaction between seeding rate and N application, however, indicated that lodging was severe where high seeding rates were combined with high N rates. 14 2.3.7 Diseases Diseases attacking the wheat plant are affected by moisture because many pathogens require free water for infection (Calhoun, 1973). Growth habit and seeding density of a crop can be significant factors in increasing humidity near the leaf surfaces and thus predispose the crop to disease attack (Zentmyer and Bald, 1977). Common diseases include: take-all (Gaeumannomyces graminis); leaf spot (Septoria tritici); leaf rust (Puccinia recondita); stripe rust (Puccinia striiformis); glume blotch (Septoria nodorum); eyespot (Cercosporella herpotrichoides); powdery mildew (Erysiphe graminis). Glynne (1951) in England reported an increase in eyespot (Cercosporella herpotrichoides) and take-all (Gaeumannomyces graminis) with increased seeding rate. Broscious et al. (1985) in Pennsylvania investigated the effects of seeding rate on powdery mildew (Erysiphe graminis) and glume blotch (Septoria nodorum). Seeding rate influenced powdery mildew at three of thirteen locations. At two of the three locations the disease linearly decreased with increasing seeding rate while at the third location the response was quadratic, with least disease at the medium rate. Seeding rate influenced Septoria at five of thirteen locations. Disease severity increased with density at four of the five locations while at the fifth location there was an inverse relationship. 2.4 Specific Effects of Time of Nitrogen Fertilizer Application 2.4.1 Tillering The time of N application has a major effect on tiller production and survival. Generally, early N application promotes tiller formation while later application improves tiller survival (Bremner, 1969). 15 Bremner (1969) in England investigated the effects of early (March 10) and late (May 4) N application on tillering. Although early application of N caused an increase in the number of tillers, the size of the tillers was restricted due to competition for light. Late application of N encouraged tiller survival and enhanced the size of tillers. Darwinkel (1983) found similar results. McLaren (1981) studied the effects of time of N application in several experiments. In the 1977-78 experiment, time of N appUcation had no significant effect on tiller production. However, in 1978-79, the time of N application had large effects on the number of tillers. Delaying the application of N until GS 18 reduced the maximum number of tillers compared to treatments which received N at GS 14. The author reckoned that residual N was high in 1977-78 and low in 1978-79. 2.4.2 Yield and yield components Bremner (1969) compared the effects of early (March 10) and late (May 4) N applications on yield and yield components. Although late application of N resulted in a 5% yield advantage, the number of heads m~2 was decreased, however, the number of grains head - 1 and grain weight were increased. McLaren (1981) assessed the effects of time of N application over a two-year period (1977-78 and 1978-79). Single or split applications were made at GS 14, 16 or 18. Time of N application had no effect on grain yield in 1977-78; however, delaying N application until GS 18 decreased grain yield in 1978-79 apparently due to low residual N as mentioned earlier in the text. Darwinkel (1983) investigated the effects of time of N application on yield and yield components. A blanket application of 90 kg N ha"1 was made at GS 20-21. A second dose of 60 kg N ha"1 was applied at GS 21,30,32,39 or 47 while a 16 last blanket application of 60 kg N ha"1 occurred at GS 52. Grain yield and the number of heads m"2 were maximized when the second application of N occurred at GS 30. The number of grains head"1 and grain weight were maximized when the second application of N was made at GS 32 and 47 respectively. Prew et al. (1986) in England conducted several experiments to investigate the effects of time of N application on yield and its components. In the 1981-82 experiment, late application of N decreased grain yield due to low number of heads nr 2 . However, in the 1982-83 and 1983-84 experiments time of N application did not influence grain yield because the decrease in the number of heads n r 2 was compensated by the increase in the number of grains head -1. The authors noted that residual N was low in 1981-82. Bomke and Temple (1989) in south coastal British Columbia conducted experiments at four locations to investigate the effects of time of N application on grain yield. Nitrogen was split-applied at GS 22, 31 or 37. At three of the four locations, highest yields were achieved when N application was delayed until GS 31. The fourth location gave highest yields when first N was applied at GS 22. 2.4.3 Total dry matter yield Nitrogen plays a significant role in dry matter production through its effects on tillering and leaf area. The period of rapid dry matter accumulation begins at jointing (GS 30-31) and lack of N at this stage can hamper dry matter production. Ellen and Spiertz (1980) in the Netherlands examined the effects of time of N appUcation on dry matter yield. A total of 140 kg N ha"1 was applied in a two-way split. The first N dose of 60 kg N ha"1 was applied at GS 22, 27,30, 31 or 37. The second appUcation of 80 kg N ha"1 occurred at GS 45. Delaying the first N 17 application until GS 37 resulted in a lower total dry matter yield mainly due to fewer shoots m"2. Prew et al. (1986) found similar results. 2.4.4 Harvest index Nitrogen has an enormous influence on harvest index due to its effect on vegetative growth. Under optimum growing conditions, N application generally increases total dry matter yield at the expense of harvest index (Donald and Hamblin, 1976). However, timing of N application can be manipulated in order to improve harvest index. Several researchers (Ellen and Spiertz, 1980; McLaren, 1981; Darwinkel, 1983; Prew et al., 1985, 1986) have reported increased harvest indices due to delayed N application. However, delayed N application is often associated with decreases in either total dry matter yield (McLaren, 1981) or straw yield (Prew et al, 1985,1986). 2.4.5 Nitrogen uptake Timing of N appUcation to match crop demand throughout the growing period ought to improve the efficiency of N uptake by winter wheat especiaUy in humid regions where N losses are greatest (Dilz, 1987). EUen (1987) studied the effects of initial N appUcation at various growth stages (GS 22, 27, 30,31, 32 or 37) on N uptake. Delaying the first N application until later growth stages did not affect N uptake presumably due to low precipitation in early May. However, delaying the first N appUcation until GS 37 resulted in rapid accumulation of N . Baethgen and Alley (1989a) in Virginia conducted several field experiments to investigate the effects of time of N application on crop N uptake. Treatments consisted of single or split N applications at GS 25 or 30. In the 1983-84 experiment, spring growing conditions were wetter and cooler than normal. 18 A single application at GS 30 resulted in high uptakes. On the other hand, a single application at GS 25 gave lower uptakes. Split application was intermediate. In the 1984-85 experiment, precipitation in spring was considered below normal and consequently the effects of N treatments were less compared to the 1983-84 season. 2.4.6 Grain protein content The desired grain protein content depends on the end-use (Hunter and Stanford, 1973). The baking quality of wheat flour is related to gluten protein content (Mengel and Kirkby, 1987). The minimum acceptable grain protein concentration for milling purposes is approximately 11.5% (Campbell et al., 1990). The major factors that influence grain protein content include (a) climate, (b) soil and (c) variety. Generally, climate and soil fertility, especially available N , exhibit greater influences (Schlehuber and Tucker, 1959). Winter wheat is generally known to have low grain protein content (Fowler and Brydon, 1989). Airman et al. (1983) noted that the production of hard red winter wheat in the Pacific Northwest is limited by the low protein content. Hucklesby et al. (1971) in Illinois examined the effects of time of spring N application on grain protein. Time of N application influenced grain protein contents. Delaying N application consistently increased grain protein content. Fowler and Brydon (1989) in Saskatchewan looked at the effects of a series of fall and spring N applications on grain protein. Time of N appUcation influenced grain protein concentration in 6 of 21 trials. Early spring N applications resulted in grain protein concentrations that were equal or higher than fall N appUcations in all the six trials. Late spring N applications gave grain proteins that were equal or superior to early spring N appUcations in 20 of 21 19 trials. In 3 of 21 trials late spring N applications produced significantly higher protein contents than all other application times. 2.4.7 Lodging The effect of N on lodging is associated directly with its effect on basal stem internodes (long and spindly internodes) or indirectly through the promotion of a closed canopy which causes shading of the lower internodes and subsequent elongation due to the action of gibberellic acid (Pinthus, 1973; Mulder, 1954). Harris (1974) in England reported increased lodging with early spring N application and hardly any with late spring application. Roth and Marshall (1987) in Pennsylvania reported variable lodging responses to split and delayed spring N treatments. Early N (GS 23) enhanced lodging but delaying N application until GS 37 reduced it. Split N applications (GS 23 + GS 37) resulted in lodging ratings similar to those from the single application at GS 23. 2.4.8 Diseases Calhoun (1973) observed that the effects of plant nutrition on disease may be attributed to: (a) the effects on plant growth that can alter the microclimate and therefore affect infection and sporulation of the pathogen; (b) effects on cell walls and tissues and on the biochemical make-up of the host; (c) the rate of growth of the host which may allow seedlings to escape infection in their most susceptible stage, and (d) effects on the pathogen of changes in the soil environment. It is most unlikely that the above factors can operate independently under specific conditions. 20 Darwinkel (1980a) investigated the relationship between the mode of N application and yellow rust (Puccinia striiformis) infection. Nitrogen treatments included single or split appUcations at GS 23, 30, 32, 39 or 52. The effect of time of N supply influenced disease infection. The most severe infection occurred with a large early single N application. Delaying the second N application retarded the beginning of the epidemic; however, late N application stimulated fungal growth. Darwinkel (1980b) reported similar results with powdery mildew (Erysiphe graminis) using identical N treatments. Prew et al. (1985) reported decreased eyespot (Cercosporella herpotrichoid.es) infection with late application of N in one of two growing seasons. Bomke and Temple (1989) observed a relationship between early N application and disease infestation. 