bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Aggregate Size and Microrelief on Development of Surface Soil Crusts
Authors: Freebairn D. M. , Gupta S. C. , Rawls W. J. 
Published: July 2010

AbstractThe rate of water entry during rainfall has implications for crop agronomy, erosion, and groundwater recharge. This study investigated the influences of aggregate size, microrelief and rainfall intensity on development of surface crusts and infiltration. Infiltration rate and hydraulic resistance of developing crusts on two soils under various surface conditions and simulated rainfall were measured. The two soils were Webster clay loam (fine loamy, mixed mesic Typic Haplaquoll) and Port Byron silt loam (fine‐silty, mixed, mesic Typic Hapludoll). Aggregates with sizes of <1, <2, 1 to 2, 2 to 5, 5 to 19, 19 to 25, and 25 to 50 mm were studied. Final or steady‐state infiltration rates were similar for all aggregate sizes of both soil types, but development of a soil crust was delayed when the surface was made up of aggregates >19 mm in diameter. Large aggregates (clods) were a source of finer materials for the development of soil crusts. Microrelief effects were simulated by creating a ridge‐furrow configuration in a box. Ridge‐furrow microrelief did not influence total infiltration and was only effective in modifying the spatial distribution of water in the soil during the early phase of crust development. Infiltration rates, when measured using different rainfall intensities, could be described by a single curve when expressed as a function of cumulative rainfall rather than time. Total rainfall or rainfall energy may be better parameters for describing soil crust development than rainfall intensity.
Root Growth and Water Extraction Patterns from a Calcic Horizon
Authors: Georgen P. G. , Davis‐Carter Jessica , Taylor H. M. 
Published: July 2010

AbstractThere is considerable uncertainty regarding the effectiveness of calcic horizons in supplying water to plants. We conducted a field experiment on Acuff fine sandy loam (fine‐loamy, mixed, thermic Aridic Paleustoll) that contained a calcic horizon starting at 0.65‐ to 1.30‐m depth. Sunflower (Helianthus annuus L. ‘Gro‐Agri 380’), kochia (Kochia scoparia [L.] Schrader), and cotton (Gossypium hirsutum L. ‘GSA‐71’) were grown to determine if (i) plant roots can proliferate readily within a calcic horizon, (ii) plant roots are as effective in extracting water from the calcic horizon as from overlying horizons and (iii) there are differences among the three species in the ability of their root systems to extract water from calcic horizons. We concluded that (i) plant roots proliferated readily in the calcic horizons, (ii) kochia roots were more effective in extracting water from the calcic horizon than from overlying layers, (iii) sunflower root systems were substantially more effective than cotton root systems in extracting water from calcic horizons, and (iv) plant roots seemed to be less effective in extracting water when they first entered a soil layer, compared with their effectiveness a few days later.
Fire Severity, Ash Deposition, and Clipping Effects on Soil Nutrients in Chaparral
Authors: Marion G. M. , Moreno J. M. , Oechel W. C. 
Published: July 2010

AbstractFire may affect soil nutrient status by direct addition of nutrients and by indirectly altering the soil environment. The objective of this study was to examine how fire severity, ash deposition, and clipping affect posttreatment soil nutrient status. There were eight experimental treatments designed to examine increasing fire severity, ash (nutrient) addition independent of fire severity, clipping to study competition for nutrients per se, and untreated controls. Fire severity affected both the quality and quantity of ash. Increasing fire severity increased the concentrations of Mg and K and decreased the concentrations of NH4‐N and NO3‐N in the ash. As fire severity increased, there was an increasing recovery of ash relative to standing biomass (10–18 g kg−1). Fire increased the availability of all nutrients (NH4‐N, NO3‐N, PO4‐P, Ca, Mg and K). This nutrient enhancement was largely restricted to the surface soil (0–5 cm); only soluble N appeared to increase in the subsurface soil (5–10 cm). The soil quantities of NH4‐N increased and NO3‐N decreased with increasing fire severity, suggesting either a direct addition of variable amounts of these N ions or an indirect effect on postfire nitrification rates. Clipping had no effect on enhancing soil nutrient availability. The apparent recovery of the basic cations in the water extracts of the ash samples was in the order: K » Mg > Ca; this was different from the subsequent recovery in the soil: Ca > K > Mg. It was hypothesized that the relative recovery of basic cations in the water extracts of the ash samples was controlled by the solubility of Ca, Mg, and K salts.
Carbon and Nitrogen Analysis of Soil Fractions Using Near‐Infrared Reflectance Spectroscopy
Authors: Morra M. J. , Hall M. H. , Freeborn L. L. 
Published: July 2010

