bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Small‐Plot Point Injector for Liquid Fertilizer Application
Authors: Benjamin J.G. , Cruse R. M. , Blaylock A. D. , Vogl L. V. 
Published: July 2010

AbstractPoint injection of liquid fertilizer has shown promise as an alternative to standard surface or subsurface fertilizer application, particularly with no‐till and ridge‐till planting systems. Field‐scale point injector applicators are difficult to use in small plots, especially with labeled fertilizer materials such as 15N. This paper describes the construction and use of a small, inexpensive fertilizer application system, which simulates fertilizer injection by a large point injection applicator. Use of the applicator for 3 yr has shown the unit to be relatively accurate, durable and compatible with a variety of fertilizer materials.
A Generalized Solution to Infiltration from a Surface Point Source
Authors: Healy R. W. , Warrick A. W. 
Published: July 2010

AbstractA method is presented for the estimation of the time‐variant extent of the wetting front and wetted volume that develop in soil in response to infiltration from a surface point source. The method is based on a numerical finite‐differences solution of a dimensionless form of Richard's equation for axially symmetric flow. The generalized solutions are obtained from empirical equations, the coefficients for which are contained in a single table for a variety of soils and source strengths. Results for specific locations are obtained by application of scaling factors to the generalized results and possibly some interpolation. The method should be of particular value in the design of trickle irrigation systems by allowing simple estimation of rates and lengths of water application, as well as spacing between water emitters.
Sorption of Cadmium, Nickel, and Zinc by Kaolinite and Montmorillonite Suspensions
Authors: Puls Robert W. , Bohn Hinrich L. 
Published: July 2010

AbstractSorption is the predominant process governing metal ion movement in soils and includes the following physical and chemical mechanisms: adsorption, precipitation and absorption. This research attempts to use the hard‐soft‐acid‐base principle to explain sorption selectivity of the metal cations Cd, Ni and Zn by kaolinite and montmorillonite clays. The hard‐soft character of the clay surfaces, which is due to their surface functional groups, may be inferred by cation sorption selectivity experiments where pH and complex ion formation are controlled and monitored. Calcium saturated clays were suspended in Ca(ClO4)2, CaCl2 or CaSO4 and spikes of the above metals as divalent cations were added and their reactivity assessed within the framework of the HSAB Principle. For kaolinite in Ca(ClO4)2, metal sorption followed the sequence Cd > Zn > Ni. For montmorillonite in Ca(ClO4)2, metal sorption followed the sequence Cd ≈ Zn > Ni. In CaCl2 and CaSO4, the selectivity was different due to the presence of Cl− and SO2−4 which competed with the mineral surfaces for the divalent metal cations.
Reactivity of Phenolic Acids in Soil and Formation of Oxidation Products
Authors: Lehmann R. G. , Cheng H. H. 
Published: July 2010

AbstractPhenolic acids were shown to be oxidized rapidly in the presence of MnO2 to form a number of soluble products which were detectable by high pressure liquid chromatography. Some of the oxidation products have higher molecular weights than the parent compounds as shown by mass spectrometry; however, no significant products of polymerization were detected. Tests with ferulic acid showed that these oxidized products were rapidly sorbed to MnO2 surfaces and became less extractable by acidified organic solvents except after acid or alkaline hydrolysis treatment. Reactions of the phenolic acids with a variety of soils demonstrated that similar oxidation reactions could also occur in natural soils, the extent of which appears, however, to be affected by the nature of soil organic matter on the soil mineral surfaces.
Field Soil Properties Influencing the Variability of Denitrification Gas Fluxes
Authors: Grundmann G. L. , Rolston D. E. , Kachanoski R. G. 
Published: July 2010