2.5 Recovery of Applied Fertilizer N Efficient utilization of applied fertilizer N is essential from an environmental point of view since unrecovered N can be a potential source of surface and ground water poUution (Macdonald et al., 1989). It is, therefore, necessary to account for appUed fertilizer N at the end of the growing season. Recovery, however, depends on factors such as rate, time and method of N application, source of N , cUmate, soil and cultivation techniques. Numerous researchers have studied N in the soil-plant system. Olson et al. (1979) in Kansas investigated the effects of fall and spring N applications on the fate of appUed N. Time of N appUcation did not influence crop recovery at the low rate (50 kg N ha-1) of N application. However, at the higher rate (100 kg N ha"1) of N appUcation the crop recovered approximately 10 kg more N ha"1 with spring than faU applications. Total N recovered was approximately 80% at both rates. Less N remained in the soil with spring than faU appUcations. Differences between fall and spring appUcations were attributed to immobilization of fall-applied N. Nitrogen losses did not differ 21 significantly between application times. Most of the fertilizer remaining in the soil was in the 0-10 cm depth which indicated that leaching did not contribute to losses. Between 9.7 to 10.3 and 19.7 to 23.4 kg N ha - 1 were unaccounted for at 50 and 100 kg N ha"1 rates respectively. The authors attributed losses to denitrification. Kowalenko (1989) in south coastal British Columbia investigated the fate of applied N in fallowed field microplots over an entire year. Applied N was equivalent to 120 kg N ha"1 to a depth of 15 cm. The results confirmed the findings of a similar study (Kowalenko, 1987) that leaching losses throughout the growing season are minimal; however, all residual NO3-N is leached out over the winter months. Negligible denitrification was observed during the growing season despite high moisture levels as was found by Myrold (1988) in Oregon. Although N H 4 - N fixation was high following N application, it cUminished soon afterwards. While mineralization contributed about 100 kg N ha - 1 between early May and late August, irrtmobilization occurred in late fall. Janzen et al. (1991) in Alberta evaluated the effects of times of N application on crop recovery in several experiments. In the 1985-86 experiment, uptake of fertilizer-derived N ranged from 18 to 52% of that applied. Fertilizer-use efficiency increased with progressive delays in application from seeding to early spring and then declined precipitously with further delays in application. In the 1986-87 experiment, uptake of fertilizer-derived N ranged from 25 to 60% of that applied and treatment effects were similar to those of 1985-86. 2.6 Summary and Relevance to South Coastal B.C. The use of ICM has enabled western European farmers to achieve high cereal yields. In the U.S. and Canada, ICM experimental results are variable and the variation is attributable to diverse environmental conditions. The success of ICM, however, hinges on favourable growing conditions. 22 The wide range of optimum seeding rates reported in the literature can be attributed mainly to environmental influences, mutual compensation among yield components, cultivar differences, date of planting and the expression of seeding rates as weight or volume per unit area instead of as number of viable seeds per unit area. High seeding rates often cause an increase in number of heads n r 2 and a decrease in both number of grains head"1 and grain weight. The effect on harvest index is inconsistent. Nitrogen responses are largely influenced by environmental factors. In arid areas, soil NO3-N is routinely used to predict optimum fertilizer N application but the approach is not applicable in humid regions. Tissue testing instead offers a viable alternative for humid climates. Effects of time of N application on grain yield are inconsistent and mostly affected by residual mineral N . However, early appUcation of N often causes increases in tiller production and heads nr 2 . A high rate of early N encourages disease infection. Late appUcation of N by and large results in higher protein contents, grain weights, harvest indices and fertilizer-use efficiency. While delayed N may retard disease infection, later appUcation of N may stimulate fungal growth. By virtue of its cUmate, south coastal B.C. has the potential to support intensively managed winter wheat. However, the literature indicates substantial edaphic and cUmatic influences on management variables. For instance, the heavy precipitation experienced in south coastal British Columbia during the winter months and early spring would result in heavy losses of available soil N and fall applications of N as practised in other regions would be inappropriate. Disease pressure would also be a major concern locaUy because of high humidity. Therefore, local research is necessary to achieve appropriate agronomic package for south coastal B.C. 23 3.0 MATERIALS A N D METHODS 3.1 Site Description The two year (1988-89 and 1989-90) field study was carried out in Delta Municipality (Bert Nottinghams' farm), approximately 30 km south of Vancouver, British Columbia. The soil is classified as Crescent silty clay loam, Orthic Gleysol, whose parent material is deltaic alluvial deposits (Luttmerding, 1981). Some chemical characteristics of the soil from the study site are shown in Appendix 1. Although drainage in the general study area is a problem, the fields used to conduct the experiment were underdrained. The preceding crop in both seasons was field peas (Pisum sativum L.). 3.2 Experimental Layout The experiment was conducted as a split-plot in a randomized complete block design with twelve treatment combinations and four replicates. Main- and sub-plots were made of seeding rates and time of fertilizer N application respectively. Sub-plots measured 4 m x 6 m and 3 m x 8.75 m in 1988-89 and 1989-90 respectively. In 1988-89, seeding rate treatments were: 200, 250 and 300 seeds m~2, while in 1989-90 they were: 150, 300 and 450 seeds nr 2 . Nitrogen treatments consisted of a single rate (225 kg N ha - 1 as ammonium nitrate) split-applied at three growth stages as shown in Table 3.1. Hard red winter wheat (Triticum aestivum L.) cv. Monopol was drilled in 9.5 cm rows using a 3-m wide Vicon pneumatic seeder. Seeding was done on 29-9-88 and 19-9-89 using seed treated with "Vitavax". The drill was calibrated prior to seeding in order to achieve the desired seeding rates after adjusting for grain weight and percent germination. Fertilizer N was hand broadcast on each sub-plot at appropriate growth stages. A set of tramlines was established at seeding to facilitate 24 Table 3.1 Nitrogen fertilizer treatments applied as ammonium nitrate Treatment GS22 GS31 GS37 Total kgNha-i NO 0 0 0 0 NI 0 125 100 225 N2 25 125 75 225 N3 50 125 50 225 management of the experiment during the course of the season. Weed control was achieved using "Blagal" (Cyanacine + MCPA) tank-mixed with plant growth regulator "Cycocel" each at 2 L ha"1 at GS 31. Foliar and head disease(s) were controlled by using "Tilt" at a rate of 0.5 L ha"1 at GS 37 and GS 55. 3.3 Field Sampling The number of plants established in the fall and shoot counts at intervals during the course of the season were deterrnined. In 1988-89, Orlando Schmidt did the counting and procedures are contained in his undergraduate thesis (Schmidt, 1989). In 1989-90, established plants were counted on October 28. All five rows within randomly selected 0.25 m 2 quadrat areas were counted in each of the main plots. Fixed 0.25 m 2 quadrat areas were established within each sub-plot using small pegs and subsequently utilized for counting shoots (main stems + tillers) throughout the season. However, only one of the four fixed quadrat areas within each sub-plot was utilized for counting until fertilizer N was applied in early spring. The three middle rows were counted at each of the dates (Nov. 28; Jan. 27; Mar. 4; Apr. 1; Apr. 29 and June 7). Visual disease evaluation was done according to the disease assessment procedures devised by James (1971). Head and flag leaves were assessed in both 25 seasons, however, the penultimate leaf was included in the second season. From each sub-plot, 10 randomly selected plants were evaluated individually for the cumulative percentage of leaf or head covered with disease symptoms. No attempt was made to evaluate individual diseases but prevalent diseases were noted. Disease ratings on a 0 to 4 scale were done at GS 83 in the first season and at GS 59 and GS 83 in the second season. A rating of 0 = 0% cover; 1=1-5% cover; 2 = 6 - 25% cover; 3 = 26 - 50% cover and 4 = >50% cover. Severity values were averaged over the 10 plants. Plant and soil samples were collected at intervals during the growth period starting from early spring to final grain harvest. The various growth stages and corresponding calendar dates during which sampling occurred are indicated in Table 3.2. Samples were collected from randomly selected harvest areas measuring 1 m 2 within each of the sub-plots. Plants were cut just above the ground level using a hand sickle. Except for the final harvest, fresh weights were recorded in the field and sub-samples of 1 kg were transported to the laboratory. At final harvest, head counts were made by counting the middle two 1-m row lengths within the 1 m 2 harvest areas. Final harvest samples were threshed using an electric stationary thresher and separated into grain and straw samples. Table 3.2 Growth stages and corresponding sampling dates Growth stage 1988-89 1989-90 31 37 69 85 92 April 10 May 5 May 1 June 6 July 12 Aug. 3 x x X July 31 xSampling not done. 26 Soil samples were taken from within the 1 m 2 harvest areas after the removal of the plant material. Soil samples were collected at each harvest date except at the final harvest in 1989-90 growing season. Two depths (0-20 cm and 20-50 cm) were sampled using a 2.5 cm Oakfield sampling probe. Samples consisted of six composite soil cores taken from each plot. The samples were placed in labelled polythene bags and transported in coolers to the laboratory where they were stored in a refrigerator at 4°C. N H 4 - N and NO3-N were extracted within 24 hours. Four bulk density cores (volume = 480 cm3) were taken from the 0-20 cm and 20-50 cm depths at the first harvest and from the 0-20 cm depth at the second harvest. 3.4 Laboratory Methods Whole shoot, straw and grain samples were dried at 65°C in a forced air oven for 72 hours. After dry weight determination, whole plant and straw samples were ground with a stainless steel Wiley mill to pass a 2-mm screen, while grain samples were ground with a rotary hammer mill to pass a 1-mm screen. Samples of 0.5 g were digested following procedures outlined by Parkinson and Allen (1975) and N concentration was determined colourimetrically using a Technicon Autoanalyzer II (Technicon, 1974). Whole plant, straw and grain N uptake (kg N ha"1) were calculated by multiplying N concentration of the components by the dry matter yield (kg ha*1). Recovery of fertilizer N was calculated by the difference method using the following formula: N F - N C % recovery = x 100 R 27 where: NF = N uptake in fertilized plot. NC = N uptake in control plot. R = Rate of applied fertilizer N. Soil samples were mixed in their respective polythene bags before extraction. Soil water contents of the samples were determined by oven drying 30 g of soil at 105°C for 24 hours and reweighing (Gardner, 1986). Bulk density samples were treated in a similar manner. Field moist sub-samples of 10 g were extracted for N H 4 - N and N 0 3 - N by shaking with 50 mL of 1 M KCl for one hour (Keeney and Nelson, 1982). After settling, the supernatant was filtered through Whatman No. 42 filter paper. Two drops of toluene were added to the filtered extracts to inhibit microbial activity and the extracts were stored in 60 mL bottles at 2°C awaiting analysis. N H 4 - N and NO3-N concentrations were determined colourimetrically using a Technicon Autoanalyzer U, coupled with a cadmium reduction column for NO3 -N (Technicon, 1977). The soil samples used to describe the study site (Appendix 1) were extracted using the Kelowna extractant (0.015 N N H 4 F + 0.25 N CH3COOF1) and available nutrients determined following procedures outlined byGough(1991). Grain yields and protein contents were calculated at 13.5% water content. Grain protein was calculated as 5.7 x total grain N and expressed as a percentage by multiplying by 100. Thousand grain weight (TGW) was measured by counting and weighing 100 grains and multiplying by 10. Grains m"2 were calculated by dividing the harvested grain dry weight by weight grain"1, while grains head"1 were calculated by dividing grains m"2 by heads nr 2 . Harvest index was calculated by dividing grain yield (dry basis) by total above-ground biomass and expressed as a percentage by multiplying by 100. 