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Open Access
Behavior of free amino acids in soil
(Colorado State University. Libraries, 1960-03) Putnam, H. D., author; Schmidt, E. L., author; Paul, Eldor A., author; Soil Science Society of America, publisher
The behavior of a mixture of amino acids in a soil environment was studied. Extractions were made with 80% ethanol. The extract was concentrated and then was analyzed for amino acids by gradient elution chromatography. After 1 hour of soil contact in the cold, at least some of each amino acid could be recovered, but the extraction was not efficient. Replicate soil flasks to which amino acids had been added were incubated at 28° C. under conditions that allowed for both CO2 and amino acid analysis of the same flask. After 24 hours, substantial degradation had occurred but at least trace amounts of each of the added amino acids except threonine could still be detected. Beta alanine appeared on the 24-hour chromatogram although it was not among the amino acids added initially. Results of both chromatographic analysis and CO2 collection suggested that nearly all of the added amino acids were degraded by the end of 96 hours. Separate studies using microbiological assay failed to confirm the persistence of threonine in soil as reported in the literature. The possibility that the beta alanine found in the soil environment was formed from aspartic acid decarboxylation was explored, but large additions of aspartic acid to soil did not result in substantial increases in beta alanine.
Open Access
Extraction of free amino acids from soil
(Colorado State University. Libraries, 1960-05) Paul, Eldor A., author; Schmidt, E. L., author; Soil Science Society of America, publisher
Alternatives to extraction with ethanol were examined in order to obtain more effective removal of free amino acids from soil. Ba(OH)2 was a promising extractant and proved to be very effective in recovering a mixture of 17 amino acids that had been added to soil. Resolution of the extract by elution chromatography was followed by colorimetric analysis; 73 to 121% of the acidic and neutral components of the mixture and 36 to 41% of the basic amino acids were recovered. A second extraction procedure, based on the use of NH4OAc, was developed to avoid any slight hydrolysis of amino acid polymers that may have occurred during preparation of Ba(OH)2 extracts. The NH4OAc extraction procedure was 31 to 83% effective in the recovery of added amino acids from soil. When both extraction techniques were applied in preliminary trials to characterize the free amino acids fraction of a soil, the NH4OAc extraction was considered the better. Both NH4OAc and Ba(OH)2 extractions yielded many more kinds of free amino acids in concentrations 5 to 25 times greater than that reported earlier in comparable studies using ethanol extraction.
Open Access
Formation of free amino acids in rhizosphere and nonrhizosphere soil
(Colorado State University. Libraries, 1961-09) Schmidt, E. L., author; Paul, Eldor A., author; Soil Science Society of America, publisher
Untreated samples of nonrhizosphere and soybean rhizosphere soils each contained about 15 identified free amino acids totaling 2 to 4 µg. per g. of soil; lysine was the most prevalent amino acid in each preparation. Numerous additional unidentified compounds occurred at concentrations estimated as 0.1 to 0.5 µg. per g. Treatment with glucose and potassium nitrate increased the amount of free amino acids to about 100 µg. per g. after 3 days. Concentrations declined after 3 days but still were 4 to 5 times that of the untreated control after 2 weeks' incubation. Glutamic acid was the dominant amino acid in all treated soils. Rhizosphere soil did not differ quantitatively from nonrhizosphere in samples treated with glucose, although a greater variety of ninhydrin reacting compounds was encountered in rhizosphere soil. Treated soils incubated at 20% field moisture capacity differed little in free amino acids from those held at 30%. The features of the free amino acid fraction are discussed.
