bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaporation from Soil Shrinkage Cracks
Authors: Adams John E. , Hanks R. J.
Published: July 2010

Field and laboratory studies have shown that evaporation from shriukage cracks may equal or exceed that from surface soil. Evaporation from moist soil samples (soil atmometers), suspended at various depths in naturally occurring shrinkage cracks in Houston Black clay, was determined. During the first 19 hours, the moisture evaporated at the 24‐inch depth was 55% of that evaporated at the surface. Soil atmometers suspended at depths of 12 inches or less were reduced from 55% soil moisture to < 17% in 44 hours. Crop cover affects evaporation in shrinkage cracks. Atmometers at the 12‐inch depth in grain sorghum lost half as much water as atmometers at the same depth in corn or permanent pasture. Field measurements showed from 2.9 to 4.6 times more surface area exposed on the shrinkage crack walls than as surface soil per square yard.

Laboratory studies indicate that evaporation from the side walls of shallow shrinkage cracks may vary from 35 to 91% of that from a comparable area of surface soil depending on soil moisture content. Wind tunnel studies with a simulated shrinkage crack 20 inches deep showed that evaporation increased at all depths as surface wind velocity increased. Increasing the wind velocity from calm to 25 mph. increased evaporation 570% at 2 inches below the surface and 100% at 18 inches. Evaporation increased as crack width decreased from 2.75 inches to 1.75 inches.
Estimating Bulk Density from Organic‐Matter Content in Some Vermont Forest Soils
Authors: Curtis Robert O. , Post Boyd W.
Published: July 2010

A close relationship between organic‐matter content and bulk density was found in the acid till forest soils of the Green Mountains of Vermont. Reasonably good estimates of bulk density can be made from determinations of organic matter content. Thus, the difficulties of direct determination of bulk density in these stony soils can be avoided. A method of determining bulk density, including a correction for stone content, is described for use in these stony soils.
Variations in Bulk Density and Moisture Content Within Two New Jersey Coastal Plain Soils, Lakeland and Lakehurst Sands
Authors: Reigner Irvin C. , Phillips John J.
Published: July 2010

To determine how manipulation of vegetative cover affects soil‐moisture storage, 8 plots were laid out in a 50‐acre block on the Coastal Plain of New Jersey, 4 on Lakeland sand and 4 on Lakehurst sand. Each plot, about 1/100 acre in size, was subdivided into 3 subplots, each of which was sampled gravimetrically 42 times over a period of 3 growing seasons.

A relationship between bulk density and soil depth plus stone content was developed. From this, bulk density was estimated for each sample in five 1‐foot layers. Moisture content by weight for each 1‐foot layer was converted to moisture content by volume by applying the respective estimated bulk densities. Variations within and between the relatively close‐spaced plots are presented for estimated bulk density and moisture content by voulme for each of the 1‐foot layers.
Determination of Total Nitrogen and Carbon in Soils by a Commercial Dumas Apparatus
Authors: Stewart B. A. , Porter L. K. , Beard W. E.
Published: July 2010

A modified Dumas procedure is presented, which extends its application to soils of high organic matter content. The modification eliminates the interference of CH4 that often causes values to be from 5 to 20% higher than Kjeldahl values. The instrument used for the Dumas procedure can be easily converted to determine C in soils. Changes necessary for this conversion are presented.
Oxidative Changes of Polyphenols as Influenced by Allophane
Authors: Kyuma Kazutake , Kawaguchi Keizaburo
Published: July 2010

Oxidative changes of polyphenols as influenced by allophane were studied in relation to humus‐forming processes in Ando soils. A chestnut tannin‐containing substrate was incubated for varying lengths of time with an allophanic material, and changes in the shape of ultraviolet (UV) and infrared (IR) spectra and in neutralization capacity of the polyphenols were traced with time. As compared with control materials, the allophanic material adsorbed large amounts of organic carbon (8 to 10 times as much at the end of 22 weeks), and the adsorbed organic matter kept incubated for only 2 weeks showed the following features: (1) No sharp peaks in UV spectrum at the 280 mµ region which is characteristic of tannin, (2) High optical density (about 20 times as high at 400 mµ as that of tannin), (3) High neutralization capacity (416 me. per 50 g. carbon, which is about 3 times as high as that of tannin), and (4) Strong 5.8 to 5.9 µ band in IR spectrum instead of a weak shoulder as for tannin. All these remarkable changes occurring in a very short period of time suggested that allophane might have some catalytic effect on oxidative changes of polyphenols, and a manometric determination of oxygen absorption confirmed this supposition. Such catalytic effect exerted by allophane would have great significance in humus formation and accumulation in Ando soils.
Some Chemical Characteristics of the Organic Matter Extracted from the O and B2 Horizons of a Gray Wooded Soil
Authors: Schnitzer M. , Gupta Umesh C.
Published: July 2010

Organic matter extracted from the O and B2 horizons of a Gray Wooded soil was characterized by ultimate and functional group analyses and by infrared spectroscopy. The analytical data were compared with those obtained by the use of the same methods on Podzol O and Bh organic matter.

The experimental data indicated that Gray Wooded humic and fulvic acids were chemically similar to Podzol humic and fulvic acids except that Gray Wooded organic matter contained more phenolic hydroxyl groups. In analogy with Podzols, approximately 70% of the organic matter extracted from the Gray Wooded O horizon was humic acid, while 90% of the extract from the B2 horizon consisted of fulvic acid.

