Showing papers in "Soil Science Society of America Journal in 1953"

The Effect of the Addition of Organic Materials on the Decomposition of an Organic Soil

Abstract: 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.

Iron Oxide Removal from Soils and Clays1

Abstract: 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. View complete article To view this complete article, insert Disc 2 then click button8

The Nature of Phosphate Sorption by Calcium Carbonate

Abstract: Studies on the nature of phosphate sorption by calcium carbonate indicate that when soluble phosphate fertilizers are added to calcareous soils, the reactions with calcium carbonate consist of rapid monolayer sorption on CaCO₃ surfaces and, at high phosphate concentrations in the vicinity of fertilizer particles, the precipitation of dicalcium phosphate, or a compound with similar properties. The initial products of these reactions are characterized by very high specific surfaces and greater phosphorus solubility than the stable hydroxyapatite or fluorapatite. Dynamic equilibrium in calcareous soils involves all of these forms of phosphate. Some of the effects of the ionic environment on solubility of calcium phosphates were calculated and experimentally verified.

Influence of Rate of Plant Residue Addition in Accelerating the Decomposition of Soil Organic Matter1

Abstract: 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.

Field Structure of Cultivated Soils with Special Reference to Erodibility by Wind

Abstract: A study of structure and erodibility of soil by wind was carried out on wind eroded and residual soil materials in a condition usually existing in the field and after sampling, cultivating, and dry sieving. Field structure and erodibility of soils varied greatly with as little as 1 inch of simulated rainfall. In soils undisturbed by cultivation after rain, four distinct phases of structure were found, all of which possess different degrees of erodibility by wind. These phases are the primary aggregates (water-stable aggregates), the secondary aggregates (granules and clods), the surface crust, and the consolidated soil material between the secondary aggregates. The abrasive action of wind erosion was shown to be one of the most serious aspects of erodibility by wind. The mechanical stability, that is, the resistance of a soil to breakdown by mechanical forces such as cultivation or sieving, was found to vary directly with the resistance of the soil to abrasion by wind-blown sand. Mechanical stability was greatest for drift particles (sand grains and water-stable aggregates mostly), less for the secondary aggregates, followed in order by the surface crust, the consolidated materials between the secondary aggregates, and lastly the consolidated materials, if any, which held drifted particles together after they were wetted and dried. The amount of dispersed fine silt was found to be a primary factor influencing the formation of the surface crust and the consolidation of the soil body after it was wetted and dried. A fraction of clay size, being much less dispersible than silt, was found to be the primary factor of secondary aggregate formation. Water-dispersible silt and clay were responsible in large measure for the resistance of the soil to erosion by wind. Although the amount of erosion was limited to some degree by the presence of water-stable aggregates too large to be moved by wind, it was found that cultivated dryland soils lack these aggregates in sufficient amounts. The resistance of these soils to wind action was found to depend primarily on their ability to form secondary aggregates, or clods. The secondary aggregates preserved their identity below the surface even after repeated wetting and drying in the field. It was concluded, therefore, that the physical condition of the soil is indicated as well or better by methods such as dry sieving, which primarily measure the state of the secondary aggregates, than by methods that measure the state of the primary aggregates.

Selective Loss of Plant Nutrients by Erosion1

Abstract: Losses of soil and plant nutrients have been determined for six 3-acre watersheds under prevailing farming practices, and six 3-acre watersheds under a conservation farming system. The period reported, 1947–1950, was found to be close to normal with respect to rainfall. Comparative loss data was also obtained for the four crops represented on the watersheds, namely, corn, soybeans, wheat, and meadow. Erosion was found to be a selective process such that the eroded material contained considerably more plant nutrients than the soil from which it was eroded. This selective process resulted in a decrease in soil fertility, a decrease in organic matter, and changes in texture. The selective nature of the erosion process was found to be due to energy limitations of the runoff. It was found that as selective erosion progressed, the availability of certain soil fractions may be changed, which limited the selection. For areas under cultivation, the effects of selective erosion were found to be accentuated by increases in the availability of the more valuable soil constituents as a result of plowing, cultivation, or rill development. Evidence was obtained in contradiction to the concept that slight or geological erosion is a beneficial soil forming process.

