bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphate Sorption‐Desorption Behavior of Some Acidic Soils of South and Southeast Asia
Authors: Sanyal S. K. , Chan P. Y. , De Datta S. K. 
Published: July 2010

AbstractThe equilibrium phosphate sorption and release behavior and the kinetics of adsorption were studied in some acidic soils of South and Southeast Asia. Phosphate sorption data at 25 °C were fitted to the Tempkin, Freundlich, and Langmuir adsorption isotherms. The soils varied widely in their capacity to sorh and retain P. During desorption, the amount of sorbed P at a given equilibrium P concentration was always higher than that during sorption, indicating low desorbability of the sorbed P. The kinetic P sorption data at 21 and 35 °C were fitted to a modified Freundlich type of kinetic equation to obtain a parameter related to the sorption rate coefficient. The effect of temperature on the kinetics of sorption was small, suggesting the process is diffusion controlled. Equilihrium and kinetic P sorption parameters were found to he closely correlated with clay and organic matter contents and surface area of soils. A negative correlation between specific P sorption by clay or organic matter and clay or organic matter content of the soils suggests an association between the two colloidal components of the soils, causing loss of effective P‐sorhing surface area. An attempt was further made to evaluate the differential change in free energy of P sorption at infinite dilution from the corresponding thermodynamic equilibrium constant for P sorption by the given soils. The results suggest that the stability of the P sorption reaction products in the given soils contribute to the P‐fixing characteristics of these soils.
Mycorrhizal Development and Phosphorus Absorption in Maize under Conventional and Reduced Tillage
Authors: McGonigle Terence P. , Miller Murray H. 
Published: July 2010

AbstractArbuscular mycorrhizae participate in P uptake by maize (Zea mays L.). Previous studies using pot‐grown plants have shown that P uptake by maize is greater when soil is not disturbed between cropping and planting. This study was conducted to determine if mycorrhizal colonization and shoot P absorption in the field are higher under reduced tillage, under conditions of soil fertility and tillage management representative of commercial farming. Maize was sampled in 1990 and 1991 from plots maintained under no‐till (NT), and ridge tillage (RT). These were contrasted with maize from plots given moldboard plow (MP) tillage each year, which disturbs the soil to a greater extent. Plots were fertilized at recommended rates. In the early part of both years, shoot P concentration in NT and RT were significantly greater than under MP. These differences in shoot P did not persist after the six‐leaf stage. Greater development of mycorrhizae in the early season was seen in the RT and NT systems relative to that in MP. There were no significant effects of tillage on final yield, possibly due to the relatively high soil P levels. Under NT and RT, arbuscular colonization had a maximum at 48 d after planting (DAP) of 55% and 60%, respectively, followed by a linear decrease to near 10% at 166 DAP. Under MP, a plateau of 45% arbuscular colonization was sustained between 48 and 97 DAP, followed by a linear decrease similar to that in NT and RT.
Tillage and Furrow Diking Effects on Water Balance and Yields of Sorghum and Cotton
Authors: Baumhardt R. L. , Wendt C. W. , Keeling J. W. 
Published: July 2010

