bluuebunny/crossref_metadata_2025 huggingface dataset:
National ecosystem assessments supported by scientific and local knowledge
Authors: Herrick Jeffrey E , Lessard Veronica C , Spaeth Kenneth E , Shaver Patrick L , Dayton Robert S , Pyke David A , Jolley Leonard , Goebel J Jeffery
Published: July 2010

An understanding of the extent of land degradation and recovery is necessary to guide land‐use policy and management, yet currently available land‐quality assessments are widely known to be inadequate. Here, we present the results of the first statistically based application of a new approach to national assessments that integrates scientific and local knowledge. Qualitative observations completed at over 10 000 plots in the United States showed that while soil degradation remains an issue, loss of biotic integrity is more widespread. Quantitative soil and vegetation data collected at the same locations support the assessments and serve as a baseline for monitoring the effectiveness of policy and management initiatives, including responses to climate change. These results provide the information necessary to support strategic decisions by land managers and policy makers.
Weathering Sequence of Clay‐size Minerals in Soils and Sediments
Authors: Jackson M. L. , Hseung Y. , Corey R. B. , Evans E. J. , Heuvel R. C. Vanden
Published: July 2010

Studies were made of several clays of soils and other deposits to clarify the nature of weathering of layer silicates. Data obtained by X‐ray diffraction, thermal, R(OH)n sorption, and elemental analyses lead to the proposal of general occurrence of interstratified X‐amorphous zones in 2:1 layer silicates. As weathering of true micas proceeds through illite, intermediates, vermiculite, and montmorin, a given K interlayer is rapidly depleted of K along a preferential weathering plane, leading to some degree of expansion. Concurrent hydroxylation by H+ addition to the octohedral layer together with dealumination accounts for loss of some of the mica layer charge. Increasing proportions of such weathered planes leads to various combinations of X‐amorphous and X‐crystalline zones typical of illite, vermiculite, and montmorin found in soils and other deposits, accounting for their diffraction properties; internal surface; K, H2O, and OH contents; and exchange properties. Functional continuity of mineral weathering in Great Soil Groups of China through layer silicates (including kaolinite), gibbsite, hematite, and anatase is demonstrated.
Root Channels and Roots in Forest Soils
Authors: Gaiser R. N.
Published: July 2010

The frequency, size, and stages in the development of vertical channels formed in the soil through the decay of the roots of hardwood trees are reported for a site located in southeastern Ohio. Data were obtained by exposing the soil profile by trenching. A diagram was prepared showing the location of root channels and living roots. Additional data on channels were obtained by probing the soil with a flexible wand to locate regions of low resistance which indicated the presence of vertical root channels. The vertical channels found exceeded 4,000 per acre. The estimate is low because not all channels could be discovered by the means employed. It is likely that vertical channels are interconnected by lateral channels formed by decayed root systems. Because channels contain materials relatively more permeable to water than the surrounding soil horizons, it is probable than the channels serve as pathways for the rapid movement of a large part of the free water in the soil profile.
Characteristics of Some Podzolic, Brown Forest, and Chernozem Soils of the Northern Portion of the Lake States
Authors: Nygard Iver J. , McMiller P. R. , Hole Francis D.
Published: July 2010

The morphology of the six great soil groups — Chernozem, Degraded Chernozem, Gray Wooded, Brown Forest, Brown Podzolic, and Podzol — with laboratory data is presented.

The general distribution of these soils is shown on a schematic map. Of the five soil forming factors, three — climate, living matter, and parent materials — change notably from west to east. The other factors, topography, and age, are reasonably uniform in the areas selected for the modal soil profiles. Additional maps, illustrations of soil profiles, and related landscapes accompany the acticle. Tables of profile characteristics and laboratory analyses are arranged to show a summarized comparison of the various soil horizons of each soil.
Microclimate and Water Vapor Exchange at the Soil Surface
Authors: Brawand Hans , Kohnke Helmut
Published: July 2010

Estimates were obtained on the annual water vapor exchange through adsorption, condensation, and evaporation at the ground surface under field conditions. The investigation was coordinated with measurements of environmental microclimatic conditions. For a 2‐month period data were obtained also on nocturnal water accretions on corn and soybean leaves.

A small area of land on the Purdue University dairy farm near West Lafayette, Ind., was chosen as site for the field experiments. Five sampling conditions were employed, in which 20 small metal dishes served as containers for various soil and water samples. Each sampling set consisted of four filled dishes, two of the dishes to be placed on the ground surface of bare soil and the other two on meadow, during experimental periods.

The annual moisture gains from adsorption and condensation of atmospheric water vapor are estimated at 1.22 inches for bare soil, and 0.99 inch for soil having grass‐clover vegetation. The water vapor transfer from the subsoil to the soil surface, not including evaporational losses, attained 1.34 inches of water on bare ground and 0.77 inch on meadow. This results in total moisture gains of 2.56 inches and 1.76 inches, respectively. The field tests indicated that 0.59 inch of water per month per acre of ground collected on corn leaves in summer. Similarly, soybeans yielded 1.32 inches in the same period. This accumulated moisture on the plant leaves in clear nights consists of condensational water from the atmosphere and of guttation.