Gray Wooded organic matter was difficult to extract and purify because of intimate association with clay and possibly other inorganic constituents.
Acidification of a Forest Tree Nursery Soil
Authors: Mullin R. E.
Published: July 2010

Artificial acidification of nursery soils for coniferous seedling production is being studied on soils which have become alkaline through continuous use. Three methods of acidification are being examined, acidification of the irrigation water, incorporation of acid peat, and incorporation of powdered S. The experimental work is being done on red pine (Pinus resinosa, Ait.) seedbeds used for production of 3‐0 shipping stock. The experiment is in three sections, starting in consecutive years, each running for three years in the nursery, and providing trees for observations in the laboratory and after outplanting. Acidification of the irrigation water, to pH 6.0 by automatic injection of H2SO4 has shown no measurable effect on soil pH or seedlings. Addition of acid peat, 60 cubic yards per acre, at about pH 5.0, showed some reduction in soil pH but not to the level desired, and no effect was determined on the seedlings. Addition of powdered S at 750, 1,500 and 2,250 pounds per acre has been most effective. The soil pH has been reduced proportionately, with that of the heaviest treatment to about pH 5.0, with some fluctuation, and the effect has not diminished after more than three years. The S treatment of 2,250 pounds caused mortality in the seedbeds, whereas the lesser treatments caused an increase in survival. Sulphur addition also resulted in taller, thicker, heavier seedlings with the first level causing a large increase, the second a minor (plateau effect), and the high level a large increase again. Information on the planting success of the seedlings is not yet available.
Water Vapor Diffusion in Relatively Dry Soil: II. Desorption Experiments
Authors: Jackson Ray D.
Published: July 2010

Water vapor diffusion during desorption was measured in three soil materials at water contents corresponding to a relative pressure range of 0.97 to about 0.05. The data were obtained from a transient desorption experiment conducted at 27°C. Diffusivities, calculated from analysis of water content distribution curves, increase and then decrease with increasing water content. The desorption diffusivity‐water content curves exhibit a less distinct maximum, with the maximum occurring at a higher water content than do the sorption diffusivity‐water content curves.
Adsorption of Phosphate by Aluminum and Iron in Soils
Authors: Hsu Pa Ho
Published: July 2010

A slightly acid soil was treated with dilute phosphate solutions of pH 7 to study the mechanism of phosphate fixation. Two reactions operating at different rates were recognized. The one which proceeded more rapidly is believed to be due to surface adsorption of phosphate on the amorphous aluminum hydroxides and iron oxides already in this soil. The other, a much slower reaction, is due to the surface adsorption on similar amorphous hydroxides and oxides developed during the experiment. Experimental work showed that the solubilities of variscite, of synthetic Al(OH)2H2PO4, and of synthetic Fe(OH)2H2PO4 were considerably increased in the presence of this soil indicating that these compounds are not likely to be the products of fixation under these conditions.
Some Aspects of Ammonia Sorption by Soil Surfaces
Authors: Coffee R. Clifford , Bartholomew W. V.
Published: July 2010

Rates of sorption of NH3 through soil surface boundaries, the extent of penetration into thin surface strata, and relative sorbing capacities of surface layers were determined for soil materials from several Coastal Plain and Piedmont soils. NH3 sorption through soil surface boundaries was rapid from aerial applications ranging from 1.3 to 1.9 mg. NH3‐N per cm.2 of surface area. Specific rate of sorption was directly proportional to the concentration of NH3 remaining above the soil surface. NH3 nitrogen sorbed by soil in the surface strata did not penetrate more than 10–20 mm. into the soil when applied at rates ranging from 0.17 to 1.00 mg. NH3‐N per cm.2 of surface. The depth distribution of NH3 changed with time of contact with NH3 without appreciable change in total NH3 sorbed. In general clay soils sorb more efficiently than sandy soils, soils with low pH more efficiently than those with high pH, and soils with high organic matter contents were less efficient than mineral soils with similar cation‐exchange capacities.
Influence of Sorbed Hydroxyl and Sulfate on Liming Efficiency, pH, and Conductivity
Authors: Mehlich A.
Published: July 2010

Soils having different values of permanent charge (CECp), variable charge (CECv), and anion‐exchange capacity (AEC) were treated with hydroxyl, sulfate and hydrogen saturated exchange resins. The AEC was then principally OH‐ or SO42‐ saturated while CECp was principally saturated with aluminohydronium and CECv with covalently bound H. To these systems were added increments of Ca(OH)2 and the release of SO42‐, Ca2+ sorption efficiency, pH, and conductivity measured. Soils containing sorbed SO42‐ had lower Ca2+ sorption efficiency, higher lime requirements, lower pH's and higher specific conductivities than those containing sorbed OH‐. These effects were the result of replacement of sorbed SO42‐ by OH‐ according to the reaction: Soil‐SO4 + Ca(OH)2 → Soil‐(OH)2 + CaSO4
Sulfate‐Sulfur Concentration as an Indicator of Sulfur Status in Various California Dryland Pasture Species
Authors: Jones Milton B. , Martin W. E.
Published: July 2010

Sulfate‐sulfur values in subclover and soft chess under high N fertilizer were approximately equal over a wide range of S fertilizer levels. With no fertilizer N the SO4‐S values of annual grasses including soft chess were higher than those of rose or subclover. Hardinggrass was particularly high in SO4‐S. Where no N was applied the SO4‐S concentration in subclover decreased as the plants advanced from early vegetative to flowering stage. When plants began to wilt at the end of the season, the SO4‐S values increased over SO4‐S levels at flowering. Subclover and rose clover, sampled during the flowering period but before wilting, appeared to be the best plants for determining the S status of dryland pastures in California.
Chloride‐36 Diffusion during Stable and Unstable Flow through Glass Beads
Authors: Biggar J. W. , Nielsen D. R.
Published: July 2010

