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A study of the organic fraction of some British Columbia soils Cook, Fred Delmer 1947

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L t 3 /by c ny fl* Cb 5? A Study of the Organic Fraction of Some Bri t i s h Columbia Soils by Fred Delmer Cook -o 0 o-A Thesis submitted in Partial Fulfilment of The Requirements for the Degree of MASTER OF SCIENCE IN AGRICULTURE in the Department of AGRONOMY (SOILS) -o 0 o-The University of Br i t i s h Columbia ACKNOWLEDGEMENTS The author wishes to express his sincere appreciation to Dr. D.G. Laird under whose guidance the work was conducted, and to Dr. C. Rowles for his helpful criticisms and suggestions. TABLE OF CONTENTS. PART A. Proximate Analysis of Organic Matter, of some B.C. Soils. Page Review of Literature 3 - 6 Description of Soils 6 -10 Experimental 11 -14 Discussion of Fractions 15 -16 Results and Discussion of Results 17 -25 Conclusions 25 -26 PART B. Study of Lignin in Organic Matter. Review of. Literature 27 -35 Experimental 35 -39 Discussion on Experimental 39 -4-3 Data and Discussion 43 -46 Hypoiodite Oxidation 46 - 5 0 Conclusions PART C. Determination of Soil Pigment in some B.C. Soils. Review of Literature 52-54 Experimental 54-55 Data and Discussion 55-59 Conclusions 69. Summary 61-62 Bibliography 6 3 " 6 8 A Study of the Organic Fraction of Some Br i t i s h Columbia Soils by Fred Delmer Cook* ABSTRACT PART A.-Carbon content, carbon-nitrogen ratio and a prox-imate analysis were determined on the organic matter of some representative B r i t i s h Columbia and Alberta zonal s o i l s . Comparing s o i l zones carbon content and hence percentage of organic matter was higher in the A Q horizons of the Grey Wooded soils while that i n the Ai horizons i s higher in the Shallow Black and Transition-al soils. The carbon-nitrogen ratio was narrower in the grassland so i l s . Although proximate analysis did not show startling differences between zones, certain differences seem to be significant: (a) Higher "lignin" nitrogen complex and l i p i d content i n Pacific Coast and Grey Wooded soi l s . (b) Percentages of "hemicellulose" and "cellulose" decrease in passing from the A 0 to the A^ horizon. (o) "Lignin" and nitrogenous complexes concentrate in the A^ horizons. PART B.-Nitrobenzene oxidation of s o i l organic matter from various sources yielded no characteristic oxidation products although excellent yields of v a n i l l i n and syringaldehyde were obtained from oxidation of spruce wood, f i r wood and rye straw. It i s suggested that the groups involved in the nitrobenzene oxid-ation reaction are destroyed during decomposition of plant materials, or that, some shortcomings in techniqu were responsible for the ina b i l i t y to isolate characteristic compounds. Hypoiodite oxidation of zonal soils and their l i g n i n residues showed no consistant differences in the nature of the lignin. Oxidation by hypoiodite i s questioned as a means of detecting differences in the constitution of the organic fraction of B.C. soils. PART C -Relative humus colour i s shown to be higher in the Shallow Black and Transitional s o i l s . This difference may be used as a criterion of s o i l type, Also the A^ horizons of a l l soils examined show a higher humus colour value than the corresponding A Q horizon. (1) INTRODUCTION. The classification of soils i s based on a study of parent material, profile development and textural grouping in the f i e l d , and substantiated by chemical and physical analysis i n the laboratory. The chemical determinations for the most part, embrace a study of such phenomena as movement of sesquioxides, accumulation of salts, base exchange and hydrogen ion concentration. The amount of organic matter i s also determined but no attempt i s made to determine the chemical nature of i t and relate the same to parent material, climate, topography and s o i l forming processes. A detailed study of the organic fraction of a s o i l should materially aid the pedologist,since processes of s o i l formation and characterization are intimately ti e d in with the chemical and physioal character of organic matter. Existing methods are admittedly inadequate but despite this,specific and interesting Information may be obtained from the application of available methods to a ciaemioal study of s o i l organic matter. The study herein reported was undertaken in order to focus attention on the need for further work on the biochemistry of organic matter, to demonstrate differences in the organic fraction of zonal s o i l s as well as of soils (2) within an association and to contribute something to the understanding of, or perfecting methods for fractionating organic residues. The soils studied are, for the most part, from the Central Interior area of Br i t i s h Columbia and represent soils from the Shallow Black, Grey Wooded, Black-Grey Transition and Pacific Coast s o i l zones. Typical Grey Wooded and Transitional soils from Alberta are also included i n the study for purposes of comparison. PART A (3) PROXIMATE ANALYSIS Review of Literature Literature relating to the physical properties and general chemical nature of organic matter is very extensive while that pertaining to differences i n the chemical nature of the organic fraction i n different soils i s rather limited. Since the literature on organic matter having general application has been f u l l y reviewed by Waksman (1938) the present review w i l l be confined to those references tnat concern directly or indirectly chemical differences between organic fractions of s o i l types. Schriener and Shorey (1910) using 2 per cent sodium hydroxide, alcohol and other solvents evolved a fractionation procedure whereby they demonstrated differences in carbon content between fresh and decomposing organic residues. Shorey (1930) in a review of methods outlined a number of tests based upon the isolation of well defined chemical compounds that could be applied to soils in order to bring out differences in the organic fraction. Pursulhlgs the question of differences between fresh and decomposed materials further, Bouyoucog i n 1934 described an ingenious method for determining the degree of decomposition of organic matter. His method i s (4) based upon the relative v o l a t i l i t y of fresh and decomposed material in a sealed bomb at 300° C. The amount of uronic carbon in organic matter was studied by Norman and Bartholomew (194-3) and they found that the proportion of uronic acid increased with depth in podsol soils where a marked accumul-ation of uronic carbon i s found in the B. horizon. In recognizing this observation they say, "Perhaps uronic acids are the *acids* often postulated but never proven to be the agents of cation transfer in the podsolization process." Previously the origin of uronic acids in soils has been discussed i n a highly theoretical papat* by Waksman and Reuzer. (1932). A detailed study of the chemical nature of ammon-ium hydroxide extracts which involved acetylation, methylation and determination of pQtentiometric curves, was undertaken by Gillam (1940). He i s led to the conclusion that the humic acid fraction of every s o i l i s about the same chemically and appears to be oomposed ohiefly of lignin. C r i t i c a l reviews on the methods of determination of organio matter, organic oarbon and carbonates ane presented by a number of workers including Alexander and Byers (1932), Waksman and Stevens (1930),Schroer ( 1944• The so-called proximate analysis proposed by the Russians and later modified and adapted to American soils (5) by Waksman and Stevens (1930a) has been used extensively during the past decade for characterization of organic matter. In fact, Waksman. (194-2) states that he has l i s t e d 87 different reports from workers that have used his modification of the proximate analysis. In brief, this method determines from 85% - 100% of the organic matter as " l i p i d s " , water soluble, "hemicellulose", "cellulose", "lignins" and "protein." A modification of Waksman*s procedure was described by Vandecaveye and Katznelson (194-0) in which the percentage carbon removed by each fractionation procedure was determined. This modification has merit in that no arbitrary factors or empirical determinations are involved. Recently the proximate analysis modified by Shewan (1938) has been used by Salisbury and De I»0ng (194-0) to compare organic matter in virgin and cultivated Quebec podsol soils. These workers found that "protein" resistant to hydrolysis forms a slightly larger proportion of the organic matter in cultivated and pastured so i l s , and that the "hemicellulose" content of the virgin soils i s higher than that of the cultivated and pastured s o i l s . Also, the "lignin" content was lower in the latter s o i l s . More recently, Gross (194-6) studied and characterized the forest floor layers in Northern Saskatchewan Grey Wooded soils. Gross reports that