bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial Variability of Soil Actual and Potential Acidity in the Mangrove Agroecosystem of West Africa
Authors: Sylla M. , Stein A. , van Mensvoort M. E. F. , van Breemen N. 
Published: July 2010

AbstractSpatial variability of soil acidity in coastal lowlands results from a complex interaction of climate, coastal morphology, river hydrology, vegetation, landform, and tidal flooding. This study was conducted to determine whether the causal factors of soil acidification can be related to soil total actual acidity (TAA) and total potential acidity (TPA) in 12 sites selected along four river basins in West Africa. A hierarchical framework was designed corresponding to the scale at which each factor has the greatest influence on acidification. In the dry season of 1991, soil samples to be analyzed for TAA and TPA were taken from three strips within each river basin, perpendicular to the river at different distances from the mouth, following a 40 by 20 m grid, at five soil depths. The contribution of the different causal factors of acidity spatial variability was analyzed with a nested analysis of variance (ANOVA) and related to the hierarchical framework. Geostatistics were used to study spatial variability at the most detailed scale. We defined main ecoregions identified between watersheds at the macroscale, subenvironments identified with distance from the river mouth within watersheds, and zones identified with positions within toposequences. Practical implications for water management in acid sulfate were developed. At the macroscale, a broad subdivision of the study area into two ecoregions was possible, at the mesoscale, site position along rivers significantly predicted a river‐dependent longitudinal variability of soil acidity, whereas at the microscale, kriged maps showed different patterns of soil acidity.
Furrow Irrigation Water‐Quality Effects on Soil Loss and Infiltration
Authors: Lentz R. D. , Sojka R. E. , Carter D. L. 
Published: July 2010

AbstractIrrigation‐induced erosion is a serious problem in the western USA where irrigation water quality can vary seasonally and geographically. We hypothesized that source‐water electrical conductivity (EC) and sodium adsorption ratio (SAR = Na/[(Ca + Mg)/2]0.5, where concentrations are in millimoles of charge per liter) affect infiltration and sediment losses from irrigated furrows, and warrant specific consideration in irrigation‐induced erosion models. On a fallow Portneuf silt loam (coarse‐silty, mixed, mesic Durixerollic Calciorthid), tail‐water sediment loss was measured from trafficked and nontrafficked furrows irrigated with waters of differing quality. Treatments were the four combinations of low or high EC (0.6 and 2 dS m‐1) and low or high SAR (0.7 and 12 [mmolc L‐1]0.5). Slope is 1%. Twelve irrigations were monitored. Each furrow received two irrigations. Main effects for water quality, traffic, and first vs. second irrigations were significant for total soil loss, mean sediment concentration, total outflow, net infiltration, and advance time. Average tail‐water soil losses were 2.5 Mg ha‐1 from low EC/low SAR furrows, 4.5 Mg ha‐1 from low EC/high SAR furrows, 3.0 Mg ha‐1 from high EC/high SAR furrows; and 1.8 Mg ha‐1 from high EC/low SAR furrows. Elevating water EC decreased sediment concentration from 6.2 to 4.6 g L‐1, but increasing SAR increased sediment concentration from 6.2 to 8.7 g L‐1. Net infiltration decreased 14% in high SAR compared with low SAR treatments. Soil loss increased 68% for second irrigations, and net infiltration fell 23% in trafficked furrows, but water‐quality effects were the same. Water quality significantly influenced infiltration and erosion processes in irrigated furrows on Portneuf soils.
Fluidized Bed Combustion Bottom‐Ash Effects on Infiltration and Erosion of Variable‐Charge Soils
Authors: Reichert José Miguel , Norton L. Darrell 
Published: July 2010

