bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lysimeter Study of Nitrate Leaching from a Corn‐Soybean Rotation
Authors: Owens L. B. , Malone R. W. , Shipitalo M. J. , Edwards W. M. , Bonta J. V. 
Published: July 2010

AbstractHigh rates of N fertilizer in the production of continuous corn (Zea mays L.) have resulted in excessive nitrate N (NO3‐N) leaching, with concentrations in ground water frequently exceeding the maximum contaminant level (MCL) of 10 mg/L. This study was conducted to determine whether NO3‐N leaching would be reduced by allowing for a legume N credit for soybean [Glycine max (L.) Merr.], and applying less N fertilizer to corn in a corn‐soybean rotation than would be applied to continuous corn. A rye (Secale cereale L.) winter cover crop was used following soybean. In the spring of each corn year, 140 kg N/ha as NH4NO3 was surface applied to two large, undisturbed monolith lysimeters (8.1 m2 surface area, 2.4 m deep), and 196 kg N/ha was applied to two other lysimeters. Prior to 6 yr of this treatment, there was a 6 yr period during which lysimeters received 224 kg N/ha in the spring of the corn year. The highest NO3‐N concentrations and the most transport occurred during the winter/spring soil moisture recharge period (November through April). Concentrations of NO3‐N in the percolate from all four lysimeters were similar, with a 6‐yr, flow‐weighted average of 9.9 ± 2.5 mg/L. Although reducing N fertilizer inputs in a corn‐soybean rotation to allow for a legume N credit may lower N leaching amounts and concentrations, the NO3‐N MCL may still be exceeded. For a given year, weather can impact percolation and leaching more than the current crop.
Chlorofluorocarbon Dating of Herbicide‐Containing Well Waters in Fresno and Tulare Counties, California
Authors: Spurlock F. , Burow K. , Dubrovsky N. 
Published: July 2010

AbstractSimazine, diuron, and bromacil are the most frequently detected currently registered pesticides in California groundwater. These herbicides have been used for several decades in Fresno and Tulare counties, California; however, previous data are inadequate to determine whether the detections are a result of recent or historical applications (i.e., within the last decade, or 20–30 yr ago). Chlorofluorocarbon (CFC) groundwater age‐dating was used in conjunction with one‐dimensional transport modeling to address this question. The estimated times between herbicide application and subsequent detection in groundwater samples from 18 domestic wells ranged from 3 to 33 yr; the aggregate data indicate that more than half of the detections are associated with applications in the last decade. The data also suggest that changes in groundwater quality arising from modified management practices will probably not be discernible for at least a decade. A secondary objective of this study was to evaluate the contribution of simazine degradates deethylsimazine (DES; 2‐amino‐4‐chloro‐6‐ethylamino‐s‐triazine) and diaminochlorotriazine (DACT; 2,4‐diamino‐6‐chloro‐s‐triazine) to total triazine concentrations (defined here as simazine + DES + DACT) in 30 domestic wells. The N‐dealkylated‐s‐chlorotriazine degradates DES and DACT substantially contribute to total triazine concentrations in Fresno and Tulare County groundwater, composing 24 to 100% of the total triazines, with a median of 82%. If s‐chlorotriazines display a common mode of toxicological action, the prevalence of triazine degradates in water samples found in this and other studies indicate that drinking water standards based on total s‐chlorotriazine concentrations may be most appropriate.
Laboratory Procedures for Characterizing Manure Phosphorus
Authors: Dou Z. , Toth J. D. , Galligan D. T. , Ramberg C. F. , Ferguson J. D. 
Published: July 2010

