bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infiltration of Simulated Rainfall: Tillage System and Crop Residue Effects
Authors: Unger Paul W. 
Published: July 2010

AbstractLow precipitation limits dryland crop yields in semiarid regions. Irrigation can increase yields, but declining water supplies, competition for water, and high pumping costs have caused an increased emphasis on water conservation in many regions. Water conservation, however, often is hindered by soil surface conditions that cause runoff, even from small rainstorms. The objective of this study was to determine the effect of tillage system and crop residue [winter wheat, Triticum aestivum L.; grain sorghum, Sorghum bicolor (L.) Moench] treatments on infiltration of simulated rainfall on Pullman (fine, mixed, thermic Torrertic Paleustoll) soil at Bushland, TX. Treatments were moldboard plowing plus disking, rotary tillage, sweep tillage with residues removed, sweep tillage with residues left in place, no‐tillage with residues removed, and no‐tillage with residues left in place. Different tillage systems caused significant differences in soil aggregate size, aggregate stability, organic‐matter concentration, initial water content, sediment loss during the rainstorms, bulk density, surface residue cover, and surface roughness. Compared with the no‐tillage treatments, moldboard plowing usually caused the greatest differences in the soil conditions. There was no close relationship, however, between any soil condition and infiltration. With limited residues, soil‐loosening tillage increased infiltration.
Influence of Oxalate Loading on Phosphorus and Aluminum Solubility in Spodosols
Authors: Fox T. R. , Comerford N. B. 
Published: July 2010

AbstractOrganic anions can increase the solubility of P and Al in soils and may influence nutrient availability and soil weathering. In Spodosols of the southeastern USA, oxalate has been identified as the dominant organic anion. Therefore, the objectives of this study were to examine the influence of oxalate on the release of inorganic P, organic P, and Al from A, and Bh horizons of two forested Spodosols from the Lower Coastal Plain. Oxalate loading rates ranging from 0 to 125 mmol kg‐1 soil were examined in a series of batch experiments using single, one‐time additions and repeated sequential additions of oxalate. Oxalate had a negligible effect on P and Al release from the A horizon soils. In contrast, oxalate had a large effect on both inorganic and organic P, as well as Al release from the Bh horizon soils. The effect of sequential additions of oxalate on P and Al release from these soils was found to be cumulative. The amount of Al or P released was primarily controlled by the cumulative oxalate loading rate. In addition, the manner of oxalate loading (single vs. sequential) had relatively little effect. At the same total, cumulative oxalate loading rate, the cumulative amount of Al or P released following sequential additions of oxalate at low concentrations were essentially the same as the amount released following a single addition of oxalate at a much higher concentration. This suggests that a continuous release of even small amounts of organic anions in forest soils could solublize large amounts of P and Al on an annual basis.
Analysis of Measured, Predicted, and Estimated Hydraulic Conductivity Using the RETC Computer Program
Authors: Yates S. R. , van Genuchten M. Th. , Warrick A. W. , Leij F. J. 
Published: July 2010

AbstractA nonlinear least‐squares optimization program, RETC, which uses empirical relationships for describing the water‐retention curve and predictive models for characterizing the unsaturated hydraulic conductivity relationship was used to analyze 36 unsaturated hydraulic conductivity distributions obtained from the literature for 23 different soils. By comparing the measured, predicted, and estimated relative conductivity for the group of data, the efficiency and accuracy of this approach for characterizing the soil hydraulic properties was determined. The analysis consisted of comparing measured, predicted, and estimated conductivities using three predictive methods and two simultaneous methods (which include known values of the conductivity). The results indicate that for this group of data, the best method for determining the model parameters that will accurately describe both the water retention and unsaturated hydraulic conductivity relationships is to use a simultaneous approach with either five or six parameters. It was also found that the predictive approach introduces a bias into the estimates of the unsaturated hydraulic conductivity and a predictive approach with scaling did not significantly improve the estimates of the unsaturated hydraulic conductivity.
X‐ray Tomography of Soil Water Distribution in One‐Step Outflow Experiments
Authors: Hopmans J.W. , Vogel T. , Koblik P.D. 
Published: July 2010

