bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of Nitrate Concentrations in Groundwater Using a Whole Farm Nitrogen Budget
Authors: Barry D. A. J. , Goorahoo D. , Goss M. J. 
Published: July 2010

AbstractContamination of groundwater under agricultural land by NO3 is influenced by the kind of farming system. One possible method of selecting farming systems that result in less NO3 leaching is to calculate whole farm N budgets, that are simplified by assuming soil‐N remains constant from one cycle of a rotation to the next. This method was applied to two model crop rotations using average crop yield data for two regions of Ontario, and to a cash‐crop farm and a dairy farm using information on purchases, sales, and crop yields, for these farms. The model rotations were corn (Zea mays L.)‐soybean [Glycine max (L.) Merr.]‐wheat (Triticum aestivum L.) and corn‐soybean‐wheat‐hay (mixture of timothy, Phleum pratense L. and alfalfa, Medicago sativa L.)‐hay‐hay. Atmospheric deposition (18.4 kg N ha−1 yr) was obtained by literature review. Symbiotic N2 fixation by legume crops with different yields was estimated from regression equations. A net surplus in the N balance was converted to maximum mean NO3‐N concentration in groundwater by assuming a groundwater recharge rate of 160 mm yr−1, and no denitrification. Predicted NO3‐N concentrations in leachate for the model corn‐soybean‐wheat rotation were greater for southwestern Ontario (22.4 mg L−1) than western Ontario (8.5 mg L−1), probably because more fertilizer was recommended in the southwest. Including hay in the model rotation increased the amount of N leached by a factor of two in western Ontario, but only by 9% in the southwest. Predicted NO3‐N concentration in groundwater for the cash crop farm was 6.7 mg L−1, compared with an average measured value of 9.5 mg L−1 in the tile drainage water. For the dairy farm the predicted value was 58 mg L−1 and a measured value was not available. The simplified N balance method provided useful estimates of potential NO3 leaching losses even though it relied on some major assumptions. A major uncertainty was atmospheric deposition of ammonia volatilized from on‐farm sources. Denitrification could be as much as 62 kg N ha−1 yr−1 under continuous production of grain corn, based on differences between N present after harvest and amount of N leached.
Theoretical Investigation of Multicomponent Volatile Organic Vapor Diffusion: Steady‐State Fluxes
Authors: Amali S. , Rolston D. E. 
Published: July 2010

AbstractLiquid mixtures of volatile organic chemicals (VOC) contaminating many underground sites give rise to multicomponent mixtures of their vapors. Previous investigation has shown that in an isoharic, isothermal multicomponent vapor system, Fick's law estimates of the diffusive flux for each species should not be used when the effective binary diffusion coefficients used are sufficiently different. Our theoretical investigation of a multicomponent, semihypothetical “gasoline” mixture containing relatively volatile aromatic constituents plus CCl4 as an additional component shows that the multicomponent effect also can be observed when the binary diffusion coefficients are not substantially different, but when the total mole fraction of the diffusing species is sufficiently high. The importance of both diffusion coefficients and total mole fraction when modeling total diffusive fluxes requires that simulations be performed for any given vapor mixture. For our “gasoline” mixture, an approximate total mole fraction of 0.05 was found to lead to underestimation of single species fluxes by Fick's law of up to 5%. Simulations of steady‐state fluxes further indicate that O2 and N2 do not need to be treated differently and can be combined to form one species, “air.” Likewise various VOC species with almost identical diffusion coefficients can be grouped to form one representative class. Our investigation of diffusion in nonuniform, multinary mixtures of gases also included pressure diffusion. Pressure diffusion causes heavier (lighter) molecules to diffuse toward the higher (lower) pressure regions of a closed system. The contribution of pressure diffusion to the total diffusive flow under the natural gravitational pressure gradient was calculated to be significant only when the simulated soil column was more than 100 m long. It does not need to be included in multicomponent diffusion formulations involving shorter transport lengths.
Alkaline Phosphatase Activity in the Sediment‐Water Column of a Hypereutrophic Lake
Authors: Newman S. , Reddy K. R. 
Published: July 2010

