bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soil Urease Activity in Winter Wheat Residue Management Systems
Authors: Barreto Hector J. , Westerman Robert L. 
Published: July 2010

AbstractSurface residue accumulation under reduced and no‐till cropping systems has been shown to cause changes in the activities of several soil enzymes. The addition of crop residues containing urease increases the rate of urea hydrolysis which can increase the potential for ammonia volatilization. Our objective was to characterize the distribution of urease activity in the surface of two Oklahoma soils (Grant silt loam, fine, silty, mixed, thermic Udic Argiustoll and Norge clay loam, fine, silty, mixed, thermic Udic Paleustoll) which had been in conventional, reduced, and no‐till wheat (Triticum aestivum L.) residue management for four consecutive years. Soil cores 60‐mm deep were taken from residue management plots that had been previously fertilized with 168 kg urea‐N ha−1 yr−1 and separated into 10‐mm increments. Urease activity was determined in the soil increments and in mature undecomposed wheat straw. Urease activity was uniformly distributed in soil to a depth of 60 mm under conventional tillage. Significant increases in urease activity were measured in the surface 10 mm of both soils where accumulation of residue had occurred. Average urease activities in the surface 10 mm of soil under conventional, reduced, and no‐till residue management systems were, 12.1, 41.4, and 45.2 µg NH4‐N g−1 h−1 for Norge clay loam and 9.7, 12.4, and 35.0 µg NH4‐N g−1 h−1 for Grant silt loam, respectively. Activity of urease in mature undecomposed wheat straw grown at the site was 376 µg NH4‐N g−1 h−1 which was 28 × larger than the average activity found in soil. Wheat straw was shown to be a major source of the observed increase in enzymatic activity. Other sources for increased urease activity include increased microbial colonization during decomposition of residue and increased urea concentration in microsites due to fertilization, particularly in combination with residue.
Crop Root Distribution as Influenced by Grain Sorghum‐Soybean Rotation and Fertilization
Authors: Roder W. , Mason S. C. , Clegg M. D. , Kniep K. R. 
Published: July 2010

AbstractSoil physical, chemical, and biological changes resulting from crop rotations are likely to affect root development. Yet, crop rotation effects on root distribution have received little attention. The objective of this experiment was to measure the effect of soybean, Glycine max (L.) Merr. and grain sorghum, Sorghum bicolor (L.) Moench, rotation and fertilization on root distribution. Root samples were collected from an experiment with a 6‐yr history of (i) continuous soybean, (ii) continuous grain sorghum, (iii) soybean‐grain sorghum rotation, and (iv) grain sorghum‐soybean rotation. The experiment was conducted on a Sharpsburg silty clay loam (fine, mont‐morillinitic, mesic, Typic Argiudoll) near Mead, NE. Fertilizer treatments consisted of (i) control (no fertilizer), (ii) N at 45 kg ha−1 on soybean plots and 90 kg ha−1 on grain sorghum plots, and (iii) manure applied at 15.8 Mg dry weight ha−1 yr−1. Roots were sampled to a depth of 120 cm in 1986 and 150 cm in 1987. Root densities were reduced at most depths when soybean had been grown the previous year. Total root lengths per unit land area were 14, 21, 25, and 33 km m−2 and total root dry weights were 111, 136, 132, and 190 g m−2 for continuous soybean, soybean after grain sorghum, grain sorghum after soybean, and continuous grain sorghum, respectively. Fertilizer effects on root development were not consistent between years. Total soybean root length was positively correlated to grain yield, whereas grain sorghum root length in the 0‐ to 30‐cm zone was negatively correlated to shoot dry matter, kernel numbers, and grain yield.
Potassium Exchange Behavior in a Weathering Sequence of Volcanic Ash Soils
Authors: Delvaux Bruno , Dufey Joseph E. , Vielvoye Léon , Herbillon Adrien J. 
Published: July 2010

