bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption of N‐Butane by Kaolinite and Montmorillonite: Phase Changes in the Monolayer Region
Authors: Jurinak J. J. , Volman D. H.
Published: July 2010

The adsorption of n‐butane by Ca‐kaolinite and Ca‐montmorillonite, using high vacuum technique, was studied to determine the nature of the differences that occur during the adsorption of nonpolar molecules by clay minerals. The adsorption is described in terms of a 2‐dimensional mobile film with the spreading pressure, ϕ, calculated by the integrated Gibbs equation. At surface coverages of < 4%, the adsorbed films on both surfaces can be described as an ideal 2‐dimensional gas, i.e., ϕA = kT, where A is the molecule area, k is Boltzman's constant, and T is the absolute temperature. Throughout the monolayer region, adsorption of n‐butane could be described as either a perfect or imperfect gaseous film. The ϕA — ϕ curves show that a transition from a liquid expanded to a liquid intermediate phase occurs in the imperfect gas region of both clay systems. The differences noted in the nature of the phase changes on both surfaces coupled with the isosteric heats of adsorption is explained on the basis that kaolinite is essentially nonporous and has a homogeneous surface, whereas the presence of capillary pores dominates the adsorption of n‐butane by montmorillonite.
Digestion of Clay‐Protein, Lignin‐Protein, and Silica‐Protein Complexes by Enzymes and Bacteria
Authors: Estermann Eva F. , Peterson G. H. , McLaben A. D.
Published: July 2010

As a contribution to an understanding of the stability of organic matter in soil, and to knowledge of microbial activity at solid‐liquid interfaces generally, the relative influence of clay‐protein and lignin‐protein complex formation in retarding protein mineralization by enzymes and bacteria is evaluated. We have found that monolayers of lysozyme adsorbed on kaolinite and bentonite can be digested by chymotrypsin, mixed soil cultures, and pure cultures of B. subtilis, B. mycoides, and Pseudomonas sp. In contrast, lignin‐protein complexes are extremely resistant to attack. Montmorillonite‐protein monolayer formation retards the rate of enzymatic proteolysis; however, most of the protein can be hydrolyzed under optimum conditions in one day with a resultant decrease in X‐ray diffraction (001) spacings. For equal clay surface areas, a mixture of soil infusion organisms or pure cultures of soil organisms hydrolyze protein freshly adsorbed on montmorillonite or kaolinite at rates nearly equal to that of free, i.e., nonadsorbed, protein, all being compared in aqueous suspension. A decrease in X‐ray (001) spacing of protein‐montmorillonite complexes is observed following digestion by the organisms. Dried, rewetted montmorillonite‐protein complexes are more resistant to attack by soil organisms than freshly prepared complexes. Complexes of protein with silica gel are somewhat comparable to lignin‐protein complexes in being resistant to digestion by Pseudomonas sp.
The Influence of Soil Conditions, Following Tractor Logging, on the Growth of Planted Douglas‐Fir Seedlings
Authors: Youngberg C. T.
Published: July 2010

Growth of planted Douglas‐fir seedlings was investigated on Reddish Brown Latosol soils on two cutover areas in the Cascade Mountains of western Oregon.

In April 1955, 2‐0 seedlings were planted on tractor roads, in loose berm material adjacent to the tractor roads, and on undisturbed cutover condition. First‐year survival for all conditions was over 90%. Annual height measurements were made at the end of the 1955 and 1956 growing seasons. Differences in height growth between seedlings on the cutover condition and those on the berm and tractor road conditions were highly significant. Seedling growth differences between berm and tractor road conditions were also statistically significant in several instances. Soil analysis data indicated poor growing conditions on the tractor roads, particularly in regard to aeration, moisture, and N relationships.
Outline of a Generalized Theory of Soil Genesis
Authors: Simonson Roy W.
Published: July 2010

Processes of soil formation have been related to prominent great soil groups by means of names such as podzolization, laterization, and solonization. A change from this point of view seems necessary when soils of the world are considered as a continuum with a number of properties in common. It is therefore proposed that soil genesis be considered as two overlapping steps; viz, the accumulation of parent materials and the differentiation of horizons in the profile. Of these two steps, the second is of more immediate concern to soil scientists.

Horizon differentiation is ascribed to additions, removals, transfers, and transformations within the soil system. Examples of important changes that contribute to development of horizons are additions of organic matter, removals of soluble salts and carbonates, transfers of humus and sesquioxides, and transformations of primary minerals into secondary minerals. It is postulated that these kinds of changes, as well as others, proceed simultaneously in all soils. It is further suggested that the balance within the combination of changes governs the ultimate nature of the soil profile. If this point of view is valid, the same kinds of changes occur in horizon differentiation in soils as unlike as Chernozems and Latosols, but the balance among the processes is not the same.
Genesis of Miami Silt Loam
Authors: Thorp James , Cady John G. , Gamble Erling E.
Published: July 2010

