bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calcium‐Magnesium Exchange Selectivity of Wyoming Montmorillonite in Chloride, Sulfate and Perchlorate Solutions
Authors: Suarez D. L. , Zahow M. F. 
Published: July 2010

AbstractThe need to consider CaCl+ and MgCl+ complexes in Ca‐Mg exchange reactions on montmorillonite was evaluated by examining cation selectivity in various anion backgrounds. The Ca‐Mg exchange isotherms on SWy‐1 Wyoming bentonite were determined in 0.0125 M SO4, 0.025, 0.050, and 0.100 M Cl and 0.03 M perchlorate background. Calculated selectivity values for the reaction Ca2+ + MgX ⇌ Mg2+ + CaX were Kv = 1.15, 1.11 and 1.10 for the SO4, Cl and perchlorate media, respectively. There was no trend in Kv, with exchangeable Ca with any anion or with ionic strength in Cl media. The Ca preference in SO4 and perchlorate media indicates that montmorillonite preference for Ca is not an artifact of complexation in Cl media. These Kv values are also consistent with earlier published Ca‐Mg selectivity of the same clay in perchlorate media. The CaCl+ and MgCl+ complexes comprised an insignificant amount of the exchangeable cations.
Calcium and Sulfate Retention by Two Oxisols of the Brazilian Cerrado
Authors: Marcano‐Martinez E. , McBride M. B. 
Published: July 2010

AbstractThe ability of two representative oxisols from the Cerrado region of Brazil to adsorb Ca2+ and SO2‐4, when in their natural acidic state, was determined by using dissolved CaCl2, K2SO4 and CaSO4 salts as adsorbates. Calcium adsorption from CaCl2 and CaSO4 was nearly linearly dependent on the equilibrium Ca2+ concentration, and was most successfully fitted to a Freundlich equation. Conversely, sulfate adsorption from K2SO4 and CaSO4 was curvilinearly dependent on equilibrium SO2‐4 concentration, conforming more closely to Langmuir adsorption behavior. Calcium adsorption was explained by nonspecific electrostatic attraction to soil clays, and did not appear to be adsorbed to any significant degree by the native organic matter. Sulfate adsorption was attributed at least in part to a ligand exchange mechanism, resulting in a measured increase in the negative charge of the soil surfaces. Simultaneous adsorption of Ca2+ and SO2‐4 from CaSO4 solutions caused an enhancement in retention of both ions at higher concentrations, despite undersaturation with respect to gypsum precipitation. A mechanism of CaSO04 ion pair adsorption on mineral surfaces is proposed in which the presence of one ion facilitates adsorption of the other.
Predicting Rates of Wheat Residue Decomposition
Authors: Stroo H. F. , Bristow K. L. , Elliott L. F. , Papendick R. I. , Campbell G. S. 
Published: July 2010

AbstractPredicting the rate and extent of decomposition of residues at the soil surface is necessary to evaluate the impacts of minimum‐tillage practices on erosion control and thus ensure the most effective use of residues. A mechanistic model simulating the decomposition of surface‐managed winter wheat residues was developed and model predictions were compared to results from field studies of decomposition rates. The model consists of two submodels. The first simulates decomposition of the various components of wheat residues (straw, leaves, and chaff) under constant conditions. This submodel requires input on the N content of the residue, and is based on results of laboratory experiments in which respiration was measured. The second submodel uses meteorological data to simulate environmental conditions in the residue layer. This information is combined with laboratory derived estimates of the effects of temperature and moisture to calculate the cumulative decomposition days. To apply the model to field situations, the relationships between respiration and mass loss were estimated experimentally. The effects of added microarthropods and nematodes were also measured, but no effects on respiration were observed in either case. Model predictions agreed well with data from field experiments in which bundled straw was used, but decomposition of straw in litter bags was slower than predicted. When grab samples were used to measure the loss of residues containing leaves, chaff, and straw, the model performed well even across climatic regions until early summer (32–36 wk after residue placement in the field), when residues began to disappear more rapidly than predicted.
Geomorphic Age and Genesis of Some San Luis Valley, Colorado, Soils
Authors: Nettleton W. D. , Brasher B. R. , Yenter J. M. , Priest T. W. 
Published: July 2010