AbstractInorganic P limitation in many aquatic systems may be overcome through the enzymatic hydrolysis of organic P compounds. The objective of our study was to determine the effect of dissolved oxygen (DO) of the water column and redox (Eh) status of the sediments on alkaline phosphatase activity (APA) in a shallow hypereutrophic lake located in central Florida. Alkaline phosphatase activity was used as an index of potential organic P mineralization. Lake water was incubated in the dark under aerobic and anaerobic conditions for 24 h. Under aerobic conditions APA increased from 22 to 43 nM min−1 within 24 h. Under anaerobic conditions no significant change in APA was observed. Neither total soluble P nor soluble‐reactive P exhibited significant responses to anoxic conditions in the water column. The increase in APA observed under aerobic conditions was attributed to increased plankton metabolic P demand following depletion of internal cell P. Sediments were incubated under six different Eh levels for 30 d. In combination with APA measurements, sediment organic P was fractionated into labile and nonlabile pools using selected inorganic chemical extractants. Phosphatase hydrolysis of organic P was significantly inhibited under anaerobic conditions. Alkaline phosphatase activity was positively related to pE + pH (r = 0.90). Conversely, porewater organic P was inversely correlated with pE + pH (r = −0.92). Alkaline phosphatase activity was also inversely related to porewater organic P (r = −0.95), labile organic P (r = −0.81), and humic acid P (r = −0.74). The results of this study suggest that short‐term depletion of DO will not affect the enzymatic breakdown of organic P within the water column. Significant reduction in the alkaline phosphatase‐dependent hydrolysis of sedimentary organic P will occur under anaerobic conditions; hence, P cycling in highly organic sediments may be severely inhibited.
Soil Nitrate Leaching Potential Indices: Using a Simulation Model as a Screening System
Authors: Khakural B. R. , Robert P. C. 
Published: July 2010

AbstractSimulation models LEACHM‐N (Leaching Estimation and Chemistry Model) and NLEAP (Nitrate Leaching and Economic Analysis Package) were first tested using NO3 leaching data obtained from lysimeter and tile drainage studies conducted at three University of Minnesota experiment stations. Both simulation models did well in simulating total (seasonally accumulated) leaching loss of NO3‐N from the soil profile. LEACHM‐N was selected as a screening tool to develop soil NO3 leaching potential (NLP) ratings using soil survey information and representative county weather station data. Simulated growing season total NO3‐N leached from the soil profile (below 1.5 m) were used as NLP index. Crop management practices and initial N were kept constant. Soil NO3 leaching potential ratings for three Minnesota counties, Redwood, Stearns, and Sherburne were developed using this method. This soil NLP rating information was included in the Soil Survey Information System (SSIS) to create leaching potential rating maps, which can be used to plan best N management schemes.
The Determination of Total Dissolved Inorganic Carbon in Aqueous Solutions
Authors: Frisbie Seth H. , Bouldin David R. 
Published: July 2010

AbstractExperimental results and theoretical considerations were utilized to develop a method for the precise and accurate determination of total dissolved inorganic carbon (TDIC) in aqueous solutions. A method of preparing standard solutions of Cs2CO3 from distilled deionized H2O which was initially stripped of ambient inorganic carbon (IC) with N2(g) at 6.90 × 104 Pa for 20 min allowed a means of calibration without systematic error. For a 0.20‐mL sample, a quadratic working range of analysis extended from the limit of detection, 1.05 × 10−5M IC, to 3.44 × 10−3 M IC. Results are accurate to three significant figures. The smallest R2 observed over 4 yr was 0.997. For 0.05‐, 0.10‐, and 0.20‐mL sample volumes, no significant effect of solution volume on detector response was observed. In order to expedite routine analysis, a means of preparing and storing secondary standard solutions of NaHCO3 for up to 28 d was developed.
Recycling of Cattle Manure: The Composting Process and Characterization of Maturity
Authors: Inbar Yossi , Hadar Yitzhak , Chen Yona 
Published: July 2010

AbstractThe utilization of cattle (Bos sp.) manure as a peat substitute in greenhouses has been proposed. This alternative requires certain preparatory procedures, including composting. The objective of this research was to study the composting process, changes occurring in the product during composting and product properties of relevance to its potential use as a container medium, and to evaluate possible criteria indicating compost maturity. Composting of separated cattle manure (CSM) was studied in 1‐m3 perforated boxes. Most of the physical and some of the chemical properties exhibited a high rate of change during the first 40 to 60 d of the composting process. Total water‐soluble salts, as measured by electrical conductivity (EC), exhibited a constant value for the first 60 d, followed by a sharp increase in EC (from 2.6–5.4 dS m−1). The main ions contributing to this increase were NO−3, Ca2+ and Mg2+. As temperature decreased, nitrate levels increased sharply due to nitrification, from 0.02 cmol L−1 at the beginning to 4.0 cmol L−1 at the end of the composting process. Although most changes took place during the first high temperature phase, slow decomposition persisted after temperature returned to ambient level as measured in the compost water extract. Plant bioassays also indicated that 40‐ to 60‐d old compost inhibited growth and there was limited response to fertilization. Both of these factors were eliminated after 80 to 90 d of composting. Chemical properties of water extracts may therefore serve as indicators of compost maturity and of the material's suitability as an organic component for container media.
Minimizing Agricultural Nonpoint‐Source Impacts: A Symposium Overview
Authors: Sharpley Andrew , Meyer Mike 
Published: July 2010