AbstractInformation on the combined effects of deep or no‐tillage together with furrow dikes (small earthen dams constructed in the furrow) on water conservation in semiarid regions is limited. The purpose of this study was to compare the amount of rain conserved and the yields of forage sorghum [Sorghum bicolor (L.) Moench] and cotton (Gossypium hirsutum L.) as affected by furrow dikes and tillage for a 3‐yr period. An Olton clay loam (fine, mixed, thermic Aridic Paleustoll) was alternately cropped to cotton and sorghum. Forage sorghum was grown in (i) disk or (ii) chisel‐disk tilled 16 by 23.8 m field plots with and without furrow diking. Cotton was grown in rotation following sorghum after (i) conventional moldboard‐disk or (ii) no‐tillage, with furrow dikes in one‐half of the tillage treatment plots. Crop yield, rainfall amount, soil water content, and runoff of natural rainfall and of simulated rainfall, applied at 80 mm h−1 for 1 h, were measured. Compared with conventionally tilled undiked plots, cumulative nonponded infiltration of simulated rainfall was significantly greater with notillage treatments and greater (not significant) in furrow‐diked treatments. Runoff of natural rainfall from plots with furrow dikes averaged ≈22 mm less than from undiked plots, and it was as much as 57 mm less; however, runoff from diked fields was observed. Under the conditions of this 3‐yr study, diking did not significantly increase crop water use and yield, but no‐tillage significantly increased crop water use and yield 1 yr. We conclude that furrow dikes installed during the growing season did not increase water conservation and crop yields under the conditions of this 3‐yr study due to seasonal dike consolidation that reduced the detention capacity and to the limited runoff from level fields. We also conclude that no‐tillage is more effective than chisel tillage for increasing water conservation and crop yields for the conditions of this study.
Soil Carbon Dioxide Characteristics under Different Forest Types and after Harvest
Authors: Fernandez Ivan J. , Son Yowhan , Kraske Chuck R. , Rustad Lindsey E. , David Mark B. 
Published: July 2010

AbstractTo characterize soil CO2 under different forest types and several years after a clear‐cut harvest, soil CO2 evolution and soil air CO2 concentrations were measured at three sites in Maine: the Howland Integrated Forest Study (HIFS) site, the Bear Brook Watershed in Maine (BBWM) site, and the Letter E township (Letter E) site. Soil CO2 evolution means ranged from 0.19 to 0.32 g m−2 h−1 among sites, whereas soil air CO2 concentration means ranged from 1023 µL L−1 for the O horizon to 3296 µL L−1 for the C horizon for the 1990 growing season. Soil CO2 evolution and soil air CO2 concentrations were similar under deciduous and coniferous forests and 4 to 6 yr after harvest. Limited multiple‐year data suggest that significant annual variations in temporal patterns of these properties exist as a function of short‐term climatic factors. These data suggest that soil CO2 evolution and soil air CO2 concentrations may be somewhat similar across a diversity of soil types, forest types, and forest conditions at any point in time for northern New England.
Organic Matter Role in Illitic Soil Colloids Flocculation: I. Counter Ions and pH
Authors: Heil Dean , Sposito Garrison 
Published: July 2010

AbstractDispersed soil particles have a negative impact on soil structure and contribute to soil erosion and contaminant movement. The colloidal properties of soil clays have been found to be different from specimen clays. The purpose of this study was to investigate the effect of organic matter on the flocculation of soil colloids as a function of electrolyte concentration, pH, and exchangeable or soluble bivalent cation type. The flocculation of suspensions of two illitic soils was studied using light transmission. Soil suspensions were prepared in Na‐K‐Ca and Na‐K‐Mg perchlorate solutions at a total electrolyte charge concentration of 5, 10, and 15 molc m−3 at pH 6 and 8. Flocculation at a given soluble bivalent cation charge fraction was increased as the organic C content of the soil colloids decreased. Calcium was more effective than Mg as a flocculant at the same soluble or exchangeable bivalent cation charge fraction. Increasing pH caused an increase in the flocculation of one of the soils, but this trend was reversed after the removal of organic matter by H2O2 treatment. The amount of electrolyte required for flocculation, the effect of pH, and the relative effectiveness of Ca vs. Mg all depended on soil organic matter content.
Solubility and Cation Exchange in Phosphate Rock and Saturated Clinoptilolite Mixtures
Authors: Allen E. R. , Hossner L. R. , Ming D. W. , Henninger D. L. 
Published: July 2010

