bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Soil Phosphorus Levels and Phosphorus Leaching from Agricultural Land in the Netherlands
Authors: Schoumans O. F. , Groenendijk P.
Published: July 2010

The contribution of nonpoint‐source pollution of P leaching and P runoff from agricultural soils is very important, especially in those areas with intensive livestock production systems. Prediction of the impacts of fertilization reduction measures on P loads from agricultural soils to surface water requires a sound description of the accumulation of P. In this article an overview is given of the Dutch approach. The presented methodology has been developed for noncalcareous sandy soils in flat areas where P loss by subsurface runoff is the dominating pathway. Based on the kinetics of P sorption and desorption of these soil types, P accumulation in soils, and inorganic P concentrations in soil solution can be modeled. Furthermore, methods have been deduced to translate the description of soil chemical P processes into commonly used soil P tests. As a result of this interaction, soil P tests can be used as an initial approach to estimate the potential risk of P leaching and runoff from agricultural soils in noncalcareous sandy areas. The description of the kinetics of inorganic P reactions and the modeling of soil P tests have been implemented in the ANIMO model in addition to an organic P cycle that is related to organic C and N dynamics. With this model, the fixation and immobilization of P by soll components can also be assessed. As a result of annual losses by fixation, immobilization, and subsurface runoff/leaching, changes in soil P test values with time can be estimated.
Phosphorus Research Strategies to Meet Agricultural and Environmental Challenges of the 21st Century
Authors: Sharpley Andrew , Tunney Hubert
Published: July 2010

The accumulation, management, and transfer of P in intensive farming systems has increased P export from agricultural watersheds and accelerated eutrophication of surface waters. Even though much research on P has been done in the last 20 years, there are still too few answers to the many questions now being asked regarding agricultural production and environmental quality. To address these concerns, four areas of research are suggested: (i) Soil P testing for environmental risk assessment—What losses are acceptable and can these losses be determined by plot‐scale or watershed‐scale studies? Threshold P levels in soil and water should be established in combination with an assessment of site vulnerability to P loss. (ii) Pathways of P transport—An analysis of the relative importance of different flow pathways is needed at a watershed scale. (iii) Best Management Practice (BMP) development and implementation—Overall, BMPs must attempt to bring P inputs and outputs into closer balance and should be targeted first to critical source areas within a watershed. Alternative management recommendations, uses, and market demand for manures must be developed. (iv) Strategic initiatives to manage P—To initiate lasting changes, research should focus on consumer‐supported programs that encourage farmer performance and stewardship to achieve agreed‐upon environmental goals.
Nitrogen Fertilizer and Herbicide Transport from Tile Drained Fields
Authors: Gentry Lowell E. , David Mark B. , Smith‐Starks Karen M. , Kovacic David A.
Published: July 2010

Offsite transport of N fertilizers and pesticides through subterranean drainage pipes (tiles) has been linked to surface water contamination in the U.S. Corn Belt. This study was conducted from water years 1995 to 1997 to evaluate N export from two tile systems (Tiles A and B) in adjacent fields [in seed corn‐soybean rotation (Zea mays L.‐Glycine max (L.) Merr.)] in response to timing and form of N application. In addition, during the 1997 water year, concentrations of two herbicides were determined on grab samples to relate tile herbicide losses with field application rates. During the 1995 and 1996 water years, Tile A exported approximately 20% more N per unit area than Tile B; however, during the 1997 water year, Tile A exported nearly 70% more N. This result was partly caused by the leaching of 142 kg of NH+4‐N following a winter application of (NH4)2SO4 fertilizer in the drainage area of Tile A. The fertilizer was applied on top of 10 cm of snow, and within 4 d, a series of afternoon melting events began. We hypothesize that increased tile flow rates were caused by rapid infiltration of melt water through partially frozen soil (Drummer silty clay loam, fine‐silty, mixed mesic Typic Haplaquolls) that allowed the NH+4 ion to bypass the soil matrix (conc. reached 278 mg NH+4‐N L−1). The incidence of elevated concentrations of N fertilizer and herbicides in tiles during high flow events following agrichemical application indicated rapid water transport via preferential flow paths, thereby limiting the contact of these solutes with the soil.
Salmonella spp. and Fecal Coliform Loads in Coastal Waters from a Point vs. Nonpoint Source of Pollution
Authors: Baudart J. , Grabulos J. , Barusseau J.‐P. , Lebaron P.
Published: July 2010

Coastal areas are often contaminated by the dissemination of pathogenic bacteria from terrestrial inputs. In this study, we compared fecal coliforms (FC) and Salmonella spp. loads from a coastal Mediterranean river and from the submarine outfall of a coastal wastewater treatment station. A stratified sampling strategy was used to analyze storm events. Bacterial fluxes were estimated during a 16‐mo period. Salmonella spp. loads from the river were high during storm events, and the annual loads were higher than those estimated from the coastal outfall. Bacterial loads from the river represented 3.0 × 1016 FC yr−1 and 6.9 × 1012 Salmonella yr−1, with at least 95% occurring during high waterflow (21% of the year). Those from the submarine outfall represented 4.3 × 1016 FC yr−1 and 4.7 × 1010 Salmonella yr−1, with a regular temporal discharge. Bacterial loads from the river were associated with small clay particles (<2 µm), which originate from different reservoirs. These particles‐sediment‐trapped bacteria accumulated in the river‐bed during the lowest water levels in the downstream part of the river and were resuspended during storm events. The quantitative relationship between both bacterial parameters vary depending on the source point of contamination. Salmonella spp. loads from the river are of great sanitary concern since high loads were recorded in summer (bathing activities) and autumn (oyster production and consumption). Our results should help water quality managers to define priorities to improve the bacterial quality of river discharges.
Irrigation‐ and Nitrogen‐Management Impacts on Nitrate Leaching under Potato
Authors: Waddell J. T. , Gupta S. C. , Moncrief J. F. , Rosen C. J. , Steele D. D.
Published: July 2010