AbstractA nondestructive method to determine total C and N concentrations in soil size fractions is desirable when a limited sample is available. Near‐infrared reflectance spectroscopy (NIRS) was used to determine the total C and N concentrations in silt (50.0–2.0 µm) and coarse clay (2.0–0.2 µm), separated from 12 surface soils, by regressing the diffuse reflectance of near‐infrared radiation with constituent concentrations determined using combustion techniques. The correlation coefficients (R2) of the calibration equations were 0.93 for C and 0.89 for N, and the standard errors associated with NIRS predictions were 6.2 g kg−1 soil for total C and 0.6 g kg−1 for total N. Equation development with only silt samples improved the accuracy of NIRS calibration equations. Coefficients of variation [CV = (standard error of performance ÷ mean of the combustion procedure) × 100] for validation sample sets ranged from 14 to 19%, which is within the acceptable range for determining inorganic elements in plant tissues. We conclude that NIRS can be used to predict C and N concentrations in soil size fractions.
Probe for Measuring Soil Specific Heat Using A Heat‐Pulse Method
Authors: Campbell G. S. , Calissendorff C. , Williams J. H. 
Published: July 2010

AbstractTemperature rise, measured a short distance from a line heat source, can be used to determine the volumetric specific heat of soil and other materials. Volumetric specific heat is linearly related to the inverse of the temperature rise. The purpose of this note is to describe the construction and performance of a device for measuring specific heat using the line source method. The device was constructed from two hypodermic needles, 0.813 mm in diam. and 28 mm long, and spaced 6 mm apart. One needle contained a heater and the other a thermocouple. The temperature rise from heat pulses given to the heater were measured with the thermocouple. The coefficientof variation (CV) of specific heat on replicate samples was around 1%. Since water is the main variable component of the specific heat in nonswelling soil, changes in water content might be resolved to 0.01 or better in nonswelling soils.
Field Infiltration of a Salt‐Loaded Soil: Evidence of a Permeability Hysteresis
Authors: Mitchell A. R. , Donovan T. J. 
Published: July 2010

AbstractLow water‐infiltration rates may be detrimental to crop growth by reducing the water available to the plant, limiting salt leaching, and inducing ponding that may result in poor aeration during irrigation. Permeability has been shown to be a function of both the total salinity and the exchangeable sodium percentage (ESP) of the soil. Our objective was to measure the changes in water infiltration that occurred following extended salt loading on a Holtville silty clay (clayey over loamy, montmorillonitic (calcareous), hyperthermic Typic Torrifluvent) with permeability problems. An earlier 4‐yr salt‐tolerance experiment provided large plots (6 by 6 m) with six levels of salinity‐sodicity and three replicates. Plots were surrounded by fiberglass barriers and were adequately drained. Colorado River water, with an electrical conductivity (EC) of 0.9 dS m−1, was used to reclaim the plots in a series of small 80‐mm irrigations. Measurements of the salinity and the exchangeable cations of saturated soil extracts were taken before, midway through, and following reclamation. Infiltration rates were measured after 4 h of ponding and were found to differ significantly both during and after salt removal by leaching. The infiltration rates showed a hysteretic effect (delayed reaction) of saline and sodic treatments on soil water permeability. We attributed the effect to the slowly reversible flocculation and deflocculation of clay particles. Final soil ESP data from different treatments indicated that a traditional ESP threshold value may be of limited worth unless past salt history of the soil is considered. Models of hydraulic conductivity should account for this permeability hysteresis. Strategies of reusing saline drainage water may benefit from the hysteretic permeability by allowing high infiltration rates to persist.
New Method for Characterizing Soil Contrast
Authors: Villamayor F. P. , Huddleston J. H. 
Published: July 2010