Open Access
The influence of nitrogen on the decomposition of crop residues in the soil
(Colorado State University. Libraries, 1962-08) Lueken, H., author; Hutcheon, W. L., author; Paul, Eldor A., author; Agricultural Institute of Canada, publisher
Additions of mineral nitrogen accelerated the initial decomposition rate of incorporated wheat straw, alfalfa hay and glucose when added to two soils differing widely in organic matter content. However, in the more advanced stages of decomposition the reverse was true, and over the total incubation period larger amounts of carbon were maintained in soils supplemented with nitrogen. In contrast to all other residues used, nitrogen additions to cellulose effected a continuous and substantial increase in residue decomposition. This was the only residue for which the mineralization of soil organic matter did not supply nitrogen adequate for its decomposition within 120 days. The very slow rate of decomposition of sphagnum peat could be attributed to its high lignin content, rather than to the nitrogen levels. Sulphacetolysis analysis, which measures the non-humified carbon, indicated the feasibility of separating non-humified crop residues from the more complex soil organic matter. Addition of organic amendments thus resulted in a drop in the soil humification quotient. Nitrogen resulted in the retention of a significantly higher percentage of the added residue, without a drop in the humification quotient for the high organic matter Melfort soil. Residue applications to soils produced a significant improvement of structural development, especially in the low organic matter soil (Arborfield).
Open Access
Measurement of the polysaccharide content of soils
(Colorado State University. Libraries, 1963-01) Acton, C. J., author; Paul, E. A., author; Rennie, D. A., author; Agricultural Institute of Canada, publisher
The polysaccharide content of two soils, measured by precipitating and weighing the microbial gums from the fulvic acid fraction of soil organic matter, and by colorimetric analyses using anthrone, was increased appreciably during the incubation of samples with straw. Applications of nitrogen and phosphorus altered only slightly the amount of polysaccharides present. The polysaccharide content of the amended soils increased rapidly during the first week of incubation and then levelled off. Peptization of the soil with dilute alkali prior to acid hydrolysis substantially increased the carbohydrates measured with anthrone. The anthrone reagent which measures primarily hexoses indicated a soil carbohydrate content of 10–15 per cent occurring in a range of Saskatchewan soils. Thirty-five per cent more carbohydrate carbon was found using the less specific phenol-sulphuric acid reagent. The acetone precipitated fraction from the fulvic acids accounted for only 10 per cent of the soil carbohydrates and contained a large proportion of ash and other non-carbohydrate materials. The total acid-soluble base-soluble fraction, fulvic acids, contained 15–25 per cent; the remainder was distributed in the alkali insoluble humin — 55–70 per cent and the humic acid fraction 4–12 per cent.
Open Access
The influence of soil moisture, nitrogen fertilization, and temperature on quality and amino acid composition of Thatcher wheat
(Colorado State University. Libraries, 1963-07) Hutcheon, W. L., author; Sosulski, F. W., author; Paul, E. A., author; Agricultural Institute of Canada, publisher
The protein content of Thatcher wheat grown in the growth chamber was increased by reduced water supply, nitrogen fertilization, and higher air temperatures. Soil moisture conditions had a greater influence on protein content at higher temperatures, while the largest responses to nitrogen fertilization were obtained at the medium moisture level. Changes in sedimentation value and mixing time were associated with protein content except for plants grown at 62°F. Apparently the low temperature had an adverse effect on gluten quality. The relative distribution of 9 amino acids was significantly correlated with changes in grain protein content. Only 6 amino acids gave similar high correlations with flour protein content and sedimentation value. These differences are explained on the basis of changes in the morphology of the wheat grain and the proportion of flour proteins.
Open Access
The relationship of polysaccharides to soil aggregation
(Colorado State University. Libraries, 1963-07) Acton, C. J., author; Rennie, D. A., author; Paul, E. A., author; Agricultural Institute of Canada, publisher
Studies were conducted on two soil types to determine whether variations in level of aggregation, induced by adding wheat straw were accompanied by significant changes in the polysaccharide content of the soils. The addition of finely ground wheat straw to the soils, followed by varying periods of incubation, markedly improved the level of aggregation in both soils. Where nitrogen was added together with the straw, the percentage of aggregates > 0.5 and 0.1 mm. diameter was reduced significantly as compared to the straw treatment alone. The data indicate that maximal structural improvement due to straw additions can only be attained where N is maintained at a relatively low level. The level of aggregation of the variously treated soils was shown to be approximately 35 per cent dependent on the 'microbial gum' content of the soil samples. This low level of correlation was due m part to the fact that the maximum level of aggregation was attained at a different sampling period than maximum accumulation of 'microbial gum'. Also, appreciable contents of polysaccharides were found in the humin and humic acid as well as the fulvic acid fractions of the soil organic matter. It is concluded that level of aggregation is a function, not only of the microbial gum content of the soil, but also of the carbohydrate carbon content of the numic acid-humin fraction.
