bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leaching and Water Flow Patterns in Every‐Furrow and Alternate‐Furrow Irrigation
Authors: Benjamin J. G. , Havis H. R. , Ahuja L. R. , Alonso C. V. 
Published: July 2010

AbstractDeep water percolation and chemical leaching is a recognized environmental problem with furrow irrigation. Alternate‐furrow irrigation (AFI) was hypothesized as a method to increase water‐use efficiency and decrease chemical leaching compared with every‐furrow irrigation (EFI). The SWMS_2D finite‐element model was used to investigate water and CaCl2 movement in EFI and AFI with furrow‐placed or ridge‐placed fertilizer bands. Model simulations were conducted for a Crook loamy sand (mixed, mesic, Ustic Torripsamment) and a Nunn clay loam (fine, montmorillonitic, mesic Aridic Argiustoll). Water isolation zones occurred with AFI and EFI that contributed little to overall profile drainage. The soil water contents after infiltration and redistribution were more uniform for EFI than for AFI for both soils. Water distribution was more uniform with AFI in the clay loam than in the loamy sand. Chemical movement was least with AFI and CaCl2 placement under the nonirrigated furrow. The greatest chemical leaching was predicted with furrow placement of CaCl2 and EFI. Results with CaCl2 suggest soluble chemicals or fertilizers placed under the nonirrigated furrow in loamy sand may not be available for plant uptake because the soil did not wet during irrigation. With either form of furrow irrigation, placement of a fertilizer in the ridge rather than in the furrow would decrease leaching of the fertilizer and keep the fertilizer in the root zone.
Foliar Deficiencies of Mature Southern Appalachian Red Spruce Determined from Fertilizer Trials
Authors: Joslin J. D. , Wolfe M. H. 
Published: July 2010

AbstractA field fertilization study employing additions of Ca, Mg, and N to a mature red spruce (Picea rubens Sarg.) stand was conducted at a high‐elevation site in southwestern Virginia. Statistically significant increases in needle weight (20% larger than controls) were observed after two growing seasons in treatments receiving Ca or Ca plus Mg. Significant foliar growth responses were accompanied by significant increases (20–60%) in foliar concentrations of Ca, Zn, Mg, and Mn in current‐year and 1‐yr‐old needles. Both Ca and Mg addition, alone or together, appear to have alleviated antagonisms by Al towards the uptake of these four cations. Both the foliar growth response (negative) and the foliar N concentration response to N addition were nonsignificant, a response consistent with the evidence for N saturation at this site. Vector analysis, correlation analyses, and literature evidence all provide support at this site for a foliar deficiency of Zn at a foliar concentration of 14 mg kg−1 and for a foliar and/or root deficiency of Ca at a current‐year needle concentration of 1700 mg kg−1. Foliar concentrations of Ca and Zn at or below these thresholds are common in southern Appalachian red spruce and may be related to its apparent growth decline in the higher elevations.
Nitrogen Losses and Lowland Rice Yield as Affected by Residue Nitrogen Release
Authors: Becker M. , Ladha J. K. , Ottow J. C. G. 
Published: July 2010

AbstractSynchronizing N supply from incorporated plant residues with N demand of rice (Oryza sativa L.) may increase the plant's N use efficiency and reduce soil N losses. This hypothesis was tested under flooded lowland conditions in a three‐season field experiment. Leguminous green manures and rice straw with various lignin to N ratios (L/N) and urea were compared using N release, rice N uptake, N use efficiency, grain yield, and total 15N balance as criteria. Basally applied urea resulted in high initial soil NH+4. Where residues were applied, exchangeable NH+4‐N varied as a function of L/N. Daily N uptake by rice peaked at ≈4 wk. Matching of soil NH+4‐N with daily rice N uptake was less apparent in urea and Sesbania rostrata Brem. S. Oberm. treatments than in the S. rostrata‐rice straw mixture treatment. Nitrogen‐15 balances indicated that the mismatch between supply and demand may have caused the measured N losses of 35% from urea and 6 to 10% from S. rostrata applied at 60 kg N ha−1. Synchronized N supply and rice N uptake resulted in negligible N loss and increased the portion of applied N remaining in the soil, but it did not cause a yield increase. Sesbania rostrata‐rice straw mixture depressed yield and N use efficiency in the dry season when yield potential was high. A residual effect was observed in the S. rostrata‐rice straw treatment in the third unfertilized crop, resulting in a 10% increase in grain yield. Apparently, synchronizing soil N supply with N demand by incorporating residues with suitable chemical composition may not immediately increase rice grain yields, but it improves long‐term soil fertility.
Soil Microbial Respiration at Different Water Potentials and Temperatures: Theory and Mathematical Modeling
Authors: Grant R. F. , Rochette P. 
Published: July 2010