AbstractLimitations of existing definitions of similar and contrasting soils for soil survey interpretations relating to both inclusions in map units and landscape patterns of soils led to the development of a new procedure for characterizing soil contrast. Six classes, or levels of soil contrast, are defined based on differences in intrinsic soil properties. Soil texture, coarse fragments, depth of rooting, drainage, permeability, pH, salinity, slope, erosion, and flooding are used to define 12 parameters for comparing soils. The range of values for each parameter is divided into a small number of discrete classes to facilitate comparisons. Within a given parameter (e.g., surface texture), class comparisons are rated as very similar, similar, somewhat contrasting, contrasting, or very contrasting, depending on whether the property values are in the same class, an adjacent class, nearby classes, or remote classes. Repeating this procedure for each parameter generates a set of 12 parameter contrasts for the two soils being compared. The distribution of contrasts among contrast levels determines the overall degree of contrast between the two soils. Where one or two parameters have a higher contrast than any of the others, that contrast level becomes the overall degree of soil contrast. Where several parameters vary at the same level, the cumulative effect of multiple variation is expressed by increasing the overall contrast to the next higher level. Advantages of the new model include multiple classes, definition of contrasts in terms of soil properties, and a precise procedure that can be duplicated by any two people given the same set of data.
Overwinter Changes in Physical Properties of No‐Tillage Soil
Authors: Unger Paul W. 
Published: July 2010

AbstractSoil physical properties often improve during winter, even without tillage. Based on observations, improvement is greater on ridged than on relatively flat soil, and it appears related to soil freezing and thawing. The objective of this study was to determine changes in bulk density, penetration resistance, aggregate‐size distribution, organic‐matter concentration, and water retention that occur during winter in a soil having low or high ridges formed by tillage. The study was conducted from 1985 to 1988 on Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll) at Bushland, TX. The 1985–1986 winter was coldest and had the least late‐period precipitation (19 mm). For the 0.04‐ to 0.07‐m depth increment during this winter, bulk density (Db) decreased 0.10 Mg m−3; penetration resistance (PR) decreased 0.14 and 0.20 kPa at −4.89 and −19.6 kPa matric potentials, respectively; mean weight diameter (MWD) of water‐stable aggregates increased 0.5 mm; organic matter (OM) decreased 0.7 g kg−1; and water retention at potentials from −2.44 to −19.6 kPa decreased 0.019 to 0.069 m3 m−3, all significant at P = 0.05. Changes were slight during the 1986–1987 winter. During 1987–1988. Db increased 0.07 Mg m−3, PR increased 0.06 kPa (at −19.6 kPa matric potential), OM decreased 0.4 g kg−1, MWD of water‐stable aggregates decreased 0.7 mm, MWD of dry aggregates increased 3.3 mm, and most changes in water retention were not significant. The 1987–1988 changes were opposite those for 1985–1986, apparently because of less intense freezing and more late‐period precipitation (44 mm). Late precipitation possibly reconsolidated soil that may have been loosened previously by freezing. In most cases, results for low‐ and high‐ridge treatments were similar. Freezing can improve soil physical properties, but improvements may be negated by late‐winter or early‐spring precipitation.
Specific Effect of Magnesium on Soil Erosion and Water Infiltration
Authors: Keren R. 
Published: July 2010

AbstractThis study was conducted to determine the effects of adsorbed Mg on erosion of soils exposed to rain. The effects of adsorbed Mg and Ca on soil erosion and infiltration rate (IR) of two soils (a Calcic Haploxeralf and a Typic Rhodoxeralf) exposed to rainfall, in the absence and presence of adsorbed Na, was studied. A drip‐type rainfall simulator and deionized water were used at water‐drop kinetic energy of 12.5 kJ m−3. The erosion rate of the soils was higher for the Mg‐soils than for the Ca‐soils. Both the steady‐state IR and the cumulative water depth required to reach a steady‐state IR were lower for Mg soils than for Ca soils. Adsorbed Mg by the montmorillonitic soil increased erosion and lowered IR, regardless of CaCO3 content. The Ca aggregates were more stable than Mg aggregates, even in the presence of Na. The specific effect of Mg on soil erosion was explained by the presence of these ions on the external surfaces of the clay tactoids, and the wider hydration shell of the Mg ion, as opposed to that of the Ca ion. It was suggested that the steady‐state infiltration and soil erosion rates are the result of two processes that occur in opposite directions: seal formation and soil detachment.
Predicting Cation‐Exchange Capacity from Soil Physical and Chemical Properties
Authors: Manrique L. A. , Jones C. A. , Dyke P. T. 
Published: July 2010