Open Access
The effect of various clover management practices on gaseous N losses and mineral N accumulation
(Colorado State University. Libraries, 1963-08) Aulakh, M. S., author; Rennie, D. A., author; Paul, E. A., author; Agricultural Institute of Canada, publisher
A 2-yr field study was carried out to assess gaseous losses of N as N2O + N2 from two Black Chernozemic soils, where during year 1 wheat was underseeded to clover and in year 2, the clover in late June was (a) green-manured and the field fallowed, (b) harvested for hay and then fallowed, or (c) harvested for hay and allowed to regrow. Gaseous losses during year 1 were small and ranged from 1.3 kg N∙ha−1 (Blaine Lake clay loam) to 4.7 kg N∙ha−1 (Hoey clay loam). Gaseous losses were somewhat higher during the second year, but differences between the various clover management practices were generally small. The contribution of lower soil horizons towards gaseous nitrogen losses were shown to be negligible. Soil moisture, mean air temperature, nitrate + nitrite, and ammonia N concentrations collectively accounted for 37–66% of the variations in N2O fluxes. It is concluded that incorporation of clover followed by a partial fallow results in substantially less gaseous loss of nitrogen than the standard summerfallowing practice, and at the same time significantly increases mineral nitrogen accumulation in the soil.
Open Access
Investigations of the dynamics of soil humus utilizing carbon dating techniques
(Colorado State University. Libraries, 1964) Rennie, D. A., author; Campbell, C. A., author; Paul, Eldor A., author; McCallum, K. J., author; Pub. House of the Academy of the Socialist Republic of Romania, publisher
The radioactivity of naturally occurring C14 in soil humus when compared to the C14 activity of a standard of recent origin (carbon dating) can be used to estimate the mean residence time of the soil humus in studying problems in soil genesis, fertility and biochemistry. The apparent mean residence time of humus from a Black Chernozemic soil was approximately 1,000 years. The C14 activity of "Humin" and "Humic Acids" isolated from this soil was lower than that obtained from the whole soil. The fulvic acids, however, had a substantially higher activity and a corresponding lower mean residence time. A Grey Wooded Podzolic soil sample, developed under different vegetation than the chernozemic, had mean residence time approximately 1/3 that of the chernozemic soil. Carbon dating techniques can also be used to study the dynamics of soil organic matter under differing cultural techniques and in soil biochemistry investigations. When integrating these data, factors such as isotopic discrimination and variations in the C14 content of the atmosphere must however be taken into consideration in all studies using this technique.
Open Access
Measurement of soil color
(Colorado State University. Libraries, 1966-02) Paul, E. A., author; Shields, J. A., author; St. Arnaud, R. J., author; Clayton, J. S., author; Agricultural Institute of Canada, publisher
The color of cultivated surface samples from Chernozemic and Gray Wooded soils were measured by visual and spectroreflectance methods. Variations in visual color measurements among different observers were of sufficient magnitude to represent serious errors in the application of the soil color criteria outlined in the Canadian soil classification system. Spectroreflectance measurements facilitated the accurate measurement and characterization of the Munsell renotations of Chernozemic and Gray Wooded soils sampled within their respective soil zones. The ratio of renotation value: renotation chroma of the Chernozemic samples (air-dry) were distinctly lower than those of the Gray Wooded samples. The presence of moisture caused a greater decrease in the renotation value of the Gray Wooded samples than it did in the Chernozemic samples. The renotation hue of most of the measured samples occurred midway between the 10YR and 2.5Y hue charts currently available in the Munsell soil color chart series. Color measurement of cultivated surface soil samples taken within the various soil zones of Saskatchewan indicated discrepancies between their renotation values and the color criteria currently suggested by the National Soil Survey Committee of Canada for the respective soils at the Order and Great Group levels.
