bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of the Glover Solution with the Simultaneous‐Equations Approach for Measuring Hydraulic Conductivity
Authors: Amoozegar A. 
Published: July 2010

AbstractThe Glover solution and the simultaneous‐equations approach have been suggested for determining the saturated hydraulic conductivity (Ks) of the vadose zone by the constant‐head well permeameter technique. The objective of this paper is to examine the two procedures and discuss the uncertainty associated with calculating Ks by the simultaneous‐equations approach (referred to as Kfs) as compared with using the Glover solution. Two flow regions are identified with the constant heights of water, H1 and H2 (H2 > H1), at the bottom of an auger hole of radius r during measurements of steady state flow rates, Q1 and Q2. The Ks's over the distances H1 (lower region), H2 – H1 (upper region), and H2 (entire wetted zone) at the bottom of the hole are designated as Ksl, Ksu, and Ksc, respectively. Using the Glover solution for calculating Ksl and Ksc for a homogeneous and isotropic medium, an equation is developed for calculating Ksu based on Q1, H1, Q2, H2, and r. This equation is found to be very similar to the equation for calculating Kfs by simultaneous‐equations approach. It is shown that Ksl > Ksc whenever the Kfs value is negative. Conversely, the matric flux potential calculated by the simultaneous‐equations approach (φm) is negative only when Ksc > Ksl. This is significant because, in the simultaneous‐equations approach, the Kfs value will not be acceptable when φm is negative. The Glover solution (i.e., equation to calculate Ksc or Ksl) is applicable to both homogeneous and heterogeneous soils and does not yield a negative value, whereas the simultaneous‐equations approach can only yield reliable results for homogeneous and isotropic media.
Field Evaluation of Soil Hydraulic Property Changes Caused by Surge Water Application
Authors: Saleh A. , Hanks R. J. 
Published: July 2010

AbstractSurge flow irrigation was developed, in part, to take advantage of the property of some soils whereby irrigation water is more evenly distributed along the field by applying the water in “surges” (on and off cycles) instead of continuously. Thus, if water advances more during the second on‐time of irrigation than the first, there must be some change in soil properties during the previous off‐time. Three soils were used in this study: Nibley silty clay loam (a fine, mixed, mesic Aquic Argiustoll), Millville silt loam (a coarse‐silty, carbonatic, mesic Typic Haploxeroll), and Kidman sandy loam (a coarse‐loamy, mixed, mesic Calcic Haploxeroll). It was demonstrated by field experiments that the soil surface of the coarse and medium‐textured soils consolidated markedly (soil surface elevation decreased about 3 mm) with surge compared to continuous water application for the first irrigation following spring tillage. The saturated hydraulic conductivity (Ksat) of these soils decreased about 45% from the first to the second on‐time. The surge effect was more pronounced during the first than the second irrigation. Most of the effect measured occurred during the first 10 to 20 min of the first off‐time. Consolidation and Ksat of the fine‐textured soil was not changed significantly by the same treatment. Two simple and practical field methods to evaluate this surge effect on soil hydraulic properties were developed: (i) measurement of soil‐surface consolidation by measuring the soil‐surface elevation changes, and (ii) measurement of Ksat by the dripper method. The soil surface level decreased by more than 1 mm and Ksat changed by about 25% when the surge effect was significant. An infiltration model developed during this study showed that simulated cumulative infiltration for surge water application was similar to measured results for the three soils studied.
Effects of Overland Flow on Plant Water Relations, Erosion, and Soil Water Percolation on a Mojave Desert Landscape
Authors: Schlesinger William H. , Fonteyn Paul J. , Reiners William A. 
Published: July 2010

AbstractPrevious work in the Mojave Desert of California has shown that diversion of overland flow from alluvial piedmonts results in lower shrub density and biomass compared to that in adjacent areas that receive overland flow. In this study, measurements of predawn xylem pressure potential of creosotebush (Larrea tridentata) on three areas that were deprived of overland flow and three adjacent areas indicated that shrubs in areas of drainage‐diversion maintained higher water potentials during midsummer drought, suggesting a greater availability of soil moisture in those areas. There were no differences in the distribution of 137Cs between these areas, suggesting that drainage‐diversion has not affected erosion of surficial deposits. Mean depth of wetting of the soil profile, as indicated by the depth distribution of mobile ions (Na+, Cl−, and SO2−4) in the soil, was not significantly different between areas, although the depth to the first peak in concentration of these ions was consistently shallower in areas of drainage‐diversion, suggesting reduced percolation of soil moisture. We conclude that the higher water potential of shrubs in areas of drainage‐diversion is due to lower competitive exploitation of soil moisture than is found among the high biomass of shrubs in undisturbed areas. In contrast, soil properties have not been greatly affected by the diversion of overland flow for the past 50 yr.
Environmental Influences on Soil Chemistry in Central Semiarid Tanzania
Authors: Jones Julia Allen 
Published: July 2010

