bluuebunny/crossref_metadata_2025_split huggingface dataset:
Agricultural Chemical Discharge in Surface Water Runoff
Authors: Smith S. J. , Sharpley A. N. , Ahuja L. R. 
Published: July 2010

AbstractThe discharge of agricultural chemicals (i.e., soil‐fertilizer nutrients and pesticides) in runoff waters is important from both agronomic and environmental standpoints. Presented here is an overview of our current concepts and approaches employed for describing this discharge, based on studies we have conducted over the past decade. Most of our field testing and validation of concepts regarding chemical discharge has focused on approximately 24 grassland and cropland watersheds across the Southern Plains. Chemicals considered include N, P, K, S, atrazine [2‐chloro‐4(ethylamino)‐6‐(isopropylamino)‐s‐triazine], alachlor [2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl) acetanilide], and cyanazine [2‐[[4‐chloro‐6‐(ethylamino)‐s‐triazine‐2‐yl]amino]‐2‐methylpropionitrile]. Soluble chemical discharge has been described by kinetic desorption and uniform or nonuniform mixing approaches, incorporating parameters reflecting watershed management and the nature of the surface soil × precipitation interaction. Particulate chemical discharge has been described by the relationship between the discharge enrichment ratio (chemical content of eroded sediment/source soil) and soil loss. Special situations considered include type of tillage, computed water and sediment runoff, severe storms, bioavailability of P, cover crops, and manure applications. For the most part, predicted chemical discharge values compared favorably with their measured counterparts, r2 values often being >0.9. Further research needs include refinement and development of the prediction equations, data bases, runoff indices, and multidisciplinary systems.
A Pragmatic Field‐Scale Approach for Modeling Pesticides
Authors: Hutson J. L. , Wagenet R. J. 
Published: July 2010

AbstractEnvironmental assessments of the fate of pesticides and other agricultural chemicals usually require estimation of chemical concentrations, with some indication of their accuracy. These estimations are usually based on a few measurements combined with existing data bases and predictive tools that include regression equations, empirical relationships, and simulation models. Comprehensive simulation models are attractive from a scientific standpoint, since they consider leaching of the chemical by water as well as the various chemical, biological, and physical processes that affect the chemical's fate during its transport. A number of simulation modeling approaches have been developed to describe soil‐water‐chemical systems, but a fundamental question remains regarding the degree of model complexity required to simulate agrochemical movement to groundwater. Most model complexity in soil‐water‐chemical simulation models arises from the manner in which water flow and chemical transport are considered. It is therefore logical, especially for management purposes, to consider alternative, pragmatic, and yet sufficiently accurate approaches to the description of water flow and chemical transport. Such approaches would require less characterization of soil hydraulic and physical/chemical properties and would reduce computation time. A method for such simplification and use is described, starting with LEACHP, a model based on the Richards and convection‐dispersion equations. The resulting model is shown to be sufficiently accurate for many management decisions.
A Field Study to Evaluate Leaching of Aldicarb, Metolachlor, and Bromide in a Sandy Loam Soil
Authors: Smith Charles N. , Parrish Rudolph S. 
Published: July 2010