The effect of the properties of solution on the mixing occurring in porous material has been examined in glass beads using Cl36. Matched NaCl solutions of 0.01, 0.1, and 4N concentration with either the displacing or displaced solutions identified by Cl36 were displaced from a 30‐cm. column. Displacements were made in the horizontal and vertical direction at two flow velocities. For solution density and viscosity differences of 0.0034 g. per ml. and 0.003 centipoise, respectively, between the displacing and displaced solution, unstable flow was clearly demonstrated. In the simple glass bead porous system, unstable flow may be of greater significance than the concentration dependent nature of the diffusion coefficient.
Oxygen Requirements of Cotton Seedling Roots for Penetration of Compacted Soil Cores
Authors: Tackett J. L. , Pearson R. W.
Published: July 2010

Cotton root growth and activity was determined at different levels of subsoil bulk density and O2 concentration. Subsoil cores of desired bulk density were aerated leaving both the soil moisture content intact and the surface soil exposed to diffusion of gases from the atmosphere. Measurements of root growth and activity in the subsoils included depth of root penetration, root yield, water uptake, and carbon dioxide production in the subsoil.

Mechanical impedance was more detrimental than low O2 for root growth in the subsoils at bulk densities above 1.5 g. cm.‐3. At lower densities root growth was depressed at O2 levels below 10%, and there was a strong interaction of O2 and bulk density.
Ion Adsorption on Charged Surfaces
Authors: Heald Walter R. , Frere Maurice H. , de Wit C. T.
Published: July 2010

A model, based on ion pair formation, for the adsorption of ions on charged surfaces is developed. This approach results in a two‐layer system analogous to the Stern‐Gouy model. Relations between the charge density, the fraction of the ions in the diffuse double layer, the concentration of the ions in the bulk solution, and a formation constant K are derived. The K describes the equilibrium reaction across the boundary between the two layers without defining the exact position of the boundary. Dowex‐50 resin, which has a high charge density and consequently a relatively small fraction of ions in the diffuse double layer, was used to test the above model. The following ratios of K's were calculated from data obtained from adsorption experiments in dilute solutions: KRb/KNa = 1.71, KRb/KK = 1.26, KK/KNa = 1.37, (K′Sr)½/KNa = 3.31 (eq. per liter)½, (K′Sr)½/KLi = 5.88 (eq. per liter)½, (K′Sr)½/KH = 4.00 (eq. per liter)½, KNa/KLi = 1.89, KNa/KH = 1.35, KSr/K′Ca = 1.56.
Relationships Between Soil Cation‐Exchange Capacity and the Toxicity of Ammonia to the Nitrification Process
Authors: Smith J. H.
Published: July 2010

Nitrification was studied in Red Bay sandy loam and Iredell clay loam treated with increments of sand to produce a range of cation‐exchange capacities (CEC). The soils were treated with 1% additions of alfalfa particles of three particle sizes. Analyses were made at intervals for ammonia, nitrate, nitrite, and pH.

The nitrification rate of ammonia from alfalfa particles decomposing in soil was decreased when the exchange capacity of the soil was decreased by dilution with sand. The mechanism involves less exchange sites for NH4+ at low CEC and the resulting increase in soil solution pH producing an NH3 concentration that is toxic to Nitrobacter. The same effect was produced by decreasing the distance between the alfalfa particles in the soil, thereby reducing the interparticle zones of low NH3 concentration where nitrification could proceed.

A steep ammonia concentration gradient develops around the alfalfa particles when adequate exchangeable hydrogen is present. In the areas between alfalfa particles, where NH3 concentration is low, nitrification proceeds without inhibition. As the exchangeable hydrogen concentration is reduced or the alfalfa particles are placed closer together, the zones where NH3 is not toxic decrease in size until most of the soil has reached the concentration of NH3 toxic to nitrification.
Moisture Relations of Soil Inclusions of a Texture Different from the Surrounding Soil
Authors: Grover Ben L. , Cahoon Garth A. , Hotchkiss C. W.
Published: July 2010

The rates of wetting and drying of soil inclusions, showed that the rate of rise of soil suction in the inclusion when compared to the surrounding soil was greatest with Ducor clay. The other soils followed in order of decreasing clay content. The rate of wetting was also greatest in the Ducor clay inclusion; the others were in the following order Coachella loamy sand > Ramona loam > Chino loam. The inclusions consisted of the soil ball on commercial nursery‐grown citrus trees. The ball was wrapped in burlap in the usual manner. The Chino loam inclusions took 3 times as long to wet as the surrounding soil when they were placed in either the clay or sand. The data indicated that extra caution must be used in orchard operation when the texture of the nursery soil is different from the field soil.
The Influence of Vegetation on Soil Thermal Regime at the San Dimas Lysimeters
Authors: Qashu Hasan K. , Zinke Paul J.
Published: July 2010

Soil temperatures for four lysimeters (bare, grass, scrub oak, and pine) during a 7‐year period (1952–1959) were studied. Observed temperature data of each lysimeter was subjected to harmonic analysis reducing the temperature time curves to a series of Fourier coefficients and the following empirical equations:

Tz = 62.70 + 18.53 exp (−0.1273z) sin (30t − 8.15 [3] −7.98z) °F. for the bare lysimeter

Tz = 58.20 + 16.02 exp (−0.1240z) sin (30t − 16.17 [4] −7.22z) °F. for the scrub oak lysimeter

Tz = 60.44 + 18.32 exp (−0.1167z) sin (30t − 15.48 [5] − 7.05z) °F. for the Coulter pine lysimeter

Tz = 60.96 + 17.43 exp (−0.1179z) sin (30t − 16.15 [6] −7.19z) °F. for the grass lysimeter

Presence of vegetation has altered the soil temperature regime by reducing mean annual soil temperature and temperature amplitudes. Vegetation has introduced patterns of time delay in the soil temperature profile characteristic of the vegetation cover and directly related to the soil moisture regime. When the lysimeters with vegetation cover are compared, the influence of vegetation is of varying magnitude as shown by marked differences in soil temperature regime and soil thermal properties.