AbstractThis study assessed the effectiveness of landscape features for predicting the variation in a set of chemical properties from 81 soil profiles sampled in a 236‐km2 site in central Tanzania. Soil samples were treated as points and coded by horizon and by groups, including landform, parent material, vegetation type, vegetation percent cover, and presence or absence of hypogeal termites. The variation captured by these groups in eight soil chemical properties (organic C, total N, acid‐extractable P, exchangeable cations, and extractable Al) was assessed using analysis of variance, Duncan's multiple range test, and discriminant analysis. Soil development fits the catena model along hillslope transects, but lateral subsurface transport of dissolved Fe and cations has produced plinthite and highly base‐saturated horizons just above the lithic or paralithic contact downslope of transitions between ferruginous sediments and granitic sediments. Nevertheless, biotic factors (vegetation type and density of termites) captured more variation than other groups at the regional level. Vegetation species composition and the density and type of termites in central Tanzania reflect soil depth, texture, clay mineralogy, and drainage characteristics influenced by landform and parent material. Root symbioses of native miombo and Acacia spp. woodlands may also modify local soil chemistry via selective uptake of C and exchangeable cations. Termites contribute to the depletion of organic C, total N, and associated nutrients throughout the soils they occupy in this region.
Weathering and Mineralogical Classification of Selected Soils in the Blue Ridge Mountains of South Carolina
Authors: Norfleet M. L. , Smith B. R. 
Published: July 2010

AbstractFour pedons in the Blue Ridge Mountains of South Carolina were studied to determine the mineralogy and weathering in soils in the southern Appalachians. These soils formed in weathered gniess or schist and receive as much as 2160 mm of annual precipitation. Gibbsite increased with increasing slope, elevation, and rainfall, and ranged from 60 to 670 g kg−1 of the clay fraction (<2.0 µm) and was as high as 140 g kg−1 of the whole soil (<2.0 mm). Gibbsite is thought to form from weathering of feldspars. Kaolinite ranged from 0 to 470 g kg−1 in clay fractions and was as high as 380 g kg−1 of the whole soil. Kaolinite appears to be the product of biotite kaolinization. Hydroxy‐Al interlayered vermiculite (HIV) was the dominant clay mineral in surface horizons, with randomly interstratified mica‐vermiculite and mica increasing with depth. All four soils met the requirements of the oxidic mineralogy class. Release of Fe from kaolinization of biotite, abundance of gibbsite, and fine‐loamy particle‐size class of these soils cause them to have quite high oxidic ratios. However, the high weatherable mineral content of these soils is not consistent with the oxidic mineralogy concept that is supposed to represent soils in an advanced weathering stage. If the oxidic class is to separate out intensely weathered soils, then some amendments must be made to exclude less‐weathered soils similar to the ones of this study. A maximum of 10% weatherable minerals is proposed as an additional criterion for the oxidic class.
Pyrite and Trace Metals in Glauconitic Parent Materials of Maryland
Authors: Rabenhorst M. C. , Fanning D. S. 
Published: July 2010

AbstractSamples were collected from the oxidized and reduced zones of three glauconitic sediment columns from the Nanjemoy (Eocene) and Aquia (Paleocene) formations on the Maryland Atlantic Coastal Plain. While absent from the oxidized zone, pyrite in the reduced zone ranged from 6 to 8 g kg−1. A portion of this pyrite was shown in thin section to be intimately associated with the glauconite. As shown by scanning electron microscopy, this pyrite occurred as euhedral octahedral crystals and clusters of crystals (up to 15 µm in size) within the matrix and in fissures of glauconite grains. Pyrite not within glauconite grains occurred as framboids, as well as euhedral crystals and clusters. Chemical analyses of magnetically separated fractions suggest enrichment of Zn, Ni, and Cu in the glauconite phase and Zn and possibly Ni in the pyrite phase. Interpretations of Cd and Pb data are less clear. With the exception of Cu, the two sites from the Aquia formation were higher in trace metals than those from the Nanjemoy site.
An Improved Method for Measuring Aggregate Stability of a Weakly Aggregated Loessial Soil
Authors: Pierson Frederick B. , Mulla David J. 
Published: July 2010