28 3.5 Statistical A n a l y s i s Each seasons' data were subjected to analysis of variance following procedures outlined by Little and Hills (1978) using U.B.C.'s Mainframe Analysis of Variance (MFAV). Orthogonal contrasts were used to partition main effect and interaction sums of squares into single of freedom contrasts. Statistical significance was determined at the 5% probability level. 29 4.0 RESULTS 4.1 Weather Conditions Mean monthly air temperatures (°C) and precipitation (mm) during the 1988-89 and 1989-90 seasons are presented in Appendices 2 and 3, respectively. The data was provided by Environment Canada, Delta Ladner South Weather Station. In 1988-89 season, precipitation and temperatures were generally above the long-term mean values, however, February was colder and drier than normal, while March and May were quite wet. Although total precipitation was above normal in 1989-90, it was lower than in 1988-89, and September and October were rather dry, while April and June were wet. Temperatures were above normal. 4.2 1988-89 Experiment Analysis of variance tables for crop and soil parameters are presented in Appendices 4-21. Grain yields and some yield characteristics are shown in Table 4.1. Grain yield and most yield components were not influenced by seeding rate. The highest thousand grain weight (TGW), however, was obtained at the lowest seeding rate with added N , while without N grain weights were maximized at 250 seeds n r 2 (Figure 4.1). Grain yield and yield components, except for grains head"1, were sigrdficantly increased with N application over the control, however, time of N application had no significant effect (Table 4.1). Dry matter yield linearly increased with increasing seeding rate at GS 31, but at subsequent harvest dates there was no significant effect (Table 4.2). Nitrogen treatments had no significant effect on dry matter yield at GS 31. At GS 37, N application significantly increased dry matter yield over the control. 30 Table 4.1 Main effects of seeding rate and N treatments on grain yield and some yield characteristics in 1988-89 Seeds Grain Heads Grains Grains Harvest Grain m - 2 yield m"^  head-1 m"2 index protein (tha"1) (X103) (%) (%) 200 8.7 488 36 16.5 38.1 10.2 250 8.8 531 33 17.1 38.3 10.4 300 8.6 553 31 17.0 37.6 .9.9 Contrast Linear NS NS NS NS NS NS Quadratic NS NS NS NS NS NS N treatment NO 4.8 321 33 9.6 36.5 7.9 N l 10.2 548 ' 37 19.6 40.0 10.9 N2 9.9 610 31 18.9 38.1 10.8 N3 9.8 618 32 19.3 37.3 11.0 C V . (%) 11 12 27 9.1 5.4 5.8 Contrast NO vs N l + N2 + N3 ** ** NS ** ** ** N l vsN2 + N3 NS NS NS NS ** NS N2vsN3 NS NS NS NS NS NS *, ** = Significant at P <0.05 and P <0.01, respectively. NS = Not significant. CV. = Coefficient of variation. 31 Table 4.2 Main effects of seeding rate and N treatments on dry matter yields in 1988-89 Seeds n r 2 GS31 GS37 GS92 200 0.87 4.3 19.6 250 0.90 4.5 20.0 300 1.10 4.6 19.5 Contrast Linear * NS NS Quadratic NS NS NS N treatment NO 0.92 3.2 11.4 N l 0.92 4.4 22.1 N2 0.97 4.9 22.6 N3 1.00 5.4 22.8 C V . (%) 13 11 9.9 Contrast NO vs N l + N2 + N3 NS ** ** N l v s N 2 + N3 NS ** NS N2vsN3 NS * NS *, ** = Significant at P <0.05 and P <0.01, respectively. NS = Not significant. CV. = Coefficient of variation. 32 TGW (g) 50 rFigure 4.1 Interaction between seeding rate and N application for thousand grain weight in 1988-89 Moreover, delaying the first N application (treatment NI) until GS 31 significantly reduced dry matter yield compared with the average effect of treatments N2 and N3. Application of 50 kg N ha'1 at GS 22 (treatment N3) significantly increased dry matter yield at GS 37 compared with the appUcation of 25 kg N ha"1 (treatment N2). Time of N application had no significant effect on dry matter yield at final harvest (GS 92), however, N appUcation significantly increased dry matter yield over the control. Grain protein content was not significantly influenced by time of N application, nevertheless, N appUcation significantly increased it over the control (Table 4.1). Seeding rate had no significant effect on harvest index, but it was sigrrificantly increased over the control by N appUcation (Table 4.1). Treatment NI resulted in significantly higher harvest index compared with the average effect of treatments N2 and N3. 33 Nitrogen uptake linearly increased with increasing seeding rate at GS 31, but was not significantly affected at later harvest dates (Table 4.3). Nitrogen application significantly increased N uptake over the control at all harvest dates. Delaying the first N application until GS 31 (treatment NI) significantly limited N uptake at GS 31 and GS 37 compared with the average effect of treatments N2 and N3 which received 25 and 50 kg N ha - 1, respectively at GS 22, however, the differences diminished at GS 92 (Table 4.3). Application of 50 kg N ha"1 at GS 22 (treatment N3) significantly increased N uptake at GS 37 compared with the application of 25 kg N ha"1 (treatment N2). Disease incidence on the flag leaf, mainly leaf spot (Sevtoria triticf), was highest at the lower seeding rate without added N , while with N it was highest at 250 seeds n r 2 (Figure 4.2). DISEASE RATING 1.2 r0.6 0.8 -A 0.4 0.2 0 200 250 SEEDING RATE ( seeds ni 2 ) 300 ^- NO •e- N1+N2+N3 Figure 4.2 Interaction between seeding rate and N application for disease rating in 1988-89 34 Table 4.3 Main effects of seeding rate and N treatments on N uptake in 1988-89 Seeds m"2 GS 31 GS 37 kgNha' 1 GS 92 200 250 300 31 33 39 112 114 107 191 201 189 Contrast Linear Quadratic NS NS NS NS NS N treatment NO NI N2 N3 CV. (%) 28 30 37 41 18 44 118 130 152 19 78 232 227 241 15 Contrast NO vs NI + N2 + N3 NI vs N2 + N3 N2 vs N3 NS ** NS NS *, ** = Significant at P <0.05 and P <0.01, respectively. NS = Not significant. CV. = Coefficient of variation. 35 Seeding rate significantly influenced soil mineral N (NH 4 -N + NO3-N) at GS 31 (Table 4.4). More soil mineral N (0-50 cm) was recovered at the lower seeding rate compared with the medium and high seeding rates. This effect was not detected at later harvest dates. Nitrogen treatments had no significant effect on soil mineral N at GS 31 but at GS 37, it was significantly increased over the control with N application (Table 4.4). At final harvest (GS 92), treatment N3 significantly increased soil mineral N compared with treatment N2. Apparent crop recovery of N at GS 31 was higher with treatment N2 compared with treatment N3 (Table 4.5). At GS 37 and GS 92, recoveries with treatments N l , N2 and N3 were generally similar. Total recovery of applied N (crop + soil) at GS 31 was highest with treatment N2 compared with treatment N3. Nitrogen unaccounted for at GS 31 was 30 and 70% with treatments N2 and N3, respectively. At GS 37 and GS 92, total N recovered was higher with treatment N3. At final harvest (GS 92), total N recovered ranged from 66 to 78%. Low levels of mineral N , calculated by the difference method, remained in the top 0-50 cm of soil at the end of the season (0 to 6%). 4.3 1989-90 Experiment Analysis of variance tables for crop and soil parameters are presented in Appendices 22-49. The number of established plants and subsequent shoot (main stem + tillers) counts linearly increased with increasing seeding rate at all sampling dates except at 207 days after seeding (Figure 4.3). The maximum number of shoots was produced at the high seeding rate and was achieved earlier in the season, however, senescence of shoots started earlier at the high seeding rate. Time of N application had no significant effect on shoot production, nevertheless, N application enhanced shoot survival at 263 and 302 days after seeding compared with the control (Figure 4.4). 36 Table 4.4 Main effects of seeding rate and N treatments on soil N H 4 - N + NO3-N (0-50 cm) in 1988-89 Seeds n r 2 GS 31 GS 37 - kgNha"1 GS 92 200 250 300 Contrast Linear Quadratic N treatment NO N l N2 N3 C V . (%) Contrast NO vs N l + N2 + N3 N l vs N2 + N3 N2 vs N3 40 23 31 30 25 39 32 57 NS NS NS 62 40 41 NS NS 28 47 51 65 49 NS NS 32 34 39 NS NS 32 34 28 45 46 NS NS *, ** = Significant at P <0.05 and P <0.01, respectively. NS = Not significant. CV. = Coefficient of variation. Table 4.5 Balance of applied fertilizer N (%) in 1988-89 GS31 GS37 GS 92 N2 N3 Nl N2 N3 Nl N2 N3 Crop N recovery 34a 26 59 57 62 68 66 72 Soil N recovery 36 4 15 15 21 1 0 6 Total N recovered 70 30 74 72 83 69 66 78 N unaccounted for 30 70 26 28 17 31 34 22 a = By difference method. SHOOTS ( m -a) 2000 - 2 seeds m X •= 150 1500 0 = 300 * = 450 1000 500 0 J 1 L 4 0 71 131 207 235 DAYS AFTER SEEDING — i 1 263 302 Figure 4.3 Effect of seeding rate on shoot counts in 1989-90 Figure 4.4 Effect of N treatments on shoot counts in 1989-90 38 Grain yields and some yield characteristics are shown in Table 4.6. With increasing seeding rate; grain yield, harvest index and number of grains n r 2 were significantly reduced, while number of heads n r 2 and number of grains head'1 were not significantly affected. Time of N appUcation did not significantly influence grain yield, yield components and harvest index. Nitrogen appUcation, however, increased grain yield, yield components, harvest index and grain protein over the control. Moreover, delayed N (treatment NI) resulted in higher grain protein compared with the average effect of treatments N2 and N3. Grain yield was maximum at the lowest seeding rate with added N , but declined with increasing seeding rate (Figure 4.5). Grain yield response to increasing seeding rate without N was maximum at 300 seeds nr 2 . Interaction between seeding rate and nitrogen appUcation significantly influenced TGW. The highest TGW was attained at the lowest seeding with added N whUe without N , TGW was maximum at 300 seeds n r 2 (Figure 4.6). With increasing seeding rate, dry matter yield Unearly increased at GS 37 (Table 4.7). However, interaction between seeding rate and early N appUcation indicated that at the lowest seeding rate treatment N3 resulted in higher dry matter yield compared with treatment N2 whue at the two highest seeding rates there were no differences (Figure 4.7). Nitrogen appUcation significantly increased dry matter yields at all harvest dates. On the other hand, delaying the first N appUcation until GS 31 (treatment NI) significantly reduced dry matter yields at GS 37 and GS 69, however, the negative effect diminished at GS 85 and GS 92. At GS 69, dry matter yield was maximized at the high seeding rate with N appUcation, however, at GS 85 and GS 92 dry matter yields were maximized at the lowest seeding rate with added N (Table 4.8). Nitrogen uptake was not significantly influenced by seeding rate, however, N appUcation resulted in higher N uptakes over the control at all 39 Table 4.6 Main effects of seeding rate and N treatments on grain yield and some yield characteristics in 1989-90 Seeds m-2 Grain yield (t ha"i) Heads m Grains head"1 Grains m-2 (X103) Harvest index (%) Grain protein (%) 150 7.8 481 32.9 15.7 32.5 9.6 300 7.2 510 29.1 14.9 30.0 9.9 450 6.0 479 26.4 12.6 26.6 10.2 Contrast Linear ** NS NS ** ** NS Quadratic NS NS NS NS NS NS N treatment NO 4.2 371 24.7 8.9 26.3 7.6 N l 7.9 530 30.4 16.2 31.5 11.0 N2 8.1 529 31.6 16.5 30.9 10.6 N3 7.9 530 31.2 16.0 30.2 10.5 C V . (%) 19 14 16 17 11 6.1 Contrast NO vs N l + N2 + N3 ** ** ** ** ** ** N l vs N2 + N3 NS NS NS NS NS * N2 vs N3 NS NS NS NS NS NS *, ** = Significant at P <0.05 and P <0.01, respectively. NS = Not significant. CV. = Coefficient of variation. 