Open Access
Effect of moisture, temperature, and nitrogen on yield and protein quality of Thatcher wheat
(Colorado State University. Libraries, 1966-04-28) Paul, E. A., author; Sosulski, F. W., author; Lin, D. M., author; Agricultural Institute of Canada, publisher
Soil moisture level was the most important factor controlling plant and grain yields while nitrogen fertilizer had the greatest influence on protein content and sedimentation value. Lower temperatures and nitrogen fertilization favored plant development at medium and high soil moisture levels but did not significantly alter the yield of plants subjected to periodic moisture stress. Temperature was the only treatment to have a consistent effect on kernel weight. However, seed yields were more closely associated with total plant weight and number of culms than kernel size. The sedimentation values of the flour, which ranged from 33.8 to 70.7 ml, were highly correlated with protein content. The wide range of sedimentation values approached the maximum range reported for very weak and very strong wheats. Within treatments receiving the same nitrogen applications, the sedimentation values and protein content were inversely related to grain yield. Variations in glutamic acid and proline content of the hydrolyzed flour proteins were positively associated with protein content and sedimentation value. Amino acids which were negatively correlated with protein content included alanine, arginine, aspartic acid, cystine, glycine, and lysine. Contrary to previous reports the lysine content varied over the complete range of protein content in the flours. The significance of these variations in amino acid composition are discussed in relation to recent studies on the fractionation of flour proteins.
Open Access
Control of the protein content of Thatcher wheat by nitrogen fertilization and moisture stress
(Colorado State University. Libraries, 1966-06) Hutcheon, W. L., author; Paul, Eldor A., author; Agricultural Institute of Canada, publisher
Experiments are reported in which it was shown that the protein content of spring wheat, grown in the growth chamber, could be effectively controlled by nitrogen supply and soil moisture stress. Protein contents above 16% were obtained only where yields were below the maximum attainable. In the protein range from 11 to 16%, it was possible to increase both protein and yields concurrently; protein contents higher than 16% were realized only where a growth factor such as moisture was below optimum for maximum yields. Moderate moisture stresses resulted in maximum efficiency of water use by the crop. High levels of nitrogen had more influence on the growth of straw than grain; the straw/grain ratio widened with increasing increments of nitrogen.
Open Access
Factors affecting the accuracy of the carbon-dating method in soil humus studies
(Colorado State University. Libraries, 1967-08) McCallum, K. J., author; Rennie, D. A., author; Paul, Eldor A., author; Campbell, C. A., author; Williams and Wilkins Co., publisher
Factors affecting the accuracy of the carbon-dating method of analysis have been discussed by several workers (1, 3, 13, 14). Since, however, these workers were interested primarily in archeological and geological applications of carbon-dating, they were most concerned with the absolute age of a sample. All "young" materials, for example fulvates, were therefore extracted and discarded before a sample was dated. In soil science it is not the absolute but the average age or mean residence time (m.r.t.) of the soil humus and soil humus components that is important. Thus the presence of younger fractions in a sample does not invalidate the results, and all organic fractions are dated. Some of the factors which might affect the accuracy of this method as applied to soil science were mentioned briefly by Paul et al. (12). This paper presents data and discusses some of these factors more fully. The factors examined are: precision of analytical techniques, isotopic fractionation, incorporation of nuclear-bomb-produced Cl4 into humus, and contamination by re-use or soil-respired CO2.
Open Access
Applicability of the carbon-dating method of analysis to soil humus studies
(Colorado State University. Libraries, 1967-09) McCallum, K. J., author; Rennie, D. A., author; Paul, Eldor A., author; Campbell, C. A., author; Williams and Wilkins Co., publisher
The organic fraction of soil is known to be composed of the soil biomass, partially decomposed plant and animal residues, and the materials commonly referred to as humic substances. Knowledge of the persistence of these fractions in soil is vital to the understanding of their contribution to soil fertility and soil genesis. Much information concerning the biochemistry of the humus materials also could be obtained through a knowledge of the mean residence times of the various organic fractions.
