bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observed and Simulated Solute Transport Under Varying Water Regimes: I. Bromide and Pentafluorobenzoic Acid
Authors: Pearson R. J. , Inskeep W. P. , Wraith J. M. , Comfort S. D. , Gaber H. M. 
Published: July 2010

AbstractComparison of observed and predicted solute transport under field conditions is a necessary component for validating various modeling approaches. The objectives of this study were to compare transport of Br− and pentafluorobenzoic acid (PFBA) under cropped and fallow conditions for a range of soil water contents and evapotranspirative demands, and to evaluate the predictive capability of a computer simulation model (LEACHM) using independent estimates of model input parameters. A field study was conducted (1991) using in situ columns (0.2 m diam., 1.22 m depth) on a Brocko silt loam (mixed, mesic Borollic Calciorthid) in Gallatin Co., MT. The transport of two tracers (Br− and PFBA) was measured at three depths (0.36, 0.66, and 0.96 m) for three water regimes under cropped (barley, Hordeum vulgare L.) and fallow conditions for 60 d following chemical application. Observed breakthrough curves (BTCs) demonstrated increased travel times with increasing depth and decreasing water application. Solute transport in cropped columns was significantly slower than fallow as a result of higher evapotranspiration. Comparison of Br− and PFBA BTCs under cropped conditions suggested significantly greater plant uptake of Br− compared to PFBA. Predicted volumetric water contents, evaporation (under fallow conditions), and solute BTCs using LEACHM agreed favorably with observed results. Under cropped conditions, agreement between predicted and observed soil water contents was less favorable, most likely a result of inaccurate assumptions concerning depth‐dependent root water uptake. LEACHM‐predicted mean travel times (d) agreed within 22% of observed PFBA values for fallow conditions and within 9% of observed PFBA values for cropped conditions. Results indicated that adequate predictions of the transport of PFBA were obtained using LEACHM when coupled with independent estimates of model input parameters.
Nitrate and Water Present in and Flowing from Root‐Zone Soil
Authors: Weed D. A. J. , Kanwar R. S. 
Published: July 2010

AbstractFrom 1990 through 1992, we studied water and nitrate‐nitrogen (NO3‐N) present in the soil and flowing into a subsurface drainage system. Tillages were chisel plow (CP), moldboard plow (MB), no‐till (NT), and ridge‐till (RT). Crops were continuous corn (Zea mays L.) and a corn‐soybean [Glycine max (L.) Merr.] rotation. Tillage and crop only slightly influenced soil NO3‐N and water. Drainage water flows were highest for treatments that minimized soil disturbance and maximized crop residues produced during the previous year. The 3‐yr total flows by crop were 38 cm water for rotation‐corn plots, 56 for rotation soybean, and 59 for continuous corn. Flows by tillage were 41 cm water for MB plots, 52 for RT, and 55 for both CP and NT. In continuous corn, NT plots had more monthly water drainage than MB plots for most of 1990. Ridge‐till and CP plots had more drainage than MB plots for part of 1991. Crop rotation had the greatest effect on NO3‐N drainage loss. The 3‐yr total NO3‐N losses were 77 kg ha−1 for rotation corn plots, 84 for rotation soybean, and 164 for continuous corn. Tillage losses were 95 kg ha−1 for RT, 102 for MB, 106 for NT, and 131 for CP. No‐till and RT plots always had the lowest NO3‐N concentrations in drainage water; their yearly NO3‐N losses were usually smallest. Leaching can be best minimized by applying fertilizer in amounts to just meet crop N demand and at times closest to peak uptake.
Molybdate‐Reactive Phosphorus Losses in Surface and Drainage Waters from Permanent Grassland
Authors: Hawkins J. M. B. , Scholefield D. 
Published: July 2010