Water vapor transfer from the subsoil toward the top layer normally remains confined to night hours during the period from March to October. Under the same conditions, a two‐directional moisture loss from the ground surface layer takes place in the daytime: a part of the moisture can be driven to greater soil depths, while perhaps a larger part is subject to evaporation. Water vapor transfer from the subsoil to the surface may be a continuous process in winter, unless the soil is water saturated.
The Influence of Applied Boron, Magnesium, and Potassium on the Growth and Chemical Composition of Red Clover Grown under Greenhouse Conditions
Authors: Tucker T. C. , Smith F. W.
Published: July 2010

The objective of this investigation was to determine by means of greenhouse experiment the influence of application of boron, magnesium, and potassium on the yield and chemical composition of red clover grown on Kansas soils.

A factoral design of greenhouse experiment in which a single rate of application of boron, magnesium, and potassium was made to each of four soil materials was used for the growth of red clover. Yield data were collected for four clippings of plant material. Chemical analyses were made for phosphorus, potassium, magnesium, and boron.

Applications of potassium to the soil always increased the potassium content of the red clover plants and significantly the total yield of red clover for each soil type. Approximately 1% potassium in the plant material was the critical lower limit for this element, insofar as growth response was concerned.

Boron applications increased the boron content of the plant material regularly and considerably. A critical lower limit of about 28 to 30 ppm B in red clover plant material was established as being necessary for prevention of boron deficiency. Cherokee subsoil was more deficient in boron than any of the surface soil samples used in this study.

Magnesium applications to the soil were generally effective in increasing magnesium concentrations in the plant material only when potassium was not included as a part of the chemical treatment. A critical lower limit of about 0.5% magnesium in red clover plant material was required for optimum growth.

A definite positive correlation was established between percent phosphorus and percent magnesium in the plant material. The mean value was 0.535. This correlation was most marked on soils which had low magnesium activity as indicated by relatively low percentage magnesium saturation on the exchange complex.

A definite negative correlation between percentage composition of potassium and percentage composition magnesium was established. The mean value was 0.683. Potassium was shown to exert control over magnesium and not vice versa.
Influence of Double‐cut Plow Mulch Tillage on Number and Activity of Microorganisms
Authors: Gamble S. J. R. , Edminster T. W. , Orcutt Fred S.
Published: July 2010

A decreased availability of plant food throughout the growing season has been observed for some stubble mulch practices. To determine if the microflora were involved as a possible factor in this plant food availability difference, comparative data were obtained from double‐cut and turnplow soil samples. Under the conditions of this investigation the following microbiological factors may be related to the plant food tie‐up problems: (a) The environmental conditions of better oxygen supply and more organic matter in the 0–6 inch horizon seem to favor the stimulation of the soil fungi in the mulch plots. This group of soil microorganisms might cause a temporary loss of nitrate‐nitrogen as a result of protein synthesis by the mold cells. (b) Biochemical nitrification as determined with the perfusion apparatus of Lees and Quastel showed slightly lower amounts of nitrate‐nitrogen formed from the mulch than from the turnplow samples. In addition, the soil pH should be considered as an environmental factor which may have considerable influence on the activity of the soil population. It is believed that these factors might be temporarily involved in the plant food tieup problems found to be associated with stubble mulch tillage practices at Virginia Polytechnic Institute.
Effect of Different Sources and Rates of Application of Fertilizer Materials on the pH and N, P, K, and Mg Content of the Soil to Which They Were Applied
Authors: Vittum M. T. , Lathwell D. J. , Stanford G.
Published: July 2010

A fertilizer experiment comparing the effects of different sources of N, P, and K, and different rates of application of complete fertilizer on the yield of beets, cabbage, peas, sweet corn, and tomatoes was conducted on a soil which, for the preceding 20 years, had been fertilized according to good commercial practice with a “complete” fertilizer high in phosphorus. After 5 years of consecutive application of the differential treatments, soil analyses showed the following results: (1) No significant difference in soil pH, ammonium N, nitrate N, P, K, or Mg from inorganic sources of N versus 40% of organic N; ordinary superphosphate versus “double” superphosphate; or muriate of potash versus 50% of the potash in the form of sulfate of potashmagnesia; (2) Significant decrease in pH and Mg and significant increase in nitrate N, P, and K with increasing rates of application of complete fertilizer; (3) No interaction between sources of fertilizer nutrients and rates of application; and (4) After 5 years of intensive vegetable cropping without addition of any fertilizer, available P, K, and Mg in the soil were 28, 86, and 557 pounds per acre, respectively. According to present New York standards, these values are classified as “very high,” “medium,” and “very high,” respectively.
The Effect of the Addition of Organic Materials on the Decomposition of an Organic Soil
Authors: Bingeman C. W. , Varner J. E. , Martin W. P.
Published: July 2010

Glucose, alfalfa insolubles, and complete alfalfa uniformly labeled with carbon‐14 were added to an organic soil to determine under controlled conditions, if the loss of the soil due to biological decomposition could be counteracted. Carbon‐14 labeled material was used so that it could be determined whether or not there was an increase in the decomposition of the native organic matter as a result of the added material, and, if this was true, whether the soluble fraction of the added materials, or the insoluble fraction, was chiefly responsible.