AbstractThe spatial variability of field denitrification gas fluxes was investigated in relation to water content, soil‐gas diffusivity, nitrate concentration, and water soluble organic C. Water was applied in a periodic fashion along a strip of Yolo soil (Typic Xerorthents) amended with chopped alfalfa hay and nitrate. Data were analyzed statistically using simple correlations and spectral and coherency analysis. Log spectrums showed that nitrate cycled at the frequency at which water content cycled and was negatively related to water content due to apparent leaching of nitrate from the high water application areas. Denitrification gas flux cycled at twice the frequency of water content with maximum fluxes occurring at the sides of the water peaks. Spectrums for water soluble organic C and gas diffusivity indicated no significant spatial cycling. Although denitrification gas flux was more highly correlated to soil‐water content than to any other variable, coherency analyses revealed no significant relationships between denitrification gas flux and water or nitrate at specific frequencies due to opposing effects related to nitrate leaching and small gas diffusivities at the soil surface. The spatial pattern of denitrification calculated from a simple equation was examined using spectral analysis and was found to be not representing measured denitrification gas flux adequately at the frequency at which water content cycled. The discrepancy between measured denitrification gas flux and calculated denitrification rates was attributed to very small gas diffusivities preventing gas transport to the surface and inadequate characterization of actual C and nitrate concentrations at microsites.
Oxidative Coupling and Polymerization of Guaiacol, a Lignin Derivative
Authors: Simmons Kathleen E. , Minard Robert D. , Bollag Jean‐Marc 
Published: July 2010

AbstractIn order to better understand the chemical reactions involved in humus formation, guaiacol, a lignin derivative, was enzymatically oxidized. Under the conditions used, seven oligomers—five dimers and two trimers—were formed and comprehensive structural analyses were performed on these products. The oligomers were predominantly polyphenolic in nature, resulting from C‐C coupling of the guaiacol monomer. Two oligomers were formed by C‐O coupling and one dimer had a quinonoid structure. Based on the product structures, reaction pathways for the oxidative oligomerization of guaiacol are proposed. In this reaction pathway scheme, free‐radical coupling of the oxidized guaiacol leads to the formation of four dimeric intermediates. Nonenzymatic reactions of the four intermediates result in the formation of the seven stable guaiacol‐derived oligomers. Such reaction schemes may elucidate the mechanism of humus formation.
Cultivation and Slope Position Effects on Soil Organic Matter
Authors: Woods L. E. , Schuman G. E. 
Published: July 2010

AbstractOur objective was to determine the effect of land use and slope position on the organic matter (total and active) of two related soils with different A‐horizon thicknesses. To accomplish this, we sampled the surface 7.5 cm of soil from top, mid and bottom slope positions of paired native grassland and wheat‐fallow cropland toposequences of the Ascalon (Aridic Argiustoll) and Renohill (Ustollic Haplargid) soil series. We measured total organic matter (organic C and Kjeldahl N), and active organic matter (microbial biomass, and mineralized N and respired C in 20‐d laboratory incubations) concentrations. Concentrations of all measured properties were much lower in cultivated than in native sites, and smaller fractions of the total organic matter were in microbial biomass or in forms mineralized during incubation. Total organic matter concentrations increased downslope in the Renohill soil, but decreased downslope in the Ascalon soil. Active organic matter concentrations differed less between between slope positions than between land uses or soil series. Concentrations of active organic matter were equal in the two soils, even though the Renohill soil had been tilled longer (>25 yr vs. 1 yr) and had a thinner native A horizon (13 vs. 32 cm). One year of cultivation of the Ascalon soil reduced both its active organic matter concentrations and the fractions of the total organic matter in active forms by approximately the same amount as did 25 yr of cultivation of the Renohill soil.
Response of Soybean to Lime and Molybdenum on Ultisols in Northern Alabama
Authors: Burmester C. H. , Adams J. F. , Odom J. W. 
Published: July 2010

AbstractBecause previous liming experiments in northern Alabama showed that critical soil pH for soybean [Glycine max (L.) Merr.] varied widely among sites, an on‐farm research program was initiated to delineate the separate effects of likely acid‐soil infertility factors in the area. Factorial treatments at 15 test sites included lime and Mo at rates of 0 and 4500 kg ha−1 and 0 and 100 g ha−1, respectively. Thirteen experiments showed yield increases from liming, 12 of which also showed yield increases to Mo. Yield responses due to correction of only Mo deficiency occurred in five experiments while liming appeared to alleviate Al toxicity, as well as Mo deficiency, in six. Increased Mo availability was accompanied by increases in soybean leaf‐N and by increased seed weights. The soil parameter that correlated best with Mo deficiency was the Fe/Mo ratio from an acid ammonium oxalate extract. The critical ratio was about 1540. Molybdenum deficiency in soybean was found to be widespread.
Cokriging Point Data on Moisture Deficit
Authors: Stein A. , van Dooremolen W. , Bouma J. , Bregt A. K. 
Published: July 2010