AbstractIncreased public awareness of the role of agriculture and associated chemical use in nonpoint‐source pollution has prompted an urgency in obtaining information on the impact of current and proposed agricultural management practices on water quality. Because of easier identification and control of point sources of pollution, agricultural nonpoint sources now account for a larger share of all discharges than a decade ago. Consequently, there is a need to identify critical sources for control; target specific controls for different water quality objectives within different watersheds; and evaluate and implement cost‐effective management practices that minimize the potential loss of agricultural chemicals to surface and groundwaters. This paper provides a brief overview of agricultural nonpoint‐source issues and options presented at a special symposium, “Minimizing Agricultural Nonpoint‐Source Impacts,” held during the American Society of Agronomy meetings in November 1992 and cosponsored by the Metropolitan Waste Control Commission. Several papers that were given at this symposium and presented in this issue are introduced.
Interlaboratory Comparison of Iron Oxide‐Impregnated Paper to Estimate Bioavailable Phosphorus
Authors: Sharpley A. N. , Indiati R. , Ciavatta C. , Rossi N. , Sequi P. 
Published: July 2010

AbstractThe transport of bioavailable phosphorus (BAP) in agricultural runoff can accelerate the eutrophication of receiving water bodies. However, procedural and theoretical limitations of algal bioassays and chemical extractants have restricted widespread measurement of BAP. Thus, a simple method using iron oxide—impregnated paper (Fe‐oxide strips) as a sink for BAP in runoff samples has been developed. As the method has potential application for BAP extraction at one location and analysis at another, Fe‐oxide strips were sent to Bologna and Rome, Italy, for P extraction of runoff samples and BAP determined. These BAP estimates were not significantly different (p < 0.001) from values determined on duplicate strips returned to the USA for BAP analysis. The close agreement in BAP measured in Italian and U.S. laboratories indicates that the simplicity of the proposed method can give highly reproducible BAP estimates. Prepared Fe‐oxide strips may be sent to a location and BAP extracted using only a 100‐ to 500‐mL bottle in which a strip and runoff sample are shaken overnight. The Fe‐oxide strip may then be air‐dried and returned to an analytical laboratory for subsequent P removal and measurement. Storage of these strips for up to 60 d had no effect on the amounts of P released.
Evaluating Agricultural Nonpoint‐Source Pollution Using Integrated Geographic Information Systems and Hydrologic/Water Quality Model
Authors: Tim Udoyara S. , Jolly Robert 
Published: July 2010

AbstractConsiderable progress has been made in developing physically based, distributed parameter, hydrologic/water quality (H/WQ) models for planning and control of nonpoint‐source pollution. The widespread use of these models is often constrained by the excessive and time‐consuming input data demands and the lack of computing efficiencies necessary for iterative simulation of alternative management strategies. Recent developments in geographic information systems (GIS) provide techniques for handling large amounts of spatial data for modeling nonpoint‐source pollution problems. Because a GIS can be used to combine information from several sources to form an array of model input data and to examine any combinations of spatial input/output data, it represents a highly effective tool for H/WQ modeling. This paper describes the integration of a distributed‐parameter model (AGNPS) with a GIS (ARC/INFO) to examine nonpoint sources of pollution in an agricultural watershed. The ARC/INFO GIS provided the tools to generate and spatially organize the disparate data to support modeling, while the AGNPS model was used to predict several water quality variables including soil erosion and sedimentation within a watershed. The integrated system was used to evaluate the effectiveness of several alternative management strategies in reducing sediment pollution in a 417‐ha watershed located in southern Iowa. The implementation of vegetative filter strips and contour buffer (grass) strips resulted in a 41 and 47% reduction in sediment yield at the watershed outlet, respectively. In addition, when the integrated system was used, the combination of the above management strategies resulted in a 71% reduction in sediment yield. In general, the study demonstrated the utility of integrating a simulation model with GIS for nonpoint‐source pollution control and planning. Such techniques can help characterize the diffuse sources of pollution at the landscape level.
Importance of Soil and Cropping Systems in the Development of Regional Water Quality Policies
Authors: Geleta S. , Sabbagh G. J. , Stone J. F. , Elliott R. L. , Mapp H. P. , Bernardo D. J. , Watkins K. B. 
Published: July 2010

