bluuebunny/crossref_metadata_2025_split huggingface dataset:
Field Study of Bromacil Transport under Continuous‐Flood Irrigation
Authors: Jaynes D. B. 
Published: July 2010

AbstractThe transport processes of sorbing chemicals in field soils are poorly understood. This study characterized the leaching behavior of the weakly sorbing herbicide bromacil (5‐bromo‐3‐sec‐butyl‐6‐methyluracil) in comparison to Br‐ during continuous‐flood irrigation of a small field plot. Twenty‐four solution samplers were used to periodically collect in situ samples from seven depths within four 1.83 by 1.83 m subplots. Estimates of the pore water velocity (vs) and dispersion coefficient (D) were made by fitting an analytical solution of the convection‐dispersion (CD) equation to the Br‐ data. Estimates of retardation (R) were made by fitting the CD equation to the bromacil data using the vs and D estimates from the Br‐ data and letting R be a fitting parameter. Estimates of R were also made from the results of batch equilibration studies using soil from seven depths. Best‐fit vs and D values exhibited considerable variability from sampler to sampler (CV = 1.25 and 1.30, respectively) and showed no significant trends with depth. Retardation values estimated from the CD equation averaged 1.88, but varied from 1.21 to 3.35 and also showed no significant trend with depth. In contrast, batch equilibration studies showed the absorption properties of the surface 0.6 m of soil to be significantly different than the 0.6‐ to 3‐m depth, with R values decreasing from 1.62 for the surface 0.6 m to 1.31 at 3 m. Although the two methods gave the same estimate of R in the surface soil, neither the lower R values at deeper depths nor the tendency to decrease with depth as predicted from the batch studies was apparent in the transport data. Using D as an additional fitting parameter to the bromacil data resulted in an average increase of 1.96 for this parameter, indicating more dispersion for the sorbing solute. Increased dispersion and increased tailing of the sorbed solute may be attributed to spatially variable adsorption and to a negative correlation between vs and R (r = −0.524).
Nitrogen and Nitrogen‐15 Analysis Using Automated Mass and Emission Spectrometers
Authors: Craswell E. T. , Eskew D. L. 
Published: July 2010

AbstractAnalysis of large numbers of samples has been a major limitation in the use of 15N. Two new instruments—an automatic N analyzer coupled to a mass spectrometer (ANA/MS), and a microprocessor‐controlled emission spectrometer (NOI‐6e)—were therefore compared with a longer established procedure of the International Atomic Energy Agency Laboratories involving 15N analysis with a Micromass (MM) 602E mass spectrometer. For 10‐mg plant samples ranging from natural abundance (NA) to 1.341 atom % 15N, the ANA/MS agreed with the MM 602E to within 0.002 atom %, and the NOI‐6e to within 0.014 atom %. In the range 1.895 to 2.398 atom %, data from the ANA/MS and the NOI‐6e agreed with the MM 602E within 0.022 and 0.093 atom %, respectively. Relative standard deviations (RSD) for six replications of a NA plant sample were: MM 602E, 0.22%; ANA/MS, 0.47%; NOI‐6e, 2.3%. For a plant sample with 2.398 atom % 15N the RSDs were: MM 602E, 0.03%; ANA/MS, 0.08%, and NOI‐6e, 0.3%. With finely ground soil samples (40 mg, 0.449 atom %) the RSD for 15N analysis with the ANA/MS was 0.30%. The ANA/MS was comparable to the Kjeldahl method (500‐mg samples) for plant N analyses and was found suitable for routine 15N analysis of plant and soil samples, but additional care in sample grinding was needed. The NOI‐6e analyzed 15N samples in one‐tenth the time required with previous emission spectrometers and its precision would be adequate for many agricultural experiments. The lower precision is a limitation, however, for measuring the 15N content in soil samples.
Wheat Stubble Management Affects Growth, Survival, and Yield of Winter Grain Legumes
Authors: Huggins D. R. , Pan W. L. 
Published: July 2010