AbstractThe application of an optimization procedure to indirectly infer soil hydraulic functions from measured outflow in pressurized soil samples (one‐step outflow method), although widely used, has not been fully accepted. Reported problems are associated with the nonuniqueness and instability of the solution, as well as with the flow conditions that exist in the soil as a result of the high pressure difference across the sample. Computed tomography (CT) imaging of two soils with different texture was used to measure soil water distribution during the outflow process. Tomographic results show that unfavorable conditions exist if the soil is initially saturated. Richards' equation, which is employed in the optimization technique, assumes air continuity everywhere in the sample at all times. However, the ceramic plate at the outflow end of a pressurized saturated soil sample prevents the existence of a continuous air phase during initial desorption. We suggest that better results are obtained with the one‐step outflow method if the sample is initially unsaturated when pressure is applied.
Diffusion Kinetics of Multinutrient Accumulation by Mixed‐Bed Ion‐Exchange Resin
Authors: Yang Jae E. , Skogley Earl O. 
Published: July 2010

AbstractConventional batch or miscible‐displacement methods for studying nutrient release in the soil‐solution‐root continuum have been confined to single‐ion‐release reactions that result in the disintegration of concentration gradients due to excessive water and chemicals used in the procedure. The Phytoavailability Soil Test (PST) accumulates all nutrients simultaneously, as a function of diffusion to a mixed‐bed resin sphere. Objectives of this research were to compare kinetic models to describe empirically multinutrient accumulation by the PST method, and to test its sensitivity to conditions that influence diffusion kinetics. Accumulation of nutrients by resin was measured by inserting resin spheres into saturated soil pastes for 96 h at 25, 35, or 45°C, and stripping resin‐accumulated nutrients with HCl. Existing kinetic models all described multinutrient accumulation, except for NO3‐N. The parabolic diffusion law model consistently provided the best fit. Values for reaction rates and net reaction energy (Ean) were of similar magnitude to those reported in the literature. Positive values of ΔGo‡ and ΔHo‡ and negative values of ΔSo‡ (pseudo thermodynamic parameters) for K and P accumulation were similar to those reported for release of these nutrients. Significant relationships were found between rate constants of K, P, S, and NH4‐N and respective ion activities in soil solution. Accumulation of all nutrients was directly related to temperature, except NO3‐N, which was temperature and soil specific. These results suggest that the PST method has advantages over conventional methods for measuring nutrient dynamics, as it more closely simulates field conditions, while providing for multinutrient studies.
Transport of Naturally Occurring Dissolved Organic Carbon in Laboratory Columns Containing Aquifer Material
Authors: Dunnivant F. M. , Jardine P. M. , Taylor D. L. , McCarthy J. F. 
Published: July 2010

AbstractThe subsurface transport of ionic and nonionic pollutants may be strongly impacted by the movement of naturally occurring dissolved organic carbon (DOC) in aquifers. Thus, the adsorption, desorption, and transport of DOC in laboratory columns containing well‐packed aquifer material was investigated. Data showed that the breakthrough of DOC from aquifer columns was the result of complex adsorption reactions between DOC and the aquifer material. Breakthrough curves (BTCs) of the DOC were characterized by an initial rapid concentration increase followed by extended tailing to long times. The extensive tailing of the BTCs was attributed primarily to the slow adsorption kinetics of DOC to the aquifer material and the nonlinear nature of the adsorption isotherm. Independent experiments suggested that the size exclusion of DOC from aquifer pores was negligible. The time required to saturate the aquifer material with organic C was dependent on the influent DOC concentration, with lower organic influent levels requiring longer pulse durations to fully saturate the aquifer sediment with organic C. Hydrophobic constituents of the DOC were preferentially adsorbed while hydrophilic components were rapidly transported through the aquifer columns. Spectral analysis (light absorbance at 260 nm) of the column effluents confirmed that the composition of the mobile organic C changed during the breakthrough of DOC. Data from this investigation demonstrate that DOC can be mobile in soil systems, and emphasizes the need to evaluate the cotransport of pollutants by DOC.
Comparison between Pyrocatechol Violet and 8‐Hydroxyquinoline Procedures for Determining Aluminum Fractions
Authors: McAvoy Drew C. , Santore Robert C. , Shosa Jennifer D. , Driscoll Charles T. 
Published: July 2010

