bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Membrane Pore Size on the Measurement of Water Tension in Bentonite Suspensions
Authors: Banin Amos , Davey Brian G. , Low Philip F.
Published: July 2010

A pressure‐transducer tensiometer and a dynamic osmometer were used to measure water tensions and osmotic pressures, respectively, in clay‐water systems. The two methods of measurement produced the same results. Different membranes, having pore sizes ranging from 0.004µ to 0.8µ were used with the tensiometer. It was found that the measured water tension of a given system depended on the pore size of the membrane; as the pore size increased, the tension decreased. However, experience indicates that little or no turbidity appears in a solution when it is separated from a clay suspension by a membrane having pores as small as those of the present experiments. Therefore, the relationship between pore size and tension was not due to differences in membrane permeability to the clay particles. Nor was it due to differences in membrane permeability to dissolved solutes. Tests showed that no lasting tension developed when a NaCl solution or an extract of the clay were utilized in place of the clay suspensions. Two possible explanations were proposed, namely: (i) entrance of particles into the pores was all that was required to lower the reflection coefficient, and (ii) the gelation of the clay suspensions within the pores produced gels having particle densities and arrangements and, hence, permeabilities to dissolved solutes, that were dependent on the dimensions of these pores. It was pointed out that, regardless of the explanation, the existence of such a relationship between membrane pore size and measured water tension is noteworthy.
Theory and Application of Gas Chromatography in Soil Aeration Research
Authors: Tackett J. L.
Published: July 2010

Methods for the gas chromatographic analysis of soil atmosphere samples as well as the construction details of two devices for obtaining the samples are presented. Typical column materials, arrangements and operating conditions are reviewed. A new approach to the dual analysis of oxygen and carbon dioxide on the same sample using a stream splitter instead of a dual column valve is presented. Advantages of the stream splitter arrangement over the dual column valve arrangement include better zero control, faster analysis, and the lack of valve switching necessary during an analysis.
Soil Organic Matter and Nitrogen Changes During 24 Years of Dryland Wheat Tillage and Cropping Practices
Authors: Unger Paul W.
Published: July 2010

Soil organic matter and total nitrogen were determined after 24 years3 of growing dryland wheat (Triticum aestivum L.) under various tillage and cropping practices in the Southwestern Great Plains. The various tillage practices resulted in significant differences in soil organic matter content when a wheat‐fallow cropping system was used. Values were highest for delayed stubble‐mulch tillage. Differences in soil organic matter content due to tillage practices used were not significant where wheat was grown continuously, but values for continuous wheat were higher than those for wheat‐fallow for comparable tillage practices.

Soil total N content was significantly affected by the tillage practice used for the wheat‐fallow, but not the continuous wheat cropping system. Values for continuous wheat were higher than those for wheat‐fallow for comparable tillage treatments. Soil organic matter was closely related to soil total N.
Lithium‐Calcium Exchange Equilibria in Soils and Clays
Authors: Bair F. L. , Pratt P. F.
Published: July 2010

Cation‐exchange equilibria at pH 7 were determined for a number of soils and clays using Li adsorption ratios (LAR) of 0.2 to 20 (mmoles/liter)½. Data for montmorillonite and montmorillonitic soils gave linear relationships between exchangeable Li ratio (ELR), or ratio of exchangeable Li to exchangeable Ca, and LAR; similar slopes were obtained in all cases. However, relationships between ELR and LAR for kaolinite and kaolinitic soils were all curvilinear with a relatively high adsorption affinity for Li at low Li concentrations, indicating that this high affinity for Li existed only in a small fraction of the cation‐exchange capacity of these materials. Drying in a Li‐saturated form increased the affinity of kaolinite for Li but had only a small effect on montmorillonite.
Velocity‐Gradient Relationships for Steady‐State Unsaturated Flow of Water in Nonswelling Artificial Soils
Authors: Olson T. C. , Swartzendruber D.
Published: July 2010

The relationship between flow velocity and hydraulic gradient was studied for steady‐state unsaturated flow of water in horizontal columns of two nonswelling porous media, one a mixture of sand, ground silica, and kaolinite, and the other a mixture of sand and ground silica only. The flowing water contained 0.1% phenol to inhibit bacteria. Soil‐moisture tension was measured with three tensiometers positioned within the soil column. Gradients at different velocities could be determined at a single location. Tension changes were always from low to high, to eliminate hysteresis effects. This required the use of a graphical analysis to calculate corresponding values of velocity and gradient at a given constant tension.

In general, essential proportionality between flow velocity and tension gradient at given tension was found for both materials. Very slight greater‐than‐proportional tendencies were present in the sand‐silica‐kaolinite mixture, but were not consistently related to tension. In the sand‐silica mixture a less‐than‐proportional flow response was observed at low and intermediate tensions, but became proportional as the tension increased. Minimal pore‐volume saturations achieved were 0.74 for the sand‐silica‐kaolinite, and 0.65 for the sand‐silica.
Theoretical Analysis of Two‐Dimensional, Transient Flow of Water in Unsaturated and Partly Unsaturated Soils
Authors: Rubin J.
Published: July 2010

The Darcian flow‐equation for two‐dimensional, transient transfer of water in rectangular, unsaturated or partly unsaturated soil slabs was solved numerically with the aid of alternating‐directions, implicit difference methods. Two alternative processes were considered: predominantly horizontal infiltration and ditch‐drainage. The results obtained for the horizontal infiltration process indicate that it involves upward flow‐components which are due, primarily, to a gravity‐induced variation in hydraulic conductivity along the inflow face. These components may materially affect the course of infiltration, especially during its earlier stages. The drainage case results demonstrate that transient water flow within the unsaturated zone and the outflow from the seepage zone may significantly affect the progress of water‐table descent and the total outflow rates.
Influence of Water Flux and Porous Material on the Movement of Selected Herbicides
Authors: Davidson J. M. , Rieck C. E. , Santelmann P. W.
Published: July 2010

