bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plot‐Scale Solute Transport in a Semiarid Agricultural Soil
Authors: Yasuda Hiroshi , Berndtsson Ronny , Bahri Akissa , Jinno Kenji 
Published: July 2010

AbstractIn semiarid areas, agricultural production is determined by limited water and nutrient supply. To develop efficient management practices, it is of importance to predict solute transport. In line with this, we present observed and calculated plot‐scale solute transport in an agricultural experimental field in northern Tunisia. A pulse of Br−‐tagged water was applied on the surface of two small field plots and leached under steady‐state soil water conditions. Solute samples were withdrawn through ceramic samplers at five different depths within each plot. The experimental data indicated a high degree of by pass or preferential flow within the small plots and nonsigmoid breakthrough curves, suggesting tailing phenomena and immobile fractions of soil water. The data were evaluated using the classical two‐parameter convection‐dispersion equation (CDE) and the four‐parameter non‐equilibrium convection‐dispersion equation (NECDE). Pore water velocities, v, and dispersion coefficients, D, were calculated by fitting the analytical solution of these two models to the breakthrough curves based on individual sample locations as well as using all samples in the plot simultaneously. None of the models could be fitted when data from all solute sampling depths were used in the optimization simultaneously. When using data at individual sample locations, the fit was somewhat better for the NECDE than for the CDE. The estimated values of D and v could be described by a power law relationship.
Mineral Effects on the Pyrolysis‐Field Ionization Mass Spectrometry of Fulvic Acid
Authors: Schnitzer M. , Kodama H. , Schulten H.‐R. 
Published: July 2010

AbstractFulvic acid (FA), physical mixtures of FA with quartz, Namontmorillonite, and kaolinite, and FA‐Na‐montmorillonite and FA‐kaolinite complexes were analyzed by pyrolysis‐field ionization mass spectrometry (Py‐FIMS). Use of this method made it possible to detect the following six major groups of FA components: carbohydrates, phenols, lignins, lipids, alkylaromatics, and N compounds, and to determine how the thermal evolution of these components was affected by the presence of minerals during pyrolysis. The thermal evolution of the six major FA components was delayed by the FA‐mineral mixtures but substantial retention of specific groups of FA components was shown only in the FA‐clay complexes. Thus, FA components retained by the clays in FA‐clay complexes were more thermostable than those in physical mixtures with FA. Pyrolysis‐field ionization mass spectrometry was found to have considerable potential for enhancing our understanding of the effects of the presence of minerals on the thermal behavior of FA.
Poultry Litter and Manure Contributions to Nitrate Leaching through the Vadose Zone
Authors: Adams P. L. , Daniel T. C. , Nichols D. J. , Pote D. H. , Scott H. D. , Edwards D. R. 
Published: July 2010

AbstractPastures are commonly fertilized with poultry litter or manure in northwestern Arkansas. We hypothesized that this practice may enhance NO3‐N movement to groundwater and wanted to ascertain the likelihood of common application rates causing excessive NO3‐N leaching. Our objective was to determine the effect of application rate of poultry litter or manure on NO3‐N concentration in vadose water under fescue (Festuca arundinacea Schreb.) plots as a function of depth and time. In August 1991, poultry litter was applied at 0 (control), 10 (PL10), and 20 Mg ha−1 (PL20) and poultry manure at 17.7 Mg ha−1 (PM20). In June 1992, we applied an additional 4.5 Mg ha−1 litter (PL5) to the PL10 plots and 3.8 Mg ha−1 manure (PM5) to PM20 plots. Pan lysimeters at the 60‐cm depth and suction‐cup lysimeters at 60 and 120 cm sampled soil water. The PL10, PL20, and PM20 treatments produced NO3‐N concentrations as high as 13, 54, and 41 mg L−1 at 60 cm. At 120 cm, NO3‐N reached 8, 24, and 37 mg L−1 for the PL10, PL20, and PM20 treatments. In 1992, the PL5 and PM5 treatments produced NO3‐N concentrations <1 mg L−1 at the 60‐ and 120‐cm depths. The recommended litter application rate in Arkansas is not more than 11.2 Mg ha−1 yr−1, split in two 5.6 Mg ha−1 applications. The PL10 and PL5 rates (similar to a maximum full‐year application plus a single split application) did not result in NO3‐N concentrations above the drinking water standard (10 mg L−1) at the 120‐cm depth.
Nutrient Runoff from Pasture after Incorporation of Poultry Litter or Inorganic Fertilizer
Authors: Nichols D. J. , Daniel T. C. , Edwards D. R. 
Published: July 2010