AbstractTransport and transformation of pesticides used in agricultural situations are subject to variability from several sources that are impossible to simulate in laboratory settings. This study was conducted to characterize pesticide leaching behavior under conventional cropping conditions and to determine the impacts of related sources of variability. An agricultural field site (Ardilla fine sandy loam, Clarendon loamy sand, Tifton loamy sand, and Lucy loamy sand) located within the Dougherty Plain region of southwest Georgia was used to study pesticide movement in unsaturated and saturated soil zones from 1984 through 1988. A granular formulation of aldicarb [2‐methyl‐2‐(methylthio) propionaldehyde O‐(methylcarbamoyl) oxime], an emulsifiable concentrate of metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide], and a bromide (Br−) tracer were applied on peanut (Arachis hypogea L.) crops under modified conventional tillage practices. Postapplication vertical movement was monitored for periods of up to 111 d for pesticides and 1307 d for Br−. Application distributions for aldicarb showed measured coefficients of variation ranging from 42 to 72, and for metolachlor from 23 to 44. Spatial variability analyses indicated the existence of small‐scale correlation for both pesticides upon initial application, and some large‐scale trending was observed for metolachlor. Field‐based transformation rates of aldicarb were up to three times higher than laboratory‐based values. There was no evidence of migration of any of the pesticides into the saturated zone during the study, although Br− was observed at less than 1 mg kg−1 in well‐water samples. Aldicarb degraded almost completely within 90 d each year, and it was not observed below 1.2 m. Metolachlor profiles always showed concentrations decreasing with increasing depth, and there was no significant movement below 0.3 m. Bromide was observed in soil samples as deep as 3 m only on the 1307th d, and the profiles showed peak concentrations no lower than 1.5 m with relative vertical dispersion increasing continuously.
Relationship between Soluble and Extractable Phosphorus in Some Calcareous Soils of Iran
Authors: Sichani Seifollah Amin , Parsa Shahrokh Zand , Nelson D.W. 
Published: July 2010

AbstractThe relationship between water‐extractable P (soluble P) and NaHCO3‐extractable P was determined in different water/soil ratios. The values of 0, 45, 90, and 180 mg kg−1 soil as KH2PO4 were added to seven calcareous soil series from southern Iran (for two soil series additional P rates of 360, 720, and 1080 mg P kg−1 soil as KH2PO4 also was employed). Soluble P in water/soil ratios of 10:1, 25:1, 100:1, and 500:1 was measured by Murphy and Riley method (1962) after 2 h shaking. Sodium bicarbonate—extractable P also was determined in all soils. The results indicate that there was a linear relationship between the logarithm of soluble and NaHCO3‐extractable P when NaHCO3‐extractable P was less than 150 mg P kg−1 soil. There also was a linear relationship between soluble P and the water/soil ratio up to 100:1 for these soils. The amount of P released per unit soil weight at water/soil ratios greater than 100:1 was approximately constant.
Atrazine and Alachlor Losses from Subsurface Tile Drainage of a Clay Loam Soil
Authors: Buhler D. D. , Randall G. W. , Koskinen W. C. , Wyse D. L. 
Published: July 2010

AbstractHerbicide losses in subsurface drainage from agricultural land is not well understood. Research was conducted to assess atrazine [6‐chloro‐N′‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] and alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide] losses in subsurface tile drainage during and after long‐term use on a Webster clay loam soil (Typic Haplaquoll) at Waseca, MN, under typical agricultural management conditions. Individual subsurface drainage systems were installed in 1975 to plots cropped continuously to corn (Zea mays L.) under moldboard plow and no‐tillage systems. Annual alachlor and atrazine use was initiated in 1974 and 1975, respectively. Alachlor use was continued through 1991 while atrazine use was terminated after the 1988 application. Tile drainage water was collected and analyzed for atrazine and alachlor beginning in October 1985. Alachlor was detected in only 2% of the samples from 1985 through 1991. Atrazine was detected in 97% of the samples from 1985 through 1990. Atrazine detection frequency declined to 78% in 1991. Atrazine concentration in October 1985 was 0.56 µg L−1. Average atrazine concentration in tile drainage water in 1986 was 1.0 µg L−1 and estimated loss by leaching was 4.1 g ha−1. Average atrazine concentrations in 1987 and 1988 were 1.24 and 0.84 µg L−1, respectively, but due to limited tile flow, atrazine losses were less than 1 g ha−1 each year. Twelve to 18 mo after the last atrazine application, average atrazine concentration in tile water did not decline. However, from 24 to 30 mo after the final atrazine application, average concentration dropped to 0.42 µg L−1 and during the following growing season average concentration declined to 0.29 µg L−1. There was little fluctuation in atrazine concentration during any year. Tillage systems had minimal impacts on atrazine concentration or loss in tile drainage water. This research indicates that low concentrations of atrazine may contaminate tile drainage water during and after long‐term use and may persist for several years after use is stopped. Contamination of drainage from similar use of alachlor appears minimal.
Hydrologic and Land‐Use Factors Associated with Herbicides and Nitrate in Near‐Surface Aquifers
Authors: Burkart Michael R. , Kolpin Dana W. 
Published: July 2010

