bluuebunny/crossref_metadata_2025 huggingface dataset:
Organic Materials Which Stabilize Natural Soil Aggregates
Authors: Greenland D. J. , Lindstrom G. R. , Quirk J. P.
Published: July 2010

The effect of periodate followed by sodium borate treatment on the stabilities of prewet soil aggregates has been determined by a permeability technique and by wetsieving. The effect of periodate treatment depends on the history of the site, the depth, and the great soil group from which the sample is taken. The stabilities of aggregates from various Red Brown Earths were all reduced by periodate treatment. The reduction was small for samples from plots which had been under pasture for many years, but very large for samples which had been under pasture for 4 years or less, or which were continuously cropped. The stabilities of all subsurface samples of the Red Brown Earths were completely destroyed by periodate treatment. Aggregates taken from a Solonized Brown soil were much less sensitive to periodate treatment, and those taken from a Rendzina were with one exception unaffected. These soils contain free CaCO3. It is probable that the most important function of the periodate treatment is to cause breakdown of the polysaccharides and polyuronides in the soil, and the results show that in cropped soils and soils under young pastures aggregate stability is primarily due to these materials. In soils under older pastures, or soils which contain free CaCO3, other materials prevent aggregate breakdown.
Sterilization of Soil by Irradiation and Some Further Observations on Soil Enzyme Activity
Authors: McLaren A. D. , Luse R. A. , Skujins J. J.
Published: July 2010

As an introduction to the study of radiation‐sterilized soil as a medium for microbial and plant growth, survival curves for microorganisms have been obtained with 5 and 9 Mev. electrons, hard X‐ray and gamma radiation. For a given soil, bacterial survival curves with these radiations are almost superimposable, but they differ among soils. Bacterial numbers in soils approach zero at 2 Mrep. doses, but 4 Mrep. doses are necessary to insure complete sterility for larger soil volumes.

Soil sterilized by radiation still manifests enzyme activity (phosphatase, urease) in the presence of suitable substrates. If this is a general situation, studies of the uptake of some organic nutrients from sterile soil by sterile root systems will not be free from the problem of hydrolysis in situ. Sterilized soil is not toxic toward tomato plants nor does it provide extra nutrient to the plants as a result of radiation. It does, therefore, provide the plant physiologist with a medium for the study of uptake of inorganic nutrients by sterile plants which possesses all the purely chemical and structural features of natural soil.
Some Studies of the Autotransformation of H‐Bentonite to Al‐Bentonite
Authors: Davis L. E. , Turner R. , Whittig L. D.
Published: July 2010

Duplicate samples of suspensions of H‐bentonite prepared by the method of Aldrich and Buchanan (1) were heated at 35°, 50°, 65°, 80° and 95°C. At appropriate time intervals, samples were removed, cooled to 25°C., and titrated electrometrically with NaOH solution. The titration curves were markedly differentiated functions of time and temperature of heating.

Specimens heated for various periods at 95°C. were analyzed for the amount of replaceable Al and examined by X‐ray diffraction analysis. Replaceable Al increased progressively with time of heating. X‐ray diffraction analysis revealed that basal spacings and intensity of diffraction maxima increased with time of heating. The authors conclude that these changes are related to increase in the ratio of replaceable Al to H.
Relative Value of Calcium Metaphosphate and Superphosphate as Sources of Phosphorus for Plants on Different Soils
Authors: Allmaras R. R. , Black C. A.
Published: July 2010

Availability‐coefficient ratios (ACR) of phosphorus in calcium metaphosphate (CMP) to phosphorus in concentrated superphosphate (CSP) applied to 11 soils were obtained from data on yields of phosphorus in plants in a greenhouse experiment. ACR values ranged from 0.61 to 1.25 and were lower for calcareous than for acid soils. The best index of ACR values was provided by the increase in orthophosphate in the soils as a result of addition of CMP and partial hydrolysis of the condensed phosphate it contains. The increase in orthophosphate was estimated by (a) adding different quantities of P as KH2PO4 to soil, (b) incubating the soil under the same conditions employed for CMP, (c) finding the increase in orthophosphate by isotopic dilution of P32O4 in the presence of (CH3)4N‐resin, (d) plotting the observed increases in orthophosphate against the quantities of P added as KH2PO4, and (e) finding by interpolation in the plot of (d) the quantity of P added as KH2PO4 to which the observed increase in orthophosphate with CMP was equivalent. The relative increases in orthophosphate present in water extracts of the soils as a result of application of CMP or CSP provided a good index of ACR values in most soils but not in all. The gross movement of P from CMP into surrounding soil provided a relatively poor index of the ACR values. The results indicate that in soils treated with CMP, the P absorbed by plants comes mainly from the orthophosphate and not directly from the condensed phosphates.
Soils of Indian Mounds in Northeastern Iowa as Benchmarks for Studies of Soil Genesis
Authors: Parsons R. B. , Scholtes W. H. , Riecken F. F.
Published: July 2010

A study was made to evaluate the degree of horizon development in seven prehistoric Indian mounds of known age in northeastern Iowa. Comparisons were made between the data obtained for the Indian mound soil profiles and two virgin, loess‐derived Fayette profiles from the landscape near the mounds. The parent materials for the mound soils were the leached upper horizons of the soils under and immediately adjacent to the mounds.