AbstractTropical volcanic ash soils are commonly associated within chronosequences and they usually sustain intensive agricultural use. In the Mungo plain, Western Cameroon (Africa), such soils are associated with the following weathering sequence: basaltic ash → allophane → halloysite → kaolinite. This paper was aimed at studying the cation exchange properties of six soils representative of such sequences and looking into their agronomic implications in intensive banana (Musa acuminata Colla) cropping systems. Calcium‐potassium exchange equilibria were performed at pH 4 and 0.01 mol L−1 chloride concentration on A and B horizons of the chosen soils. Their K/Ca exchange selectivity was interpreted through the fitting of the isotherm curves according to a two‐site model and the calculation of the Vanselow and Gapon selectivity coefficients. For some acid soil horizons, K selectivity was measured in different conditions of Al saturation and pH. The least weathered allophanic soils exhibit the lowest measured K selectivity. The halloysitic soils show a strong selective adsorption of K ions, which is associated with the presence of halloysite‐smectite mixed‐layer clays. Potassium selectivity further decreases in the kaolinitic soil. High Al saturation increases K selectivity in acid soil horizons while increasing pH promotes the adsorption of Ca ions. As K retention is low in young allophanic soils, banana plants frequently suffer from K deficiencies in rainy periods. On the contrary, K excess‐induced Mg deficiencies are general on acid kaolinitic soils and are related related to two factors: low Mg reserves, and a high retention of K relative to Mg promoted by high Al saturation.
Mycorrhizal Mediation of Phosphorus Availability: Synthetic Iron Chelate Effects on Phosphorus Solubilization
Authors: Jayachandran K. , Hetrick B. A. D. , Schwab A. P. 
Published: July 2010

AbstractTo determine whether chelation of Fe in slightly acidic soils will release sufficient P from Fe phosphate complexes to stimulate plant growth in P‐limited soils, the effect of EDDHA {ethylenediamine [di(o‐hydroxy‐phenylacetic) acid]}, a strong synthetic Fe‐chelating compound, on plant growth was studied in two P‐deficient native prairie soils and a P‐rich agricultural soil. Under laboratory conditions, EDDHA increased P extractability in the three soils. Subsequently, in a prairie soil/water slurry, repeated application of 10−4 M EDDHA significantly increased big bluestem (Andropogon gerardii Vitman) growth and P uptake as compared with distilled water controls or slurries which received only a single application of 10−3 M EDDHA. In slurries prepared with agricultural soil, growth of big bluestem was not affected by either concentration of the EDDHA. When the effect of EDDHA on growth of mycorrhizal and nonmycorrhizal plants was compared, in the prairie soils without EDDHA, mycorrhizal plants were significantly larger than nonmycorrhizal plants. Mycorrhizal plants in EDDHA‐amended soil had significantly greater growth and P uptake than mycorrhizal plants in unamended soil. However, neither concentration of EDDHA affected growth of nonmycorrhizal plants. In agricultural soil, plant growth was not affected by the mycorrhizal fungus or the EDDHA amendment. It appears that siderophore production by mycorrhizae or other soil microbes can significantly increase P availability in low pH soils and that this is a feasible mechanism by which mycorrhizal plants could assess P sources unavailable to nonmycorrhizal plants.
Diffusion Method To Prepare Soil Extracts For Automated Nitrogen‐15 Analysis
Authors: Brooks P. D. , Stark J. M. , McInteer B. B. , Preston T. 
Published: July 2010

AbstractA diffusion method that requires less labor than distillation methods was developed for preparing soil KCl extracts for 15NH+4 and 15NO‐3 analyses. The procedure is ideal for preparing samples having low N mass (50–200 µg N) with no cross contamination. The method uses 140 mL disposable specimen containers to hold the sample, and 7‐mm diam, disks of acidified GF/D glass fiber filter paper on stainless steel wire as the acid trap. Devarda's alloy and MgO are used as the reductant and base respectively. Complete diffusion for 40 to 60 mL of sample takes 6 d at room temperature with no shaking. Paired t‐tests comparing analyses of soil extracts of varying 15N enrichment by this method and steam distillation showed no significant difference (p = 0.64). Use of KHSO4 as the trapping acid allows the paper disks to be placed in a Sn capsule and analyzed by direct combustion mass spectrometry. Alternately, H2SO4 can be used and the disks analyzed by an automated NaOBr method. The disks can be easily dried in a desiccator over H2SO4 and mailed for 15N analysis by service laboratories.
Soil, Landscape, and Erosion Relationships in a Northwest Illinois Watershed
Authors: Kreznor William R. , Olson Kenneth R. , Banwart Wayne L. , Johnson Donald L. 
Published: July 2010