no consistent differences were (b) noted between, different forest floor types i n regards to amount of " l i p i d s " and water soluble organic sub-stances. However in granular mor. types hemicelluloses increase with decomposition of the leaf l i t t e r whereas this fraction decreases with decomposition of the l i t t e r of other mor types. For a l l forested types he found a rapid decrease in "cellulose" content and a steady increase in l i g n i n content with decomposition of the leaf l i t t e r . Description of the Soils A description of the s o i l associations and the horizon samples taken for analysis are presented in Tables I and II. Further information about these so i l s , the general description of the area and the type of agriculture for the Central Interior may be found i n Farstad and Laird (1945). TABLE I GENERAL INFORMATION ABOUT THE SOILS UNDER STUDY. Association Name Texture Zone (Tentative) Location Topography Native Vegetation. Dawson Clay Shallow Black Dawson Creek Sloping 2-10% Grasses and Poplar Nulki ti n S.W. of Vanderhoof Undulating n Driftwood Loam n Bulkley Valley Rolling to h i l l y n Pinchi Clay n Pinohi Lake Undulating to rol l i n g Grasses Barret Loam Grey Wooded n Holling to h i l l y Coniferous forest Vanderhoof n n Vanderhoof Undulating n Alberta Grey-* Wooded Clay Loam ti nr. Eaglesham Alta. Gently rolling to r o l l i n g Poplar Fort St.James Clay ti Fort.St.James Undulating to h i l l y Poplar and conifers Doughty n n nr. Smithers n ooniferous forest Telkwa it Black-Grey Transition Telkwa Rolling to h i l l y Grasses,pop-l a r & conifers Alberta Transition n n nr. Codessa Alta. Undulating Poplar and grasses Lakelse n Pacific Coast Terrace,B.C. Undulating Conifers and Bracken. 1 ** Soils not supplied with association names. (8) TABLE II PROFILE DESCRIPTIONS OF SOILS UNDER STUDY Zone Association Horizon Depth Description Dawson Shallow Black Pinehi Driftwood Barret Grey-Wooded An Al Ao AQ Al 0-2" Blackish, highly fibrous, tough layer formed from grass roots. 2"-7" Black granular, friable clay loam. AjUpper 0-1" AjLower l"-6" 0-2" 2n-<5" 0-2M l"-2» Dark brown partially decomposed remains of leaves, grasses & herbs. Dark grey to almost black clay, upper two inches granular in structure. Lower three inches dark grey granular with tend-ency towards platiness. The whole is often so underwoven with grass roots that compact sod i s formed. BlaCk finely granular clay with an extremely tough mat of grass roots. Dark grey to black highly granular clay. P a r t i a l l y decomposed re-mains of leaves, grasses, herbs, etc. Dark brown to black, gran-ular loam, numerous grass roots and small stones present. Dark brown partially decomposed remains of masses and coniferous forest debris. 2"-4w Brown friable loam, mod-erately supplied with organic matter. Weak granular structure, numerous roots and stones (9) TABLE II (continued) Zone Association Horizon Depth Description Vanderhoof A. An Grey 2" Raw undecomposed mass of needles & twigs. The whole i s extremely fibrous and contains many roots. 0-2" Dark grey to brown grey clay containing consid-erable mere-decomposed organic material mixed with the mineral s o i l . Struct-ure i s granular with a slight indication of platiness in the lower part of the horizon. Wooded Alberta Grey Wooded AQ Fort St. James Ao 0-2" P a r t i a l l y decomposed debris from poplar and grasses. 2" Highly granular clay loam, black to grey brown. 2" P a r t i a l l y decomposed remains of poplar leaves, grasses and coniferous tree debris. 0-2* Dark grey to brown fine granular day. Doughty AQ - Variable depth of accumul-ated remains of par t i a l l y decomposed needles, twigs and mosses. *• A^ 0-2" Grey clay with brownish colouring, platy structure with small amount of granulation. (10) TABLE II (continued) Zone Assooiation Horizon Depth Description Blaok Grey Transit* ion Telkwa Al 0-i" Black, rooty and fibrous pa r t i a l l y decomposed remains of acornes and poplar debris. £ U - 4 W Dark brown to black, friable granular clay. This horizon varies up to 8" in depth. Pacific Coast Alberta Transition Ar Lakelse Ai A, 0-2" Decomposed remains of acornes and poplar leaves. Black, granular, clay loam. A dark brown fibrous mat of organic accululation consisting of mosses, bracken and coniferous debris. An N i l j^c Horizons not analysed in this study. (11) Experimental The previously described soils were analysed following in general the method outlined by Shewan (1938). After a number of preliminary determinations, a number of minor changes in the teohnique were introduced to give increased accuracy and convenience. These changes are as follows: (a) The^lipid^fraction was determined by extracting the s o i l i n a Soxhlet with 50:50 alcohol-benzene for 48 hours instead of extracting with both ether and alcohol. Preliminary work showed that this treatment simplified the technique without altering the produots removed. The extracted " l i p i d s " after removal of the solvent was dried over ^anhydrous calcium chloride to constant weight since Salisbury and De Long (1940) have reported the presence of a product which i s volatile at 105°C (b) After each extraction process, with exceptions in determination of lignin }the total residue was used for the next operation instead of taking a weighed portion of the previously extracted residues. (c) Determination,of reducing sugars was carried out by the procedure of ©tilfg,Peterson and Fred 41926) (d) Amide nitrogen was determined by d i s t i l l i n g aliquots of the 2% hydrochloric acid extract with sodium hydroxide. (12) (e) Lignin was determined by the method of Ritter et a l (19J2) for reasons explained in Part B. Page 28 • The method f i n a l l y adopted for the analysis of the 19 soils i s given as follows in detail: Carbon i n a l l samples was determined by wet combustion and nitrogen by the standard Kjeldahl procedure. Twenty grams of s o i l from the AQ horizons, 40 grams from the Ai horizons, ground to pass 40 mesh, were extracted for 48 hours i n a Soxhlet. apparatus with 50:50 alcohol-benzene. The material soluble in alcohol-benzene after removal of tne solvent was dried over calcium chloride ~ to constant weight in a desiccator and reported as " l i p i d ? . The residue was transferred to a l i t r e florence flask refluxed with 200 o.c. of water for 4 hours and f i l t e r e d by suction in a Bu&hner. The f i l t r a t e on cooling was made up to 500 o.c. Total nitrogen was determined after concentration of one aliquot by the Kjeldahl method. Another portion of the extract was concentrated and evaporated down to dryness on\ a steam bath, dried in the oven for 1/2 hour and weighed, then ashed and weighed again. The total ash free organic matter and total water soluble nitrogen was calculated for the whole sample. (13) The residue from the Buchner funnel was transferred to the boiling flask and 300 o.c. of 2% hydroohlorio acid added. This mixture was boiled under reflux for 5 hours. After cooling the f i l t r a t e was made up to a known volume* 25 c.c. of this solution was withdrawn and neutralized with 3% sodium hydroxide to the bromg thymol blue end point. The precipitated iron and aluminum hydroxides were f i l t e r e d off and the solution made up to 50 c.c. Reducing sugars were det-ermined on neutral iron and aluminum free extracts by the method of Sti l e s et a l (1928). The weight of reducing sugar calculated as glucose i s reported as "hemioellulose'V Amide nitrogen was determined by d i s t i l l i n g another aliquot with sodium hydroxide. Total nitrogen was determined on a third aliquot of the HCL extract. The residue after Mcl hydrolysis was dried in the oven and weighed. Ten grams of residue from A^ horizons and 3 grams from AQ horizons were transferred to a 100 c.c. glass stoppered conical flask, 25 c.c. of 72%H2SK>4 were added and allowed to stand for 2 hours at 20°0. as recommended by Kitter et a l (1932). The contents were transferred to a l i t r e flask and diluted to make 3% H2SO4. The solution was boiled for 5 hours under reflux. On oooling and f i l t e r i n g reducing sugars were determined as before and reported as cellulose (14) on the basis of the whole sample. The residue from the f i l t e r was transferred to ta?ed; dish and weighed and carbon (wet combustion) nitrogen (Kjeldahl) were determined. Using Waksman* (1930) formula the "lignin-protein" complexes were calculated for the original sample* (15.) DISCUSSION OF THE VARIOUS FRACTIONS 1. Alcohol-benzene soluble fraction* Treatment of s o i l with alcohol-benzene mixture removes the fats, waxes and resinous substances. 2. Water soluble fraction. The nature of organic oompounds dissolved by hot water i a quite indefinite. Shorey (1930) points out that such material may be predominately organo-aluminum compounds from the colloidal complex. He further points out that the quantity of water soluble materials increases after treatment of the s o i l with solvents. 