AbstractHighly weathered soils generally maintain low electrolyte levels (EC) in soil solution, which, along with raindrop impact, causes aggregate dispersion and enhanced erosion. This study was conducted to determine if application of fluidized bed combustion bottom ash (FBCBA) could control erosion of variable‐charge soils. Seven highly weathered soils (six Oxisols and one Ultisol) were prewetted and then subjected to high‐intensity rainfall (110 mm h‐1) for 2 h. The FBCBA was surface applied at a rate of 5 Mg ha‐1. Infiltration, runoff, and erosion were measured throughout the rains. The FBCBA increased EC and pH of the soil solution, because it contained CaO (23%), Ca(OH)2 (3%), and CaSO4 (73%). Steady‐state infiltration rates (Is) ranged from 7.2 to 54.8 mm h‐1 for the control and from 9.5 to 44.4 mm h‐1 for the FBCBA. The FBCBA had either a favorable, an unfavorable, or no effect on the parameters tested, depending on the soil. On soils with a favorable response to FBCBA, Is was increased by 1.7 to two times, total runoff reduced by two times, and total erosion reduced by 2.2 to 2.4 times. On soils with an unfavorable response, Is was decreased by 1.2 to 1.6 times, total runoff increased by 1.2 to 1.6 times, and erosion increased by 1.6 times. The increased infiltration and reduced erosion and runoff occurred only for soils that had low pH (ΔpH ≤ 0.6) and negative charge (≤ 2.0 cmolc kg‐1). Unfavorable responses were found when ΔpH was >2.1, charge increase was at least 6.8 cmolc kg‐1, and final pH was >9.
Organic Matter Fractions from Organically and Conventionally Managed Soils: I. Carbon and Nitrogen Distribution
Authors: Wander M. M. , Traina S. J. 
Published: July 2010

AbstractChemical and physical fractionation techniques were used to study the effects of organic and conventional management practices on soil organic matter (SOM) characteristics. We isolated SOM from: (i) organic animal‐based, manure‐amended (ORG‐AN), (ii) organic cash‐grain‐based, cover cropped (ORG‐CC), and (iii) conventional, cash‐grain‐based (CONV) rotations. We quantified the total C and N contents of humin (HN) and humic substances (HS), and light (LF), heavy (HF), fine organo‐clay, and organo‐sand fractions. Management changed the quantity and distribution of C and N in physically and chemically isolated fractions. The ORG‐CC soil had significantly greater quantities of C in its HN, HS, LF, and HF fractions than the CONV soil. Management impacted the distribution of C and N only in the LF fraction. The ORG‐CC had a larger percentage and proportion of C and N in its LF than the other soils. The percentage of soil N in HS was higher in the ORG‐AN and ORG‐CC than in the CONV soil. Even though the quantity of N in the CONV's HN equaled the other soils, it had the highest percentage and proportion of N allocated to this fraction. Farming systems did not significantly alter the C and N contents of HS or the quantity of C associated with selected particle‐size fractions; however, the C content of fine clay isolated from aggregated soil was significantly greater than the C content of clay isolated from loose soil. By isolating macroorganic matter (LF) in concert with HS and HN fractions, we were able to assess management practice impacts on SOM characteristics.
Drip Irrigation in Heterogeneous Soils: Steady‐State Field Experiments for Stochastic Model Evaluation
Authors: Or Dani 
Published: July 2010

AbstractIn many drip‐irrigated fields, spatial variations in soil properties induce variations in wetting patterns about the drippers, resulting in uncertainty in the interpretation and use of sensor‐based soil water information. In previous work, analytical tools to quantify the effects of spatial variation in soil hydraulic properties on wetting patterns were developed. The objective of this study was to validate some of these analytical results. Following the characterization of the soil hydraulic properties in the study site, water was supplied from arrays of surface and subsurface point sources at constant flow rates. About 160 tensiometers and 100 time domain reflectometry (TDR) probes were installed at fixed positions relative to the source (for each flow rate and source location) and were monitored daily. The resulting spatial moments of matric head and water content were compared with analytical model predictions. Results revealed a large discrepancy between measurements and predictions based on the field‐estimated variability in α (the exponent of the unsaturated hydraulic conductivity function). Better agreement was obtained when a reduced variability in α was used. This suggests that soil hydraulic properties measured under ponding may be biased by the presence of large pores. Overall, the analytical model was capable of using information on the (permanent) spatial variability in soil hydraulic properties to predict the variability in flow attributes. However, even with better soil characterization and smaller soil variability, model predictions should be viewed as first approximations of the extent of variability in matric head and water content.
A Quasi‐Analytical Model for Soil Solute Movement under Plant Water Use
Authors: Connell L. , Haverkamp R. 
Published: July 2010