AbstractLand‐applied poultry litter can elevate N, P, and C concentrations in surface water runoff. This study tested the hypothesis that incorporation of surface‐applied poultry litter and inorganic fertilizer by rotary tillage would improve runoff quality from tall fescue (Festuca arundinacea Schreber) pasture. Captina silt loam (fine‐silty, siliceous, mesic Typic Fragiudult) plots with 5% slopes and fescue cover received 4.5 Mg litter ha−1 or fertilizer equivalent to 218 kg N ha−1 and 87 kg P ha−1. Litter and fertilizer were surface applied or incorporated 2 to 3 cm deep by rotary tillage. Simulated rainfall was applied 7 d later at 50 mm h−1 to produce continuous runoff for 0.5 h. Runoff concentrations and mass losses of measured constituents were not significantly different (α = 0.05) between surface‐applied and incorporated treatments. Runoff concentrations of total Kjeldahl N (TKN), NH3‐N, NO3‐N, total P (TP), PO4‐P, chemical oxygen demand (COD), and total suspended solids (TSS) averaged 32.5, 12.4, 1.1, 15.4, 10.4, 427.8, and 86.8 mg L−1 for litter treatments, and 37.5, 39.0, 2.6, 26.2, 26.1, 87.8, and 20.6 mg L−1 for fertilizer treatments. Mass losses of TKN, NH3‐N, NO3‐N, TP, PO4‐P, COD, and TSS averaged 2.8, 1.0, 0.1, 1.3, 0.9, 32.3, and 6.7 kg ha−1 for litter and 2.9, 3.4, 0.2, 2.0, 2.0, 12.7, and 2.1 kg ha−1 for fertilizer treatments. Runoff mass losses of TKN and TP were not significantly different between litter and fertilizer treatments. Averaged across all treatments and replications, mass losses of TKN and TP were 2.8 and 1.7 kg ha−1, representing 1.3% of applied N and 1.9% of applied P.
Transport of Zinc and Cadmium in Soils: Experimental Evidence and Modeling Approaches
Authors: Hinz C. , Selim H. M. 
Published: July 2010

AbstractThis study was conducted to assess the suitability of several isotherm equations in describing single solute and binary ion exchange of Zn and Cd in two soils (Windsor and Olivier). Isotherms were determined using batch methods for equilibration times of 1 and 14 d. Ion exchange batch experiments (based on NH4OAc extraction) were carried out at different heavy metal/Ca ratios. Several isotherm equations were capable of describing 1‐ and 14‐d sorption isotherms. However, the general Langmuir‐Freundlich was most suitable for describing single solute (Zn and Cd) isotherms, whereas the Rothmund‐Kornfeld ion exchange equation well described binary data sets (Zn‐Ca and Cd‐Ca). Miscible displacement experiments were carried out to study Zn and Cd transport in uniformly packed soil columns (10 cm in length) for different flow velocities. For Windsor soil, the general isotherm equation predicted Zn transport results adequately but not Cd results. Moreover, under conditions of variable ionic strength, the use of constant selectivity (equal affinity) for ion exchange provided consistently superior predictions of Zn and Cd transport than the Rothmund‐Kornfeld (variable affinity) approach. Attempts to predict Cd and Zn transport in Olivier soil, using several isotherms and ion exchange approaches, were not successful. Local equilibrium appeared dominant for Windsor soil, whereas nonequilibrium sorption behavior may be rate limiting for Zn and Cd transport in Olivier soil.
Network Modeling of Diffusion Coefficients for Porous Media: II. Simulations
Authors: Steele D. D. , Nieber J. L. 
Published: July 2010

AbstractGas diffusion often dominates constituent transport in porous media (PM) and is dependent on pore geometry, water content, and water distribution in PM. Network models of PM offer the ability to investigate the influence and interaction of pore‐scale PM properties and fluid properties on macroscopic properties of the system. This study was conducted to investigate the macroscopic relative gas diffusion coefficient vs. air‐filled porosity relationship or diffusion characteristic (DC) of PM using a network model. The network model was used to simulate DCs in wetting and drying PM containing air and water. A network size of nine by nine by nine spheres was used; increasing the network size to 19 by 19 by 19 produced essentially no change in the DC. The DC was independent of Henry's law gas‐liquid partition coefficient (H) for H values of 0.1, 1.0, and 5.0. The product HRw, where Rw is the ratio between the bulk gas‐ and liquid‐phase diffusion coefficients, strongly influences the DC when H values of 1000 to 10 000 are considered; this indicates that certain organic compounds have DCs independent of air‐filled porosity. Hysteresis in DCs was found in selected network cases, with the wetting DCs being greater than the drying DCs for most air‐filled porosities, in accord with some experimental results reported in the literature. Spatial correlation of network pore space was shown to bring the simulated DCs into better agreement with some experimental DCs.
Soil Amendments for Reducing Phosphorus Concentration of Drainage Water from Histosols
Authors: Coale F. J. , Porter P. S. , Davis W. 
Published: July 2010