3« Hemicellulose. It i s recognized that no single determination can give a complete estimation of hemicellulose present i n organic matter. The hydrolysis method involving the use of 2% hydrochloric acid i s used in this work, i t being expressly understood that this determines those hemicellous whose sugar produots on hydrolysis are not destroyed by the acid treatment. How tar such a treatment i s a true estimate of the hemicellulose present i s impossible to say. (16) 4. Cellulose, Where both cellulose and li g n i n are being determined on the same sample conditions favourable for both determinations are not well defined. The hydrolysis method according to Shewan (1938) gives lower results than the Cross and Bevan Method (A.O.A.C. 1945) 5. Lignin-protein complex. The separation of cellulose and l i g n i n through the use of 72% sulphuric acid probably strongly affects the l i g n i n . Norman and Jenkins (1934) point out that Xylose cjind fructose w i l l polymerize into insoluble compounds in the presence of concentrated sulphuric acid thereby increasing the figure for li g n i n . Direct methods for determination of cellulose and l i g n i n i n plants and composts are suggested by .Norman and Jenkins 11933.) Since gashes are involved, the methods do not seem practical for routine laboratory analysis. A complete review of the methods of determination of hemicelluloses, celluloses and lignins i s given by Norman U937). (17) RESULTS AND DISCUSSION OF RESULTS The analytical results for percentages of carbon and nitrogen and for the carbon-nitrogen ratio of the soils examined are given in Table III. Examination of this data reveals that the percentage carbon i n the AQ horizons of the ^ rey Wooded and Pacific Coast soils i s higher than the percentage carbon in the A 0 horizons of the Shallow Black and Transition s o i l s . On the other hand, the percentages of organic carbon in the horizons of the Forest soils i s lower than the percentage carbon i n the A^ of the Shallow Black and Transition s o i l s . It appears that mineralization of the organic matter has been more complete in the grassland soi l s . This conclusion i s supported by data that has shown the surface layers of prairie soils to have a higher microbiological activity than the surface layers of Forest soils. (Vandecaveye and Katznelson 1940-Cook,194$). .Examination of Table III demonstrates the well recognized differences between the C:N of forest and grassland soi l s . The soils of the shallow black zone have a narrow C:N ranging between 6.05 and 29.7 f soils of the transition zone also have a narrow C:N ranging between 8.3 and 24.6, and soils of the Wooded and Pacific Coast zones have a wide C:N ranging between 17.6 and 58. (18) TABLE I I I PERCENTAGE CARBON, NITROGEN AND C:N of the SOILS UNDER STUDY Zone Association Horizon Depth % Organic C %Total N C:N Dawson Al 2-7" 15.6 1.01 15.4 Shal low Nulki AjUpper 0-1" 12.5 0.777 16.1 Blac k Nulki A^Lower 1-6" 15.6 0.980 15.9 Pinchl A 0 0-2" 25.0 0.842 29.7 Pinchi Al 2-5" 11.3 0.977 11.6 Driftwood A l 2-5" 5.20 0.797 6.05 Barret A0 1-2" 41.8 1.19 35.1 Barret A l 2-4" 3.48 O.136 32.9 Grej Vanderhoof Ao 2" 58.3 1.46 39.9 Wood led Vanderhoof Alberta, Grey-A l o-e» 3.44 0.156 22.0 Wooded A 0 0-2" 21.6 I .036 20.4 Alberta, Brey Wooded Al 2-4" 4.15 0.233 17.8 Port St.James A l 0-2" 6.15 0.349 17.6 Doughty Ao variable i 41.6 1.21 38.6 Telkwa A 0 0-|2 18.8 2.24 8.3 Telkwa Al i - 4 » 8.10 0.463 17.4 Trar isitioE Alberta Transit-ion Ao 2" 30.4 1.24 24.6 Alberta Transit-ion A l 2-4" 5.00 0.477 10.5 Pacific Coast [t'akelse-' A^ 0-2" 58.2 1.04 58.1 (19) The relationship of vegetative types to C:N i s illustrated by these examples: Driftwood under a gross vegetation with few poplar and no conifers has a 0:N of 6, Fort St. James under poplar with some grass has a C:N of 17.6 and Lakelse under coniferous forest only has a 0:N of 58 .1 . The results of the proximate analysis for the 19 soils studies are recorded in Table IV. The figures for each fraction are averaged on the zonal basis for both the AQ and A± horizons of each association i n order to make comparison somewhat easier. It i s strongly emphasized that the values i n terms of " l i p i d s " , "hemicellulose", " c e l l -ulose", "lignin" and "protein" have significance only as accorded them in other studies of this nature. The use of these terms does not imply either that the fractions so designated consist solely of the chemical substances of these classes or that the recovery of chemical compounds of these classes has been quantitative. Examination of Table IV shows differences in the constituents recovered from s o i l associations within a zone and from the horizons within the s o i l associations. Although none of these differences are striking at f i r s t glance they may be significant. The " l i p i d " ' fraction i s highest in the wooded soils as might be expected considering the amount of resins in coniferous debris. The appearance of the alcohol-benzene soluble materials from the various TABLE VT PROXIMATE ANALYSIS OF SOILS UNDER STUDY Zone Association Horizo 4 Organic Matter Percentage Based on Organic Matter (Oxl»724) Lipid Water Soluble Hemicell-ulose Cellu-lose Llgnin Nitrogen Complex (Nx6.25) Recovery Shallow Black Grey Wooded Dawson Nulki Nulki Pinchi Pinchi Driftwood AjUpper AjLower Average Ao it Barret Barret Vanderhoof Vanderhoof Alberta Grey Wooded n Fort St.James Ao -A, A. A-, Ao Uoughty Average n Grey Black Telkwa Transition Alberta Transition Average Pacific Coast Lakelse A, A, A-, 2£.9 21,6 26.9 42.8 19.5 8.9 1*67 4.32 2.32 3.21 2.97 3.90 2.85 3.80 4.12 3.23 3.78 2.56 15.8 12.7 6.13 21.0 17.7 28.9 3.76 2.76 5.51 3.32 71.8 -6.0 -100,0 5.92* 37.1 „ 7.13^ 10.6 ^ 5.72 6.34 4.90 2.36 4.20 8.50 3.22 8.00 3.23 3.44 2.69 6.20 2.52 3.92 71.9 7.23 5.34 3.67 32,2 ' 14.0 / $2.3 8.62 100.0 1.72 1.40 2.94 3.08 2.33 2.24 4 .28 3.78 6.65 6.17 3.32 2.84 6.50 4.50 5.41 1.01 16.8 17.1 26.2 10.4 10.1 8.021 11.4 10.7 6.15 18.3 16.5 8.80 16.8 15.7 20.01 17.6 18.4 16.6 8.19 7.034 4.70 2.86 13.1 11.8 20.7 37.9 33.1 48.9 36.2 39.4 30.8 12.4 20.6 17.7 8.41 16.8 10.3 8.90 10.5 34.6 39.2 14.5 14.3 6.98 Trace 3.28 8.29 7.14 10.7 1.71 42.7 38.6 43.2 29.5 53.4 48.1 52.9 5.77 14.5 13.8 23.5 9.41 11.1 13.5 77.7 81.2 82.9 87.05 92.5 97.1 91.6 78.3 78.5 79.6 87.8 82.6 8O.7 5.027 60.5 7 . i 4 5.60 5.17 50.0 42.2 4.00 1.041 2.28 5.34 3.14 3.19 7.00 38.3 43.3 51.1 50.8 44.7 47.0 ?1.H 9.09 15.6 11.3 12.6 7.50 7.15 9.40 9.87 27.? 103.0 48.3 77.4 86.5 90.4 80.0 (21) s o i l zones shows some interesting differences. These extracted materials were a reddish brown and/acid to litmus i n the forest soils,and a canary yellow and neutral to litmus in the Shallow Black and Transition s o i l s . The significance of these observations i s not f u l l y appreciated at the present time. Perhaps after further investigational work organic matter may be characterized by the chemical nature of the " l i p i d s " . Water soluble constituents are higher in the A-^  horizons of a l l soils regardless of zone, but the i n -definite nature of the substances involved reduces the significance of this observation. Attention i s drawn to the extremely low water soluble oontent of Lakelse A Q # This s o i l i s formed under an annual precipitation of 70 inches. In a proximate analysis of Western Washington prairie s o i l s , (Fower and Wheeting 1941) found a correlation between r a i n f a l l and water soluble constit-uents. There i s no apparent differences between the "hemicellulose" and "cellulose" contents within the 4 s o i l zones. Results of both these fra'ctions are, in fact, very inconsistent. However, the decrease in both "hemicellulose" and "cellulose" from the AQ to the A^ horizon of a l l soils regardless of zone seems to be significant.. I t w i l l be noted that the cellulose oontent (22) in most cases i s lower than the hemicellulose. Cellulose being one of the main energy sources for micro-organisms, i s broken down rapidly during decomposition of plant remains. The hemicelluloses, on the other hand, are made up chiefly of pentosans, hexosans andpolyuronldes that are quite resistent to decomposition (Waksman and Diehm 1931a 1931b).Polyuronides* increase on decomposition of plant remains because of extensive synthesis by micro-organisms (Norman 1941). For these reasons, the "hemicelluloses" are usually higher than "celluloses"• And according to (Waksman et a l 1928) comparison of the decomposed l i t t e r with a variety of fresh plant materials shows a marked accumulation of "hemicelluloses". The "lignin" content on the average, i s higher in the Grey Wooded so i l s . Vandecaveye and Katznelson (1940) found this tendency in an examination of Washington zonal soils by the proximate analysis. The "lignin" content in the AQ horizons of the Shallow Black so i l s i s somewhat lower than the "lignin" in the corresponding A-j_ horizon. In the wooded soils the situation i s the reverse. The differences between