AbstractThere is currently considerable interest in quantifying concentrations of Al species in solution because of: (i) concern about the potential toxicity of inorganic forms of Al to plants and aquatic organisms, (ii) the need to better understand the processes contributing to soil development, and (iii) ongoing assessments of the biogeochemistry of Al. This study was conducted to compare the pyrocatechol violet (PCV) and 8‐hydroxyquinoline (oxine) methods for the determination of monomeric Al fractions. A strongly acidic cation‐exchange resin was used in automated PCV and nonautomated oxine procedures to separate aqueous Al into inorganic (labile) and organic (nonlabile) monomeric forms. Both synthetic and natural solutions were used in this analysis. Results showed good agreement between the two methods, suggesting that the PCV method is an acceptable alternative to the oxine method for the estimation of monomeric Al. In addition, the cation‐exchange column fractionation procedure was verified using an F ion‐selective electrode. Interference to the PCV method by Fe, F, and dissolved organic C was not significant across the range of solution concentrations studied.
Modeling Soil Organic Matter in Organic‐Amended and Nitrogen‐Fertilized Long‐Term Plots
Authors: Paustian Keith , Parton William J. , Persson Jan 
Published: July 2010

AbstractTo study the effects of organic matter and fertilizer additions on soil organic‐matter (SOM) dynamics, we analyzed results from a 30‐yr‐old Swedish field experiment, using the CENTURY model. Field treatments on a sandy clay loam included biannual addition (up to 4000 kg C ha−1) of straw, sawdust, and no organic additions, with and without N fertilizer (80 kg N ha−1), and green manure, farmyard manure, and bare fallow. Soil C and N, crop production (small‐grain and root crops), N uptake, and mineralization and immobilization of N were modeled and compared with field measurements. Changes in soil C and N, as much as 30% after 30 yr, were generally well represented by the model. Most of the treatment differences in SOM could be explained by the rate of organic‐matter input, its lignin content, and C/N ratio, plus the effect of N fertilizer on belowground C inputs. However, there appeared to be additional positive effects of N supply on SOM accumulation that were not fully explained by the model. The quality of organic amendments strongly influenced N uptake and crop productivity, through controls on N mineralization and immobilization. Mean annual N uptake ranged from a low of 3.1 g m−2 in sawdust‐amended soil to a high of 9.2 g m−2 in fertilized, straw‐amended soil. Simulated N losses accounted for 7 to 20% of total N inputs. Nitrogen‐balance estimates by the model were consistent with the observed data for four of the treatments, but treatments with low N availability appeared to have additional, unexplained N inputs.
Pedogenesis of Two Forest Soils (Kandiustults) Derived from Metamorphosed Granite in Korea
Authors: Cho Hi Doo , Mermut A. R. 
Published: July 2010

AbstractSoils derived from granite rocks occupy 66% of the land in Korea. Two soils from the southern part of Korea formed on metamorphosed granite under forest vegetation, containing high amounts of ferruginous chlorite, were studied to evaluate weathering and formation of clay minerals. The soils are deeply weathered, strongly acid, low in organic matter and cation‐exchange capacity (CEC), and the amounts of clay in the very thick Bt horizons are almost three times higher than in the BC horizons. Micromorphology of the thin O horizon showed common characteristics of moder humus and evidence of high biological activity. High contents of coarse grains and low plasma impart to the E horizon an enaulic‐related distribution pattern. The most striking micromorphological features are multilaminated, generally limpid ferriargillans in the Bt and BC horizons. While some chlorites are intact or partly weathered in the E and BC horizons, they are entirely weathered in the Bt horizons. High clay contents in the Bt horizons are not only due to clay translocation, but also to intensive in situ mineral weathering in this zone. The most significant pedogenic processes, as revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were formation of Fe oxyhydroxide and tubular halloysite from the weathering of chlorite and other primary minerals. Iron oxides imparted a typical red color to the soils. Total chemical analysis of clays revealed extensive loss of Ca, K, and Na and concentration of Fe and Al. Almost equal proportions of Al and Si oxides support a clay fraction dominated by halloysite and kaolinite. Mineralogical studies of clays in the Bt horizon showed that, while feldspars were partly weathered, chlorite, under a well‐drained, acid, humid temperate to semitropical environment, was completely weathered to kaolinite, halloysite, hematite, goethite, gibbsite, and a chlorite‐vermiculite intergrade, probably hydroxy‐interlayered vermiculite (HIV). Some dioctahedral mica appeared to be resistant in the soils.
Mapping Soil Salinity Using Calibrated Electromagnetic Measurements
Authors: Lesch S. M. , Rhoades J. D. , Lund L. J. , Corwin D. L 
Published: July 2010