Morphologically, the mound profiles exhibited pronounced A1 horizons, weak color and structural A2 horizons, and incipient B horizons. Differences in profile development among the mounds were attributed to differences in mound age. The development of soil profiles in the mounds has been the most pronounced during the first 1,000 years. The mounds have reached their greatest present horizon expression in a period of no more than 2,500 years, and are similar in many respects to the Fayette soils which have developed over a period of no more than 14,000 years.
Moisture Storage and Use by Dryland Spring Wheat Cropping Systems
Authors: Haas H. J. , Willis W. O.
Published: July 2010

Soil moisture data collected at Mandan, North Dakota from 1915 to 1954 were summarized to compare water storage and use from soil annually cropped to spring wheat and alternately fallowed and cropped to spring wheat. Consecutive 2‐year periods were used for the comparisons. The periods of study began with time of harvest.

Water storage was similar for both systems from harvest to June 1 of the first year. Eighty‐four percent of the water stored during an entire fallow period had accumulated by July 1. Conservation of water over the second winter of fallow averaged only 0.02 inch. For the same period of time, the annually cropped soil conserved 1.67 inches. During an entire fallow period (about 21 months) only 4.36 inches of a possible 22.73 inches were stored. For the same period, an annually cropped soil stored 2.60 inches.

Only 4 more inches of water was used by the annual cropping system in producing a wheat crop averaging 15 bushels per acre than was used during the same period by fallow where a crop had not been grown.
Numerical Method for Solving the Diffusion Equation: I. Horizontal Flow in Semi‐Infinite Media
Authors: Ashcroft Gaylen , Marsh Donald D. , Evans D. D. , Boersma Larry
Published: July 2010

The diffusion equation has been successfully used by several investigators to describe moisture movement in soil. Their success depends largely upon the Boltzmann transformation which can only be used for semi‐infinite, uniform regions.

A numerical technique is developed for solving the implicit difference analogues of the diffusion equation. This method involves (1) devising suitable difference analogues for the differential equation, (2) developing a method for choosing diffusivity to convert the nonlinear difference analogues into linear equations, and (3) solving the system of linear equations.

The numerical method can be applied to finite, nonuniform media. However, the study reported is limited to one‐dimensional, horizontal flow in a uniform, semi‐infinite medium so that the solutions obtained can be compared to solutions obtained by the Boltzmann transform technique. The results of the study indicate that the numerical methods and the Boltzmann transform techniques give very similar solutions and that solutions obtained by both methods are similar to experimental results.
Effect of Iron Removal and Dispersion Methods on Clay Mineral Identification by X‐Ray Diffraction
Authors: Harward M. E. , Theisen A. A. , Evans D. D.
Published: July 2010

The clay minerals identified in soil samples were found to be dependent on the pretreatment of samples for iron removal and dispersion. Treatments affected the characterization for chlorite, montmorillonite‐type minerals, vermiculite, and intergrade components. Increases in the degree of expansion upon solvation and in degree of collapse upon K‐saturation and heating were related to the severity of treatments used for dispersion. Iron removal treatments also increased the ease of expansion and collapse to 2:1 lattice clays. It was concluded that certain pretreatments tended to remove interlayered materials which were present in these samples.

The degree to which clay mineral interpretation was affected by methods of pretreatment was not the same for all soils. Samples of the Astoria soil exhibited the greatest differences in diffraction patterns as a result of dispersion and Fe removal treatments while the Aiken was the least affected. The Willamette was found to be intermediate. The evidence suggested that the Astoria samples contained interlayer materials (intergrade components) which were poorly crystallized and thus more labile and subject to removal. On the other hand, the interlayer material in the Aiken seemed to be better crystallized and more toward the chlorite end of the spectrum.

It has sometimes been assumed that the methods which permit the identification of the largest number of components with “clean‐sharp” peaks are the ones which should be used in sample preparation. It is suggested that the objective should be to obtain methods which permit the identification and reflect the properties of clay minerals as they existed in situ.
Comparing Measurements of the Effect of Residual Fertilizer Phosphorus in Some Iowa Soils
Authors: Smith Charles M. , Pesek John T.
Published: July 2010

The accuracy of the chemical soil test (0.03N NH4F in 0.025N HCl) for predicting biological response to residual fertilizer P was determined for several Iowa soils. Significant correlations were obtained with various measurements in the field and greenhouse, including grain, total dry matter, yield of P and radioactively determined A values.