The materials were added, the soil incubated, and CO2 collected at intervals. The insoluble fraction of alfalfa caused a larger breakdown of native organic matter than solubles alone or complete alfalfa. It was impossible to build up the organic content of the soil, under these conditions, but the net loss of carbon was diminished by the addition of the organic materials.
Influence of Alfalfa Green Manure on the Availability of Phosphorus to Corn
Authors: Nielsen K. F. , Pratt P. F. , Martin W. P.
Published: July 2010

Greenhouse work was conducted in which alfalfa and KH2PO4, singly and in combination, were used as phosphate fertilizers. These materials were layered into pots of Wooster silt loam representing three levels of residual phosphorus. The availability to corn of the phosphorus in these carriers of phosphorus and in the soil was measured by the use of radiotracer techniques. A series of Neubauer tests were carried out to determine the time rate of release of phosphorus from alfalfa.

Results indicate that the phosphorus in the alfalfa was not as available as in the KH2PO4. However, the alfalfa increased the availability of the residual phosphorus. The Neubauer tests indicated that the phosphorus from the alfalfa was most available during the period between 46 and 64 days after being incorporated into these soils.
Cationic Activities in Systems of Plant Roots
Authors: McLean E. O. , Baker F. E.
Published: July 2010

The activities and mean free bonding energies of Na, K, and Ca on alfalfa, soybean, red top, and Reed canary grass roots were determined by the use of the clay membrane electrode technique. Samples of electrodialyzed roots were saturated with each cation by addition as the hydroxide after the exchange capacity of the roots had been previously determined.

Examination of the techniques employed showed that reproducible determinations of the activities could be made after a five minute contact of the clay membrane electrode with the root system. Identical readings from both small and large electrodes indicated that there was no problem in obtaining a representative cross section of the root systems for measurement. There was no appreciable liquid junction potential at the point of contact of KCl bridge with the root system. The cations added were found to be practically all recoverable in a 0.1N HCl extraction without serious contamination from ions within the roots.

It was possible to determine a value for the cation exchange capacity of the roots by titrating the electrodialyzed roots with base, stirring, and maintaining the system at pH 7 for ten minutes. Bonding energy determinations on these systems indicate that K is bonded stronger than Na on alfalfa roots, but Na is bonded stronger than K on soybean roots. The legume roots held all of the cations with greater energy than did those of the grasses; however, there was a shift in the relative values obtained for the grass root systems when compared to those of the legumes.
Soil Structural Stability of Brookston Clay as a Factor in Sugar Beet Yields
Authors: Zwerman Paul J. , Page J. B. , Yoder R. E.
Published: July 2010

The purpose of this research was to determine the influence of the structural stability of soil upon the yield of sugar beets.

Structural units of soil between one‐eighth inch and one‐fourth inch were used in 20 small plots. The main comparison made was of highly stable structure (12% organic matter) against highly unstable structure (5% organic matter). The top soil (10 inches) of each of 10 of these plots was made up of stable soil structure. The other 10 plots were made up of unstable structure. Five rainfall conditions were studied: frequent half‐inch, no rain, natural rain for 1947, 4 inches per week, and rain similar to 1942. There were 16 harvested beets on each plot or 64 per rainfall condition. Film‐glass cloth houses used to protect the soil from natural rainfall transmitted only one‐half of the sunlight. Apparently this light factor was responsible for the highest beet yield under natural rain and sunlight.

There were no differences in yield associated with soil structural differences except in the case of 4 inches rain per week. This difference was significant. Differences in yield as affected by rainfall were significant for all comparisons except “ideal” rain and 1942 rain.
X‐Ray Characteristics of Clay Minerals as Related to Potassium Fixation
Authors: Kunze G. W. , Jeffries C. D.
Published: July 2010

Evidence is presented to support on structural grounds the early potassium fixation theories based on entrapment of the potassium ion due to the closure of the interlayer spaces. Field surface samples (0–6 in.) of 15 soils classified as Gray‐Brown Podzolics from which the clay was extracted served as experimental material. The soil‐clays were saturated with potassium and a divalent cation and the effect on the basal spacings noted. X‐ray diffraction results suggested that those soil‐clays which showed a strong 10 angstrom line when potassium saturated as contrasted to a strong 14 angstrom line when saturated with a divalent cation were relatively high fixers of potassium. Those soil‐clays which showed little or no shifting of the larger basal spacings toward 10 angstroms when saturated with potassium were found to be relatively low fixers of potassium.
Nitrogen, Phosphorus, and Potassium Content of the Corn Leaf and Grain as Related to Nitrogen Fertilization and Yield
Authors: Bennett William F. , Stanford George , Dumenil Lloyd
Published: July 2010