AbstractExisting computer calculations by simulation of the moisture deficit (MD) were used for 500 point observations in an area of 404 ha with sandy soils in the Netherlands. The statistical prediction techniques kriging and cokriging were used to predict MD‐values in 100 points selected at random from the 500 available points. The MD‐data at the remaining 400 points were used for the predictions. The mean variance of prediction error (MVPE) and the mean squared error of prediction (MSEP) decreased only slightly when kriging is compared with cokriging using the mean highest water‐table level as a covariable. The number of MD‐values used in cokriging could, however, be reduced from 400 to 160 with only a small loss of accuracy in using 400 observations on the mean highest water‐table (MHW) as a covariable. As the MD‐variables being considered are four times as expensive to determine as the covariable, which is routinely estimated during soil survey, this also represents a considerable reduction of costs. Cokriging can thus be a useful technique to more effectively utilize available soil survey information.
Selection of a Parameter Describing Soil Surface Roughness
Authors: Lehrsch G. A. , Whisler F. D. , Römkens M. J. M. 
Published: July 2010

AbstractThe microrelief of the soil surface, termed soil surface roughness, affects water movement into a soil profile as well as seedling germination in the seedbed. When analyzing surface roughness, the selection of a measurable, physically significant parameter describing roughness is critical. An evaluation was conducted on eight roughness parameters, including maximum peak height, a microrelief index (the area per unit transect length between the measured surface profile and the least‐squares regression line through all measured positions of the transect), peak frequency, and MIF (the product of the microrelief index and peak frequency). The objective of the study was to select the parameter being the best descriptor of soil surface roughness. An automated, noncontact profiler was used to obtain surface profiles along transects, 5‐cm apart, of 1‐m by 1‐m plots after a cultivation and a simulated rainfall application at each of three different stages of soybean [Glycine max (L.)] development. For each cultivation, surface profiles were obtained on bare plots before rainfall and on adjacent vegetated plots after rainfall. The common logarithm of the MIF parameter was selected as the best descriptor of surface roughness because of its sensitivity to simulated rainfall as a source of variation, and its consistent response to such rainfall. MIF can also account for spatial dependency and can be measured relatively precisely.
Carbon Movement in Runoff and Erosion Under Simulated Rainfall Conditions
Authors: Lowrance Richard , Williams Randall G. 
Published: July 2010

AbstractOrganic C loss in erosion contributes to depletion of soil organic matter in continuously cultivated soils. Runoff, erosion, and C movement were measured from eight 39.6 m2 plots under simulated rainfall in order to assess C movement from a coastal plain soil. Plots were located at the Univ. of Georgia Coastal Plain Exp. Stn. near Tifton, GA, on a Tifton loamy sand (fine‐loamy, siliceous, thermic Plinthic Paleudults). Four soil cover conditions were duplicated on the eight plots: two‐row peanuts (Arachis hypogea L.), four‐row peanuts, continuous fallow, and bare‐bedded. Samples were taken during rainfall simulator events in March, July, and September 1985 and April 1986. Continuous fallow plots had significantly higher C concentrations in runoff and higher sediment concentrations. Sediment from the four‐row peanut plots had the highest C content, 5.83%. Total loads of C and sediment and total runoff were about twice as high from the bare‐bedded plots. Approximately 1.0% of the total soil C could be moved annually from the continuous fallow plots with a lower percentage from the other treatments. Runoff as well as sediment and C loads were lowest for simulated rainfall during September when peanuts had been inverted and were on the soil surface. Events in March and April produced lower runoff and lower sediment and C loads than events in July. Apparently the residue cover in the spring was more effective at preventing runoff and erosion than the partial crop canopy in July.
Detachment of Soil as Affected by Fertility Management and Crop Rotations
Authors: Hussain S. K. , Mielke L. N. , Skopp J. 
Published: July 2010