Ammonium Fixation in Soils

Abstract: Laboratory experiments are reported which show the extent to which representative soils of the United States are able to fix ammonium, and the effect of various factors on fixation and on the availability of fixed ammonium to nitrifying bacteria. Especial attention is given to the comparative values obtained with KCl and CaCl₂ used as the extracting agents. It is shown that subsoils fix much more ammonium than surface soils. Considerable moist fixation may occur in soil if the predominant clay mineral is illite or vermiculite, and these values are increased by drying and heating. Montmorillonitic clays fix little ammonium unless heated. If ammonium-saturated soils are leached with N KCl, more fixed ammonium is left than if N CaCl₂ is used. Since potassium contracts some crystal lattices and calcium expands them, the value in the absence of salts would probably be intermediate. The availability to nitrifying bacteria of fixed ammonium in several soils during a period of 2 months varied between 5 and 24%, being lowest for vermiculite-containing soils and highest for those containing montmorillonite. Leaching with CaCl₂, as compared with KCl, resulted in somewhat higher availabilities of the residual ammonium. Low nitrification values for added ammonium salts were shown to be characteristic of soils that fix ammonium under moist conditions. The percentage nitrification in such soils is markedly increased if fixation is prevented. Ammonium fixation is shown to be a factor of importance in agriculture, especially where ammonium fertilizers are added to the plow sole of nonkaolinitic soils.

Mineral Content of Low Humic, Humic and Hydrol Humic Latosols of Hawaii1

Abstract: Data from X-ray diffraction, elemental, differential and integral thermal, and infrared absorption analyses were used to characterize quantitatively the minerals in the clay fractions of representative soils of the Low Humic, Humic and Hydrol Humic Latosols of Hawaii. Allophane was identified in substantial amounts (approximately 30%) in the < 0.2u fractions of two Hydrol Humic Latosols. Other minerals present in the clay fractions of the Hydrol Humic Latosols include gibbsite (25–35%), goethite (10–35%), magnetite (5–20%), mica (1–10%) and quartz (0–3%). The Humic Latosol contained kaolin (15–20%), gibbsite (15–20%), hematite (20–25%), goethite (10–20%), montmorin (5–10%), interstratified 2:1 layer silicate (5–10%), mica (1–5%) and quartz (1–5%). The Low Humic Latosols were predominantly kaolinic (45–55%) with hematite (15–25%), allophane (5–10%) and montmorin (5–15%) in substantial amounts. The fractions < 2u constitute the major portion of the Latosols. All percentages given are of the < 2u fractions except that two whole soils are included with the Low Humic Latosol group.

Report of the Committee on Physical Analyses 1951–1953, Soil Science Society of America

Abstract: THE present report deals with the efforts of the Standing Committee on Physical Analyses to formulate an acceptable standard procedure for making aggregate analysis of soils by the wet sieving method. Aggregate analysis by wet sieving is one of the methods by which soil scientists attempt to describe soil tilth quantitatively. Soil tilth is a conglomerated concept, analogous to soil fertility, suitability of a climate, or personality of an individual. It is an idea abstracted from numerous facts by means of personal judgment and will indubitably remain, therefore, a source of continued dissension. Yet, it is necessary in arriving at decisions or recommendations pertaining to practical soil management, to attach a scale of valuation to the idea of soil tilth and here the necessity for making quantitative measurements enters in. Unfortunately, the relation between soil tilth and the results of an aggregate analysis, however conducted, is tenuous, even qualitatively. A quantitative relation between the two cannot be expected, as the idea of soil tilth itself is too intangible. But, one cannot even state in general that soil tilth will be always more desirable as aggregate analysis indicates increased presence and greater stability of structural units. The indicated state of affairs has, of course, also a bearing on the preference for a method of making an aggregate analysis. For instance, one method will entail a greater destructive action on the soil as it is prepared for the analysis than will another. Whether one is more desirable than the other cannot be decided by objective methods. Or, the method of calculation of the results will shift emphasis in one direction or another in regard to the she of the ultimately resulting structural units. One method tends to show up the actual distribution of the latter units, whether they are primary particles or not, and another indicates the degree to which primary particles are united into aggregates. Even the method of taking the sample in the field cannot be decided upon objectively. Without a doubt, therefore, a greater future seems to be in store for measurement of such aspects of soil tilth that have a more direct and causal bearing on plant growth or on the mechanical behavior of the soil in regard to erosive forces and tillage implements. Nevertheless, there will always be an interest in aggregate analysis on account of the simplicity of the method, particularly with respect to the manner of obtaining the sample, and because laboratory preparations may be investigated with it. A notable and recent example of the latter is the fact that the laboratory and field evaluation of the so-called soil conditioners is, at present, for a greater part based on various forms of aggregate analysis. Because of the mentioned interest, the Committee adopted a method of making aggregate analyses which was a common denominator, as it were, of methods followed in a number of laboratories. A substantial amount of critical thought and discussion resulted in