40 Table 4.7 Main effects of seeding rate and N treatments on dry matter yields in 1989-90 Seeds nr* GS37 GS69 ^ GS85 GS92 150 5.4 300 5.9 450 7.1 Contrast Linear ** Quadratic NS N treatment NO 4.6 NI 6.3 N2 6.6 N3 7.1 C V . (%) 9.7 Contrast NO vs NI + N2 + N3 ** NI vs N2 + N3 * N2 vs N3 NS 13.9 18.4 20.5 14.5 18.9 20.5 15.0 17.8 19.2 NS NS NS NS NS NS 10.6 12.4 13.6 14.9 20.4 21.5 15.9 19.7 22.5 16.6 21.0 22.6 9.5 12 10 ** *» K-II-* NS NS NS NS NS *, ** = Significant at P <0.05 and P <0.01, respectively. NS = Not significant. CV. = Coefficient of variation. Table 4.8 Significant (P <0.05) interactions between seeding rate and N application for dry matter yields in 1989-90 GS69 GS85 GS92 Seeds m"2 NO N1+N2 + N3 NO N1+N2 + N3 NO N1+N2 + N3 t ha"l 150 300 450 cv. 8.7 11.0 12.1 15.7 15.6 16.0 10.2 13.6 13.4 21.1 20.6 19.3 12.1 14.7 14.0 23.3 22.4 20.9 41 GRAIN YIELD ( t ha 1) 10 r 4 ^ 150 300 SEEDING RATE ( seeds n i 2 ) NO N1+N2+N3 450 Figure 4.5 Interaction between seeding rate and N application for grain yield in 1989-90 TGW (g) 45 r 40 35 150 300 450 SEEDING RATE (seeds rrf 2 ) NO N1+N2+N3 Figure 4.6 Interaction between seeding rate and N application for thousand grain weight in 1989-90 42 DM ( t ha-i ) 150 300 450 SEEDING RATE ( seeds m"2) N2 N3 Figure 4.7 Interaction between N application and seeding rate for dry matter at GS 37 in 1989-90 harvest dates (Table 4.9). Delaying the first N application until GS 31 (treatment Nl) resulted in lower N uptake at GS 37 compared with the average effect of treatments N2 and N3 which received 25 and 50 kg N ha'1, respectively at GS 22. On the other hand, treatment N3 resulted in higher N uptake at GS 37 compared with treatment N2, while at GS 69 the opposite was true, however, at final harvest (GS 92), the two treatments did not significantly differ (Table 4.9). Neither seeding rate nor time of N application had any effect on disease incidence (Table 4.10). Nevertheless, N application significantly increased disease pressure on the head (Septoria nodorum), flag and penultimate leaves (Erysiphe graminis; Puccinia recondita; Septoria tritici) over the control. Although lodging was not rated, visual observations indicated that lodging and disease incidences were higher at the highest seeding rate with early N application. Lodging occurred in June due to heavy rains and windy conditions. 43 Table 4.9 Main effects of seeding rate and N treatments on N uptake in 1989-90 Seeds n r 2 GS37 GS69 GS85 GS92 kgNha*1  150 116 300 118 450 130 Contrast Linear NS Quadratic NS N treatment NO 53 NI 132 N2 141 N3 159 C V . (%) 14 Contrast NO vs NI + N2 + N3 NI vs N2 + N3 N2vsN3 182 183 209 173 184 209 180 183 192 NS NS NS NS NS NS 65 66 82 217 230 246 226 215 248 206 221 237 13 12 12 ** ** * NS NS NS * NS NS *, ** = Significant at P <0.05 and P <0.01, respectively. NS = Not significant. CV. = Coefficient of variation. 44 Table 4.10 Main effects of seeding rate and N treatments on disease incidence at GS 83 in 1989-90 Seeds n r 2 Head Flag leaf Penultimate leaf 150 0.5 1.1 1.6 300 0.5 1.0 1.6 450 0.3 1.0 1.6 Contrast • Linear NS NS NS Quadratic NS NS NS N treatment NO 0.2 0.3 0.3 N l 0.5 1.1 2.0 N2 0.6 1.3 2.1 N3 0.5 1.2 2.0 C V . (%) 48 28 30 Contrast NO vs N l + N2 + N3 ** ** ** N l vs N2 + N3 NS NS NS N2 vs N3 NS NS NS *, ** = Significant at P <0.05 and P <0.01, respectively. NS = Not significant. CV. = Coefficient of variation. 45 Soil mineral N (NH 4 -N + NO3-N) was not influenced by seeding rate at any sampling date (Table 4.11). At all harvest dates, nitrogen application resulted in significantly higher soil mineral N than the control. Delaying the first N application until GS 31 (treatment NI) resulted in more soil mineral N at GS 37 than treatments N2 and N3 which received N at GS 22. Crop N recoveries at GS 37, GS 69 and GS 85 were generally similar and ranged from 59 to 73% (Table 4.12). Total N recovered (crop + soil) was generally higher with treatment NI especially at GS 37. Total N recovered at GS 85 ranged from 71 to 79%. Although soil samples were not taken at final harvest (GS 92), it can be inferred from GS 85 data that low levels of mineral N , as calculated by the difference method, remained in the top 0-50 cm of soil at the end of the season. 46 Table 4.11 Main effects of seeding rate and N treatments on soil N H 4 - N + N O 3 - N (0-50 cm) in 1989-90 Seeds n r 2 GS 37 GS69 kg N ha"1 GS85 150 300 450 25 34 30 15 15 16 20 19 31 Contrast Linear Quadratic N treatment NO N l N2 N3 C V . (%) Contrast NO vs N l + N2 + N3 N l vs N2 + N3 N2vsN3 NS NS 18 40 30 31 41 NS NS NS 6 20 19 15 44 NS NS NS NS 14 27 26 27 60 NS NS *, ** = Significant at P <0.05 and P <0.01, respectively. NS = Not significant. CV. = Coefficient of variation. Table 4.12 Balance of applied fertilizer N (%) in 1989-90 GS37 GS69 GS85 Nl N2 N3 Nl N2 N3 Nl N2 N3 Crop N recovery 63a 59 61 68 72 63 73 66 69 Soil N recovery 18 8 7 6 6 4 6 5 6 Total N recovered 81 67 68 74 78 67 79 71 75 N unaccounted for 19 33 32 26 22 33 21 29 25 a = By difference method. 47 5.0 DISCUSSION The number of established plants linearly increased with increasing seeding rate in 1988-89, but subsequent shoot (main stem + tillers) counts taken at several intervals during the course of the season were not significantly influenced (Schmidt, 1989). In 1989-90, number of established plants and shoot counts responded positively to increasing seeding rate at all sampling dates except at 207 days after seeding. Schmidt (1989) attributed the lack of shoot response in 1988-89 to compensation through tillering. In 1989-90, however, the range of seeding rates was expanded and consequently tillering could not fully compensate for the differences in shoot numbers even though more tillers per plant were produced at the lower seeding rate. Darwinkel (1978) reported a 12-fold increase in number of tillers in response to a 160-fold increase in plant density and attributed the small magnitude of response to abundant tillering at the lower plant densities. McLaren (1981) found similar results. Winter wheat (Triticum aestivum L.), therefore, exhibits tremendous tillering capacity which acts as an insurance factor against yield loss under unfavourable growth conditions such as poor seedbed or severe winters. Although maximum number of shoots were produced at the high seeding rate (1793 shoots nr 2) and were attained earlier in the season, shoot senescence started earlier. Darwinkel (1978) and McLaren (1981) reported similar findings and they attributed it to intense interplant competition for environmental resources. With increasing seeding rates, the space per plant diminishes and consequently interplant competition sets in earlier than at the lower seeding rates. On the other hand, intraplant competition occurs later at the lower seeding rates due to continued tillering per plant. 48 The effect of N on shoot production was not determined in 1988-89. However, in 1989-90 time of N application had no significant effect on shoot production. Nevertheless, N application enhanced shoot survival at 263 and 302 days after seeding but not at 235 days after seeding probably due to the short interval between N application and the sampling date. Bremner (1969) and Darwinkel (1983) reported increased tiller production with early N application contrary to the findings of the present study. The short interval (11 days) between the early N (GS 22) and the main N (GS 31) applications could be the reason why delaying the initial N application until GS 31 did not significantly reduce the number of shoots nr 2 . McLaren (1981) reported similar findings in one of two seasons and attributed it to high residual N. In 1988-89, interaction between seeding rate and N application significantly influenced disease incidence. With added N, disease was lowest at the 200 seeds n r 2 rate while it was highest at the 250 seeds n r 2 rate. On the other hand, without added N disease severity was highest at the lower seeding rate and declined with increasing seeding rate. The results should be interpreted with caution due to the fact that at the time of disease assessment most leaf tissues in the control plots had senesced. Nevertheless, a decrease in powdery mildew (Erysiphe graminis) severity with increasing seeding rate has been reported elsewhere (Broscious et al., 1985). The authors speculated that it could have been due to vigorous growth at the low seeding rate because of reduced interplant competition for light, water and nutrients. Glynne (1951) reported increased incidence of eyespot (Cercosporella herpotrichoides) and take-all (Gaeumannomyces graminis) with increasing seeding rate. Generally, high seeding rates provide an ideal microclimate (dense canopy and high moisture) for disease infection which may have been the case in the present study where with 49 added N, disease incidence was highest at the 250 seeds n r 2 rate. By and large, disease pressure was not a major factor in 1988-89 and on a scale of 0-4, the highest rating was 1. In 1989-90, neither seeding rate nor time of N appUcation significantly influenced disease incidence, however, N appUcation increased disease severity over the control. Reports elsewhere indicate that delaying N application retards disease infection (Darwinkel, 1980a, 1980b; Prew et al., 1985). Disease was more of a factor in 1989-90 than in 1988-89 and on a scale of 0-4, disease ratings ranged from 0.2 to 2.1. It is not certain why seeding rate and time of N appUcation did not significantly influence disease incidence and yet visual observations indicated that high seeding rate coupled with early N application resulted in more disease. It must be noted, however, that disease stress was mostly on lower leaves and tillers, while quantitative disease assessments were confined to the upper leaves plus the head. The predominant diseases in 1988-89 were leaf spot (Septoria tritici), glume blotch (Septoria nodorum) and leaf rust (Puccinia recondita), whUe in 1989-90 they were powdery mildew (Erysiphe graminis), leaf rust (Puccinia recondita), eyespot (Cercosporella herpotrichoides), glume blotch (Septoria nodorum) and leaf spot (Septoria tritici). Grain yield, number of heads nr 2 , number of grains head"1 and number of grains n r 2 were not significantly influenced by seeding rate in 1988-89, however, in 1989-90 grain yield and number of grains n r 2 decreased with increasing seeding rate, whUe number of heads n r 2 and number of grains head"1 were not significantly affected. In both seasons, interaction between seeding rate and N application significantly influenced TGW. Maximum TGW was achieved at the low seeding rate with added N , while without added N it was maximized at the medium seeding rate. Darwinkel et al. (1977) found that with early seeding, grain yield was not significantly influenced by seeding rate. Similarly, Johnson 50 et al (1988) reported that when averaged over seasons, grain yield was not significantly affected by seeding rate. Darwinkel (1978) reported only a 3-fold increase in grain yield with a 160-fold increase in plant density, whereas Frederick and Marshall (1985) found significant increases in grain yield with increasing seeding rate at 3 out of 8 sites. Number of heads n r 2 have been reported to increase with increasing seeding rate (Darwinkel et al., 1977; Darwinkel, 1978; Smid and Jenkinson, 1979; Johnson et al, 1988), while number of grains head"1 have been reported to decrease with increasing seeding rate (Darwinkel et al, 1977; Darwinkel, 1978; Smid and Jenkinson, 1979; Frederick and Marshall, 1985; Johnson et al, 1988). Grain weight responses to seeding rate are generally variable. For instance, Darwinkel et al (1977) reported significant decreases in grain weight with increasing seeding rate, while Darwinkel (1978) reported maximum grain weight at 50 plants n r 2 and reductions with further increases in seeding rate reduced it. On the other hand, both Frederick and Marshall (1985) in 6 out of 8 sites and Johnson et al. (1988) reported increases in grain weight with increasing seeding rate. Grain yield and yield components were not significantly influenced by seeding rate in 1988-89, probably due to the narrow