AbstractIf ecosystem simulation models are to be used to study changes in C distribution under proposed changes in climate, then they must represent the effects of soil physical conditions upon microbial activity. Hypotheses for the effects of soil water content (θ) and temperature (Ts) on microbial oxidation rates were formulated into mathematical algorithms as part of the ecosys modelling program. Access to organic substrates by heterotrophic microbial populations was represented from competitive enzyme kinetics, which were presumed to be sensitive to θ. Access to O2 by obligately aerobic or facultatively anaerobic microbial populations was represented from O2 diffusion gradients and active uptake rates controlled by θ and Ts. Sensitivity to Ts of substrate hydrolysis and oxidation by heterotrophic microbial populations was modelled from an Arrhenius function. Rates of simulated respiration were tested against rates measured under laboratory and field conditions at different θ and Ts. Simulated CO2 fluxes were largest when θ = 0.6 to 0.7 of total porosity and declined to <0.2 of their largest values when θ declined to 0.2 or rose above 0.9 of total porosity. The sensitivity of simulated CO2 fluxes to θ was consistent with that measured during laboratory incubations, except in the range of 0.65 to 0.80 of total porosity, where sensitivity of measured fluxes was greater than that simulated. When θ was >0.8 of total porosity, simulated respiratory quotients rose above 1.0 to values consistent with those recorded elsewhere at high θ. Model hypotheses allowed simulated CO2 evolution rates to reproduce those reported from wheat residue during a 30‐d incubation at Ts from 0 to 20°C and ψs from −0.033 to −5.0 MPa. These hypotheses also allowed simulated changes in CO2 evolution rates attributed to changes in Ts and θ to reproduce those measured in the field during 60 d under barley.
Phosphorus Release Kinetics and Extractable Phosphorus after Long‐term Fertilization
Authors: Steffens D. 
Published: July 2010

AbstractIf different P fertilizers have been applied for a long time, it is difficult to measure the P availability. The objectives of this study were to investigate (i) the kinetics of soil P release by electroultrafiltration (EUF), (ii) extractable P using different soil extractants, (iii) plant P uptake, and (iv) the importance of considering both the P release kinetics and extractable P for plant P uptake prediction. This study was conducted with 15 European Alfisol topsoils with different histories of P and lime applications. The soils had received P as basic slag phosphate (BSP), superphosphate (SP), partially acidulated phosphate rock (PAPR), and phosphate rock (PR) for a long period. Plant P availability was measured in a 4‐yr pot experiment with different plants. Phosphorus release kinetics analyzed by EUF were better described by the Elovich equation than by other diffusion functions. The Elovich b values, which can be used as an index of release rate, ranged from 53.5 to 140.0 mg P kg−1 soil min−1. These b values were more closely correlated to cumulative plant P uptake (r = 0.96) than P extracted with water (r = 0.90), calcium acetate‐calcium lactate‐acetic acid (CAL) (r = 0.89), Mehlich 3 (r = 0.81), and double lactate (r = 0.79). Only Elovich b values in the PAPR and PR treatments were significantly correlated to cumulative plant P uptake (r = 0.92). The cumulative plant P uptake of the 15 soils was well predicted with the fitted equation: y = 27.8 + (0.40 CAL P) + (0.83b), r = 0.99, where y denotes the plant P uptake and b is the Elovich b value (mg P kg−1 soil min−1) and CAL P is the adsorbed P. This indicates that considering the b value as a parameter for P release and the amount of CAL‐extractable P for determining P availability following different fertilizer applications is a better estimation of plant P uptake than consideration of only one index of P availability.
Statistical Characterization of Dry Aggregate Strength Using Rupture Energy
Authors: Perfect E. , Kay B. D. 
Published: July 2010