AbstractThe purpose of this study was to establish the relationship between soil taxonomic description, landscape form and position, and erosion in northwest Illinois. The study area consists of a first‐order drainage basin about 10 ha in size. The hillslopes have mean gradients of 6 to 10% with overland flow the primary contributor to erosion. A detailed geomorphic map of the watershed was constructed on a 1‐m topographic survey base map. Map units were delineated based on slope shape, gradient, and USDA erosion class. Erosion classes were determined for the transect pedons by comparison with two uneroded and uncultivated pedons in area cemeteries with similar slope gradient, slope shape, slope length, and landscape positions. The A horizon thickness and organic C content decreased and clay content increased as a consequence of cultivation and erosion. Transect data for all hillslope geomorphic units showed the erosion classes near the shoulder to be either slightly or moderately eroded. The lower backslopes and upper footslopes, just above the sediment basin, were either severely or very severely eroded, suggesting slope length to be the dominant factor affecting erosion. The geomorphic units with concave across‐slope shapes were found to be less eroded than those with convex across‐slope shapes. All cultivated pedons failed to meet the criteria for Mollisols, which was the taxonomic placement of the uncultivated pedons. Erosion phase, landscape segment, slope shape, slope gradient, and slope length affected the taxonomic placement of the cultivated hill‐slope soils when compared with uncultivated sites.
Use of Color Splitting and a Computer Technique to Separate Soil Moisture Groups
Authors: Al‐Abed S. R. , Lewis D. T. , Samson S. A. 
Published: July 2010

AbstractA method to quantify the distribution of colors across the surface and interior of soil peds was developed and used on soils that differed in morphological indicators of soil drainage. Soils from two contrasting geomorphic settings were selected for study. In the first of these settings, morphological indicators have not appeared to be useful predictors of actual soil wetness. In the second setting, soil morphology appears to predict wetness reasonably well. Pedons in the second setting provided an independent set of data against which to evaluate judgments made about pedon wetness of the first geomorphic setting. Pedon morphology was determined and duration of saturation was measured for all pedons studied. Saturation measurements were used to place pedons studied in a wet, medium, or dry moisture group. Ped surfaces and interiors were photographed using a 35‐mm camera and color slides were prepared. Color patterns on these slides were analyzed using a digital densitometer. Colors (red, green, and blue) were separated through use of the corresponding filters. Densities of these colors on each slide were determined and ranked within six brightness subranges. Cluster analysis was used to group the color rankings. Groups formed through this procedure coincided with groups (wet, medium, or dry) formed through measurement of duration of saturation. This procedure appeared to be better able to predict actual saturation than did commonly used methods based on horizon color and/or mottle features. It appears to provide a method to remove subjectiveness from soil color measurements and to quantify the measurement of soil color. Its predictive value appears to equal or exceed that of commonly applied techniques.
Earthworm Effects on Corn Residue Breakdown and Infiltration
Authors: Zachmann J. E. , Linden D. R. 
Published: July 2010

AbstractEarthworm (Lumbricus rubellus Hoffmeister) activity in the field has been implicated in increased rates of residue turnover, surface soil stabilization, and increased infiltration rates due to macroporous flow. A growth‐chamber study was conducted to evaluate some of the field variables associated with L. rubellus activity and tillage systems. Polyethylene buckets packed with sieved soil had either surface‐applied, incorporated, or no corn (Zea mays L.) residue, each with or without worms. Treatments were subjected to diurnal temperature and light sequences, and periodic additions of water were made over 60 d to maintain near‐optimum moisture conditions. Corn was grown in the cultures for an additional 30 d and was harvested before a small amount of concentrated Br solution was sprayed on the soil surface. Cultures were then subjected to simulated rainfall. Corn residue in the surface‐residue treatment with worms degraded 30% faster than in the no‐worm control. Plant growth and N content were not affected by the presence of worms. Burrows and casts formed under surface residue were greater in number and stability than in other worm/residue combinations. The surface‐residue treatment with worms reduced runoff and caused incoming water to bypass the surface soil matrix, moving small quantities of Br to significantly greater depths than in other treatments. Depth of peak Br concentration was greater in no‐residue treatments than in surface‐residue/worm or incorporated‐residue/worm or no‐worm treatments, indicating a substantial difference in the displacement of surface‐applied Br during rainfall. L. rubellus may alter the water balance of field soils while simultaneously hastening decomposition of the residue mat.
Multiple‐Year Response of Winter Wheat to a Single Application of Phosphorus Fertilizer
Authors: Halvorson A. D. 
Published: July 2010