A Q and A^ in Shallow Black s o i l s may be due to increased decomposition as was pointed out previously. Results for nitrogenous complexes are rather inconsistent but a general trend for a higher value in the A± horizons i s demonstrated. The recovery of constituents varied between 77% and 102% of the total organic matter with a mean recovery of 85%. ( 2 3 ) , This recovery agrees closely with those reported by Gross (1947) and DeLong and Salisbury (1940) but i s relatively low. This may be due to solution of "lignin" in the acids used for hydrolysing the "hemicellulose" and " c e l l -ulose". Waksman and Hutchings (1935) have previously reported such a loss i n the fractionation of organic matter of podsol s o i l s . They attempt to make a correction for the amount of "lignin" dissolved by analysing the acid f i l t r a t e s for total carbon, subtracting the carbon equivalents of the amounts of "hemicellulose", "cellulose" and hydrolysed "protein" found present in the hydrolyzates, and calculating the remainder of carbon to "lignin". Even then, the assumption that a l l of the residual carbon i s lignin derived i s scarcely ju s t i f i a b l e . The factor 1.724 x C i s for organic matter i s arbitrary and may vary between 2.20 and 1.79 x c for high carbon soils i s shown by Lunt (1936). In table V the nitrogen distribution of the various soils are expressed as per cent of the total nitrogen in the whole s o i l . Nitrogen soluble in 72% sulphuric acid was not determined because of the low recovery on several extracts taken at random. This nitrogen fraction i s included in the fraction, "nitrogen unaccounted for." The results for water soluble nitrogen i n Barret A Q and Alberta Grey Wooded s o i l A^ ^ are rather surprising since 24.9% and 2017% of the total nitrogen present i s water soluble. No explanation can be offered for this fact. "Protein" nitrogen TABLE 7 (24) NITROGEN DISTRIBUTION IN THE SOILS STUDIED (Expressed as % Total Nitrogen) IT Hcl .'Soluble Zone Association Horizon Water Soluble' N. Non Amide N. Amide J L Protein Nitrogen Nitrogen Unaccoun-ted for Shallow Black Grey Wooded Dawson Nulki Nulki Pinchi Pinchi Driftwood Barret Barret Vanderhoof Vanderhoof Alfrerta Grey Wooded Fort St .James Doughty Telkwa Black-Grejf Telkwa Alberta Transition Transitioi Pacific Coast I Lakelse Al AjUpper 6.30 9.80 AiLowex|13.1 10.3 10.0 o Al Al A0 A l A0 Al Ao A l A 0 A A Al 24.9 8.55 4.80 10.7 5.71 20.3 3.10 8.25 5.25 10.3 12.5 14 .7 25.2 8.52 21.1 9.7 10.3 17.7 16.7 8.53 12.01 17.3 1.87 15.7 10.6 17.1 23.3 21.4 8.15 35.8 14 .2 32.8 15.5 14 .5 25.2 8.33 30.4 22.1 8.16| 12.1 15.4 13.5 9.50 64.4 46.2 58.3 47.5 51.5 48.0 43.5 53.6 45.2 64.5 34.0 70.1 53.7 57.6 67.4 63.4 -1.1 7.2 14 .8 -2 .3 7.4 a 7.6 -5.5 10 .7 2.8 2.3 8.9 -0.27 -0.68 -0.35 0.64 2.5 (2$) or nitrogen insoluble i n 72% sulphuric acid accounts for 34-70% of the total nitrogen of the soils examined. Although there are no apparent differences between zones, as in "lign i n " (Table I Y ) there i s a marked tendency for accumulation of protein nitrogen i n the A-L horizons. CONCLUSIONS Although the results of the proximate analysis do not show striking differences between the zonal soils studied some interesting results have been demonstrated. From a study of percentage organic matter i t appears that the soils of the Shallow* Black and Transition zones are more completely mineralized than the soils of the Grey Wooded and Paci f i c Coast zones. In demonstrating increased mineralization and hence increased intermixing of mineral and organic fractions, the organic matter of the grassland soils may be classified as a mull type while that of the Wooded s o i l may be classified as a mor type. There was no significant differences i n "hemicellulose" and "cellulose" between the soils of the 4 zonal groups, but the "lignin" content of the Grey Wooded soils i s higher than that in the Grassland s o i l s . A comparison of differences between the AQ and Ai_ horizons of a l l soils indicate rather clearly: decreased "hemicellulose and "cellulose" and increased "li g n i n " and (26) nitrogen complex in passing from the AQ to the A^ horizon. Fractionation of nitrogenous compounds gave results too inconsistent to be significant. The proximate analysis of the Driftwood s o i l sug-gests that this s o i l should not be c l a s s i f i e d as Shallow Black but should perhaps be included in the Black-Grey Transition group. The value of the proximate analysis for the study herein described i s questionable. There i s need for the adoption of methods less empirical than those used i n the proximate analysis. (27) PART B. STUDY OF LIGNIN IN ORGANIC MATTER OF BRITISH COLUMBIA SOILS. Review of Literature Lignin i s found mainly in the secondary wall and pargly i n the middle lamella of the plant. There has been much speculation as to the origin of li g n i n and the mechanism of l i g n i f i c a t i o n but the scope of this work does not provide for a detailed discussion of these theories. However i t may be mentioned, that two of the recent theor-ies on lignin formation are given in detail by Freudenberg (1939) and Hibbert (1942). Methods of Determination and Isolation of Lignin. Since lignin has a very restricted s o l u b i l i t y the methods adopted for i t s isolation are more or less drastic, and may bring about changes, the nature of which, are not known. Through the action of concentrated acids in the cold, cellulose, hemicellulose, and other polysacchorides pass into solution. The lignin remains behind and i s fi l t e r e d off, dried at 105°C and weighed. A correction for ash and protein i s usually applied to the weighed product. Varying strengths of sulphuric acid from 65% to 80% have been used from time to time. But 72% sulphuric acid has been found to give most satisfactory results and i s recommended by the A.O.A.C. (1945). The conditions under which the determination i s carried out has been the subject of much research and those set down by Hitter et a l (1932) are generally followed. They stress 3 important points in (28) making the lignin determination: contact time of 2 hours, constant temperature of 20°C and f i n a l hydrolysis of sol-uble constituents in 37» sulphurio acid for 4 hours. Norman and Jenkins (1934) emphasize the necessity for s t r i c t adherence to these conditions since,as they point out, certain sugars, particularly xylose and fructose and sucrose by reason of i t s fructose content give an insoluble residue on standing i n 72% sulphuric acid, i'he disturbance caused by these sugars increases i f the time of contact with the acid i s prolonged but i s not serious i f limited to 2 hours at 20°C. The nature of the condensat-ion products i s discussed at length by the authors. Another method in which a l l other constituents are dissolved out with 42-43°% fuming hydrochloric acid has been described by Willstatter and Kaeb (1922) and the product so obtained from this treatment i s called "Willstatter" lignin. Since the action^fuming hydrochloric acid is about the same as concentrated sulphuric acid no particular advantage is gained tnrougji i t s use. A lignin residue called "Freudenberg lignin" has been obtained through the dissolving of the cellulose and hemicellulose of l i g n i f i e d tissue i n cuprammonium solution. As the name suggests the metnod was devised by Freudenberg et a l (1928). A number of methods based on the solution of the l i g n i n by solvents and the weight of the dissolved portion (29) calculated as lignin have been described. The commercial preparation of cellulose from wood depends upon the fact that on heating the wood with sulphites delignification occurs through the formation of soluble ligno-sulphonic acids. The method of lignin determination based on the sulphurous acid reaction i s not generally used since some of the cellulosic compounds are dissolved. Mild alkaline conditions have also been used for the extraction of l i g n i n . In such cases, the material i s treated with alcoholic sodium hydroxide under pressure and the dissolved l i g n i n i s precipitated by neutralization. This method is extremely effective in removal of l i g n i n for obtaining a lignin free cellulosic residue, but for the determination of lignin degradation of polyuronides adds to the error and for this reason i s not recommended (Phillips 1927). Lignin i n S o i l Organic Matter. The occurrence of lignin in organic matter can be demonstrated through the application of the well known qualitative tests for native l i g n i n . Shorey and Lathrop (1911) show that me/tfctasyl i s present i n organic matter. Some of the microtests for native lignin such as the phlorglucinal test and resorcinal test have been successfully applied to the lignins in the s o i l (Shorey 1930). The presence of a complex insoluble in sulphuric acid, has already been shown in part A of this paper and Norman and Moody(1940) using a number of delignification procedures, have demonstrated (30) the presence of lignin in the organic fraction of s o i l horizons AQ and A 1 # Biological Decomposition of Lignin Many conflicting and contradictory statements have been made in regard to the availability of lig n i n to microbial attack and the general consensus of opinion i s that isolated lignin at least i s unavailable. (Norman 1937.PP.177). But since a l l methods of lignin isolation involve the use of drastic reagents the Unavailability of isolated lignin cannot be taken as a criterion for (inavailability of lignin Infeitu* > Certain specific fungi are capable of decomposing lignin i n the plant, as, for example wood destroy-ing fungi (Norman 1937* pp.179, the edible mushroom, Psalliata camnestris Waksman and Nissen (1931) and species of Coprinus,Waksman (1931). Boruff and Buswell (1934) show that "Klason" l i g n i n added to an actively fermenting glucose media stops the gas production instantly and further additions of glucose w i l l not revive the process. Similarly a l k a l i lignin has a restrictive action on microorganisms as was demonstrated by Levine et a l (1933). Phenol li g n i n has been shown, surprisingly enough, to be decomposed by a number of -bacteria and fungi. (Waksman and Hutchings 1936). Bartlett and Norman (1939) show a decrease in methoxyl content as decomposition proceeds in compost heaps and attribute this fact to microorganisms. Synthesis of lig n i n by Microorganisms. The presenoe of lignin-like complexes in some s o i l fungi (3D was demonstrated for the f i r s t time by Thorn and P h i l l i p s (1932) and later the a b i l i t y of fungi to synthesize these complexes was studied by Pinck et al(l943). Cladisporium and Helmlnthosporium species were shown to be capable of synthesizing a 72% sulphuric acid insoluble complex from glucose. This complex comprised from 16.6-23.9% of the total dry weight of the mat. Other genera including Aspergillus, Gliocladium and Alternaria also synthesized l i g n i n i n lesser amounts. The l i g n i n synthesized by fungi differed chemically from native lignin in that i t contained less methoxyl. Practical Significance of Lignin i n S o i l The base exchange capacity of organic matter layers was studied by Mitchell (1932) who found that 40% - 70% of the total exchange capacity of organic soils could be attributed to the organic fraction and i n this l i g n i n plays a major role. Miller et a l (1936), too, concluded that the exchange capacity of organic soils i s significantly correlated with lignin content and that the total exchange capacity increased with decompos-i t i o n . McGeorge (1934) verified this observation and stressed the low total exchange capacity of fresh plant materials. Waksman and Hutohings(1935) while investigating the function of lignin in the preservation of nitrogen in soils suggested that the aldehydic groups of lignin combine (32) chemically with the amino groups in protein forming a ligno-protein complex of the nature of a Schiffs* base. This complex i s stable in the presence of 72% sulphuric acid and contains 30%-70% of the s o i l nitrogen as has already been shown by the proximate analysis. Since organic matter i s of paramount importance in a s o i l , and since l i g n i n or lignin-like complexes comprise 30-70% of the organic fraction in a s o i l , and since l i g n i n i s by no means f u l l y understood there i s a real need for further study on the chemical nature and practical signif-icance of lig n i n in organic matter. Recent Advances in Lignin Chemistry. Researches devoted to a study of the composition of plants during recent years have disclosed that aainarked difference exists between the lignins Isolated from gymnosperms or softwoods and those isolated from angiosperms or hardwoods. Hibbert and co-workers (1939) for instance have shown that in the lig n i n from angiosperms there are present both the 4 hydroxy-3-methoxyphenyl and the 4 hydroxy-3-$-dimethoxyphenyl nuclei; whereas in the lignin from gymnosperms only the 4-hydroxy-3-methoxyphenyl nucleus i s present. Thus employing an ethanolysis procedure attgiosperm lignins yielded a mixture of compounds I, II, III, 17 and V while lignin from gymnosperms obtained in similar manner gives i n addition the corresponding syringyl analogs VI, VTI, VIII and IX. The oombined yields of pure products from angiosperms and gymnosperms amounted to 9.7% and 3% respectively. (33) / \ ? V u I 2 ethoxy - 1 - (4 hydroxy -3-methoxyphenyl)-l-propanone C H - ^ H o f 1/ Ho< ) - C - C - C M 3 II 1 ethoxy - 1 - (4 hydroxy - 3 - methoxyphenyl)-2-propanone CH3< o © « i/ C — C — C H 3 III l-(4-hydroxy-3-methoxyphenyl) 1-2 propandione CH3Q O l - ( 3 hydroxy-4-methoxyphenyl) 2-propanone c«3<\ V Vanill i n (34) O H II I 71 2-ethoxy - l(4-nydroxy -3,j>,-dimethonypnenyl) 1-propanone, / y—~\ t ? VII 1(4 hydroxy-3,5-dtmethoxyph.enyl) 1,2, propanedione. VIII 1 (4 hydroxy-3.3 dimethoxyphenyl) 2 propanone. CH3C{ CH3a i x . Syringaldehyde. Freudenberg et a l (1940) employed a nitro-benzene oxidation technique that gave from spruce lignin v a n i l l i n V only i n 20% yield. Maple lig n i n gave a mixture of v a n i l l i n V and syringaldehyde IX in ratio 1:3 and in yields as high as 33% of the i n i t i a l Klason li g n i n . With the foregoing data in mind i t was considered worth while to Investigate the possibility of applying one of these lignin techniques to s o i l organic matter. Should such a procedure be applicable i t might perhaps enable one to determine the character of vegetation from which the organic horizons of some of the degraded soils have been derived and so provide another basis for differentiation of s o i l s . ( Lignin means of 72% sulphuric acid. ) EXPERIMENTAL The Freudenberg oxidation technique as described by Creighton et a l (1944) was used i n a study of the following s o i l organic residues and plant materials; Description of Samples Soils. Dawson A^ - See description page 8 • Vanderhoof AQ - " M " 9 . Daughty A Q - • » * 9 . Forest L i t t e r - Decomposed needles, twigs etc. from U.B.C. Forest floor. Woods and Straw Douglas F i r Sitka Spruce Rye Straw (36) Procedure and Description of Procedure The samples were ground in a Wiley mill.pass a 60 mesh sieve. The air dry meal was extracted in a Soxhlet for 48 hours with a 50-50 alcohol-benzene mixture, 12 hours with ethanol and 6 hours with hot water. The extracted material was dried f i r s t by suction and then by low heat. Duplicate two gram samples of the extracted air dry meal were used for determination of moisture. Twenty grams of extracted meal, 12 ml. of nitrobenzene and 400 ml. of 8% sodium hydroxide were placed i n a steel bomb (Figure 1) and heated to l65°C. i n an o i l bath. The bomb was then transferred to the shaker and oven (FigureIII) where the bomb temperature was maintained at l60°C. for 3 hours with violent shaking (300 strokes per minute). After cooling, the contents were f i l t e r e d at the pump and the residue washed with 8% sodium hydroxide and fi n a l l y with water. The washings and f i l t r a t e were acidified with sulphuric acid to ph 3 and the resulting mixture continuously extracted for 48 hours with benzene. The benzene extract was shaken with 20% sodium bisulphite for | hour. The bisulphite extract was acidified and sulphur dioxide removed under reduced pressure at room temperature u n t i l no odour of the gas could be detected and then f i l t e r e d and made up to 500 ml. F i f t y ml. of the bisulphite solution were taken for the determination of total aldehydes by adding 10 grams of sodium acetate FIG- I STEEL BOMB c (39) and a solution .23 grams of m nitrobenzoyl hydrozide in 25 ml. of water. The hydrozones form almost immediately at 60°C. The precipitate was allowed to stand at 60°0 for h hour and at room temperature over-night. The hydrozones were f i l t e r e d , washed with d i s t i l l e d water and dried over anhydrous calcium chloride and weighed. The remainder of the bisulphite solution was extracted for 48 hours with benzene and the solvent removed. The resulting o i l s were dried for 15 minutes in vacuum and stored in a desiccator. Vanillin and syringaldehyde were separated by adding a weighed amount of o i l s (about .4 grams) to a sublimation tube (Figure II) f i t t e d with a cold finger. Vaouum equivalent to about 1.5 mm. was applied and the sublim-ation temperature kept at 6 l°0. by means of a chloroform bath for 5 hours. The va n i l l i n sublimate was removed by means of dry ether and the solvent removed. The va n i l l i n was weighed and tested for melting point depress-ion. Vanillin in the o i l s was then calculated and syring-aldehyde determined by difference. Considerable preliminary work on the procedure was necessary before the data of Creighton and co-workers for rye straw and spruce wood could be duplicated. Temperature of Bomb At the outset about 1 § hours was required to heat the bomb to a temperature of l60°C. in the oven but as (40) poor