range of seeding rates used. Considering that there were no differences in number of shoots nr 2 , compensation occurred largely through tillering. At the same time, compensation occurred through TGW which was maximized at the low seeding rate with added N. In 1989-90, however, interaction between seeding rate and N application showed that grain yield was maximized at the lower seeding rate with added N. The decrease in grain yield with increasing seeding rate was due to the decrease in number of grains n r 2 and TGW probably as a result of interplant competition and lodging. According to Darwinkel et al (1977) and 51 Darwinkel (1978), interplant competition reduces the number of spikelets, the number of fertile spikelets, the number of grains per spikelet and ultimately the number of grains per head. At high seeding rates, TGW is lowered because increased interplant competition restricts the supply of photosynthates required for grain filling (Darwinkel, 1978). In the present study, however, lodging and disease pressure also played a significant role. Although the number of grains head"1 decreased with increasing seeding rate, the effect was not statistically significant. As in 1988-89, TGW was highest at the lower seeding rate with added N. Time of N application did not significantly influence grain yield and yield components in either season. However, with N application, they were significantly increased over the control in both years except for the number of grains head"1 in 1988-89. Bremner (1969) reported a 5% increase in grain yield with delayed N application, however, the number of heads m"2 decreased, while the number of grains head"1 and grain weight were increased. The superiority of late N appUcation was attributed to more disease, lodging and weeds where N was applied early. Elsewhere, lack of grain yield response to time of N application has been attributed to high residual N (McLaren, 1981). Bomke and Temple (1989) reported significant positive grain yield response to spUt application of N, with first N applied at GS 22, at only 1 out of 4 sites. The lack of response to time of N appUcation in the current study may be related to the total N appUed. The effects of time of N application might have been different at a lower rate of N than 225 kg N ha"1. It is noteworthy, however, that in early spring residual N is quite low due to winter leaching, and crop demand is high as reflected by the high crop N. recoveries. 52 Dry matter yields linearly increased with increasing seeding rate at GS 31 in 1988-89 and GS 37 in 1989-90, however, at subsequent harvest dates dry matter yields were not significantly different. The results are consistent with the findings of Puckridge and Donald (1967). The linear responses at GS 31 and GS 37 can be attributed to more shoots nr 2 , while the lack of response at later harvest dates could be due to tiller mortality as a result of interplant competition at the high seeding rate. At GS 37, in 1989-90, the increase in dry matter yield at the lowest seeding rate with N3 compard with N2 could be relevant to forage production even though it did not translate into increased grain yields. Delaying the first N application until GS 31 significantly reduced dry matter yields at GS 37 in both seasons, as well as at GS 69 in 1988-89 in agreement with the findings of Ellen and Spiertz (1980) and Prew et al. (1986). A delay of N application hampers tiller production, consequently leading to fewer shoots nr 2 . With added N , dry matter yields decreased with increasing seeding rate at GS 85 and GS 92 in 1989-90 probably due to lodging and disease pressure. Visual observations indicated that lodging occurred mainly at the highest seeding rate with added N . Harvest index was not significantly influenced by seeding rate in 1988-89 as was found by Sharma and Smith (1987), however, harvest index significantly decreased with increasing seeding rate in 1989-90 consistent with the findings of McLaren (1981). Darwinkel (1978) reported maximum harvest index at 50 plants n r 2 rate and further increases in plant density resulted in lower harvest indices. Interplant competition and lodging are thought to be responsible for the decreased harvest index over the control in both seasons. On the other hand, delaying the first N application until GS 31 (treatment Nl) resulted in maximum harvest index in 1988-89 in agreement with the findings of Ellen and Spiertz 53 (1980), McLaren (1981), Darwinkel (1983) and Prew et al (1985, 1986). The delayed N probably contributed to more grain than foliage production since harvest index is a ratio of grain to total above-ground yield. In 1988-89, N uptake linearly increased with increasing seeding rate at first harvest (GS 31) but not at subsequent harvest dates in close agreement with the findings of Puckridge and Donald (1967). In 1989-90, however, seeding rate had no significant effect on N uptake at any harvest date with the first harvest occurring at GS 37. The significant effect early in the season in 1988-89 could be due to more root biomass available for uptake at the higher seeding rate. Although appUed N increased N uptake at all harvest dates in both seasons, delaying the first N application until GS 31 Umited N uptake at GS 31 in 1988-89 and at GS 37 in both seasons. However, crop N recoveries at GS 37 were rather comparable, ranging from 57 to 61% in 1988-89 and from 61 to 63% in 1989-90. Although the appUcation of 25 and 50 kg N ha'1 at GS 22 in 1988-89 did not result in significant differences in N uptake at GS 31, crop N recovery was higher with 25 kg N ha"1, which suggests that 50 kg N ha"1 may be more than the crop demand early in the season. Crop N recoveries at the end of both seasons ranged from 66-73% and were higher than those reported by other workers, 56% (Stanford and Hunter, 1973), 44-57% (Olson et al, 1978), 45% (Cleemput et al, 1981), 53-67% (Cleemput and Baert, 1984), 18-60% 0anzen et al, 1991). Baethgen and Alley (1989a) reported higher N uptakes where N was appUed as a single application at GS 30 compared with that appUed at GS 25 under wet conditions. The period for rapid N uptake for winter wheat starts at GS 30. Applied N increased grain protein over the control in both seasons. Moreover, in 1989-90 delaying the first N application until GS 31 (treatment NI) significantly increased grain protein compared with the average effects of 54 treatments N2 and N3 which received first N at GS 22. The superiority of treatment NI is consistent with the findings of both Hucklesby et al (1971) and Fowler and Brydon (1989). It is noteworthy, however, that treatment NI received 100 kg N ha'1 at GS 37, while treatments N2 and N3 received 75 and 50 kg N ha"1, respectively. The results suggest that N appUed later in the season is accumulated in the grain where it is utiUzed in protein synthesis. At the low seeding rate, more soil mineral N was measured at GS 31 in 1988-89 probably due to fewer roots available for uptake. Alternatively, less leaf area may have reduced the transpiration rate consequently slowing down N transport through mass flow. On the other hand, N appUcation significantly increased soil mineral N over the control only at GS 37 in 1988-89 and at aU harvest dates in 1989-90. Delaying the first N application until GS 31 resulted in significantly more soU mineral N at GS 37 in 1989-90 most Ukely due to less potential for losses as weU as limited time for crop uptake compared to N applied earUer (GS 22). However, the variabUity in soil data was quite high (cv. ranged from 41 to 61%) and the results should be interpreted cautiously. Total N recoveries at final harvest (GS 92) in 1988-89 and at GS 85 in 1989-90 were quite high and comparable to those reported by Olson et al. (1979). Nevertheless, soil N recoveries in the present study were fairly low compared with those reported by Olson et al (1979). Whereas Olson et al (1979) attributed unaccounted N to denitrification, Kowalenko (1987, 1989) reported negUgible denitrification and minimal leaching losses in the Lower Fraser Valley where the present study was located. However, Kowalenko (1989b) mentioned the occurrence of microbial immobilization and N H 4 fixation. The present study did not take into account N contained in the non-harvested roots. 55 6.0 CONCLUSIONS Based on the study, several points can be made about the response of winter wheat (Triticum aestivum L.) and soil mineral N contents to seeding rate and time of N application in south coastal British Columbia: 1. Winter wheat has a tremendous capacity to make compensatory growth through changes in yield components in response to variable seeding rates. 2. Although more shoots were produced at the highest seeding rates, shoot mortality was higher due to interplant competition. 3. Seeding rate did not influence grain yield and its components in 1988-89. 4. The decrease in grain yield with increasing seeding rate in 1989-90 was due to decreased number of grains n r 2 and TGW. 5. Dry matter yields at GS 31 increased linearly with increasing seeding rate in 1988-89 and at GS 37 in 1989-90 due to the presence of more shoots nr 2 . At the lowest seeding rate, however, dry matter yield increased with N3 compared with N2 at GS 37 in 1989-90. 6. Harvest index decreased with increasing seeding rate in 1989-90 due to decreased grain yield. 7. Nitrogen uptake linearly increased with increasing seeding rate at GS 31 in 1988-89 probably due to more roots available for uptake and/or increased N transport by mass flow in response to greater transpiration with more leaf area, however, at later harvest dates the effect was not detected. 8. Time of N application did not influence grain yield and yield components in either season. However, N application significantly increased grain 56 yield, yield components, harvest index, N uptake and grain protein over the control. 9. Delaying the first N application until GS 31 significantly reduced dry matter yields at GS 37 in either season and at GS 69 in 1989-90. Similarly, the same treatment resulted in reduced N uptake at GS 31 in 1988-89 and at GS 37 in either season. On the other hand, the delay in N application significantly increased harvest index in 1988-89 and grain protein in 1989-90. 10. Without N , disease pressure was high at the low seeding rate in 1988-89, while N application increased disease incidence over the control in 1989-90. 11. Nitrogen application significantly increased soil mineral N at GS 37 in 1988-89 and throughout the growth period in 1989-90. However, low levels of mineral N , as calculated by the difference method, remained in the soil at the end of either season regardless of the timing of N application. 57 7.0 RECOMMENDATIONS To recommend specific seeding rate and N management practices for south coastal British Columbia based on a two year study at one site may not be realistic. However, the study provided some information relevant to the Delta area and by inference to other areas in the region. Even though in 1989-90 highest grain yield was achieved at 150 seeds m~2 rate, a seeding rate of 300 seeds n r 2 is recommended for Delta and areas around the Strait of Georgia with similar soils in order to avoid risks due to unfavourable seedbed, weed infestation, inadequate soil cover and adverse weather conditions. Considering that TGW varied from 39 to 46 g, seeding rate calculations should take into account TGW as well as seed viability and preferably expressed as seeds nr 2 . Time of N appUcation was not a major factor influencing grain yield and, in fact, delaying the first N application until GS 31 did not appear to affect grain yield despite the N deficiency symptoms observed in early spring. The eUmination of the early N appUcation (GS 22) would result in the reduction of field operations when soUs may not be trafficable. Assuming 225 kg N ha"1 is the appropriate rate, a two-way split appUcation of N , 125 kg N ha"1 at GS 31 + 100 kg N ha"1 at GS 37 is recommended espedaUy if the crop is grown for milUng purposes. However, observed factors such as low plant population, weediness or poor drainage, suggesting a lower yield potential should cause the rate of N application to be adjusted downwards. By inference, a lower seeding rate may be adequate for the Eastern Fraser Valley because of severe disease and lodging incidences. Conversely higher seeding rate is suggested for Oyster River or Sumas Prairie when droughty conditions are experienced in these areas at seeding time. 58 8.0 LITERATURE CITED Altaian, D.W., W.L. McCuistion, and W.E. Kronstad. 