bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applicator for Spreading Liquid Manures on Small Research Plots
Authors: Wetterauer Donald , Killorn Randy 
Published: July 2010

AbstractFarm‐size liquid‐manure pressure or vacuum tanks are not well suited for applying manure to research plots. It is difficult to manuever the spreaders and accurately control the flow of manure. This report describes an inexpensive liquid‐manure spreader developed for use on research plots (i.e., 4.6 by 12.2 m). The spreader has been used to apply manure as broadcast or injected treatments at rates of 18 000 to 80 000 L ha−1. This spreader can also be used to hand‐apply manure to very small (1.5 by 1.5 m) plots.
Ionic‐Equilibrium Time inside Ceramic Cups in Unsaturated Porous Media
Authors: Riga P. , Charpentier S. 
Published: July 2010

AbstractIn order to improve the methodology of collecting soil solutions with porous ceramic cups without suction, we developed a method to estimate an ionic‐equilibrium time (tC/C∞) inside cups first filled with distilled water. Characterization of tC/C∞ was used to select the minimum interval time between two extractions with different water contents (θ) or water pressures (ψ). The method is based on an analytical solution of the general equation of cylindrical diffusion. The model is used for approximating the molecular diffusion coefficient (D) vs. θ or ψ and predicting the evolution toward ionic equilibrium inside the cups. It was satisfactorily validated, using KNO3 as a solute, with a fine sand, a silty clay soil, and a peat‐perlite mixture. The results showed that tC/C∞ is (i) dependent on molecular diffusion, which has a particular relationship with θ for each medium, and (ii) proportional to the squared radius of the cup. The best results obtained near saturation showed that the times necessary to obtain a concentration close to equilibrium with standard cups (22.6‐mm diam.) were ≈4 d with the peat‐perlite mixture and ≈2 wk for the sand and the silty clay soil. Furthermore, tC/C∞ can take up to 1 mo when diffusivity in sand decreases drastically with low water content. The length of time needed to reach equilibration limits the usefulness of this sampling method for conditions where changes in solute concentration with time are weak, such as diffusion phenomena with slow or nonexistent displacement of solute. Nevertheless, the equilibration time may be reduced to ≈30 h by using smaller cups (9.6‐mm diam.) with high‐water‐content media.
Integral Method for Estimating Soil Hydraulic Properties
Authors: Shao Mingan , Horton Robert 
Published: July 2010

AbstractSoil hydraulic properties are required to fully understand and predict soil water distribution. Soil hydraulic properties include the soil water characteristic curve and hydraulic conductivity. We used an integral method to solve the problem of water absorption into a horizontal soil column. The integral solutions to the problem were used to estimate the parameters α and n in the van Genuchten model for soil water characteristic curves. The two parameters, α and n, in the characteristic curve model were estimated by the length of the wetted zone, sorptivity, and saturated hydraulic conductivity. This new integral method uses both Richards' equation and the closed‐form equations of soil hydraulic properties. Six soils ranging from sandy loam to clay loam were used to test the method. Soil water characteristic curves estimated by the infiltration method are in good agreement with measured characteristic curves. The integral method provides a transient water flow approach to estimate the soil water characteristic curve instead of the usual equilibrium method. This is a new and simple means to determine soil hydraulic properties.
Supercritical Fluid Extraction of 2,4‐D from Soils: pH and Organic Matter Effects
Authors: Rochette E. A. , Harsh J. B. , Hill H. H. 
Published: July 2010

AbstractSupercritical fluid extraction (SFE) recoveries of 2,4‐D (2,4‐dichlorophenoxyacetic acid) from spiked Washington soils depended on both pH and organic matter content. The soils used in this study spanned a wide range of organic C concentration (2–480 g kg−1). One of the soils (the Benge series A horizon) was adjusted to pHs from 1.8 to 8.3, and extracted with methanol‐modified supercritical CO2. Recoveries from this soil increased from 41 to 76% with decreasing pH. For soils at natural pHs, when a weak acid modifier (benzoic acid) was used in addition to methanol, the 2,4‐D recovery ranged from 21 to 86%, increasing with decreasing organic C concentration. Treating the samples to the lowest pHs practical (1.2–1.6) with HCl and extracting with methanol‐modified supercritical CO2 was more successful than utilizing the weak acid‐methanol modifier, except for the soil with very low organic C. Recoveries after HCl treatment ranged from 80 to 94%. Two soils from 2,4‐D‐treated fields yielded more 2,4‐D by modified SFE at pH 1.2 than by a modified version of the method recommended by the U.S. Environmental Protection Agency. The results suggest that organic acids like 2,4‐D can be successfully extracted at low pH, even from soils high in organic C. Low recoveries from soils high in organic C appear to result from proton consumption by natural soil organic matter during extraction.
Effect of Different Organic Ligands on Cadmium Sorption by and Extractability from Soils
Authors: Naidu R. , Harter R. D. 
Published: July 2010