Soil test P was the most highly correlated with greenhouse A values and the relationship was essentially linear over the range of levels of residual P. One regression line described this relationship for all neutral and acid soils tested but was different from that for a calcareous (pH 8.0) soil. The soil test predicted the A values equally well regardless of whether the fertilizer P had been applied 1, 2, or 3 years previously.
Heats of Desorption of Ammonia and Simple Organic Materials from Bentonite
Authors: Ellis Boyd G. , Mortland M. M.
Published: July 2010

The differential thermal analysis apparatus was used as a means of determining the heats of desorption of NH3, methylamine, and ethylamine from bentonite clay. A method was developed using nitrogen gas to prevent oxidation of the sample during analysis. The average heat of desorption of NH3 and methylamine for the temperature range of 200° to 450°C. was found to be 35.3 and 40.9 kcal. per mole, respectively. In each case the desorption was accompanied by loss of equal moles of water. It is postulated that the water loss arises from decomposition of Al(OH)3. The average heat of desorption of ethylamine for the same temperature range was 157 kcal. per mole; however, the simultaneous loss of large quantities of water accounted for most of the heat change.
High Frequency Titrimetry of Soils and Clays: Methodology, Theory, and Nature of the Ba‐Mg Exchange Reaction
Authors: Simonson Clifford H. , Axley John H.
Published: July 2010

A highly sensitive method for studying cation‐exchange phenomena was developed. A high frequency titrimeter, sensitive to about 0.0002 me., was used along with a continuous‐delivery buret of precision ±0.0003 ml. Soil or clay samples of 0.5 to 2.0 g. (much less can be used) were first saturated with Na, then converted to Ba‐saturation, and finally titrated in semiaqueous media with standard sulfate solution.

The apparent dissociation of Ba from exchange sites is indicated by comparisons with titration curves for strongly dissociated (BaCl2) and weakly dissociated (Ba‐(OAc)2) salts. For many soils and clays, four general stages or regions of the curve can be differentiated. These appear to represent loose bonding, moderate bonding, moderately strong bonding, and very strong bonding. The bonding characteristics of exchangeable Ba are further illustrated by curves of a few selected soils and reference clays. These curves also demonstrate: (1) similarities in clay‐mineral behavior between specific soil samples and reference clays; (2) differences between reference clays in the same group; and (3) differences between arable soils and those developed in hydromorphic environments.
Extractable Aluminum in Some Hawaiian Soils
Authors: Plucknett D. L. , Sherman G. D.
Published: July 2010

Extractable Al was measured in 5 Hawaiian soils from Kauai at four 3‐month intervals. A relationship between extractable Al and rainfall was observed. Highest extractable Al was measured during high rainfall periods (winter) and lowest extractable Al was measured during low rainfall periods (summer). High extractable Al was also observed in the poorly drained Koolau soil. Low extractable Al during summer months could be the result of inactivation of Al on cation‐exchange sites due to dehydration. The method used for extractable Al in this study probably measured both “exchangeable” and “soluble” Al. Plant Al analysis indicated not all extractable Al measured was available to the plant. In subsoils treated with lime, extractable Al decreased with increased pH. Lower extractable Al due to P treatment was interpreted as inactivation of Al as the latter reacted with the phosphate.
Inability of the Kjeldahl Method to Fully Measure Indigenous Fixed Ammonium in Some Soils
Authors: Stewart B. A. , Porter L. K.
Published: July 2010

In the course of some N fractionation studies in soils, inconsistencies resulted between the summation of the N fractions and the total soil N. In some, but not all, soils the summation figure exceeded by 25% the Kjeldahl figure. This inconsistency was especially noted in one soil that contained as much as 55% of the total N as indigenous fixed ammonium. A question was thus raised about the accuracy of the Kjeldahl procedure to measure indigenous, clay‐fixed ammonium.

When soils were treated with HF before Kjeldahl analyses, the difference between the summation figures and the modified Kjeldahl results was < 5%. These results leave little doubt that on soils which contained from 11 to 55% of the total N as fixed ammonium the HF pretreatment increased the total N recovered.
The Fate of Applied Phosphorus in Four Ohio Soils
Authors: Volk Veril V. , McLean E. O.
Published: July 2010

Four acid soils were selected on the basis of the level of available P and the magnitude of P fixing capacity (ability to retain soluble P against Bray P1 extracting solution). Water‐soluble P labeled with P32 was applied at the rate of 3.4, 29.2, and 106 pp2m. parts of soil with and without additions of lime. The availability of the soil P to oats in the greenhouse was computed by the methods of Fried and Dean (also Larsen and Sokolov) and of Murdock and Engelbert. Fractionation of the phosphate compounds formed in the soil was also made by the method of Chang and Jackson.

Both the initial level of available P and the P fixing capacity were found to be important in determining the amount of plant response to applied P. A value indexes of available P generally increased with rate of application of P and lime. The application of soluble P to soils high in P fixing capacity decreased the availability (Bray P1 extractability) of the native P, while the added P tended to increase the availability of the native P in the low fixing soils. Almost all of the applied P was recovered in the Al and Fe phosphate components. There was a tendency for recovery of more than half of the applied P as FePO4 in the soils of high P fixing capacity and more than half as AlPO4 in those of low fixing capacity.
Residual Effects of Phosphorus Fertilizer in an Irrigated Rotation in the Southwest
Authors: Leamer Ross W.
Published: July 2010

Response to phosphorus fertilizer on a phosphorus‐deficient Reddish‐Brown soil was measured through 8 years. Yields, percent P in plant, and NaHCO3‐extractable soil P were followed through 2 cycles of alfalfa and 2 intervening crops of sorghum. Increased yields were obtained until P equal to the application was removed in harvested crops. Alfalfa yields were closely correlated with both percent P in hay and NaHCO3‐extractable soil P during the first 4 years. High yields were maintained in the second cycle of the rotation, but percent P in hay and NaHCO3‐extractable soil P were at levels associated with low yields during the first cycle. Sorghum following alfalfa was not affected by N fertilizer. Second‐year sorghum benefited from N only where there was ample P.
The Effect of Nitrogen Fertilization on the Concentration and Weight of Nitrogen, Phosphorus, and Potassium in Douglas‐Fir Trees
Authors: Heilman Paul E. , Gessel S. P.
Published: July 2010

Analyses were made of composite samples of needles, live branches, dead branches, bark and wood of 70 Douglas‐fir trees taken from five areas and ranging in age from 30 to 50 years. The fertilized trees were from plots that had been fertilized at rates of 200, 300, 500 and 660 pounds of elemental nitrogen per acre.