AbstractThe adoption of no‐tillage systems in the Pacific Northwest will benefit from the development of crop rotations that complement winter wheat (Triticum aestivum L.). Experiments were conducted during 1986–1987 and 1988–1989 to determine the effects of wheat residue and fertility management on the growth, winter survival, and yield of ‘Glacier’ Austrian winter pea (Pisum sativum subsp. arvense L.) and winter lentil (Lens colinaris Medik.). No‐tillage (NT) and no‐tillage with reduced stubble (NT‐SR) enhanced soil moisture conservation and increased the early growth of Austrian winter pea (AWP), compared with conventional tillage (CT). Decreased shoot mass of winter lentil (WL) in NT, and elongated stems and reduced branching of AWP and WL in NT, were attributed to shading by stubble that reduced photosynthetically active radiation and red/farred ratios. Winter survival of AWP during 1986–1987 was reduced in NT (78%), compared with NT‐SR (91%) and CT (96%), but no differences occurred in 1988–1989. Less aboveground tissue necrosis of surviving AWP occurred in NT than in NT‐SR and CT for both years. Greater average yields in NT (3568 kg ha−1) and NT‐SR (3530 kg ha−1) than in CT (2700 kg ha−1) were correlated with greater fall growth and less winter injury. Residue management did not influence the yield of WL. Applied P and K did not have consistent effects on winter survival or yield. These results indicate that winter grain legumes can be used to complement wheat production in the design of no‐tillage rotations.
Modeling Tree Growth Sensitivity to Soil Sodicity with Spatially Correlated Observations
Authors: Samra J. S. , Stahel W. A. , Künsch H. 
Published: July 2010

AbstractRevegetation of degraded sites with an ecologically suitable tree species is an important environmental concern. Adequate evaluation of the salt tolerance of deep‐rooted perennials using pot or small‐plot culture investigations is often difficult. The natural soil heterogeneity found in field experiments provided a means to study the dependence of tree growth on soil variables such as sodicity. In such studies, the random errors of a regression model will usually show spatial correlations, and adjustments of statistical methods are, therefore, necessary. Tree height monitored for 3 yr was related to the root‐zone soil sodicity that was measured in four layers of a fine loamy Natric Haplustalf using a depth increment of 0.3 m. Sodium adsorption ratio was a better predictor of tree height variation than pH and DTPA‐extractable Na. Inclusion of DTPA‐P and ‐K in the regression model did not add to the information. The predictive power of the 0‐ to 0.6‐m layer alone was as good as that of all the four depths (up to 1.2 m) considered simultaneously. Neighboring residuals of ordinary regression of height on soil properties were correlated. Generalized least squares returned narrower confidence intervals of the sensitivity curves than corrected ordinary least squares. Consideration of pH as covariate to the log of the sodium adsorption ratio reduced confidence bands by 5 to 10%, which was roughly equivalent to 10 to 20% more observations.
Relative Efficiency of Broadcast and Banded Phosphorus for Sweet Corn Produced on Histosols
Authors: Sanchez C. A. , Porter P. S. , Ulloa M. F. 
Published: July 2010

AbstractHistosols used extensively for crop production are often hydrologically linked to environmentally sensitive wetlands, making it imperative that management strategies be developed to improve the efficiency of fertilizer P. Furthermore, sweet corn (Zea mays L.) produced on Florida Histosols is grown in rotation with sugarcane (Saccharum spp.), which responds negatively to high P. Reduction of the P rates applied to sweet corn would increase the compatibility of this common crop rotation. Studies were conducted across six site‐seasons during 1988 and 1989 to evaluate the relative efficiency of broadcast and banded P for sweet corn. Broadcast and banded P rates were 0, 25, 50, 75, and 100 kg P ha−1. Broadcast P was surface applied and disked into the soil before planting. Banded P was applied ≈3 cm below the corn seeds in bands mixed with soil in an approximate diameter of 5 cm. Sweet corn responded to P when soiltest P levels were below 1.2 g m−3. Total marketable yields, yield of U.S. Fancy, and quality parameters of sweet corn ears were increased by P rate and affected by placement in four of the six site‐seasons. Band placement reduced the amount of P required for a specified sweet corn yield and also appeared to result in higher total yield. The relative efficiency of banded to broadcast P depended on soiltest P level. The relative efficiency was greater than 3:1 (band/broadcast) when soil‐test P was <0.2 g m−3 but approached 1:1 as soil‐test P increased to 1.2 g m−3. Overall, results indicate that banding P is, indeed, a viable strategy to reduce the amount of P used for sweet corn production on Histosols.
Comparison of Denitrification in Two Riparian Soils
Authors: Ambus Per , Lowrance Richard 
Published: July 2010