AbstractAlthough the loss of P in agricultural runoff can provide freshwater eutrophication, little information is available on losses from permanent grasslands. Thus, 14 lysimeter plots (each of 1 ha), established in 1982 on a clay loam soil under grazed grassland management, were monitored between 1989 and 1991 for release of molybdate‐reactive phosphorus (MRP). The plots enabled the daily measurement of discharge through field drains (to 85 cm) or by surface lateral runoff (to 30 cm). Sward type was either perennial ryegrass (Lolium perenne L.) or a perennial ryegrass‐clover (Trifolium sp.) mixture. The plots were grazed continuously by beef cattle and received either 200 or 400 kg N ha−1 yr−1 in various combinations. Having collected >7500 data points during the 3 yr, it was found that there was no significant difference between the effects of either agronomic or drainage variables (P > 0.05) within years. However, there was a significant difference (P < 0.05) between drainage variables when the data from the 3 yr were combined, as there were larger MRP losses from undrained treatments. There was no relationship between concentration of MRP and drainage volume. The MRP concentrations ranged from 0.01 to 0.7 mg L−1 with an average concentration of 0.02 mg L−1. Losses of MRP as great as 0.4 kg ha−1 yr−1 were measured in surface lateral runoff from undrained plots and 0.2 kg ha−1 yr−1 in water percolating through field drains. The data show this type of grassland system may have the potential to be an important diffuse source of P to fresh waters.
Herbicides in Karst Groundwater in Southeast West Virginia
Authors: Pasquarell G. C. , Boyer D. G. 
Published: July 2010

AbstractA field study was conducted to determine the karst groundwater impact of herbicide application to feed crops in support of livestock production in southeast West Virginia. Grab samples were taken on a weekly/biweekly schedule at three resurgences for two agriculturally intensive karst watersheds. Two surface water sites were also sampled. The samples were analyzed for the presence of 12 different analytes: atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine), its two metabolites, desethylatrazine (2‐chloro‐4‐ethylamino‐6‐amino‐1,2,5‐triazine) and desisopropylatrazine (2‐chloro‐4‐amino‐6‐isopropylamino‐1,3,5‐triazine), and nine additional triazine herbicides. Little impact was detected at the two surface water sites. In contrast, 6 of the 10 herbicides were detected in at least two of the three resurgences. Three of them, atrazine (ATR), metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide], and simazine [2‐chloro‐4‐6‐(ethylamino)‐s‐triazine], were detected in more than 10% of all samples at all three resurgences. ATR and desethylatrazine (DES) were detected in more than 50% of samples at all three resurgences; median ATR values were 0.060, 0.025, and 0.025 µg/L. DAR*, the ratio of DES to ATR plus DES, was used to differentiate atrazine leaching following storage for long periods in the soil, from transport that bypassed deethylation in the soil through sinkholes and other solutionally developed conduits. DAR* was low (median of <0.5) and highly varied during the periods immediately following ATR application, indicating that significant quantities of ATR were present. In the winter, a release of ATR metabolites from the soil was evidenced by a steadier, and higher DAR* (median of 0.64). The maximum detected ATR concentration was 1.20 µg/L, which is within the USEPA maximum contaminant level of 3 µg/L.
Distribution and Mineralization of Biosolids Nitrogen Applied to Dryland Wheat
Authors: Barbarick K. A. , Ippolito J. A. , Westfall D. G. 
Published: July 2010

AbstractThe greatest challenge in land application of biosolids (sewage sludge) for beneficial use is predicting N‐mineralization rates so that managers can amend the soil with an agronomic rate of material. We used 11 yr of field‐study information from biosolids addition to dryland hard‐red winter wheat (Triticum aestivum L. ‘Vona’ or ‘TAM107’) to determine not only the distribution of applied N but also to estimate net N mineralization rates. This study is unique since it involves multiple biosolids application in a dryland summer fallow agroecosystem. We applied five or six applications of biosolids from the cities of Littleton and Englewood, CO (L/E) to Weld loam (Aridic Paleustoll) or Platner loam (Abruptic Aridic Paleustoll) at four locations. This paper focuses on the O (control) and the 56‐ or 67‐kg N ha−1 fertilizer rate, and the 6.7 and 26.8 dry Mg biosolids ha−1 rates that we added every crop year. The 6.7 dry Mg biosolids ha−1 treatment resulted in the following average N distributions: 54% soil residual, 9% grain removal, and 38% unaccounted. At the larger application rate of 26.8 dry Mg biosolids ha−1 treatment, we found the following average N distributions: 35% soil residual, 2% grain removal, and 63% unaccounted. We estimated a net mineralization of 25 to 57% and a first‐year N net mineralization of 13 to 43% for 6.7 dry Mg ha−1 and a net mineralization of 62 to 78% and a first‐year N net mineralization of 41 to 67% for 26.8 dry Mg ha−1.
Composition and Decomposition of Soybean and Sorghum Tissues Grown under Elevated Atmospheric Carbon Dioxide
Authors: Henning F. P. , Wood C. W. , Rogers H. H. , Runion G. B. , Prior S. A. 
Published: July 2010