The data show increased concentration of nitrogen and decreased concentration of phosphorus and potassium in the foliage, as a result of nitrogen fertilization. The nitrogen concentration of other components was also increased, but the concentration of phosphorus and potassium in these tissues did not demonstrate dilution effects that were observed in the needles. The nitrogen:phosphorus ratio in the foliage showed promise for use in diagnosis of nitrogen deficiency of Douglas‐fir by foliar analysis.

The data on total weight of nutrients in the trees on an area basis show that almost twice as much nitrogen, greater quantities of potassium and approximately equal amounts of phosphorus were contained in the vegetation on certain fertilized plots as were contained in the unfertilized vegetation. Needles showed the greatest increase in nitrogen, with branches and bark showing lesser increases, and wood no increase.
Measurements of Capillary Conductivity for a Taiwan Latosol and Alluvial Soils
Authors: Shyr‐yaung Lin , Tsen‐tuo Chen
Published: July 2010

The capillary conductivities of natural cores and sieved samples of Taiwan latosol have been determined and compared with those of alluvial soils. Calculations were made from pressure plate outflow data at 0.06‐ to 0.10‐, 0.10‐ to 0.20‐, 0.20‐ to 0.33‐, and 0.33‐ to 0.50‐atm. ranges by the methods of Gardner, and of Miller‐Elrick which was extended for non‐negligible plate impedance. In the case of non‐negligible plate impedance, the Gardner method met limitation, and the Miller‐Elrich method was preferable. At low moisture tension, the capillary conductivity of the clayey latosol was similar to that of sandy soils. It seems that no generalization is yet possible about the influence of soil texture upon capillary conductivity.
Some Principles of Chelation Chemistry
Authors: Lehman D. S.
Published: July 2010

There are various factors which contribute to the stability of a metal chelate. The number of rings formed by one molecule of chelating agent with the metal ion, the size of the rings, and the nature of the donor atoms are of prime importance. Also to be considered are the effects of resonance stabilization and steric relationships. Thermodynamic data shows that a favorable increase in entropy often makes a significant contribution to the stability of a chelate. In addition the environment, for example, the pH, plays an important role in chelation reactions.
Miscible Displacement in Saturated and Unsaturated Sandstone
Authors: Corey John C. , Nielsen D. R. , Biggar J. W.
Published: July 2010

A description of soil water movement is more complete if the nature of the pore structure is known. Miscible displacement techniques were used to investigate the nature of the pore structure of a sandstone. The mixing of a 75‐ml. slug of tritiated CaCl2 solution during displacement through 5 lengths of sandstone was measured. Different velocities and different degrees of water saturation were involved. Limited mixing by molecular diffusion for the various experimental conditions clearly revealed the lack of interconnection between major pore sequences. This pore structure differs markedly from that of soils or other unconsolidated porous materials.
Multilayer Adsorption of Water by Kaolinite
Authors: Jurinak J. J.
Published: July 2010

The Frenkel‐Halsey‐Hill isotherm equation for multilayer adsorption was applied to water adsorption by various monoionic kaolinites at 10.0°C. The FHH Equation described water adsorption over a wide P/P0 range in all systems. Li‐kaolinite showed no evidence of ion hydration or capillary condensation up to P/Po = 0.972 and was used to calculate free water adsorption in terms of statistical layers, n. The calculated multilayer adsorption isotherm for water was identical for Li‐, Ca‐, Ba‐, and Al‐kaolinites. The same isotherm also described water adsorption by Na‐kaolinites up to P/Po = 0.9 where ion hydration was initiated. A definite effect on the parameters of the FHH equation was found as the nature of the substrate surface was varied when water is used as the adsorbate.
Immobilization and Mineralization of Nitrogen in Several Organic Fractions of Soil
Authors: Stewart B. A. , Porter L. K. , Johnson D. D.
Published: July 2010

Straw and N fertilizers were incubated in soil and changes in content of some organic N fractions were measured. Ammonia and nitrate N, as well as the N in several organic fractions, were determined to detect changes in the organic fractions which could be related to increases or decreases in the inorganic N.