AbstractThe factors controlling NO3 removal in riparian buffer systems are poorly understood. We measured denitrification rates for two Coastal Plain, forested riparian zone soils: Kinston fine loamy sand (fine‐loamy, siliceous, acid, thermic Typic Fluvaquent) and Alapaha loamy sand (loamy, siliceous, thermic Arenic Plinthic Paleaquult). Kinston soils are more poorly drained and have higher organic matter than Alapaha soils. Surface soil and shallow aquifer samples were treated with solutions that contained chloramphenicol with either distilled water, NO3‐N, glucose‐C, or NO3 plus glucose. Denitrification potentials (N2O production in the presence of acetylene) were significantly higher in Kinston soil for both depths. Surface samples from both soils showed significant responses to NO3 additions but no response to C additions without NO3. Subsurface samples, taken from the top of the aquifer, showed no significant response to either NO3 or C treatments for either soil. Both soils showed a high degree of stratification within the top 10 cm, with 88 and 68% of denitrification potential in the top 2 cm for Alapaha and Kinston soils, respectively. Denitrification rates in cores were much lower than in slurries but rates in cores with NO3 or NO3‐plus‐glucose additions were significantly higher than unamended or C‐amended cores for the Kinston soil. Although both soils respond to NO3 additions, Kinston soils are better able to reduce incoming NO3. These results indicate that denitrification in the shallow aquifer is a more important NO3 removal mechanism at the Kinston site than at the Alapaha site.
Field Crop Recovery and Modeling of Nitrogen Mineralized from Labeled Sorghum Residues
Authors: Vigil M. F. , Kissel D. E. , Smith S. J. 
Published: July 2010

AbstractEfficient use of fertilizer N requires an assessment of the N contribution from decomposing crop residues. The objectives of this study were to quantify and model the amount of mineralized N recovered by a growing crop from 15N‐labeled sorghum (Sorghum bicolor [L.] Moench) residues of variable N concentration and composition. The residues were incorporated into the surface soil of field microplots. The microplots were double‐cropped with sorghum and wheat (Triticum aestivum L.) for a 3‐yr period. The 15N tag in the crop residue was used to distinguish between residue‐derived N and that from soil organic matter. Between 4.5 and 25% of the residue N applied (36–83 kg N ha−1 was applied as crop residue N) was recovered by a sorghum crop 110 d after incorporation. This constituted 56 to 77% of the total N recovered during a 3‐yr period. Accumulated N recovered over time was described by modified first‐order models. Regression analysis indicated that 93% of the variability in N recovered by 110 d could be explained using the C/N ratio and acid‐detergent fiber contents of the residues. Measurements of N mineralized, using the method described above, were compared with predicted N mineralized, using MINIMO (a subroutine of the CERES‐Maize model). After adjusting MINIMO parameters using data collected 110 d after residue incorporation, the slope and intercept of a linear fit between measured and MINIMO‐predicted N mineralized 1097 d after residue incorporation were not different from one and zero, respectively.
Iron Oxidation at the Surfaces of Slash Pine Roots from Saturated Soils
Authors: Fisher H. M. , Stone E. L. 
Published: July 2010

AbstractRoot aeration in saturated gleyed soils is indicated by Fe oxide coatings on live‐root surfaces. Oxygen diffusing through gas‐permeable tissues, from the atmosphere to submerged roots, ultimately diffuses into and oxidizes the rhizosphere. The objectives of this study were to: (i) characterize the oxidizing conditions of slash pine (Pinus elliottii Engelm. var. elliottii) roots growing in saturated conditions, and (ii) test the hypothesis that submerged taproot systems are internally aerated. One study examined Fe‐oxide deposits on the roots of six saplings grown outdoors in drums filled with saturated, Fe‐amended peat. Another study examined roots of two mature slash pines growing naturally on a poorly drained Paleaquult. Orange Fe‐oxide precipitates coasted cortical tissue of sapling taproots and root branches growing in saturated peat. Iron concentrations in these roots were 6 to 96 times greater than in the surrounding peat. In gleyed horizons of the Paleaquult, Fe‐rich precipitates cemented sand to the surfaces of large‐diameter roots and entirely ensheathed fine roots of pine and pine cypress (Taxodium ascendens Brogn.). Prominent mottles, all neoferrans, surrounded fine pores, remnants of decayed‐root channels. Despite the anoxic growing conditions, all of the examined slash pine root systems oxidized and accumulated Fe, supporting other evidence that the taproot systems of slash pine growing in wet soils are internally aerated.
Iron Oxides in Selected Brazilian Oxisols: II. Mössbauer Studies
Authors: Fontes M. P. F. , Bowen L. H. , Weed S. B. 
Published: July 2010