AbstractIt has been hypothesized that changes in both quantity and quality of plant residue inputs to soils as atmospheric carbon dioxide (CO2) concentration increases may alter carbon (C) and nitrogen (N) turnover rates and pool sizes. We determined the effect of elevated atmospheric CO2 on plant tissue quality, and how modifications in tissue quality affect C and N mineralization. Soybean [C3; Glycine max (L.) Merr. cv. Stonewall] and sorghum [C4; Sorghum bicolor (L.) Moen. cv. Savanna 5] were grown under elevated (704.96 ± 0.33 µmol CO2 mol−1) and ambient (357.44 ± 0.12 µmol CO2 mol−1) atmospheric CO2 in open‐top chambers. Leaf and stem tissues were separated from harvested plants and analyzed for C, N, lignin, and cellulose. Tissues were applied to Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudult) and aerobically incubated for 70‐d to determine C and N mineralization, C turnover, relative N mineralization, and C/N mineralized. Elevated CO2 had no effect on plant residue C concentration, but N concentration of soybean leaves and stems and sorghum stems was reduced; however, CO2 enrichment increased C/N ratio and lignin concentration for only sorghum stems and soybean leaves, respectively. Source of plant residue (i.e., produced under either elevated or ambient CO2) had no impact on soil C turnover, relative N mineralization, cumulative C and N mineralization, and C/N mineralized. These data suggest that increasing atmospheric CO2 will have little effect on composition or decomposition of field crop residues. Thus, since CO2 enrichment results in increased photosynthetic C fixation, the possibility exists for increased soil C storage under field crops in an elevated CO2 world.
Carbon Dioxide and Ozone Effects on Growth of a Legume‐Grass Mixture
Authors: Johnson B. G. , Hale B. A. , Ormrod D. P. 
Published: July 2010

AbstractAtmospheric carbon dioxide (CO2) and photochemical ozone (O3) have been increasing in the biosphere and will continue to do so with further industrialization and burning of fossil fuels. The purpose of this study was to examine the interaction of CO2 and O3 on plant growth and aboveground competition using a forage mixture of alfalfa (Medicago sativa L.) and timothy (Phleum pratense L.). Mixtures were grown at two CO2 levels (350 and 700 µL/L) in controlled environment chambers and exposed to four weekly O3 episodes of 8‐h duration with peak daily concentrations of 0.03, 0.08, 0.13, or 0.18 µL/L on Days (d) 21, 28, 35, and 42 after seeding. Roots of individual plants were in separate containers. The plants were harvested 2 d after the final O3 exposure. Total dry biomass of alfalfa and timothy was 50 and 40%, respectively, greater at 700 than at 350 µL CO2/L with low O3. Increasing peak O3 concentration decreased alfalfa shoot dry biomass at 700 µL CO2/L but not at 350 µL/L and decreased root dry biomass at both CO2 levels. In timothy, intermediate O3 levels reduced shoot growth but the highest level of O3 resulted in more shoot growth in the mixture at both CO2 levels. Partitioning of dry matter to alfalfa roots was strongly retarded by increasing O3, particularly in the CO2‐enriched environment, while timothy root growth was unaffected by O3. The enhancement of timothy shoot biomass in the mixture by exposure to the highest level of O3 at either CO2 level could not be fully explained by changes in competition between timothy and alfalfa in relation to differential O3 tolerance.
Spreader Performance Evaluation for Forest Land Application of Wood and Fly Ash
Authors: Wilhoit John H. , Ling Qingyue 
Published: July 2010

AbstractLand application is an important disposal alternative for ash, but materials handling and spreading difficulties are obstacles to increased utilization of this alternative, especially in forest situations. A horizontal spinner‐type spreader mounted on a forwarder, a specialized tractor for hauling logs out of the forest, was used to conduct distribution pattern trials spreading wood ash and fly ash in a pine (Pinus sp.) plantation stand. The materials were spread at two conveyor speeds, and the results were analyzed for application rate and spreading uniformity, as indicated by coefficient of variation (CV), at different simulated swath widths. Spreader uniformity was generally poor in comparison to standards for spreading fertilizer, and the uniformity results were inconsistent from one trial to the next. Both of the materials exhibited similar trends, however, with best uniformities (indicated by minimum CV values) occurring at both narrow (5.5–7.3 m) and wide (10.9–12.8 m) simulated swath widths. At the 19 cm s−1 speed, fairly high application rates were achieved with fly ash, which was dry and uniform in consistency. The wood ash, which was wet and mud‐like in consistency, could only be spread satisfactorily at a lower application rate (7.1 cm s−1 conveyor speed). For the operating conditions used in these tests, estimated costs (for spreading only) at an application rate of 10 Mg ha−1 ranged from $1.31 Mg−1 ($1.35 m−3) to $2.62 Mg−1 ($2.70 m−3), depending on loading and travel time requirements.
Evaluation of Beneficial Use of Wood‐Fired Boiler Ash on Oat and Bean Growth
Authors: Krejsl J. A. , Scanlon T. M. 
Published: July 2010