AbstractA statistical modeling approach is presented that predicts spatial soil salinity patterns from aboveground electromagnetic induction (EM) readings. In this approach, EM readings are obtained from a field sampled on a uniform (centric systematic) grid. A small number of these sample sites are chosen for soil sampling, based on the observed EM field pattern. The salinity levels for these soil samples are determined and then the remaining nonsampled salinity values are predicted from the corresponding EM readings through a multiple linear regression equation. Experimental results suggest that this approach will work well in fields having low to moderate levels of soil textural variability. For example, 95% of the spatial variability in soil salinity within typical 16.2‐ha (40‐acre) cotton (Gossypium hirsutum L.) fields could be accounted for with only 36 soil samples, as opposed to the 200 to 300 soil samples typically required if no EM readings were available. This approach makes EM readings a more practical and cost‐effective tool by substantially reducing the number of soil samples needed for accurate mapping of spatial salinity patterns at the field scale.
Dry‐Soil Aggregate Stability as Influenced by Selected Soil Properties
Authors: Skidmore E. L. , Layton J. B. 
Published: July 2010

AbstractDry aggregate stability is an important soil physical property for evaluating tillage and wind‐erosion research. Research in this study was aimed at developing a model for predicting soil aggregate stability as influenced by intrinsic soil properties, with particular application to wind erosion. Aggregates from 10 Kansas soils with a wide textural range were tested periodically for stability during a 3‐yr period. The logarithm of aggregate stability was regressed against the intrinsic soil properties (geometric mean diameter of primary particles, specific surface area, water content at −1500 J/kg matric potential, and clay content). Clay content and water content at −1500 J/kg were both good predictors of mean aggregate stability. A resulting empirical model estimates mean aggregate stability from either clay or water content with coefficients of determination of 0.97 and 0.96, respectively. Further testing is planned by running the model with several independent data sets to estimate the probability of aggregate stability within specified limits for particular soils.
Miniaturized Method to Measure Carbon Dioxide Production and Biomass of Soil Microorganisms
Authors: Heilmann B. , Beese F. 
Published: July 2010

AbstractMicrobial activities and biomasses in soils exhibit steep gradients across short distances, forming microhabitats with different qualities. A methodological study was carried out to determine CO2 production of soil microorganisms in miniature. Soil samples (2–4 g) from 28 different soil types of southern Germany were incubated directly in a small glass ampoule within a 20‐mL gas‐tight syringe. A high correlation (r = 0.96) between CO2 production and heat output suggests that this micromethod is useful for the determination of CO2 respiration and the estimation of microbial biomass of small soil samples.
Alkalinity Measurements in Water Extracts of Calcareous Soils
Authors: Marion G.M. , Schlesinger W.H. , Fonteyn P.J. 
Published: July 2010

AbstractIn soil carbonate solubility studies, it is usually assumed that total alkalinity is equal to inorganic‐C alkalinity. Recent studies have raised questions about the validity of this assumption. This study reexamined previously published soil data from grass‐oak (Quercus spp.) woodlands and deserts to test the hypothesis that total alkalinity is equal to inorganic‐C alkalinity. Total alkalinity was measured with strong‐acid titration, while inorganic‐C alkalinity was calculated from pH and the partial pressure of CO2 (pCO2) measurements. Within the limits of error, calculated inorganic C alkalinity (Y) was equal to measured total alkalinity (X) (Y = 0.01 + 0.998X, r2 = 0.97). A recommendation was made for overdetermining the state of experimental systems in solubility studies; this allows one to check the internal consistency of experimental measurements, equilibrium constants, and model assumptions.
Thermally Driven Water and Octane Redistribution in Unsaturated, Closed Soil Cells
Authors: Prunty Lyle 
Published: July 2010