With exception of the top 6 inches of soil, observed data for the average annual cycle of temperature agrees well with calculated values using the theory of heat flow. The slight difference in average monthly temperatures are much smaller than the natural differences from year to year.
Landform Parameters Correlated to Soil Drainage
Authors: Troeh Frederick R.
Published: July 2010

Quantitative means of describing land surfaces were developed in this study and related to soil drainage. Hundreds of elevations were determined on each of 40 plots representing 6 soil series. The 3‐dimensional equations developed to approximate these elevations assume radial symmetry and a parabolic relationship between elevation and distance from the symmetry axis. An electronic computer was used to solve and test equations for several positions in each plot. Areas that crossed soil boundaries were excluded. The equations of 75% of the remaining positions closely approximated the data and were used in this study. Parameters representing slope, rate of change of slope, and radius of curvature were obtained from the equations. These parameters were used to classify the shapes of the land surfaces both qualitatively and quantitatively. Three‐dimensional plots of these parameters correctly predicted the drainage class of 90% of the positions with usable equations. Surfaces having equivalent drainage at all points were defined by equations in terms of radius, slope, and rate of change of slope.
Persistence and Biological Reactions of Pesticides in Soils
Authors: Alexander M.
Published: July 2010

Although microorganisms are often considered to be omnivorous and biochemically omnipotent, they seem unable to destroy at significant rates many synthetic chemicals that enter soil. This unexplained microbial fallibility recently has assumed prominence because of the long persistence of a variety of pesticides. With at least certain compounds, the chemical, physiological, or environmental basis of the biological failings can be established, as illustrated with substituted phenols and phenoxy herbicides.

Microorganisms may detoxify pesticide‐treated soil by metabolizing or degrading the added substance. The microflora may also be responsible for the generation of a toxic condition in soil by activation of the applied pest‐control agent. The use of laboratory precedents as guides in investigations of natural transformations is considered, and instances of pesticide metabolism in soil are cited.
Soil Polysaccharides and Aggregation in Crop Sequences
Authors: Webber L. R.
Published: July 2010

Soil polysaccharides and aggregation (mean weight‐diameter and aggregate stability) were determined in the corn plots from a rotation project where the preceding crops were corn, oats, alfalfa‐brome, or winter wheat. The residues from these crops did not result in significant differences in the content of soil polysaccharides; only in a two‐year crop sequence, corn and oats underseeded with red clover, were the polysaccharides increased by the addition of manure. Aggregate stability was greater in the rotations that included a grass‐legume; manure improved aggregation over unmanured plots. In a multiple regression analysis, polysaccharides and organic matter together, accounted for 36% of the variation in mean weight‐diameter and 27% of the variation in aggregate stability.

The seasonal variation in the content of polysaccharides and aggregate stability showed a marked out‐of‐phase relationship except under oats, which were underseeded with a grass or legume.
Structural Arrangement of Functional Groups in Soil Humic Acid as Revealed by Infrared Analyses
Authors: Wagner G. H. , Stevenson F. J.
Published: July 2010

Humic acid from a brunizem soil was subjected to a series of treatments (methylation, saponification, acetylation) to determine the number and arrangement of functional groups when analyzed by a combination of chemical and infrared techniques. One‐third of the COOH groups (total COOH, 390 meq/100 g) occurred in positions close enough to form cyclic anhydrides; two‐thirds of the OH groups (total OH, 290 meq/100 g) were phenolic. Some phenolic OH groups in the samples failed to methylate wth diazomethane. Potassium bromide catalyzed the formation of cyclic anhydrides by mild thermal treatment of acid‐treated and methylated‐saponified humic acids, but not of untreated humic acid. Acetylation gave a small amount of brown material (acetyl content, 20%) whose infrared pattern was characteristic of an acetylated carbohydrate. Tests for quinone and H‐bonded phenolic OH groups were negative.
The Effect of Salts on the Dissolution of Monocalcium Phosphate
Authors: Taylor A. W. , Gurney E. L.
Published: July 2010

Additions of KCl, NH4NO3, or K2SO4 to Ca(H2PO4)2·H2O so complicate the dissolution processes that the final distribution of the phosphate cannot be interpreted in terms of the simple system CaO‐P2O5‐H2O as can the dissolution of Ca(H2PO4)2·H2O alone. In KCl and NH4NO3 mixtures, formation of Ca2KH7(PO4)4·2H2O and Ca2(NH4)H7(PO4)4·2H2O lowers the pH of the initial solutions to < 1 and decreases the initial phosphate concentrations; in the later stages both salts hydrolyze to CaHPO4·2H2O, but the amounts of phosphate remaining as this salt are less than that remaining from pure Ca(H2PO4)2·H2O. In mixtures containing K2SO4, Ca(H2PO4)2·H2O is rapidly decomposed with formation of syngenite, CaK2(SO4)2·H2O, and the phosphate is dissolved as KH2PO4. Sulfate decreases markedly the amount of residual phosphate.
The Effect of Nitrite and Organic Matter on Aerobic Gaseous Losses of Nitrogen from a Calcareous Soil
Authors: Meek B. D. , MacKenzie A. J.
Published: July 2010

The loss of gaseous nitrogen compounds when nitrite accumulates in a calcareous silty clay loam during nitrification was investigated under aerobic conditions.