AbstractSoil solutions contain a variety of low molecular weight dissolved organics from breakdown of plant residues and exudation from plant roots, and complexation of metals by these organic ligands can play an important role in controlling metal solubility. The effect of the organic ligands acetate, citrate, fumate, malonate, maleate, salycylate, succinate, and tartrate on the extractability and sorption of Cd was investigated in a range of Cd‐treated soils varying widely in soil chemical characteristics. Experimental parameters were adjusted to investigate the effect of pH and organic ligand concentration on Cd extractability. The soils were also extracted with NaNO3 of equivalent pH and concentration. The organic ligands always extracted more Cd than did NaNO3, indicating that organic complexation increased the extractability of Cd from soil. Extractable Cd ranged from <0.30 to 1 µmol kg−1; the greatest Cd concentration in each soil was released in the presence of maleate. In general, the ability to desorb Cd followed the order: maleate > fumarate ≈ succinate > tartrate > malonate > oxalate > salicyclate when the pH of the extract was between 3.1 and 3.4; in this pH range competition for complexation between the metal ion and ligand anion is greater than the affinity of the metal ion for the soil surface. For all soils and organics, extractable Cd decreased with increasing pH of the ligand solutions. The amount of NaNO3‐extractable Cd also decreased with increasing pH, and the amount desorbed was not detectable at pH values exceeding 5.5, suggesting that at high pH values, Cd is released into soil solution only as metal‐organic complexes.
Removal of Nitrite Impurity from Nitrate Labeled with Nitrogen‐15
Authors: Malone John P. , Stevens R. James 
Published: July 2010

AbstractPotassium nitrate labeled with 15N is often used as a tracer in studies of N dynamics in soil and water systems. Typically, 0.8% NO−2 impurity has been found in the batches of K15NO3 enriched to 99 atom % excess 15N that were purchased by our laboratory. Nitrite is an intermediate in several N cycling processes so its addition when adding NO−3 could produce misleading results. We have developed a safe, simple, and inexpensive method to remove NO−2 impurity from any NO−3 solution in a water matrix. The principle is the oxidation of NO−2 to NO−3 by UV light in the presence of a heterogenous TiO2 catalyst. A NO−2 concentration of 0.2 mM in 100 mL of 0.2 M NO−3 solution could be oxidized in 12 min using 0.5 g L−1 TiO2 in a specially constructed photoreactor with a 75‐W UV facial tanning lamp. For the routine removal of NO−2, use of the same TiO2 concentration in a standard beaker worked equally well when the irradiation time was extended to 2.5 h. After irradiation, the TiO2 is easily and totally removed from the solution by membrane filtration.
Simulating the Impact of Management Practices on Nitrous Oxide Emissions
Authors: Xu C. , Shaffer M. J. , Al‐kaisi M. 
Published: July 2010

AbstractEffective evaluation of alternative management strategies to control global warming requires tools for simulating emissions of N2O from soils across a range of soil properties, weather, and management inputs. We hypothesized that with modification to the nitrification and denitrification submodels of the Nitrate Leaching and Economic Analysis Package (NLEAP) model, we could simulate daily N2O emissions as a function of soil moisture, temperature, N content, and other factors. Field parameterization was conducted on an Ulm clay loam soil (a fine, montmorillonitic, mesic Ustollic Haplargid) and validation experiments for N2O gas emissions were performed on an on‐farm swine effluent study site on a Valent sandy soil (a mixed, mesic Ustic Torripsamment). The unitless model parameters reflecting the maximum fraction of selected N transformations emitted as N2O for nitrification (αN), wet‐period denitrification (αw), and dry‐period denitrifiation (αd) were calibrated as 0.065, 0.050, and 0.520 separately and then used in the validation study. The trends and magnitudes of simulated N2O emissions were statistically consistent with the results obtained from the field experiments (r = 0.78). Experimental results showed that the decline of N2O emission rates from 70 to 2 g N ha−1 d−1 during the growing season was related to soil N content decline from 33 to 4 mg kg−1. Simulated effects of field management on annual N2O emissions indicated that plowing decreased N2O relative to notillage corn (Zea mays L.), irrigation increased N2O 14% relative to dry‐land corn, and doubling fertilization N rates from 100 to 200 kg ha−1 increased N2O emissions 60%.
Distribution of Zinc and Lead Fractions within a Forest Spodosol
Authors: Johnson Chris E. , Petras Robert J. 
Published: July 2010