AbstractCation‐exchange capacity (CEC) is an important soil property in describing nutrient availability for plant growth. Measurements of CEC, however, are often not available or have been measured using different analytical methods. The need, therefore, exists to develop alternative procedures to predict CEC from accessory soil properties. In this study, regression analysis was used to examine the relationships between CEC and clay (CLAY), organic carbon (OC), and other soil properties. Multiple regressions indicated that CLAY, OC, and soil pH accounted for up to 51% of the variation in CEC for all soil (n = 37921). For soil orders, CLAY and OC accounted for up to 67% of the variation in CEC for Alfisols, Inceptisols, Mollisols, and Vertisols, and up to 78% of the variation in CEC for Entisols and Spodosols. The OC alone accounted for up to 73% of the variation in CEC for Spodosols. Poor predictions of CEC resulted from CLAY for Aridisols and Vertisols, indicating that factors other than CLAY interfered with accurate predictions of CEC.
Tillage and Simulated Rainfall Intensity Effect on Bromide Movement in an Argiudoll
Authors: Bicki Thomas J. , Guo Lei 
Published: July 2010

AbstractMovement of Br‐ in a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) managed under five different tillage systems and subjected to three simulated rainfall intensities was documented. Under low (10 mm/h) and medium (25 mm/h) simulated rainfall intensities, movement of Br‐ in the soil profile was not significantly different between moldboard plow, chisel plow, disk plow, para‐till, and no‐till systems. When subjected to a high simulated rainfall intensity, significantly greater Br‐ movement occurred in the soil profile managed under continuous, long‐term no‐till. Greater movement of Br‐ in the no‐till soil was attributed to preferential flow.
Determination of Low Concentrations of Phosphorus in Soil Extracts Using Malachite Green
Authors: Ohno Tsutomu , Zibilske Larry M. 
Published: July 2010

AbstractA sensitive method is needed to analyze soil‐water extracts that contain P at submicromolar concentrations. The proposed spectrophotometric method, based on the ionic association of malachite green with phosphomolybdate under acidic conditions, was evaluated on soil extracts. The molar absorptivity was 64641 ± 743 L mol−1 cm−1. Absorbance of the reagent blank was 0.069 ± 0.004. With 1‐cm path length cells and limiting absorbance of 0.004, the detection limit calculated from the Beer‐Lambert equation was 6.7 × 10−8 M orthophosphate P. Recovery of added P in saturated paste extracts averaged 91% with a range of 87 to 94% and averaged 101% with a range of 93 to 109% for 1:1 soil/water extract. The method was successfully applied to saturated paste extracts from soils of varied organic matter content and pH. The proposed malachite green method allows for P determination in restricted volume samples and at concentrations too low for the standard Murphy‐Riley method.
High‐Resolution Measurement of Root Water Uptake Using Automated Time‐Domain Reflectometry
Authors: Wraith J. M. , Baker J. M. 
Published: July 2010