The rate at which two substituted urea herbicides move through a water‐saturated glass bead and uniformly packed soil column depends upon the water flux or average pore velocity. A 200‐ml slug of 0.01N CaSO4 solution containing either fluometuron (3‐(m‐trifluoromethylphenyl)‐1,1‐dimethylurea) or diuron (3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea) was introduced at one end of a 30‐cm long column at a specific flux and the herbicide displaced through a column with 0.01N CaSO4 at the same water flux. Effluent samples collected every 5‐ml show fluometuron and the chloride ion to mix in a similar manner at the two fluxes studied. Experimental and calculated effluent concentration distributions did not agree when fluometuron was retained by the porous material.
Nitrate Uptake and Reduction as Affected by Calcium and Potassium
Authors: Minotti P. L. , Williams Doris Craig , Jackson W. A.
Published: July 2010

Nitrate uptake patterns by nitrogen‐depleted wheat seedlings (Triticum vulgare var. Atlas 66) exhibited an initial lag phase which was lessened, but not completely overcome, by presence of solution Ca. Maintenance of a more rapid subsequent rate of nitrate uptake, which developed after the initial lag phase, depended upon presence of solution K. The rapid phase was enhanced when both Ca and K were present and was curtailed by shoot excision and by Ca deficiency. Sizeably larger amounts of nitrate were recovered in the shoots after 24 hours in KNO3 as compared to Ca(NO3)2, and with the former salt, smaller proportions of the absorbed nitrate were reduced. The data suggest a beneficial influence of Ca both on initial nitrate uptake by root tissue and on transport to shoots while a continual K supply was apparently beneficial in nitrate transport.
Nitrate‐Stimulated Uptake and Transport of Strontium and Other Cations
Authors: Jackson W. A. , Williams Doris Craig
Published: July 2010

Supplying nitrate to N‐depleted wheat seedlings (Triticum vulgare, var. Atlas 66) stimulated the uptake of both divalent (Sr, Mn, and Mg) and monovalent (Cs, Na, K) cations. Rapid nitrate uptake, and the lower ambient acidity resulting from it, appeared to be partially responsible for the increase in cation uptake. Nevertheless, pretreatments with nitrate exerted some stimulation in Sr and Cs uptake, indicating an additional action of nitrate after it had entered the tissues. Pretreatment with nitrate, as well as its presence during the Sr uptake period, increased transport of Sr to the shoots more than total uptake. Transport to shoots of previously absorbed Sr was enhanced by subsequent nitrate treatments, the amount transported being significantly greater with nitrate salts of Ca, Mg, and Na than with K or NH4.
Factors Important in the Calculation of Hydraulic Conductivity
Authors: Kunze R. J. , Uehara G. , Graham K.
Published: July 2010

The calculation of hydraulic conductivity by a modified Millington‐Quirk method with a matching factor gave conductivity values closely approximating experimentally measured values. The technique requires knowledge of the moisture characteristic and the saturated conductivity. A number of factors that affect the calculated values and improve the computational results were investigated. Calculated conductivity values decreased with an increasing number of pressure classes at low moisture contents. For all soils tested the calculated conductivities were less than the experimental values at the terminal point of the moisture characteristic. This discrepancy was partially corrected by a small change in the Millington‐Quirk equation, by extending the moisture characteristics to higher suction values, and by reducing the number of pressure classes to approximately 10. A matching factor, the ratio of measured over calculated saturated conductivity, was found necessary for obtaining the best fit of calculated and measured data. Two conductivity functions calculated separately from each moisture characteristic forming a hysteresis loop, converged as the hysteresis loop was translated to higher tensions. All computations were done by computer.
Soil‐Water Diffusivity Values Based Upon Time Dependent Soil‐Water Content Distributions
Authors: Cassel D. K. , Warrick A. W. , Nielsen D. R. , Biggar J. W.
Published: July 2010

A laboratory method based upon time dependent soil‐water content distributions is presented for calculating isothermal soilwater diffusivity values for soils at 5 to 15 volume percent water. The redistribution of water within sealed soil columns was monitored by gamma‐radiation attenuation at approximately 100 to 1,000 hour intervals over a period exceeding 3 months. Diffusivity values from numerical integration of the diffusion equation were obtained easily and compared favorably with those of previous investigators.
Rhizo‐Deposition of Organic Debris in Soil
Authors: Shamoot Saad , McDonald Lain , Bartholomew W. V.
Published: July 2010

Deposition of organic debris from or associated with plant roots during periods of active growth (Rhizo‐deposition) was measured by the use of carbon‐14. The measurements were made by growing plants from the seedling stage to near maturity in an atmosphere containing carbon‐14, harvesting the tops and roots and determining the tracer C residual in the soil. The magnitudes of rhizo‐deposition were directly related to the extent of root growth and ranged from 25 to 49 g residual organic debris for each 100 grains of harvested roots.
Inhibition of Nitrification in Bladen Grassland Soil
Authors: Brar S. S. , Giddens Joel
Published: July 2010