AbstractAn experiment was initiated on Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in 1981 to compare the effects of fertility management and crop practices on splash detachment of soil. Experimental treatments included comparisons of crop rotations of soybean [Glycine max (L.) Merr.] after corn (Zea mays L.) (SB), corn after soybean (C), and oat/red and yellow sweetclover (Avena sativa L./Trifolium pratense L. and Mellilotus officinalis Lam.) after corn (O/CL). For each crop rotation, there were two management options, either added manure (OR) or herbicide plus chemical fertilizer (HF). The seventh treatment was continuous corn (CC) with herbicide, chemical fertilizer, and insecticide. Soil surface samples from each treatment were subjected to rainfall intensities of low (35 mm h−1), medium (62 mm h−1), and high (120 mm h−1). Total splash detachment of soil from simulated rainfall was linearly related to rainfall intensity. For all crop rotation treatments, total splash detachment generally was greater for manured soils than from soil with herbicides and fertilizer. Continuous corn had the lowest soil splash detachment at low intensity, second highest splash detachment at medium intensity, and the highest splash detachment at high intensity. This trend clearly indicated that rate of splash detachment of CC was higher than from soil under crop rotations. The splash detachment rates were 48, 40, 39, and 31 mg cm−3 for CC, C, SB, and O/CL, respectively. Treatment by rainfall intensity interaction was significant, which suggested that intensity and crop rotation were not independent in their effect on soil splash detachment. Soil aggregation as inferred from geometric mean diameter (GMD) indicated that CC had the lowest degree of aggregation (150) as compared to 211 for C, 225 for SB, and 313 for O/CL.
Improved Apparatus for Preparing Nitrogen‐15 Labeled Anhydrous Ammonia
Authors: Vanden Heuvel R. M. 
Published: July 2010

AbstractAn all‐stainless steel apparatus is described that allows for dilution of highly 15N‐enriched liquid anhydrous ammonia (LAA) with natural abundance LAA to accurately and precisely produce up to 142 mL of LAA for 15N‐enrichments up to that being used for dilution. Such flexibility of 15N‐labeling is useful for studies where 15N‐enrichment requirements are diverse. The apparatus, calibrated for various volume‐pressure combinations of anhydrous ammonia gas at room temperature, allows for sequential recovery of selected amounts of 15N‐enriched and natural abundance LAA in a liquid N2 cold trap. The apparatus is constructed from commercially available components and the cylinders used for collecting the 15N‐labeled LAA are easily adaptable for use in laboratory and field N investigations.
Direct Observation of Phosphate Precipitation in the Goethite/Phosphate System
Authors: Martin Ronald R. , Smart Roger St. C. , Tazaki Kazue 
Published: July 2010

AbstractA combined scanning Auger, XPS, scanning SIMS, and TEM (electron diffraction) investigation of naturally‐occurring goethite surfaces in contact with 10−3 M KH2PO4 solution for 90 d at 60 °C has shown that isolated crystallites of the mineral griphite, Fe3Mn2(PO4)2.5(OH)2, are formed by reprecipitation from solution. No adsorbed phosphate can be detected on the goethite surface above 0.1 atomic % and there is no phosphate penetration of the goethite crystals. Evidence concerning initial adsorption of phosphate, before recrystallization, is reconsidered. The results suggest that phosphate retention in Fe oxide systems may be due primarily to precipitation rather than adsorption.
A Laboratory Technique for Releasing and Measuring Denitrification Products Trapped in Soil
Authors: Holt L. S. , Christianson C. B. , Austin E. R. , Katyal J. C. 
Published: July 2010

AbstractSeveral laboratory denitrification studies have shown an incomplete 15N balance at their conclusion. This incomplete 15N balance could be attributed to trapped gaseous products of denitrification within the soil. Incubation trials were designed to determine whether a complete 15N balance could be achieved if these trapped gases were released and included in the 15N balance. At the end of a preliminary incubation trial using flooded soils, 80% of the fertilizer was found in the soil and water fraction while the measured loss through denitrification into the headspace was only 2.6% with 70% in the soil and water fraction. When the incubation vessel was thoroughly shaken prior to sampling, fertilizer N recovery in the gaseous phase increased to 26.7%. This indicated that most of the gaseous products of denitrification had been trapped within the soil, and a nearly complete 15N balance was obtained.
Nitrogen‐15 Uptake by Eggplant Under Sodium Chloride Stress
Authors: Pessarakli M. , Tucker T. C. 
Published: July 2010