AbstractMixtures of zeolite and phosphate rock (PR) have the potential to provide slow‐release fertilization of plants in synthetic soils by dissolution and ion‐exchange reactions. This study was conducted to examine solubility and cation‐exchange relationships in mixtures of PR and NH4‐ and K‐saturated clinoptilolite (Cp). Batch‐equilibration experiments were designed to investigate the effect of PR source, the proportion of exchangeable K and NH4, and the Cp to PR ratio on solution N, P, K, and Ca concentrations. The dissolution and cation‐exchange reactions that occurred after mixing NH4‐ and K‐saturated Cp with PR increased the solubility of the PR and simultaneously released NH4 and K into solution. The more reactive North Carolina (NC) PR rendered higher solution concentrations of NH4 and K when mixed with Cp than did Tennessee (TN) PR. Solution P concentrations for the Cp‐NC PR mixture and the Cp‐TN PR mixture were similar. Solution concentrations of N, P, K, and Ca and the ratios of these nutrients in solution varied predictably with the type of PR, the Cp/PR ratio, and the proportions of exchangeable K and NH4 on the Cp. Our research indicated that slow‐release fertilization using Cp/PR media may provide adequate levels of N, P, and K to support plant growth. Solution Ca concentrations were lower than optimum for plant growth.
Soil Solution Composition Relative to Mineral Distribution in Blue Ridge Mountain Soils
Authors: Norfleet M. L. , Karathanasis A. D. , Smith B. R. 
Published: July 2010

AbstractSoils with large quantities of gibbsite are normally associated with tropical climates and very intense weathering. The abundance of this mineral in the clay fractions of soils in the temperate climate of the Blue Ridge Mountains raised questions about the soil environment and possible mineral weathering trends. The composition of interstitial soil solutions of three highly weathered soils in the mountains of South Carolina was studied in order to explain contrasting distributions and prevalence of gibbsite and kaolinite. Extensive leaching caused by high amounts of rainfall was evidenced from the low solution ionic strengths and soluble Si content of these soils. The solubility data suggested gibbsite to be the most stable mineral in subsurface horizons serving as Al sinks (mineral precipitation), with kaolinite being more stable in surface horizons. These two minerals appeared to be in a dynamic equilibrium with hydroxy‐interlayered vermiculite, which is controlled by kinetic gradients imposed by site characteristics rather than solution chemistry alone. While the solution composition is consistent with the mineralogical suite of these soils, the residence time of Al and especially Si appears to be the determining factor for secondary mineral formation, weathering transformations, and distribution in the soil profile.
Basic Edta as an Extractant for Soil Organic Phosphorus
Authors: Bowman R. A. , Moir J. O. 
Published: July 2010

AbstractSoil organic P is an important source of plant‐available P in the Great Plains. It is, therefore, important in conservation tillage agriculture, that we know the size and the potential availability for crop use of this large P pool, which could exceed one‐half of the total P. We propose a one‐step procedure with hot basic EDTA (ethylene diaminetetraacetic acid) for total soil organic P that requires minimum manipulation and analytical prowess. Soil samples (0.5 g) were incubated for 2 h at 85 °C with 25 mL of 0.25 M NaOH + 0.05 M Na2EDTA, after which time the organic P in the extracts was determined by persulfate oxidation. Results from the evaluation of nine soils from various parts of the USA and one Canadian soil showed significant correlations with an existing wet sequential extraction and a dry high‐temperature ignition method for total organic P determinations. With the high‐organic‐matter Canadian soil, the EDTA method extracted 32% more organic P than the wet extraction method, and essentially the same as the dry ignition method. The new method appears to be especially useful for soils where organic acids and chelation mechanisms with P may be more dominant than ester‐type formations.
Potential Errors in Measuring Nitrogen Content of Soils Low in Nitrogen
Authors: Wang Deane , Snyder Michael C. , Bormann F. Herbert 
Published: July 2010

AbstractSamples of sandy soils of low N content were analyzed using a variety of procedures to assess N levels and sources of variation and bias. We assessed subsampling of collected soil, sample preparation by grinding, and two methods for measuring nitrogen. Micro‐Kjeldahl and CHN combustion procedures differed in accuracy and precision; the micro‐Kjeldahl method generally provided greater precision and accuracy across a variety of soil sample types. The greatest potential error was due to a particle‐size bias in removal of small subsamples (30–200 mg) required for each method. To eliminate this error, we recommend either pulverization of large samples to at least 0.5 mm before subsampling, or separation of soils into three or more homogenous particle‐size classes prior to chemical analysis.
Corn Yield and Salinity Response to Irrigation on Slowly Permeable Subsoils
Authors: Reichman G. A. , Trooien T. P. 
Published: July 2010