AbstractTemperature‐gradient influences on non‐aqueous‐phase liquid (NAPL) distribution in soil have received little detailed study, although there have been proposals to employ such gradients in remediation of NAPL contamination. The goal of this study was to characterize the time dependence and ultimate steady‐state distributions of water and octane after a constant temperature difference had been imposed across a volume of soil. Cells 5 cm long were packed with soil of initially uniform water and octane content. Temperatures at opposite ends of the cells were established and maintained at 40 and 6°C. Cells were destructively sampled at seven times from 1.5 to 100 h. Octane moved toward the cool end of the soil within 1.5 h. Water redistributed more slowly, but continued to do so for > 12.5 h. Water concentrating at the cool end of the cells resulted in reversal of the initial movement of octane at times > 1.5 h. The final steady‐state distribution of water in the cells had > 95% of the total water within the 3 cm nearest the cool end. In contrast, octane showed a peak at the location where water content dropped sharply. The interval 3 to 4 cm from the cool end contained 28% of the total octane in the cells. This study indicates that using thermal gradients effectively for concentrating NAPL will be a complex undertaking.
Macropore and Surface Seal Interactions Affecting Water Infiltration into Soil
Authors: Ela S. D. , Gupta S. C. , Rawls W. J. 
Published: July 2010

AbstractMacropores can increase water infiltration into soils whereas surface sealing decreases infiltration. Using Webster clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll) and Port Byron silt loam (fine‐silty, mixed, mesic Typic Hapludoll) soils, this study examined the effect of simulated rainfall on water infiltration into soils with earthworm (Aporrectodea tuberculata) and artificial macropores. Treatments included bare and covered soil surfaces, soils with and without macropores formed by earthworms, and soils with artificially formed macropores of 2‐, 3‐, 4‐, and 5‐mm diameter. During simulated rainfall, infiltration was measured by continuously monitoring the increase in container weight. Comparison of infiltration rates between bare and covered treatments showed that a surface seal developed on bare soils. The surface seal was effective in sealing visible macropores varying in diameter from 2 to 5 mm. Subsequent measurements with a disk permeameter at the surface and three subsurface depths showed that open macropores at the surface were ineffective in conducting water to deeper depths because they lacked continuity below the surface. Likewise, measurements of the water flux through individual earthworm macropores demonstrated that much of the increase in water flux due to macropores was due to the contribution of only a few of the visible macropores. The description of macropore size and number by themselves may be insufficient for developing models of water entry into soils containing earthworm macropores.
Changes in Aluminum and Phosphorus Solubilities in Response to Long‐Term Fertilization
Authors: Hetrick J. A. , Schwab A. P. 
Published: July 2010

AbstractContinuous fertilization with NH4 and phosphate fertilizers often has profound effects on the chemistry of soils. The resulting decreased pH and increased orthophosphate activities can impact the solid‐ and solution‐phase equilibria. The objective of this study was to determine the effect of long‐term fertilization of Al and P soil solution activities and to relate these activities to mineralogical components of the soil. Soil fertility treatments were established in Manhattan, KS, on a Smolan silt loam (fine, montmorillonitic, mesic Pachic Argiustoll) and annually received high rates of NH4NO3 and superphosphate for >40 yr. High rates of NH4 applied to these soils decreased the soil pH from 6.9 to 4.1, and it was anticipated that the activities of Al and P might have been affected by pH changes. Solubilities of Al and P were measured after equilibrating soils for 36 d in 0.01 M CaCl2, and ionic activities were calculated. Apparent equilibria with amorphous Al(OH)3 and hydroxyapatite were observed in unfertilized soils. Phosphorus fertilization did not affect Al solubilities but increased P activities to apparent equilibrium with tricalcium phosphate and Al phosphates. The mean ion activity product for AlPO4·nH2O was −2.29 ± 0.38 compared with −2.50 for AlPO4 (variscite) and −0.92 for AlPO·2H2O (amorphous). Aluminum solubilities in the N‐treated soils were undersaturated with respect to Al oxides, Al oxyhydroxides, Al hydroxides, and all phosphate minerals but may have been in equilibrium with montmorillonite.