AbstractSelected herbicides, atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) metabolites, and NO−3 were examined in near‐surface unconsolidated and bedrock aquifers in the midcontinental USA to study the hydrogeologic, spatial, and seasonal distribution of these contaminants. Groundwater samples were collected from 303 wells during the spring and late summer of 1991. At least one herbicide or atrazine metabolite was detected in 24% of the samples collected for herbicide analysis (reporting limit 0.05 µg/L). No herbicide concentration exceeded the USEPA's maximum contaminant level (MCL) or health advisory level. The most frequently detected compound was the at razine metabolite deethylatrazine [2‐amino‐4‐chloro‐6‐(isopropylamino)‐s‐triazine] followed by atrazine, deisopropylatrazine [2‐amino‐4‐chloro‐6‐(ethylamino)‐s‐triazine], prometon (2,4‐bis(isopropylamino)‐6‐methyoxy‐s‐triazine), metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1methylethyl)acetamide], alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide], metribuzin [4‐amino‐6‐(tert‐butyl)‐3‐methylthio‐as‐triazine‐5(4H)‐one], simazine [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine], and cyanazine [2‐[[4‐chloro‐6‐(ethylamino)‐1,3,5‐triazin‐2‐yl]amino]‐2‐methylpropionitrile]. Nitrite plus nitrate, as nitrogen (N), exceeding 3.0 mg/L (excess NO−3), was found in 29% of the samples, and 6% had −3 exceeding the MCL of 10 mg/L. Ammonium as N was detected in excess of 0.01 mg/L in 78% of the samples. A nonlinear increase in the frequency of atrazine detection occurred with decreases in reporting limit. The frequency of atrazine residue detection (atrazine + deethylatrazine + deisopropylatrazine) was 25% greater than for atrazine alone. Herbicide detections and excess NO−3 were notably lacking in the eastern part of the study region where it was estimated that herbicide and fertilizer use were among the largest in the region. Prometon, the second most frequently detected herbicide, was associated with non‐agricultural land use. Herbicide and excess NO−3 were more frequent in unconsolidated aquifers than in bedrock aquifers. Aquifer depth, as direct measurement of proximity to recharge sources, was inversely related to frequency of herbicide detection and excess NO−3.
Soil Loss as Affected by Different Combinations of Surface Litter and Rock
Authors: Benkobi Lakhdar , Trlica M. J. , Smith James L. 
Published: July 2010

AbstractThe effects of various surface cover types, their combinations, and bare ground on soil loss from a clay loam topsoil were studied on small plots in the laboratory using a rotating boom rainfall simulator. A total of 105 plots with various types and amounts of surface cover were exposed to simulated rainfall at 100 mm/h for 30 min. Cover treatments included herbaceous litter of sedges (Carex spp.) and bluegrass (Poa spp.), shrub litter of willows (Salix spp.), small rocks, and mixtures of these cover types at several levels of cover (0, 25, 50, 75, 100%) and bare ground (control). Experimental data for high intensity storm were used to develop an equation to quantify soil loss and surface cover relationships for a clay loam soil. Regression analysis indicated high correlation (R2 = 0.86) between soil loss and types and amounts of surface cover. Soil loss from bare plots was about 13 000 kg/ha. A surface cover proportion of about 0.60 for vegetation litter, and 0.85 for rock, would reduce soil loss to about 5000 kg/ha. Rocks were not as effective as vegetation litter in our experiment in protecting the soil from erosion. However, surface coverage of 100% with combinations of vegetation litter and rocks offered the best protection of the soil against erosion. This combination was better than either 100% vegetation litter cover or 100% rock cover alone. Rock in combination with vegetation litter may have increased roughness and allowed deposition of sediment.
Reducing Soil Erosion and Agricultural Chemical Losses with Conservation Tillage
Authors: Seta A. K. , Blevins R. L. , Frye W. W. , Barfield B. J. 
Published: July 2010