AbstractThe original high energy moisture characteristic (HEMC) technique for measuring aggregate stability is shown to have limitations for use with weakly aggregated soils. Improvements were made to expand the applicability of the technique to weakly aggregated soils and reduce its subjectivity to operator bias. The destructive force used to break down the aggregates was controlled by wetting aggregates 1.0 to 0.5 mm in diameter under suction on a sintered glass plate. The moisture characteristic curve for the aggregates was fit using a modified van Genuchten S‐shaped equation, and the specific water capacity curve was analytically calculated. The modal suction and the area under the specific water capacity curve were then computed and used to calculate a structural index value for aggregate stability at a fast and a slow wetting rate. Surface samples of weakly aggregated loessial soil were collected from adjacent long‐term organic and conventional farms in the Palouse region of Washington State. The coefficient of variation for replicate determination of structural indices from a slow wetting treatment using the original HEMC method on samples from both farms was 15%, whereas it was 7% using the improved method. Using the original HEMC technique, there was no difference in the stability ratio of either farm due to complete breakdown of aggregates dropped into standing water. With the improved HEMC method, the aggregate stability ratio and structural index for fast wetting were both significantly higher for soil on the traditional farm than on the organic farm. Thus, the improved method facilitates the measurement of differences in stability of weakly aggregated soils subject to long‐term differences in cropping and management history. In contrast, the original method was inappropriate for these weakly aggregated soils due to improper wetting rates and high variability resulting from operator subjectivity.
Modeling Wheat Seedling Growth and Emergence: I. Seedling Growth Affected by Soil Water Potential
Authors: Bouaziz A. , Bruckler L. 
Published: July 2010

AbstractTo improve the prediction of wheat (Triticum aestivum L.) emergence, an empirical model of wheat root and shoot growth, which takes into account the soil water potential effects, is proposed. Pregerminated seeds from a Moroccan wheat cultivar, Nesma 149, were used for laboratory experiments at a constant 22 °C temperature. Seminal root and shoot lengths were measured vs. time using a completely randomized design, for a clay loam soil (33.6% clay, 57.0% loam and 19.4% sand) at five water potentials: −0.02; −0.17; −0.39; −1.0; −1.31 MPa. Soil dry bulk density of aggregates ≤3 mm was 1000 kg m−3 and thus, soil mechanical resistance to root growth was regarded as a nonlimiting factor. Data were used to select satisfactory growth functions for seminal root axes and shoots and to estimate their empirical parameters. The monomolecular and Gompertz functions were retained for roots and aerial parts, respectively. Considering that the soil water potential in the root zone controlled the root elongation rate, we took into account the average soil water potential along the root axes for calculations. Furthermore, the effects of soil water potential on the estimated parameters of the models involved in the growth models were studied. Results showed that roots and shoots responded differently to soil water stress. After 17 d, total root lengths varied from approximately 600 mm to 300 mm for the −0.02 MPa and −1.31 MPa treatments, respectively, whereas shoot lengths were similar. Finally, the growth curves calculated with soil water potential as input were compared with observed results. The correlation coefficients between predicted and observed data varied from 0.77 to 1.00.
Influence of Fertilizer Application Nonuniformity on Crop Response
Authors: Ndiaye J. P. , Yost R. S. 
Published: July 2010

AbstractLevels of nonuniformity in K fertilizer application were established in a field experiment on a K deficient soil. Measures of uniformity of fertilizer distribution (UCF) were calculated from the coefficient of variation (CV) of K application (UCF = 1 − CV/100). The structure of spatial dependence of exchangeable soil K was used to estimate the proportion of a given experimental plot which should be below a specified threshold of exchangeable K. Fertilizer requirements were estimated on the basis of the proportion of the region that was deficient. If deficient areas were identified in the field, then variable rates of fertilization could be applied. The response of chinese cabbage (Brassica oleracea L. Chinensis) to K application was strongly affected by the uniformity of fertilizer distribution. Maximum yield decreased 9.5% with nonuniformity of fertilizer distribution. Amounts of K associated with 95% maximum yield were 97, 113, and 444 kg K ha−1 for UCF values of 1.0, 0.42, and −0.02, respectively. Corresponding tissue K concentrations associated with 95% maximum yield were 3.5, 3.8, and 4.0%. Increased variation in exchangeable K from CV = 44.1% to CV = 96.6% resulted in critical levels of soil K of 0.28 and 0.73 cmolc ha−1, respectively.
Application of an Infiltration Model to Experimental Data
Authors: Hogarth W.L. , Parlange J.‐Y. , Haverkamp R. , Davidoff B. , Selim H.M. 
Published: July 2010