As potato (Solanum tuberosum L.) production increases in the North‐Central Region of the USA, so does the potential for deep seepage of nitrogenous compounds into the ground water. The objectives of this 2‐yr study were to determine how different irrigation schemes (sprinkler and drip), irrigation triggers (70 and 40% of the available soil water [AW] remaining), drip placement (at the soil surface or buried at 25‐cm depth), and various N sources (urea, sulfur‐coated urea [SCU], and turkey [Meleagris gallopavo] manure) and timings (three‐ vs. five‐N splits) affect percolation and NO3 leaching. As expected, water percolation was generally higher from the sprinkler‐irrigation than from the drip‐irrigation treatments. Within the sprinkler irrigation, percolation was higher when irrigated at 70% than at 40% of AW remaining. Small but frequent irrigation in drip treatments helped reduce water percolation. Within irrigation treatments, 70% AW had the most N leaching, followed by 40% AW and the drip, the last two treatments being about the same. The trend in N leaching among fertilizer treatments was similar for various irrigation methods. Splitting N applications five times vs. three times reduced N leaching from unforeseen rains. Sulfur‐coated urea reduced N leaching, whereas turkey manure‐amended treatments showed no significant difference in N leaching compared with the urea‐N treatment. In conclusion, alternatives such as 40% deficit irrigation, five‐N application splits, drip irrigation, S‐coated urea, and turkey manure not only reduce N leaching but also have a minimal impact on potato tuber yield and tuber quality.
Laboratory Estimates of Trace Gas Emissions following Surface Application and Injection of Cattle Slurry
Authors: Flessa H. , Beese F.
Published: July 2010

Applying cattle slurry to soil may induce emissions of the greenhouse gases N2O and CH4. Our objective was to determine the effects of different application techniques (surface application and slit injection) of cattle (Bostaurus) slurry on the decomposition of slurry organic matter and the emissions of N2O and CH2. The effects of slurry application (43.6 m3 ha−1) were studied for 9 wk under controlled laboratory conditions using a soil microcosm system with automated monitoring of the CO2, N2O, and CH4 fluxes. The soil used was a silty loam (Ap horizon of a cambisol) with a constant water‐filled pore space of 67% during the experiment. About 38% of the organic matter applied with the slurry was decomposed within 9 wk. Production of CO2 was not affected by the application technique. Emissions of N2O and CH4 from the injected slurry were significantly higher than from the surface‐applied slurry, probably because of restricted aeration at the injected‐slurry treatment. Total N2O‐N emissions were 0.2% (surface application) and 3.3% (slit injection) of the slurry N added. Methane emission occurred only during the first few days following application. The total net flux of CH4‐C for 2 wk was −12 g ha−1 for the control (CH4 uptake), 2 g ha−1 for the surface‐applied slurry, and 39 g ha−1 for the injected slurry. Slurry injection, which is recommended to reduce NH3 volatilization, appears to increase emissions of the greenhouse gases N2O and CH4 from the fertilized fields.
Nitrous Oxide and Methane Emissions following Application of Animal Manures to Grassland
Authors: Chadwick D. R. , Pain B. F. , Brookman S. K. E.
Published: July 2010

Nitrous oxide (N2O) and methane (CH4) emissions were measured from grassland following manure applications at three times of the year. Pig (Sus scrofa) slurry and dairy cow (Bos taurus) slurry were applied in April, at equal rates of ammoniacal‐N (NH+4‐N), and in July, at equal volumetric rates (50 m3 ha−1). I n October, five manure types were applied to grassland plots at typical application rates: pig slurry, dilute dairy cow effluent, pig farm yard manure (FYM), beef FYM and layer manure. Emissions were measured for 20, 22, and 24 d, respectively. In April, greater cumulative emissions of N2O‐N were measured following application of dairy cow slurry (1.51 kg ha−1) than pig slurry (0.77 kg ha−1). Cumulative CH4 emissions following application in April were significantly greater from the dairy cow slurry treatment (0.58 kg ha−1) than the pig slurry treatment (0.13 kg ha−1) (P < 0.05). In July, significantly greater N2O‐N emissions resulted from pig slurry‐treated plots (0.57 kg ha−1) than dairy cow slurry‐treated plots (0.34 kg ha−1). Cumulative net CH4 emissions were very low following July applications (<10 g ha−1). In October, the lowest N2O‐N emission resulted from application of dilute dairy effluent, 0.15 kg ha−1, with the greatest net emission from the application of pig slurry, 0.74 kg ha−1. Methane emissions were greatest from the plots that received pig FYM, resulting in a mean cumulative net emission of 2.39 kg ha−1.
Rye Cover Crop and Nitrogen Fertilization Effects on Nitrate Leaching in Inbred Maize Fields
Authors: Rasse Daniel P. , Ritchie Joe T. , Peterson W. Richard , Wei Jun , Smucker Alvin J. M.
Published: July 2010