AbstractDry aggregate strength, s, is important in tillage studies. Weibull's brittle fracture model is a widely accepted statistical approach for analyzing variability in s. Tensile strength, T, is commonly used as the measure of s in Weibull's model. However, compression and shear also occur during tillage. Use of specific rupture energy, E, involves no assumptions regarding the mode of failure. Furthermore, E can be related to tillage draft energy. Information is lacking on the statistical characterization of s using E. Our objective was to compare the performance of E and T as measures of s in Weibull's model. We determined E and T simultaneously for 1400 air‐dry aggregates from five size classes and seven cropping‐tillage treatments on a loam soil. Weibull's model fit equally well using either T or E. Model parameters estimated using T (αT and βT) were significantly correlated with those estimated using E (αE and βE). A log‐log relationship was established between αE and αT, with an intercept of −5.01 and a slope of 1.16. The β values were related by the equation: βE = 0.69βT, indicating less variation in s as measured by T than as measured by E. The α parameter was more sensitive to size and cropping‐tillage effects than the β parameter. The αE resulted in a better discrimination between size classes and cropping‐tillage treatments than did the αT. The αE decreased with increasing aggregate size and decreasing tillage intensity. The use of E in Weibull's model is recommended for the statistical characterization of s in tillage studies.
Adsorption of Thiamin (Vitamin B1) on Soils and Clays
Authors: Schmidhalter U. , Kahr G. , Evéquoz M. , Studer C. , Oertli J. J. 
Published: July 2010

AbstractRecent research suggests that thiamin applied to soils or coated onto seeds may stimulate plant growth. The behavior of thiamin in soils has not been investigated. Therefore, studies were carried out to determine how thiamin hydrochloride (3‐[(4‐amino‐2‐methyl‐pyrimidinyl)methyl]‐5‐(2‐hydroxyethyl)‐4‐methylthiazolium chloride hydrochloride) is adsorbed by 17 soils and three clays. The dominate mechanism in binding of thiamin is thought to be cation exchange with clay minerals and organic matter. In soils with low to medium organic matter content, thiamin adsorption occurred primarily on clay minerals and depended particularly on the amount and composition of the clay. Adsorption is species dependent (pKa1 [negative logarithm of the first dissociation constant] = 4.85) and takes place principally in the acidic pH range, probably with position 1′ of the pyrimidine ring. Adsorption equilibrium is attained in <30 min. Adsorption in all soils, and in kaolinite and illite clays, could be described by a one‐surface Langmuir isotherm at initial concentrations ranging from 16.3 to 995 µmol L−1. Adsorption by smectite in the same range was log‐linearly related to the equilibrium concentration. Extending the initial concentration range from 16.3 to 9890 µmol L−1 showed that a two‐surface Langmuir equation more adequately described adsorption in hydroxy‐interlayered vermiculitic and chloritic‐illitic soils, whereas a one‐surface Langmuir equation was found to be adequate in mixed layer‐smectitic soils. Only in the case of smectite clays is thiamin allowed to lie in a monolayer configuration parallel to the basal plane.
Nonequilibrium Transport of Atrazine through Large Intact Soil Cores
Authors: Gaber H. M. , Inskeep W. P. , Comfort S. D. , Wraith J. M. 
Published: July 2010