AbstractAs nonpoint source pollution of water becomes more evident, more concern is being focused on the effects of agricultural practices on water quality. This study evaluated the effects of conventional tillage (CT), chisel‐plow tillage (CP), and no tillage (NT) on the quality of runoff water from a Maury silt loam soil (fine, mixed, mesic Typic Paleudalf) near Lexington, KY. The mean runoff rate, total runoff volume, mean sediment concentration, and total soil losses were significantly less for NT than for CP and CT. Concentration of NO−3, NH+3, and PO3−4 in the runoff water from NT were greater than from CP or CT. Concentration of atrazine [6‐chloro‐N‐ethyl‐N′‐(I‐methylethyl)‐1,3, 5‐triazine‐2,4‐diamine] in the runoff water tended to be higher from CP than from NT or CT. Total losses of NO−3, NH+4, PO3−4, and atrazine in runoff water were generally in the order CT > CP > NT. The sum of all chemicals lost was less than 3% of the total amount of each applied.
Thermodynamic Modeling of Zinc, Cadmium, and Copper Solubilities in a Manured, Acidic Loamy‐Sand Topsoil
Authors: Hesterberg Dean , Bril Jan , del Castilho P. 
Published: July 2010

AbstractSoil solution samples collected during a 14‐mo period from manured, loamy‐sand soil profiles in the Netherlands showed variations in dissolved Zn, Cd, and Cu concentrations of up to two orders of magnitude. To try to account for variations in the dissolved metals, a thermodynamic model was developed for the chemical‐equilibrium computer program CHARON. In addition to solution complexation and solid‐phase precipitation of inorganic components, the model accounted for metal complexation with dissolved organic carbon (DOC) ligands and with a solid organic matter (OM) exchanger phase. Both dissolved and solid organic materials were assumed to behave like fulvic acid having a complexing capacity for Zn2+, Cd2+, Cu2+, Ca2+, Mg2+, and Al3+ of 2 tool kg−1 of C. To obtain a single (pH‐dependent) stability constant for each metal‐organic ligand complex, stoichiometries of 1:1:n metal/organic‐ligand/OH− complexes were determined from published linear relationships between pH and average equilibrium quotients normalized for complexing capacity of a polyfunctional complexer. Exchange in the exchanger phase included monovalent cations and anions to maintain phase electroneutrality. Model predictions of dissolved Zn, Cd, and Cu were calculated from relevant soil properties and macrochemical concentrations in each of 44 soil‐solution samples collected from three manured field plots. Model‐predicted Zn and Cd concentrations deviated from measured concentrations on the average 1.4‐ and 2‐fold for measured concentration ranges of 120‐ and 34‐fold (respectively). Copper was typically underpredicted by the model. Model‐predicted speciation between the two principal dissolved metal species, free‐ionic and DOC ligand‐complexed, varied depending on soil solution macrochemistry. Soil solution chemical conditions ranged from pH 4.5 to 6.7, 30 to 260 g DOC m−3, and electrical conductivities (EC) of 15 to 510 mS m−1.
Resin Adsorption for Describing Bromide Transport in Soil under Continuous or Intermittent Unsaturated Water Flow
Authors: Li Z. M. , Skogley E. O. , Ferguson A. H. 
Published: July 2010