Nitrate leaching from maize (Zea mays L.) fields fertilized in excess of plant requirements continue to threaten water quality even though many agronomists have recommended reducing N fertilization rates to contain this environmental risk. Inbred maize has lower N uptake than conventional hybrid maize; therefore, inbred maize production exposes soils to even greater ground water pollution risks by nitrates. A 3‐yr field experiment was conducted on sandy loam soils in southwestern Michigan to investigate the combined effects of N fertilization rates and rye (Secale cereale L.) cover crops on NO3 leaching in inbred maize fields. Inbred maize was fertilized at 0, 101, and 202 kg N ha−1. Annual NO3 leaching losses were 7 kg N ha−1 higher in fields fertilized at 101 kg N ha−1 than in nonfertilized controls. Annual NO3 leaching losses to ground water between May 1995 and April 1998 from lysimeters fertilized at 202 kg N ha−1 averaged 88 kg NO3‐N ha−1. Rye interseeded with inbred maize fertilized at 202 kg N ha−1 sequestered from 46 to 56 kg ha−1 of excess fertilizer N. Rye scavenged little residual fertilizer N in plots fertilized at 101 kg N ha−1. Well established rye cover crops in 1996 reduced NO3 leaching by as much as 65 kg N ha−1 when the previous crop was fertilized with 202 kg N ha−1. Therefore, rye cover crops sequestered substantial amounts of soil NO3 in heavily fertilized inbred maize fields.
Bentonite and Humic Acid as Modifying Agents in Controlled Release Formulations of Diuron and Atrazine
Authors: Fernández‐Pérez M. , González‐Pradas E. , Villafranca‐Sánchez M. , Flores‐Céspedes F. , Ureña‐Amate M. D.
Published: July 2010

The herbicides diuron [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea] and atrazine [6‐chloro‐N2‐ethyl‐N4‐isopropyl‐1,3,5‐triazine‐2,4‐diamine] were incorporated in alginate‐based granules to obtain controlled release (CR) properties. The basic formulation [sodium alginate (14.0 g kg−1)‐herbicide(6.0 g kg−1)‐water] was modified by addition of sorbents. The effect on (Huron and atrazine release rate, caused by incorporation of natural bentonite and humic acid in the alginate formulation, was studied by immersion of the granules in water under static conditions. The release of the active ingredient from alginate‐based CR granules in water was affected by the addition of natural bentonite, and to a greater extent, by the addition of the humic acid. The water uptake, permeability, and the time taken for 50% of active ingredient to be released into water, T50, were calculated for the comparison of the preparations. Addition of both bentonite and humic acid samples to the basic alginate‐based formulation produced the higher T50 values (43.11 and 50.49 d for diuron and atrazine formulations, respectively), indicating a slower release of herbicide. Based on parameters of an empirical equation used to fit the herbicide release data, it appears that the release of diuron and atrazine from the various formulations into water is controlled by a diffusion mechanism. Sorption capacity of the sorbent and the permeability of the formulations (ranging from 3.77 to 20.83 mg d−1 mm−1) were the most influential factors affecting herbicide release.
Relationship of Soil Organic Matter Characteristics to Organic Contaminant Sequestration and Bioavailability
Authors: Lueking Angela D. , Huang Weilin , Soderstrom‐Schwarz Sara , Kim Minsun , Weber Walter J.
Published: July 2010

Sorption and desorption equilibria of phenanthrene with respect to three different types of geosorbents were measured, as were the rates of desorption and biological mineralization of this representative hydrophobic organic contaminant. The chemical nature of the organic matter associated with each geosorbent was characterized using solid state 13C‐NMR spectrometry. The results of these studies reveal that both the desorption behavior and the microbial bioavailability of the sorbed contaminant are influenced by the physicochemical character of the organic matter. The more reduced and condensed the organic matter, the greater the extent of sorption‐desorption hysteresis, the slower the desorption rate, and the less readily bioavailable the sorbed contaminant. These observations are consistent with projections predicated on a dual reactive domain model introduced earlier to describe the sorptive reactivities of different types of soil/sediment organic matter with hydrophobic organic contaminants.
Nitrogen Mineralization of Lime‐Stabilized Fishwaste in Acid Soils and its Effect on Plant Growth
Authors: Kuo S. , Bristow P. R. , Jellum E. J. , Okiro M.
Published: July 2010

Fishwaste is often disposed of in landfills or the ocean, adversely affecting water quality. With its high protein content, fishwaste could instead be used as a N source for crop production. The viability of a lime‐stabilized fishwaste (LSF) product as a N source was tested by determining its effects on net N mineralization, growth of bacteria, and the growth of a variety of plant species in two acidic soils. Net N mineralization and viable bacteria number were significantly increased (P < 0.001) by the addition of LSF. At the highest rate of 30 g LSF kg−1 soil, high NH4‐N accumulation was extended to several weeks and a longer lag period before bacteria growth occurred. At such a high rate, nitrification, but not the activities of proteolytic enzymes, was severely impaired. The considerably high inactivation rate for the bacteria following the exhaustion of the available energy in the protein in the Sultan soil [half life = 4.5 ± 0.5 d (SD)] may explain why the Sultan soil had a comparatively higher net N mineralization rate than the Puyallup soil [half life = 14.7 ± 3.5 d (SD)]. At 6 g LSF kg−1 soil in a greenhouse trial, the N availability to a variety of crops was generally increased. Unless a soil is extremely acidic, using high rates of LSF can lead to undesirable soil conditions (high pH and NH4‐N accumulation) that interfere with plant growth.
Characterization and Extractability of Copper, Manganese, and Zinc in Swine Manure Composts
Authors: Hsu Jenn‐Hung , Lo Shang‐Lien
Published: July 2010