Soil to which either (NH4)2SO4, NaNO2, or (NH4)2SO4 + barley straw was added, was incubated at 28C and 31% moisture for 28 days. Samples were maintained under aerobic conditions in a N‐free atmosphere of 21% oxygen and 79% helium. Gas samples were taken every 7 days from the incubation flasks and analyzed, using a gas chromatograph, for gaseous N products evolved. The accumulation of nitrite was measured on separate soil samples incubated in the same manner as the flasks used to secure gas samples.

The gaseous N forms produced were N2O and N2. It was found that losses were low even when large amounts (250 ppm) of nitrite‐N accumulated. The gaseous N loss was 1.3% for (NH4)2SO4 and NaNO2 and 3.6% for the (NH4)2SO4 + barley straw treatment.
High Cesium Uptake in Wheat Seedlings Cultured with Ammonium
Authors: Minotti Peter L. , Craig Doris , Jackson W. A.
Published: July 2010

Wheat seedlings grown exclusively on NH4‐N, relative to those grown exclusively on NO3‐N or without N, consistently demonstrated a markedly high capacity for subsequent Cs absorption from solutions labelled with Cs137. In addition, previous nitrogen nutrition greatly influenced the relative distribution of absorbed Cs, with percentage transport of Cs to tops being greatest in seedlings cultured with NO3. The results could not be explained on the basis of either K content or respiratory substrate levels prior to the uptake periods.
Preparation of Thin Sections from Moist Organic Soil Materials
Authors: Langton John E. , Lee Gerhard B.
Published: July 2010

Micromorphologic investigation of Histosols requires use of thin sections prepared in such a way as to minimize shrinkage and disruption of natural soil fabric. A method which meets these requirements is described. Moist samples are impregnated with Carbowax 6,000, mounted with Castoglas, and ground and polished by special techniques. Little shrinkage or destruction of soil fabric occurred in thin sections prepared by this method from a variety of organic soil materials.
The Significance of Nonsymbiotic Nitrogen Fixation
Authors: Knowles R.
Published: July 2010

Estimates of the rate of nonsymbiotic fixation of N215 were calculated on an area basis for several natural woodland and cultivated field soils. Results supported the conclusion that much of the nitrogen gain in the field may be associated with periods or regions of anaerobiosis, or with localized available energy sources. There was agreement with many earlier conclusions drawn from nitrogen balance experiments.
The Effect of Soil Temperature on the Availability of Indigenous Soil Zinc
Authors: Bauer A. , Lindsay W. L.
Published: July 2010

A short‐term growth chamber experiment was used to study the effect of soil temperature on the availability of indigenous soil zinc. Zinc‐deficient weld loam was incubated for periods of 0, 1, 3 and 6 weeks at temperatures of 5, 17, 31 and 43C and treated with 0 and 0.75 ppm Zn as ZnSO4·7H2O, immediately before plant‐soil contact. Two‐week‐old corn plants (Zea mays) used as the assay crop were allowed to exploit the previously incubated soil for a 2‐week uptake period.

During this period both yield and the uptake of Zn was increased from soil previously incubated at 43C for 1 to 3 weeks. The 6‐week incubation period tended to reduce available Zn over shorter periods. The addition of Zn fertilizer showed that Zn was a limiting factor in growth at the lower temperatures. Chemical extractions commonly used as soil tests for Zn were not sufficiently sensitive to detect the Zn made available to plants by soil incubation.
Effect of Underlying Residua on Chemical and Mineralogical Properties of Soils Developed in a Uniform Loess Overlay
Authors: Hutcheson T. B. , Bailey H. H.
Published: July 2010

Chemical properties; sand, silt and clay mineralogy; and particle size distributions are compared and found to support the concept that Lexington, Wellston, Bewleyville, and Dewey soil series were developed in wiedly different residua overlain by a rather uniform loess mantle. Data presented indicate greater weathering of the loess mantle when it is underlain by coarser textured residual material as well as illuviation of materials from the loess mantle into and/or through the coarse textured residuum. Thinner loess overlays tend to exhibit significant mixing with underlying materials from the residuum.
Effect of Phosphorus on Some Physical Properties of Soils: I. Modulus of Rupture
Authors: Lutz J. F. , Pinto Rafael A.
Published: July 2010

Applications of phosphorus, both as phosphoric acid and as monocalcium phosphate, to three soils were very effective in reducing the hardness of soils as measured by modulus of rupture. Phosphoric acid was more effective than monocalcium phosphate on all three soils. Both sources of P were more effective on Iredell soil, which consists predominantly of montmorillonite with some kaolinite, than on White Store soil, which contains montmorillonite and kaolinite but with some illite. Even though both sources of P produced significant decreases in modulus of rupture on the Georgeville soil, which contained predominately 1:1 clay minerals, the results were not as striking as on the Iredell. The greatest effect per unit of P was produced by the smaller increments, especially by the 50‐ppm rate. This is especially important from both agronomic and economic standpoints since 50 to 100 lb/acre are feasible rates.
Quantitative Determination of Vermiculite in Soils
Authors: Alexiades C. A. , Jackson M. L.
Published: July 2010