AbstractInfiltration models are often fitted to experimental data in soils, but few actually take ponded depth into account. In this study, the effect of ponded depth is considered by using a model which actually incorporates ponded depth. This is achieved by fitting the model to the experimental cumulative infiltration data and comparing the resultant sorptivity values with two other models where ponded depth is assumed to be zero. The results indicate that there is a 10 to 15% difference, depending on the crop treatment, in the sorptivity when ponded depth is taken into account. It is concluded that the model gives an excellent fit to the experimental data and provides a reliable way of obtaining the physical sorptivity with different ponded depths.
Decomposition of Carbon‐14 Labeled Ryegrass and Maize under Tropical Conditions
Authors: Ayanaba A. , Jenkinson D. S. 
Published: July 2010

AbstractThis work is an extension of earlier studies on the rate of decay of plant material in the forest zone of Nigeria. Maize (Zea mays L.) leaves, uniformly labeled with 14C, were allowed to decompose for 2 yr under field conditions in an Alfisol (pH 7.0) or an Ultisol (pH 4.7). After two years, 15% of the original plant C still remained in the Alfisol. Decomposition was slower in the Ultisol, particularly during the first 26 wk. Maize leaves incorporated in soil at the beginning of the dry season initially decomposed more slowly than leaves incorporated during the wet season, but by the end of 2 yr the difference was small. Earlier experiments in Nigeria with labeled ryegrass (Lolium multiflorum Lam.) tops were continued: after 5 yr, 8% of the original ryegrass C remained in an Alfisol. After adjustment for differences in climate and soil texture, the current Rothamsted model for turnover of organic C in soil gave a close fit to the Nigerian data.
Corn Yield Response to Water Stress, Heat Units, and Management: Model Development and Calibration
Authors: Swan J. B. , Staricka J. A. , Shaffer M. J. , Paulson W. H. , Peterson A. E. 
Published: July 2010

AbstractA crop model for corn is presented that uses readily available soil, crop, meteorological, and management data as inputs to integrate the effects on grain yield of water stress, plant density, deficit of growing degree days, and planting date. The model can be run on an IBM‐PC, was developed for use in the deep loessial lands of the Upper Mississippi Valley in Major Land Resource Area (MLRA) 105 and associated soil areas, and was calibrated using data for 1972 through 1984 from tillage‐residue management experiments at Lancaster, WI. Estimated water stress, deficit in air‐temperature growing degree days (GDD), and plant density accounted for 77% of the 79% of yield variation explained by the model. The standard error of estimate for predicted yield was 0.67 Mg ha−1. Presence in the data set of interactions between water stress and GDD, and also water stress with plant density, allowed their incorporation into the model. Tillage and residue management had the principal effects of modifying plant density, soil water storage, and rate of phenologic development to the six‐leaf stage.
Erosion‐Induced Changes in the Properties of a Fragipan Soil
Authors: Rhoton F. E. , Tyler D. D. 
Published: July 2010

AbstractAccelerated erosion of fragipan soils results in a relatively fast decline in productivity, compared with soils without root‐restricting layers. This study was conducted to determine how the characteristics of fragipan soils change with an increase in degree of erosion, as indicated by a decrease in depth to fragipan. Samples were collected at 130 points from the A horizon at five sites on a Grenada silt loam (fine silty, mixed, thermic Glossic Fragiudalf) with depth to fragipan ranging from 15 to 112 cm. Laboratory analyses included a range of chemical and physical properties that influence soil productivity. The data were separated into eight groups on the basis of difference in depth to fragipan and analyzed by regression techniques. Several significant changes occurred as the depth to fragipan decreased. The amount of organic matter, extractable Mn, and silt decreased, whereas increases were observed in exchangeable Na, extractable Fe, percent sand, percent clay, modulus of rupture, color value, and chroma. A minimum of 82% of the variability in these parameters was explained by depth to fragipan. As the degree of erosion increases on fragipan soils several management problems, related to modification of the chemical and physical properties of the plow layer, can be expected. These include greater susceptibility to erosion, reduced seedling emergence and plant vigor, and less drought tolerance.
Relating Sulfate Adsorption to Soil Properties in Michigan Forest Soils
Authors: MacDonald Neil W. , Hart James B. 
Published: July 2010