AbstractAccurate information on movement of soil‐applied chemicals toward water tables is necessary for improving agricultural and environmental management. Current methods for studying related processes have major limitations. Objectives of this research were to investigate resin capsule adsorption for measuring Br− transport, to compare results with those from vacuum extraction, and to determine the utility of resin capsule technology for field studies. Laboratory experiments were conducted with a uniformly packed soil column under continuous or intermittent, unsaturated water flow using Br− as a tracer. Field experiments were also conducted with intermittent water flow applied by a line‐source irrigation system. Bromide accumulated by mixedbed ion‐exchange resin capsules inserted into the soil at several depths in the soil column was compared with Br− in solutions collected at the same depths by vacuum extraction through porous ceramic candles. Delayed timing of peak Br− leaching patterns (BLPs) at the uppermost sampling point, and earlier peak BLPs at the lowest sampling depth, when resin capsule data were used, suggest that the accuracy of measuring Br− transport is method‐dependent. Under intermittent water flow, distinct spikes of BLPs measured by resin capsules corresponded to soil water potential changes. Only broad plateaus for BLPs were measured with vacuum extraction, implying greater sensitivity of the resin capsule methodology to soil moisture changes. Field results demonstrated the utility of resin capsules for detecting Br− transport as influenced by irrigation intensity, plant water use, and plant Br− uptake. The resin capsule methodology may provide a simple, accurate alternative to vacuum extraction or repetitive soil sampling for studying solute transport. It provides “in situ solid‐phase extraction” of the target solute simultaneously with other ions in soil solution.
Soil Cadmium Mobility as a Consequence of Sewage Sludge Disposal
Authors: Lamy I. , Bourgeois S. , Bermond A. 
Published: July 2010

AbstractAnaerobically digested liquid sewage sludge was applied as a single treatment to a loamy hydromorphic drained soil, characteristic of agricultural soils in the North of France, at a rate of 11 Mg of dry solids ha−1. Total Cd concentrations of drainage waters for both amended and unamended plots were monitored at selected times to follow the mobility of Cd after sludge disposal. The drained groundwater of the plot that exhibited the highest discharge of sludge soluble organic matter (SSOM) exhibited about twice the Cd levels of the control plot during the first few weeks following sludge disposal (average of 3 and 1.5 µg L−1, respectively). Laboratory experiments were conducted to provide estimates of the relative binding strength of Cd‐soil interactions as well as Cd‐SSOM interactions. The behavior of Cd in a mixed sludge‐soil system showed that the addition of sludge soluble organic matter to the soil led to a decrease in the sorption of this cation across the pH range between 5 and 7. The laboratory studies highlighted the role of soluble organic matter in soil Cd speciation, and can be used to speculate on the perturbations induced by high levels of sludge soluble organic matter introduced into a soil.
Technique for Measuring Air Flow and Carbon Dioxide Flux in Large, Open‐Top Chambers
Authors: Ham Jay M. , Owensby C. E. , Coyne P. I. 
Published: July 2010

AbstractOpen‐Top Chambers (OTCs) are commonly used to evaluate the effect of CO2, O3, and other trace gases on vegetation. A study was conducted to develop and test a new technique for measuring forced air flow and net CO2 flux from OTCs. Experiments were performed with a 4.5‐m diam. OTC that had a sealed floor and a specialized air delivery system. Air flow through the chamber was computed with the Bernoulli equation using measurements of the pressure differential between the air delivery ducts and the chamber interior. An independent measurement of air flow was made simultaneously to calibrate and verify the accuracy of the Bernoulli relationship. The CO2 flux density was calculated as the product of chamber air flow and the difference in CO2 concentration between the air entering and exhausting from the OTC (Cin ‐ Cout). Accuracy of the system was evaluated by releasing CO2 within the OTC at known rates to emulate respiration from the field surface. Data were collected with OTCs at ambient and elevated CO2 (≈700 µmol mol−1). Results showed that the Bernoulli equation, with a flow coefficient of 0.7, accurately measured air flow in the OTC to within ±5% regardless of flow rate and air duct geometry. Experiments in ambient OTCs showed that CO2 flux density (µmol m−2 s−1), computed from 2‐min averages of air flow and Cin ‐ Cout, was typically within ±10% of actual flux, provided that the exit air velocity at the top of the OTC was greater than 0.6 m s−1. Obtaining the same level of accuracy in CO2‐enriched OTCs, however, required a critical exit velocity near 1.2 m s−1 to minimize the incursion of ambient air and prevent contamination of the exit gas sample. When flux data were integrated over time to estimate daily CO2 flux (µmol m−2 d−1), actual and measured values agreed to within ±2% for both ambient and CO2‐enriched chambers, suggesting that accurate measurements of daily net C exchange are possible with this technique.