AbstractRecently, the Everglades Agricultural Area (EAA) has been scrutinized by groups concerned with the impact of P‐enriched drainage water from organic soils (Histosols) on the ecology of adjoining wetlands. The objective of our research was to evaluate the effectiveness of soil amendments in reducing the P concentration in drainage water from an organic soil. Plastic cylindrical columns were filled with soil collected from a Pahokee muck (euic, hyperthermic Lithic Medisaprist). Three soil amendments were added to the soil columns: (i) a municipal drinking water purification facility waste material (“residual”), which is composed of CaO, Al2(SO4)3, and a starch‐based polymer; (ii) commercial agricultural dolomite [CaMg(CO3)2]; and (iii) commercial agricultural gypsum (CaSO4·2H2O). The amended columns were saturated for 60 d with an aqueous solution containing 5 mg P L−1 and then drained. The columns were then subjected to four P desorption cycles by saturating with distilled water and draining. Leachates were collected and analysed for total dissolved P (TDP). Residual and dolomite amendments reduced soil affinity for P sorption and resulted in a decrease in the quantity of soil P retained after repeated leachings. The net result from gypsum amendment was a small increase in P sorption capacity combined with an increased soil affinity for P. The reduced leachate TDP concentrations resulting from gypsum amendment were long lasting and were dependent on gypsum amendment rate. The effectiveness of gypsum amendments in reducing drainage‐water TDP concentrations needs to be evaluated under commercial agricultural field conditions.
A Steady‐State Model of Nutrient Uptake Accounting for Newly Grown Roots
Authors: Yanai Ruth D. 
Published: July 2010

AbstractA model of solute uptake that accepts root growth, water uptake, and soil solution concentration as time‐varying input is required to interactively link plant and soil processes. The advantage of the steady‐state approach to solute uptake over more exact numerical solutions lies in the independence of the mathematical solution to previous conditions. Uptake thus calculated can accommodate unpredictable changes in root growth and mortality, root density, water uptake rates, and sources and sinks of nutrients such as decomposition and leaching, as required in simulating plant growth for multiple seasons in a dynamic soil environment. Previous steady‐state models were improved by including nonlinear uptake kinetics and the contribution of new root growth to uptake. The correction for new root growth is most important for relatively fast‐growing plants and immobile nutrients. The importance of each model parameter, as indicated by sensitivity analysis, depends on the values of other parameters. For example, root surface area and uptake kinetics are important when solution concentrations at the root surface are high, while root length, water uptake rate, and diffusion become important when delivery of solute to the root surface is limiting. Because the limiting factors can vary with environmental and plant conditions, it is important to represent these aspects of nutrient uptake in modeling plant‐soil interactions. A consistent derivation of the improvements and the original model is appended.
Long‐Term Changes in Soil Carbon and Nitrogen Pools in Wheat Management Systems
Authors: Franzluebbers A. J. , Hons F. M. , Zuberer D. A. 
Published: July 2010

AbstractCrop management strategies that alter the timing, placement, quantity, and quality of crop residue input can affect the size, turnover, and vertical distribution of the active and passive pools of soil organic matter (SOM). Our objectives were to quantify long‐term changes in soil organic, soil microbial biomass (SMB), and mineralizable C and N in continuous wheat (Triticum aestivum L.), continuous wheat/soybean [Glycine max (L.) Merr.], and wheat/soybean‐sorghum [Sorghum bicolor (L.) Moench.] sequences under conventional tillage (CT) and no tillage (NT) with and without N fertilizer. A Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas was collected from a 9‐yr field study. Soil microbial biomass C (SMBC) and N (SMBN) were determined with the chloroform fumigation‐incubation method and mineralizable C and N were determined from 10‐d aerobic incubations at 25°C. More crop residue C input was retained as soil organic C (SOC), SMBC, and mineralizable C under NT than under CT. Soil organic C, SMBC, and mineralizable C at a depth of 0 to 50 mm were 33 to 125% greater under NT than under CT. Increasing cropping intensity increased SOC up to 22%, SMBC up to 31%, and mineralizable C up to 27% under NT. Differences in crop management systems significantly altered SMB and the associated mineralizable N level, which supplies crops with mineral N. High clay content soils of central Texas can be effectively managed to increase the active and passive pools of SOM using minimal fallow with NT.
Estimating Gross Nitrogen Mineralization and Immobilization Rates in Anaerobic and Aerobic Soil Suspensions
Authors: Smith C. J. , Chalk P. M. , Crawford D. M. , Wood J. T. 
Published: July 2010