Most of the N immobilized during incubation with soil and straw was found in the nondistillable acid‐soluble N fraction of the hydrolysate. Although the nondistillable acid‐soluble N fraction constituted only about one‐half of the total organic N, studies using N15 showed that about about three times as much fertilizer N went into this fraction during immobilization as went into the distillable acid‐soluble and acid‐insoluble N fractions combined.
Oxygen‐18 as a Tracer in Soil Aeration Studies
Authors: Jensen C. R. , Kirkham Don
Published: July 2010

This paper describes a procedure for use of O18 in soil aeration tracer studies. Atmolysis, isotopic exchange, and respiratory fractionation produce only small errors when using O16O18 as a tracer for O2 diffusing in soil under steady state conditions. A special train for producing equal, continuous streams of O18‐enriched and unenriched air was developed. Analyses of experimental samples of oxygen were performed with a mass spectrometer. A split canopy experiment is described in which the effects of different surface conditions on the soil oxygen supply may be compared; in this case, the presence and absence of corn seedlings were compared. Results are expressed in terms of the mixing ratio of air from the two halves of the canopy. Improvements and possibilities of the method are discussed.
Effect of Exchangeable Potassium Level and Drying upon Availability of Potassium to Plants
Authors: Dowdy R. H. , Hutcheson T. B.
Published: July 2010

Successive croppings of Sudangrass showed that K uptake by plants was greater from soil samples that released K upon drying than from comparable continuously moist samples. For soils originally low in exchangeable K, more K was released from continuously moist samples than from similar samples which had been air‐dried prior to cropping. This was considered a response to increased stress by the plants upon the K equilibrium, because of less readily available K in the continuously moist samples.

Potassium uptake data, reductions in exchangeable K levels, and K‐release patterns strongly suggested that added K fixed by drying was available for plant use. Crop yields were the same for both moist and air‐dried soil samples at high levels of exchangeable K; but, yield data did reflect K released by drying samples initially low in exchangeable K.
Ammonium Influences on Rubidium Absorption and Distribution by Tobacco Seedlings
Authors: Skogley E. O. , McCants C. B.
Published: July 2010

Mechanisms whereby NH4 influences the accumulation of cations in tobacco were investigated using short‐term solution studies with Rb86. Measurements on the influence of seedling size and absence of tops on the accumulation of Rb in roots indicated that the size of the plant was positively correlated with Rb accumulation only to the extent of 0.7. During a 6‐hour period roots had the major influence on Rb accumulation, the absence of tops making little or no difference. During this absorption period it was found that NH4 had the same influence as K on the absorption of Rb, while after 24 to 48 hours NH4, relative to K, had an additional depressive influence on Rb accumulation, especially in the tops of seedlings. The possible involvement of NH4 influences on transpiration rate and associated passive ion transport was investigated. No NH4 influence on transpiration was found during periods extending to 70 hours. Salt treatments subsequent to Rb86 treatments indicated that the distribution of Rb was dependent more on conditions during its absorption than on those imposed later. Results from these and other studies are used to develop a mechanism for Rb absorption and distribution by tobacco seedlings which accounts for the observed influences of NH4 on Rb accumulation through an effect on absorption competition and metabolic ion transport.
Yield and Nutrient Composition of Tomatoes in Relation to Soil Temperature, Moisture, and Phosphorus Levels
Authors: Cannell Glen H. , Bingham F. T. , Lingle J. C. , Garber M. J.
Published: July 2010

Tomato plant growth was determined for 4 soil temperatures in combination with 2 soil moisture conditions and 3 phosphorus levels. There was a curvilinear relationship between yield and temperature. The highest yields were at 68°F., low soil suction, and high phosphorus. Yields increased with decreasing soil suction and with increasing phosphorus. Chemical leaf analysis, with exception of Mg, showed Ca, K, P, N, Cu, Fe, Mn, and Zn to vary significantly with temperature changes. Ca, Mg, K, N, Mn, and Zn were increased with decreasing soil moisture. Ca, Mg, K, P, N, and Mn tended to decrease with higher rates of phosphorus.
The Management of Soil Salinity in Lysimeters
Authors: Williamson R. E.
Published: July 2010

Soil salinity quickly became a problem in sheltered lysimeters used for studies of the drainage requirements of crops in North Carolina. Water tables were maintained by subsurface watering at depths of 6 to 40 inches below the soil surface in 3‐foot‐square lysimeters, with some sheltered from rainfall and others exposed to rainfall. All were exposed alike to other atmospheric conditions. Very high levels of P, K, and Ca were established in the soil by mixing 0‐20‐0, muriate of potash, and lime with the soil placed into each tank.

Soybean plants exhibited chlorosis and stunted growth in the lysimeters with subsurface watering only. These symptoms were serious approximately 1 month after the establishment of water tables only 6 inches beneath the surface, but were less pronounced with the deeper water tables. They were not observed where rain fell on the soil.

At any water table depth, the plant growth and yield were best on the lysimeters that were leached with rainfall. Plant growth increased with depth to water table to a depth of 24 inches, both with and without rain on the soil.

After soybean harvest in 1959, the electrical conductivity of the saturation extract from the soil in the top 6 inches of all lysimeters was 4 to 5 millimhos where subsurface watering only was used, and 0.4 millimho where rain fell on the soil.