A chemical method based on potassium fixation was developed for quantitative determination of vermiculite in soils. The cation‐exchange capacity (CEC) of a sample is determined by washing with CaCl2 and replacement of Ca with MgCl2. The sample is then washed with KCl, heated to 110C overnight to dehydrate and collapse the layers of vermiculite and to fix K. The K remaining exchangeable is determined by NH4Cl washings. The difference between these two CEC values gives the interlayer charge of vermiculite. A number of vermiculite standards and soil samples of widely different clay mineral compositions give remarkably near 100% totals when the vermiculite content is based on the average value of interlayer charge of 154 meq/100 g of vermiculite and when the other minerals present are appropriately determined (mica by K2O, chlorite by ignition loss, montmorillonite by CEC measured by non‐fixed K, quartz and feldspar by Na2S2O7 fusion, allophane, kaolinite, and halloysite by selective dissolution in NaOH). The total CEC of vermiculite is 159 meq/100 g when the allocated external surface charge of 5 meq is included.
Effect of pH on Leaching Losses of Potassium Applied to Forest Nursery Soils
Authors: Krause H. H.
Published: July 2010

A lysimeter experiment was conducted to determine the effect of soil pH on adsorption and leaching of applied K. The experimental soil was a fine sand. The pH was adjusted to 4.3, 5.1, and 6.4. The soils of different reaction were treated at increasing rates with K2SO4 and exposed to rainfall and irrigation. Periodic collection and analysis of leachates over 1 year showed that K losses from strongly acid (pH 4.3) soil were 1.7 to 2.4 times higher than losses from moderately acid (pH 5.1) soil, and 2.5 to 3.5 times higher than losses from weakly acid (pH 6.4) soil. Seasons of greatest K leaching were late fall, early spring, and wet periods during summer.

The results show a need for an adjustment of rate and frequency of K fertilization according to pH and base saturation of individual nursery soils, and stress the importance of liming of strongly acid nursery soils.
Recording CO2 in Soil‐Root Systems with a Potentiometric Membrane Electrode
Authors: Jensen C. R. , Van Gundy S. D. , Stolzy L. H.
Published: July 2010

A commercial electrode was evaluated for measuring the partial pressure of CO2 in soil. Carbon dioxide was monitored in containers of Yolo silt loam, with and without a growing tomato plant (Lycopersicum esculentum), and compared with gas chromatograph measurements of simultaneous soil air samples. A linear correlation coefficient of 0.98 between the two methods was obtained, although the electrode departs slightly from linearity below 2% CO2. Small increases of CO2 pressure in the soil were observed immediately following small additions of water; these increases could be followed continuously by the electrode. The CO2 electrode should prove practical for both greenhouse and field measurements.
The Influence of Soil Moisture, Soil Texture, Drying Conditions, and Exchangeable Cations on Soil Strength
Authors: Gerard C. J.
Published: July 2010

Empirical relationships expressing soil strength for different combinations of silt‐clay and sand mixtures as functions of soil moisture, drying conditions, and exchangeable Na+ content of the silt‐clay fraction were determined. Soil strength data indicate that moisture content, drying conditions, texture, and kind and level of exchangeable cations of the soil and interactions of these factors play significant roles on soil strength and the soil strength‐moisture relationships. Strength of briquets increases (i) with decreasing soil moisture, reaching a maximum when moisture content was reduced to 2 to 3 monomolecular layers of water; (ii) with increasing silt and clay and exchangeable Na+ content; and (iii) by slow drying. The cohesive actions of water molecules during slow drying, similar to the dispersing action of Na+, increase close‐packing of soil particles and, therefore, soil strength. Fast drying produces briquets of lower strength due to disruptive action of rapidly escaping water molecules on the arrangement of soil particles.
Release of Potassium from Soil Fractions During Cropping
Authors: Doll E. C. , Mortland M. M. , Lawton K. , Ellis B. G.
Published: July 2010

Soil fractions from six soils known to vary in ability to supply K to field crops were cropped intensively in greenhouse experiments. All soils and soil fractions were Mg‐saturated prior to conducting the experiments. The K content of the clay and of the silt was linearly correlated with the logarithm of the K uptake for each fraction, except for the silt fraction of one soil. No correlation was noted between the uptake of K and the K content of the entire soil. In equilibrium experiments, K in solution in 1.0n MgOAc after 90 days was linearly correlated to the K content of the clay. A similar correlation was obtained with the entire soil. The different pattern of K release during cropping tests as compared to the equilibrium studies is attributed to rate processes which would govern release during cropping, but which would not be a factor in the equilibrium experiment. X‐ray analyses indicated the formation of expanding lattice clays upon the removal of interlayer K by cropping. Large amounts of K were removed from the coarse clay (2.0–0.2µ), intermediate amounts from the medium clay (0.2–0.08µ), and small amounts from the fine fraction (<0.08µ). This differential release of K by the different size clay fractions can be explained by a decrease in the activity of interlayer K when the K content of the clay is decreased.
Potassium Availability in Nason Soil as Influenced by Ammonium and Lime
Authors: Murdock L. W. , Rich C. I.
Published: July 2010

A greenhouse experiment was established to find if NH4+ increases K+ availability when Nason silt loam is limed to pH 7.0 as suggested by previous laboratory studies.