AbstractPreferential flow in heterogeneous soils may result in more rapid leaching of pollutants through soils than would be predicted using transport models based on the local equilibrium assumption (LEA). Our objectives were to evaluate nonequilibrium processes important to the transport of tritiated water (3H2O) and atrazine under varying pore water velocities and soil water contents, and to distinguish between transport‐related nonequilibrium (TNE) and sorption‐related nonequilibrium (SNE). Column experiments were performed using a 3H2O‐14C‐labeled atrazine pulse through intact soil cores (15.24‐cm diam., 30‐cm length) at pore water velocities of 0.12, 0.69, and 2.16 cm h−1 (θv ≈ 0.39) and at 0.74 cm h−1 (θv ≈ 0.44). The asymmetrical shape and the left‐handed displacement of 3H2O breakthrough curves (BTCs) as a function of pore water velocity and soil water content (θv) indicated that 3H2O was subject to TNE at only the 0.74 (θv = 0.44) and 2.16 cm h−1 pore water velocities. The asymmetrical shape and increased tailing of atrazine BTCs at all pore water velocities indicated that atrazine was influenced primarily by SNE at pore water velocities of 0.12 and 0.69 cm h−1, and a combination of both TNE and SNE at pore water velocities of 0.74 (θv ≈ 0.44) and 2.16 cm h−1. The convection‐dispersion equation based on the LEA was unable to predict atrazine BTCs at any pore water velocity. Although the nonequilibrium bicontinuum (two‐site/two‐region) model provided excellent fit to all atrazine BTCs, fits to the model cannot be used to separate between TNE and SNE when both mechanisms are operative. Results of this study confirm that TNE and SNE are important transport processes in naturally structured soils under conditions of relatively high pore water velocities and volumetric water contents.
Ancient Agricultural Soils in the Andes of Southern Peru
Authors: Sandor J. A. , Eash N. S. 
Published: July 2010

AbstractKnowledge about soil changes resulting from long‐term agriculture is important because agricultural influences on soil continue to increase in extent, intensity, and duration. Agricultural terraces in the Colca Valley, Peru, present an opportunity to study soils that have been cultivated for at least 15 centuries. Physical and chemical properties of soils were determined to explore possible effects of traditional agricultural practices on soils. Relative to nearby uncultivated Mollisols, agricultural A horizons are commonly 0.3 to 1.3 m thicker, contain buried organic‐matter‐enriched horizons, and are lower in bulk density. They also have more organic C and N and lower pH. Cultivated A horizons, particularly in agricultural terraces that have been abandoned for about four centuries, are enriched in P. Data suggest that P applied as fertilizer has been translocated deeply into soils during centuries of agriculture and accumulated in physically undisturbed B horizons. Agricultural practices inferred to be causal factors in changing these soils include terracing, tillage, fertilization, and irrigation. These ancient agricultural soils contain features characteristic of anthropic and plaggen epipedons and agric horizons.
Traffic Effects on Water Infiltration in Chisel‐Plow and No‐till Systems
Authors: Ankeny M. D. , Kaspar T. C. , Prieksat M. A. 
Published: July 2010

AbstractTraffic effects on pore structure and hydraulic properties of soils may be affected by site‐specific factors. The objective of this study was to determine if the effects of wheel traffic on infiltration rates in chisel‐plow and no‐till tillage systems differed among five Midwestern locations. Ponded and unsaturated (30‐, 60‐, and 150‐mm water tension head) infiltration rates were measured sequentially using infiltrometers after removing surface residues and the upper 2 cm of soil. Wheel traffic reduced ponded infiltration rates in both tillage systems at all locations, ranging from 95% in the chisel‐plow system in Iowa to approximately 55% in the chisel‐plow system in Missouri. Tillage systems significantly affected ponded infiltration rates at only two of the locations. At the Minnesota and Nebraska locations, no‐till reduced ponded infiltration rates in untrafficked interrows by 33 and 64%, respectively, compared with those in the chisel‐plow system. Ponded infiltration rates of trafficked interrows did not differ between tillage systems at any location. At the Iowa and Nebraska locations, the decrease in infiltration rate with an increase in tension head was greater for untrafficked interrows than for trafficked interrows in the chisel‐plow system. The large pores that drain at 30 mm of tension head accounted for a lower percentage of the water flow with ponding in trafficked interrows (73%) than in untrafficked interrows (88%). Infiltration rate comparisons between tillage systems should consider wheel traffic patterns.
Interpreting Differences among Hydraulic Parameters for Different Soil Series by Functional Characterization
Authors: Leummens H. , Bouma J. , Booltink H. W. G. 
Published: July 2010