AbstractSan Luis Valley is a semibolson in south central Colorado that has varying geomorphic and soil properties. Three sets of geomorphic surfaces were identified corresponding to young, intermediate, and old surfaces. A 14C date of 11 170 YBP on a peat deposit on the valley floor was used to separate Holocene geomorphic surfaces (Set 1) from late‐Pleistocene ones (Set 2). The oldest‐Pleistocene surfaces (Set 3) studied are believed to be Illinoian in age. They are above the late‐Pleistocene age valley floor and are more dissected than the other Pleistocene surfaces. Entisols have formed on the Holocene surfaces (Set 1). These Entisols have some accumulation of organic C and movement of carbonate, but none have calcic horizons. Their sand grains lack clay cutans or other evidence of soil formation. Most of the soils on late‐Pleistocene geomorphic surfaces (Set 2) have argillic and calcic horizons, and some have mollic epipedons. Grain argillans on sands are the most common form of illuvial clay and there are calcans in the calcic horizons. Some of the soils have natric horizons. The soils on mid‐Pleistocene geomorphic surfaces (Set 3) have a greater clay accumulation than any of the other soils and have calcic horizons. Clay accumulation is largely masked by the carbonate accumulation. The distribution of salt for the most part is in balance with today's arid climate in the valley. The occurrence of carbonate in horizons with illuvial clay, especially in the soils on the oldest surfaces, suggests an arid climate following one or more Pleistocene pluvials. Some of the salt and carbonate may have been added as dust from playas on the valley floor.
A Re‐Examination of Alternative Test Procedures for Soil Consistency Limit Determination: I. A Compression‐Based Procedure
Authors: McBride R. A. , Bober M. L. 
Published: July 2010

AbstractA static uniaxial (drained) compression test procedure using effectively saturated, remoulded soil samples is proposed which unifies soil consistency limit determination procedurally under similar experimental conditions. It yields numerically comparative (r2 = 0.786–0.931), rather than only correlative, indices of the upper and lower limits of soil plasticity while providing ancillary information on the effective stress regime when in these states of consistency. For the 44 soil horizon samples used in this study, apparent equivalent stresses at the Atterberg consistency limits ranged from 0.26 to 1.84 MPa for the lower plastic limit and 3.9 to 268 kPa for the upper plastic limit. Clay and organic matter contents had a significant influence on defining these equivalent static loadings. Organic matter was further shown to expand the range of moisture contents representative of the semisolid consistency state while constricting the plastic range. Potential areas for improvement in the procedures are discussed.
A Re‐Examination of Alternative Test Procedures for Soil Consistency Limit Determination: II. A Simulated Desorption Procedure
Authors: McBride R. A. 
Published: July 2010

AbstractA soil water retention model was used to simulate a desorption procedure for Atterberg consistency limit determination (i) to test the validity for Ontario soils of this procedural alternative to the A.S.T.M. standard methods in light of past research efforts, and (ii) to allow for the assessment of soil plasticity and related soil qualities for soil inventory interpretive purposes with only a minimum of soil physical data. From a remoulded and effectively saturated initial condition, the upper and lower plastic limits of the 290 soil horizons investigated were generally found to occur at the upper and lower flex points, respectively, of the estimated moisture retention curve. The presumed absolute equivalence of the effective normal stress required to bring soils to their respective Atterberg consistency limit moisture contents in a compression‐based test procedure with the negative pore water pressure potential at the estimated moisture characteristic flex points was corroborated. The observed tendency to underestimate the A.S.T.M. lower plastic limit of low clay content (marginally plastic) soils was attributed to procedural limitations in the A.S.T.M. standard methods which set the lower moisture content limit of plasticity of such soils unrealistically high. Clay and organic matter contents influenced both the effectively saturated gravimetric moisture content attained by free swelling soils in a remoulded condition and the pore water pressure potential at the lower plastic limit. Only clay content was a significant factor in explaining variations in pressure potential at the upper plastic limit with soil texture.
Modeling of Wheat Imbibition and Germination as Influenced by Soil Physical Properties
Authors: Bouaziz A. , Bruckler L. 
Published: July 2010