Miami silt loam and other Gray‐Brown Podzolic soils of the United States and Canada are developed from calcareous parent materials of glacial, glacial‐fluvial or loessial origin; a large proportion of these materials were deposited during the Wisconsin stage of glaciation. Study of thin sections with polarized light shows clearly that much of the clay of the B2 horizon has been carried in by water and deposited. Studies of the clay fraction of the soil and parent material indicate that much of the clay was either unaltered or has been transformed from clay originally present, but that some was formed by weathering of primary minerals. Characteristics of the A horizon may be ascribed to the joint effects of leaching, eluviation, and the influence of the broad‐leaved deciduous forest and the associated macro‐ and micro‐fauna. Recent leaching experiments, using “undisturbed” soil columns of Miami silt loam, suggest that B horizons are developed primarily through translocation of suspended fine clay and some humus, especially after the periods of soil drying in late summer and early autumn.
The Genesis of the Red‐Yellow Podzolic Soils
Authors: McCaleb Stanley B.
Published: July 2010

Mineralogical, chemical, physical, and morphological data are given for 18 profiles of Red‐Yellow Podzolic soils. These soils represent 3 profiles each of 2 sequences, one derived from acid crystalline rocks and the other from sandstones. Six profiles of Reddish Brown Lateritic soils are included for comparison where appropriate.

Differences between sequences and within sequences are due either to inherited or to genetic properties, both of which are related to or limited by parent material. All properties studied follow the same kind of distribution with depth. Differences in magnitude reflect inherited differences, whereas the kind of distribution reflects similar genetic differences under uniform environments. Apparent discrepancies in the distribution with depth of clay content, exchange capacity, and associated properties occur as differences in parent materials. Differences in secondary products are also related to differences in parent materials and in turn are related to the observed differences.

Suggested mechanisms for the genesis of these soils and their characteristic mottling are presented. The Red‐Yellow Podzolic soils are compared to the Gray‐Brown Podzolic soils in terms of probable genesis.
Relative Water Losses by Evaporation and Transpiration in Field Corn
Authors: Peters D. B. , Russell M. B.
Published: July 2010

The separation of transpiration by corn and evaporation from the soil was experimentally accomplished, in the field, by covering the ground surface with polyethylene plastic. It was found that as much as 50% of total evapotranspiration could be accounted for by evaporation from the soil surface. Transpiration was found to be influenced in a minor way by plant population and soil moisture environment. Corn yields were depressed in only 1 year by elimination of summer rainfall.
Theoretical Aspects of Flow Above the Water Table in Tile Drainage of Shallow Homogeneous Soils
Authors: Bouwer Herman
Published: July 2010

Hypothetical conductivity‐tension relationships were employed in a study to determine the effect of the thickness of the capillary fringe and the relative conductivity above the capillary fringe on drainage flow. Solutions were obtained with an electrical resistance network using equivalent conductivities.

A capillary fringe of 50 cm. increased the drainage coefficients in shallow soil by 24 to 57%, depending on the height of the water table. Smaller increases can be expected with decreasing thickness of the fringe and increasing depth of the impermeable layer. Agreement existed between the results of the network analyses and calculated drainage coefficients, including the effect of the capillary fringe with Hooghoudt's method.

The effect of the flow above the capillary fringe on the drainage coefficient appeared to be small so that the flux across the top of the capillary fringe can be assumed to be uniform. Steady‐state drainage coefficients, therefore, can be used to calculate the rate of fall of the water table after cessation of rain when the region near the top of the capillary fringe becomes a source of almost uniform flow because of drainage of pore space.

For a certain water‐table position midway between drains, the water table in the vicinity of the drains appeared to be higher with increasing thickness of the capillary fringe. Since hysteresis causes the fringe thickness to be greater for falling water tables than for rising water tables, lower water tables near the drains can be expected with the latter.
Certain Physico‐Chemical Properties of the Pinchen Clay and the Function of Its Free Iron Oxide and Organic Matter
Authors: Kun‐Huang Houng , Tsen‐tuo Chen
Published: July 2010

Tension‐moisture content relationships of the deferrated soils and control soil indicated that available moisture was reduced from 10.3% to 7.3% as the result of deferration.

From the study of vapor adsorption isotherms, the constants of the BET equation were derived. Deferration increased the standard free energy of adsorption of water on the bare surface, ΔF°1, and decreased the specific surface, S, while oxidation decreased both ΔF°1 and S. The deferrated clay was dispersed easier by humic acid, showed less buffering effect against Ba(OH)2, and a decrease in exchange capacity; whereas oxidized clay gave a stronger buffering effect against NaOH. The energy of replacement of Ca by K showed no difference between variously treated clays, indicating binding force of cations at exchange sites was little affected by presence of organic matter or iron oxide.

It was concluded that the principal clay minerals and free iron oxide forming fine porous coating might be regarded as the dominant factors affecting moisture and surface characteristics of the Pinchen clay.
Calcium Phosphate Fertilizers: III. The Effect of Surface Area on the Availability Coefficients of the Dicalcium Phosphates
Authors: Bouldin D. R. , Sample E. C.
Published: July 2010

Several granule sizes (ranging from 20 to 40 mesh to < 325 mesh) of dicalcium phosphate dihydrate (DCPD) and anhydrous dicalcium phosphate (DCPA) were compared in a greenhouse experiment with corn forage grown on Mountview silt loam, pH 6.6. Several comparable screen‐size separates varied with respect to the size of the component crystals. Plant response increased with decreasing granule size.