Swine (Sus domesticus) manure was comprehensively characterized with respect to Cu, Mn, and Zn in feed additives. This research was conducted to study the leachability and identify factors influencing the leachability of these elements from separated swine manure (SSM) composts to assess its environmental hazard. Several chemical properties were determined to assess the degree of maturity of eight SSM composts. A series of extraction schemes were used to determine base‐extractable metals and their distribution on humic substance fractions (humic acid, HA; fulvic acid, FA; and nonhumic fraction, NHF), chemical fractionation, synthetic acid rainwater (SAR) solubility, and extractability at various pH levels of metals in composts. We evaluated the influence of dissolved organic carbon from compost on the extractability of these metals. The SSM composts were enriched with Cu (154–1380 mg kg−1), Mn (239–976 mg kg−1), and Zn (372–2840 mg kg−1). The SAR and neutral‐pH extractable fractions of Cu, Mn, Zn, and organic C were generally low (<10% of their total content). Copper leachability in Sample F2 compost, however, was high (20%), resulting from immaturity and associated substantial dissolution of organic C (18%). High extractability (86%) of Cu from humic substances (HS) extraction and at high pH levels (>8) resulted from dissolution of organic matter. Conversely, the extractability of Mn and Zn at alkaline pH levels was low. The major portions of Cu, Mn, and Zn were found in the organic, oxide, and carbonate fractions, respectively, regardless of their content in these composts. The results of this study show that Cu in SSM compost is primarily bound to organics.
Removal of Perchlorate in Ground Water with a Flow‐Through Bioreactor
Authors: Giblin Tara , Herman David , Deshusses Marc A. , Frankenberger William T.
Published: July 2010

The bacterium, perc1ace, has been shown to reduce perchlorate to less than the detection limit of 0.004 mg L−1 when grown on acetate under anaerobic conditions. In batch studies, the presence of nitrate does not significantly hinder the reduction of perchlorate. The ability of perclace to remove nitrate and perchlorate from ground water in a flow‐through system is described in this study. Celite‐packed columns of 300 ml were used to demonstrate the removal of perchlorate from ground water. At a flow rate of 1 ml min−1, perchlorate was removed from 0.738 mg L−1 to less than detectable levels and when the flow rate was 2 ml min−1 92 to 95% of the perchlorate was removed. Analysis of bacterial biomass at the completion of the study revealed that most of the bacterial growth was concentrated in the inlet area of the column. A circulating pump was added, with the idea that passing the ground water multiple times through the bacterially active zone might increase the efficiency of the column. In this experiment, perchlorate in ground water was reduced from 0.550 mg L−1 to nondetectable levels at a flow rate of 1 ml min−1. When the flow rate was increased to 2 ml min−1, 98% of perchlorate was removed and when the flow rate was 3 ml min −1 95% of perchlorate was removed. Rapid removal of perchlorate by perc1ace immobilized in a bioreactor may provide an efficient, cost‐effective technology for ground water remediation.
Phenanthrene‐Degrader Community Dynamics in Rhizosphere Soil from a Common Annual Grass
Authors: Miya Ryan K. , Firestone Mary K.
Published: July 2010

Enhanced rates of phenanthrene biodegradation were observed in rhizosphere soils (17.2 and 15.5 mg/kg/d for initial and re‐spiked additions, respectively) planted with slender oat (A vena barbata Pott ex Link) compared with unplanted bulk soil controls (12.4 and 10.7 mg/kg/d). Soil microbial populations were characterized using a modified most probable number (MPN) method to determine quantitative shifts in heterotrophic and phenanthrene degrader communities while principal component analysis (PCA) of fatty acid methyl ester (FAME) data from isolated phenanthrene degraders was used to identify qualitative differences and degrader community diversity. The average heterotrophic bacterial population over time was about three times larger in rhizosphere soil than in bulk soil while phenanthrene degrading populations increased by as much as an order of magnitude between 24 and 28 days after planting (DAP). Thus, phenanthrene degraders were selectively enriched in rhizosphere soil compared with bulk soil. The greatest selection for degraders occurred during the later stages of plant development from 24 to 32 DAP. A PCA plot of the FAME data from phenanthrene degrader isolates indicated that the rhizosphere degraders were less diverse than bulk soil degraders. These results give us some insight into the mechanisms responsible for enhanced biodegradation and selective degrader enrichment in rhizosphere soils.
Organic Matter Transformations During the Weathering Process of Spent Mushroom Substrate
Authors: Chefetz Benny , van Heemst Jasper D. H. , Chen Yona , Romaine C. Peter , Chorover Jon , Rosario Rex , Mingxin Guo , Hatcher Patrick G.
Published: July 2010