Lower fertilizer applications and leaching with small amounts of water kept the soil salinity in the upper 6‐inches at a low level in subsequent years. Crops of soybeans, cabbage, corn, grain sorghum, and string beans were produced successfully both in the lysimeters sheltered from rain and in those exposed to rain.
Soil‐Erodibility Evaluations for Soils on the Runoff and Erosion Stations
Authors: Olson Tamlin C. , Wischmeier W. H.
Published: July 2010

The universal soil‐loss estimating equation introduced by Wischmeier is:

A = R K L S C P

where A is estimated soil loss, R is the rainfall‐erosion index, K is the soil‐erodibility factor, and L, S, C, P are factors for length and percent slope, cover, and mechanical conservation practices, respectively.

The soil‐erodibility factor (K) is defined as the average soil loss per unit of the erosion index (R) from continuous fallow on a plot 72.6 feet long on a 9% slope. The value of this factor was approximated for 20 soil types represented on the U. S. Department of Agriculture runoff and erosion research stations located in the eastern half of the United States.

The estimated values were computed from the plot data, using those plots whose conditions most closely approximated base conditions of cover and geometry. Observed soil losses from cropped plots were adjusted to fallow conditions by use of previously published numerical values of C and P.

The resulting table of K values provides a list of bench‐mark values for estimating the erodibility of other soils.
Ion Sorption by Soil Separates and Exchange Equilibria Involving Sodium, Potassium, and Rubidium
Authors: le Roux F. H. , Coleman N. T.
Published: July 2010

Sodium‐potassium exchange reactions were studied with four California soils, utilizing chromatographic and equilibrium procedures. Apparent exchange constants varied with ion saturation and indicated a larger affinity for potassium as its equivalent fraction on exchange sites decreased. This was especially true for soils containing biotite‐hydrobiotite‐vermiculite in the coarse fractions. Clay and silt‐size materials from such a soil were packed into columns, and the sorption‐desorption behavior of rubidium was measured using the radioisotope Rb86. Irreversible sorption of rubidium with corresponding reductions in cation‐exchange capacity was large for silt, intermediate for coarse clay, and negligible for fine clay. Sodium‐rubidium exchange isotherms obtained for various size fractions both before and after a portion of the exchange‐capacity was “blocked” with Rb or K indicated a quite specific sorption of Rb on certain sites, with “normal” ion‐exchange behavior for the remainder of the CEC. X‐ray diffraction studies suggested specific sorption of K and Rb by vermiculite and hydrobiotite, irrespective of the Na/K or Na/Rb ratio in saturating solutions. However, even when sites with specific affinity for Rb or K were eliminated, there was significant variation in the apparent exchange constants obtained for different soils. For soil containing vermiculite in the coarse fractions, the specific sorption of radiorubidium may be a conveniently determined guide to potassium fertilizer needs.
Gibbsite Formation From Aluminum‐Interlayers in Montmorillonite
Authors: Barnhisel R. I. , Rich C. I.
Published: July 2010

Gibbsite crystallized from hydroxy‐Al which previously had been precipitated on the interlayer surfaces of the 2 to 0.2µ fraction of montmorillonite. Hydroxy‐Al interlayers were prepared with OH/Al molar ratios of 0.38, 0.75, 1.50, 2.25, and 3.00 and were aged 1, 3, and 6 months. In the samples that were not aged, the CEC decreased from 78 to 2 me. per 100 g. as the OH/Al molar ratio increased. In addition, the basal spacing increased from 10.2 to 14.7Å. (K‐saturated, 300°C.) as the OH/Al molar ratio increased.

X‐ray diffraction, thermo‐gravimetric, and differential thermal analysis studies indicated that the hydroxy‐Al interlayers formed with OH/Al molar ratios of 0.38, 0.75, and 1.50 were stable when aged 6 months; whereas, samples with OH/Al molar ratios of 2.25 and 3.00 were not. Gibbsite formed after 1 month in the sample with an OH/Al ratio of 3.00 and after 3 months in the sample with an OH/Al ratio of 2.25, and the amount of gibbsite increased with time. Gibbsite formed in the presence of montmorillonite at a pH of < 4.3. After the Al‐interlayers were removed through gibbsite formation, the montmorillonite regained its cation‐exchange capacity. The crystallization of gibbsite from Al‐interlayers may be one mechanism for the formation of this mineral in some acid soils.
Effect of Anions on Amount of Sodium Adsorbed by Sodium‐Saturated Utah Bentonite
Authors: Sommerfeldt Theron G. , Peterson H. B.
Published: July 2010

Sodium‐saturated Utah bentonite was equilibrated in various concentrations and kinds of sodium salt solutions to ascertain the effects of different anions in the system on the amount of sodium adsorbed by the clay. Effects of pH on the adsorption of sodium were also studied by equilibrating the clay in solutions having pH's of 7.2 and 10.5. The solutions were analyzed before and after equilibration to determine their changes in ion concentrations and pH. Soluble silicon was determined in both the equilibrate and the cation extraction solutions.