Geometric surface areas of the fertilizers were estimated from the counted number of granules and the size of the granules. Relative rates of solution, which are roughly proportional to geometric surface area, were also measured.

The linear correlation coefficients between (a) availability coefficient indexes and geometric surface area were 0.94 and 0.69 for the DCPA and DCPD fertilizers, respectively, and (b) availability coefficient indexes and relative rates of solution were 0.98 and 0.85 for the DCPA and DCPD fertilizers, respectively.

The results of these experiments indicate that the availability coefficients of different granule sizes of DCPD and DCPA are primarily dependent upon geometric surface area of the granules and are not much influenced by variations in size of the component crystals in the granule. Per unit of surface area, the availability coefficient of the DCPD is about 2.3 times that of the DCPA.
Extractable Sulfate‐Sulfur in Soils of Florida in Relation to Amount of Clay in the Profile
Authors: Neller J. R.
Published: July 2010

Sulfate‐S was extracted from the profiles of a number of uncropped soils, using samples obtained in soil surveys. The extractant used was sodium acetate adjusted to pH 4.8 with acetic acid.

Little or no sulfate‐S was found in the surface horizons of the soils studied but considerable amounts were present in many of the subsurface layers. These deposits of sulfate‐S were found generally where clay was present in the profile. The amounts of sulfate‐S increase with increase in clay in a highly significant manner and generally at a much greater rate of increase. There appears to be some relation between amounts of sulfate and types of clay.

Rainfall on these soils adds about 5 pounds of S annually per acre and much of this sulfate probably leaches down through the sandy surface layers that characterize many of the soils of Florida.
Solubility Criteria for the Existence of Variscite in Soils
Authors: Lindsay W. L. , Peech Michael , Clark J. S.
Published: July 2010

The pKsp value of a highly purified synthetic variscite, Al(OH)2H2PO4, was found to be 30.5 at 25° C. The equilibrium between variscite and its constituent ions in solution was attained only very slowly. The solubility criteria obtained in this study would indicate that the immediate reaction products of applied phosphate in acid soils are much more soluble than variscite but, upon ageing, these intermediate reaction products are slowly transformed into variscite which may coexist with gibbsite as stable solid phases.
Rubidium‐Potassium Relations in the Soil‐Plant System
Authors: Fried Maurice , Hawkes George , Mackie W. Z.
Published: July 2010

Potassium and Rb are taken up by plants in a constant ration to that in the substrate, when the substrate is a resin sand mixture. In soils the apparent independent reactions of K and Rb with the soil dominate the supply of these ions to the plant. These reactions tend to mask the competition that is presumed to occur between these ions in the ion uptake process. Increase in the rate of applied Rb was shown to decrease the percent of the added Rb fixed and markedly increase the percent of the added Rb taken up by the plant. High rates of applied K had only a slight effect on Rb uptake. Rubidium did not appear suitable as an “isotope” of K in soil studies.
Soil Temperature and the Early Growth of Corn from Mulched and Unmulched Soil
Authors: van Wijk W. R. , Larson W. E. , Burrows W. C.
Published: July 2010

On corn plots in Iowa, South Carolina, Ohio and Minnesota which were treated with oat straw either plowed under or on the surface and with two levels of N, measurements were made of soil temperature at the 4‐inch depth, and these measurements were correlated with dry matter yields of corn early in the season. The data from Iowa, Minnesota and Ohio support a theory that early season corn growth is decreased by low temperatures caused by a mulch of crop residues. The data from South Carolina, where soil temperatures were considerably higher than in the three other states, showed that the mulch did not appreciably influence the growth rates. The data from all four of the states agreed in a general way with data of Lehenbauer who found that for a range of temperatures from about 50° to 86° F. there is an increase with temperature of seedling growth rate; whereas around 86° to 90° F. there is little influence; and from about 90° to 111° F. there is a decrease. From the soil temperature measurements taken at a 4‐inch depth it was shown how temperatures for other depths could be deduced from a theoretical expression based on heat flow theory. A detailed example of the use of the heat flow theory in studying the mulch problem in practical experimentation is presented.
Differential Thermograms of Selected Organic Acids and Derivatives
Authors: Chesters G. , Allen O. N. , Attoe O. J.
Published: July 2010

Thirty‐eight organic acids and derivatives were characterized by differential thermal analysis (DTA) employing free access of air. Each thermogram was readily distinguished from the others, inclusive of such closely related acids as fumaric and maleic (cis‐trans isomers), and pyrogallic acid (1:2:3 trihydroxy‐benzene) and phloroglucinol (1:3:5 trihydroxy‐benzene). In general, the peaks were sharp and duplication of the thermograms was highly satisfactory. Although the mechanism involved was not clearly elucidated, the thermograms evidenced fundamental differences in molecular structure.
The Formation of Nitrate from Ammonium Nitrogen in Soils: III Influence of Temperature and Initial Population of Nitrifying Organisms on the Maximum Rate and Delay Period
Authors: Sabey B. R. , Frederick L. R. , Bartholomew W. V.
Published: July 2010

A number of soils of varying properties were incubated at several temperatures and rates of inoculation of nitrifying organisms to determine the influence of these factors on nitrification. The time‐nitrification curve generally exhibited a “delay” phase and a “maximum rate” phase followed by a phase in which the rate of nitrification declined as the substrate was exhausted and the end product concentration increased. Each phase must be measured and characterized before difference in nitrification in soils can be fully understood and described.