AbstractSix Michigan forest soil series comprising several gradients in soil physical and chemical properties were studied to relate SO4 adsorption to soil properties. The series studied were Grayling (mixed, frigid Typic Udipsamments), Rubicon (sandy, mixed, frigid Entic Haplorthods), Kalkaska (sandy, mixed, frigid Typic Haplorthods), Montcalm (coarse‐loamy, mixed Eutric Glossoboralfs), Spinks (sandy, mixed, mesic Psammentic Hapludalfs), and Oshtemo (coarse‐loamy, mixed, mesic Typic Hapludalfs). Six randomly located map units of each series were sampled in the lower peninsula of Michigan. An index of SO4 adsorption potential was determined by shaking samples in solutions containing 0.312 mmol SO4‐S L−1 and measuring the loss of SO4 from solution. The highest SO4‐adsorption potentials were found in Bw, Bs, and Bhs horizons of the Grayling, Rubicon, Kalkaska, and Montcalm series (7.0 to 14.1 mg S kg−1) and in E and Bt horizons of the Spinks and Oshtemo series (4.3 to 10.1 mg S kg−1). Significant differences in adsorption among series were present when comparing the upper 50 cm or the 100‐ to 150‐cm depths in subsurface horizons, related to differences in Al, Fe, and clay concentrations. Sulfate adsorption was positively correlated with dithionite‐citrate and ammonium oxalate extractable Al concentrations in subsurface horizons of the soils studied (r = 0.69–0.90). Regression analyses indicated that SO4 adsorption could be predicted using variables derived from commonly measured soil properties (Al, Fe, pH, organic C, extractable P), with maximum R2 values ranging from 0.83 to 0.89.
Isolation and Characterization of an Iron‐rich Chlorite‐like Mineral from Soil Clays
Authors: Ghabru S. K. , Mermut A. R. , St. Arnaud R. J. 
Published: July 2010

AbstractThis study reports on the isolation and characterization of a naturally occurring Fe‐rich, 1.4‐nm nonexpanding chlorite‐like interphase from soil clays. The mineral was isolated from the coarse clay (2‐1 µm) fraction of a Boralf (Gray Luvisol) from Saskatchewan, by using a high‐gradient magnetic separation (HGMS) at 0.20‐T level of magnetic flux density (MFD). While most chlorites contain Fe2+, analyses showed that all the Fe in this mineral was in the Fe3+ form. High‐resolution transmission electron microscopic (HRTEM) examination confirmed a 1.4‐nm spacing throughout isolated particles. Iron was extracted from the interlayer of the mineral by repeated dithionite‐citrate‐bicarbonate (DCB) plus citrate‐dithionite (Tamura‐CD) extractions. These treatments resulted in the collapse of the mineral from 1.4 nm to 1.0 nm following K‐saturation and 105 or 300 °C heating. Extractions of several Fe‐rich chlorites with the same DCB and Tamura‐CD treatments showed that, although some Fe was extracted from them, they retained their characteristic 1.4‐nm spacing after the K‐saturation and heat treatments. The DCB and Tamura‐CD extractions resulted in a marked increase in cation‐exchange capacity (from 27 to 150 cmolc kg−1), and a layer charge of 0.75 per half unit cell. The high initial cation‐exchange capacity (CEC) values and the rapid acquisition of a micaceous (1.0‐nm) characteristic are atypical of the normal chlorites also included in this study. It is suggested that the mineral isolated is an Fe‐hydroxy interlayered vermiculite rather than a true chlorite. Regarding the genesis of the isolated mineral, two possibilities exist: the Fe lost from the octahedral layer of an original mica could have been responsible for the formation of an Fe‐hydroxy interlayer, thus producing a chlorite‐like mineral, or the interphase may have resulted from weathering of an original chlorite since chlorites were detected in the soil parent material.