Low nitrification in Bladen grassland soil was not improved by extraction of possible toxic substances. Liming improved nitrification after a delay period. Addition of nitrifiers to a limed soil resulted in good nitrification. Nitrifiers developed in Bladen soil gave better nitrification in Bladen than nitrifiers from Cecil. The acid Bladen soils were very high in extractable aluminum. It was concluded that acidity and the resulting low population of nitrifiers was the cause of low nitrification in Bladen sod soil.
Zn‐Dust Distillation and Fusion of a Soil Humic and Fulvic Acid
Authors: Hansen E. H. , Schnitzer M.
Published: July 2010

A humic and a fulvic acid extracted from a Podzol Bh horizon were subjected to Zn‐dust distillation and fusion. The reaction products were first purified by vacuum‐sublimation and then separated by a combination of preparative thin‐layer chromatography on silica gel and on cellulose. Identification of each fraction was performed by ultraviolet spectroscopy and spectrophotofluorometry. The main products were polysubstituted naphthalene, substituted phenanthrene, and substituted and unsubstituted anthracene, pyrene and perylene. In addition, small amounts of the following polycyclic hydrocarbons were also identified: fluoranthene, 1,2‐benzofluorene, 2,3‐benzofluorene, 1,2‐benanthracene, 1,2‐benzopyrene, 3,4‐benzopyrene and naphtho‐(2′,3′:1,2)‐pyrene. Semi‐quantitative yields for individual polycyclic hydrocarbons were estimated. Our results point to the occurrence in the “nuclei” of soil humic compounds of significant amounts of polycyclic aromatic ring structures or structures yielding such systems under the experimental conditions employed.
Response of Several Corn Hybrids to Level of Water‐Soluble Zine in Fertilizers
Authors: Giordano P. M. , Mortvedt J. J.
Published: July 2010

Fertilizers varying in level of H2O‐soluble Zn were prepared by combining fine ZnO and ZnSO4 in various proportions and pressure‐granulating the powders with ammonium nitrate, monoammonium phosphate, or ammonium polyphosphate. Forage yields and uptake of Zn by corn (Zea mays L.) grown on a P‐ and Zn‐deficient soil in the greenhouse increased with the level of H2O‐soluble Zn in these macronutrient fertilizers. Additional crop response was slight to fertilizers with levels of H2O‐soluble Zn in excess of about 50% but this varied, depending upon the macronutrient carriers. However, the amounts of Zn extracted after cropping from untreated soils and soils initially receiving 12 mg of Zn per 3 kg of soil in a highly H2O‐soluble form were comparable.

In a second experiment differential response of several corn hybrids to amount of P and Zn and level of Zn solubility in the fertilizers suggests that the test variety might influence the interpretation of the results from fertilizer evaluation studies. No relationship was found between P/Zn ratios in the corn forage and the seed. The P/Zn ratios in corn forage were not related to the response of corn to applied Zn.
Interlayer Forces in Montmorillonite and Vermiculite
Authors: Kittrick J. A.
Published: July 2010

Oriented X‐ray spacings for vermiculite and montmorillonite were obtained as the sample temperature was changed at a constant rate. Temperatures at which an abrupt change in (001) spacing took place indicated the relative ease of expansion or contraction for a series of interlayer ions. From such temperatures, the difference between contracting and expanding forces was found to be dependent upon interlayer ion charge, distance, and hydration energy, indicating essentially a strong‐force balance (ion‐water, ion‐clay) for both vermiculite and montmorillonite.

Transition temperatures for hydration were lower than the corresponding dehydration temperatures, where small interlayer ions were involved. After removal of a water layer, the layer silicate contracted. Stronger hydrating forces at lower temperatures were required to reexpand the layer silicate prior to sorption of a corresponding water layer. Where the size of the interlayer ion approached that of the water molecule, preventing contraction during dehydration, the hysteresis was eliminated.

Temperatures at which comparable interlayers of water molecules were removed were higher for vermiculite than for montmorillonite, for Li, Na, Mg, Ca, Sr, and Ba ion saturations. A semi‐quantitative consideration of the strong‐force model indicates the presence of an expanding force in addition to hydration of interlayer ions, and one that is much stronger in vermiculite than in montmorillonite. Hydration of the negative charge sites meets these requirements, but does not explain ion fixation by vermiculite. Hydration of negative charge sites is indicated by plateau formation in the curves, by ion hydration theory and by swelling theory of ion‐exchange resins.
Plant Uptake and Chemical Extractions for Evaluating Potassium Release Characteristics of Soils
Authors: Conyers E. S. , McLean E. O.
Published: July 2010

Five soils were treated with K at rates of 269, 134, and 0 kg/ha and were diluted 6:4, 3:7, and 1:9 with sand. Potassium was extracted from samples of the soils and soil‐sand mixtures by various methods. The treated soils were then sequentially cropped in a growth chamber to German millet (Setaria italica stramineofructa) (one cutting) and alfalfa (Medicago sativa) (four cuttings). After cropping, K was again extracted from samples of the soils and mixtures.