In soils incubated at field capacity, the maximum nitrification rates increased from immeasurably low values to as great as 900 ppm. per week in some soils and the delay periods decreased from about 32 weeks to < 1 day, as temperatures increased from 0 to 25° C. Increase in initial population of nitrifying organisms caused decreases in delay periods but did not appreciably affect the maximum rate above 10° C. The influence of temperature and nitrifying population on delay periods and maximum rates varied greatly among soils indicating that other factors inherent in the soils also affect nitrification.
Chemical and Clay Mineralogical Properties of Certain Memphis Catena Soils of Western Kentucky
Authors: Hutcheson T. B. , Lewis R. J. , Seay W. A.
Published: July 2010

Chemical and clay mineralogical properties of Memphis, Grenada, Calloway and Henry series were determined and related to degree of internal drainage and genesis. Percent base saturation and other chemical data indicated that the more poorly drained profiles were more severely leached than better drained members. These data, together with the occurrence of larger proportions of expanding lattice 2:1 type minerals to nonexpanding 2:1 types in the more poorly drained profiles, suggest that a high degree of weathering was attained before pan horizon formation occurred.

The presence of lower exchangeable Ca/Mg + Na ratios along with lower montmorillonite/vermiculite ratios in B3m horizons than in deeper or shallower horizons suggests that the pans are the result of packing of dispersed clay particles and that vermiculite has formed from montmorillonite or other weathering products in those horizons.
Cholesterol as a Standard in the X‐Ray Diffraction of Clay Minerals
Authors: Kittrick J. A.
Published: July 2010

Cholesterol was found to be a satisfactory standard with which to align X‐ray diffractometers for work with the relatively long spacings which are the chief diagnostic characteristic of clay minerals. Sensitivity of peak intensity and position to various diffractometer adjustments was determined, and improved results with clay minerals were demonstrated. Alignment of the diffractometer at some relatively short spacing introduces the risk of obtaining a long‐spacing peak of diminished intensity or no peak at all. However, good alignment at a relatively long spacing ensures good alignment at shorter spacings as well.
Boron Adsorption and Release by Soils
Authors: Biggar J. W. , Fireman Milton
Published: July 2010

The Langmuir adsorption equation was found to describe the adsorption of boron from solution by three soils up to a limited concentration. Agreement for a fourth soil was not as good. Wetting and drying of the soil following the addition of B waters increased the maximum adsorption capacity and bonding energy of the soil for B.

Leaching and successive extraction experiments indicated a relationship between the bonding energy of the soils for B and their release characteristics. Boron removal from three soils indicated a desorption type of release, whereas release by a fourth soil appears similar to the formation of a saturated solution of a chemical compound. These findings indicate that the difference in the release patterns may be expected to affect the absorption of B by plants and the removal of B from the soil.
Infiltration Rates in Frozen Soils in Northern Minnesota
Authors: Stoeckeler J. H. , Weitzman Sidney
Published: July 2010

Infiltration tests were conducted in northern Minnesota forests and grassland using single‐ring steel cylinders. Concretely frozen silt loam soils showed 0.09 inch of infiltration per hour, while sands of similar frost type showed 0.47 inch. A porous‐concrete frost type was found in loamy sands; in these soils infiltration amounts were 2.19 inches for the porous‐concrete frost, 3.97 inches in partly frozen soils, and 13.22 inches in unfrozen soils. The impermeable concrete type of frost was most prevalent in sod land, while in the forest the more permeable types were present.
Relation of Soil Moisture to Ion Absorption by Corn Plants
Authors: Mederski H. J. , Wilson J. H.
Published: July 2010

A split‐root technique was devised in which the top portion of the roots of corn plants developed in sand culture while the remaining portion of the root system developed in soil adjusted to seven known moisture contents in the range of wilting point to field capacity. With this system, plants were grown from seed for a 25‐day period without addition of water to the soil and with only a small loss of the original soil water content. Plants were grown at two levels of atmospheric humidity at each level of soil moisture.

Dry weight of plant tops and roots developed in the soil increased linearly with increasing soil moisture. Both percent and total P, K, and Mg in the plants increased with increasing level of soil moisture. Level of humidity appears to interact with the effect of soil moisture on ion absorption.
The Effect of Soil Water Movement vs. Phosphate Diffusion On Growth and Phosphorus Content of Corn and Soybeans
Authors: Shapiro Raymond E. , Armiger W. H. , Fried Maurice
Published: July 2010

The effect of soil water movement vs. phosphate diffusion on plant growth and composition was studied by soil‐sand dilution and continuous movement of the soil solution by recirculation. Yield, percent P, and P uptake of corn and soybeans remained approximately constant at soil‐sand dilutions up to 1:1.1 by volume, but decreased at greater dilutions in both the recirculated and noncirculated (normal watering) systems. Recirculation increased yield and percent P of corn and soybeans. These increases were attributed partly to the sampling of a larger soil volume for replenishment of the soil solution. The diffusion process alone was unable to renew P at the root surface as fast as the observed uptake rate. Soil water movement probably accounts for a much greater transfer of P to the root surface than diffusion.
Nitric Acid Oxidation of the Organic Matter of a Podzol
Authors: Schnitzer M. , Wright J. R.
Published: July 2010