AbstractMethods for monitoring changes in soil water content with high resolution in both space and time are needed to help quantify patterns of soil‐water uptake by plant roots. We designed and tested an automated time‐domain reflectometry (TDR) system for precise, continuous measurement of such changes. A two‐dimensional root‐zone enclosure was constructed from stainless steel wire cloth, with a parallel pair waveguide centered within each of 10 rectangular compartments. The wire cloth confined the electromagnetic pulse from the TDR without restricting root growth or water movement. Digitized waveforms from the analog TDR unit were captured, analyzed, and converted to volumetric water content by a program written for a datalogger. A sorghum (Sorghum bicolor [L.] Moench) plant was grown for 84 d, during which soil water content and changes in weight were monitored at 15‐min intervals. Standard deviations in water‐content measurement were estimated to be between 0.0008 and 0.001 m3 m−3. Water‐balance computations of evapotranspiration agreed well with measurements by a precision electronic balance, with a standard deviation of 0.0012 m3 m−3 during a 6‐d period. The wire mesh supported the root system, which had grown through it, even after soil was removed by rinsing with water. This will facilitate determination of root densities corresponding to measured changes in water content. The high degree of spatial and temporal resolution afforded by the system make it a valuable tool for studying the dynamics of water flow in the root zone, and information provided by this method may allow resolution of some issues that have remained controversial due to lack of measurement ability.
Phosphate and Accompanying Cation Transport in a Calcareous Cation‐Exchange Resin System
Authors: Akinremi O. O. , Cho C. M. 
Published: July 2010

AbstractCation‐exchange interactions are known to modify the movement of the individual cations involved. It is uncertain, however, how such interactions affect the movement and immobilization of an anionic species such as phosphate. An experiment was conducted to assess the influence of cation‐exchange reactions on the transport and immobilization of phosphate ions in a system of cation‐exchange resin with CaCO3 as the buffer. A 0.2‐g amount of KH2PO4 salt was uniformly applied to the surface of columns packed with either a mixture of CaCO3 and quartz sand or a mixture of CaCO3, quartz sand, and Ca2+‐saturated exchange resin. Phosphate ions diffused to a distance of 45, 60, and >60 mm from the surface after 3, 7, and 14 d of incubation, respectively, in columns packed with the CaCO3‐sand mixture. In the columns containing both CaCO3 and Ca2+‐saturated exchange resin, phosphate ions diffused about 35, 45, and 50 mm down the column during the same periods of incubation. The reduced movement of phosphate in the presence of Ca2+‐saturated resin is explained by the magnitude of precipitated phosphate obtained. In the columns containing CaCO3 and quartz sand, the amount of precipitated phosphate in the upper 6‐mm portion ranged from 20 to 180 mmol L−1. The corresponding value for columns containing Ca2+‐saturated exchange resin ranged from 250 to 550 mmol L−1. The movement of K+ was similarly retarded by the presence of Ca2+‐saturated resin. The results showed that the influence of cation‐exchange interactions on ion mobility is not limited to the cations involved. The mobility of an anionic species can also be affected where the exchangeable cation, when liberated into solution, can form a precipitate with the anion. In soils containing exchangeable cations capable of reacting with phosphate to form a precipitate, there is a need to take cation exchange into consideration when describing the fate of applied P.
Abrasion of Crusted Soils: Influence of Abrader Flux and Soil Properties
Authors: Zobeck T. M. 
Published: July 2010

AbstractSurface crusts greatly affect soil susceptibility to wind erosion. Little is known about the effects of soil properties and environmental factors on crust abrasion. In this study, the influence of abrader flux, degree of crust consolidation, and selected soil properties on soilcrust erosion was evaluated and sattistically modeled. Fourteen soils, representing a wide range of physical and chemical preperties, were evaluated. Soils were subjected to simulated rainfall rates of either 25 or 64 mm h−1, air dried, and abraded at mass fluxes of 0.010, 0.025, and 0.050 kg m−1 s−1. Crust abrasion (abrasion coefficient, AC) was defined as the slope of the linear regression of cumulative soil loss vs. cumulative abrader passage. An analysis of variance indicated that abrader flux, crust consolidation level, soil properties, and their interactions significantly affected (P < 0.05) soil loss. The AC ranged from 3.179 m−1 for an organic soil to 0.002 m−1 for silt loam and clay soils. The range of AC for unconsolidated soils was from 5 to 5000 times greater than for crusted soils. The mean AC for unconsolidated soils was 40 and 70 times greater than for crusted soils created at rainfall rates of 25 and 64 mm h−1, respectively. Regression analyses revealed that the natural logarithm of AC was positively correlated with sand content and the cation‐exchange capacity/clay ratio, and negatively correlated with abrader flux.