On a series of eight nitrogen side‐dressing experiments in 1950, a study was conducted to determine the effectiveness of side‐dressed nitrogen on corn as shown by yield response and by the chemical composition of the corn leaf and grain. A wide range in response to nitrogen occurred. The application of nitrogen significantly increased the percent of nitrogen in the leaf on all experiments, whereas, the nitrogen content of the grain was significantly increased on only five of the eight experiments. Phosphorus percentage in the leaf was significantly increased due to nitrogen application on certain experiments; and these increases were associated with yield responses which proved to be independent of the nitrogen effect. That a definite relationship between yield and the nitrogen and phosphorus content of the leaf existed in these experiments was shown by determining the regression of yield on the content of these nutrients. Both of the regression coefficients were significant and the multiple correlation coefficient was highly significant. When the nitrogen percentage in the leaf reached the level of approximately 2.8 or above, further increases did not appear to affect corn yields. A very striking linear relationship was found to exist between increases in yield resulting from nitrogen fertilization and associated increases in the nitrogen content of the leaf, the correlation coefficient being 0.96. The results of plant analysis suggest that phosphorus deficiency was a factor limiting yields on four of the experiments. Chemical soil tests for available phosphorus did not distinguish between five of the experiments which, however, appeared to differ in phosphorus status on the basis of phosphorus content of the leaf. In these experiments, leaf analysis provided a clearer indication of the nutrient status of the plants than did grain analysis for all three nutrients.
Nine Essential Amino Acids in the Protein of Wheat and Barley Grown on Sulfur‐Deficient Soil
Authors: Renner Ruth , Bentley C. F. , McElroy L. W.
Published: July 2010

The investigation was undertaken to study the possible effects of fertilizers and cropping systems on the quality of grain protein as measured by total content and proportions of nine essential amino acids. Amino acid determinations were made on acid hydrolysates of ground grain using a microbiological assay method.

All grains were grown on sulfur‐deficient gray wooded soil. Most of the samples were from plots originally laid out in 1930 for long term tests to compare the effects on crop yields of various fertilizers applied in a wheat‐fallow cropping system and in a rotation in which mixed legume hay was grown in two years out of five.

The protein content of wheat grown in the rotation was higher than that of wheat from the wheat‐fallow plots and the barley grown the first year after legumes contained more protein than that grown the third year after legumes. Increases in percentage of protein (N × 6.25) in the grains were associated with some decrease in quality as measured by the percentage that nine essential amino acids contributed to the protein. This decrease in quality was less marked in grains from rotation plots to which fertilizers containing sulfur were applied than in those from plots treated with fertilizers that did not supply sulfur.
The Behavior of Applied Phosphorus and Potassium in Organic Soil as Indicated by Soil Tests and the Relationship between Soil Tests, Green‐Tissue Tests and Crop Yields
Authors: Bigger T. C. , Davis J. F. , Lawton Kirk
Published: July 2010

Phosphorus and potassium were extracted from organic soils by rapid test methods using 0.1 N HCl — 0.03N NH4F, 0.135 N HCl, and 0.018 N CH3COOH for phosphorus and 23% NaNOa, 0.135 N HCl, and 0.018 N CH3COOH for potassium. The extractable phosphorus was determined by a colorimetric method and the extractable potassium was determined with a flame photometer, except for the sodium nitrate extracts in which case a cobaltinitrite procedure was employed.

A highly significant correlation exists between the amount of phosphorus and potash applied and the amount of phosphorus and potassium extracted from the soil. Applied phosphorus remained in the surface soil while potassium was found in the 12 to 18‐inch depth.

Periodic green‐tissue tests of sugar beets and peppermint revealed a seasonal variation in the composition of water extractable phosphorus and potassium in these plants. Sugar beets contained 1,800 ppm and peppermint 1,000 ppm of potassium when the plants showed foliar symptoms of potassium deficiency.

In correlating rapid soil tests, green‐tissue tests, and crop yields, it was impossible to establish optimum levels of phosphorus and potassium for maximum yields of sugar beets and peppermint because of the following factors: the physiological nature of the plants, the seasonal variations in plant composition, the differential response of the crops to the fertilizer ratios, and the limitation of the fertilizer analyses and rates of application in this experiment.
Recording Soil Moisture Automatically
Authors: Korty B. L. , Kohnke H.
Published: July 2010

A method utilizing nylon blocks and an automatic recording potentiometer equipped to record resistence by means of a special ohmmeter circuit was used to follow continuously the moisture content of the soil. The information obtained was used in correlation with rainfall data to estimate the time required for water to reach various depths in the soil.

The results show that water moved downward more rapidly on a watershed where conservation practices were used than on a prevailing farm practice watershed.