The organic matter of the A0 and Bh horizons of a podzol has been oxidized with 1:1 nitric acid. About 60% of the organic matter of both materials was converted to CO2. In the oxidation product of the A0 material, succinic, glutaric, adipic, benzene tetra‐ and penta‐carboxylic and picric acids were identified. The oxidation product of the Bh material contained benzene tetra‐ and penta‐carboxylic and picric acids but no aliphatic carboxylic acids. The acids identified represented about 5% of the original organic matter of both materials. The results suggest that the organic matter of the Bh contained more aromatic structures than that of the A0 horizon. The possible significance of the acids identified with regard to the chemical structure of the organic matter preparations from both horizons is discussed.
The Effect of Low Temperatures on Nitrification of Ammonia in Cecil Sandy Loam
Authors: Anderson O. E.
Published: July 2010

Anhydrous ammonia (NH3) at the rate of 150 ppm. NH4‐N was applied to samples of Cecil sandy loam in the laboratory in a manner simulating field application. Initial concentration at the center of the absorption zone was 800 ppm. NH4‐N. NH4NO3 at rates 0, 50, 100, 200 and 400 ppm. NH4‐N was also applied to the Cecil soil. Nitrification occurring at 37°, 42°, 47° and 52° F. was studied. Nitrification, though negligible, occurred in all samples at 37° F. At 42°, nitrification became noticeably active by the 3‐ to 6‐week period in NH3 samples, and NH4NO3 samples treated with 50 ppm. NH4‐N. Compared to the latter, nitrate accumulation decreased as NH4NO3 concentration increased. This effect was particularly noticeable at 47° and 52° F. where nitrification of NH3 and NH4NO3, up to 100 ppm. NH4‐N, was moderate. At 52° F. nitrification approached completion in the 50 ppm. NH4‐N samples by the 9th week, and in the NH3 samples by the 12th week. Nitrate accumulation during 12 weeks expressed as a percentage of that occurring at 52° F. was 93, 51, and 8% at 47°, 42°, and 37° F., respectively, in NH4NO3 samples treated with 50 ppm. NH4‐N. In samples treated with NH3 it was 72, 35, and 4%, respectively, at the same temperatures.
The Germination of Small Grain and Corn as Influenced by Urea and Other Nitrogenous Fertilizers
Authors: Brage B. L. , Zich W. R. , Fine L. O.
Published: July 2010

Field experiments comparing the use of urea to other fertilizers were performed. The fertilizer was placed with the seed in all but two experiments.

Urea containing 2.5% biuret reduced stands of small grain by 30% when the equivalent of 20 pounds nitrogen per acre was applied with the seed. Ammonium nitrate at 80 pounds nitrogen per acre caused a reduction in stand of 10%. Stands were depressed by 25 and 60% when 40 and 80 pounds nitrogen, respectively, as reagent urea were used per acre.

Urea, containing 10% biuret, applied broadcast at 160 pounds nitrogen per acre, caused no damage to germination of either corn or barley.

Urea was intermediate between ammonium carbonate (most damaging) and ammonium nitrate in a greenhouse germination trial.

When fertilizer was mixed with the soil in the laboratory, considerable ammonia was evolved from the soil atmosphere by aeration when either urea, ammonium hydroxide or ammonium carbonate was used. Only traces of ammonia were removed from soils treated with either ammonium nitrate, ammonium sulfate or biuret. Ammonia gas formed from urea, and the contaminant biuret in urea, are therefore both instrumental in causing commercial urea to be toxic to germinating seeds.
Some Gilgaied Soils in South Dakota
Authors: White Everett M. , Bonestell Robert G.
Published: July 2010

The addition of material to the lower part of the solum by the swelling of clay down into desiccation voids seems to be the first step in the genesis of South Dakota gilgai. The microridges of wavy gilgai are formed by (a) the cyclic movement of microvalley subsoil material along oblique cleavage planes into the microridge; (b) a slower downslope soil creep of microridges than of microvalleys; and (c) the upward extrusion of material from a compacted microridge subsoil as it is moistened and clays swell. Normal gilgai are formed by extrusion. Gilgaied areas have soils similar to Chestnuts, Solodized‐Solonetz, Solonchaks, or complexes of these soils.
An Experiment in Ordination of Some Soil Profiles
Authors: Hole Francis D. , Hironaka M.
Published: July 2010

“Ordination” as defined by Goodall is “an arrangement of units in a uni‐ or multidimensional order.” The authors have attempted to apply this method of classification to soil profiles.