AbstractA theoretical model that was used previously for predicting maize (Zea mays L.) seed imbibition, and subsequently, germination, is applied to wheat (Triticum aestivum L.) seeds. The proposed model takes into account the seed‐soil water movements in both liquid and vapor phases under nonlimiting aeration conditions. The main variables that govern the imbibition process are (i) the seed‐soil water potential difference, (ii) the seed contact area as affected by vapor or liquid transfers, and (iii) conductive properties of the seed for both liquid and vapor phases. Laboratory experiments show that (i) the imbibition process occurs both in liquid and vapor phases, (ii) wheat seed must reach a critical moisture content before germination (0.27 kg kg−1 approximately), and (iii) the rate of the imbibition depends upon the seed surface area affected by liquid or vapor transfers and on the water potential of the external medium that governs the ability of the seed to reach its critical moisture content. The proposed model is regarded as satisfactory after calibration of the seed conductive properties in liquid and vapor phases. Field experiments involved irrigated and nonirrigated treatments (31.7% clay, 42.5% loam, 25.8% sand) and manual or mechanical sowing. Moisture content, bulk density profiles, and soil porosity analyses were used to estimate the seed‐soil contact area. The previous imbibition model was applied to field experiments, combining field data with the laboratory results. This model accurately predicted wheat imbibition and germination. Finally, simulated results compared the effects of climatic conditions and sowing techniques on wheat germination for three climatic sequences. Climate was the major limiting factor illustrating the importance of selecting the suitable sowing techniques to optimize the seed imbibition and germination processes.
Influence of Topsoil Removal and Fertilizer Application on Spring Wheat Yields
Authors: Tanaka D. L. , Aase J. K. 
Published: July 2010

AbstractTopsoil loss by wind and water erosion has reduced crop productivity and created soil management problems. Crop yield‐soil loss relationships vary, depending on soil, climate, crop, and management practices. The purpose of this study was to determine the relationships among surface soil removal and additions of nitrogen (N) and phosphorus (P) fertilizer on spring wheat yields and yield components. Soil was mechanically removed from the surface of a Williams loam (fine‐loamy mixed, Typic Argiboroll) to 0.00‐, 0.06‐, 0.12‐, and 0.18‐m depths in a spring wheat (Triticum aestivum L.)‐fallow rotation. Three levels of N (0, 35, and 70 kg ha−1) and three levels of P (0, 20, and 40 kg ha−1) were applied in all combinations to each soil removal treatment prior to seeding a spring wheat crop. In 3 of 5 years, soil removal treatments reduced spring wheat yields an average of 9, 28, and 45% for 0.06‐, 0.12‐ and 0.18‐m soil removal treatments, respectively, when averaged over all fertilizer treatments compared to 0.00‐m soil removal treatment. The other 2 years were water limiting and soil removal treatments were not a factor. Application of 20 and 40 kg ha−1 of P fertilizer increased grain yields 75 to 400 kg ha−1 with yield increase associated with an increase in heads m−2 and kernels head−1. Phosphorus application tended to decrease grain N concentration because grain yields were increased which caused a dilution in grain N concentrations. Application of 35 and 70 kg ha−1 of N, in combination with either 20 or 40 kg ha−1 of P, resulted in greater grain yield increases when compared to N application without P. Generally 70 kg ha−1 of N and 20 kg ha−1 of P increased grain yields on 0.06‐, 0.12‐, and 0.18‐m soil removal treatments to at least the same yield as 0.00‐m soil removal treatment without N or P fertilizer. These data suggest P was the most limiting nutrient and additions of N fertilizer without P resulted in small yield increases.
Effect of Polysaccharides, Clay Dispersion, and Impact Energy on Water Infiltration
Authors: Ben‐Hur M. , Letey J. 
Published: July 2010