An automatic instrument of the type used in this work that follows soil moisture conditions would be of great value in many research problems.
A Method for Determining the Stability of Soil Structure Based Upon Air and Water Permeability Measurements
Authors: Reeve R. C.
Published: July 2010

A method is described for determining the stability of soil structure based upon intrinsic permeability, the measurement being made first with air, and then with water. The change in permeability is attributable to the instability of the soil to the wetting and slaking action of the water.

Procedures and equipment for making tests with fragmented samples are described. Experimental data which show that the permeability ratio, air to water, is correlated with treatments known to produce differences in structural stability, are presented for both fragmented samples and soil cores. The air‐water permeability ratio is shown to be correlated with both the exchangeable‐sodium‐percentage and clay content of soils. The effect of a polymeric soil conditioner of the type VAMA (Vinyl acetate‐maleic acid) in stabilizing the structure of alkali soils, is reflected in the permeability ratio determination.

The permeability ratio for soils varies over a range of from slightly greater than 1 to 10,000 or more. This large range permits effective appraisal of soil treatments that affect soil stability.

On the basis of the reported tests, it appears that at the 20 to 1 level of odds, single determinations of the permeability ratio will distinguish a 45% difference for fragmented samples and a 185% difference for cores.

The permeability ratio expresses in a single dimensionless number the effects of many factors and processes that influence the stability of soil structure. It is an integrated measure of the effects of swelling, slaking, dispersion, and other processes that take place to change soil structure as a result of wetting with water.
Mica Weathering Sequence in the Highfield and Chester Soil Profiles
Authors: Jeffries C. D. , Rolfe B. N. , Kunze G. W.
Published: July 2010

The paper consists of the description of a procedure for determining the nature of the micas in soils and the application of this procedure to the study of the weathering characteristics of the micas in the Highfield soil profile from Pennsylvania and the Chester soil profile from Virginia. The results of this study indicate a definite type of weathering sequence of the micas, which consists of mica — mica intermediate, to hydrated mica to chlorite — kaolin.
The Feeding Power of Plants for Phosphates
Authors: Fried Maurice
Published: July 2010

Plant species were compared as to their feeding power for both monocalcium phosphate and rock phosphate. Even after the effect of size and extensiveness of the root absorbing surface was eliminated, species differed in their capacity to absorb phosphorus from basic calcium phosphates. The phosphorus of rock phosphate was most available to buckwheat and was more available to the legumes, alfalfa, crotalaria, and ladino clover, than to the grasses, orchard grass, bromegrass, perennial ryegrass, millet and oats.
Iron Oxide Removal from Soils and Clays
Authors: Aguilera N. H. , Jackson M. L.
Published: July 2010

Iron oxide coatings or crystals must be removed from soils in which they are found in many mineralogical techniques for identification of colloidal layer silicates as well as the identification of silt and sand grains with the polarizing microscope. A procedure is presented which employs sodium dithionite (Na2S2O4, hyposulfite, or “hydrosulfite”) as the reductor, and 0.3 molar citrate with or without Fe‐3 specific Versene as the chelating reagent. It is a neutral system the pH of which is kept at 7.3. The reaction is fast, as much as 20% of iron oxides (hematite, geothite, or limonite but not magnetite or ilmenite) being removed from a soil in 15 minutes, and does not precipitate either elemental sulfur or iron sulfides. Like other procedures, it causes some decrease of exchange capacity of layer silicates which contain iron, and at the same time may increase the exchange capacity of kaolinic soils.
Influence of Rate of Plant Residue Addition in Accelerating the Decomposition of Soil Organic Matter
Authors: Hallam M. J. , Bartholomew W. V.
Published: July 2010

The addition of corn and soybean residues to soils increased the rate of decomposition of the native soil organic matter. The residues were comparable to green manure crops and the data provide an explanation for the failure of green manures to be helpful in building or maintaining the organic matter content of soils.

Plant materials containing radioactive carbon were added to soils at the rates of 2.5, 10 and 50 tons per acre. The use of the isotopes permitted a partition of the evolved CO2 into that coming from the plant residue and that coming from the soil organic matter.

The high rates of residue addition resulted in greater losses of native soil organic matter than did the low rate. Corn and soybeans were similar in their influence on the decomposition of soil carbon.

The rate of plant residue addition had a marked influence upon the rate of residue decomposition. At the rate of 2.5 and 10 tons per acre the decomposition of residue was considerably more rapid than when added to soil at the rate of 50 tons per acre. Residues apart from soil decomposed at about the same rate as when added to soil at the rate of 50 tons per acre.
Characteristics of Certain Soils in the Dominican Republic
Authors: Veale P. T.
Published: July 2010

This study summarizes the first soil survey on sugar estates in the Dominican Republic. The soils are characterized and classified. Illustrations of soil profiles, and diagrams showing their topographic occurrence are included. A rather close relationship was found between soil characteristics and root growth of cane. Study of root growth in relation to soil properties was helpful in evaluating the agriculture potentialities of the various soils.
A Basis for Improving the Soil Classification in the Seaward Portion of the Atlantic Coastal Plain
Authors: Ligon W. S. , Lyford W. H.
Published: July 2010

Field studies and historical reviews of some 47 soil series in the seaward portion of the northern Atlantic Coastal Plain led to the use of five general principles in improving the soil classification in that particular area:

The older, widely known soil series names shall be given preference over newer ones whenever feasible.