The soils differed greatly in amounts of K released to the plants and to the various extracting solutions. Amounts of K removed by NH4OAc, HNO3, HCl, and NaBPh4 from soils prior to cropping generally correlated better with amounts of K uptake than did amounts of K removed by other extractants. When all soils, K additions, and soil dilutions were combined, energy of exchange (ΔF) values were poorly correlated with K uptake because of greater than proportional release of K in soil‐sand mixtures. Both the plants and chemical extractants removed more K from soil‐sand mixtures than that calculated on the basis of proportions of the soil in the mixtures. Cropping considerably reduced the amounts of exchangeable and boiling HNO3 releasable K and caused ΔF values to become more negative.
Rate of Cation Exchange on Clay Minerals as Determined by Specific‐Ion Electrode Techniques
Authors: Malcolm R. L. , Kennedy V. C.
Published: July 2010

A cationic electrode (used as a potassium specific‐ion electrode and a sodium specific‐ion electrode were used to measure rates of cation exchange on clay minerals. The Ba‐K exchange rates for kaolinite, illite, and montmorillonite were rapid with >75% exchange being measured within 3 sec. Because this time interval represents response time of the specific‐ion electrode, the Ba‐K exchange on these clay minerals occurs at a faster rate than this and may be an instantaneous process. Ba‐K exchange on vermiculitic materials was characterized by both a rapid and a slow rate of exchange. A major part of the Ba‐K exchange in silt‐ and clay‐size vermiculite was found to be diffusion controlled.

Ca‐K, Mg‐K, Ca‐Na, and Mg‐Na exchange rates were rapid for all vermiculites and other clay minerals used in the experiment. Only Poole vermiculite exhibited two rates of Ba‐Na exchange similar to those shown by all vermiculites during Ba‐K exchange. Ba‐Na exchange rates on all vermiculites except Poole were rapid.
Influence of Soil Moisture Tension on Nitrate Accumulation in Soils
Authors: Sabey Burns R.
Published: July 2010

The influence of soil moisture tension on NO‐3‐N accumulation was studied in limed, silt loam, loessial derived soils to which a non‐limiting source of NH+4‐N was added. This was done by saturating the soils in an NH+4 solution, then subjecting the samples to 0, 0.1, 0.33, 1, 5, and 15 bars of soil moisture tension in conventional positive pressure equipment, and incubating the samples in a saturated atmosphere for varying intervals, to characterize the NO‐3‐N accumulation curve with time. The maximum slope of the line gave an estimate of the KM value or maximum rate of NO‐3‐N accumulation in ppm/day. The KM values in all soils were greatest at 0.1 bar tension, with KM values decreasing as soil moisture tension increased or decreased. The relative rates of NO‐3‐N accumulation, RM values or moisture rate indexes, varied much less than KM values among soils. The mean RM values at 0.1, 0.33, 1, 5, and 15 bars tension were 1.0, 0.71, 0.53, 0.29, and 0.13, respectively. The moisture rate index curve can be used to estimate the amount of NO‐3‐N accumulation in soils similar to those used in this study at all soil moisture tensions between 0.1 and 15 bars if the rate of NO‐3‐N accumulation is known at any one tension within the above range. The moisture rate index curve of this study and the temperature rate index curve of a previous paper are used in the previously proposed equation, N = KFRK(t − tFrt), to estimate NO‐3‐N accumulation in soils under varying conditions of temperature and soil moisture tension.
Effects of Soil Physical Properties, Rainfall Characteristics, and Wind Velocity on Clod Disintegration by Simulated Rainfall
Authors: Lyles Leon , Disrud L. A. , Woodruff N. P.
Published: July 2010

The effects of clod size and density, rainfall intensity and duration, and wind velocity on clod disintegration by simulated rainfall were studied in a laboratory wind tunnel‐raintower facility. Significant interactions (including those of higher order) were found among the variables studied. Clod bulk density had a minor effect on disintegration. For a specific clod size and wind velocity, 10‐min rains at 5.61 cm/hour were about as destructive as 90‐min rains at 1.60 cm/hour, even though the total volume of rainfall was 2.5 times larger in the latter case.

Wind‐driven rain was very effective in clod disintegration. Up to 66% more soil was lost from clods exposed to 13.4‐m/sec winds than from those exposed to no wind for the same rain intensity, duration of exposure, and clod size. Mean drop size striking the clods probably increases with wind velocity and would account for some of the wind effects. Small clods were more susceptible to disintegration by raindrop impact than large clods. Multiple regression analyses indicate about 80 and 89% of the soil detachment variance was accounted for by linear and curvilinear procedures respectively.
Lindane Diffusion in Soils: II. Water Content, Bulk Density, and Temperature Effects
Authors: Ehlers Wilfried , Farmer W. J. , Spencer W. F. , Letey J.
Published: July 2010

The diffusion of lindane in Gila silt loam is strongly influenced by soil water content, bulk density, and temperature. The diffusion coefficient is nearly zero in soil of 1% water content. With an increase to 3% water content, which is equivalent to two layers of water between the montmorillonite clay plates, water is able to displace the lindane from the adsorbing surface so that the diffusion coefficient becomes maximal. A small additional increase in water content reduces the diffusion coefficient to about one‐half of the maximal value. This value then remains constant with increasing water content up to saturation. Decreasing bulk density or increasing temperature raises the diffusion coefficient. The influence of bulk density and temperature on diffusion is in good agreement with theoretical calculations.
Water Movement and Freezing Pressures
Authors: Hoekstra Pieter
Published: July 2010

Pressures develop when cylindrical columns of saturated soils are frozen unidirectionally under conditions of constant volume with an open water supply at the warm side. The value and behavior of these pressures depend on soil type.

If water migration can take place in the frozen soil and ice lenses grow behind the freezing front the value of the pressure depends on the temperature at the ice lens. This process occurs in clayey soils, and the pressure is theoretically limited by the phase transition ice 1 — water. Values of 100 atm have been measured experimentally.

In soils where water migration in the frozen soil does not occur and ice lenses form at the freezing front, the pressure reaches a constant value, which may vary between 0.2 atm for a sand soil and 3 atm for a silt soil.