Two oat crops were grown in soil at 3 lime levels (1, 5, and 15 g/1,000 g), 2 K levels (0 and 0.5 meq/100 g) and 2 N sources [Mg(NO3)2 and NH4NO3]. At high soil pH, potassium uptake was significantly greater where the N source was NH4NO3 as compared to Mg(NO3)2. The results support soil extraction data which show that at about pH 7.0, NH4+ ions are considerably more efficient in displacing K+ from this soil than are Mg2+ ions. It is concluded that the smaller NH4+ ions are able to penetrate to exchange positions not accessible to large hydrated Mg2+ ions.

The results do not support an explanation of the differential K uptake based on the antagonistic effect of Mg2+ ions on K+ nor due to an effect caused by lower soil pH with NH4NO3 fertilization.

Although K fixation occurs at high pH in this soil, this fixation does not appear to be associated with greater collapse of expansible vermiculite. In fact, it is shown that liming caused the vermiculite to be less subject to collapse on K saturation. The reason for the greater fixation at high pH may be that there is less competition for the specific sites by H3O+ ions and thus greater opportunity for selection of K+ ions which are of similar size.
Estimating Soil and Saturation Extract Composition by a Computer Method
Authors: Paul J. L. , Tanji K. K. , Anderson W. D.
Published: July 2010

Five soil samples were salinized with NaCl and CaSO4.2H2O. They were extracted at 1:1 and saturation moisture content, and the chemical composition of the soils and extracts was determined. Exchange constants, for Na‐Ca and Mg‐Ca exchange, in combination with chemical data derived from samples at 1:1 moisture content were used in a computer program to predict soil and extract composition at saturation. The computer procedure, developed by Dutt, proved very satisfactory in estimating chemical makeup at saturation.
Factors Controlling the Extractability of Soil Zinc
Authors: Martens D. C. , Chesters G. , Peterson L. A.
Published: July 2010

The effect of total zinc, pH, and contents of clay and organic C on the extractability of soil Zn by Aspergillus niger, 0.1n HCl, dithizone, and 0.2m MgSO4 for 57 Wisconsin soils was evaluated by simple, partial, and multiple correlation.

The relative amount of soil Zn extracted by the Zn tests was in the order A. niger > 0.1n HCl > dithizone > 0.2m MgSO4 extractable Zn. Simple, partial, and multiple correlation data indicated that the fungus extracts a fixed fraction of the total soil Zn. Consequently, total Zn and A. niger‐extractable Zn were of approximately equal importance in the prediction of Zn uptake by plants. Statistical interactions between clay and organic C content in relation to the amount of Zn extracted by 0.1n HCl were explained on the basis of organo‐clay complex formation. An increase in organic matter content at constant levels of clay increased the amount of Zn bound by the organo‐clay complex thereby resulting in increased extractability of soil Zn by 0.1n HCl. On the basis of correlation data and the greater extractability of Zn by 0.1n HCl than dithizone, it was concluded that much of the Zn extracted by 0.1n HCl over dithizone is not extractable by plants. It was shown that the amount of Zn extracted by 0.2m MgSO4 varied inversely with pH; clay and organic C contents had less effect on the relationship suggesting that 0.2m MgSO4 extracts only solution and readily exchangeable Zn.
Optimum Nutrient Levels in Potato Leaves (Solanum tuberosum L.)
Authors: MacKay D. C. , MacEachern C. R. , Bishop R. F.
Published: July 2010

Field experiments involving six rates of each of the nutrients N, P, and K were conducted at 18 locations over a 3‐year period. Comparison of polynomial response curves for tuber yields with those for nutrient content of uppermost mature leaves collected at the 10% bloom stage suggested optimum levels of 6.5, 0.50, and 3.9% for N, P, and K, respectively.

The optimum level for K was the most satisfactory of the three nutrients because moderate yield deficiencies resulted in large differences in leaf concentrations. However, on soils high in exchangeable K, responses to K fertilization were obtained at higher leaf levels than on soils low in K.

The optimum level derived for N appeared to be fairly stable. On coarse‐textured soils, or where a combination of factors produced unusually high yields, somewhat higher leaf levels, at the stage sampled, were apparently necessary to prevent deficiency.

The optimum level obtained for P was the least satisfactory, since there was considerable variation as a result of season and soil series. However, where yields were < 90% of the maximum, the P content was invariably well below the overall optimum value.
An Evaluation of the Mechanisms Governing the Supply of Ca, Mg, K, and Na to Soybean Roots (Glycine max)
Authors: Oliver S. , Barber S. A.
Published: July 2010

Three mechanisms, root interception, mass‐flow, and diffusion, govern the rate of supply of nutrients from the soil mass to the plant root. Two experiments were conducted to evaluate methods developed for calculating the supply of ions to the root by mass‐flow and by root interception. Root interception values were calculated by assuming that all the exchangeable and soluble ions were in the pore space and that the roots intercepted an amount in proportion to their volume. Mass‐flow was calculated by multiplying the amount of water uptake of the plant by the concentration of ions in this water as determined from analysis of a saturation extract.

Contributions of mass‐flow were varied by creating three rates of transpiration. The results indicated that mass‐flow was significant for supplying Ca and Mg but was of little importance for Na and K in the soil used. Increases in mass‐flow of Ca and Mg were highly correlated with increases in the uptake of Ca and Mg by the plant.

In a second experiment, root interception of Ca and Mg was varied by using soil‐sand mixtures varying from 100% soil to 20% soil and 80% sand. Mass‐flow was minimized by leaching the soil before use. The results indicated that the calculated Ca uptake by root interception gave a reasonably close approximation to uptake of Ca minus mass‐flow Ca.
Source and Placement of Zinc and Phosphorus for Corn (Zea mays L.)
Authors: Brown A. L. , Krantz B. A.
Published: July 2010

The effects of source and placement of zinc and phosphorus were studied in several greenhouse experiments. A Zn and P deficient soil was utilized and sweet corn was grown as the test plant.