Soil series shall not be differentiated on the basis of marine terrace height (or age) per se.

Range in subsoil texture of each series shall be consistent and of reasonable magnitude.

Each drainage sequence shall consist of soil series reasonably comparable in subsoil texture.

Differences in substratum texture that constitute the sole differentiating feature between soils shall be considered as phase differentia rather than series differentia.

Each of these principles is discussed with reference to problems of soil classification in the area and a partial key showing drainage and subsoil texture relationships among 30 of the soil series is given.
Correlation of Phosphorus Content of Alfalfa with pH and Forms of Soil Phosphorus
Authors: Hallock D. L. , Attoe O. J.
Published: July 2010

A study was made of the availability to alfalfa of acid soluble and alkali soluble inorganic and organic soil phosphorus. Samples of both soil and alfalfa were taken from experimental plots and farm fields located on eight soil types.

In the case of the plot samples, it was found that the content of acid soluble soil phosphorus in 1948 and soil pH in 1949 were the variables most closely related to the phosphorus content of the alfalfa. Out of 22 cases of significant correlations of the phosphorus, 2 were with soil pH, 8 each with the acid soluble and alkali soluble inorganic forms and 4 with the alkali soluble organic form.

When the silt loam soils were divided into two pH groups, those below 7.0 and those of 7.0 and above, the contents of acid soluble and alkali soluble inorganic phosphorus were the forms most closely (and about equally) correlated with the phosphorus content of the alfalfa for both groups.
A Comparison of the Effects of Exchangeable Sodium and Potassium upon the Physical Condition of Soils
Authors: Reeve R. C. , Bower C. A. , Brooks R. H. , Gschwend F. B.
Published: July 2010

The effects of exchangeable sodium and of exchangeable potassium upon soil physical condition were compared by means of permeability ratio, air to water, and modulus of rupture determinations. The permeability ratio is a measure of the change in pore‐size distribution due to the action of water and the modulus of rupture is a measure of soil crusting. The permeability ratio and modulus of rupture increased markedly with increasing exchangeable‐sodium‐percentage, whereas, increases in the exchangeable‐potassium‐percentage had little effect. The relation of the permeability ratio to exchangeable‐sodium‐percentage can be expressed by an exponential equation of the form, y = aebx, whereas, the modulus of rupture is linearly related to exchangeable‐sodium‐percentage by the equation y' = mx + c. The parameters a, b, m and c of the respective equations are positively correlated with cation exchange capacity and total specific surface.
Sand‐Model Experiments on the Distribution of Water‐Pressure under an Unlined Canal
Authors: Day Paul R. , Luthin James N.
Published: July 2010

A study has been made of the seepage of water by capillary flow (movement at pressures less than that of the atmosphere). The analysis differs markedly from previous theories of seepage which ignore capillary movement.

An idealized flow system, which consisted of parallel furrows in soil overlying a gravel substratum, was postulated in the theory and simulated experimentally in a sand model. Pressures were measured tensiometrically. The water pressure found at various points in the sand model in the steady state agreed approximately with values calculated from theory.

The theory is applicable only to certain simple cases. However, the results show clearly that under certain conditions capillary flow accounts for the entire seepage flux. In such cases, the reduced pressure of the water prevents its entry into test holes placed in the seepage zone.
A Study of Adaptation in Azotobacter
Authors: Harris John O.
Published: July 2010

The age of cells was shown to be an important factor in the rate at which Azotobacter chroococcum adapts its respiratory mechanism to the utilization of different substrates. These organisms are able to utilize dilute (M/400) solutions of glucose or mannitol for respiration. Experiments measuring oxygen uptake and dehydrogenase activity of intact cells indicated that simultaneous oxidation of two substrates is possible by partially adapted cells. Studies of enzymatically active cell‐free extracts showed that the Kreb's cycle of terminal oxidation probably occurs in Azotobacter chroococcum. Glucose and mannitol dehydrogenases appeared to be formed only when these compounds were present. This was interpreted as evidence that at least part of the adaptation process is due to formation of new enzyme systems.
Modification in Chemical Properties of Straw during Decomposition
Authors: Broadbent F. E.
Published: July 2010

Oat straw samples were allowed to decompose for periods varying up to 15 months; changes in functional groups and chemical properties followed as a function of time. Carbon increased in the whole residues and decreased in the lignin fraction while hydrogen decreased in both. Selective demethylation occurred in the lignin but methoxyl content of the complete residues remained about constant. Carboxyl groups as determined by esterification increased progressively, accompanied by decreases in hydroxyl. Carboxyl in the lignin fraction was in good agreement with exchangeable hydrogen determined by an iodometric titration procedure in contrast to lack of agreement between corresponding values in the whole residues. Cation exchange capacity of the straw residues and of their lignin component increased as decomposition progressed.