yields of aldehydes from rye straw were obtained (Table 71) another method of heating had to be devised. In this method the sealed bomb was immersed i n an o i l bath at about 150°C. The temperature of the bath was then raised to l63°C. and the hot bomb quickly transferred to the preheated oven. This pre-treatment substantially reduced the time required for heating to the desired temperature and at the same time greatly increased the aldehyde yield as indicated i n Table VI. Extreme care must be exercised owing to the danger of explosion due to the exothermic reaction of nitrobenzene as an oxidizing agent. TABLE VI OXIDATION OF RYE STRAW. Expt. Heat Treatment Speed of Shaking ^Strokes per min. Total aldehydes gm./20 gm.meal 1 Heating bomb in oven 300 3.2 2 Preheating bomb In o i l 300 23.1 It was also found necessary to maintain a constant temperature at l60°^ 1 ° for maximum yields. Preliminary work with Rye straw showed decreased yields where the bomb was heated by a gas oven the temperature of which varied between 155° 0. and 163° C. (41) FIG. I l l (42) Speed of Shaking Various speeds of shaking were tried but a speed of 300 strokes per minute has been used for a l l work reported. A higher speed may be desirable but 300 strokes per minute was the maximum possible for the shaking apparatus (Figure II) used, as serious vibration effects came into play beyond this point. Extraction of Aldehydes. Two other extraction methods were tried on the s o i l organic matter oxidation products but no aldehyde was recovered. There were: (a) Prolonged extraction with benzene at ph 8 as was recommended by Freudenberg (1940) (b) Extraction by refluxing with 5-20 ml. portions of triohlorethylene as recommended by Kurschner (1928). Oolorimetrio Determination of Aldehydes. Since the gravimetric determination of aldehydes i s extremely tedious and time consuming a colorimetric determination for Vanillin using Folin's reagent (A.0.A.C.1945) was used on the bomb extracts. Comparison of the gravimetric and colorimetric methods and spruce wood and forest l i t t e r extracts are shown in Table VII. Reference to these data shows too high a yield by the colorimetric method which suggests that some compound in the bomb extracts other than aldehydes i s reacting with Folin*s reagent. In an attempt to verify this idea the colorimetric procedure described by Estes (1917) was used on the bomb extracts. In both spruce wood and l i t t e r a bright red colour appeared instead of the (43) TABLE VII-VANILLIN BY DIFFERENT METHODS. Grams/20 grams meal Source Vanillin as m nitro- Vanillin benzoyl hydrozone by F o l i o s Spruce Wood 0.938 1.54 Forest L i t t e r Trace O.683 characteristic purple. A red colour according to Estes was produced by vanillic, acid. The significance of this fact w i l l be disoussed later. In view of these findings the colorimet-ric procedure appears to be of l i t t l e value for the determin-ation of total aldehydes. DATA AND DISCUSSION The results for the nitrobenzene oxidation of the samples previously described are shown in Table VIII>. Table VIII NITROBENZENE OXIDATION OF ORGiiNIC MATTER, VJOODS, AND RYE STRAW.  Based on Lignin "Source Lignin "A Total Aldehydes% Vanillin % Syring-aldehyde % Ratio: Syrlng-aldehyde to Van-i l l i n 1 Spruce Wood 20.3 21.4 21.0 None 2 Douglas F i r Wood 28.6 10.7 10.1 None 3 Rye Straw 19.1 23.1 12.6* 10.5 1:0.83 4 Forest L i t t e r 71.6 Trace - - -5 Doughty A Q 60.1 None - - -6 Dawson A± 10.3 None - - -7 Vanderhoof AQ 43.2 None - - -^ V a n i l l i n fraction contains p. hydroxybenzaldehyde Creighton and Hibbert (1944) (44) I n order to compare these r e s u l t s , data on the n i t r o -benzene o x i d a t i o n of a number of p l a n t species by Creighton et a l (1944) i s presented i n t a b l e IX. The r e s u l t s (Table V I I I ) f o r rye straw and spruce wood siaow a some-what lowor t o t a l aldehyde y i e l d than reported by Creighton and co-workers but the recovery of v a n i l l i n and s y r i n g a l d e -hyde based on the t o t a l aldehydes i s comparable. F i r wood was not examined by these workers but reference to Table VTII shows a good recovery of v a n i l l i n as based on t o t a l aldehyde, and no syringaldehyde. I n t h i s respect f i r wood has the same nitrobenzene o x i d a t i o n chemistry as the other angiosperms examined by Creighton. Data as presented i n Table VTII i n d i c a t e the absence of aldehydes except i n tr a c e amounts i n s o i l organic matter samples, although the same technique used f o r rye straw, spruce wood and f i r wood was employed. F u r t h e r i n v e s t i g a t i o n s w i t h f o r e s t l i t t e r u s i n g 20 gms., 15 gms., and 10 gms. of solvent e x t r a c t e d meal did not i n any case y i e l d more than a tr a c e of aldehyde. I t might be concluded then, that the groups i n v o l v e d i n the nitrobenzene o x i d a t i o n are a l t e r e d i n the normal process of organic matter decomposition i n s o i l to a degree gr e a t e r than has been normally suspected. Apart from the p o s s i b l e change i n the l i g n i n i t s e l f , s e v e r a l t h e o r i e s suspecting the inadequacy of the technique and suggested improvements are advanced: f r e e amino n i t r o g e n groups may r e a c t w i t h the aldehyde and thereby block the formation of W i l e t h i s t h e s i s was at the t y p i s t s the paper of G o t t l i e b and Hendricks(1945) became a v a i l a b l e . These authors r e p o r t t h a t nitrobenzene o x i d a t i o n of mucks y i e l d e d no c h a r a c t e r l z a b l e products. (45) TABLE IX NITROBENZENE OXIDATION OF GYMNOSPERMS (CREIGHTON ET AL,1944) .PLANT KLason Total Van i l l i n Syringal- Ratio Lignin% Aldehydes % dehyde % Vanillin: Syringald-Pioea glanea (White Spruce) 28.6 23.7 23.5 None Tsuga Canadensis (Hemlock) 31.1 23.2 22.1 None -Pinus strabus (white pine) 34.9 20.1 18.5 None -Thuja plicata (red cedar) 33.9 24.6 24.0 None -Toxus Canadensis (Gjrounnl Hemlock) 32.5 22.0 20.7 None -NITRO BENZENE OXIDATION OF ^ COTYLEDONS AQQar rubrum (Red maple) 22.0 46.0 10.2 34.7 1:34 Populus tremuloids (aspen) 17.4 44.7 9.4 32.1 1:34 Betuia luten (yellow birch) 19.6 44.9 11.0 33.7 1:31 Froxinus americana (white ash) 18.5 48.6 10.5 37.2 1:33 NITROBENZENE OXIDATION OF MONOCOTYLEDONS Rye straw 20.2 30.5 14.1*^ 15.3 1:00 Corn cobs 13.8 21.4 17.1 6.0 1:04 Corn stalks 19.9 17.8 9.5 7.8 1:0,8 a n i l l i n in monocotyledons also contains somepj-hydroxybenzalde hyde. the hydrozone. Pretreatment by steam d i s t i l l a t i o n of the bomb contents before extraction with benzene should remove the nitrogenous compounds. Since organic matter i s higher in ash than plant material and therefore heavier there may be d i f f i c u l t y in obtaining thorough mixing of the organic matter with the reacting solution. If such were the case increasing the severity of agitation beyond 300 strokes per minute might prove advantageous. The poss-i b i l i t y exists that oxidation of the C6-C3 units in organic matter lignin does not stop at the aldehyde stage but i s carried, as i s suggested by the Estes test, to v a n i l l i c and syringic acids. If this theory can be substantiated,methods for determination of the guaioyl and syringji radicals as the acids might be desirable. HYPOIODITE OXIDATION OF ORGANIC MATTER LIGNIN Norman and Peevey (1939) have suggested the use of hypoiodite as a means of studying li g n i n distribution in the s o i l . With this reagent as an oxidizing agent, consider-able differences were reported in respect to tne reactivity of the organic matter in the horizons of a profile and in the surface layers of the great s o i l groups. In view of their results i t was thought advisable to study the hypoiodite oxidation of the B.C. soils to see whether or not this reaction could be used to characterize the organic matter content of these s o i l s . (47) S o i l Samples Used (a) The samples of s o i l as used for proximate analysis were reserved for this study. (b) The lignin residues from the proximate analysis were included for comparison. Experimental The method i s that outlined by Norman (1943). One-half to five grams of s o i l , depending on the carbon content, was placed in a small glass-stoppered bottle (100-125 mis.) and 25 mis. of water added. After a further addition of 5 ml. of Et-Hcl solution (1 gram EC 10 ml. cone. Hcl made up to 100 ml.) the mixture was shaken and allowed to stand over-night. One m i l l i l i t e r of 1% starch solution was added and any free T% released from the K I titrated with o.l'N NagSOj from a burette. This correction was found necessary since certain soils were found capable of oxidizing KI to Ig. Th e volume of NagSOj was recorded, (not more than .5 ml. of this work and usually .1 ml.) Water was then added from a burette so that the veluBwof liq u i d i s brought up to 35 ml. (25+5*l+x sulphite t y waters35 ml) Fifteen mis. of 2N NaOH was pipetted in followed by 50 ml. of .IN I 2 . After being shaken, the bottle was placed in the dark and shaken by hand at approximately 10 minute intervals/ Aliquots of 10 ml. were withdrawn at the end of 1 hour and acidified with 10 ml. @f IN H 9S0 A for tit r a t i o n with .03 N Na 9S 90, (48) The iodine uptake was expressed as millfcequivalents of Ig per 100 grams of s o i l , per unit of organic carDon in the s o i l . The Nature of the Reaction Between Hypoiodite and S o i l  Organic Matter. In alkaline solutions Ig undergoes the following reactions: 2Na0H + I 2 -» NalO + 2NaI + H20 3NaI0 ~*> NalOj + 2 Nal Iodine behaves differently from other members of the halogen family since the conversion of hypoiodite to iodate i s complete within one-half hour. Therefore, the reaction of hypoiodite with s o i l organic matter i s not a simple quantitative one, but one which i s considerably affected by concentration of reactants. Also, the actual nature of the reaction with organic matter i s not clearly understood. Norman (1943) suggests that the point of attack may be the phenol OH group in the lignin molecule. However, i t i s known that hypoiodite oxidized the aldore group with formation of the corresponding acid.