Foliar Feeding of Corn with Urea Nitrogen1

Abstract: The application of supplemental nitrogen to corn by the use of urea foliar sprays was investigated. Injury in the form of marginal leaf burn was dependent upon both the concentration of the solution and the rate of application. The amount of injury could also be modified by additions of sugar, calcium hydroxide and potassium bicarbonate. Yield response of corn to foliar applied nitrogen was no greater than to the same amount of nitrogen applied as a side dressing. When injury occurred the yield response was reduced. The cause of the marginal leaf burn was investigated. Ammonia or nitrites did not appear to cause the injury. It was postulated that some product or a number of products of ammonia metabolism caused the injury. The beneficial effect of sucrose was believed to be due to the decreased rate of urea absorption and an increased rate of urea translocation within the plant.

Physicochemical Investigations of Clay-adsorbed Organic Colloids: II1

Abstract: The purpose of this study was to determine the sedimentation velocity and free diffusion behavior of humic acid extracted from Miami clay with neutral sodium pyrophosphate solution In addition the organic colloids extracted from several soils of the Miami catena were analyzed using the eletrophoretic technique The electrophoresis examination indicated that the organic colloids extracted from the clay fractions of a Brookston, Crosby, and Miami soil were similar In all cases it appeared that the extract consisted mainly of dark colored humic acid, with two additional colloids present in very small quantities The sedimentation velocity and free diffusion study showed that the humic colloid isolated from Miami clay was polydisperse with respect to particle size The following data were obtained for the colloid dissolved in a water solution: Sedimentation constant s₂₀ 28 × 10⁻¹³ cm/sec/dyne Diffusion constant D₂₀ 39 × 10⁻⁷ sq cm/sec Partial specific volume V 067 Frictional coefficient f/f₀ 23 Weight-average molecular weight Mw 53,000

A Diffusion‐Equilibrium Method for Obtaining Soil Gases under Field Conditions

Abstract: A soil gas sample obtained by mass flow of gases may not be representative of the point sampled because of mixing with gases from other soil depths or from the atmosphere. The authors have investigated a method which eliminates this error and which is based on the diffusion of gases between a point in the soil to a collection chamber via a tube tightly fitted in the soil. A physical analysis and laboratory tests were made to determine the time required for the collected gas to be representative of the soil atmosphere at any depth. For all conditions, this time depends on initial differences between the partial pressure of a gas in the collection chamber and in the soil. When the percentage of water-free pores in soil is approximately 20 or greater, the time is strongly dependent on the volume of the collection chamber and on the diameter and length of the tube connecting the chamber to a point in the soil. For porosities between 0–15%, the effect of reduced diffusion rates in soil becomes significant and increases the time. Equations are given for making these calculations. An evaluation was also made of the condition in which (1) approximate equilibrium had been previously established between partial pressures in the chamber and in the soil, and (2) partial pressures in the soil were changing due to release or absorption of a gas. It was shown that the pressure of a gas in the chamber will not differ from its partial pressure in the soil by more than 0.5% unless concentration changes in the soil exceed 15% by volume per day. Oxygen analyses are shown for 2-years field results. The average coefficient of variation of oxygen concentration was a low value of 3% but was strongly dependent on soil moisture content. Some comparisons of soil oxygen concentrations obtained by pumping and by the diffusion-equilibrium method showed that the former method gave higher values.

Correlation Between Nitrifiable Nitrogen and Yield Response of Corn to Nitrogen Fertilization on Iowa Soils1

Abstract: Nitrification rate is proposed as a procedure for evaluating nitrogen requirements of soils for the production of corn. By the use of a modified nitrification method the rate of nitrate production was compared with the response of corn to nitrogen fertilizer in a series of experiments conducted in Iowa over a period of seven years. A significant correlation was obtained between nitrification rate and the response of corn to the application of 40 to 60 lbs. of nitrogen per acre. The data serve to stress the influence of plant population density on the magnitude of yield response to nitrogen. At comparable rates of nitrification considerably higher yield responses to fertilization were obtained where the plant population was high than where it was low. In all population groups, however, a profitable yield response to nitrogen fertilization was obtained where the nitrification rate was less than 40 ppm. On fields with thick stands, profitable yield increases were generally obtained when the nitrification rate was less than 50 ppm.

Nine Essential Amino Acids in the Protein of Wheat and Barley Grown on Sulfur-Deficient Soil

Abstract: 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.