AbstractSolute accumulation in surface soils through capillary rise transport, driven by evaporation, is a serious management issue. In particular, for soils under a saline shallow water table, salt buildup can have a serious detrimental impact on agricultural productivity. For vegetated surfaces, evaporation is the sum of water loss directly from the surface and that taken up by plants for transpiration. We developed a procedure for the prediction of solute migration in soils under plant water use in a shallow water‐table environment. For this situation, the advection‐dispersion equation is shown to be linear with nonconstant coefficients. To solve this equation, the root zone is divided into a series of layers and for each layer the governing equation is approximated by a constant coefficient form with layer‐averaged values for properties. We derived a solution to this equation in Laplace space, which is coupled to its neighbors by requiring the flux and concentration be constant across the layer boundaries. At each time level, a matrix system is posed for the equation coefficients and concentration resolved by numerical inversion from Laplace space. The good agreement between model predictions and solutions obtained from a finite‐element analysis indicates that the procedure presented is of high accuracy and could offer computational savings over purely numerical procedures. The multilayer approach allows the representation of nonuniform plant water use functions, dispersivities, soil properties, and initial conditions.
Release Rates of Phosphorus, Ammonium, and Potassium in Clinoptilolite‐Phosphate Rock Systems
Authors: Allen E. R. , Hossner L. R. , Ming D. W. , Henninger D. L. 
Published: July 2010

AbstractControlled release of P, NH4, and K can be accomplished in synthetic soils through dissolution and cation‐exchange reactions by phosphate rock (PR) and the zeolite mineral, clinoptilolite (Cp). The power‐function equation has previously been found to adequately describe transport kinetics of the nutrient release process. Research was conducted to evaluate factors affecting P, NH4, and K release rates in Cp‐PR systems. Data was collected using a continuous‐flow thin‐disk technique. Results were evaluated with the power‐function equation. Materials included a Texas Cp and North Carolina and Tennessee PRs. Variables examined included the Cp/PR ratio, the mole fraction of NH4 and K on the Cp, and the type of PR. The power‐function model indicated that initial release rates and cumulative nutrient release in Cp‐PR mixtures were increased by using a higher Cp‐PR ratio and by using a more reactive PR. Nutrient release rates were also affected by changes in the proportion of NH4 and K occupying Cp exchange sites and reflected ion‐selectivity characteristics of Cp. The results indicate that Cp and PR may be used to obtain a controlled release of NH4, P, and K in a synthetic soil.
Soil Carbon Dioxide Fluxes from Conventional and No‐Tillage Small‐Grain Cropping Systems
Authors: Fortin M.‐C. , Rochette P. , Pattey E. 
Published: July 2010

AbstractConversion to conservation tillage systems increases soil C content by reducing soil erosion and the rate of organic matter oxidation. We hypothesized that these effects could impact soil emission of CO2. This study (i) determined if CO2 emissions were reduced in the first years after conversion to no‐tillage (NT) relative to conventional tillage (CT), (ii) evaluated whether differences in soil CO2 emissions between tillage treatments were related to soil temperature differences, and (iii) determined if soil CO2 emission measurements provided an early estimate of soil management practice impact on soil organic C. In 1992 and 1993, CT and NT plots were planted to small‐grain cereals in Ottawa, Ontario, on a Dalhousie silt loam (mixed, mesic, Typic Endoaquoll). Fluxes were measured using closed chambers connected to a portable CO2 analyzer. During growing season 1992, the CO2 emissions varied from 0.05 to 0.18 mg CO2 m−2 s−1 with an average of 0.12 mg CO2 m−2 s−1 for CT and of 0.10 mg CO2 m−2 s−1 for NT. In 1993, the CO2 emissions varied from 0.06 to 0.35 mg CO2 m−2 s−1 with an average of 0.15 mg CO2 m−2 s−1 in both tillage treatments. Differences in soil CO2 fluxes between treatments were related to differences in soil temperature (r2 = 0.62), giving an estimate of 75 g C m−2 yr−1 difference in organic C transfers to the atmosphere between CT and NT. These results were validated using an independent estimation derived from long‐term field experiments. Thus, soil CO2 flux measurements using dynamic closed chambers can provide early estimates of soil management impacts on soil organic C.
Ion‐Chromatographic Analysis of Low Molecular Weight Organic Acids in Spodosol Forest Floor Solutions
Authors: Krzyszowska Anna J. , Vance George F. , Blaylock Michael J. , David Mark B. 
Published: July 2010