Thermodynamic models proposed to explain these phenomena are discussed.
The Stability of Different Forms of Selenium Applied to Low‐Selenium Soils
Authors: Cary Earle E. , Allaway W. H.
Published: July 2010

In some acid‐to‐neutral soils, water‐soluble selenite salts react rapidly with the solid phase to form a relatively insoluble adsorption complex. The Se in this complex is less available to alfalfa (Medicago sativa L. ‘Dupuit’) than the Se added to the same soil as Fe(OH)3‐HSeO3. In other soils, or in some acid soils limed to neutrality, the availability of Se to alfalfa from NaHSeO3 and from Fe(OH)3‐HSeO3 is essentially the same. The availability of Se from Seo added to the same soils is less than from either NaHSeO3 or Fe(OH)3‐HSeO3 sources. Oxidation of Seo is initially rapid in these soils, and does not seem to be pH dependent, but the rate of oxidation varies in different soils. Soluble selenite may be the most practical form of Se to add to low‐Se soils in order to produce crops containing sufficient Se to meet animal requirements.
Poorly Drained Soils with Permafrost in Interior Alaska
Authors: Allan R. J. , Brown Jerry , Rieger Samuel
Published: July 2010

Physical, chemical, and mineralogical properties are presented for five soils with permafrost in interior Alaska. The soils are shallowly thawed, with permafrost usually at 60 cm or less, and with a thick accumulation of organic matter, usually about 25 cm deep, over a gleyed mineral soil. They are classified as Histic Pergelic Cryaquepts in the comprehensive soil classification system adopted by the US Department of Agriculture. Histic Pergelic Cryaquepts are the most extensive soils developed over permafrost in Alaska. In three of the five profiles, particle‐size analyses reveal a slight increase (2–4%) in clay content of the thawed mineral soil over that of the permafrost. The coarsest horizon in all five profiles contains only 48% sand. The dominant texture is silt loam. In one of the profiles, base saturation increases (52–90%) with depth in the thawed mineral soil, then remains fairly constant in the permafrost. Percent Zr (0.02%) remains constant in the coarse silt fraction of all horizons of all five profiles both above and in the permafrost. The dominant clay minerals in the thawed horizons were vermiculite and kaolinite.
Growth and Foliar Nutrition of White Pine Seedlings as Influenced by Simultaneous Changes in Moisture and Nutrient Supply
Authors: Schomaker Charles E.
Published: July 2010

A greenhouse study was used to investigate the effects of varying moisture supply and nutrient solution concentration concurrently on the growth and foliar nutrient concentration of white pine (Pinus strobus L.) seedlings. Seedlings were treated with four nutrient solution concentrations over four different periods of time between irrigations in all possible combinations. Mean seedling weight decreased with reduced nutrient solution concentration and with increasing time between irrigations. The interaction between nutrient solution concentration and irrigation schedule was highly significant in regard to effect on seedling weight.

Mean N, K, and P concentrations in the needles showed significant increases with an increase in moisture stress. Irrigation treatment had no significant effect on foliar Ca or Mg concentrations. Of the micronutrients only B and Mn were affected by irrigation treatments. In general foliar concentrations of the macronutrients were negatively correlated with the micro‐nutrients.
The Utilization of Applied Zinc as Affected by pH and Pyrophosphate Content of Ammonium Phosphates
Authors: Hossner L. R. , Blanchar R. W.
Published: July 2010

Laboratory preparations of pure ammonium ortho‐ and pyrophosphates were blended to give mixtures containing 0, 20, 40, 60, 80, and 100% of the total P as pyrophosphate at pH values of 3.6, 4.0, 5.0, 6.0, 7.0, and 8.0. Each ammonium phosphate mixture was blended with ZnSO4 · H2O to yield a product containing 2 or 8% Zn, formed into a pellet, and reacted with soil solution. Residues were recovered and analyzed for chemical and mineralogical composition.

The quantity and species of Zn precipitating in the residues were markedly influenced by the pyrophosphate content and pH of ammonium phosphate mixtures. At pH 3.6 and 4.0, the quantity of Zn in the residue was increased with increasing pyrophosphate content. At pH 5.0 all of the Zn precipitated when the P was 100% orthophosphate but as the pyrophosphate level was increased to 60% more Zn moved out of the pellet. The Zn content of the residues decreased as pH increased (6.0, 7.0, and 8.0) and was lowest when the mixture contained 40, 60, and 80% pyrophosphate, respectively.

Two zinc ammonium orthophosphates, ZnNH4H3(PO4)2 · H2O and ZnNH4PO4, were identified in the residues. Zinc ammonium pyrophosphates identified were Zn(NH4)2H4(P2O7)2 · 2H2O, Zn3(NH4)2(P2O7)2 · 2H2O, and Zn(NH4)2P2O7 · H2O.

Ammonium phosphate mixtures with pH values of 3.6, 6.0, and 8.0 containing 2% Zn as 65ZnSO4 · H2O were spot‐placed in pots and evaluated in growth chamber experiments. Plant uptake of Zn was proportional to the quantity of Zn which moved from the placement site.
Hydrolysis and Sorption of Ortho‐, Pryo‐, Tripoly‐, and Trimetaphosphate in 32 Midwestern Soils
Authors: Blanchar R. W. , Hossner L. R.
Published: July 2010

Hydrolysis and sorption reactions of orthophosphate (OP), pyrophosphate (PP), tripolyphosphate (TPP), and trimetaphosphate (TMP) were studied in 32 Corn Belt soils. TMP hydrolyzed to TPP in 1 day in all but two soils. TPP hydrolyzed to PP and OP within 7 days in 30 of 32 soils, and 15 to 80% of the PP formed in the soil remained after 14 days. The sodium salts of OP and PP were compared as P sources for corn and found to be equal. It was concluded that under our conditions (25C), the rate of TMP, TPP, and PP hydrolysis was rapid enough so it would not limit the availability of P to plants.