The clay proved sensitive to its anion environment. The amount of sodium adsorbed by the clay and the concentration of the soluble silicon in the equilibrate varied with the anion present. Increased concentration of anion generally increased the anion effect. After equilibration in solutions having an ionic strength of 1.0, the amount of sodium adsorbed was 66, 68, 76, 77, 94, and 115 me. per 100 g. of clay when the anions were bromide, iodide, chloride, sulfate, bicarbonate, and hydroxide, respectively. A correlation existed between the final pH and the amount of sodium adsorbed; generally the amount adsorbed increased with pH. A correlation also was evident between the amount of soluble silicon and final pH.
The Release of Fixed Ammonium from Soils by Sodium as Affected by Small Amounts of Potassium or Ammonium
Authors: Leggett G. E. , Moodie C. D.
Published: July 2010

The release of fixed NH4 from soils by Na was studied. Data are presented to show that when no K was added to NH4‐saturated air‐dried soils, 86 to 98% of the fixed NH4 was released during alkaline aeration or distillation. When small amounts of K were added to the alkalizing agents, the release was markedly decreased. When the K/Na ratio of the alkalizing agents was increased to 0.005, only 14 to 35% of the fixed NH4 was released. Similar effects were noted when small amounts of NH4 were allowed to accumulate in the system during equilibration of NH4‐saturated soils in various volumes and concentrations of NaCl solutions.

The rate of release of fixed NH4 was studied by aerating NH4‐saturated soils in the presence of Na2CO3 solution. The data obtained indicate that release is slow, even under conditions which favor removal of the released NH4 from the system. A linear relationship was obtained when the logarithm of rate of release was plotted against time. Thus, it was concluded that the release of fixed NH4 was similar to the release of fixed K from vermiculite and the later stages of K release from biotite noted by others.
The Availability of Fertilizer Nitrogen Immobilized During Decomposition of Straw
Authors: Stewart B. A. , Johnson D. D. , Porter L. K.
Published: July 2010

A greenhouse study measured the extent to which fertilizer N15 immobilized during decomposition of straw becomes available for plants. Less than one‐half of the immobilized fertilizer N15 was released for plant uptake during four successive croppings in the greenhouse. The crops were beets, barley, and two of corn.

Fractionation of the soil N showed that about 75% of the N taken up by the plants was derived from the nondistillable acid‐soluble N fraction. Fertilizer N15 immobilized in this fraction was utilized at a faster rate by plants than the N initially present in this fraction.
Sequence of Products Formed During Denitrification in Some Diverse Western Soils
Authors: Cooper Grant S. , Smith R. L.
Published: July 2010

The sequential products of anaerobic denitrification were determined on seven Western soils (four alkaline, two acid, and one neutral) by soil and gas analysis. The soils with 1% alfalfa and added KNO3 were incubated at moistures slightly greater than field capacity and with an atmosphere of He. The soils and gases were periodically analyzed and balance sheets prepared. The sequence of NO3‐ → NO2‐ → N2O → N2 operated in all soils. The N2O and N2 were determined on a gas chromatograph. The rates of nitrogen interchanges and maximal amounts of nitrite, N2O, and N2 were determined. From this data it was postulated that the rate‐limiting process for denitrification in acid soils is the reduction of nitrate, while in alkaline soils it is the reduction of nitrite. The reduction of N2O was rapid in all instances. The total time for complete reduction of 300 ppm. N as nitrate to N2 at 30°C. varied only from 28 to 96 hours for the 7 soils. Lowering the temperature to 25° or 20°C. influenced all rates for 3 alkaline soils and resulted in a twofold increase in denitrification time for the 10°C. drop. Decreases in initial concentration of added KNO3 to 150, 75, and 37.5 ppm. did not change the overall rate of dentrification. There was, however, a marked reduction in the maximal amounts of N2O found in the gaseous atmosphere when the initial KNO3 concentration was reduced.
Influence of Salts on Ammonium Oxidation and Carbon Dioxide Evolution from Soil
Authors: Johnson D. D. , Guenzi W. D.
Published: July 2010

Osmotic tension was found to reduce nitrate production and CO2 evolution from soil in a linear manner. This is essentially the result which would have been predicted using principles derived from studies on the influence of salts on the growth of higher plants. Nitrification showed the influence of individual salt species, with NaCl being the most toxic. Total microbial activity, as measured by CO2 evolution is much more tolerant of osmotic stress and shows no definite individual salt effects.
The Effects of Nitrogen on Short‐Term Phosphorus Absorption and Translocation in Corn (Zea Mays)
Authors: Cole C. V. , Grunes D. L. , Porter L. K. , Olsen S. R.
Published: July 2010

Short‐term P uptake studies were conducted with intact 1‐month‐old corn plants of differential N and P composition. Supplemental N pretreatments producing increased growth rates and higher levels of N in the plant stimulated the rate of P uptake per unit dry weight of root more than did a tenfold increase in P concentration in the external solution. Nitrogen pretreatments caused five‐ to tenfold increases in rate of P translocation to the tops during the uptake period. The presence of nitrate or ammonium ions in the test solution during the uptake period had negligible effects on P uptake rates. Phosphorus uptake rates were highly correlated with total N level in the roots. The stimulation of P uptake rates with higher plant N levels suggests a connection between N metabolism and P uptake processes.
Physical Characteristics of Four Mississippi Soils
Authors: Andrew L. E. , Stearns F. W.
Published: July 2010

Four silt loam soils in Warren County, Mississippi, were studied intensively to determine to what extent a soil series, as normally mapped by types, delimits the physical properties of the surface foot.