The weathering process of spent mushroom substrate (SMS) was studied to better understand the chemical properties and transformations of organic matter (OM) during the process. The SMS was piled (20 m by 6 m row of 1.5 m height) in an open field and weathered during 15 mo. Chemical properties of the OM collected from the top and bottom parts of the weathering pile were studied using 13C‐nuclear magnetic resonance (NMR), tetramethylammonium hydroxide (TMAH) thermochemolysis‐gas chromatograph/mass spectrometry (GC/MS), and pyrolysis‐gas chromatograph/mass spectrometry (Py‐GC/MS). The 13C‐NMR data suggested that weathered SMS from the top part of the pile degraded rapidly: the relative level of polysaccharides decreased by 33% while the level of aromatic C increased by 21% during the process. The TMAH thermochemolysis chromatogram exhibited peaks of methylated derivatives of phenyl, guaiacyl and syringyl structures as well as some fatty acid methyl esters. Lignin‐derived products from TMAH thermochemolysis indicate that preferential degradation of syringyl units and oxidation of Cα‐Cβ bonds occurred in the SMS from the top part of the pile. In contrast, no major changes in lignin‐derived structures were observed in the weathered SMS from the bottom part of the pile. The 13C‐NMR, Py‐GC/MS and TMAH thermochemolysis‐GC/MS analyses indicated that the SMS decomposed rapidly at the top part of the weathering pile, whereas decomposition at the bottom of the pile was significantly slower, probably due to lack of oxygen. These analyses were shown to be useful techniques for the characterization of degradation processes in SMS. Therefore, their application to studies on OM transformation and humification processes is highly recommended.
Effect of Soil Conditions on the Degradation of Cloransulam‐Methyl
Authors: Cupples Alison M. , Sims Gerald K. , Hultgren Ryan P. , Hart Steven E.
Published: July 2010

Herbicide efficacy and environmental fate are often controlled by soil conditions. Aerobic soil laboratory studies were undertaken to determine the degradation of the herbicide cloransulam‐methyl [N‐(2‐carbomethoxy‐6‐chloro‐phenyl)‐5‐ethoxy‐7‐fluoro[1,2,4]triazolo [1,5‐c]pyrimidine‐2‐sulfonamide] for a range of soil factors. Treatments included soil temperature (5, 15, 25, 40, and 50°C), moisture (20, 40, and 60% water filled pore space), and soil type. The soils under study were a Drummer silty clay loam (fine‐silty, mixed, super‐active, mesic Typic Endoaquolls) and a Cisne silt loam (fine, smectitic, mesic Vertic Albaqualfs). Variability in molecular degradation was investigated using two radiolabeled forms ([Phenyl‐UL‐14C] and [Pyrimidine‐7,9‐14C]). Dissipation of parent compound in soil solution and sorbed phases, formation of radiolabeled metabolites, 14C mineralization, total microbial respiration, and bound residue formation were measured for up to 120 d. Dissipation of parent and formation of bound residues in Drummer soil increased with greater temperatures. The influence of temperature on 14C mineralization, however, was dependent on position of radiolabel, suggesting that distinct groups of microorganisms degrade different parts of the molecule at higher temperatures. Only 14C mineralization was influenced by moisture, with response depending on soil type. Increasing moisture resulted in more 14C mineralization in Drummer, but not Cisne soil, which was attributed to increased microbial access to pesticide at greater moisture contents in Drummer soil. Reduced availability, suggested by greater sorption in Drummer soil, may explain persistence of parent in this soil. Bound residues were more extensive and exhibited greater dependence on biological activity in Cisne soil, owing to enhanced dissipation of parent compound in this soil.
Assessment of the Condition of Agricultural Lands in Six Mid‐Atlantic States
Authors: Hellkamp Anne S. , Bay Jeff M. , Campbell C. Lee , Easterling Karen N. , Fiscus Daniel A. , Hess George R. , McQuaid Betty F. , Munster Michael J. , Olson Gail L. , Peck Steven L. , Shafer Steven R. , Sidik Kurex , Tooley Mark B.
Published: July 2010

Indicators of the condition and sustainability of agricultural lands covering 5.5 million ha in six mid‐Atlantic states were measured in 1994 and 1995. The primary objective was to collect baseline information against which future data from the region can be compared. Soil samples and questionnaire data were collected from a random sample of 293 sites. Indicators addressed productivity, management at the agroecosystem scale, and management for the landscape scale on annual crop land. Crop yields were almost 30% higher than those of the 1980s, with a mean observed to expected yield index of 1.27. The mean soil quality index showed moderate quality for supporting plant growth. Non‐tilled sites, which were mostly hay, had greater microbial biomass than tilled sites. Just over half of the annual crop land was covered by rotation plans; hay fields accounted for most of the land where one crop was grown continuously. Hay showed a lower use of applied nitrogen than seed crops. Integrated pest management was practiced on less than 20% of annual crop land. Twenty‐seven different annual crops were grown in the region, with hay (all types) the dominant crop. Less than 20% of the land where pesticides were applied had high to moderately high potential for pesticides leaching into ground water. This information provides a baseline for long‐term monitoring of agricultural lands in the region.
17 β‐Estradiol as an Indicator of Animal Waste Contamination in Mantled Karst Aquifers
Authors: Peterson E. W. , Davis R. K. , Orndorff H. A.
Published: July 2010

The poultry and cattle industries comprise a large segment of the agricultural economy in the mantled karst area of northwest Arkansas. The associated risks of nutrient and bacterial contamination to karst aquifers by poultry litter have been well documented. However, only recently have the risks associated with hormones, specifically 17 β‐estradiol (E2), been addressed. During a winter recharge event, five springs in northwest Arkansas were sampled and the waters were analyzed for E2, fecal coliform, and Escherichia coli. Analyses of the waters from five springs representing three different water‐bearing formations revealed that E2 is present in the waters. Concentrations of E2 ranged from 6 to 66 ng/L. The observed E2 concentration trends imitated the changes in stage over the recharge event. The E2 concentration trends were similar to the concentration trends of both fecal coliform and E. coli at all five springs, indicating that the three components move in the mantled karst system similarly.
Regional‐Scale Leaching Assessments for Tenerife: Effect of Data Uncertainties
Authors: Diaz‐Diaz Ricardo , Loague Keith
Published: July 2010