When Zn fertilizer materials were mixed well with the soil ZnSO4 and organic sources such as ZnEDTA and Rayplex‐Zn were equivalent in their effectiveness for the correction of Zn deficiency. However, if the fertilizer was banded under the seed, ZnEDTA was more effective than the inorganic sources.

A small amount of mixing appeared to improve the effectiveness of Zn, or P, or both fertilizers markedly.

Granulation greatly reduced the effectiveness of ZnSO4, ZnNH4PO4, and Rayplex‐Zn.
Closed‐System Freezing of Unsaturated Soil
Authors: Dirksen C. , Miller R. D.
Published: July 2010

Recent developments in the theory of soil freezing and frost heaving led to the conclusion that pores directly adjacent to a growing ice lens ought to be filled with water. The literature contains fragmentary reports of heaving of soils that were not saturated with water and which lacked an external source of water. It was thought that this apparent anomaly might be explained by postulating that before lens growth and heaving began, local saturation was achieved by thermal water transfer.

Experiments confirm that heaving sometimes occurs in moist closed soil columns, initially at uniform temperature and water content, when the temperature at one end is lowered below the ice point and kept at that temperature while the other end is held at the original temperature. The region just ahead of the advancing ice front does not become saturated in the expected manner, but instead suffers a net loss of water. Water lost from the unfrozen soil enters the frozen soil, and causes its water (ice) content to increase for a considerable distance behind the 0 C isotherm. This transport within the frozen soil exceeded by several orders of magnitude that which can be accounted for as vapor movement through the unfilled pore space and thus, it was concluded, must take place in the liquid phase. Whenever and wherever the degree of saturation reaches about 0.9, a further increase in water content is accompanied by heaving. The frozen soil actively extracts water from the unfrozen soil, supposedly due to attenuation of the iquid water films associated with ice surfaces. The resultant water content gradient in the unfrozen soil induces hydraulic flow toward the frozen soil. During the early stages of the experiments thermal transport in the unfrozen soil is inconsequential compared with this hydraulic flow. Later the rate of ice accumulation diminishes, the hydraulic gradient is dissipated, and the thermal water transport becomes relatively more important, by default. By that time heaving has virtually ceased. Thermal water transport is, therefore, not essential for heaving in moist soils that lack an external source of water.
Soil Aggregate Stabilization by the Indigenous Microflora as Affected by Temperature
Authors: Harris R. F. , Chesters G. , Allen O. N.
Published: July 2010

The water‐stability of sucrose‐amended aggregates of Waupun silt loam incubated at 15, 25, and 35C, and the aggregate‐stabilizing characteristics of microorganisms isolated from these aggregates were evaluated. Aggregate water‐stability determined by wet‐sieving was expressed as the percentage of soil material bound into water‐stable aggregates 0.5 to 1 mm, 1 to 2 mm, and > 2 mm in size. Microbial development was investigated by microscopic and dilution plate techniques.

Fungi isolated from the aggregates differed in their ability to effect aggregate stabilization in the presence and absence of sucrose. Stabil zation by effective fungi was a function mainly of the binding of soil particles into > 2‐mm water‐stable aggregates and was related closely to the onset and subsequent development of macroscopic mycelia on the aggregates. Stabilization of aggregates by sporeforming bacteria involved the production of a high percentage of <2‐mm aggregates, especially in the early stages of incubation. Bacterial stabilization was initiated earlier but was maintained for a shorter time as incubation temperature increased from 15 to 35C; maximum aggregate stability effected at 15 and 25C was almost twice that reached at 35C.

Maximum stabilization by the indigenous microflora occurred within 4 days at all 3 temperatures; appreciable stability was maintained for 84, 14, and 4 days at 15, 25, and 35C, respectively. Bacteria were primarily responsible for the initial stabilization of aggregates incubated at 15 and 25C and contributed to the initial stabilization of aggregates incubated at 35C. The fungal species involved in aggregate stabilization varied with temperature.
Mineralization and Immobilization of Nitrogen in Bacterial Cells and in Certain Soil Organic Fractions
Authors: Chu J. P‐H. , Knowles R.
Published: July 2010

Nitrogen15‐enriched Pseudomonas cells and (NH4)2SO4 were added separately to a Chicot sandy loam and to a black spruce raw humus (F horizon). At intervals from zero to 100 days the soil N was fractionated (Cheng and Kurtz, 1963) into: exchangeable NH4+‐ + NO3‐‐N, fixed NH4+‐N, N in acid hydrolyzate (i.e. NH4+ from hydrolysis, amino sugar‐N, amino acid‐N, acid‐soluble alkali‐insoluble humin‐N), and acid insoluble humin‐N.

At zero time 92.5 and 93.0% of the added NH4+‐N appeared in the exchangeable fraction of the two soils, respectively; 55.3 and 83.7% of the added cell‐N appeared in the amino acid fraction of the two soils, respectively. During incubation in both soils about 40% of the added NH4+‐N remained in the exchangeable fraction and 50 to 60% was immobilized in the amino acid fraction. In the raw humus about 13% of the added NH4+‐N appeared in the insoluble humin fraction. In both soils 20–30% of the added cell‐N was rapidly mineralized but at least 50% remained in the amino acid fraction. There was evidence of a “priming effect” or “N interchange” resulting in increased mineralization of native soil organic N. This effect was particularly pronounced in the raw humus.