TMP added to soil remained water soluble. The sorption of TPP and PP by soil was more than OP.
Soil‐Water Hysteresis Measured in a Sandy Loam and Compared with the Hysteretic Domain Model
Authors: Topp G. C.
Published: July 2010

A uniformly packed column of sandy loam soil was subjected to a controlled series of wetting and drying changes. Soil water contents were obtained from gamma ray attenuation information while simultaneous tensiometer pressures at five locations along the column were measured by a pressure transducer. In addition, the flows of the water solution to and from the column were read in burettes. The data from the tensiometers demonstrated a high degree of uniformity throughout the soil. Analysis of the primary scanning curves of the water content versus pressure head showed that the independent domain theory of hysteresis is an inadequate model for both wetting and drying curves. A refinement to the theory could not be tested with these data. Following consolidation during the initial drying phase there was no measurable hysteresis in the water content‐hydraulic conductivity relationship.
Resolving Time, Mass Absorption Coefficient and Water Content with Gamma‐Ray Attenuation
Authors: Fritton D. D.
Published: July 2010

A method is described that was used to experimentally determine an intensity correction for gamma‐ray attenuation. The correction is determined by using the minute nonlinearity of a semi‐log plot of gamma‐ray intensity versus the thickness or the product of thickness and density of a material. The experimentally determined correction is expressed in terms of resolving time and varied with both material and counting rate. A correction of 5.0 µsec/count was determined experimentally as the best resolving time to correct the observed counting rates for water content determination. Part of the 5.0 µsec/count correction was evidently due to causes other than resolving time. Mass absorption coefficients of water and soil were 0.08105 and 0.07309 cm2/g, respectively, with no correction and were 0.0871 and 0.0773 cm2/g with a 5.0 µsec/count correction. The difference between gravimetric water content and gamma‐ray water content dropped from 3.02% to 0.60% when this correction was used.
An Organic Carbon‐Organic Matter Conversion Equation for Pennsylvania Surface Soils
Authors: Ranney R. W.
Published: July 2010

Low temperature ashing was used to determine the organic matter content of soils by weight loss. This technique utilizes oxygen excited by radiofrequency energy to effect oxidation at relatively low temperatures. Ashing at 375C was used for samples high in organic matter. Corrections were applied for weight loss of inorganic constituents and for incomplete oxidation of organic matter. The following regression equation was developed to convert organic carbon percent to organic matter percent in Pennsylvania surface soils:

Percent organic matter = 0.35 + 1.80 × percent organic carbon.
Effect of Picloram, Diuron, Ametryne, and Prometryne on Nitrification in Some Tropical Soils
Authors: Dubey H. D.
Published: July 2010

Effect of 4‐amino‐3,5,6‐trichloropicolinic acid (picloram), 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (diuron), 2‐ethylamino‐4‐isopropylamino‐6‐methylthio‐s‐triazine (ametryne), and 2,4‐bis(isopropylamino)‐6‐methylthio‐s‐triazine (prometryne) at rates from 2 to 100 ppm on nitrification of 100 ppm applied NH4‐N was studied in several soils of Puerto Rico incubated at 24C for 8 weeks.

The effect was greatly dependent on the nitrifying capacity of the soils. Inhibition of nitrification by herbicides was less in soils of high nitrifying capacity than in soils of low nitrifying capacity. Picloram at 2 ppm caused a weak inhibition and at 20 to 100 ppm complete inhibition except in the soil of high nitrifying capacity. Diuron inhibited nitrification at 20 ppm and above in soils of low to intermediate nitrifying capacity. It did not affect nitrification in the soil of high nitrifying capacity even at 100 ppm. Ametryne and prometryne at 100 ppm inhibited Nitrobacter bacteria, but not NH4‐ oxidizers resulting in high NO2‐ accumulation. At certain times 60 to 100% of the applied NH4‐H appeared as NO2‐ when prometryne and ametryne were applied at 100 ppm, respectively. Nitrite accumulated, however, only at soil pH of 6.8 and above.
Leaf Composition and Yield Response of Corn in Relation to Quantity‐Intensity Parameters for Potassium
Authors: Koch J. T. , Orchard E. R. , Sumner M. E.
Published: July 2010

Data obtained by the quantity‐intensity (Q/I) technique were tested against field experimental results to assess the value of the Q/I approach for characterising the potassium (K) status of soils. Q/I data describe K status by relating the energy level or intensity (I) of K in the labile pool to the amount (Q) present.

It was shown that in a leached ferrallitic soil (Oxisol), the pool of labile K is a good index of the amount available to corn (Zea mays L.). It is superior as a criterion to both the equilibrium activity ratio and exchangeable K.