(Goebel 1927). Again, the CHj-C- group i s attacked to form iodoform in the well known iodoform test (AOAC 1945). In the present study a l l the reaction bottles smelled strongly of iodoform indicating that at least some of the hypoiodi-ce was convert-ed to this compound. Thus a q u a n t i t a t i v e determination of groups by means of iodoform may be valuable in (49) characterizing organic matter. At best then, the procedure i s entirely empirical with a l l the shortcomings of emp-i r i c a l determinations, with the additional disadvantage that the exact nature of the reaction i s not at present understood Data and Discussion of Data. The data for hypoiodite oxidation expressed as the ME of I2 P e r 1°0 grams of s o i l per unit of C. i s presented in Table X. In both the s o i l and l i g n i n residues, a rough correlation exists between the activity factor (me Ig j and the percentage organic carbon. In the "lignin residues" there i s a tendency for the A^ horizons of grassland soils to show greater activity than that from the corresponding A Q horizon. But, in the case of Pinchi, a grassland s o i l , the reverse i s true. This fact may possibly be explained by error in sampling. Norman (1944) pointed out that forest s o i l s showed higher reactivity than the grassland soils and this i s borne out by the data presented in Table X. With the Barret association^an exception^there i s a marked tendency for the wooded soils to show greater reactivity passing from the AQ to the A^ horizon. No real differences are brought out in the hypoiodite oxidation of lig n i n residues. TABLE X HYPOIODITE OXIDATION OF 1? SOILS AND LIGNIN RESIDUES. So i l Zone Soil Association Horizon Oven Dry S o i l m e I 2 lOOg m el2/100 g Oven Dry Lignin residue %0 me I g m e I2/lOO g lOOg Shallow Black Pacific Coast Dawson A l 15.6 108.0 6.90 14.4 75.0 5.49 Nulki AjUpper 12.5 87.0 6.93 7.36 58.5 7.95 Nulki A^Lower 15.6 94.5 6.03 13.4 75.0 4.71 Pinchi Ao 25.0 159.0 6.36 16.8 138.0 9.09 Pinchi A l 11.3 90.0 8.82 7.00 45.0 6.36 Driftwood A l 5.20 33.2 6.40 - - -Telkwa Ao 18.8 115.5 6.06 16.2 150.0 9.24 Telkwa A l 8.10 88.5 10.8 5.04 57.0 11.34 Alberta Transition Ao 30.4 258.0 8.49 34.0 102.0 3.0 tt A l 5.00 35.4 7.08 3.26 27.0 8.27 Barret Ao 41.8 450.0 10.8 62.4 306.0 4.92 Barret A l 4.48 41.1 9.78 2.24 16.2 7.20 Vanderhoof Ao 58.3 384.0 6.60 67.7 • 306.0 4.53 Vanderhoof A l • 3.44 35.4 10.2 2.43 27.0 Alberta - • - - ~ — -Grey Wooded Ao 21.6 198.0 9.18 20.6 270.0 13.1 ii A l 4.15 39.0 9.96 3.04 20.4 7.14 Doughty Ao 41.6 318.0 7.65 48.1 480.0 10.0 Fort St.James A l 6.15 78.0 12.7 5.71 108.0 18.6 Lakelse Ao 58.2 486.0 8.34 68.2 408.0 5.98 o (51) Conclusions The nitrobenzene oxidation carried out on rye straw, spruce wood and f i r wood yielded 10-25%, based on i n i t i a l l i gnin, of the aldehydes v a n i l l i n and syringaldehyde. Production of these aldehydes depended upon the maintenance of specific temperature and speed of shaking conditions during the oxidation. No aldehydes were formed in the oxidation of s o i l organic matter although the same technique for oxid-ation of rye straw and the woods was used. It i s suggested -that the chemical groups in the organic matter li g n i n involved in the oxidation process are changed i n some way upon decomposition so that the reaction i s blocked. Hypoiodite oxidation of the 19 soils and their l i g n i n residues from Part A show no consistent differences. Therefore, the value of this test for characterization of the organic horizons of Br i t i s h Columbia soils is questioned. (52) PART 0 DETERMINATION OF SOIL PIGMENT Review of Literature The fact that solutions of salts ammonium hydroxide and sodium hydroxide w i l l extract from organic matter a jet black to brown pigment or humus has been known for a long time. A great many ideas have been put forth concerning the nature of humus but as yet very l i t t l e i s known about i t s true chemical nature. Gortner (19l6a) concluded that humfls i s not a typical s o i l product since similar extracts can be made from undecomposed plant materials. He further pointed out that the pigment content of organic soils i s much higher than that of undecomposed vegetable material so i t may be concluded that humus extracted from s o i l does not consist entirely of pigmented dompounds but contains a large proportion of almost colourless substances usually masked by the ooloured compounds. Using different extracting solutions he (19l6b) observed that 4% sodium hydroxide, although i t dissolves approximately the seme weight of humus, does not dissolve the same quantity of coloured compounds as does 4% ammonium hydroxide. In an attempt to procure the pure pigment from the ammonia extracts he secured a product containing 37-47% ash (^Humus in this paper refers to the organic substances of soils soluble in ammonium and sodium hydroxides. ) (53) which he explained may be a contributing factor in the colour phenomena. The formation of humus in the s o i l i s described by Baoklay (1921) who states that the coloured material i s the result of carbohydrates reacting a with mineral acids to form hydroxymethylfurfural which condenses to form humus. Naturally, such an explanation i s highly theoretical and has been proven only to the point that hydroxymethylfurfural w i l l give a black condensation product. According to Gillam (1940) that fraction of the s o i l organic matter remaining following peptization by ammonia and precipitation by acid and insoluble in 95% ethanol i s the s o i l black pigment. Various pigment fractions, although isolated from soils of different s o i l groups, when subjected to such determinations as methoxyl content, acetyl number and $Qt@ntiORSt*?io tit r a t i o n were found to be remarkably consistent in chemical and physical properties. This suggests that the same central neucleus is present for each pigment. The formation of s o i l pigment as extracted by ammonia i s believed to be a function of such factors as climate, vegetation, topography, drainage and biological activity. Since i t i s well known that the zonal distribution of soils i s also based on these factors, methods for measuring the pigments have been worked out and the results correlated with the s o i l zones. Hock (1957) found that the humus extracted from Podsol and Black Earth s o i l s with sodium fluoride and sodium (54) oxalate gave vastly different oolourtone values "farbtonwert" as determined by a mercury vapor lamp. He suggests that behaviour of humus extracts on exposure to the mercury vapor lamp or other photoelectric measuring instruments could be used as a criterion of s o i l type. Gillam (1938) in a study of pigment values i n relation to temperature and precipitation demonstrated that for every f a l l of l8°F in mean annual temperature along the two isohyetal lines through the Central Plains the humus colour increases two or three times. With increasing precipitation along an isothermae line he observed that the humus colour increases proportionally. In this work, s o i l type and texture were constant. Experimental In the present work the colour value of ammonium hydroxide extracts of the 19 soils previously described in Part A were studied with a photoelectric colourimeter. Since a quantitative extraction of s o i l pigment with dilute ammonia i s well nigh impossible (Gartner 1916a, Gillam 1938, Shorey 1930) a modification of an indirect method suggested by Gillam (1938) was used. In this method a colourimetric procedure was employed since many workers including Alway and Pinckney (1911), Carr 1917» and Eden (1924) have concluded that i t i s sound i n principle. The method as modified i n this laboratory i s as follows: ten grams of a i r dry s o i l was mixed with an equal weight of pure quartz sand and