Absorption of oxygen by alkaline suspensions of the residues was determined in a Warburg respirometer and found to increase with length of decomposition period. Most of the total oxygen uptake during an arbitrary 8‐hour period could be attributed to the lignin fraction.

Some chemical properties of organic matter preparations from five soils were compared with corresponding values for the decomposed residues.
The Adsorption and Reactions of Enzymes and Proteins on Kaolinite. II
Authors: McLaren A. Douglas
Published: July 2010

Some preliminary data illustrating the role of adsorption of enzymes and proteins to kaolinite in enzyme‐substrate reactions are presented. The adsorption of trypsin and chymotrypsin on kaolinite is nearly complete within 2–3 minutes. Over 40 mg. of chymotrypsin (MW 27,000) is adsorbed per gram of kaolinite whereas only 28 mg. of lysozyme (MW 15,000) is adsorbed. Much less chymotrypsin is adsorbed on kaolinite previously nearly covered by lysozyme. Heat‐inactivated lysozyme either in solution or adsorbed on kaolinite is subject to hydrolysis by chymotrypsin. The rate of hydrolysis is slower in the adsorbed state, however. Adsorbed trypsin is slowly hydrolyzed by free trypsin in a suspension of kaolinite. Thus substrates adsorbed on kaolinite are subject to hydrolysis by enzymes in solution. Lysozyme and trypsin eluted from kaolinite with ethylamine are active as enzymes. The possible significance of such findings for an understanding of the microbial utilization of macromolecules in the presence of clay minerals is discussed.
The Origin of Mima Mound (Hogwallow) Microrelief in the Far Western States
Authors: Arkley Rodney J. , Brown Herrick C.
Published: July 2010

The origin of the mound microrelief known by such names as “hogwallows,” “pimple mounds” or “mima mounds” has long been a mystery; although many solutions have been proposed, none has yet received widespread acceptance.

During the course of the soil surveys of eastern Merced and Stanislaus Counties of California, where mound microrelief is widespread, the phenomenon was studied over a period of eight years. All known theories were evaluated and compared with the evidence which could be observed in the field. The evidence includes the nature of the mounds such as shape, size, internal structure, distribution of gravel, the burrows of ants and rodents; the distribution of the microrelief with respect to soil types and the pattern of occurrence of mounds under various conditions.

The theories of origin which were tested included erosional theories based on wind action and water action, fluviatile, submarine and sub‐lacustrine currents; eruptional theories suggesting gas‐vents, sand boils and hydrostatic pressure; and biological theories based upon the activity of ants, ground squirrels and pocket gophers.

It is concluded that the evidence points clearly to a biological explanation, and that the pocket gopher is responsible for Mima mound microrelief.
The Regur Soils of India and Their Utilization
Authors: Simonson Roy W.
Published: July 2010

The Regur or Black Cotton soils of India seem to be members of the same great soil group as the Houston Black and Houston series of Texas, on the basis of field studies by the author in the Deccan plateau in 1951. Similarities between the soils on the separate continents are evident in morphology, contents of organic matter, clay minerals, carbonate content and distribution, and the high coefficients of expansion and contraction upon wetting and drying. Like Houston Black clay, the Regur soils are widely used for cotton, although much greater acreages of the soils, with a total area equal to that of the Corn Belt, are devoted to sorghum, pearl millet, pulses, and other food crops. Agricultural production is largely dependent upon animal power and human labor, with little benefit from products of heavy industry such as tractors, fertilizers, insecticides, and the like. Yield levels for most crops are low as compared to those in the United States, although yields have been stable at these low levels for centuries. Higher levels of production will require substantial changes in the agicultural arts and in the technological and industrial resources available to and used by the cultivators of the Regur soils.
Rainfall Intensity as a Measure of Storm Erosivity
Authors: Ekern P. C.
Published: July 2010

The erosivity of storms should be proportional to the additive kinetic energy from the impact of falling rain and shallow flow of water. The erosivity of shallow water should be proportional to the proximity of the maximum velocity thread to the soil surface and the square of that maximum velocity. Relations among velocity, slope, and discharge suggest the following function for erosivity:

Erosivity = f [(discharge rate)1.0 (slope)1.0]

Evaluation of data suggested that the relation was reasonable, though a slightly higher value than the first power of the discharge was generally found.

When discharge in turn was related to rainfall intensity, the erosivity for shallow flow became:

Erosivity = f [(storm intensity)1.46 (slope)1.0]

The impact energy of rainfall was found to be a nearly identical function of intensity and slope so that the additive energy of shallow flow and drop impact should approximate the 1.5 power of the storm intensity.