AbstractPlant growth and nutrient uptake are adversely affected under salt stress conditions. This study was conducted to examine the effects of NaCl stress on growth of eggplant (Solanum melongena L., cv. Syria), and 15N uptake and distribution in plant shoots and roots. Absorption pattern of 15N by eggplant from normal (−0.03 MPa osmotic potential) and NaCl salinized (−0.3 and −0.6 MPa osmotic potentials) nutrient solutions was investigated in a growth chamber. The 21‐d‐old seedlings were grown for 7 d in complete Hoagland solution before and 7 d after the completion of salt treatments. This was followed by 3‐d growth in minus N solution with respective salinity levels, and a 90‐d 15N uptake period after 15NH415NO3 addition to nutrient solutions. Nutrient solutions were sampled at 5‐d intervals for 15N disappearance from the pots (plant absorbed). Plant tissues were analyzed for distribution of 15N in shoots and roots. Lowering the osmotic potential of culture solution decreased total N and 15N uptake by plants at all salinity levels. Increasing salinity decreased dry matter production and water uptake to a greater extent than 15N absorption. Nitrogen‐15 concentration was substantially higher in shoots and roots of salinized plants as compared with the controls at the 90‐d harvest. Only at the 30‐d harvest was 15N concentration in shoots significantly higher than in roots at each salinity level. Any level of NaCl in the root medium appears to be detrimental to eggplant growth in terms of dry matter production as well as nitrogen (N and 15N) and water uptake.
Solution Parameters Influencing Dissolved Organic Carbon Levels in Three Forest Soils
Authors: Evans A. , Zelazny L. W. , Zipper C.E. 
Published: July 2010

AbstractA column study was conducted using selected horizons from three soils that were leached with pH 4.8 solutions containing either SO2−4 (0–0.208 mmol L−1) or NO−3 (0–0.16 mmol L−1) at various ionic strengths (0.2–2.53 mmol L−1). The quantity of dissolved organic C (DOC) release into the soil solution decreased with increasing ionic strength, with DOC levels remaining constant for ionic strengths > 1.10 mmol L−1. The addition of SO2−4 (0–0.208 mmol L−1) to the leaching solution resulted in elevated DOC levels over a wider range of ionic strengths, while DOC levels increased substantially for NO−3 additions only at conditions of low ionic strength <0.5 mmol L−1 and higher NO−3 concentrations > 0.048 mmol L−1. The portion of total measurable DOC attributed to anion source, compared to that of ionic strength, was observed to increase under conditions of low ionic strength and high anion concentration. Results suggest that anion composition and ionic strength may regulate DOC levels in solution.
Estimating Molecular Diffusion Coefficients of Urea in Unsaturated Soil
Authors: Sadeghi A. M. , Kissel D. E. , Cabrera M. L. 
Published: July 2010

AbstractA correct value for the molecular diffusion coefficient of urea in soil (Ds) is required to accurately predict urea movement in soil by molecular diffusion. In previous work, to estimate Ds in a simulation model of urea diffusion, we used an empirical equation of Papendick and Campbell that describes Ds for a dissolved species in soil to be a product of a tortuosity factor squared, the species diffusion coefficient in water (Dw), and the volumetric water content. Comparisons of measured and computed urea concentration with depth indicated that this equation was not adequately general over a wide range of soils. The objective of this study was to modify the parameters in the equation and, if necessary, develop a new relationship to estimate the value of Ds in soils. Laboratory studies were conducted on seven soils in which the clay content ranged from 10 to 51%. Urea concentrations with depth at 48 h following surface‐application were measured and also computed using numerical techniques with an initial estimate for Ds instead of computing it using Papendick and Campbell's equation. The Ds was modified incrementally, until the difference between computed and measured concentrations was minimized. In all seven soils, good agreement was obtained between measured and computed urea concentrations with depth. The maximum depth of urea movement occurred in Kahola soil (approx. 3.5‐cm deep), whereas least movement occurred in Crete soil (approx. 2.6‐cm deep). Nonlinear regression analysis gave a better relationship (Ds = 0.18 × Dw (Θv/porosity)2.98, R2 = 0.88) when relative water content (Θv/porosity) of the seven soils was substituted for the volumetric water content (Ds = 0.73 × Dw (Θv)2.58, R2 = 0.66) in Papendick and Campbell's equation.