AbstractInformation on multiple‐year responses of irrigated winter wheat (Triticum aestivum L.) to a single application of P fertilizer in the central Great Plains is limited. The effects of one‐time P applications (0, 34, 67 kg ha−1), with 5 N rates applied annually as subplots, on winter wheat grain yield and protein were studied. Winter wheat was grown on the same plots for three consecutive years under limited irrigation on a Weld silt loam (fine, montmorillonitic, mesic Aridic Paleustoll). Single P applications in the fall of 1983 significantly increased grain yields each of three consecutive years. Applying N to P‐fertilized plots resulted in greater yields than when N or P was applied alone. The 67 kg P plus 134 kg N ha−1 treatment produced 5405 kg/ha more grain in three crops than without P and N applied. Grain protein was reduced by P fertilization at low N rates, but increased by N fertilization. Soil‐test P and residual NO3‐N levels were significantly increased by P and N fertilizer additions, respectively. Soil NO3‐N in the 0 to 180‐cm depth for the highest N rate (336 kg N ha−1 in 1984 and 268 kg N ha−1 in 1985–86) was 764 kg N ha−1 without P and 458 kg N ha−1 with 67 kg P ha−1 applied. Downy brome (Bromus tectorum) infestations responded positively to N and P fertilization and tended to increase in severity each year in this monoculture winter wheat system. The results indicate that an adequate level of P and optimum level of N are needed to achieve efficient use of these nutrients by winter wheat and to reduce the amount of potentially leachable NO3‐N in the soil profile.
Interstratified 1:1–2:1 Mineral Formation in a Polygenetic Soil from Southern Ohio
Authors: Jaynes W. F. , Bigham J. M. , Smeck N. E. , Shipitalo M. J. 
Published: July 2010

AbstractA polygenetic soil from southern Ohio, formed by loess deposition on a pre‐existing Sangamon paleosol, was examined to determine if the lithologic discontinuity has affected subsequent clay‐mineral weathering or formation. Analyses of the <0.2 µm clays indicated that cation exchange capacities (CECs) and total Mg, K, and Fe contents were lowest near the interface between the loess and underlying paleosol at a depth of approximately 65 cm; in contrast, total Al contents were highest in this zone. An interstratified 1:1–2:1 mineral was identified in materials surrounding the loess‐paleosol contact and was concentrated in the 2.03 g/cm3‐density fraction of the <0.2 µm clay using density‐gradient centrifugation. Alkylammonium exchange of the 2.03 g/cm3‐density fraction demonstrated that the 2:1 component of the interstratified mineral was heterogeneous in charge and included layers characteristic of both smectite and vermiculite. Soil properties and depth distribution of the interstratified mineral suggest a pedogenic origin.
Rapid Digestion Procedure for the Determination of Total Nitrogen and Nitrogen‐15 Content of Soils
Authors: Christianson C. B. , Holt L. S. 
Published: July 2010

AbstractThe effectiveness of a rapid acid‐digestion procedure for total N content and atom % 15N was tested on six soils exhibiting a wide range of physical and chemical characteristics. The procedure uses H2SO4 and H2O2 without addition of a salt or metallic catalyst. Average recovery of total N and atom % 15N from soils digested with the H2SO4/H2O2 digestion procedure compared with a standard Kjeldahl digestion procedure were 98.2% and 100.9%, respectively. The H2SO4/H2O2 digestion takes only 38 min to complete.
Transport of Exchangeable Cations in an Aggregated Clay Soil
Authors: Gaston L. A. , Selim H. M. 
Published: July 2010

AbstractThe objective of this study was to assess the applicability of the classical and mobile‐immobile transport models for describing cation transport in soils. The transport of exchangeable cations for binary and ternary systems in an aggregated clay soil using miscible displacement methods was examined. Packed columns of aggregates of Sharkey soil (Vertic Haplaquept) were saturated with Ca. Pulses of Mg or Mg plus Na were applied to these columns, then eluted with Ca. Chloride was the accompanying anion. These leaching experiments were conducted at constant and variable total solution concentrations. Two pore‐water velocities were used in these experiments. Effluent was collected in fractions and analyzed for concentration of cations. Exchange isotherms were determined for the cation pairs Ca‐Mg, Ca‐Na, and Mg‐Na. Experimental leaching data were compared with predicted breakthrough curves obtained using the classical (or one‐region) and mobile/immobile water (or two‐region) transport models. The two‐region model offered no improvement over predictions obtained using the one‐region model. The locations of all breakthrough peaks were well described by the models; however, peak heights for Mg breakthroughs were consistently over‐estimated. Extension of the model to include the occurrence of CaCl+ and MgCl+ and adsorption of these complexes did not improve model predictions.
Steady‐State Procedure for Determining the Effective Particle‐Size Distribution of Soil Carbonates
Authors: Hartwig R. C. , Loeppert R. H. , Moore T. J. 
Published: July 2010