AbstractClay fractions (<2 µm) of Oxisols derived from four different parent materials, all from the Triangulo Mineiro Region, Minas Gerais, Brazil, were analyzed using Mössbauer spectroscopy to provide insight into their Fe mineralogy. As little as 0.5% Fe as hematite in the total clay was quantitatively determined by this technique. Aluminum substitution in the Fe oxides resulted in lowering of the field of maximum probability (H max) and this Al substitution affected the magnetic ordering of goethite more strongly than did poor crystallinity. However, Al substitution estimated from Hmax showed some inconsistencies with varying temperature of Mössbauer analysis as well as with values obtained from chemical analysis. Apparently, the currently available Mössbauer calibration curves, obtained from synthetic samples of hematite and goethite, are not readily applicable to soil samples. Little difference in goethite content was found among the soils developed on parent material from mafic rocks. The data suggest that, in the presence of high levels of Fe in an ustic environment, the amount of goethite formed is not strongly correlated with organic matter. The values of the lower half‐width (LHW) of the hyperfine field distribution at room temperature showed some hematites to consist of very fine particles (broad LHW), whereas other hematites were better crystallized (sharper LHW).
Relation between Vertical Soil Movements and Water‐Content Changes in Cracking Clays
Authors: Bronswijk J. J. B. 
Published: July 2010

AbstractField studies on swelling and shrinkage in clay soils are scarce, due to the lack of sound experimental methods and suitable mathematical equations. This study was aimed at developing such methods and equations. Disks were positioned at various depths in the soil in order to measure vertical movements in undisturbed soil. Newly developed equations were applied to convert these vertical soil movements into three‐dimensional volume changes and crack volume and to relate them to water‐content changes. These equations are unique in that they are valid for water loss in the structural‐, normal‐, residual‐, and zero‐shrinkage phases, and for both isotropic and anisotropic shrinkage. Methods and equations were successfully tested in a 1‐yr field experiment in a heavy marine clay soil in the Netherlands. The use of seven rotating disks for measuring soil volume changes was about 10% more accurate than two other less laborious methods. An interesting application of this method and equations is the determination of soil water‐content changes by measuring vertical soil movements.
Changes in Soil Water Tables Following Phosphorus Fertilization of Young Slash Pine
Authors: McCarthy J.W. , Stone E.L. 
Published: July 2010

AbstractThis study was conducted in a 19‐yr‐old experimental planting of slash pine (Pinus elliottii Engelm. var. elliottii) on a level, very poorly drained Bladen soil (clayey, mixed, thermic Typic Albaquult) that was highly deficient in P. Phosphorus applied at planting at rates from 0 to 314 kg/ha in a randomized block design resulted in a concomitant range in stand basal areas from 3 to ≈ 38 m2/ha at 17 yr of age. Our objective was to quantify observed differences in height and duration of soil water tables associated with P treatment. Forty‐eight groundwater wells were measured weekly over a 1‐yr period. Drawdown of soil water tables during low rainfall periods was greater and more rapid in the high‐P plots, and the subsequent rise after rainfall was slower. These differences appeared only when the water‐table surface was deeper than about 0.5 m. Above that depth, rapid lateral movement through coarse macropores allowed equilibration among the 0.08‐ha plots, regardless of P treatment. In addition to overcoming acute P deficiency, the single applications of P fertilizers indirectly increased the depth and duration of aerated surface soil, and hence the opportunities for root exploitation.
Solution Chemistry in a Red Pine Plantation Thirty‐Nine Years after Potassium Fertilization
Authors: Shepard James P. , Mitchell Myron J. 
Published: July 2010