AbstractPhosphorus runoff from agricultural land contributes to accelerated eutrophication of surface waters. In areas with intensive animal farming, P loss from manured fields may be elevated due to high concentrations of soluble P in manure. We characterized P in dairy and poultry manure for the relative dissolution and fraction distribution using deionized water (H2O), 0.5 M NaHCO3, 0.1 M NaOH, 1.0 M HCl, and 5% trichloroacetic acid (TCA). Two extraction procedures were tested: (i) independent, with dried, ground samples being extracted repeatedly and P measured for each extractant; and (ii) sequential, with each sample being repeatedly extracted by H2O, NaHCO3, NaOH, and HCl, in that order. For the independent procedure, H2O extracted 53 to 64%, NaHCO3 64 to 72%, NaOH 33 to 54%, HCl 90 to 97%, and TCA 84 to 96% of the total P in manure. Sequentially, H2O, NaHCO3, NaOH, and HCl extracted 70, 14, 6, and 5% of the total P in the dairy, and 49, 19, 5, and 25% of the total P in the poultry sample, respectively. Manure P release was not greatly affected by shaking time but decreased rapidly with increasing number of repeated extractions. A large portion of P in manure being extractable by H2O or NaHCO3 suggests weak binding energy of P and hence a high susceptibility for loss to waters when conditions favor runoff. A 1‐h shaking of manure with H2O may provide a quick measure of the relative magnitude of P that is most susceptible. Further investigation relating manure P fractions with P in runoff would help identify management alternatives for reduced P losses.
Phosphate Losses through Field Drains in a Heavy Cultivated Soil
Authors: Addiscott T. M. , Brockie D. , Catt J. A. , Christian D. G. , Harris G. L. , Howse K. R. , Mirza N. A. , Pepper T. J. 
Published: July 2010

AbstractLosses of total and molybdate‐reactive phosphate (MRP) were measured for 4 yr in water flowing from interconnecting mole and pipe drains under 0.24 ha plots of a heavy cracking clay soil. The molybdate‐unreactive phosphate (MUP) obtained by difference appeared from the results to be mainly phosphate carried on suspended soil material. The losses of all three categories of phosphate were closely related to the cumulative drainflow, with the same relations covering three of the four years, designated the synoptic years. Losses were much greater in the other year, probably because phosphate was applied after, rather than before, plowing and to very wet soil. The ceiling to annual total phosphate loss, assuming 500 mm drainage, was 0.4 kg ha−1 in the synoptic years, with 76% of the loss occurring as MUP. It was about 1 kg ha−1 in the high‐loss year, with 88% as MUP, implying that MUP comprised 96% of the extra loss that year. Halving the phosphate application lessened the loss of total phosphate but not conclusively, and the decrease in MRP loss was not significant. Restricting and thereby delaying drainage lessened losses of MUP, probably because suspended material carrying it was allowed to settle. Increasing the spacing between mole channels from 2 m to 4 m increased the losses of MUP but not MRP. This probably happened because to meet a flow pathway connected to a mole channel, rainwater had to travel further horizontally and collected more phosphate‐containing soil material.
Historical Sediment Flux from Three Watersheds into Lake Pepin, Minnesota, USA
Authors: Kelley D. W. , Nater E. A. 
Published: July 2010

AbstractThis contribution presents an assessment of the modern and historic fluxes of sediments exiting the Mississippi, St. Croix, and Minnesota watersheds and entering Lake Pepin, a natural riverine lake on the Upper Mississippi River. A Chemical Mass Balance receptor model and elemental signatures for sediments in Lake Pepin and the rivers draining its three principal catchment areas were used to apportion sediments in the lake to their source watersheds. The apportionment data, estimated trapping efficiency of the lake, and watershed basin areas were used to calculate sediment fluxes and erosion rates for each basin on a decadal basis. The relative apportionment of sediments from the Minnesota River watershed increased since European settlement of the region circa 1830 from 83 to 87% for the upper, 83 to 90% for the middle, and 78 to 87% for the lower reaches of the lake. Sediment loading to the whole lake shows a 12‐fold increase from historic levels in the mass of Minnesota River‐derived sediments. The amount of sediment currently supplied by this river is more than seven times the amount supplied by the headwater‐Mississippi and St. Croix Rivers combined. Sediment contributions from these two combined watersheds have risen sevenfold since settlement. The causes of these increases are attributable to intensive agricultural production, especially within the Minnesota River basin. Watershed alterations have resulted in a decrease in wetlands, riparian zones, and native prairie and an increase in acreage artificially drained by sub‐surface tile lines and surface ditching.
Quantity and Quality of Autumnal Litterfall into a Rehabilitated Agricultural Stream
Authors: Oelbermann Maren , Gordon Andrew M. 
Published: July 2010