Open Access
Nitrate ion electrode method for soil nitrate nitrogen determination
(Colorado State University. Libraries, 1968-10) Paul, Eldor A., author; Myers, R. J. K., author; Agricultural Institute of Canada, publisher
Open Access
Spectrophotometric measurement of soil color and its relationship to moisture and organic matter
(Colorado State University. Libraries, 1968-10) Paul, E. A., author; Shields, J. A., author; Head, W. K., author; St. Arnaud, R. J., author; Agricultural Institute of Canada, publisher
The color of soil samples taken from the Ap horizons of Chernozemic and Gray Wooded (Podzolic) soils was measured spectrophotometrically at moisture levels ranging from air-dryness to field capacity. The Munsell re-notations "hue", "value" and "chroma" were related to the moisture content and the amount and nature of the soil organic matter. The addition of moisture to the Ap horizons from Chernozemic and Gray Wooded soils caused a significant decrease in value but had little effect on the hue and chroma. In Chernozemic soils the average decrease in value was 1.0 unit. This darkening in color occurred primarily in the moisture range between air-dryness and 18%. The decrease in Gray Wooded soils averaged 1.7 units and it occurred throughout the moisture range from air-dryness to 30%. The Gray Wooded soils were significantly higher in color value per unit of organic matter than were the Chernozemic soils. Differences were found in the ultraviolet reflectance spectra of these two kinds of soils and in the E4:E6 ratios of alkali extracts. The ratio of humic to fulvic acid and the amounts of 0.5 N NaOH-extractable humic acid also differed for the Gray Wooded and the Chernozemic soils.
Open Access
Plant components and soil organic matter
(Colorado State University. Libraries, 1970) Paul, Eldor A., author; Appleton Century Crofts, publisher
Large amounts of cellulose, aromatics, and proteinaceous compounds are introduced into the geochemical carbon pool as products of biological activity, or by economic and public health endeavors. Industrial wastes, pesticides, and detergents belong to the latter category. A net dry matter production of 1 kg/m2, representing about 4000 k. cal of energy, is attained in a significant portion of temperate terrestrial ecosystems (MacFayden, 1967). Most of the annual net primary productivity falls to the surface of the soil or is present as roots and is decomposed there. It is not surprising, therefore, that nearly every naturally produced organic compound can be isolated from the soil in at least small concentrations. The ability of multicellular plants and animals to cleave the aromatic ring appears to be restricted, most phenolics merely being modified by these organisms which do not seem to contribute substantially to the cyclization of aromatic carbon. Microorganisms, alone and in association with the soil fauna, bear the burden of releasing this carbon. Soil, being the major geostation in the cycling of terrestrial elements, is the site of greatest activity (Towers, 1964; Odum et al., 1967).Plant and animal residues with an adequate content of nutrients and a fairly low lignin content are rapidly degraded. The rate of decomposition is dependent on the moisture content, aeration, and temperature of the soil. It is only under conditions such as anaerobiosis, peat formation, or the initial colonization of a denuded landscape that plant carbon accumulates faster than it is decomposed (Ghilarov, 1967). In other environments, decomposition more or less balances the primary productivity of the higher plants and algae (Delwiche, 1965; Kononova, 1966; Burges, 1967). The contribution of plant residues and soil humus to plant growth, soil productivity, and genesis is well recognized (Russell, 1961; Tisdale and Nelson, 1966). Energy flow through producers, consumers, and decomposers is being stressed in ecosystem research (ICSU, 1967). This, plus the questions concerning the geocycle of nutrients in nature (Delwiche, 1965) and the detoxification of environmental pollutants (Breth and Stelly, 1966), makes it imperative that information be obtained relative to the turnover rate of plant constituents, and the recalcitrant humic components in soil. In this review, no attempt has been made to cover the extensive organic matter literature. The characterization of plant and soil components relative to their turnover in nature has been stressed.