1983. Grain protein percentage, kernel hardness, and grain yield of winter wheat with foliar applied urea. Agron. J. 75:87-91. Baethgen, W.E., and M.M. Alley. 1989a. Optimizing soil and fertilizer nitrogen use by intensively managed winter wheat. I. Crop nitrogen uptake. Agron. J. 81:116-120. Baethgen, W.E., and M.M. Alley. 1989b. Optimizing soil and fertilizer nitrogen use by intensively managed winter wheat. II. Critical levels and optimum rates of nitrogen fertilizer. Agron. J. 81:120-125. Batey, T. 1976. Some effects of nitrogen fertilizer on winter wheat. J. Sci. Fd. Agric. 27:287-297. Bomke, A.A. 1990. Intensive wheat management in south coastal British Columbia. In Proceedings: Mey Wheat Management Conerence, Denver, Colorado, March 7-9,1990. pp. 8-14. 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Appendix 1: Some chemical properties of composite soil samples taken from control plots in early spring 1988-89 1989-90 Soil parameter 0-20 20-50 0-20 20-50 depth (cm) depth (cm) pH (H20) 5.9 5.9 6.7 5.8 Organic matter (%) 4.3 3.3 4.0 3.0 Nitrate-N (kg ha"1) 62 59 18 19 Phosphorus (kg ha"1) 233 39 136 58 Potassium (kg ha"1) 543 284 499 336 Magnesium (kg ha"1) 236 616 447 645 Calcium (kg ha"1) 2742 2874 4598 3782 Sodium (kg ha"1) 24 82 90 136 Sulphate-sulphur (kg ha"1) 65 80 85 130 68 Appendix 2: Mean monthly air temperatures (°C) and precipitation (mm) during the 1988-89 growing season compared with the mean data for the 1951-1980 period Precipitation (mm) Month 1951-80 1988-89 Deviation from mean Temperature (°C) 1951-80 1988-89 Deviation from mean September 51.7 86.2 +34.5 14.1 14.1 0.0 October 93.2 109.8 +16.6 9.8 11.0 +1.2 November 127.3 212.4 +85.1 5.8 7.1 +1.3 December 137.9 177.5 +39.6 3.6 4.5 +0.9 January 118.2 124.0 +5.8 2.4 3.6 +1.2 February 92.1 62.5 -29.6 4.6 0.5 -4.1 March 69.4 123.2 +53.8 6.0 5.9 -0.1 April 47.2 41.3 -5.9 8.8 10.9 +2.1 May 38.8 84.2 +45.4 12.4 12.9 +0.5 June 39.9 56.6 +16.7 15.1 15.6 +0.5 July 26.0 31.7 +5.7 17.1 16.7 -0.4 August 37.3 49.2 +11.9 16.8 16.7 -0.1 Appendix 3: Mean monthly air temperatures (°C) and precipitation (mm) during the 1989-90 growing season compared with the mean data for the 1951-1980 period Precipitation (mm) Temperature (°C) Month 1951-80 1989-90 Deviation 1951-80 1989-90 Deviation from mean from mean September 51.7 13.2 -38.5 14.1 15.5 +1.4 October 93.2 59.2 -34.0 9.8 11.0 +1.2 November 127.3 179.4 +52.1 5.8 7.7 +1.9 December 137.9 115.6 -22.3 3.6 5.8 +2.2 January 118.2 150.6 +32.4 2.4 5.6 +3.2 February 92.1 82.4 -9.7 4.6 4.0 -0.6 March 69.4 67.2 -2.2 6.0 7.2 +1.2 April 47.2 86.1 +38.9 8.8 10.9 +2.1 May 38.8 54.2 +15.4 12.4 12.8 +0.4 June 39.9 81.4 +41.5 15.1 15.2 +0.1 July 26.0 4.8 -21.2 17.1 18.7 +1.6 August 37.3 37.2 -0.1 16.8 18.6 +1.8 69 Appendix 4: Analysis of variance for dry matter yield at GS 31 in 1988-89 Source of variation df MS F-value Probability Block 3 0.51396 8.4663 0.014 Seeding Rate 2 0.24359 4.0126 0.078 Linear 1 0.407252 6.7086 0.041 Quadratic 1 0.799258E-1 1.3166 0.295 Error (a) 6 0.60706E-1 Nitrogen 3 0.17214E-1 1.0918 0.369 NO vs N l + N2 + N3 1 0.164697E-1 1.0446 0.316 N l vsN2 + N3 1 0.316682E-1 2.0086 0.168 N2vsN3 1 0.350416E-2 0.22226 0.641 Interaction 6 0.11695E-1 0.74179 0.621 Lin. * (NO vs N l + N2 + N3) 1 0.510322E-4 0.32368E-2 0.955 Quad. * (NO vs N l + N2 + N3) 1 0.420045E4 0.26642E-2 0.959 Lin. *(NlvsN2 + N3) 1 0.208164E-5 0.13203E-3 0.991 Quad. * (Nl vs N2 + N3) 1 0.626725E-2 0.39751 0.534 Lin. *(N2vsN3) 1 0.473063E-1 3.0005 0.095 Quad. * (N2 vs N3) 1 0.165022E-1 1.0467 0.315 Error (b) 27 0.15766E-1 Appendix 5: Analysis of variance for dry matter yield at GS 37 in 1988-89 Source of variation df MS F-value Probability Block 3 2.5323 4.5819 0.054 Seeding Rate 2 0.21681 0.39229 0.692 Linear 1 0.418613 0.75744 0.418 Quadratic 1 0.150003E-1 0.27142E-1 0.875 Error (a) 6 0.55267 Nitrogen 3 10.213 41.091 0.000 N0vsNl+N2 + N3 1 24.9917 100.55 0.000 N l vsN2 + N3 1 4.45014 17.905 0.000 N2vsN3 1 1.19707 4.8163 0.037 Interaction 6 0.288 1.1587 0.357 Lin. * (NO vs N l + N2 + N3) 1 0.770445E-2 0.30998E-1 0.862 Quad. * (NO vs N l + N2 + N3) 1 0.888912E-2 0.35765E-1 0.851 Lin. *(NlvsN2 + N3) 1 0.184084E-1 0.74065E-1 0.788 Quad. * (Nl vs N2 + N3) 1 0.411731 1.6566 0.209 Lin. *(N2vsN3) 1 0.722517E-2 0.2907E-1 0.866 Quad.*(N2vsN3) 1 1.27401 5.1259 0.032 Error (b) 27 0.24854 70 Appendix 6: Analysis of variance for dry matter yield at GS 92 in 1988-89 Source of variation df MS F-value Probability Block 3 5.3601 0.83292 0.523 Seeding Rate 2 0.80326 0.12482 0.885 Linear 1 0.114022 0.17718E-1 0.898 Quadratic 1 1.49244 0.23192 0.647 Error (a) 6 6.4353 Nitrogen 3 372.37 98.93 0.000 N0vsNl + N2 + N3 1 1114.28 296.04 0.000 N l vsN2 + N3 1 2.45689 0.65274 0.426 N2 vs N3 1 0.370027 0.98307E-1 0.756 Interaction 6 2.3795 0.63218 0.703 Lin. * (NO vs N l + N2 + N3) 1 0.520686 0.13833 0.713 Quad. * (NO vs N l + N2 + N3) 1 6.9409 1.844 0.186 Lin. * (Nl vs N2 + N3) 1 0.420012 0.11159 0.741 Quad.*(Nl vsN2 + N3) 1 2.65415 0.70514 0.408 Lin. * (N2 vs N3) 1 3.48759 0.92657 0.344 Quad. *(N2vsN3) 1 0.25376 0.67418E-1 0.797 Error (b) 27 3.764 Appendix 7: Analysis of variance for N uptake at GS 31 in 1988-89 Source of variation df MS F-value Probability Block 3 610.18 6.9657 0.022 Seeding Rate 2 288 3.2878 0.109 Linear 1 547.392 6.2489 0.047 Quadratic 1 28.6127 0.32664 0.588 Error (a) 6 87.598 Nitrogen 3 448.02 11.864 0.000 NO vs N l + N2 + N3 1 540.601 14.315 0.001 N l vsN2 + N3 1 686.6 18.181 0.000 N2vsN3 1 116.865 3.0946 0.090 Interaction 6 38.73 1.0256 0.430 Lin. *(N0vsNl + N2 + N3) 1 26.9982 0.71492 0.405 Quad. * (NO vs N l + N2 + N3) 1 0.562671 0.149E-1 0.904 Lin. *(NlvsN2 + N3) 1 2.2707 0.60129E-1 0.808 Quad.*(NlvsN2 + N3) 1 73.6452 1.9501 0.174 Lin. * (N2 vs N3) 1 64.6415 1.7117 0.202 Quad.*(N2vsN3) 1 64.2644 1.7017 0.203 Error (b) 27 37.764 71 Appendix 8: Analysis of variance for N uptake at GS 37 in 1988-89 Source of variation df MS F-value Probability Block 3 1732.4 7.668 0.018 Seeding Rate 2 180.23 0.79774 . 0.493 Linear 1 147.576 0.6532 0.450 Quadratic 1 212.89 0.94229 0.369 Error (a) 6 225.93 Nitrogen 3 26137 58.913 0.000 N0vsNl+N2 + N3 1 71423.9 160.99 0.000 NI vsN2 + N3 1 4161 9.379 0.005 N2vsN3 1 2825.13 6.3679 0.018 Interaction 6 379.61 0.85565 0.539 Lin. *(N0vsNl + N2 + N3) 1 25.0105 0.56374E-1 0.814 Quad. * (NO vs NI + N2 + N3) 1 14.7427 0.3323E-1 0.857 Lin. *(NlvsN2 + N3) 1 44.5062 0.10032 0.754 Quad. * (NI vs N2 + N3) 1 54.2438 0.12227 0.729 Lin. * (N2 vs N3) 1 382.007 0.86105 0.362 Quad. + (N2 vsN3) 1 1757.16 3.9607 0.057 Error (b) 27 443.65 Appendix 9: Analysis of variance for N uptake at GS 92 in 1988-89 Source of variation df MS F-value Probability Block 3 1884.7 1.0538 0.435 Seeding Rate 2 655.89 0.36672 0.708 Linear 1 39.4495 0.22057E-1 0.887 Quadratic 1 1272.32 0.71139 0.431 Error (a) 6 1788.5 Nitrogen 3 72435 81.677 0.000 N0vsNl+N2 + N3 1 215854 243.39 0.000 NI vs N2 + N3 1 19.6365 0.22142E-1 0.883 N2vsN3 1 1430.36 1.6129 0.215 Interaction 6 501.5 0.56548 0.754 Lin. *(N0vsNl + N2 + N3) 1 19.3952 0.2187E-1 0.884 Quad. * (NO vs NI + N2 + N3) 1 187.519 0.21145 0.649 Lin. *(NlvsN2 + N3) 1 1520.66 • 1.7147 0.201 Quad. * 0N1 vs N2 + N3) 1 365.157 0.41175 0.526 Lin. *(N2vsN3) 1 5.60509 0.63202E-2 0.937 Quad.*(N2vsN3) 1 910.635 1.0268 0.320 Error 0>) 27 886.85 72 Appendix 10: Analysis of variance for soil NH4 -N + NO3-N (0-50 cm) at GS 31 in 1988-89 Source of variation df MS F-value Probability Block 3 414.12 3.8401 0.076 Seeding Rate 2 1204.9 11.173 0.009 Linear 1 654.677 6.0708 0.049 Quadratic 1 1755.15 16.275 0.007 Error (a) 6 107.84 Nitrogen 3 372.66 1.1632 0.342 N0vsNl + N2 + N3 1 45.2813 0.14134 0.710 Nl vsN2 + N3 1 829.806 2.5901 0.119 N2vsN3 1 242.888 0.75813 0.392 Interaction 6 592.59 1.8496 0.127 Lin. * (NO vs Nl + N2 + N3) 1 1072.94 3.349 0.078 Quad. * (NO vs Nl + N2 + N3) 1 69.6986 0.21755 0.645 Lin. *(NlvsN2 + N3) 1 1206.61 3.7662 0.063 Quad. * (Nl vs N2 + N3) 1 65.9616 0.20589 0.654 Lin. *(N2vsN3) 1 1078.47 3.3662 0.078 Quad. * (N2 vs N3) 1 61.8351 0.19301 0.664 Error (b) 27 320.38 Appendix 11: Analysis of variance for soil NH4 -N + NO3-N (0-50 cm) at GS 37 in 1988-89 Source of variation df MS F-value Probability Block 3 1698.9 1.6639 0.272 Seeding Rate 2 2427.1 2.3771 0.174 Linear 1 3534.94 3.462 0.112 Quadratic 1 1319.35 1.2921 0.299 Error (a) 6 1021.1 Nitrogen 3 2936.9 5.2575 0.005 NO vs Nl + N2 + N3 1 6579.1 11.778 0.002 Nl vs N2 + N3 1 995.845 1.7827 0.193 N2vsN3 1 1235.68 22121 0.149 Interaction 6 423.72 0.75853 0.609 Lin. *(N0vsNl + N2 + N3) 1 88.2625 0.15801 0.694 Quad. * (NO vs Nl + N2 + N3) 1 19.3804 0.34694E-1 0.854 Lin. *(NlvsN2 + N3) 1 373.749 0.66908 0.421 Quad. * (Nl vs N2 + N3) 1 6.89939 0.12351E-1 0.912 Lin. *(N2vsN3) 1 565.726 1.0127 0.323 Quad.*(N2vsN3) 1 1488.31 2.6643 0.114 Error fl>) 27 558.6 73 Appendix 12: Analysis of variance for soil NH4 -N + NO3-N (0-50 cm) at GS 92 in 1988-89 Source of variation df MS F-value Probability Block 3 615.79 3.3386 0.097 Seeding Rate 2 222.14 1.2044 0.363 Linear 1 425.882 2.309 0.179 Quadratic 1 18.3923 0.99717E-1 0.763 Error (a) 6 184.44 Nitrogen 3 673.64 2.6539 0.069 N0vsNl+N2 + N3 1 127.464 0.50216 0.485 NI vsN2 + N3 1 49.9997 0.19698 0.661 N2 vsN3 1 1843.46 7.2626 0.012 Interaction 6 106.68 0.42028 0.859 Lin. *(N0vsNl + N2 + N3) 1 249.293 0.98213 0.330 Quad. * (NO vs NI + N2 + N3) 1 96.119 0.37868 0.543 Lin. * (NI vs N2 + N3) 1 23.3243 0.9189E-1 0.764 Quad. * (NI vs N2 + N3) 1 8.64358 0.34053E-1 0.855 Lin. *(N2vsN3) 1 137.828 0.54299 0.468 Quad.*(N2vsN3) 1 124.872 0.49195 0.489 Error (b) 27 253.83 Appendix 13: Analysis of variance for grain yield in 1988-89 Source of variation df MS F-value Probability Block 3 0.46526 0.60078 0.638 Seeding Rate 2 0.26978 0.34836 0.719 Linear 1 0.621285E-1 0.80225E-1 0.787 Quadratic 1 0.477399 0.61645 0.462 Error (a) 6 0.77443 Nitrogen 3 81.945 97.89 0.000 N0vsNl + N2+N3 1 244.818 292.46 0.000 NI vsN2 + N3 1 0.920259 1.0993 0.304 N2vsN3 1 0.962658E-1 0.115 0.737 Interaction 6 0.84063 1.0042 0.443 Lin. *(N0vsNl+N2 + N3) 1 0.128344E-1 0.15332E-1 0.902 Quad. * (NO vs NI + N2 + N3) 1 2.07911 2.4837 0.127 Lin. *(NlvsN2 + N3) 1 0.621074 0.74192 0.397 Quad.