AbstractAccelerated leaching of nutrient cations has been hypothesized as a potential effect of acidic deposition. Nutrient‐cation deficiencies resulting from accelerated cation leaching have been proposed as a contributing factor in forest decline in Europe. The objective of this study was to intensively characterize the solution chemistry of a forest ecosystem in order to assess the status of its nutrient‐cation losses. Precipitation, throughfall, stemflow, and soil solution chemistry were monitored for 3 yr in a red pine (Pinus resinosa Ait.) plantation established in 1930 at the Pack Forest in the Adirondack Mountains of New York. Plots fertilized with 0, 59, and 118 kg K ha−1 in 1948 (designated C, L, and H, respectively) were studied to compare K leaching in systems of different K status and to assess the longevity of K‐fertilization effects on solution chemistry. The concentration of K in throughfall and stemflow was higher in the two fertilized plots relative to the control although 39 yr had elapsed since K fertilization. Fertilized plots generally had higher K concentrations in soil solution in the 0‐ to 8‐ and 8‐ to 15‐cm depths, whereas no differences were found among plots in the 15‐ to 45‐cm depth. Input‐output budgets indicated that much less H, NO3, and SO4 were leached below the rooting zone (0–45 cm) than were received from atmospheric (including dry) deposition. Net losses were observed for K, Ca, and Mg of 64, 294 and 17 molc ha−1 yr−1 (15, 3, and 1% relative to the exchangeable pools), respectively. These losses were not large compared with other forests in the USA.
Carbon Dioxide Degassing Effects on the pH of Spodosol Soil Solutions
Authors: Zabowski D. , Sletten R. S. 
Published: July 2010

AbstractHigh levels of CO2 in soil air can influence the composition of the soil solution according to carbonate equilibrium relationships. Carbon dioxide can lower soil solution pH by reacting with water to form aqueous carbonic acid (H2CO*3; the asterisk denotes hydrated carbon dioxide plus carbonic acid). Measurements of soil CO2 from a subalpine Spodosol showed concentrations as high as 12 000 µL L−1 (1.2%). Standard methods used to collect soil solutions can degas CO2 from soil solutions, resulting in elevated solution pH or decreased dissolved inorganic C (DIC). The objectives of this study were to determine whether degassing affected solution pH when solutions were collected from an acidic soil using two different techniques. Both collection methods, low‐tension lysimetry and centrifugation with double‐bottomed cups, were found to cause degassing of CO2 from soil solutions; however, pH was affected only in solutions from the lower B horizon and C horizon. The pH of the solutions from the upper horizons was not affected because high concentrations of soluble organic acids maintain these solutions at a pH <4.5. Carbonate equilibrium relationships suggest that the effect of CO2 degassing on soil solution pH should be negligible for forest soils with a solution pH <4.5 with soil‐air CO2 concentrations up to 6000 µL L−1.
Winter Wheat Phosphorus Fertilization as Influenced by Glacial Till and Loess Soils
Authors: Sander D. H. , Penas E. J. , Walters D. T. 
Published: July 2010

AbstractFertilizer P efficiency can be greatly affected by different methods of application. This study was conducted to determine the effect of different methods of P application on winter wheat (Triticum aestivium L.) grain yield, yield components, and fertilizer efficiency as influenced by different soils. Five loess‐derived soils and four till‐derived soils were selected that ranged from 4 to 9 mg P kg−1 (Bray and Kurtz P1). Methods of P application included knifed into the soil (dual placement) (KF), broadcast and incorporated (BF), and application with the seed (SF) at rates of 0, 10, 20, and 30 kg P ha−1. Results indicated that grain yield was increased differently by applied P on the soils studied. Grain yield increase from applied P was significantly greater on till‐derived soils than loess soils, although soil‐test P (Bray and Kurtz Pl) was similar. Till soils also required a higher P rate to maximize yield than did loess soils. Both KF and SF were consistently superior to BF on all soils but were especially superior on the till soils. Fertilizer efficiencies for BF averaged only 2% on the till soils, compared with 18% for KF and SF applications. Applied P increased head numbers on all soils. The primary reason for increased effectiveness of KF and SF applications was increased effectiveness of head production. As head numbers were increased by applied P, head size was decreased, especially for SF application, which increased head numbers more than KF or BF. Our study concluded that the soil test for P did not adequately determine the degree of P deficiency between loess‐ and glacial‐till‐derived soils for winter wheat production. Seed and knifed‐in methods of P application performed similarly on loess and glacial till soils, both being superior to broadcast application.