AbstractLow molecular weight organic acids (LMWOA) from root exudates, decomposing organic matter, and other sources are important lignads involved in solution complexation reactions as well as ligand exchange reactions at mineral surfaces. The purpose of this study was to (i) develop an ion chromatography method that could be used to determine LMWOA in soil solutions from Spodosols, (ii) assess methods for preserving LMWOA in soil solutions, and (iii) evaluate LMWOA concentrations in forest floor solutions during a growing season. Solutions were collected weekly from zero‐tension lysimeters installed within the forest floor (forest floor leachate collectors). Limits of quantitation for acetic, formic, malonic, oxalic, phthalic, and citric acids were 0.35, 0.14, 0.43, 0.41, 0.07, and 0.04 µM, respectively, which in some cases are an order of magnitude lower than reported in previous studies. Freezing soil solutions after filtering resulted in the best recoveries (between 90 and 100% for all LMWOA); other methods of preservation, such as filtering alone and filtering and storing at 4°C, resulted in lower recoveries. The average concentrations of LMWOA in the forest floor solutions were 10 µM acetic acid, 0.7 µM formic acid, and 3.3 µM oxalic acid. Dissolved organic C from the forest floor contained a maximum concentration of 2.0% acetic acid, 0.01% formic acid, and 0.15% oxalic acid. There were no apparent temporal patterns in LMWOA concentrations, except for a decrease in LMWOA concentrations from late September to a minimum in October.
Moment Analysis to Estimate Degradation Rate Constants from Leaching Experiments
Authors: Das B. S. , Kluitenberg G. J. 
Published: July 2010

AbstractFirst‐order degradation rate constants (γ) are often estimated from the results of solute leaching experiments by using curve‐fitting procedures. However, uniqueness problems can make curve‐fitting a challenging task if multiple parameters are estimated simultaneously. Several attempts have been made to compute γ by employing batch degradation theory to analyze the results of leaching experiments. This theory requires an estimate of the mass recovery fraction (MRF) and the degradation time. The degradation time is replaced with an average solute travel time when batch theory is applied to the results of a leaching experiment. This approach is flawed because the simultaneous occurrence of sorption, dispersion, and convection confounds the time available for degradation in a leaching experiment. We have used statistical moments to show that when degradation follows first‐order kinetics, the degradation time is an adjusted convection time (ACT). It is defined as the harmonic mean of m1/R and the convection time (L/v), where m1 is the first moment of the breakthrough curve (BTC), R is the retardation factor, L is the length of the soil column, and v is the pore water velocity. The adjustment in the convection time scale is required because of the simultaneous occurrence of dispersion and degradation. We show that these two processes interact to reduce the true convection time for the leaching event (ACT < L/v). We have tested our result by generating artificial BTCs with known values of γ and then successfully estimating γ by obtaining the MRF and ACT from the generated BTC. We have outlined a procedure to estimate γ from the information generated in a typical leaching experiment.
Sodium‐Copper Exchange on Wyoming Montmorillonite in Chloride, Perchlorate, Nitrate, and Sulfate Solutions
Authors: Zhang Z. Z. , Sparks D. L. 
Published: July 2010