This paper reports assessments of nonpoint‐source (NPS) ground water vulnerability due to pesticide leaching for the Canary Island of Tenerife. Index‐based estimates of contamination potential were made for the pesticides Carbofuran and Ethoprophos using the attenuation and retardation factors (AF and RF). The major objective this effort was to characterize the data‐related uncertainties, using first‐order uncertainty analysis, that are associated with the new pesticide leaching estimates for Tenerife. The crop, recharge, and soils data for Tenerife were overlaid in this regional‐scale study using a geographic information system approach. The strategy was to identify the effect of supplemental information in reducing uncertainties in the island‐wide vulnerability estimates. Data improvements were estimated as reductions in the AF and RF input parameter uncertainties. The greatest improvements in the Tenerife vulnerability estimates were found for reductions in the chemical data uncertainties. The new vulnerability assessments for Tenerife will be useful for future agrochemical regulation decisions and for targeting critical areas that may require remediation.
Transport of Mercury from a Cultivated Field during Snowmelt
Authors: Balogh S. J. , Meyer M. L. , Hansen N. C. , Moncrief J. F. , Gupta S. C.
Published: July 2010

Total mercury (THg) was determined in snow, overland snowmelt runoff, and soil from a small cultivated catchment. Total mercury concentrations in snow were low [mean concentration = 1.04 ng/L (liquid basis); n = 9; CV = 23%], while THg concentrations in snowmelt runoff were much higher, ranging from 16 to 22 ng/L. The THg concentration of suspended particulates in the runoff (52 µg/kg) was much higher than observed surface soil THg concentrations (mean concentration = 26 µg/kg; n = 6; CV = 16%). Particle size analysis showed the clay content of the runoff sediment was approximately twice that of the bulk surficial soil. These results suggest that snowmelt runoff preferentially mobilizes very fine soil partides (clays) that have a THg concentration that is greater than that of the bulk surficial soil. The total mass of THg in the snowpack prior to snowmelt was 1.26 mg, and that delivered from the catchment during the snowmelt event was 0.36 mg. This suggests there was a net accumulation of THg in the catchment soil over the winter. Soil erosion and transport are the primary mechanisms that control THg delivery from this catchment during snowmelt events.
The Near‐Stream Zone is a Source of Nitrogen in a Swedish Forested Catchment
Authors: Fölster Jens
Published: July 2010

Most Swedish forests efficiently retain N from deposition and runoff N can be expected to originate from the near‐stream zone. Nitrogen leaching from this region is low, but still may be of ecological relevance (e.g., in oligotrophic lakes). In the present study the function of the near‐stream zone with respect to N chemistry in stream water of a small pristine catchment in central‐south Sweden was investigated. The study included ground water, soil water, and stream water sampling. The aim was to explain the variation in N species in stream water with hydrological flow paths and the spatial and temporal variation in N in ground water and soil water. Nitrate and ammonium concentrations were negligible in ground water and soil water at most locations. When nitrate occurred, it was usually at concentrations below 100 µg N L−1 and related to higher pH and aerobic conditions. Ammonium was detected in anaerobic locations at stable concentrations up to 200 µg N L−1. The near‐stream zone was the main source of organic N entering the stream where the median concentration was 240 µg L−1. Nitrate occurred only occasionally in stream water at concentrations around 100 µg N L−1 and then probably originated from near‐stream pre‐event water. The only significant ammonium concentrations were detected during a spring flow episode and there were indications of flushing of organic matter of microbial origin. The importance of within‐catchment variation for understanding leaching processes in forested catchments is discussed.
Nonsingular Sorption of Organic Compounds in Soil: The Role of Slow Kinetics
Authors: Altfelder Sven , Streck Thilo , Richter Jörg
Published: July 2010

Nonsingular sorption‐desorption behavior of organic compounds has been frequently observed, but it remained unexplained in many cases. In this study we investigate the role slow kinetics may play in nonsingular sorption. Sorption‐desorption experiments were carried out with the herbicide chortoluron (3‐(3‐chloro‐p‐tolyl)‐1,1‐dimethylurea) and two soils—a silt loam and a loamy sand—using three different batch techniques. The first technique is the classic decantrefill method where part of the supernatant is replaced with solute‐free solution. The second technique is similar;, however, part of the supernatant is replaced with solute containing solution instead. In the third technique desorption is induced by successive dilution of the supernatant with time. Nonsingular sorption of chlortoluron was observed independent of the method. We fitted a kinetic two‐stage model to the data of the first technique to estimate sorption rate parameters. With this set of parameters, the model predicted the data measured with the second and third technique well. The agreement indicates that nonsingularity phenomena observed by means of the different techniques may be explained by slow sorption kinetics. The ability of the model to describe nonsingular sorption‐desorption data was further tested on data sets taken from the literature where nonsingularity remained unexplained or was explained by other causes different from slow kinetics. All phenomena observed in the different studies could readily be explained by the two‐stage model.
Rice Pesticide Concentrations in the Colusa Basin Drain and the Sacramento River, California, 1990–1993
Authors: Crepeau Kathryn L. , Kuivila Kathryn M.
Published: July 2010