AbstractCrop yields in the northern Great Plains often could be improved with irrigation but many soils of this region have been considered nonirrigable because of their low hydraulic conductivity. This project was initiated to determine the leaching characteristics when irrigating two of these soils and to determine if harmful salinity increases would result from irrigation. We measured corn (Zea mays L.) yield and soil saturation extract electrical conductivity (ECe) and sodium adsorption ratio (SARe) in response to irrigation plus precipitation of one, two, and three times the calculated evapotranspiration and to N fertility of 100 and 200 kg N/ha. The study was conducted for 5 yr at one site and 6 yr at another site, both in the northern Great Plains. Yield and increase of ECe at 100 kg N/ha were less than at 200 kg N/ha. At both sites, ECe increased but corn yield did not decrease during this experiment. The SARe increased for all treatments but the maximum observed was <10. Excess irrigation usually had no effect on yield and did not decrease yield. Such excess irrigation provided salinity control by leaching. Precipitation also leached these soils. Our data indicate that the soils tested, the top 2.3 m of the soil profiles at two sites, allow enough leaching to permit effective well‐managed irrigation.
Root Zone Effects on Tracer Migration in Arid Zones
Authors: Tyler S. W. , Walker G. R. 
Published: July 2010

AbstractThe study of groundwater recharge and soil water movement in arid regions has received increased attention in the search for safe disposal sites for hazardous wastes. In passing through the upper 1 to 2 m of most soil profiles, tracers indicative of recharge such as Cl, 2H, 18O, Br, 3H, and 36Cl are subjected to a wide range of processes not encountered deeper in the profile. This transition zone, where water enters as precipitation and leaves as recharge, is often ignored when environmental tracers are used to estimate deep soil water flux and recharge, yet its effect may be profound. In this work, we reexamine the processes of root extraction and its effect on the velocity and distribution of tracers. Examples are presented for idealized conditions, which show clearly the relation between the root zone processes and the deep drainage or recharge. The results indicate that, when recharge is small and root zone processes are not accounted for, tracer techniques can significantly overestimate recharge until the tracer has moved well below the root zone. By incorporating simple models of root zone processes, a clearer understanding of tracer distributions and a more accurate estimate of recharge can then be made.
Soil Water Diffusivity Estimates from One‐Dimensional Absorption Experiments
Authors: Warrick A. W. 
Published: July 2010

AbstractA method to estimate soil water diffusivity from experimental absorption data was explored. The purpose was to directly match measured sorption curves (water content vs. distance or the Boltzmann transform variable) to scaled forms of the solutions and thus provide consistent hydraulic properties. Evaluation of such parameters is critical to prediction of water and solute transport within the vadose zone. The method is relevant to several, if not most, of the commonly used hydraulic functional relationships. Generally, the results gave two independent relationships of the parameters. Ane xample was considered and calculations performed for three alternative models. The best choice of each model was easily found and the evaluated parameters were shown to be consistent. The soil water diffusivities were compared for the estimated parametric relationships. Individual models provide alternative shapes for the diffusivity function, but tend to converge for the wetter range of water contents.
Agrichemical Detection in a Shallow Unconfined Aquifer as Influenced by Sampling Technique
Authors: Clay D. E. , Holman P. W. , Clay S. A. , Schumacher T. E. , Scholes K. A. , Bender A. R. 
Published: July 2010

AbstractThe sample collection system may influence the ability to describe the complex temporal and spatial variation of contaminants within an aquifer. The objective of this study was to evaluate the probability of detecting atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) using a bailer or skimmer in an unconfined aquifer located below an atrazine‐treated surface soil. In the simulated aquifer, the surface skimmer collected more Br− than the fixed sampling port located 15 cm below the aquifer surface and bailer. In the unconfined aquifer, the probability of an atrazine detection was higher when samples were collected with a surface skimmer tban a bailer. These results suggest that the ability to determine vertical transport of contaminants from surface soil to shallow aquifers at the point of agrichemical application is dependent on surface sampling of the aquifer.
Carbon and Nitrogen Dynamics of Soil Organic Matter Fractions from Cultivated Grassland Soils
Authors: Cambardella C. A. , Elliott E. T. 
Published: July 2010