*(NlvsN2 + N3) 1 2.11216 25232 0.124 Lin. *(N2vsN3) 1 0.2116 0.25277 0.619 Quad. * (N2 vs N3) 1 0.700755E-2 0.83711E-2 0.928 Error (b) 27 0.83711 74 Appendix 14: Analysis of variance for thousand grain weight in 1988-89 Source of variation df MS F-value Probability Block 3 19.833 1.6299 0.279 Seeding Rate 2 11.551 0.94923 0.438 Linear 1 13.9126 1.1433 0.326 Quadratic 1 9.18841 0.7551 0.418 Error (a) 6 12.168 Nitrogen 3 22.165 3.9481 0.019 NO vs NI + N2 + N3 1 50.4101 8.9792 0.006 NI vs N2 + N3 1 1.20123 0.21397 0.647 N2vsN3 1 14.884 2.6512 0.115 Interaction 6 14.877 2.65 0.038 Lin. *(N0vsNl + N2 + N3) 1 29.8152 5.3108 0.029 Quad. * (NO vs NI + N2 + N3) 1 35.4902 6.3216 0.018 Lin. * (NI vs N2 + N3) 1 8.25029 1.4696 0.236 Quad. * (NI vs N2 + N3) 1 8.85063 1.5765 0.220 Lin. * (N2 vs N3) 1 3.70564 0.66006 0.424 Quad. * (N2 vs N3) 1 3.15187 0.56142 0.460 Error (b) 27 5.6141 Appendix 15: Analysis of variance for number of heads m"2 in 1988-89 Source of variation df MS F-value Probability Block 3 16273 2.5976 0.148 Seeding Rate 2 17467 2.7883 0.139 Linear 1 33800 5.3956 0.059 Quadratic 1 1134.38 0.18108 0.685 Error (a) 6 6264.4 Nitrogen 3 0.23207E+6 18.62 0.000 NO vs NI + N2 + N3 1 660833 53.02 0.000 NI vs N2 + N3 1 35068.3 2.8136 0.105 N2vsN3 1 315.375 0.25303E-1 0.875 Interaction 6 6927 0.55577 0.761 Lin. * (NO vs NI + N2 + N3) 1 66.6667 0.53488E-2 0.942 Quad. * (NO vs NI + N2 + N3) 1 833.68 0.66888E-1 0.798 Lin. * (NI vs N2 + N3) 1 2867.52 0.23007 0.635 Quad. * (NI vs N2 + N3) 1 18883.3 15151 0.229 Lin. *(N2vsN3) 1 17358.1 1.3927 0.248 Quad. * (N2 vs N3) 1 1552.69 0.12458 0.727 Error (b) 27 12464 75 Appendix 16: Analysis of variance for number of grains head"1 in 1988-89 Source of variation df MS F-value Probability Block 3 76.651 2.0069 0.215 Seeding Rate 2 73.931 1.9357 0.225 Linear 1 145.564 3.8112 0.099 Quadratic 1 2.29714 0.60144E-1 0.814 Error (a) 6 38.194 Nitrogen 3 78.936 0.9825 0.416 N0vsNl + N2 + N3 1 12.2966 0.15305 0.699 N l vsN2 + N3 1 218.44 2.7189 0.111 N2vsN3 1 6.07015 0.75555E-1 0.786 Interaction 6 40.968 0.50992 0.795 Lin. * (NO vs N l + N2 + N3) 1 95.6603 1.1907 0.285 Quad. * (NO vs N l + N2 + N3) 1 0.587715 0.73152E-2 0.932 Lin. *(NlvsN2 + N3) 1 6.51218 0.81056E-1 0.778 Quad. * (Nl vs N2 + N3) 1 89.3652 1.1123 0.301 Lin. *(N2vsN3) 1 19.8469 0.24703 0.623 Quad. * (N2 vs N3) 1 33.8351 0.42114 0.522 Error (b) 27 38.194 Appendix 17: Analysis of variance for number of grains m"2 in 1988-89 Source of variation df MS F-value Probability Block 3 1.6501 0.27965 0.838 Seeding Rate 2 1.763 0.2988 0.752 Linear 1 2.46969 0.41857 0.542 Quadratic 1 1.05632 0.17902 0.687 Error (a) 6 5.9004 Nitrogen 3 283.89 121.69 0.000 N0vsN l + N2 + N3 1 848.459 363.7 0.000 N l vsN2 + N3 1 2.02676 0.8688 0.340 N2vsN3 1 1.19709 0.51315 0.480 Interaction 6 1.96 0.84016 0.550 Lin. *(N0vsNl+N2 + N3) 1 3.48462 1.4937 0.232 Quad. * (NO vs N l + N2 + N3) 1 2.14418 0.91913 0.346 Lin. *(NlvsN2 + N3) 1 0.115062 0.49323E-1 0.826 Quad.*(NlvsN2 + N3) 1 1.98579 0.85123 0.364 Lin. » (N2 vs N3) 1 3.14173 1.3467 0.256 Quad. * (N2 vs N3) 1 0.888328 0.38079 0.542 Error 0>) 27 2.3328 76 Appendix 18: Analysis of variance for harvest index in 1988-89 Source of variation df MS F-value Probability Block 3 4.2999 0.40448 0.755 Seeding Rate 2 1.7872 0.16811 0.849 Linear 1 1.60201 0.15069 0.711 Quadratic 1 1.97227 0.18552 0.682 Error (a) 6 10.631 Nitrogen 3 26.714 6.4526 0.002 N0vsNl + N2 + N3 1 35.89 8.6691 0.007 N l v s N 2 + N3 1 40.1262 9.6923 0.004 N2 vs N3 1 4.12506 0.99639 0.327 Interaction 6 4.8349 1.1679 0.352 Lin. * (NO vs N l + N2 + N3) 1 10.5337 2.5444 0.122 Quad. * (NO vs N l + N2 + N3) 1 5.22724 1.2626 0.271 Lin. *(NlvsN2 + N3) 1 4.23047 1.0218 0.321 Quad. * (Nl vs N2 + N3) 1 7.28545 1.7598 0.196 Lin. *(N2vsN3) 1 1.44597 0.34927 0.559 Quad. * (N2 vs N3) 1 0.286765 0.69267E-1 0.794 Error (b) 27 3.764 Appendix 19: Analysis of variance for grain protein in 1988-89 Source of variation df MS F-value Probability Block 3 0.71753 1.0699 0.429 Seeding Rate 2 0.76918 1.147 0.379 Linear 1 0.505014 0.75305 0.419 Quadratic 1 1.03332 1.5408 0.261 Error (a) 6 0.67062 Nitrogen 3 26.865 77.905 0.000 N0vsNl + N2 + N3 1 80.3714 233.06 0.000 N l vs N2 + N3 1 0.799198E-3 0.23175E-2 0.962 N2vsN3 1 0.224267 0.65034 0.427 interaction 6 0.54712E-1 0.15865 0.986 Lin. *(N0vsNl + N2 + N3) 1 0.273381E-1 0.79276E-1 0.780 Quad. * (NO vs N l + N2 + N3) 1 0.110443 0.32027 0.576 Lin. * (Nl vs N2 + N3) 1 0.117198E-1 0.33986E-1 0.855 Quad. * (Nl vs N2 + N3) 1 0.976493E-1 0.28317 0.599 Lin. *(N2vsN3) 1 0.798064E-1 0.23142 0.634 Quad. * (N2 vs N3) 1 0.130204E-2 0.37757E-2 0.951 Error Q>) 27 0.34485 77 Appendix 20: Analysis of variance for disease ratings (head) at GS 83 in 1988-89 Source of variation df MS F-value Probability Block 3 0.31875E-1 0.85475 0.513 Seeding Rate 2 0.18958E-1 0.50838 0.625 Linear 1 0.78125E-2 0.2095 0.663 Quadratic 1 0.301042E-1 0.80726 0.404 Error (a) 6 0.37292E-1 Nitrogen 3 0.16875E-1 0.73119 0.542 NO vs NI + N2 + N3 1 0.30625E-1 1.327 0.259 NI vsN2 + N3 1 0.5E-2 0.21665 0.645 N2vsN3 1 0.15E-1 0.64995 0.427 Interaction 6 0.17292E-1 0.74925 0.615 Lin. * (NO vs NI + N2 + N3) 1 0.126042E-1 0.54614 0.466 Quad. • (NO vs NI + N2 + N3) 1 0.378125E-1 1.6384 0.211 Lin. * (NI vs N2 + N3) 1 0.333334E-2 0.14443 0.707 Quad. * (NI vs N2 + N3) 1 0.999999E-2 0.4333 0.516 Lin. *(N2vsN3) 1 0.1E-1 0.4333 0.516 Quad. * (N2 vs N3) 1 0.3E-1 1.2999 0.264 Error (b) 27 0.23079E-1 Appendix 21: Analysis of variance for disease ratings (flag leaf) in 1988-89 Source of variation df MS F-value Probability Block 3 0.69652 3.1994 0.105 Seeding Rate 2 0.12849 0.5902 0.583 Linear 1 0.903125E-1 0.41484 0.543 Quadratic 1 0.166665 0.76555 0.415 Error (a) 6 0.21771 Nitrogen 3 022061 5.5661 0.004 N0vsNl + N2 + N3 1 0.406406 10.254 0.003 NI vs N2 + N3 1 0.245 6.1815 0.019 N2vsN3 1 0.104167E-1 0.26282 0.612 Interaction 6 0.13342 3.3663 0.013 Lin. *(N0vsNl+N2 + N3) 1 0.387605 9.7795 0.004 Quad. * (NO vs NI + N2 + N3) 1 0.125 3.1538 0.087 Lin. *(NlvsN2 + N3) 1 0.880202E-2 0.22208 0.641 Quad. * (NI vs N2 + N3) 1 0.140629E-2 0.35482E-1 0.852 Lin. * (N2 vs N3) 1 0.262656 6.627 0.016 Quad.*(N2vsN3) 1 0.150522E-1 0.37977 0.543 Error Qb) 27 78 Appendix 22: Analysis of variance for number of plants established (40 days after seeding) in 1989-90 Source of variation df MS F-value Probability Block Seeding Rate Linear Quadratic Error 3 2 1 1 6 388.89 51461 102152 770.667 360.89 1.0776 142.6 283.06 2.1355 0.427 0.000 0.000 0.194 Appendix 23: Analysis of in 1989-90 variance for shoot counts (71 days after seeding) Source of variation df MS F-value Probability Block Seeding Rate Linear Quadratic Error 3 2 1 1 6 36115 0.36907E+6 738113 28.1667 238% 1.5113 15.445 30.888 0.11787E-2 0.305 0.004 0.001 0.974 Appendix 24: Analysis of in 1989-90 variance for shoot counts (131 days after seeding) Source of variation df MS F-value Probability Block Seeding Rate Linear Quadratic Error 3 2 1 1 6 4075 0.22418E+6 446513 1837.5 65842 0.61891E-1 3.4048 6.7816 0.27908E-1 0.978 0.103 0.040 0.873 Appendix 25: Analysis of in 1989-90 variance for shoot counts (207 days after seeding) Source of variation df MS F-value Probability Block Seeding Rate Linear Quadratic Error 3 2 1 1 6 10053 0.19268E+6 365513 19837.5 61319 0.16394 3.1422 5.9608 032351 0.917 0.117 0.050 0.590 79 Appendix 26: Analysis of variance for shoot counts (235 days after seeding) in 1989-90 Source of variation df MS F-value Probability Block 3 70354 4.0799 0.068 Seeding Rate 2 0.4332E+6 25.121 0.001 Linear 1 808038 46.859 0.000 Quadratic 1 58361.3 3.3844 0.115 Error (a) 6 17244 Nitrogen 3 17850 1.7128 0.188 N0vsNl + N2 + N3 1 1412.5 0.13554 0.716 NlvsN2 + N3 1 30176.1 2.8956 0.100 N2vsN3 1 21961.5 2.1073 0.158 Interaction 6 3363.9 0.32279 0.919 Lin. *(N0vsNl + N2 + N3) 1 2762.76 0.2651 0.611 Quad. * (NO vs Nl + N2 + N3) 1 1572.67 0.15091 0.701 Lin. *(NlvsN2 + N3) 1 2596.02 0.2491 0.622 Quad. * (Nl vs N2 + N3) 1 5463.67 0.52427 0.475 Lin. * (N2 vs N3) 1 7788.06 0.74731 0.395 Quad.*(N2vsN3) 1 0.1875 0.17992E-4 0.997 Error 0>) 27 10421 Appendix 27: Analysis of variance for shoot counts (263 days after seeding) in 1989-90 Source of variation df MS F-value Probability Block 3 206.47 0.32662E-1 0.991 Seeding Rate 2 0.23042E+6 36.45 0.000 Linear 1 40208 63.605 0.000 Quadratic 1 58756.5 9.2947 0.023 Error (a) 6 6321.5 Nitrogen 3 0.10015E+6 17.217 0.000 N0vsNl+N2 + N3 1 276851 47.595 0.000 Nl vsN2 + N3 1 23508.4 4.0414 0.054 N2vsN3 1 92.0455 0.15824E-1 0.901 Interaction 6 1506.9 0.25906 0.951 Lin. *(N0vsNl + N2 + N3) 1 175104 0.30103E-2 0.957 Quad. * (NO vs Nl + N2 + N3) 1 20.5868 0.35392E-2 0.953 Lin. *(NlvsN2 + N3) 1 667521 0.11476 0.737 Quad.*(NlvsN2 + N3) 1 1729.17 0.29727 0.590 Lin. *(N2vsN3) 1 5076.56 0.87273 0.358 Quad.*(N2vsN3) 1 1530.02 0.26303 0.612 Error 03) 27 5816.9 80 Appendix 28: Analysis of variance for shoot counts (302 days after seeding) in 1989-90 Source of variation df MS F-value Probability Block 3 5600.9 0.7906 0.542 Seeding Rate 2 0.1138E+6 16.064 0.004 Linear 1 206564 29.158 0.002 Quadratic 1 21033.8 2.9691 0.136 Error (a) 6 7084.3 Nitrogen 3 0.22254E+6 43.348 0.000 N0vsNl+N2 + N3 1 663547 129.25 0.000 NI vsN2 + N3 1 3334.75 0.64957 0.427 N2vsN3 1 726 0.14142 0.710 Interaction 6 2926.5 0.57005 0.750 Lin. *(N0vsNl + N2 + N3) 1 981.76 0.19124 0.665 Quad. * (NO vs NI + N2 + N3) 1 949.753 0.185 0.671 Lin. *(NlvsN2 + N3) 1 165.021 0.32144E-1 0.859 Quad. * (NI vs N2 + N3) 1 193.674 0.37726E-1 0.847 Iin. *(N2vsN3) 1 14701.6 2.8637 0.102 Quad. *(N2vsN3) 1 567.188 0.11048 0.742 Error (b) 27 5133.7 Appendix 29: Analysis of variance for dry matter yield at GS 37 in 1989-90 Source of variation df MS F-value Probability Block 3 1.7507 1.1743 0.395 Seeding Rate 2 11.928 8.0014 0.020 Linear 1 22.6465 15.191 0.008 Quadratic 1 1.2105 0.81198 0.402 Error (a) 6 1.4908 Nitrogen 3 14.037 39.635 0.000 N0vsNl + N2 + N3 1 383367 108.25 0.000 NlvsN2 + N3 1 2.38347 6.7298 0.015 N2vsN3 1 1.39202 3.9304 0.058 Interaction 6 0.87349 2.4663 0.049 Lin. * (NO vs NI + N2 + N3) 1 0.734998 2.0753 0.161 Quad. * (NO vs NI + N2 + N3) 1 0.900034 25413 0.123 Lin. *(NlvsN2 + N3) 1 0.522919 1.4765 0.235 Quad. * (NI vs N2 + N3) 1 0.733508E-1 0.20711 0.653 Lin. *(N2vsN3) 1 2.83081 7.9929 0.009 Quad.*(N2vsN3) 1 0.178852 0.505 0.483 Error (b) 27 0.35417 81 Appendix 30: Analysis of variance for dry matter yield at GS 69 in 1989-90 Source of variation df MS F-value Probability Block 3 0.90787 0.30551 0.821 Seeding Rate 2 4.5798 1.5412 0.288 Linear 1 9.1592 3.0822 0.130 Quadratic 1 0.33816E-3 0.1138E-3 0.992 Error (a) 6 2.9716 Nitrogen 3 85.763 45.19 0.000 N0vsNl + N2 + N3 1 240.172 126.55 0.000 N l vs N2 + N3 1 14.2044 7.4846 0.011 N2vsN3 1 2.91196 1.5344 0.226 Interaction 6 3.1954 1.6837 0.163 Lin. *(N0vsNl + N2 + N3) 1 13.9843 7.3686 0.0114 Quad. * (NO vs N l + N2 + N3) 1 1.05853 0.55776 0.462 Lin. *(NlvsN2 + N3) 1 1.17814 0.62079 0.438 Quad. * (Nl vs N2 + N3) 1 0.731008 0.38518 0.540 Lin. *(N2vsN3) 1 0.999798E-2 0.52681E-2 0.943 Quad.*(N2vsN3) 1 2.21021 1.1646 0.290 Error 03) 27 1.8978 Appendix 31: Analysis of variance for dry matter yield at GS 85 in 1989-90 Source of variation df MS F-value Probability Block 3 5.1621 0.82971 0.524 Seeding Rate 2 4.9159 0.79014 0.496 Linear 1 2.70866 0.43537 0.534 Quadratic 1 7.1231 1.1449 0.326 Error (a) 6 6.2216 Nitrogen 3 191.8 37.888 0.000 N0vsNl+N2 + N3 1 565.052 111.62 0.000 N l vsN2 + N3 1 0.238324E-1 0.47079E-2 0.946 N2vsN3 1 103095 2.0366 0.165 Interaction 6 8514 1.6819 0.164 Lin. *(N0vsNl + N2 + N3) 1 37.5876 7.4251 0.011 Quad. * (NO vs N l + N2 + N3) 1 3.83876 0.75831 0.392 Lin. * (Nl vs N2 + N3) 1 3.3974 0.67113 0.420 Quad. * (Nl vs N2 + N3) 1 0.160675 0.3174E-1 0.860 Lin. *(N2vsN3) 1 6.08862 1.2028 0.282 Quad. *(N2vsN3) 1 0.111034E-1 0.21934E-2 0.963 Error 03) 27 5.0622 82 Appendix 32: Analysis of variance for dry matter yield at GS 92 in 1989-90 Source of variation df MS F-value Probability Block 3 11.53 3.6443 0.083 Seeding Rate 2 9.4275 2.9798 0.126 Linear 1 13.8866 4.3892 0.081 Quadratic 1 4.96875 1.5705 0.257 Error (a) 6 3.1638 Nitrogen 3 224.44 52.06 0.000 NO vs NI + N2 + N3 1 664.178 154.06 0.000 NI vs N2 + N3 1 9.10924 2.113 0.158 N2 vs N3 1 0.273415E-1 0.63421E-2 0.937 Interaction 6 8.1298 1.8858 0.120 Lin. *(N0vsNl+N2 + N3) 1 27.8642 6.4633 0.017 Quad. * (NO vs NI + N2 + N3) 1 3.77211 0.87497 0.358 Lin. * (NI vs N2 + N3) 1 2.97014 0.68895 0.414 Quad. * (NI vs N2 + N3) 1 14.0876 3.2677 0.082 Lin. * (N2 vs N3) 1 0.702246E-1 0.16289E-1 0.899 Quad. * (N2 vs N3) 1 0.14701E-1 0.341E-2 0.954 Error (b) 27 4.3111 Appendix 33: Analysis of variance for N uptake at GS 37 in 1989-90 Source of variation df MS F-value Probability Block 3 2290.2 4.6626 0.052 Seeding Rate 2 838.85 1.7078 0.259 Linear 1 1424.98 2.9011 0.139 Quadratic 1 252.72 051452 0.500 Error (a) 6 491.18 Nitrogen 3 26677 85.982 0.000 N0vsNl + N2 + N3 1 75353 242.87 0.000 NI vsN2 + N3 1 2676.59 8.627 0.007 N2vsN3 1 2000.38 6.4475 0.017 Interaction 6 194.37 0.62648 0.708 Lin. *(N0vsNl + N2 + N3) 1 287.25 0.92584 0.344 Quad. * (NO vs NI + N2 + N3) 1 231.984 0.74771 0.395 Lin. *(NlvsN2 + N3) 1 278.454 0.89749 0.352 Quad. * (NI vs N2 + N3) 1 99.3497 0.32022 0.576 Lin. *(N2vsN3) 1 244.375 0.78765 0.383 Quad. * (N2 vs N3) 1 24.8114 0.7997E-1 0.779 Error (b) 27 310.26 Appendix 34: Analysis of variance for N uptake at GS 69 in 1989-90 83 Source of variation df MS F-value Probability Block 3 794.23 0.48978 0.702 Seeding Rate 2 358.71 0.22121 0.808 Linear 1 37.4115 0.23071E-1 0.884 Quadratic 1 680.016 0.41935 0.541 Error (a) 6 1621.6 Nitrogen 3 69797 134.89 0.000 N0vsNl+N2 + N3 1 207047 400.12 0.000 Nl vsN2 + N3 1 1.85573 0.35862E-2 0.953 N2vsN3 1 2343.14 4.5282 0!043 Interaction 6 395.37 0.76407 0.604 Lin. *(N0vsNl + N2 + N3) 1 864 1.6697 0.207 Quad. * (NO vs Nl + N2 + N3) 1 104.86 0.20264 0.656 Lin. +(NlvsN2 + N3) 1 1362.35 2.6328 0.116 Quad. * (Nl vs N2 + N3) 1 0.312361E-1 0.60365E-4 0.994 Lin. *(N2vsN3) 1 25.9081 0.50068E-1 0.825 Quad.