AbstractLitterfall from riparian vegetation is a major source of nutrients for stream invertebrates. However, replacement of riparian forests with agricultural crops may result in reduced litter quantity and quality and therefore severely affect stream trophic structure. Litterfall inputs and their associated N flux were measured in 1996 and 1997 at Washington Creek, an agriculturally degraded stream in southern Ontario, Canada. Litterfall varied significantly (p < 0.05) among three treatment areas, with varying tree densities (3.14, 2.43, and 2.17 trees m−2, respectively) and land use. Litterfall was highest (1611 kg ha−1 yr−1) in sections with a wide buffer zone, although it was significantly less (p < 0.05) compared with litterfall in a mature riparian zone (= control, 3238 kg ha−1 yr−1). Leaves represented similar proportions of total litterfall at both the rehabilitated (91.7%) and control (98.2%) site. Litterfall varied significantly (p < 0.05) among trap orientation for both 1996 and 1997 litter collections and was highest in traps oriented south‐west (the predominating wind direction) and perpendicular to the stream. Total N flux varied significantly (p < 0.05) among treatment areas of the rehabilitated site and the mature riparian zone. A higher N flux was found in treatment areas with a wide buffer zone directly adjacent to intensely cropped agricultural fields. This suggests that trees in the riparian zone may be intercepting agricultural runoff and enhancing water quality by converting NO−3‐N runoff to organic forms of N in canopy components. A leaf litter C:N ratio of 32:1 at the rehabilitated site suggests that N may be readily available for stream invertebrates and higher trophic levels.
Soil Carbon Dynamics beneath Switchgrass as Indicated by Stable Isotope Analysis
Authors: Garten C. T. , Wullschleger S. D. 
Published: July 2010

AbstractSurface (0–40 cm) soil organic carbon (SOC) dynamics were studied beneath four switchgrass (Panicum virgatum L.) field trials in the southeastern United States. Soil organic carbon was partitioned into particulate organic matter (POM) and mineral‐associated organic matter (MOM). Most (75–90%) of the SOC at each study site was affiliated with MOM (<0.053 mm). Changes in stable carbon isotope ratios were used to derive carbon inputs to and losses from POM and MOM at each site. Inventories of existing SOC and new C4‐derived SOC beneath switchgrass decreased with increasing soil depth. Approximately 5 yr after establishment, 19 to 31% of the existing SOC inventories beneath switchgrass had been derived from new C4‐carbon inputs. Calculated turnover times of POM and MOM ranged from 2.4 to 4.3 yr and 26 to 40 yr, respectively. The turnover time of SOC in the POM fraction increased with decreasing mean annual temperature. A simple, two‐compartment model was parameterized to predict the potential for soil carbon sequestration under switchgrass. An example calculation with the model indicated a measurable and verifiable recovery of soil carbon (≈12% increase) on degraded lands through one decade of switchgrass production. The potential to sequester carbon through switchgrass cultivation will depend on initial soil carbon inventories, prevailing climate, soil type, and site management.
A Conceptual Model and Indicators for Assessing the Ecological Condition of Agricultural Lands
Authors: Hess George R. , Campbell C. Lee , Fiscus Daniel A. , Hellkamp Anne S. , McQuaid Betty F. , Munster Michael J. , Peck Steven L. , Shafer Steven R. 
Published: July 2010

AbstractAs part of an environmental monitoring and assessment effort, we developed a conceptual model for measuring and assessing the condition and sustainability of agroecosystems. An agroecosystem is a field, pasture, or orchard and the associated border areas. We focused on ecological sustainability and defined the goals for agroecosystems in terms of the values people place on them. The purpose of an agroecosystem is to produce food and fiber. Other desired outcomes can be considered as goals for the larger landscape and the rest of the world, and they sometimes function as constraints on production. Condition is defined by agroecosystem productivity and the degree to which farmers use management and stewardship practices that conserve and protect valued natural resources in the landscape and the rest of the world. An agroecosystem in good condition is productive and is managed to conserve valued resources. Sustainability is the maintenance of good condition over time. We developed indicators that link system condition and sustainability to societal values and goals. These indicators measure productivity, management practices that promote sustainability at the agroecosystem scale, and management practices that promote sustainability at landscape and global scales. Our initial efforts focused on annually harvested herbaceous crops; however, the concepts we used can be adapted to other plant and livestock systems. Our conceptual approach may be used to evaluate the effectiveness of several major programs now being implemented, including the USDA's Environmental Quality Incentive and Conservation Reserve Programs.
Greenhouse Gas Emission from Stored Livestock Slurry
Authors: Sommer Sven G. , Petersen Søren O. , Søgaard Henning T. 
Published: July 2010