AbstractThe amount of organic matter present in soil and the rate of soil organic matter (SOM) turnover are influenced by agricultural management practices. Because SOM is composed of a series of fractions, management practices will also influence the distribution of organic C and N among SOM pools. Our study examined SOM fractions that are occluded within the aggregate structure. Aggregates were disrupted by sonication and the disrupted soil suspensions were passed through a series of sieves to isolate size fractions. Densiometric separations were carried out on the size fractions, creating size‐density fractions. Fine‐silt‐size particles having a density of 2.07 to 2.22 g/cm3 isolated from inside macroaggregates contained the highest percentage of total soil C and N for all cultivation treatments and, because of its properties, will be referred to as the enriched labile fraction (ELF). As cultivation intensity was reduced, the amount of N in the ELF increased from 110 mg N/kg in the bare fallow treatment to 405 mg N/kg in the no‐till treatment. About 5% of the N in the ELF was mineralized during a 28‐d laboratory incubation, averaged across treatments. The proportion of N mineralized from the ELF (4.7%) was significantly higher than from intact macroaggregates (2.1%), which suggests this fraction may be protected from decomposition within the aggregate structure. We postulate that the ELF is a byproduct of microbial activity and that it contributes to binding microaggregates into macroaggregates in cultivated grassland soils.
Quantification of the Effect of Soil Organic Matter Content on Soil Productivity
Authors: Bauer Armand , Black A. L. 
Published: July 2010

AbstractThe positive effects of soil organic matter (OM) on soil properties that influence crop performance are well documented. But definitive and quantitative information of differential effects of soil OM contents is lacking for the northern Great Plains. The objective of this study was to quantify the contribution of a unit quantity of soil OM to productivity. Experiments were conducted on Williams loam (fine‐loamy, mixed, Typic Argiboroll) for 4 yr in the same field. The variables were soil OM content of the upper 30.5 cm together with all combinations of three postplanting soil available N levels (55, 90, and 125 kg N ha−1 as NO3‐N to 1.2 m) and three water levels. Water levels were uniformly maintained with a trickle system that independently metered water to each plot for each soil available N level. Pretillering spring wheat (Triticum aestivum L.) plant population decreased as soil OM content decreased in 3 of 4 yr. On an annual basis, highest total aerial dry matter and grain yields were associated with highest OM contents. The contribution of 1 Mg OM ha−1 to soil productivity, across the range of 64 to 142 Mg OM ha−1, was calculated as equivalent to 35.2 kg ha−1 for spring wheat total aerial dry matter and 15.6 kg ha−1 for grain yield. Loss of productivity associated with a depletion of soil OM in the northern Great Plains is primarily a consequence of a concomitant loss of fertility.
Soil Drainage Class Probability Mapping Using a Soil‐Landscape Model
Authors: Bell James C. , Cunningham Robert L. , Havens Matthew W. 
Published: July 2010

AbstractThe direct application of quantitative soil‐landscape models for soil mapping has been limited by technological constraints. This study combines a statistically based soil‐landscape model and geographic information system (GIS) technology to create soil drainage class maps. An existing soil‐landscape model that predicts soil drainage class from parent material, terrain, and surface drainage feature proximity variables was used. A digital geographic database of parent material, terrain, and surface drainage feature proximity variables stored in a geographic information system were used as model inputs. Combinations of these landscape variables were defined by overlaying the digital maps and by applying the soil‐landscape model to create predictive maps of soil drainage class probability and most‐likely soil drainage class. The modeled soil drainage class map agreed with an Order II (1:20000 scale) soil survey for 67% of the study area. A majority of the disagreement was attributed to areas predicted as somewhat poorly to moderately well drained by the model and well drained by the soil survey. This technique consistently assigns soil drainage class based on landscape attributes, documents the data and decision criteria used for drainage class assignment, estimates the uncertainty associated with drainage class assignment, and generates a digital map for GIS applications.