Potassium content of the leaf is related to the pool of labile K free to participate in the mechanisms by which K is supplied to roots. Critical values for K in the labile pool at the beginning of the growing season are proposed, below which K deficiency is likely to reduce corn yield.
Calcium Deficiency and Ammonia Toxicity as Separate Causal Factors of (NH4)2HPO4‐Injury to Seedlings
Authors: Bennett A. C. , Adams Fred
Published: July 2010

Short term experiments were conducted in a growth chamber with seedlings of sudangrass (Sorghum sudanensis) and cotton (Gossypium hirsutum L.) on a Lucedale sandy loam surface soil treated with different rates of MgO, CaO, (NH4)2HPO4, K2HPO4, and Ca(H2PO4)2. Sudangrass seed was planted in treated soils and the seedlings were allowed to grow for 14 days, during which time they were observed for symptoms of Ca deficiency or NH3 toxicity. Cotton seed was planted in a layer of untreated soil that was underlain by treated soil in glass‐front boxes for direct observation of root growth. The depth to which each primary root of cotton extended into the treated soil was measured periodically for 3 days after the root entered the treated soil. Results were related to ionic composition of soil solutions in situ. Calcium deficiency symptoms and reduced growth occurred on all soils with aCa/Σacation i ratios in soil solutions of 0.15 or less. Ammonia toxicity symptoms on foliage were caused by only one treatment although toxic concentrations of NH3(aq) were present in three other soil solutions. These solutions were also deficient in Ca. When conditions conducive to Ca deficiency and NH3 toxicity existed in the same soil solution, Ca deficiency symptoms dominated except at the highest NH3(aq) concentration.
Graphic Presentation of a Mathematical Solution for Interacting Diffuse Layers
Authors: Kemper W. D. , Quirk J. P.
Published: July 2010

The scaled electrical potential, Y = zεψ/kT, is presented as a function of the effective surface charge density, the external solution concentration, valence of the cation and distance between clay platelets for symmetric electrolytes. Swelling pressures and ion concentrations near the platelets may be calculated from these values of Y using some of the simple equations published by other authors and reproduced herein.
Elution of Potassium in Soil
Authors: Avnimelech Y. , Shaham Vera , Feder Adina
Published: July 2010

Displacement of potassium in soil by a solution of calcium sulphate is considered. The basic assumptions are the existence of a state of microscopic equilibrium and neglecting dispersion. A model is developed and computed.

The computed curves reveal the existence of two potassium peaks moving during the first stages of the leaching, one peak in the solution front and the main peak behind it. The first peak disappears at advanced stages of the migration. The experimental curves showed the main peak at the predicted locations, and indicated the existence of the first peak, which was flatter than the computed ones.

The relative velocity of the displaced ion (Rf) is discussed and computed. This value can be easily obtained for different soils and solutions and is an important parameter for a number of practical problems. The computed and experimental values for the relative velocity of the eluted potassium were in good agreement.
Comparison of Some Methods for Determination of Total Sulfur in Soils
Authors: Tabatabai M. A. , Bremner J. M.
Published: July 2010

A comparison of five methods of determining total sulfur in soils showed that the acid oxidation method of Arkley and the alkaline oxidation method of Tabatabai and Bremner gave almost identical results and were more precise than other methods studied. The results obtained by use of X‐ray fluorescence spectrography for determination of total sulfur in soils were, on average, slightly higher than those obtained by the Arkley or Tabatabai‐Bremner method, and they indicated that this technique can be used satisfactorily for routine sulfur analysis of mineral soils. Attempts to adapt the Leco Sulfur Analyzer for rapid and precise determination of total sulfur in soils were unsuccessful, but they suggested that this automated instrument might prove useful for sulfur analysis in some types of soil investigations. The data obtained indicate that several methods proposed for total sulfur analysis of soils give satisfactory results.
Degradation of Gamma‐BHC in Rice Soils
Authors: Yoshida T. , Castro T. F.
Published: July 2010

The biodegradation of the organochlorine insecticide, γ‐BHC (γ‐isomer of 1,2,3,4,5,6‐hexachlorocyclohexane) was evaluated for four Philippine rice soils: Casiguran sandy loam, Luisiana clay, Maahas clay and Pila clay loam. Rapid degradation of the insecticide was observed under flooded soil conditions. The rate of degradation for γ‐BHC was highest in Casiguran sandy loam; none of the parent insecticide remained in the soil after 1 month of incubation at 30C. Organic matter levels were related directly to rate of decomposition. Molecular oxygen, nitrate, and manganic oxide retarded the rate of γ‐BHC degradation. Increased temperature increased the rate of γ‐BHC degradation, and it appears that γ‐BHC residues are unlikely to be a problem in the tropical rice‐growing areas.
The Plant Availability of Potassium in Fly Ash
Authors: Martens D. C. , Schnappinger M. G. , Zelazny L. W.
Published: July 2010

The availability of K in fly ash obtained from nine coal burning power generating plants was evaluated by greenhouse and laboratory procedures. The total K content of the samples of fly ash ranged from 0.65 to 3.14%. Eight of the samples were bituminous coal ashes, and one was lignite coal ash. The samples of bituminous coal fly ash neutralized less than 0.25 meq H3O+/g, whereas the sample of lignite coal fly ash neutralized 3.05 meq H3O+/g. Application of three samples of the bituminous coal fly ash and the sample of lignite coal fly ash increased K uptake by corn plants (Zea mays L.) grown on Davidson clay loam. Potassium uptake was higher from application of 158 mg K as KCl to 2,100 g of the soil than from application of a higher rate of K as the four samples of fly ash. Equivalent K uptake by corn plants occurred from application of 79 mg K as KCl and 207 mg K as the lignite fly ash. However, yield was lower where the ash was applied. Tissue analyses indicated that B toxicity limited yield on the latter treatment. Application of certain of the fly ash samples increased Mg uptake by corn plants. This increase in Mg uptake probably caused a decrease in K uptake by plants grown in the fly ash‐soil mixtures.
Comparison of Iron and Aluminum Hydroxy Interlayers in Montmorillonite and Vermiculite: II. Dissolution
Authors: Carstea D. D. , Harward M. E. , Knox E. G.
Published: July 2010

The stabilities of hydroxy‐Al and ‐Fe interlayers in montmorillonite and vermiculite were evaluated by subjecting the systems to HCl treatment and to sequential treatments which included boiling 2% Na2CO3, buffered sodium citrate‐dithionite, a second citrate‐dithionite treatment, and boiling NaOH.