AbstractAn evaluation on the effects of pulp and paper mill combined boiler ashes on growth and nutrient uptake by oat (Avena sativa L., var. 501) and bean (Phaseolus vulgaris L., var. blue pole) was conducted in a greenhouse. Ash with a calcium carbonate equivalent of 29.1% and a pH of 12.1 was applied at the rates 30, 40, and 50 dry Mg ha−1 to Chehalis silty clay loam (fine‐silty, mixed, mesic Cumulic Ultic Haploxerolls), with pH 5.4. An agricultural dolomitic lime treatment of 7.4 Mg ha−1 and a nonamended control were also included. Plants grown on ash‐amended soil had higher biomass compared to plants grown on lime and control treatments. Ash treatments 30, 40, and 50 dry Mg ha−1 increased the bean (stems and leaves) dry matter (DM) yield over the control by 49, 57, and 64%, respectively. The lime treatment increased the bean DM yield by 31% compared with the control. The ash rate 30 dry Mg ha−1, equivalent to the recommended agronomic lime rate 7.4 Mg ha−1, increased oat (shoots) DM yields over the control by 45%, while the lime treatment increased biomass by 8% over control. The highest ash treatment, 50 Mg ha−1, produced the lowest oat biomass. The ash was as effective as dolomitic lime in raising soil pH. Ash‐amended soils contained higher concentrations of P, S, and B for plant growth compared to lime and nonamended soils. Soil Zn, Fe, Mn, and Cu concentrations decreased as ash application rates increased. Oat and bean plants grown in the ash‐amended soil had increased concentrations of K, S, and B and decreased concentrations of Mn and Cu compared with plants grown in the nonamended control soil. Overall, oat and bean benefited from the increased nutrient availability and soil pH caused by the application of boiler ash.
Optimizing Nitrogen and Irrigation Inputs for Corn Based on Nitrate Leaching and Yield on a Coarse‐Textured Soil
Authors: Sexton B. T. , Moncrief J. F. , Rosen C. J. , Gupta S. C. , Cheng H. H. 
Published: July 2010

AbstractA study was conducted on a Verndale sandy loam soil (coarse loamy over sandy, mixed, frigid Udic Argiboroll) during 1991 and 1992 at Staples, MN, to assess the influence of irrigation scheduling and N source and rate on corn (Zea mays L.) yield and nitrate leaching. Nitrogen sources were urea and turkey manure. Soils were irrigated to field capacity (i) at a fixed trigger deficit throughout the season, or (ii) at a variable trigger deficit based on crop growth stage. Leaching losses were calculated from measured daily fluxes of water percolation and soil water NO3‐N concentrations and from a seasonal N mass balance. Based on yield response curves, maximum corn grain yields were obtained at 202 and 234 kg N ha−1 urea in 1991 and 1992, respectively. This resulted in growing season leaching losses of 72 and 55 kg N ha−1 in 1991 and 1992, respectively. The rate at 95% of the maximum crop yield is suggested to substantially reduce nitrate leaching past the root zone. Using this guideline, nitrate leaching would be reduced by 35% compared with nitrate leaching at the maximum yield. When a variable available water deficit was used to schedule irrigation compared with a fixed deficit schedule (at 95% of maximum yield N rate), nitrate leaching was reduced 46%. At equivalent N rates, turkey manure produced equal or greater crop yields as that from urea applications; however, nitrate leaching was equal to or less than urea.
Atrazine Concentrations in Near‐Surface Aquifers: A Censored Regression Approach
Authors: Liu Shiping , Yen Steven T. , Kolpin Dana W. 
Published: July 2010