AbstractEffects of clay dispersion, impact energy of water drops, and chemical amendments on crust formation and infiltration rate (IR) of Haplic Durixeralf soil were studied using a sprinkler infiltrometer. The soil was subjected to two impact energies, high energy = 240 J m−2 h−1 and low energy = 0, and to three waters: (i) distilled water [DW, electrical conductivity (EC) < 0.05 dS m−1], (ii) saline water (SW, EC = 5.0 dS m−1), and (iii) regular water (RW, EC = 1.0 dS m−1). The chemical amendments, polysaccharides, guar derivatives were supplied with the DW and RW and with high impact energy. Crust formation by the impact energy was found as a dominant factor in the IR reduction. This factor reduced the total soil infiltration capacity by more than 40%. Conversely, clay dispersion in the soil surface reduced the total soil infiltration capacity by 24%. Likewise, it was found that clay dispersion in the soil surface decreased the hydraulic conductivity of the crust and sharply increased its hydraulic resistance. The polymers had an amendatory effect on the IR. The polymers apparently adsorbed on the particle surfaces and acted as a cementing material holding primary particles together against the destructive forces of the water drops. The order of the maximum effect of the chemical amendments (0.01 kg m−3), that were supplied in DW, on the maintenance of IR was: high charge cationic polymer (HCCP) > low charge cationic polymer (LCCP) ≫ nonionic polymer > anionic polymer (had no effect). A concentration of 0.01 kg m−3 of HCCP and LCCP in RW prevented crust formation and preserved the high initial IR of the soil throughout the water application period. The HCCP and LCCP under sprinkled DW and RW conditions apparently adsorbed at the soil surface and did not move with the water into the soil layer.
Effect of Subsoiling on Yield and Quality of Corn and Potato at Two Irrigation Frequencies
Authors: Ibrahim B. A. , Miller D. E. 
Published: July 2010

AbstractHigh strength soil layers within a rooting zone restrict rooting and reduce the supply of water and nutrients to plants. Frequent irrigation may be required to prevent plant water stress. Studies were conducted in 1983, 1984, and 1985 to evaluate the yield responses of potato (Solanum tuberosum L.) and field corn (Zea mays L.) to subsoiling and sprinkler irrigation frequency on Warden loam (coarse‐silty, mixed, mesic Xerollic Camborthids) and Quincy sand (mixed, mesic Xeric Torripsamments) soils. Leaf water potential, stomatal resistance, and canopy temperature were measured. On the loam soil, yield and % U.S. no. 1 potato tubers responded positively to subsoiling with biweekly irrigation but not with weekly irrigation. Corn silage yields were increased by subsoiling with both irrigation regimes but grain yields were not. Plants growing on subsoiled sand and irrigated every 4 d were stressed less than plants grown without subsoiling. With this irrigation regime total tuber yield, % U.S. no. 1 tubers, and corn grain yields were increased by subsoiling. Benefits from subsoiling were relatively unimportant for either crop or soil if irrigation was adequate.
Nitrogen Placement Evaluation for Winter Wheat in Three Fallow Tillage Systems
Authors: Varvel G. E. , Havlin J. L. , Peterson T. A. 
Published: July 2010

AbstractIncreased soil water storage with increasing amounts of surface residue in winter wheat (Triticum aestivum. L.)—fallow cropping systems has not consistently resulted in higher grain yields in the Great Plains. Earlier results had suggested increased amounts of surface residue may increase N immobilization and limit N availability, thereby reducing potential for use of the additional stored soil water. This study was conducted to determine if N placement below the zone of organic matter or surface residue accumulation would reduce N immobilization and increase yields. The effects of N placement were evaluated by surface broadcasting and injecting below the soil surface 15N depleted NH4NO3 at 45 kg ha−1 in no‐till, stubble mulch, and plow fallow method systems on an Alliance silt loam (fine‐silty, mixed mesic Aridic Argiustolls) in a long‐term study in western Nebraska. Dry matter and grain yield, N concentration, N uptake, 15N concentration, 15N uptake, and fertilizer recovery in plant tissue were determined for fallow method and N placement during the 1985, 1986, and 1987 growing seasons. Dry matter and grain yield, N concentration, N uptake, 15N uptake, and fertilizer recovery were all significantly affected by fallow method during all 3 yr of the study, being highest in plow and lowest in no‐till with stubble mulch values intermediate. Nitrogen placement, however, had no effect on any of the variables in any of the tillage systems. In this environment, N immobilization does not appear to be a factor limiting use of additional stored soil water in reduced tillage systems because fertilizer recovery was equal for both placement methods in all three tillage systems.
Soil NO3‐N Analysis in CA(OH)2 Extracts by the Chromotropic Acid Method
Authors: Haby V. A. 
Published: July 2010