*(N2vsN3) 1 15.0977 0.29177E-1 0.866 Error (b) 27 517.46 Appendix 35: Analysis of variance for N uptake at GS 85 in 1989-90 Source of variation df MS F-value Probability Block 3 1222.4 0.58419 0.647 Seeding Rate 2 14.439 0.69007E-2 0.993 Linear 1 0.101255 0.48392E-4 0.995 Quadratic 1 28.7743 0.13752E-1 0.910 Error (a) 6 2092.4 Nitrogen 3 73492 166.91 0.000 N0vsNl + N2+N3 1 219084 49756 0.000 Nl vs N2 + N3 1 1211.86 2.7523 0.109 N2vsN3 1 180.786 0.41059 0.527 Interaction 6 455.18 1.0338 0.425 Lin. *(N0vsNl + N2 + N3) 1 1738.08 3.9474 0.057 Quad. • (NO vs Nl + N2 + N3) 1 6.83312 0.15519E-1 0.902 Lin. *(NlvsN2 + N3) 1 573395 13022 0.264 Quad.*(Nl vsN2 + N3) 1 60.1678 0.13665 0.715 Lin. *(N2vsN3) 1 343.731 0.78065 0.385 Quad.*(N2vsN3) 1 8.85817 0.20118E-1 0.888 Error fl>) 27 440.31 84 Appendix 36: Analysis of variance for N uptake at GS 92 in 1989-90 Source of variation df MS F-value Probability Block 3 4327 3.882 0.074 Seeding Rate 2 1403.1 1.2588 0.350 Linear 1 2102.76 1.8865 0.219 Quadratic 1 703.506 0.63116 0.457 Error (a) 6 1114.6 Nitrogen 3 78501 136.87 0.000 N0vsNl + N2 + N3 1 234685 409.18 0.000 NI vsN2 + N3 1 144.499 0.25194 0.620 N2vsN3 1 673.524 1.1743 0.288 Interaction 6 1258.2 2.1937 0.075 Lin. *(N0vsNl+N2 + N3) 1 2370.09 4.1323 0.052 Quad. * (NO vs NI + N2 + N3) 1 195.031 0.34004 0.565 Lin. *(NlvsN2 + N3) 1 296.711 0.51732 0.478 Quad. * 0M1 vs N2 + N3) 1 4284.34 7.4699 0.011 Lin. * (N2 vs N3) 1 392.634 0.68457 0.415 Quad. * (N2 vs N3) 1 10.4349 0.18193E-1 0.894 Error (b) 27 573.55 Appendix 37: Analysis of variance for soil NH4 -N + N0 3 -N (0-50 cm) at GS 37 in 1989-90 Source of variation df MS F-value Probability Block 3 3303.9 9.184 0.012 Seeding Rate 2 278.82 0.77504 0.502 Linear 1 193.799 0.53871 0.491 Quadratic 1 363.833 1.0114 0.353 Error (a) 6 359.74 Nitrogen 3 927.61 6.1373 0.003 N0vsNl + N2 + N3 1 2125.13 14.06 0.001 NI vsN2 + N3 1 650.582 4.3044 0.048 N2vsN3 1 7.11778 0.47093E-1 0.830 Interaction 6 189.45 1.2535 0.311 Lin. *(N0vsNl+N2 + N3) 1 65.0925 0.43067 0.517 Quad. * (NO vs NI + N2 + N3) 1 201.419 1.3326 0258 Lin. *(NlvsN2 + N3) 1 83.6349 055335 0.463 Quad. * (NI vs N2 + N3) 1 501.013 3.3148 0.080 Lin. *(N2vsN3) 1 175.43 1.1607 0.291 Quad. * (N2 vs N3) 1 110.111 0.72852 0.401 Error (b) 27 151.14 85 Appendix 38: Analysis of variance for soil NH4 -N + NGyN (0-50 cm) at GS 69 in 1989-90 Source of variation df MS F-value Probability Block 3 91.129 0.53023 0.678 Seeding Rate 2 10.247 0.59625E-1 0.943 Linear 1 10.08 0.5865E-1 0.817 Quadratic 1 10.4149 0.60599E-1 0.814 Error (a) 6 171.87 Nitrogen 3 505.16 11.481 0.000 N0vsNl + N2 + N3 1 1366.72 31.063 0.000 Nl vsN2 + N3 1 52.9077 1.2025 0.283 N2vsN3 1 95.84 2.1782 0.152 Interaction 6 21.157 0.48085 0.817 Lin. * (NO vs Nl + N2 + N3) 1 41.2387 0.93727 0.342 Quad. * (NO vs Nl + N2 + N3) 1 3.86881 0.8793E-1 0.769 Lin. *(NlvsN2 + N3) 1 7.42609 0.16878 0.684 Quad. * (Nl vs N2 + N3) 1 15.8668 0.36062 0.553 Lin. * (N2 vs N3) 1 58.4461 1.3284 0.259 Quad. *(N2vsN3) 1 0.954049E-1 0.21683E-2 0.963 Error ft>) 27 43.999 Appendix 39: Analysis of variance for soil NH4 -N + NO3-N (0-50 cm) at GS 85 in 1989-90 Source of variation df MS F-value Probability Block 3 297.44 0.80045 0.537 Seeding Rate 2 642.49 1.729 0.255 Linear 1 916.455 2.4663 0.167 Quadratic 1 368521 0.99175 0.358 Error (a) 6 37159 Nitrogen 3 473.75 2.4592 0.084 N0vsNl + N2+N3 1 141752 7.3581 0.011 Nl vs N2 + N3 1 0.806475 0.41863E-2 0.949 N2vsN3 1 2.92602 0.15188E-1 0.903 Interaction 6 162.22 0.84207 0.549 Lin. *(N0vsNl + N2 + N3) 1 489.109 25389 0.123 Quad. * (NO vs Nl + N2 + N3) 1 46.924 0.24357 0.626 Lin. *(NlvsN2 + N3) 1 144.699 0.75111 0.394 Quad. *(N1 vsN2 + N3) 1 109.621 056902 0.457 Lin. *(N2vsN3) 1 90.6305 0.47045 0.499 Quad. * GM2 vs N3) 1 92.3521 0.47938 0.495 Error 03) 27 192.65 86 Appendix 40: Analysis of variance for thousand grain yield in 1989-90 Source of variation df MS F-value Probability Block 3 2.7399 2.1604 0.194 Seeding Rate 2 14.046 11.075 0.009 Linear 1 27.1769 21.429 0.004 Quadratic 1 0.914553 0.72112 0.428 Error (a) 6 1.2682 Nitrogen 3 43.78 25.079 0.000 NO vs NI + N2 + N3 1 131.026 75.057 0.000 NlvsN2 + N3 1 0.678349E-1 0.38858E-1 0.845 N2vsN3 1 0.246038 0.14094 0.710 Interaction 6 1.702 0.97497 0.461 Lin. *(N0vsNl + N2 + N3) 1 7.3538 4.2125 0.050 Quad. * (NO vs NI + N2 + N3) 1 0.450461 0.25804 0.616 Lin. * (NI vs N2 + N3) 1 0.902001 0.5167 0.478 Quad. * (NI vs N2 + N3) 1 1.35333 0.77524 0.386 Lin. * (N2 vs N3) 1 0.756248E-1 0.43321E-1 0.837 Quad. * (N2 vs N3) 1 0.767968E-1 0.43992E-1 0.835 Error (b) 27 1.7457 Appendix 41: Analysis of variance for grain weight in 1989-90 Source of variation df MS F-value Probability Block 3 32.666 3.9131 0.073 Seeding Rate 2 14.206 1.7018 0.260 Linear 1 28.313 3.3917 0.115 Quadratic 1 0.010011 0.11992E-1 0.916 Error (a) 6 8.3478 Nitrogen 3 16.76 5.9992 0.003 N0vsNl + N2+N3 1 ' '47.7252 17.084 0.000 NI vs N2 + N3 1 1.0035 035921 0.554 N2 ys N3 1 1.5504 055498 0.463 Interaction 6 10.383 3.7168 0.008 Lin. *(N0vsNl + N2 + N3) 1 5.27347 1.8877 0.181 Quad. * (NO vs NI + N2 + N3) 1 21.5058 7.6981 0.010 Lin. * (NI vs N2 + N3) 1 25.6669 9.1876 0.005 Quad. * (NI vs N2 + N3) 1 8.45847 3.0278 0.093 Lin. *(N2vsN3) 1 0.765625 0.27406 0.605 Quad. * (N2 vs N3) 1 0.630237 0.2256 0.639 Error (b) 27 2.7936 87 Appendix 42: Analysis of variance for number of heads nr 2 in 1989-90 Source of variation df MS F-value Probability Block 3 25756 2.1713 0.192 Seeding Rate 2 4806.3 0.40519 0.684 Linear 1 12.5 0.10538E-2 0.975 Quadratic 1 9600 0.80932 0.403 Error (a) 6 11862 Nitrogen 3 75739 15.118 0.000 N0vsN l + N2 + N3 1 227211 45.354 0.000 N l vs N2 + N3 1 1.38862 0.27718E-3 0.987 N2vsN3 1 4.16585 0.83155E-3 0.977 Interaction 6 12445 2.4842 0.048 Lin. *(N0vsNl + N2 + N3) 1 7004.16 1.3981 0.247 Quad. * (NO vs N l + N2 + N3) 1 2222.22 0.44358 0.511 Lin. * (Nl vs N2 + N3) 1 9633.34 1.9229 0.177 Quad. + (Nl vs N2 + N3) 1 31802.8 6.3482 0.018 Lin. * (N2 vs N3) 1 19600 3.9124 0.058 Quad. * (N2 vs N3) 1 4408.34 0.87996 0.357 Error 0?) 27 5009.7 Appendix 43: Analysis of variance for number of grains head"1 in 1989-90 Source of variation df MS F-value Probability Block 3 25.258 0.28079 0.838 Seeding Rate 2 172.81 1.9211 0.227 Linear 1 342.829 3.8112 0.099 Quadratic 1 2.78797 0.30994E-1 0.866 Error (a) 6 89.953 Nitrogen 3 123.98 5.7163 0.004 N0vsNl+N2 + N3 1 363.442 16.758 0.000 N l v s N 2 + N3 1 7.7552 0.35758 0.555 N2vsN3 1 0.731505 033728E-1 0.856 Interaction 6 23.611 1.0887 0.394 Lin. *(N0vsNl+N2 + N3) 1 25.73 1.1864 0.286 Quad. * (NO vs N l + N2 + N3) 1 4.81537 0.22203 0.641 Lin. *(NlvsN2 + N3) 1 30.5123 1.4069 0.246 Quad. * (Nl vs N2 + N3) 1 21.7544 1.0031 0.325 Lin. * (N2 vs N3) 1 46.6831 2.1525 0.154 Quad. * (N2 vs N3) 1 12.1706 0.56116 0.460 Error 0)) 27 88 Appendix 44: Analysis of variance for grains m"2 in 1989-90 Source of variation df MS F-value Probability Block 3 0.95654E+7 2.1495 0.195 Seeding Rate 2 0.40856E+8 9.1811 0.015 Linear 1 0.751528E+8 16.888 0.006 Quadratic 1 0.655839E+7 1.4738 0.270 Error (a) 6 0.445E+7 Nitrogen 3 0.16075E+9 26.134 0.000 N0vsNl + N2 + N3 1 0.480168E+9 78.067 0.000 NI vs N2 + N3 1 69212.3 0.11253E-1 0.916 N2vsN3 1 0.200042E+7 0.32523 0.573 Interaction * 6 0.53254E+7 0.86582 0.532 Lin. *(N0vsNl+N2 + N3) 1 0.211494E+8 3.4385 0.075 Quad. * (NO vs NI + N2 + N3) 1 35600.4 0.5788E-2 0.940 Lin. *(NlvsN2 + N3) 1 21022.6 0.34179E-2 0.954 Quad. * (NI vs N2 + N3) 1 0.966358E+7 1.5711 0.221 Lin. *(N2vsN3) 1 0.101718E+7 0.16538 0.687 Quad.*(N2vsN3) 1 65799.9 0.10698E-1 0.918 Error (b) 27 0.61508E+7 Appendix 45: Analysis of variance for harvest index in 1989-90 Source of variation df MS F-value Probability Block 3 21.283 2.4592 0.160 Seeding Rate 2 139.63 16.134 0.004 Linear 1 276.948 32.001 0.001 Quadratic 1 2.30644 0.26651 0.624 Error (a) 6 8.6544 Nitrogen 3 66.104 6.2142 0.002 N0vsNl + N2 + N3 1 188.239 17.696 0.000 NI vsN2 + N3 1 7.23899 0.68051 0.417 N2vsN3 1 2.83594 0.2666 0.610 Interaction 6 1.9747 0.18563 0.978 Lin. *(N0vsNl+N2 + N3) 1 3.73673 0.35128 0.558 Quad. * (NO vs NI + N2 + N3) 1 0.881928E-1 0.82907E-2 0.928 Lin. *(NlvsN2 + N3) 1 2.6602 0.25008 0.621 Quad. * (NI vs N2 + N3) 1 1.1664 0.10965 0.743 Lin. *(N2vsN3) 1 2.78889 0.26217 0.613 Quad. * (N2 vs N3) 1 1.40773 0.13234 0.719 Error (b) 27 10.638 89 Appendix 46: Analysis of variance for grain protein in 1989-90 Source of variation df MS F-value Probability Block 3 0.14398 0.78291E-1 0.969 Seeding Rate 2 1.2916 0.70234 0.532 Linear 1 2.53688 1.3795 0.285 Quadratic 1 0.463754E-1 0.25217E-1 0.879 Error (a) 6 1.839 Nitrogen 3 28.131 77.249 0.000 NO vs Nl + N2 + N3 1 82.7192 227.15 0.000 Nl vsN2 + N3 1 1.61997 4.4485 0.044 N2vsN3 1 0.541503E-1 0.1487 0.703 Interaction 6 0.38007 1.0437 0.420 Lin. *(N0vsNl + N2 + N3) 1 0.562738 1.5453 0.225 Quad. • (NO vs Nl + N2 + N3) 1 0.342387 0.9402 0.341 Lin. * (Nl vs N2 + N3) 1 0.529204 1.4532 0.238 Quad. * (Nl vs N2 + N3) 1 0.722488 1.984 0.170 Lin. * (N2 vs N3) 1 0.1089 0.29904 0.589 Quad. * (N2 vs N3) 1 0.146996E-1 0.40366E-1 0.842 Error (b) 27 0.36416 Appendix 47: Analysis of variance for disease ratings U\ead) at GS 83 in 1989-90 Source of variation df MS F-value Probability Block 3 1.8047 14.543 0.004 Seeding Rate 2 0.12521 1.009 0.419 Linear 1 0.195313 1.5739 0.256 Quadratic 1 0551042E-1 0.44404 0.530 Error (a) 6 0.1241 Nitrogen 3 0.39472 8.7267 0.000 N0vsNl + N2+N3 1 1.17361 25.947 0.000 Nl vsN2 + N3 1 0.138889E-3 0.30706E-2 0.956 N2 vs N3 1 0.104166E-1 0.2303 0.635 Interaction 6 0.20764E-1 0.45906 0.832 Lin. *(N0vsNl + N2 + N3) 1 0.876041E-1 1.9368 0.175 Quad. * (NO vs Nl + N2 + N3) 1 0.586809E-2 0.12973 0.722 Lin. *(NlvsN2 + N3) 1 0.102083E-1 0.22569 0.639 Quad. • (Nl vs N2 + N3) 1 0.694476E^ 1 0.15354E-2 0.969 Lin. *(N2vsN3) 1 0.15625E-1 0.34545 0.562 Quad. * (N2 vs N3) 1 0.520834E-2 0.11515 0.737 Error 03) 27 0.45231E-1 90 Appendix 48: Analysis of variance for disease ratings (flag leaf) at GS 83 in 1989-90 Source of variation df MS F-value Probability Block 3 0.24667 0.71627 0577 Seeding Rate 2 0.79375E-1 0.23049 0.801 Linear 1 0.112811 0.32758 0.588 Quadratic 1 0.459374E-1 0.13339 0.727 Error (a) 6 0.34437 Nitrogen 3 2.5072 31.358 0.000 N0vsNl + N2 + N3 1 7.29 91.178 0.000 NI vs N2 + N3 1 0.125 1.5634 0.222 N2 vs N3 1 0.106667 1.3341 0.258 Interaction 6 0.52431E-1 0.65576 0.685 Lin. * (NO vs NI + N2 + N3) 1 0.45937E-1 0.57455 0.455 Quad. * (NO vs NI + N2 + N3) 1 0.253124E-1 0.31659 0578 Lin. * (NI vs N2 + N3) 1 0.675E-1 0.84424 0.366 Quad. * (NI vs N2 + N3) 1 0.400002E-1 0500029 0.485 Lin. *(N2vsN3) 1 0.1225 1.5321 0.226 Quad.*(N2vsN3) 1 0.133336E-1 0.16677 0.686 Error (b) 27 0.79954E-1 Appendix 49: Analysis of variance for disease ratings (penultimate leaf) at GS 83 in 1989-90 Source of variation df MS F-value Probability Block 3 1.3725 2.0327 0.211 Seeding Rate 2 0.4375E-2 0.64795E-2 0.994 Linear 1 0.499985E-2 0.74049E-2 0.934 Quadratic 1 0.375008E-2 0.55539E-2 0.943 Error (a) 6 0.67521 Nitrogen 3 8.8475 37.94 0.000 N0vsNl + N2 + N3 1 26.5225 113.74 0.000 NI vsN2 + N3 1 0.500004E-2 0.21441E-1 0.885 N2vsN3 1 0.150001E-1 0.64324 0.802 Interaction 6 0.24604 1.0551 0.413 Lin. *(N0vsNl + N2 + N3) 1 0.481666 2.0655 0.162 Quad. * (NO vs NI + N2 + N3) 1 0.55125 2.3639 0.136 Lin. *(NlvsN2 + N3) 1 0.163333 0.70042 0.410 Quad.*(NlvsN2 + N3) 1 0.900006E-1 0.38595 0.540 Lin. *(N2vsN3) 1 0.16 0.68612 0.415 Quad. * (N2 vs N3) 1 0.300003E-1 0.12865 0.723 Error (b) 27 0.23319 

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