AbstractSoil processes play a critical role in the fate of trace metals in forest ecosystems. To explore the nature of soil‐trace metal interactions, we estimated five fractions of Zn and Pb in Spodosols at the Hubbard Brook Experimental Forest in central New Hampshire: (i) soluble + exchangeable (EX); (ii) inorganically bound (IB); (iii) organically bound (ORG); (iv) amorphous oxide bound (AMOX); and (v) mineral lattice, or residual (RES). Organic matter is a critical factor in trace metal fractionation in Hubbard Brook soils; loss‐on‐ignition was strongly correlated to EX Zn (r = 0.91) and Pb (r = 0.85), and ORG Zn (r = 0.57) and Pb (r = 0.89). The Oa horizon accounted for only 1.9% of the soil mass above the C horizon, but contained 23% and 77%, respectively, of the EX Zn and Pb in the soil. Lead was more tightly held in the soil than Zn; the percentage of total metal in the EX fraction was greater for Zn than Pb in all horizons. Through biocycling, Zn is returned to the forest floor, helping to maintain labile pools in upper soil horizons. Nevertheless, the EX Zn pool (6.03 kg ha−1) is insufficient to replace the pool of Zn in aboveground tissues (6.87 kg ha−1). Lead, not a nutrient, has accumulated in the soil due to the combustion of leaded gasoline. Lead leached from the O horizon between 1926 and 1991 can account for 30% of the EX + IB + ORG Pb, or 14% of the labile Pb in the mineral soil.
Alteration of Arsenic Sorption in Flooded‐Dried Soils
Authors: McGeehan Steven L. , Fendorf Scott E. , Naylor Denny V. 
Published: July 2010

AbstractArsenic is known to be immobilized in soils through oxyanion sorption reactions involving metal (hydr)oxides. While the mechanisms involved in oxyanion sorption are relatively well characterized in aerobic systems, the response of (hydr)oxides to fluctuating soil redox conditions, and its impact on As sorption, is poorly understood. This study investigated the influence of soil flooding and drying on As sorption and Fe fractionation. Four soils exhibiting a range in As sorption capacity were incubated under flooded (anaerobic) conditions. After the flooding period, the pH and redox potentials of each soil suspension were measured and saturation indices were calculated for standard soil minerals. The suspensions were air dried at room temperature and the short‐range order Fe (oxalate‐extractable) and crystalline Fe (dithionite‐extractable) fractions determined. Separate flooded‐dried samples were resuspended in 0.1 M NaCl for AsO4 sorption measurements. Prolonged soil flooding resulted in a decrease in soil redox potential and an increase in dissolved Al, Fe, Mn, and Si. Drying the previously flooded soils resulted in an increase in As sorption. Selective extraction indicated that the flooding‐drying treatments increased the short‐range order Fe fraction while depleting the free oxide fraction. These changes in Fe mineralogy most likely increased the surface area and number of potential As sorption sites.
Determination of Parameters for Bimodal Hydraulic Functions by Inverse Modeling
Authors: Zurmühl Torsten , Durner Wolfgang 
Published: July 2010