Data concerning three groups of soil profiles were treated separately in order to show the degrees of similarity and dissimilarity between the profiles. Soils of the Miami family and catena were examined in this manner twice, once on the basis of laboratory data and a second time on the basis of current detailed soil profile descriptions. The two treatments gave some strikingly similar results. The third group of soils consisted of 25 soil profiles considered to be representative of as many great soil groups of the world. A three‐dimensional model showing relationships between these profiles illustrates the possibilities of this kind of analysis.
Cropping‐Management Factor Evaluations for a Universal Soil‐Loss Equation
Authors: Wischmeier Walter H.
Published: July 2010

About 8,000 plot‐years of soil‐loss and related data assembled from 21 states were analyzed to evaluate influences of vegetal growth, crop sequence, tillage practices, fertility, and residue management on erosion of soil by rainfall. Specific‐crop data were grouped according to relatively homogeneous intervals such as the respective rough fallow, seedbed, establishment, growing crop, and residue periods. For each such period, measured soil losses under specific combinations of crop sequence and management were compared with corresponding losses from bare fallow. Not only canopy protection, but the residual effects of prior cropping and management as well, differed significantly for the respective crop‐stage periods. Soil losses for each crop‐stage period under various sequences and management levels are presented in tabular form as percentages of losses from fallow under identical rainfall. The table was designed for use with rainfall erosion index maps and monthly distribution curves computed from localized rainfall records as discussed in “A Rainfall Erosion Index for a Universal Soil‐Loss Equation” (Soil Sci. Soc. Am. Proc. 23:246–249. 1959). Combined with the erosion index and other factors comprising the soil‐loss equation, the tabulated values will help to provide valuable guides for conservation farm planning adapted to the local rainfall pattern.
Moisture Storage on Fallowed Wheatland in the Great Plains
Authors: Mathews O. R. , Army T. J.
Published: July 2010

Moisture storage data during the fallow period of annually cropped and alternately cropped‐fallowed wheatland from 25 locations throughout the Great Plains were summarized and statistically analyzed. Data, representing over 450 crop‐fallow periods, showed that on the average 2.02 inches of water was stored during the fallow portion of an annual cropping system. Under an alternate crop‐fallow system, an average of 3.96 inches of precipitation was stored between the harvest of one crop and the seeding of the next.

The amount of moisture stored during the fallow period was found to be related to soil moisture content at the beginning of the fallow period, and the amount of precipitation during the fallow period. Moisture storage efficiency (percent of total precipitation stored) was greater in the northern than in the southern Great Plains.
The Hydrolysis of Aluminum Salts in Clay and Soil Systems
Authors: Ragland John L. , Coleman N. T.
Published: July 2010

Aluminum salts undergo more extensive hydrolysis in acid soil and clay systems than in aqueous solutions of the same pH. The “increased hydrolysis” is accompanied by, and presumably is caused by, the sorption of the hydrolysis product which contains Al. As much as 0.2 mmol. of Al was removed from 10‐3M AlCl3 solution by 1 g. of montmorillonite; kaolinite and a soil clay sorbed comparable amounts of the hydrolysis product.

During the “increased hydrolysis” reaction, 3 moles of H+ appeared for each mole of Al which hydrolyzed and was sorbed. When clays containing hydrolysis products were treated with dilute mineral acid, 3 moles of H+ were required for each mole of Al dissolved. Although it appears from the above that the sorbed substance is of composition Al(OH)3, the solubility product of gibbsite was not exceeded in many of the acid systems in which the “increased hydrolysis” occurred. It is suggested that the loss of Al(OH)3 from solution occurred through the deposition of Al(OH)3 units on clay surfaces.
Chemical Nature of the Nitrogen in the Fulvic Fraction of Soil Organic Matter
Authors: Stevenson F. J.
Published: July 2010

A study of the forms of N in the fulvic fraction of soil organic matter showed that about one‐half of the N occurred in compounds which deaminated readily by acid and base hydrolysis. About one‐fourth of the N existed in amino acids; about one‐tenth in amino sugars.

Through a modification of Forsyth's selective adsorption technique, the fulvic extract from a Brunizem soil was fractionated into several components, a number of which were pigmented. All of the components contained amino acids; several contained amino sugars. The N compounds which formed NH3 by hydrolysis occurred primarily in association with pigments. A physicochemical study of the colloids of fulvic extracts showed that the colloids were heterogeneous with respect to both charge and particle size.

A consideration of possible mechanisms for the formation of fulvic pigments in soil prompted the author to postulate that the pigments originated through the condensation of carbonyl compounds with amino derivatives, by mechanisms similar to those proposed for browning processes in natural products.
Control of Soil Moisture Regimes in Greenhouse Studies by the Neutron Method
Authors: Twersky Marvin , Hillsman George
Published: July 2010

A calibration curve for measurement of soil moisture regimes by the neutron method is shown for a greenhouse study. A linear regression analysis was used to determine the equation for the best fitting neutron‐soil moisture data. The equation was established by relating percent of neutron standard and tension in atmospheres. This relationship was determined as log T = c + bY where T is tension in atmospheres and Y is percent of neutron standard.
Studies on the Suspension Effect With a Sodium Electrode
Authors: Bower C. A.
Published: July 2010

Soil and clay suspensions containing Na+ exhibited the suspension effect when emf readings were made with a calomel electrode and a glass electrode which is selective for Na+. The suspension effect was identified with the KCl salt bridge of the calomel electrode. Overbeek has proposed an approximate equation for calculating the magnitude of the suspension effect when a saturated KCl salt bridge is employed. The equation is based on the relative contributions of the electric double layer at the surface of the particles and the bulk of the liquid to the total electrical conductance of the suspension. Values for the suspension effect calculated by Overbeek's equation from electrical conductivity measurements agreed closely with those obtained potentiometrically. As predicted by Overbeek's equation, the magnitude of the suspension effect was found to vary in an orderly manner with the electrolyte concentration and the exchangeable‐sodium‐percentage of the suspension. The magnitude of the suspension effect was also found to be a function of the KCl concentration of the salt bridge. An explanation for this finding based on an extension of Overbeek's theory is proposed.
Development of Molybdenum Deficiency Symptoms in Certain Crop Plants
Authors: Peterson Nobel K. , Purvis E. R.
Published: July 2010

Molybdenum deficiency symptoms in six important crop plants were developed, described, and photographed. Deficiency symptoms were developed in the first generation of broccoli, cauliflower, and tobacco; in the second generation of corn, cotton and soybeans.