The stability of hydroxy interlayers was dependent on kind of mineral matrix, whether the interlayer was Fe or Al, and the conditions of acidity under which they were initially formed. Hydroxy‐Al interlayers formed under acid conditions were more stable than those formed under alkaline conditions in both montmorillonite and vermiculite systems. Iron interlayers formed under neutral and alkaline conditions in montmorillonite and vermiculite were more stable than those formed in acid media. The hydroxy‐Al and ‐Fe interlayers in montmorillonite exhibited a higher stability than their counterparts in vermiculite.

A residual 14A line after K‐saturation and heating to 550C was observed in some samples which received the dithionitecitrate and NaOH treatments. This occurred to a greater extent in vermiculite and particularly with Fe‐hydroxy systems. The data suggested a resolution of a mixed system into collapsible and noncollapsible components.

In montmorillonite, the hydroxyl‐Al interlayer, formed in alkaline conditions, showed the highest stability to the HCl treatment, whereas that formed in acid medium was the least stable. In vermiculite, the stability of hydroxy‐Al interlayer to the HCl treatment decreased from acid to alkaline media.

Iron interlayers in montmorillonite formed in all media exhibited high stabilities to the HCl treatments. In vermiculite, the HCl treatments removed more interlayers from acid media than from alkaline media.

Some of the dissolution treatments tested in this study are often used as pretreatments for removal of coatings and cementing agents prior to separation or analysis of clay fractions. These reagents will remove hydroxy interlayers and result in changes of properties of clays from soils and sediments. This must be recognized for proper interpretation of data for clay mineral identification and characterization.
Soil Temperature and Water Content Changes During Drying as Influenced by Cracks: A Laboratory Experiment
Authors: Selim H. M. , Kirkham Don
Published: July 2010

A container consisting of three identical compartments each 30 cm long, 30 cm deep, and 10 cm wide, was used to study the influence of artificial soil shrinkage cracks on heat and water content redistribution in three soil materials subjected to wind or radiative drying of 1.18 and 2.54 cm of water per 24 hours evaporation potential, respectively. Three crack widths were used, 0, 0.64, and 1.91 cm. Moisture content and temperature distributions were measured with time up to 12 days. The cracks decreased water content as much as 5 to 10% by volume. Evaporation through crack walls caused lateral movement of water for a distance of 4 to 5 cm from the wall of a 0.64‐cm crack after 12 days of radiative drying. These distances were greater up to 14 cm (for the sand). Under wind, distances of lateral movement of water were about 5 cm, for all drying times. For all three soils with cracks, after 4 days of wind drying, soil temperature was cooler (1 to 2C lower) than for the soils with no cracks. Under radiation all three soils were warmer (5 to 10C higher) than soils with no cracks, after 4 days. In general, shrinkage cracks increased evaporation from bare soil 12–16% with cracks 0.64 cm wide and about 30% with cracks 1.91 cm wide as compared to evaporation from soils with no cracks.
Accumulation of Mercury Vapor in Soils Laboratories
Authors: Fisher H. D. , Cary J. W.
Published: July 2010

The rate of accumulation of mercury vapor in a closed room was determined as a function of surface area of the exposed mercury, ambient temperature, and air flow. The rate of mercury vapor accumulation was much higher than suspected by many soil scientists. For example, in a 3‐ by 3‐ by 2‐m constant temperature room, 250 cm2 of mercury surface produced toxic levels of mercury vapor within 13 minutes. Water or oil covering the surface of the mercury was a highly effective means of suppressing vaporization. The standard decontamination treatment with sulfur proved effective, but only after complete amalgamation occurred.
Detachment of Soil Aggregates by Simulated Rainfall
Authors: Mazurak Andrew P. , Mosher Peter N.
Published: July 2010

Sharpsburg silty clay loam was separated into 11 aggregate fractions with the following diameters: 9,250–4,760µ, 4,760–3,360µ, + … +, 297–210µ, and <210µ. Krilium solution was added to half of each aggregate fraction to make the aggregates more water‐stable. The aggregate fractions were packed into splash‐cups and exposed to simulated rainfall intensities from 2 to 12 cm/hr. Raindrops were 5.1 mm in diameter and fell 11.33 m onto the surface of soil materials. Splash of soil particles and aggregates was caught, oven‐dried, and weighed.

The amount of detachment of aggregates was linearly related to the rainfall intensity.

Detachment of non‐treated aggregates exposed to rainfall increased from 76 mg of particles per cm3 of water to a maximum amount of 172 mg/cm3 as the aggregate diameters decreased from 9,250–4,760µ to 2,360–1,680µ. Then, the amount of detachment decreased with decreasing diameter to aggregate to 78 mg/cm3 for aggregates < 210µ diameter.

The addition of Krilium to aggregates reduced the amount of detachment of aggregates >420µ in diameter exposed to simulated rainfall. The amount of splash increased with decreasing diameter of Krilium treated aggregates until 297–210µ diameter was reached (138 mg/cm3), then it decreased (101 mg/cm3) for aggregates < 210µ diameter.