Open Access
Effect of soil moisture stress on uptake and recovery of tagged nitrogen by wheat
(Colorado State University. Libraries, 1971-02) Paul, E. A., author; Myers, R. J. K., author; Agricultural Institute of Canada, publisher
Labelled 15NH4NO3 was used in a growth chamber to study the effect of moisture stress on the utilization of nitrogen by wheat. This made it possible to determine the recovery of nitrogen (N) in the soil-plant system of two Chernozemic soils. Moisture stress effects were less evident in a clay soil than in a loam. Approximately 55% of the N utilized by the growing plants came from organic soil-N mineralized during the growing period. From 59 to 71% of the initial fertilizer plus soil mineral-N was utilized by the plants. Twenty to 36% remained in the soil, and 1 to 17% was lost. Losses were greatest in soils exposed to high moisture stress and were related to the residual NO3-N levels in the soil. They were attributed to denitrification. Immobilization of N was highest at low moisture stress where plant growth was the greatest, but mineralization was unaffected by the moisture stress applied. It was estimated that 5.0 to 6.2 kg N were required to produce 100 kg of wheat, the highest efficiency of N utilization being obtained at low soil moisture stress.
Open Access
Decomposition of 14C-labelled plant material under field conditions
(Colorado State University. Libraries, 1973-08) Paul, E. A., author; Shields, J. A., author; Agricultural Institute of Canada, publisher
Mature, uniformly labelled (14C, 15N), chopped, wheat straw incorporated in the plow layer of a Brown Chernozemic soil and a Gray Wooded soil was allowed to decompose in the field. Labelled grass material (14C) was added to the surface of an adjacent virgin Brown Chernozemic soil. After 4 yr of normal cropping practices, one-fifth of the C of added straw remained in the Brown soil and one-sixth in the Gray Wooded. The initial decomposition rate of straw was retarded in plots under wheat as compared with those under fallow. Decomposition of labelled grass was initially dependent on sufficient rainfall to compress it to the soil surface. When winter periods are excluded from the time scale, the half-life of resistant straw components or soil organic matter derived from the straw was equivalent to 24 mo in Gray Wooded soil and 48 mo in Brown soil. Resistant grass material decomposed more slowly with a half-life of 96 growing mo. Distribution of labelled C among the various fractions of soil organic matter after different periods of time was investigated. The rapid decline of labelled straw from the fraction that floated in water, the high specific activity of fulvic acid, coupled with fluctuations in humic acid and the fraction <0.04 μ suggested a higher degree of biological activity in the Gray Wooded soil. In the Brown soil, the major transfer of labelled C was from the floated fraction to the humin (>0.2 μ) suggesting that the rate of decomposition was controlled to a greater extent by abiotic factors.
Open Access
The use of radiocarbon dating of organic matter in the study of soil genesis
(Colorado State University. Libraries, 1974-05) Paul, Eldor A., author; Martel, Y. A., author; Soil Science Society of America, publisher
Radiocarbon dating was used to study the nature and the stability of the organic matter in a range of Chernozemic soils (Borolls) from Saskatchewan. Two catenas, one cultivated, the other not, were studied in detail; the bottom soils of the uncultivated catena contained buried horizons. From the crest of the knoll to the depression, the mean residence time of the surface horizon of the cultivated catena decreased from 545 years before present (B.P.) to modern, the organic matter content increased and the percentage of hydrolyzable carbon decreased. The content of organic matter decreased but the mean residence time increased by 700 to 4,000 years in the B horizons. Two buried horizons located at different depths underneath the lower members of the uncultivated catena showed mean residence times of 5,950 and 8,410 years B.P. indicating that mass movement of soil had periodically occurred since the last glaciation. The 14C content of a field soil, measured by radiocarbon dating, was compared with the 14C distribution in fractions of another sample of the same soil after amendment with 14C-acetate and 350 days incubation in the laboratory. The artificially labelled soil accumulated more of the tracer in the acid hydrolyzable fractions than was found by radiocarbon dating the field soil. In turn, the distribution of soil nitrogen was more closely associated with the 14C than with the unlabelled carbon of the soil.