With large seeded crops it was necessary to develop seed low in molybdenum before severe deficiency symptoms could be produced. In the case of corn and cotton, germination of the molybdenum‐deficient seed was at a slower and lower rate than for seed adequately supplied with the element. First generation cotton plants which received nutrient solution purified of molybdenum developed abnormal bolls.

Molybdenum deficiency symptoms were developed in plants grown in a pyrex glass cullet‐wool mixture, pyrex glass sand, quartz sand, and aerated nutrient solution. The macronutrient stock solutions were purified of molybdenum by copper sulfide coprecipitation technique.
Effect of Drying Some Ohio Soils Upon the Soil Test for Potassium
Authors: Jones J. B. , Mederski H. J. , Hoff D. J. , Wilson J. H.
Published: July 2010

Most Ohio soils release K (from a nonexchangeable form to exchangeable) upon air drying from the field‐moist state. The amount released varies from 25 to 100 pounds per acre depending upon soil type. The effect of this release upon the interpretation of soil test recommendations was found to be not significant. Correlations between soil test level and corn yield response to K fertilization were the same or better using air‐dried samples as compared with the field‐moist samples. Further drying at 110°C. for 24 hours slightly increased or decreased the amount of exchangeable K depending upon the soil type. These values were, in some instances, poorly related to the yield response. Of the three procedures, air drying at room temperature prior to extraction gave the best estimate of the available K level.
Tactoid Size and Osmotic Swelling in Calcium Montmorillonite
Authors: Blackmore A. V. , Miller R. D.
Published: July 2010

Various workers in recent years have found that the Gouy‐Chapman theory of the diffuse electrical double layer provides useful predictions of swelling behavior of certain 2:1 clays in dilute solutions. Calcium‐saturated montmorillonite was apparently an exception. It swelled appreciably in dilute CaCl2 solutions, but much less than predicted by theory, and to an extent depending on previous compression history.

Earlier swelling studies with calcium montmorillonite were repeated with similar (but not identical) results. In addition, specimens with various histories of compression were examined by X‐ray diffraction methods. Every specimen showed [001] spacings of 18.8Å., regardless of degree of compression or reswelling. Analysis of the 18.8Å. diffraction peaks by literal use of the Scherrer equation indicated that in uncompressed material (prepared by resin exchange from the sodium form) packets, or “tactoids” averaging about 4.5 montmorillonite particles each, produced the diffracted beam. The indicated number of particles increased irreversibly to about 8 as the maximum pressure experienced by a specimen increased to 100 atm. These results suggest that volume changes of compressed specimens were not associated with elastic bending of montmorillonite particles.

Literal use of the Scherrer equation permits estimation of average spacing between tactoids from water content data. The slope of curves relating this spacing to pressure were surprisingly close to that predicted by application of double‐layer equations, but large “dead volume” corrections must be applied if this is to be taken as evidence that swelling in calcium montmorillonite is in reasonable agreement with double‐layer theory.

It is concluded that the lowest energy state for calcium montmorillonite in dilute CaCl2 is represented by a single “crystal” with 18.8Å. [001] spacing. Where attainment of this ordered state is prevented by imperfect orientation, swelling can occur, and is not incompatible with osmotic repulsion inherent in the diffuse double‐layer model.
Plant Growth, Water Use and Nutritional Response to Rhizosphere Differentials of Oxygen Concentration
Authors: Letey J. , Lunt O. R. , Stolzy L. H. , Szuszkiewicz T. E.
Published: July 2010

Various oxygen level treatments were applied to snapdragons grown in cylinders by varying the oxygen concentration above the soil surface. Other soil physical properties were held relatively uniform during the experiment. The aerial portions, except for part of the stem, were isolated from the rhizosphere treatments. Eight treatments ranging from < 1% to 21% O2 were applied. In general plant growth increased with higher oxygen levels. The relative content of phosphorus and potassium in shoots increased with increasing oxygen concentration. Sodium content increased with decreasing oxygen and showed a very marked increase at the lowest oxygen levels. Water use decreased with decreasing oxygen.
An Evaluation of Phosphorus Fertilizers Applied Broadcast on Calcareous Soils for Corn
Authors: Webb John R. , Eik Kalju , Pesek John T.
Published: July 2010

Five field experiments were conducted in which several slightly water‐soluble P sources were compared with concentrated superphosphate (CSP) for use in broadcast applications for corn. The tests involved rates of 30 and 60 pounds of available P2O5 per acre and were located on calcareous Webster soils which tested low in available P.