The pesticides molinate, thiobencarb, and carbofuran are applied to rice (Oryza sativa L.) fields in the Sacramento Valley, California, each year during April through June. These pesticides are of concern because of their adverse effects on water quality and their potential adverse effects on aquatic life. Therefore, the California Regional Water Quality Control Board (CRWQCB) mandated the holding of irrigation‐return water in rice fields to increase pesticide degradation and dissipation before the water is released to the Sacramento River. The CRWQCB also established performance goals to maintain drinking water quality for the city of Sacramento and to protect the habitat for aquatic life. The objectives of this study were to determine the effects of increased irrigation‐return water holding times on rice pesticide concentrations and loads in the Colusa Basin Drain and the Sacramento River. Dissolved pesticide concentrations were measured in water samples collected in May through July during 1990–1993 at the Colusa Basin Drain at Road 99E near Knights Landing (Colosa Basin Drain) and at the Sacramento River at Sacramento. Pesticide concentrations and loads at both sites showed a decrease from 1990–1992 and an increase in 1993. This trend cannot be explained by the yearly holding time regulations but can be explained by the amount of yearly emergency releases. The yearly changes in pesticide concentration detected demonstrate that continued monitoring and management of pesticides is necessary to maintain water quality.
Chemical Characterization of Ash from Gasification of Alfalfa Stems: Implications for Ash Management
Authors: Mozaffari M. , Rosen C. J. , Russelle M. P. , Nater E. A.
Published: July 2010

Electricity generation from biomass is an attractive option from an environmental perspective. Pilot studies have indicated that alfalfa (Medicago sativa L.) stems are suitable feedstock for energy generation via gasification. Detailed information on chemical characteristics of the ash generated from gasification of alfalfa stem is required to develop environmentally and economically sound ash management strategies. Alfalfa fly and bottom ashes were characterized with respect to chemical properties that are important in developing ash management practices with emphasis on beneficial utilization as a soil amendment. Mean concentrations of total C, K, Ca, and Cl were 424, 120, 85, and 26 g kg−1, respectively, in fly ash. In bottom ash, the mean concentrations of C, K, and Ca, were 63, 61, and 193 g kg−1. Concentrations of total Pb, As, Cd, Co, and Se were below detection limits in both ash types. Naphthalene ranged from 6.2 to 74 mg kg−1, but concentrations of many other polyaromatic hydrocarbons were low or below mg kg−1 detection limits. Available K and P in fly ash were 90 to 120 and 8 to 10 g kg−1, respectively. Mean CaCO3 equivalent value of fly ash was 400 g kg−1, its electrical conductivity (EC) and pH were 127 dS m−1 and 11.5, respectively. These results suggest that when managed properly, gasified alfalfa ash could potentially be utilized as a beneficial soil amendment with few potential environmental concerns.
Organic Phosphorus Source Effects on Calcareous Soil Phosphorus and Organic Carbon
Authors: Robbins C. W. , Freeborn L. L. , Westermann D. T.
Published: July 2010

The loading, solubility, mobility, and plant availability of P is a growing environmental concern to regulators and planners of nutrient management plans, confined animal feeding operations, and wastewater land application permit sites. Insufficient information is available on how P reacts from different organic sources when applied to calcareous soils. A field study was conducted to determine the interactions among P application rate, source, extractability, and soil organic carbon (OC) concentration. A Portneuf silt loam (Coarse‐silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids) topsoil and freshly exposed subsoil were fertilized with monocalcium phosphate (MCP), cheese whey, and dairy manure. Organic matter added with the whey did not influence soil OC concentrations whereas organic matter added with the manure doubled the subsoil OC and increased the topsoil OC concentrations. Bicarbonate and saturation paste extractable ortho‐ and organic‐P concentrations were linearly related to soil OC concentrations but were not related to the amount of ortho‐ or organic‐P added. All forms of P increased more per unit of added P in the order manure > whey > MCP and were correlated with the soil OC concentrations. These results suggest organic waste applications should be managed from soil P test data rather than on P application rates.
Removal of Perchlorate from Ground Water by Hydrogen‐Utilizing Bacteria
Authors: Giblin Tara L. , Herman David C. , Frankenberger W. T.
Published: July 2010

An autotrophic consortium of bacteria, utilizing hydrogen and bicarbonate as electron and carbon sources, respectively, for the reduction of perchlorate has been enriched. The efficiency of this consortium for perchlorate reduction in a packed‐bed bioreactor is described. The use of hydrogen as an electron source for microbial biodegradation of pollutants in a packed‐bed bioreactor is advantageous because hydrogen does not promote vigorous biomass growth, resulting in less clogging of the system, and hydrogen gas reduces the need for post‐reactor water cleanup. The consortium, comprised of four bacteria, was capable of removing nitrate and perchlorate simultaneously from mineral salts medium in a batch culture. A 120‐mL bioreactor was designed to test the capacity of the consortium to remove perchlorate in a flow‐through system. At a flow rate of 1 mL min−1, perchlorate levels naturally occurring in San Gabriel Valley ground water (0.740 mg L−1) were completely removed to less than 0.004 mg L−1, which is the detection limit. However, as the flow rate was increased, the removal efficiency decreased. Factors affecting the rate of perchlorate removal included nonuniform distribution of biomass in the column, unstable pH of the ground water, and limited delivery of hydrogen to the bacteria. This bioreactor also completely removes perchlorate from ground water at a flow rate of 1 mL min−1 without an added carbon source, presumably using the bicarbonate naturally present in the ground water.
Nitrogen Transformations and Losses in Forest Soil Subjected to Sprinkling Infiltration
Authors: Paavolainen Laura , Smolander Aino , Lindroos Antti‐Jussi , Derome John , Helmisaari Heljä‐Sisko
Published: July 2010