AbstractTo determine the hydraulic properties of soils, transient flow experiments on soil samples and their evaluation by parameter identification methods have become common. In the past, the feasibility of this method has been investigated for soils exclusively with unimodal poresize distributions. In this work we investigated, both from a theoretical and from an experimental point of view, whether hydraulic properties of structured soils with bimodal pore‐size characteristics can be identified by inverse simulation. Multistep outflow experiments were simulated for three hypothetical soils with different degrees of bimodality. The outflow data thus created were then used in the inverse procedure, both in the original form and with an added random error. An analysis of sensitivity coefficients for the model parameters showed that if the bimodality of the pore system is well developed, the parameters of the bimodal hydraulic functions are uncorrelated and can be identified. This was confirmed by inverse optimization runs with simultaneous optimization of up to six parameters, which consistently converged from different initial values to the true parameter values, indicating uniqueness of the inverse problem. Attempts to fit the bimodal outflow data with simulations using unimodal hydraulic functions were not successful, as expressed by systematic disagreement between fitted and “observed” data and nonuniqueness of the inverse solution. We validated these theoretical results with experimental data from an undisturbed sandy forest soil, which showed that it is possible to determine the retention parameters of bimodal hydraulic properties by inverse modeling of multistep outflow experiments.
Texture and Electrical Conductivity Effects on Temperature Dependency in Time Domain Reflectometry
Authors: Persson Magnus , Berndtsson Ronny 
Published: July 2010

AbstractIf not accounted for, temperature effects on the water content and electrical conductivity measured with time domain reflectometry (TDR) will introduce significant errors. In this study, an automated TDR system was used to quantify the temperature dependence of the apparent dielectric constant and electrical conductivity in wet soils. Sandy, clayey, and organic soils were used to examine the effect of soil texture. The temperature correction factor for water content measurements was predicted, by using different dielectric mixing models, to lie between −0.00253 and −0.00419θ°C‐1, the negative value of the temperature correction factor indicating a decrease in the water content measurements with increasing temperature. These values agreed well with the correction factor measured in sandy soils: −0.00269θ°C‐1. In soils with large specific surface, i.e., clayey and organic soils, however, the temperature dependence was significantly lower. Large specific surface combined with high soil solution electrical conductivity resulted in a positive correction factor, i.e., water content measurements increased with increases in temperature. The temperature dependence of the bulk electrical conductivity was investigated using different soils and soil solutions. The temperature dependence was close to that of the soil solution and was independent of soil texture.
Nitrogen Application Timing Effects on Nitrogen Efficiency of Dry‐Seeded Rice
Authors: Wilson, C. E. , Bollich P. K. , Norman R. J. 
Published: July 2010

AbstractOptimum N application timing contributes significantly to successful rice (Oryza sativa L.) production. In many areas of the southern U.S. Rice Belt, where rice is produced in a dry‐seeded, delayed‐flood system, optimum fertilizer timing has traditionally been achieved by applying 50 to 65% of the total N required onto dry soil immediately prior to establishing the permanent flood and the remainder in one or two applications near the beginning of reproductive growth. Field studies were conducted during 1992 and 1993 at two locations to evaluate the optimum timing for midseason N applications. ‘Laccassine’ rice was grown in microplots (0.58 m2) established with galvanized steel collars. Nonlabeled urea was applied at the four‐ to five‐leaf growth stage at rates of 0, 67.2, and 134.4 kg N ha‐1 just prior to flooding. Nitrogen‐15 labeled urea was applied at midseason at a total rate of 67.2 kg N ha‐1 in four different treatments: (i) 67.2 kg ha‐1 at panicle initiation (PI) (PI‐1), (ii) 67.2 kg ha‐1 at panicle differentiation (PD) (PD‐1), (iii) 33.6 kg ha‐1 each at PI and PI + 10 d (PI‐2), and (iv) 33.6 kg ha‐1 each at PD and PD + 10 d (PD‐2), in addition to a zero‐N treatment. Plant samples were collected to measure total dry matter, fertilizer and total N uptake, and grain yields. Fertilizer N uptake was not affected by midseason N application timing during 1992 and was only slightly affected during 1993. Increasing the pre‐flood N rate significantly increased midseason fertilizer N uptake efficiency, total N uptake, total dry matter accumulation, and grain. Midseason N applications increased total dry matter accumulation, total N uptake, and grain yields compared with no midseason N at one location, but were minimally influenced at the other location. Results suggest that no real advantage is gained from split application of midseason N compared with a single application at midseason and that it can be made from PI to PD growth stage.
Phosphorus Diffusive Flux as Affected by Phosphate Source and Incubation Time
Authors: Villani E. M. A. , Barros N. F. , Novais R. F. , Costa L. M. , Neves J. C. L. , Alvarez V. V. H. , Comerford N. B. 
Published: July 2010