AbstractZero‐order models for estimating gross rates of N mineralization (m) and immobilization (i) of NH+4 in soils were characterized by expressing the analytical solutions in a standard format. Three models of m were identified out of seven evaluated. One model was based on the solution of differential equations, and two on arithmetic mean data of ratios of labeled and total NH+4 pools. Data from well‐mixed anaerobic and aerobic soil suspensions amended with rice straw and labeled with (15NH4)2SO4 were used to compare the three models of m and four models of i for 56 d, with measurements every 7 d. Estimated rates of m declined during incubation, particularly during the first 21 d. Correction of m for remineralization of immobilized 15N in the anaerobic system using the total organic N pool (OT) had little effect, but the correction was more pronounced when the estimated active organic N pool (OT*) was used. Remineralization did not account for the observed decline in m during anaerobic incubation. Numerical modeling and nonlinear parameter estimation were also used to estimate m and i, with values being similar to analytical estimates for Days 0 to 7 (m) and Days 7 to 14 (i). The OT* comprised 10 to 11% of OT in both suspensions. Estimates of OT* were derived from the numerical analysis (anaerobic), or by assuming approximate isotopic equilibrium between the NH+4 (anaerobic) or NO−3 (aerobic) pools and the organic N pool following remineralization of immobilized isotope.
Genesis and Native Phosphorus Distribution in some Palexeralfs of Southern Spain
Authors: Smeck N. E. , Torrent J. , Barrón V. 
Published: July 2010

AbstractAlthough deeply weathered soils are common on stable landscapes in Mediterranean regions, little information exists regarding the quantities and depth‐distributions of native P forms in such soils. The objective of this investigation was to gather such information to determine the P status of Palexeralfs representative of southern Spain and to evaluate the applicability of current models and paradigms for describing pedogenic P transformations in such soils. Base saturation, clay distribution, absence of primary carbonates, distribution of secondary carbonates, extent of rubification, and properties of Fe (hydr) oxides all indicate that the Palexeralfs are polygenetic. Yellowishred lower sola are considered relicts attributable to deep leaching and weathering during Pleistocene pluvial periods, whereas pedogenesis is active in upper yellowish‐brown B horizons. Low total and labile P contents and the dominance of reductant‐soluble and organic P fractions throughout entire >3‐m sola indicate that soil P distribution attained a terminal steady state during the paleo‐climatic regime and has been little affected during the current semiarid climate. Although organic P (Po) is a major component of total P, stabilization of Po by Fe (hydr) oxides restricts Po mineralization and fosters the labile P deficient state of these soils.
Interactions and Weathering Losses of Iron and Phosphorus in Palexeralfs of Southern Spain
Authors: Smeck N. E. , Torrent J. , Barrón V. 
Published: July 2010

AbstractIn Palexeralfs of southern Spain, Fe (hydr)oxides are the dominant reservoir of P. Thus, knowledge of P and Fe (hydr)oxide interactions is vital to understanding P dynamics in these soils. This investigation focused on the effect of mineralogy and properties of Fe (hydr)oxides on P distribution and transformations by calculating Fe and P gains and/or losses during formation of Typic, Aquic, and Calcic Palexeralfs. Although differential x‐ray diffraction could not positively identify hematite, differential x‐ray diffraction data, redness ratings, and estimates of Al substitution indicated differences in Fe (hydr)oxide properties between upper yellowish‐brown horizons and lower yellowish‐red horizons in Typic and Aquic Palexeralfs. The properties are consistent with goethite in the upper yellowish‐brown horizons and goethite with a small amount of hematite in the lower yellowish‐red horizons. The yellowish‐brown horizons not only show net Pd (reductant‐soluble P) losses but also greater gains of Fed (citrate‐bicarbonate‐dithionite‐extractable Fe) than the yellowish‐red horizons resulting in lower Pd/Fed molar ratios. Due to the minimal mineralogical differences, we conclude the lower quantity of P occluded in the Fe (hydr)oxides in the yellowish‐brown horizons is not a function of Fe (hydr)oxide mineralogy and properties but availability of labile P.
Periodic Plowing Effects on Soil Properties in a No‐Till Farming System
Authors: Pierce F. J. , Fortin M.‐C. , Staton M. J. 
Published: July 2010