placed i n a leaching apparatus suggested (55) by Shollenberger (1945). It was then leached with 1^ hydrochloric acid u n t i l no calcium could be detected in the leachate. One hundred f i f t y to 200 mis. were usually required. D i s t i l l e d water was then percolated through the so i l u n t i l a l l chloride ions were removed, about 150 ml. being required for this treatment. Finally a solution consisting of 4% ammonia hydroxide, and 2% ammonium carbonate was percolated through the s o i l and exactly 250 ml. of the jet black extract retained. The ammonia solution was fed through the extractor at a constant rate of 1.5 me per minute, this rate being closely adjusted by screw-clamps on the delivery tubes. Duplicate 10 ml. portions of the extract were determined gravimetrically for soluble organic matter and the percentage of ash free humus calculated for the whole sample. The required volume of extract was removed and diluted to 100 ml. to give 1 part of pigment and 10,000 parts of solution or 100 ppm of pigment. The colour values of the extracts were determined i n a Fisher Colourimeter. Data and Discussion of Data. From the data assembled in Table XI a comparison of hygroscopic coefficient, percentage humus and humus colour can be made for the various s o i l types. The hydroscopic coefficient i s included to show the colloidal nature of the soils which in a rough way i s a criterion of texture (Russel and McRuer 1927). It w i l l be seen that the A Q horizons have a hygroscopic coefficient higher than TABLE XI - HUMUS COLOUR OF THE 19 SOILS UNDER STUDY Zone Association Horizon Hygroscopic coefficient % Organic Matter % Humus Humus Colour Value. Dawson 5.47 24.9 4.20 54.0 Nulki AjUpper 4.96 20.9 2.75 66.0 Sha How Nulki A^Lower 4.17 24.9 3.25 68.0 Black Pinchi A 0 7.61 42.8 3.72 50.0 Pinchi A l 6.71 19.5 3.5 60.5 Driftwood A l 5.32 8.9 3.7 57.0 Barret Ao 11.4 71.8 7.09 19.0 Barret A l 3.51 6.0 1.25 23.5 Gre y Vanderhoof Ao 12.4 98.1 7.50 15.5 Woo led Vanderhoof Alberta A l 3.10 5.92 2.91 21.5 Grey Wooded Ao 6.64 37.1 5.50 22.0 Alberta Grey Wooded A l > 2.76 7.13 3.96 26.0 Doughty Ao 12.3 71.9 8.11 16.0 Fort St.James A l 7.49 10.6 3.5 55.0 Grey Black Telkwa V 5.72 32.2 5.00 70.1 Transition Telkwa 3,61 14.0 3.2S - 0O.5 i Alberta Grey Black Trans-i t i o n Ao 7.83 60.3 4.59 39.0 n Al 3.97 8.62 2.00 45.0 Pacific Coast Lakelse A o 13.2 90.1 8.08 22.5 U.B.C. Forest L i t t e r _ - - 7.25 25.2 (57) (58) -the Ai_ horizon samples. The percentage humus i n a l l samples i s f a i r l y well correlated with percentage organic matter. However, more humus i s extracted per unit i n the Al horizons than in the A Q horizons. The humus colour values are graphically illustrated in Figure IV. These oolour values show very significant differences between the forest s o i l s (Grey Wooded and Pacific Coast) and the grassland s o i l s (Shallow Black and Transitional). The differences manifest themselves in both the A Q and A^ horizons as i s seen by examination of Figure IV. Attention i s drawn to the fact that the s o i l s of the Black-Grey Transition Zone show humus colour values of the same order as the Shallow Blaok s o i l s . Although Fort St. James association i s tentatively cl a s s i f i e d as a Grey Wooded s o i l the high humus colour value suggests that i t might be placed i n the Transition Zone. The nature of vegetation and profile developement of this s o i l also supports this suggestion. It w i l l be seen that the humus colour of the A-^  horizons are consistently higher than that of the corresponding A Q horizons. This i s in lin e with Gortner's (1916a 19l6b) observations that humus colour increases with decomposition. (59) RELATIVE HUMUS COLOR o g on a x DAHSON NULKI PINCHI DRIFTWOOD TELKWA •v 111 11TA TRANSITION BARRET 3 D f-ri VANOCR ROOF O ALTA. GRCY O WOODED O n DOUGHTY O f r . j r . jAMa 5 ^ roRCST LITTER s x O J O N O Z . > o X O X) N O (60) Conclusion Relative humus colour of ammonium hydroxide extracts provides a ready means of distinguishing between the organic matter of forest and grassland s o i l s . In a l l soils examined, regardless of zones increased decomposition in the Aj_ horizons i s shown by a higher humus colour value than the corresponding A horizon. (61) SUMMARY. Part A.-Carbon oontent, carbon-nitrogen ratio .and a prox-imate analysis were determined on the organic matter of some representative British. Columbia and Alberta zonal s o i l s . Comparing s o i l zones carbon content and hence percentage of organic matter was higher in the A Q horizons of the Grey Wooded soils while that in the Ai horizons i s higher in the Shallow Black and Transition-al so i l s . The carbon-nitrogen ratio was narrower in the grassland so i l s . Although proximate analysis did not show startling differences between zones, certain differences seem to be significant: (a) Higher "li g n i n " nitrogen complex and l i p i d content in Pacific Coast and Grey Wooded s o i l s . (b) Percentages of "hemicellulose" and "cellulose-decrease in passing from the A© to the Ai horizon. (c) "Lignin and nitrogenous complexes concentrate in the A i horizons. Part B.-Nitrobenzene oxidation of s o i l organic matter from various sources yielded no characteristic oxidation products although excellent yields of v a n i l l i n and syringaldehyde were obtained from oxidation of spruce wood, f i r wood and rye straw. It i s suggested that the (62) groups involved in the nitrobenzene oxidation reaction are destroyed during decomposition of plant materials, or that, some shortcomings in technique were responsible for the i n a b i l i t y to isolate characteristic compounds. Hypoiodite oxidation of zonal soils and their l i g n i n residues showed ho consistant differences in the nature of the lignin. Oxidation by hypoiodite i s quest-ioned as a means of detecting differences in the constitution of the organic fraction of B.C. soils. Part C -Relative humus colour i s shown to be higher in the Shallow Black and Transitional s o i l s . This difference may be used as a criterion of s o i l type. Also the A]_ horizons of a l l soils examined show a higher humus colour value than the corresponding AQ horizon. (63) Alexander, L.T., and Byers, H.G, 1932 A oriticfc<i laboratory review of the methods of determining organic matter and carbonates in s o i l . U.S. Dept. Agric. Tech. Bui. 317. Alway, F.J., and Pinckney, R.M. 1911.' The photometric and colorimetric determination of humus. Nebr. Agr. Exp. Sta. 25th Ann. Rept. * Association of O f f i c i a l Agricultural Chemists, Methods of Analysis. 5th ed. 19*5. Washington, D.C. Bartlett, J.B. and Norman, A.G. 1939. Changes in the li g n i n of some plant materials as a result of decomposition. Proo. Soil Sci. Soc. of Amer. 3:210-216. Beokley, V.A.1921. Formation of humus. Jour Agric. Sci. 11:70-77. Boruff, C.S. and Buswell, A.M. 1934. The aneisrabio fermentation of l i g n i n . Jour Amer. Chem. Soc. 56:886. Bouyoucos, G.J. 1934. Method for determining the degree of decomposition that unknown decayed vegetable organic materials have already-undergone in nature. S o i l Sci. 38:477-82. Brickman, L., Pyle, J.J., McCarthy, J.T.,Hibbert, H.1939. Studies on l i g n i n and related compounds XXXIX. Ethanolysis of spruce and maple woods. Jour. Amer. Chem. Soc. 61:868-869. Carr, R.H. 1917. Is humus oontent of a s o i l a guide to f e r t i l i t y . Soil Sci. 3:515-524. Cook, F.D. 1945. The microbiological act i v i t y of profiles of Pineview, Vanderhoof and Nulki Clays. Unpublished undergraduate thesis. University of B r i t i s h Columbia. Creighton, R.H.J., Gibbs, R.D. and Hibbert, H.1944. Studies on li g n i n and related compounds LXXV. Alkaline nitrobenzene oxidation of plant materials and application to taxonomic classification. Jour. Amer. Chem. Soc. 66:32-37* (64) Creighton, R.H.J, and Hibbert, Harold, 1944. Studies on ^lignin and related compounds. LXXYI. Alkaline nitrobenzene oxidation of corn stalks. Isolation of p-hydroxybenzaldehyde. Jour. Atner. Chem. Soo. 66:37. Eden, T.A. 1924. A note on the colorimetric estimation of humic acid in mineral s o i l s . Jour Agric. Sci. 14:469-472. Estes, D. 1917. A new quantitative test and ooloremetric method for the estimation of v a n i l l i n . Ind. Eng. Chem. 9:142-144. Farstad, L., and Laird, D.G. 1943. S o i l survey of the central interior of B.C. Unpublished report, University of B.C. Fowler, R.H. and Wheeting, 1941. Nature of organic matter in western Washington Prairie soils as influenced by differences in r a i n f a l l . Jour. Amer. Soc. of Agron. 33 : 13-33. Freudenberg, K. Harder, M. and Markert, L. 1928 Ber. 6l :1760, as cited in Freudenberg, K. Polysacchorides and Lignin. Ann. Rev. Biochem. 8:81-112. Freudenberg, K. 1939. Polvsacchorides and li g n i n . Ann. Rev. Biochem. 8:81-112. Freudenberg, K. Lautseh and Ingler, 1940-Ber.,73:167. as cited in Creighton et a l . Jour Chem. Soc.66:34. Gillam, W.S. 1939. 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