AbstractAnimal manure contributes about 40% of the total methane (CH4) and 20% of the total nitrous oxide (N2O) emissions in Denmark. We measured the CH4 and N2O emissions from stored cattle slurry and fermented slurry during fall 1996 and summer 1997 and evaluated the effect of surface covers consisting of straw, floating leca pebbles, or a natural surface crust on the patterns of these emissions. No emission of N2O was measured during periods with more rain than evaporation from the slurry stores and no emission was measured from uncovered slurry, irrespective of climatic conditions. During the summer storage with drying conditions, N2O emissions of up to 25 mg N m−2 h−1 were recorded from slurry with surface covers. Total N2O emission was highest from digested slurry. The emission of CH4 from stored fermented slurry and cattle slurry varied between <0.01 and 1.4 or 0.7 g CH4—C m−3 h−1, respectively. The log‐transformed emissions were linearly related to the inverse temperature. Emission of CH4 was reduced, on average, by 38% with surface covers. The reduction was probably due to CH4 oxidation in the surface covers or in the interface between the cover and liquid in the store. Fermentation did not reduce CH4 emissions during storage of the slurry.
Assessing the Origin of Sulfate Deposition at the Hubbard Brook Experimental Forest
Authors: Alewell C. , Mitchell M. J. , Likens G. E. , Krouse R. 
Published: July 2010

AbstractThe geographical and chemical origin of SO2−4 deposition has become a concern, because anthropogenic S emissions have influenced the biogeochemistry of forested ecosystems and surface waters. Our aim was to evaluate the origin of SO2−4 in bulk precipitation at the Hubbard Brook Experimental Forest (HBEF), New Hampshire. We analyzed 26 years of archived bulk precipitation samples for sulfur stable isotopes. We compared the δ34S values with anthropogenic SO2 emissions, the relative contribution of sea salt aerosols (as the SO−4/Na+ ratio in precipitation), and temperature and solar radiation effects on the long‐term patterns of δ34S values. The long‐term pattern of δ34S values in bulk precipitation could be explained partly by the relative contribution of marine SO2−4 or solar radiation but not by temperature variation or anthropogenic SO2 emissions. The high variability of the δ34S values of various fossil fuels makes it difficult to use stable S isotopes for identifying whether changing fossil fuel use is affecting the δ34S values in bulk precipitation. The seasonal pattern of δ34S values in bulk precipitation (significantly higher values in the winter than the summer) may be explained by the temperature dependence of the isotopic shift during SO2−4 formation in the atmosphere. A greater relative contribution of marine SO2−4 during the winter also may have contributed to the higher δ34S values in the winter. Previous investigations may have overestimated the role of biogenic emissions in affecting the δ34S pattern.
Sewage Sludge as an Amendment for Calcareous Bauxite Mine Spoils Reclamation
Authors: Brofas G. , Michopoulos P. , Alifragis D. 
Published: July 2010

AbstractDried aerobically digested sewage sludge applied at seven rates (0, 10, 20, 40, 60, 80, and 120 Mg ha−1) in a field experiment on calcareous bauxite mine spoils significantly increased the available water capacity, concentrations of organic matter, total N, extractable P (Olsen), exchangeable Mg2+, and diethylenetriaminepentaacetic acid (DTPA)‐extractable Cu, Mn, Zn, and Pb of mine spoils. Total N and extractable P concentrations decreased with time after sludge application. The DTPA‐extractable Cu concentration was high 4 yr after application at sludge rates of 80 and 120 Mg ha−1. Extractable Cu and Zn concentrations correlated significantly and positively with Cu and Zn concentrations in burnet (Sanguisorba minor subsp. minor) and fiddleneck (Phacelia tanacetifolia Benth) tissue. Sludge application depressed plant Mn uptake. Plant biomass, plant density, and foliar cover significantly increased with treatment rates in the first and fourth growing seasons but decreased with time. Fiddleneck and burnet were the species favored by the high rates of sludge application.
Predicting Subsurface Drainage, Corn Yield, and Nitrate Nitrogen Losses with DRAINMOD‐N
Authors: Zhao S. L. , Gupta S. C. , Huggins D. R. , Moncrief J. F. 
Published: July 2010