AbstractSoils in no‐tillage management are often plowed for crop rotation or to correct a pest or soil management problem. This study determined whether soil properties created by no‐tillage were retained or reestablished after plowing and return to no‐tillage. The study was conducted on a Capac loam (fine‐loamy, mixed, mesic Aeric Ochraqualf) in East Lansing, MI. In 1986 and 1987, one each of three treatments in no‐tillage since 1980 was plowed and subsequently returned to notillage (NTP86 and NTP87) and compared with conventional tillage (CT) and long‐term no‐tillage (NT). In all treatments, plowing, compared with NT, decreased bulk density by 0.17 to 0.28 Mg m−3, increased total porosity from 0.03 to 0.10 m3 m−3, increased macroporosity by 0.05 to 0.13 m3 m−3, and decreased microporosity by 0.03 to 0.05 m3 m−3. Wheel traffic increased bulk density 0.14 to 0.18 Mg m−3 in the plowed soils but only 0.04 Mg m−3 in the NT soil. Soil surface P, K, and organic C (OC) were redistributed in the surface 200 mm by plowing, but plowing did not eliminate stratification of chemical properties in the surface 50 mm. The NTP87 treatment enhanced mineralization of N over both CT and NT by 9.8 to 18.4 g N m−3 in the surface 50 mm in 1987. Residual effects were evident 1 yr after plowing. However, 4 to 5 yr after plowing, most soil properties had returned to levels of NT, although reestablishment of C and N in the surface remained lower than NT.
Relations between Soil Color and Landsat Reflectance on Semiarid Rangelands
Authors: Post Donald F. , Horvath E. H. , Lucas W. M. , White S. A. , Ehasz M. J. , Batchily A. K. 
Published: July 2010

AbstractThe reflectance of radiant energy from the earth's surface in sparsely vegetated arid rangelands is determined by the characteristics of the soil and geologic material on the land's surface. This study measured the color characteristics of earth surface materials collected from a semiarid rangeland in southeastern Arizona and compared these colors to digital numbers recorded by Landsat. Other parameters including particle size, slope, and vegetation were also evaluated, but the color characteristics of the fine earth soil and rock fragments measured with a colorimeter were most strongly correlated to Landsat digital numbers. The numerical values of the color components (hue, value, and chroma) for three different soil and rock fragment size fractions were related in a multiple linear regression equation to Landsat digital reflectance numbers. The R2 for Band 4 (0.5–0.6 µm), Band 5 (0.6–0.7 µm), Band 6 (0.7–0.8 µm), Band 7 (0.8–1.1 µm), and the sum of the four bands were 0.85, 0.69, 0.71, 0.68, and 0.75, respectively. The color of earth surface features in sparsely vegetated land areas should be precisely and accurately determined because of its very strong correlation with remotely sensed spectral data. The use of colorimeters to quantify the color of earth surface features will significantly help in evaluating remotely sensed data, particularly for land‐scapes in arid regions.
E. W. Hilgard and John Wesley Powell: Efforts for a Joint Agricultural and Geological Survey
Authors: Amundson Ronald , Yaalon Dan H. 
Published: July 2010

AbstractEugene W. Hilgard, professor of agriculture at the University of California, was a pioneer in agricultural, or soil, survey. In the mid to late 1880s, he vigorously sought to incorporate agricultural survey within the U.S. Geological Survey (USGS), then under the direction of Major John Wesley Powell. Hilgard recognized that agricultural survey fell within the USGSs original charge of land classification. Powell considered soil survey to be part of a much larger plan that was needed to develop the water and land resources of the arid American West. Through his early efforts, Hilgard was offered a position in the USGS (1886), which he declined, and he helped to make soil investigations part of the USGSs activities by the end of the 1880s. A bill to appropriate funds for the USGS to conduct an agricultural survey, supported by both Powell and Hilgard, was defeated by Congress in 1888. In 1889, Powell helped lead an effort to appoint Hilgard the Assistant Secretary of Agriculture (which Hilgard also declined), a position that would have given Hilgard power to help develop a national agricultural or soil survey. In the late 1880s and early 1890s, Hilgard was a strong supporter of Powell's attempts to transfer the USGS from the Department of Interior to the newly organized Department of Agriculture (USDA). Ultimately, Powell was attacked by western politicians, who rejected his plans for intensive mapping and land planning and for his attempts to join the USDA, effectively ending Hilgard's dream of a federal program of joint agricultural and geological surveys.