AbstractIn 1991, the U.S. Geological Survey (USGS) conducted a study to investigate the occurrence of atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) and other agricultural chemicals in near‐surface aquifers in the midcontinental USA. Because about 83% of the atrazine concentrations from the USGS study were censored, standard statistical estimation procedures could not be used. To determine factors that affect atrazine concentrations in groundwater while accommodating the high degree of data censoring, Tobit models were used (normal homoscedastic, normal heteroscedastic, lognormal homoscedastic, and lognormal heteroscedastic). Empirical results suggest that the lognormal heteroscedastic Tobit model is the model of choice for this type of study. This model determined the following factors to have the strongest effect on atrazine concentrations in groundwater:percent of pasture within 3.2 km, percent of forest within 3.2 km (2 mi), mean open interval of the well, primary water use of a well, aquifer class (unconsolidated or bedrock), aquifer type (unconfined or confined), existence of a stream within 30 m (100 ft), existence of a stream within 30 m to 0.4 km (0.25 mi), and existence of a stream within 0.4 to 3.2 km. Examining the elasticities of the continuous explanatory factors provides further insight into their effects on atrazine concentrations in groundwater. This study documents a viable statistical method that can be used to accommodate the complicating presence of censored data, a feature that commonly occurs in environmental data.
Bromide and Nitrogen‐15 Tracers of Nitrate Leaching under Irrigated Corn in Central Nebraska
Authors: Kessavalou Anabayan , Doran John W. , Powers William L. , Kettler Timothy A. , Qian Jin H. 
Published: July 2010

AbstractNitrate leaching from agricultural fields into groundwater has caused environmental and health concerns. A study was conducted during 1992–1993 in the Central Platte Valley of Nebraska to assess the nitrate leaching potential under recommended center‐pivot irrigation and fertilizer best management practices for continuous corn (Zea mays L.). At time of planting corn, potassium bromide (KBr) and double‐labeled 15N ammonium nitrate (10 atom% 15NH415NO3) tracers were applied at rates of 200 kg Br ha−1 and 30 kg N ha−1 to four 6.1 by 3.7 m plots that were representative of major soil types on the 32.1‐ha field. Soil and plants sampled 7 wk after planting and at harvest in 1992, and in the spring of 1993, were analyzed for Br and N content and a mass balance was determined. At corn harvest, 41% (81.9 kg ha−1) of the applied Br loss from the top 1.2 m of soil was attributed to leaching. Also, 54% (16.2 kg ha−1) of the tracer applied was lost from the system; 41% (12.3 kg ha−1) through leaching; and 13% (3.9 kg ha−1) through denitrification and volatilization. By time of planting in the spring of 1993, 70% (139.3 kg ha−1) of the applied Br and 46% (13.8 kg ha−1) of the fertilizer N leached below 1.2 m. High negative correlations were found between soil clay and silt contents, and Br or NO3 leaching. Despite use of best management practices for irrigation water and N applications, large amounts of nitrate can be lost through leaching under irrigated corn in this subhumid climate on fine‐ to medium‐textured soils.
Chemistry and Phytotoxicity of Soil Trace Elements from Repeated Sewage Sludge Applications
Authors: Berti W. R. , Jacobs L. W. 
Published: July 2010

AbstractMunicipal sewage sludges, or biosolids, can be applied to croplands to supply and recycle nutrients and organic C. Trace elements in sludges, however, may be of environmental concern. This study examines the long‐term consequences to crops and soil when loading phytotoxic levels of one or more trace elements to cropland. Municipal sewage sludges containing trace elements, including high concentrations of Cd, Cr, Cu, Pb, Ni, and Zn, were applied to cropland from 1977 to 1986 at three rates plus an untreated control. Plant and soil samples were collected between 1985 and 1990. These results report on yield and metal uptake of corn (Zea mays L.), sorghum‐sudangrass (Sorghum bicolor L. Moench × S. sudanese P. Stapf.), and soybean (Glycine max L.). Yields of all crops were reduced on one or more sludge treatments because of phytotoxic concentrations of soil trace elements, probably Zn and Ni. Phytotoxicity has continued since the last sludge application. Chemical fractionation of surface soils was performed using a sequential extraction technique and trace elements were measured in each of eight fractions. Cadmium, Ni, and Zn occupied soil fractions that were potentially available for plant uptake. Copper and Cr loadings increased the environmental availability of these two elements to a smaller extent. Loadings of Pb to the levels seen in this study did not appear to significantly increase its environmental availability. The Toxicity Characteristic Leaching Procedure (TCLP) and guidelines used to characterize hazardous wastes were inappropriate to use when testing soils for potential phytotoxic concentrations of trace elements or uptake of these elements into the food chain.