AbstractUsing soil survey data for simulation modeling of water regimes and crop growth requires characteristic expressions for hydraulic characteristics of major soil horizons and soil series. It is unclear at present whether: (i) hydraulic functions based on parameter estimation techniques are adequate for simulations in macroporous soils, and (ii) to what extent different soil horizons and series can be pooled to reduce input data in simulation models. These questions were examined using two methods of expressing measured hydraulic conductivity data in computer simulations with previously validated crop models. Both hydraulic conductivity expressions used parameterized equations derived from one‐step outflow data for the −5.0 to −60.0 kPa pressure range. For the 0 to −5.0 kPa range, one method used hydraulic conductivities estimated by extrapolating the parameterized functions, whereas the second method used actual crust test data to account for macropore flow. Differences between the two methods were functionally tested by simulating maize (Zea mays L.) yields and fluxes below the root zone in three Costa Rican soil series, using the SWACROP model. Yields were significantly higher when considering structural porosity (Method 2), while fluxes were significantly lower. Thus, extrapolation of one‐step outflow data to conditions near saturation seems to be questionable. Using Method 2, maize yields and fluxes below the root zone were compared for three representative soil series to test whether they could be considered as one functional group of soils. Yield data indicated that two rather than one functional group should be distinguished. Flux data were similar for all three series, indicating that only one functional group was necessary.
Solubility of Hydroxy‐Aluminum Interlayers and Imogolite in a Spodosol
Authors: Su Chunming , Harsh James B. , Boyle Jeffrey S. 
Published: July 2010

AbstractInformation on the thermodynamic stability of minerals is essential when describing dissolution‐precipitation reactions. The solubility of imogolite in the Bs and BC horizons of a Spodosol influenced by volcanic ash in the Cascade Range, Washington, was studied using batch chemical equilibrium modeling at 25°C and 0.1 MPa pressure. Imogolite was found to be a major component of the clay fraction in the Bs and BC horizons of these soils using transmission electron microscopy (TEM) and selective dissolution techniques. Soil solutions were collected in 60‐, 120‐, and 180‐d intervals from soils (<2 mm) equilibrated in 0.01 M NaCl at initial pH 5.7 or 3.5 under conditions of both under‐ and oversaturation. The pH, total and labile (inorganic monomeric) Al, and labile (monomeric) Si were determined. We used a computer speciation model to calculate the activities of Al, H4SiO4, F, SO4, and other species including a soluble aluminosilicate complex. Soil solutions appeared to be in equilibrium with interlayer Al(OH)3 of 2:1 phyllosilicates and natural imogolite in the Bs and BC horizon soils, based on the most recent free energy values for synthetic and natural imogolites. The equilibrium activity of H2SiO4 was 10−3.71±0.08. Soil solutions were oversaturated with respect to gibbsite (3pH + log Al3+ = 8.73 ± 0.16). Interlayer Al(OH)3 appeared to have a higher solubility than well‐crystallized gibbsite. Assuming equilibrium with the soil solution, imogolite in this Spodosol was more soluble (log K25C [equilibrium constant at 25°C and 0.1 MPa] = 13.76 ± 0.25) than its synthetic counterpart (log K25C = 13.04 ± 0.14), but not different from a Japanese natural imogolite (log K25C = 13.56 ± 0.18).
Boron Sorption by Soil in the Presence of Composted Organic Matter
Authors: Yermiyahu U. , Keren R. , Chen Y. 
Published: July 2010

AbstractAlthough the organic matter content in cultivated soil is relatively low, its presence may have a significant effect on B distribution between the solid and liquid phases in soils. This study was conducted to determine the influence of organic matter in soil on B sorption and to test a B sorption model for soil in the presence of organic matter. The study was conducted on a loess soil (Calcic Haploxeralf). Mature compost, produced from the solid fraction of separated straw‐containing cattle manure, served as a simulation of organic matter. Boron sorption by soil‐composted organic matter mixtures increased as the organic matter content increased. At low pH levels (below pH 8), the sorption isotherms were linear regardless of the composted organic matter content. At the higher pH range, however, a deviation from linearity was observed. This deviation, which increased with pH, was related to the surface concentration of occupied sorption sites. Sorption B data from batch experiments were compared with results computed according to fitted adsorption coefficients (maximum B sorption and affinity coefficients that related to the binding energy). The B sorption capacity of the mixture increased with the composted organic matter content. The agreement between calculated values and experimental results indicates that the sorption model can be used to predict B sorption by soil‐organic matter mixtures.