The degree of variation between individual samples implied that intensive sampling is necessary to typify physical properties of these soils. Means differed significantly between series in clay content, bulk density, and moisture‐tension values. However, the range in values suggests that, for strength classification and simliar purposes depending upon physical properties, similar textural types in different series can often be combined.

Memphis and Loring, designated upland soils, had considerably more clay than the bottom‐land soils Falaya and Collins. As a result of erosion, variation in clay content in the plow layer was far greater in upland than in bottom‐land soils.
Soil Variability—A Serious Problem in Soil‐Site Studies in the Northeast
Authors: Mader Donald L.
Published: July 2010

The degree of variability and its effect on accuracy of mean plot values for soil properties is an important problem needing evaluation for soil‐site studies in the Northeast. This paper discusses the variability in soils sampled in a red pine plantation site study. Two profiles were sampled by horizon on each plot. Data are presented on the following soil properties: organic matter, N, silt and clay, exchangeable Ca plus Mg, cation‐exchange capacity, and bulk density. Variability between plots was much greater than within plots. Some soil properties required a large number of samples for accurate estimation, others a small number. Variation did not differ greatly from A to B horizons.
Site Evaluation Studies in Red Pine Plantations in Michigan
Authors: van Eck W. A. , Whiteside E. P.
Published: July 2010

Soil productivity for planted red pine in lower Michigan was evaluated for 27 soil series in terms of dominant tree height at age 50 by aid of local site curves developed from actual growth measurements.

In the presence of soil factors favoring adequate soil moisture supply and in the absence of soil factors which limited effective soil depth, the site index and growth rate of red pine was found to be rather uniform for many coarse‐ and moderately coarse‐textured soils.

The inadequacy of a single set of site curves for the prediction of site productivity is discussed and separate sets of curves are presented for soils causing growth patterns deviating from the normal trend.

The observed variations in height growth are associated with even greater relative differences in volume of wood produced. While variations in the quality of the wood products are also important in evaluating the productivity of forest sites, this aspect was not covered in the present study.
The Influence of Crop Environment on the Internal Water Balance of Cotton
Authors: Namken L. N.
Published: July 2010

The relative turgidity of cotton plants subjected to three soil moisture levels was related to soil moisture content, air temperature, pan evaporation, vapor pressure deficit, and air movement. A multiple regression equation that contained only those variables significant at the 1% level of probability was developed. The influences of vapor pressure deficit and air movement were not significant at the 1% level. Soil moisture, ambient temperature, and pan evaporation accounted for 87.5% of the variation in the relative turgidity of cotton leaves. Soil moisture alone accounted for 70.9% of the variation with a reduction to 44.3% upon discounting the effects of ambient temperature and pan evaporation. Ambient temperature and pan evaporation accounted for 43.1% of the variation with a reduction to 16.5% upon discounting the effect of soil moisture. The results demonstrate the relative importance of soil moisture and atmospheric conditions in regulating the internal water balance of plants.
Comparative Studies of Actinomycete Populations in Acid Podzolic and Neutral Mull Forest Soils
Authors: Corke C. T. , Chase F. E.
Published: July 2010

A comparison has been made of the actinomycete populations of acid podzol and neutral mull soils under forest cover. In both soils, numbers decreased with depth though less rapidly than did the combined bacteria and fungi; consequently the actinomycetes were, proportionately, slightly more numerous in the lower mineral horizons. The actinomycetes in the podzol were more acid tolerant than those from the mull soils. Approximately two‐thirds of the isolates from the podzol grew at pH 4.5 and one‐third at pH 4.0. Of the isolates from the mulls, only one‐sixth were capable of growth at pH 4.5 and none grew at pH 4.0. Furthermore, the acidic environment restricted actinomycete development to from five to seven “species groups” of Streptomyces.
Soil Parameters for Evaluating Tillage Needs and Operations
Authors: Larson W. E.
Published: July 2010

Estimated critical limits of selected soil parameters for evaluating tillage requirements for corn in the water management (interrow) zone and seedling environment (row) zone are presented. Suggested parameters for corn in the western Cornbelt for the row zone include soil temperature, secondary aggregate size, bulk density and volume of the zone. For the interrow zone, the parameters include depression storage, plow layer storage, and/or surface mulch or surface microrelief. The research basis for the selection of the critical limits and soil parameters is discussed. This approach can be used to evaluate tillage needs for other crops.
Distribution Patterns of the Weld‐Rago Soil Association in Relation to Research Planning and Interpretation
Authors: Fly Claude L. , Romine Dale S.
Published: July 2010

This study is concerned with criteria for predicting applicability to other soils of research results obtained from key or benchmark soils. Soil‐water‐plant growth relations which affect yields under different levels of management were evaluated at Akron, Colo. Under 46 years of uniform management, wheat production levels varied from 73 to 120 among eight soil types identified in a 25‐acre test field formerly mapped as one soil type. Soil differences induced wider variations under uniform treatment than did different treatments on a single soil type. When the detail of delineation and characterization of soils is comparable to the detail of the research plot layout, existing research fields and plot data may be used to associate soil qualities with response to treatment. The reliability of application of research findings to other areas will depend on adequate characterization and evaluation of the soil in each plot.