Artificial ground water has been produced in Ahvenisto esker in southern Finland by sprinkling lake water directly onto the forest soil. The aim of this study was to investigate N transformations in the soil, especially nitrification, and N losses via leaching and gaseous emissions during the first three years of this sprinkling infiltration. During the first year, the pH of the humus layer increased from about 5 to 6.7 and net nitrification started. Intensive nitrification continued throughout the study period. Although infiltration increased N2O emissions from the soil, the emissions were very small compared with N losses via leaching. The esker retained organic N. The mean (NO2 + NO3)−N concentration in percolation water during infiltration was close to that of the infiltration water (about 0.2 mg L−1) but, during breaks in infiltration, the concentrations generally exceeded 10 mg L−1. The ground water (NO2 + NO3)−N concentration, however, remained very low (mean 0.2 mg L−1) due to dilution of the (NO2 + NO3)−N, produced in the soil, by the large volume of infiltration water. The results of this 3‐yr study show that the leaching of nitrate does not presently pose a threat to the quality of ground water as long as infiltration is continuous. As nitrate was still being produced 2 yr after cessation of infiltration, there is a risk of nitrate leaching into the ground water. The actual risk this poses to ground water quality depends on the size of the infiltration area in relation to the whole aquifer.
Nitrate Dynamics in Relation to Lithology and Hydrologic Flow Path in a River Riparian Zone
Authors: Devito Kevin J. , Fitzgerald Dan , Hill Alan R. , Aravena Ramon
Published: July 2010

The efficiency with which riparian zones remove nitrate (NO−3) from contaminated ground water can vary with landscape setting. This study was conducted to determine the influence of flood plain geometry, lithology, hydrologic flow path, and nitrate transport on mechanisms of nitrate depletion of contaminated ground water. Patterns of NO−3−N, chloride, and dissolved organic carbon (DOC) concentrations and δ15N‐NO−3 and δ18O‐NO−3 values in combination with detailed piezometric head measurements were investigated in a river floodplain connected to a large upland sand aquifer in an agricultural region near Alliston, Ontario, Canada. Ground water discharging to the forested floodplain from the sand aquifer exhibited large spatial variability in NO−3−N concentrations (10–50 mg/L). The transport and depletion of NO−3 was strongly influenced by floodplain geometry and lithology. Little ground water flow occurred through the low‐conductivity matrix of peat in the floodplain. Plumes of NO−3‐rich ground water passed beneath the riparian wetland peat and flowed laterally in a 2‐ to 4‐m‐thick zone of permeable sands across the floodplain to the river. Analyses of the distribution of the NO−3−N concentrations, isotopes, and DOC within the floodplain indicate that denitrification occurred within the sand aquifer near the river where nitrate‐rich ground water interacted with buried channel sediments and surface water recharged from peat to the deeper sands. This study shows that the depth of permeable riparian sediments, ground water flow path, and the location of organic‐rich subsurface deposits may be more important than the width of vegetated strips in influencing the ability of riparian zones to remove nitrate.
Crop Management and Corn Nitrogen Rate Effects on Nitrate Leaching
Authors: Andraski T. W. , Bundy L. G. , Brye K. R.
Published: July 2010

Excess N use in crop production is often identified as a major contributor to NO3 enrichment of ground water. Little information is available to show the specific relationships between crop management systems and N fertilizer use on the amounts of NO3 lost by leaching. This study determined the effect of several cropping systems and N rates, providing a range of N availability to corn (Zea mays L.), on soil water NO3 concentrations and leaching below the root zone. Four cropping‐manure management systems were established in 1993 and 1994 (8‐site years) at Arlington, WI, on a Plano silt loam (fine‐silty, mixed, superactive, mesic Typic Argiudoll). Ammonium nitrate (0 to 204 kg N ha−1 in 34‐kg increments) was broadcast at the time of corn planting. Economic optimum N rates (EONR) for corn ranged from 0 to 150 kg ha−1 depending on site‐year. Soil water NO3 concentrations were determined for 18‐mo using porous‐cup samplers installed at a 120‐cm depth in the 0 and 204 kg N ha−1 treatments. Nitrate N concentrations in the samplers increased as the amount of N applied in excess of the observed EONR increased. Predicted soil water NO3−N concentration at EONR was 18 mg L−1. Average NO3−N concentrations were <10 mg L−1 where fertilizer N rates were >50 kg N ha−1 below the EONR and >20 mg L−1 where fertilizer N rates were >50 kg N ha−1 above the EONR. Total NO3−N leaching estimates based on water budget data and soil water NO3 concentrations for the 18‐mo study period ranged from 3 to 88 kg ha−1 depending on crop and manure management system, N fertilizer rate, amount of water drainage, and time of drainage event relative to treatment establishment. An end‐of‐season soil NO3 test appears to be capable of evaluating corn N management practices and indicating the amount of excess N fertilizer applied that may be leached from the root zone. These results illustrate the direct relationship between NO3 loss by leaching and N application rates that exceed crop needs.