AbstractPhosphorus supply to eucalypts is deficient in many Brazilian soils and must be augmented with fertilizers to promote economic growth of plantations. Diffusion is generally considered to be the major mechanism of P fertilizer movement in these types of soils; therefore, we studied the effect of P fertilizer source and time of incubation of fertilizer with soil on the P diffusive flux in four Oxisols. Five soluble P sources [Ca(H2PO4)2, NH4H2PO4, (NH4)2HPO4, Na2HPO4·2H2O, and K2HPO4] were applied to the soils at a rate of 500 g P m‐3 soils. Microscope slides were covered with anion‐exchange paper (filter paper impregnated with Fe hydroxide) and laid between two soil layers in a diffusion chamber. Fifteen days later, P was extracted from the exchange paper and analyzed. Five hundred grams P m‐3 soil as the Ca source were also applied to soil samples and incubated for 30 d. Phosphorus diffusive flux was measured as described above. The Ca source of P reduced P diffusive flux by as much as 77% compared with the other sources. This reduction was attributed to the effect the P source had on soil pH. Sandy soils showed less difference between P sources than did clayey soils because the P applied to the sandy soils was in excess of their maximum sorptive capacity. Incubation for 30 d reduced P diffusive flux by up to 81%. Different P sources affect the availability of P in these soils by influencing mobility. Choosing the best source can increase diffusive flux by up to 242% under these soil conditions.
Soil Warming: Consequences for Foliar Litter Decay in a Spruce‐Fir Forest in Maine, USA
Authors: Rustad Lindsey E. , Fernandez Ivan J. 
Published: July 2010

AbstractIncreased rates of litter decay due to projected global warming could substantially alter the balance between C assimilation and release in forest soils, with consequent feedbacks to climate change. This study was conducted to investigate the effects of soil warming on the decomposition of red spruce (Picea rubens Sarg.) and red maple (Acer rubrum L.) foliar litter at Howland, ME. Experimentally increased Oa horizon soil temperatures (increase of 4–5°C) were maintained during the snow‐free season from 1993 through 1995 in replicated 15 by 15 m plots using heat‐resistance cables. For red maple litter, significant treatment effects included greater loss of mass (27%) and C (33%), and greater accumulation of Zn (54%) during the first 6 mo of decay in the heated plots than the control plots. After 30 mo of decay, significant treatment effects were no longer evident for red maple litter. Few treatment effects were observed for red spruce litter during the initial 18 mo of decay. However, after 30 mo of decay, significant treatment effects included greater loss of mass (19%), C (19%), N (24%), Ca (27%), Mg (12%), K (4%), Zn (60%), and cellulose (40%) in red spruce litter in the heated plots than the control plots. We conclude that a modest increase in Oa horizon soil temperature (4–5°C) can significantly increase litter decay rates and alter litter decay dynamics in this coniferous forest stand, and that these changes exhibit variations in their temporal development as a function of species and litter quality attributes.
Nitrous Oxide Emissions from Agricultural Soils of the Boreal and Parkland Regions of Alberta
Authors: Lemke R. L. , Izaurralde R. C. , Malhi S. S. , Arshad M. A. , Nyborg M. 
Published: July 2010

AbstractThe contribution of agricultural soils to atmospheric N2O in the Boreal and Parkland regions of Alberta is largely unknown. Field data are required to quantify the flux of N2O from these regions, as are methodologies to scale up from site‐specific measurements to large geographical areas. Climate‐soil‐management combinations (CSMCs) aggregated to an ecodistrict level have recently been proposed as a technique for scaling up greenhouse gas flux estimates for Canadian agriculture. Our objective was to calculate seasonal N2O losses and investigate large‐scale spatial variability using field data from selected sites in the Boreal and Parkland regions. We used vented soil covers to measure N2O emissions during spring and summer of 1993 and 1994, and the spring of 1995, from six representative CSMCs in five ecodistricts in Alberta. Substantial and consistent differences in the magnitude of N2O‐N loss among sites were observed, with annual estimated losses of N2O‐N ranging from 0.4 to 2.6 kg ha‐1. Up to 70% of the total annual N2O‐N loss occurred during brief but intense bursts at spring thaw. Soil clay content was found to be strongly correlated with annual N2O‐N loss. This relationship suggests that clay content, readily available from soil data bases, could be used as a N2O‐loss predictor variable when applying scaling‐up methodologies.