Examination of the envelope for maximum soil loss from fallow plots of silt loam on 16% slopes at LaCrosse, Wis., showed such a relation to the 1.5 power of the rainfall intensity.
The Effect of Conservation Practices on Runoff, Available Soil Moisture and Cotton Yield
Authors: Burnett Earl , Fisher C. E.
Published: July 2010

The mechanical conservation practices of contouring and terracing have produced significant differences in runoff, available soil moisture, and cotton yield in a 26‐year experiment at Spur, Tex. The increased cotton yield may be attributed primarily to reduction or elimination of runoff with attendant deeper penetration of moisture which resulted in reduction of moisture losses by evaporation and weed growth.

Available soil moisture in the second and third feet of soil on May 20 was increased from an average of 1.27 inches on plots with rows in the direction of the slope to 1.60 inches on contoured plots with closed level terraces. The average annual runoff on the former plots was 2.75 inches and was completely eliminated on the latter. The average yields of lint cotton for the two practices were 117 and 188 pounds per acre.
Field Capacity Approximation Based on the Moisture‐Transmitting Properties of the Soil
Authors: Hanks R. J. , Holmes W. E. , Tanner C. B.
Published: July 2010

A new field capacity approximation is reported. This approximation was compared both with the field capacity and with various estimates of the field capacity of 23 soils. The field capacity approximation was found to be related to the field capacity by the equation: FC = 0.959FCA + 1.17. The data presented support the view that field capacity is the moisture content of a well drained soil when, after the soil has been thoroughly wet, drainage has decreased the moisture content to such an extent that the consequent decrease in capillary conductivity materially impedes further drainage of water. A statistical test of significance showed that the field capacity approximation is a significantly better over‐all estimate of field capacity than the moisture equivalent, buchner funnel percentage, and ⅓‐atm. percentage. The test further indicated that the field capacity approximation is not a significantly better estimate of field capacity than a modification of the Wilcox (7) method. However, the field capacity approximation is much more convenient, reproducible, and time conserving than the modified Wilcox method.
X‐Ray Diffraction of Common Silica Minerals and Possible Applications to Studies of Soil Genesis
Authors: Pollack S. S. , Whiteside E. P. , Van Varowe D. E.
Published: July 2010

A qualitative X‐ray diffraction study indicated that quartz was present in all of 16 silica minerals. Jasper was the only sample found to contain a crystalline impurity and this was identified as hematite.

A standardized sample preparation and mounting technique is described herein. Quantitative estimates of the quartz contents of three phenocrystalline varieties and two cryptocrystalline varieties of quartz were made. The cryptocrystalline varieties showed much less intense diffraction by the 3.35 A° spacing characteristic of quartz than did the phenocrystalline varieties. The available evidence indicates that these differences are probably due to fundamental differences in the nature of the quartz in these two groups. However, the possibilities of the presence of some amorphous diluents and variable particle sizes have not yet been completely eliminated.

The implications of these findings for the use of X‐ray diffraction procedures for the determination of quartz in soils and the study of soil genesis are discussed.
A Chemical‐Microbiological Study of Effects of Exchangeable Cations on Soil Aggregation
Authors: Aldrich D. G. , Martin J. P.
Published: July 2010

This paper presents data obtained in a study of the effect of various exchangeable cations on soil aggregation and microorganisms. Twenty‐one treatments involving various combinations and ratios of exchangeable Ca, Mg, Na, K, and H were compounded by appropriate treatment of a Hanford sandy loam and a Yolo sandy loam. The soil samples of varying cation composition were incubated alone and in combination with organic matter sources of high and low carbon‐nitrogen ratio for a period of 200 days. Soil aggregation measurements and counts of kind and number of soil microorganism were made at various intervals during the incubation period. In comparison with a calcium system, the following results were noted: (1) A high percentage of Mg has no effect on aggregation. (2) Depending on the soil, a high percentage of exchangeable K may or may not reduce aggregation. (3) Increasing Na reduces aggregation. (4) An excess of free lime reduces aggregation. (5) Kinds and numbers of microorganisms are affected more by organic matter additions than by cation composition of soil. (6) Organic matter additions increase aggregation regardless of cation composition.
Unsaturated Flow of Water in Field Soils and Its Effect on Soil Moisture Investigations
Authors: Robins J. S. , Pruitt W. O. , Gardner W. H.
Published: July 2010

Measureable drainage of water within the soil profile in field plots was observed for periods of up to 8 days following irrigation under an actively transpiring alfalfa crop. Rates of movement from the 0 to 3 foot zone were of the order of 0.20 inch per day 2 days after irrigation and 0.11 inch per day 4 days after irrigation. Total drainage from the 0 to 3 foot zone for the period 2 to 8 days was 0.58 inch.

This downward movement of water is shown to have material effects upon consumptive use measurements and the soil moisture extraction pattern. A computed error of 23 per cent in consumptive use for the first 8 days following irrigation is shown to have occurred in the present experiment as a result of drainage from the 0 to 3 foot zone.