AbstractMethodology and instrumentation improvements have contributed to the increased use of nitrate‐nitrogen (NO3‐N) analysis of soil extracts for predicting crop N requirements. This research was conducted to determine the accuracy of the modified chromotropic acid (CTA) procedure for NO3‐N in saturated Ca(OH)2 extracts of soils. Sixty‐two soil sample extracts were analyzed for NO3‐N by the CTA method modified to eliminate oxidizing agents, NO‐2, and possible interferences from CI‐ and Fe. Results were compared with the same samples extracted and analyzed by use of the phenoldisulfonic acid method (PDSA). Comparison indicated the two methods were in close agreement (slope = 0.92 and r2 = 0.94). The graph of CTA NO3‐N concentration vs. absorbance at 410 nm followed Beer's Law. The modified CTA method, combined with Ca(OH)2 extraction of soil NO3‐N, is described in detail and presented as a standard.
Predicting Oil Infiltration and Redistribution in Unsaturated Soils
Authors: Cary J. W. , Simmons C. S. , McBride J. F. 
Published: July 2010

AbstractThe infiltration and redistribution of two viscous hydrocarbon oils, with viscosities 4.7 and 77 times greater than water, were observed in columns of moist silt loam and loamy sand soils. The time required for water and oil to infiltrate the two soils and the final volumetric liquid contents after 8 h were measured. These observations are compared to the results predicted by a simple multiphase flow code based on scaling oil flow to unsaturated soil‐water flow by using classical capillary theory and relative viscosities. A new function for describing the oil permeability was derived and, when used in the code, produced oil content distributions with depth that agreed reasonably well with those observed. The actual oil infiltration time was generally less than predicted, however. The flow of the two organic liquids into moist soils was found to be predictable, based only on classical soil‐water relations and the organic liquids' physical properties, under the imposed experimental conditions.
Effect of Low Electrolyte Concentration on Hydraulic Conductivity of Clay‐Sand‐Hydroxy Polymers Systems
Authors: Keren R. , Singer M. J. 
Published: July 2010

AbstractIron and Al oxides are ubiquitous in soils and have profound affects on soil structure. The objectives of this study were to (i) determine the effect of Fe‐ or Al‐polymers on saturated hydraulic conductivity (HC) of smectite‐sand mixtures at different percentages of the clay cation exchange capacity (CEC) at different sodium adsorption ratios (SAR) and solution electrical conductance (EC), and (ii) determine the reason for the observed effect. The HC of 5% smectite, 95% acid washed quartz sand (0.1 to 0.5‐mm diam.) with and without polymer additions was determined by leaching with SAR 5, 10, or 20 and EC 500, 100, 50, 10, 5, 3, 2, 1 solutions, and distilled water (DW) at pH 7.5. The HC of clay leached with SAR 5 solution decreased with a reduction in solution concentration from 500 to 1 molcm−3, after which clay was leached from the system and HC increased. No clay was leached from the column in the presence of hydroxy‐Al polymers in excess of 25% of clay CEC. Little HC reduction occurred at SAR 10 in the presence of hydroxy‐Al polymers. At SAR 20, HC of the clay‐sand mixtures decreased greatly, but no clay was observed in the leachate. Hydroxy‐Fe polymers produced similar effects, but to a lesser extent. The presence of hydroxy‐Fe polymers equivalent to 50% of CEC was insufficient to prevent clay dispersion and removal from the column when SAR 5 solution of 1 molcm−3 was replaced by DW. At 100% of CEC, Fe prevented clay dispersion when leached with SAR 5, 10, and 20 solutions. Iron was not as effective as Al‐polymers in preventing reduction of HC at SAR 10. The Al‐polymers appeared to be more effective than the Fe‐polymers because they bound clay particles into larger stable microaggregates than did the Fe‐polymers. A smaller percent of particles <2 µm was measured in the Al‐treated clay than the Fetreated clay. Both treatments increased the size of stable microaggregates compared to the untreated clay.