AbstractA pH‐stat procedure in conjunction with the equal‐diameter reduction model was used to estimate the effective particle‐size distribution of soil carbonates. Samples were titrated by pH‐stat at pH 3 and 5. The cumulative dissolution data and rate constants for the dissolution of Iceland‐spar calcite were incorporated into simultaneous equations to obtain estimates of the effective particle‐size distributions of soil carbonates. Results obtained by this method from 23 calcareous soils were compared with results obtained by a sieving and sedimentation procedure. The pH‐stat procedure resulted in the estimation of a higher proportion of clay‐size carbonates than was obtained by the sieving and sedimentation procedure. This difference was attributed predominantly to the higher reactivity of soil carbonates compared with Iceland‐spar calcite. The pH‐stat procedure was especially useful for obtaining quantitative estimates of the proportion of highly reactive clay‐size carbonate with <0.2‐µm effective particle diameters.
Kinetics of the Nitrite to Nitric Oxide Reaction in Peat
Authors: McKenney D. J. , Lazar C. , Findlay W. J. 
Published: July 2010

AbstractNitrite consumption and net NO production rates were measured across a pH range of about 3 to 8 and a temperature range of 5 to 40 or 10 to 70°C in nonsterile and sterile peat, respectively. The NO was sparged from stirred peat/water (1:10) slurries by N2 or Ar carrier gas and analyzed. Addition of small quantities, 1 to 280 µg NO‐2‐N g−1 dry peat, resulted in immediate No production. Biological production of NO exceeded chemical (nonbiological) production in nonsterile peat at pH >5. At pH >6, rates were less than 5 × 10−9 mol min−1 g−1 dry peat with chemical production rates relatively insignificant. Decreasing pH increased rates significantly, particularly the nonenzymatic process, which apparently dominates NO production at pH <4.5. The chemical process was first order with respect to [NO‐2]. The dependence of [H+] was complex, approximating first‐order behavior at [H+] <4 × 10−4 mol g−1 dry peat and more strongly dependent at higher concentrations. The activation energy for the chemical reaction at pH 5.09 was 52.3 kJ mol−1. The average value for nonsterile peat measured at pH 5.45 and 6.26 was 41.4 kJ mol−1. The stoichiometric coefficient, a, for the overall reaction NO‐2 → a No was 2.14 ± 0.39 in sterile peat and 2.00 ± 0.38 in nonsterile peat. In the latter case, where both enzymatic and nonenzymatic reactions occur, the value may also reflect the nonenzymatic reaction. Other nitrogenous gases, N2O, N2, NOx and CH3ONO were not observed under the flow conditions employed, suggesting that NO is the primary product of NO‐2 reduction.
Nitrogen Management and Nitrification Inhibitor Effects on Nitrogen‐15 Urea: II. Nitrogen Leaching and Balance
Authors: Walters D. T. , Malzer G. L. 
Published: July 2010

AbstractNitrification inhibitors (NI) may reduce N leaching losses, and should have the greatest effect on sandy soils where leaching potential is high. This study used 27 lysimeters to evaluate the effect of a NI, nitrapyrin [2‐chloro‐6(trichloromethyl) pyridine], on soil water percolation (SWP) and N leaching losses from an irrigated sandy loam soil (Typic Hapludoll) planted with corn (Zea mays L.), and monitor the fate of a single application of 15N‐enriched urea over a multiyear period. Urea was applied at 90 and 180 kg N ha−1 yr−1 for a 3‐yr period, with and without NI, and with and without incorporation. Urea + NI reduced SWP between planting and silking in 2 out of 3 yr when growing degree days (GDD) were high. After silking, SWP was reduced when urea + NI was incorporated and leaching load was high. A twofold increase in N rate resulted in an average of 3.4 times more N leached over 3 yr. The NI influenced time of N loss but not total N loss. Leaching losses of fertilizer‐derived N (FDN) were delayed 25 to 50 d when urea + NI were incorporated. The leaching load required to reach the maximum rate of FDN loss was higher with urea + NI. Leaching losses of fertilizer N were three times greater when determined by the difference method than by isotope‐ratio analysis. Differing results with these two calculations are attributed to isotope dilution with indigenous soil N as a result of microbial activity. Nitrification inhibitors may reduce the potential for nonpoint‐source pollution by delaying NO3 leaching, but will be most effective if coupled with proper N rates and conservative irrigation water management.