AbstractThe effect of anions on the Na‐Cu exchange reactions on montmorillonites is not well understood and discrepancies exist in the literature. This study was conducted to examine the role of anions on the Na‐Cu exchange reaction on Wyoming montmorillonite. The copper exchange capacity (CuEC) and Na‐Cu exchange reactions on Wyoming montmorillonite were studied in Cl−, ClO−4, NO−3, and SO2−4 solution media at a constant total metal charge concentration of 0.0200 molc L−1. We found that the values of CuEC were similar in Cl−, ClO−4, NO−3, and SO2−4 electrolyte media, and the quantity of Cu extracted by Na2‐EDTA solution was only 1.0 to 1.2% of the CuEC and was not affected by anions. The apparent adsorbed metal charge, Q, and Vanselow selectivity coefficients, Kv, were determined across a wide range of exchanger phase composition, with Cu2+ occupying 30 to 95% of the charge sites. We found that the values of Q increased with Cu saturation in each of the anionic media, and the increase was not affected by anions. The increase in Q was attributed to decrease in negative adsorption of anions. We observed that Kv was independent of exchanger composition in each of the four anionic media. The values of Kv in the SO−4 medium were lower than those in other anionic media because of the complexation reaction between Cu2+ and SO2−4. The data showed that Cu2+ ions were not specifically adsorbed under our experimental conditions and that the exchanger phase behaved as an ideal mixture. It was concluded that no detectable monovalent complexes such as CuCl+ and CuNO+3 were adsorbed on Wyoming montmorillonite in the Na‐Cu exchange reaction.
Origin and Properties of Smectite in Loess‐derived Soils of Western Ohio
Authors: Burras L. , Smeck N. E. , Bigham J. M. 
Published: July 2010

AbstractExpanding phyllosilicates have been identified in soils of western Ohio for >40 yr, yet little is known about the origin or properties of these clays. The objective of this study was to ascertain the origin of the smectite component of the expanding phyllosilicates from a representative Udalf‐Aqualf‐Aquoll toposequence derived from Peoria loess in western Ohio. The content, distribution, and layer charge of the smectite were evaluated using chemical and x‐ray techniques. Results from these analyses show the smectite present in these soils is a medium‐charge dioctahedral species. Alkylammonium chloride exchange indicated the layer charge of the smectite is between 0.36 and 0.38 mole charge per half unit cell. The smectite generally comprised 50% or more of the total clay content in the B and C horizons of each pedon. The presence of high contents of smectite in the C horizons of all three pedons demonstrates a detrital origin and suggests that Peoria loess was an important source of expanding phyllosilicates in soils of western Ohio.
Influence of Hydroperiod on Litter Conversion to Soil Organic Matter in a Floodplain Forest
Authors: Lockaby B. G. , Wheat R. S. , Clawson R. G. 
Published: July 2010

AbstractLignin and cellulose dynamics were followed for 23 mo during degradation of foliar litter in an oligotrophic floodplain forest located in south Georgia. Litter was placed in microcosms, which were subjected to hydroperiod variation in terms of duration and nutrient inflow. Treatments were compared in terms of rates of lignin and cellulose loss and the degree to which a theoretical asymptotic value of the ratio of lignin to lignin plus cellulose (LCI) was approached. Flooding strongly stimulated loss rates of lignin and cellulose, and results suggest that a single, relatively brief flooding event promoted loss rates to the greatest extent. The elevation of N inflow reduced lignin degradation rates compared with other flooding treatments. Observed temporal patterns of LCI ratios did not follow theorized patterns and may suggest that, in warm climates such as south Georgia, lignin loss is greater than in boreal forest systems where theoretical LCI relationships were developed.
Improved Soil Particle‐Size Analysis by Gamma‐Ray Attenuation
Authors: Oliveira J. C. M. , Reichardt K. , Vaz C. M. P. , Swartzendruber D. 
Published: July 2010

AbstractThe size distribution of particles is useful for physical characterization of soil. This study was conducted to determine whether a new method of soil particle‐size analysis by gamma‐ray attenuation could be further improved by changing the depth and time of measurement of the suspended particle concentration during sedimentation. In addition to the advantage of nondestructive, undisturbed measurement by gamma‐ray attenuation, as compared with conventional pipette or hydrometer methods, the modifications here suggested and employed do substantially decrease the total time for analysis, and will also facilitate total automation and generalize the method for other sedimentation studies. Experimental results are presented for three different Brazilian soil materials, and illustrate the nature of the fine detail provided in the cumulative particle‐size distribution as given by measurements obtained during the relatively short time period of 28 min.