AbstractNitrate N from artificially drained soils of the upper Midwest USA is finding its way to the Mississippi River and then to the Gulf of Mexico. There is some concern that this nitrate N is causing hypoxia in the Gulf of Mexico. The DRAINMOD‐N model was used to evaluate the long‐term effect of N application rate and drain spacing on corn (Zea mays L.) yield and nitrate N losses. Prior to evaluation, the model was calibrated and then validated against long‐term field data from southwestern Minnesota. A 24‐yr simulation showed that climate plays a major role in determining drainage, yield, and nitrate N losses from a moderately well‐drained Normania clay loam (fine‐loamy, mixed, mesic Aquic Hapludoll) soil under continuous corn. April to August rainfall accounted for 82% of the variation in drainage and 66% of the variation in nitrate N losses during the growing season. Corn yield increased significantly when drain spacing was changed from 56 to 28 m but there was much less increase when changing from 28 to 14 m. During the growing season, drain spacing had little effect on nitrate N losses from this soil. Cost‐benefit analysis showed that a 28 m drain spacing was a good design criterion for this soil. For a given drain spacing, an increase in N application rate significantly increased nitrate N losses through drainage. We conclude that efforts to reduce drainage‐associated nitrate N losses from soils with perched water table conditions in the upper Midwest USA should concentrate on identifying N management strategies that increase N use efficiency.
Molybdenum Uptake by Forage Crops Grown on Sewage Sludge‐Amended Soils in the Field and Greenhouse
Authors: McBride M. B. , Richards B. K. , Steenhuis T. , Spiers G. 
Published: July 2010

AbstractMolybdenum (Mo) is a plant‐available element in soils that can adversely affect the health of farm animals. There is a need for more information on its uptake into forage crops from waste materials, such as sewage sludge, applied to agricultural land. Field and greenhouse experiments with several crops grown on long‐term sewage sludge‐amended soils as well as soils recently amended with dewatered (DW) and alkaline‐stabilized (ALK) sludges indicated that Mo supplied from sludge is readily taken up by legumes in particular. Excessive uptake into red clover (Trifolium pratense L.) (>30 mg/kg) was seen in a soil that had been heavily amended with sewage sludge 20 yr earlier, where the soil contained about 3 mg Mo/kg soil, three times the background soil concentration. The greenhouse and field studies indicated that Mo can have a long residual availability in sludge‐amended soils. The effect of sludge application was to decrease Cu to Mo ratios in legume forages, canola (Brassica napus var. napus) and soybeans [Glycine max (L.) Merr.] below the recommended limit of 2:1 for ruminant diets, a consequence of high bioavailability of Mo and low uptake of Cu added in sludge. Molybdenum uptake coefficients (UCs) for ALK sludge were higher than for DW sludge, presumably due to the greater solubility of Mo measured in the more alkaline sludges and soils. Based on these UCs, it is tentatively recommended that cumulative Mo loadings on forages grown on nonacid soils should not exceed 1.0 kg/ha from ALK sludge or 4.0 kg/ha from DW sludge.
Desorption of Polycyclic Aromatic Hydrocarbons from Soil in the Presence of Dissolved Organic Matter: Effect of Solution Composition and Aging
Authors: Kögel‐Knabner Ingrid , Totsche Kai U. , Raber Bernd 
Published: July 2010

AbstractThe effect of dissolved organic matter (DOM) on the desorption of polycyclic aromatic hydrocarbons (PAHs) from soil was studied with 14C‐benzo[a]pyrene and 14C‐pyrene in different soil‐aqueous solution systems and after prolonged periods of aging (110 and 216 d). The desorption of 14C‐benzo[a]pyrene and 14C‐pyrene was strongly affected by the composition and properties of the aqueous phase. Desorption linearly increased with increasing DOM concentrations. Distribution coefficients (log Koc′) for the desorption of 14C‐labeled PAHs were about 3.5 (pyrene) and 25 (benzo[a]pyrene) times lower in the presence of DOM. The enhancement of PAH desorption between various types of DOM is controlled by the molecular weight distribution of DOM. Dissolved organic matter with a high proportion of high molecular weight components (>14 000 dalton) has a high affinity for PAHs and thus is more effective in desorbing PAHs from soil. In addition, the desorption of PAHs from soil is controlled by the time elapsed since contamination. In the first 36 d following contamination with 14C‐benzo[a]pyrene, a decrease of the PAH concentration that could be desorbed in the solution phase was observed. The desorbable fraction did not show any further changes for up to 183 d after contamination, suggesting a fraction of PAH that is not or very slowly desorbing from soil. The major proportion (>98%) of the desorbable PAH‐fraction is apparently bound at sites that show a rate‐limited release of PAHs. This is corroborated by the model discrimination conducted with three different models, which favors a two‐site equilibrium‐nonequilibrium model.