The sources could be ranked into three groups as measured by their effect upon the concentration of P in corn leaves and upon corn yields. CSP and dicalcium phosphate dihydrate were the most effective sources, with the former being slightly superior. Anhydrous dicalcium phosphate, calcium metaphosphate, and a chemical blend of mono‐and dicalcium phosphate were of intermediate effectiveness, producing yield increases of about 70 to 80% of that given by CSP. Granular calcium metaphosphate was the least effective source, being about 60% as effective as CSP in promoting yield increases.

It was concluded that on calcareous soils a highly water soluble source of P, such as CSP, is likely to be more effective in broadcast applications for corn than are most slightly soluble sources. However, other characteristics of the fertilizer may be of equal importance in determining their value. Some evidence was also obtained which indicated that increasing the granule size of the less soluble fertilizers tended to reduce their effectiveness.
The Problem of Stones in Soil‐Moisture Measurement
Authors: Reinhart K. G.
Published: July 2010

The presence of stones in soil poses a serious problem in soil‐moisture measurement, especially in forest soils. In gravimetric sampling, moisture‐content estimates can be improved by removing stones from the samples and deducting their weight from the total soil weight and the weight of moisture in the stones from weight of moisture in the sample. Adjustments must also be made in determining soil bulk density when moisture content by volume is desired and in applying soil‐moisture values to soil areas that include stone.
Iron Adsorption by Montmorillonite Systems: II. Determination of Adsorbed Iron
Authors: Page A. L. , Whittig L. D.
Published: July 2010

Comparison of methods for determination of Fe adsorption capacity of montmorillonite and a qualitative method for differentiation of adsorbed and precipitated Fe are presented.

Separate H‐montmorillonite samples (Wyoming Clay Spur, < 1µ diameter) were exchange‐saturated by washing with FeCl3, Fe2(SO4)3 and Fe(NO3)3 solutions. Excess ions were removed with either distilled H2O, absolute methanol, 95% ethanol, or 0.003M HCl. Fe retained by the systems after washing was removed with acidified 1N NH4OAc.

Fe(III) removed after 0.003M HCl washing was essentially the same in all systems (between 1.17 and 1.25 me. per g.) but was much higher (up to 2.2 me. per g.) and quite variable from H2O or alcohol‐washed samples. The 0.003M HCl washing was found to remove negligible amounts of adsorbed iron. Base titration curves of all the samples were essentially the same, indicating that each system retained the same amounts of adsorbed Fe.

The data indicate that excess Fe was precipitated in the systems where H2O and alcohols were employed for removal of the excess ions. Data are presented which show that adsorbed Fe may be qualitatively differentiated from precipitated Fe in the systems studied by using NH4F solution as an extracting reagent.
Calibration and Characteristics of Two Neutron Moisture Probes
Authors: van Bavel C. H. M. , Nielsen D. R. , Davidson J. M.
Published: July 2010

The effect of the size of cylindrical containers filled with soil on the calibration of two types of neutron probes was investigated for moisture contents up to 0.25 volume fraction. Neutron count rates were appreciably affected by the value of both diameter and height up to 3 feet. Differences between 3 and 4 feet were samll.

The response of the end‐source probe was linear within the range investigated (0 to 0.40 volume fraction). The data also show that the end‐source probe design as compared with the centered‐source design is more efficient and, therefore, requires a smaller radioactive source for equal precision.

Once an accurate calibration with soil is available, verifying calibration of probes may be done with NaCl or H3BO3 solutions, limited to probes of identical design but differing efficiencies or source strengths. Relations found between soil moisture content and solution concentration are given.

A discussion of the range of measurement of soil moisture content with neutron probes is presented, comparing various literature data.
Soil Moisture Measurements with the Neutron Method Supplement Weighing Lysimeters
Authors: McGuinness J. L. , Dreibelbis F. R. , Harrold L. L.
Published: July 2010

Evaluation of soil moisture changes with the neutron method agreed closely with that obtained from the weighing lysimeters. Evapotranspiration can be determined with either method by the equation ET = P ‐ G ‐ Q ± Δ M where ET = evapotranspiration, P = precipitation, G = percolation, Q = surface runoff and ΔM = change in soil moisture.

Differences were shown in the soil moisture extraction pattern under deep‐rooted and shallow‐rooted meadow crops. The hydrologic implications of this difference are discussed.
The Effect of Temperature and Moisture on Exchangeable Potassium
Authors: Burns Allan F. , Barber Stanley A.
Published: July 2010

The influence of temperature and moisture on the release of nonexchangeable K to the exchangeable form was studied in the laboratory. Varying moisture from 60 to 100% of moisture equivalent was found to have no effect on the release of nonexchangeable K at temperatures from 1° to 80° C. Temperature caused increases in the level of exchangeable K in all but one case. The higher the temperature, the greater was the rate of release of nonexchangeable K.

The first release of K appeared to conform to a first‐order reaction, while subsequent release was of a zero‐order nature. Activation energies were determined from data obtained by the incubation of soils at three temperatures. These values were in the range of 11,000 to 26,000 cal. per mole.

Data obtained by oven‐drying soils before and after incubation at 118° C. indicate that the increases in exchangeable K obtained by these two methods were due to different reactions.