AbstractTargeting certain soils and cropping systems may be necessary in consideration of regional water quality protection policies. However, little information is available relating soils and cropping practices to regional water quality problems. This study evaluates crop yield and NO3‐N movement to surface and groundwater on four soils and nine principal cropping systems in the High Plains region of Oklahoma. The cropping systems involve wheat (Triticum aestivum L.), grain sorghum [Sorghum bicolor (L.) Moench], and corn (Zea mays L.), and are part of a regional data base also containing soils and chemical management information. For each combination of crop, soil, cropping system, and chemical alternative, a 20‐yr simulation was made. The simulation was based on a modeling system that includes EPIC‐PST (crop growth/chemical movement model) interfaced with a Geographic Information System (GIS), Earthone. Results of each simulation included crop yield and NO3‐N movement in runoff and percolation. Results show wide variations in NO3‐N losses for different soils, irrigation systems, and cropping systems. When compared with continuous irrigated wheat and grain sorghum cropping systems, double‐cropped wheat‐grain sorghum resulted in greater NO3‐N loss in percolation. Compared with sprinkler and LEPA (low energy precision application) irrigation systems, furrow irrigation resulted in high NO3‐N loss on both fine‐textured and coarse‐textured soils, with significantly greater loss on the coarser‐textured soils. The modeling framework can be used to compare alternative water quality policies. Broad policies such as a restriction on the amount of N that can be applied per hectare can be compared with targeted policies, such as limiting N applications or irrigation water use on coarser soils or under furrow irrigation.
Effect of Drying and Rainfall Intensity on Cyromazine Loss from Surface‐Applied Caged‐Layer Manure
Authors: Pote D. H. , Daniel T. C. , Edwards D. R. , Mattice J. D. , Wickliff D. B. 
Published: July 2010

AbstractMost poultry manure is surface‐applied as pasture fertilizer. Cyromazine (N‐cyclopropyl‐1,3,5‐triazine‐2,4,6‐triamine), a feed through larvicide used to control house flies (Musca domestica), is often a manure component in caged‐layer (Gallus gallus domesticus) systems. Since cyromazine is quite soluble and stable in water, the objective of this study was to quantify cyromazine in runoff and soil water from pasture treated with caged‐layer manure. Plots of uniform slope were bordered to isolate runoff and planted in fescue (Festuca arundinacea Schreb). Manure was analyzed for cyromazine content and applied at 0, 4.4, and 17.7 Mg ha−1 (dry basis). Rain was applied by simulator at 50 and 100 mm h−1. Runoff was analyzed for cyromazine and its metabolite, melamine (1,3,5‐triazine‐2,4,6‐triamine). A high manure application rate increased runoff volume and cyromazine concentration. High rain intensity increased total cyromazine runoff loss but provided enough runoff volume to reduce the concentration. Mean cyromazine concentration in runoff was as high as 101 µg L−1, and mean cyromazine loss was as high as 23.7%. Pan lysimeters monitored soil water in the vadose zone for 1 yr after the manure application, but cyromazine and melamine were not detected. In a follow‐up study, plots received manure at 3.76 Mg ha−1, were allowed to dry for either 1 or 7 d, and then received rain at 50 mm h−1 for 30 min of runoff. The 7‐d drying time decreased cyromazine loss, apparently by reducing both runoff volume and cyromazine concentration in the runoff.
Phosphorus in Drainage Water from Sugarcane in the Everglades Agricultural Area as Affected by Drainage Rate
Authors: Coale F. J. , Izuno F. T. , Bottcher A. B. 
Published: July 2010

AbstractSugarcane (interspecific hybrids of Saccharum spp.) is grown on 78% (156,000 ha) of the cultivated organic soils of the Everglades Agricultural Area (EAA) of southern Florida. Recently, the EAA has come under scrutiny because of concerns with the impact of nutrient‐rich drainage water from organic soils on the ecology of adjoining bodies of water and wetlands. The objectives of our research were to determine the effects of field drainage rate on P concentration and off‐field P loads in drainage water from sugarcane grown on organic soils of the EAA and to determine the effect of field drainage rate on sugarcane productivity and sugar yield. The research site was on a Terra Ceia muck soil (euic, hyperthermic Typic Medisaprist) on a commercial sugarcane farm located in the EAA. The treatments were fast and slow field drainage rates. Nine drainage events were monitored between Nov. 1988 and Aug. 1990. Average drainage water total P (TP) and total dissolved P (TDP) concentrations were significantly higher for the slow drainage rate treatment. In order to minimize off‐farm P loading, main‐farm canal water should be discharged off‐farm while field drainage water is retained on‐farm. Field drainage rate should be fast and drainage event duration should be as short as possible. Plant‐cane crop yield and yield component data were not collected. The first‐ratoon crop total aerial dry weight and harvested sugarcane and sugar yields were not affected by drainage rate.
Nitrogen Accumulation and Form over Time in Young Mine Soils
Authors: Li R. S. , Daniels W. L. 
Published: July 2010

AbstractNitrogen deficiency is a common problem during reclamation of mine soils, and limited comprehensive information is available concerning the forms and characteristics of N in Appalachian mine soils. This chronosequence study was conducted to investigate the accumulation, distribution, and component change of N in mine soils over time. Fresh spoil, coal, natural forest soil and 10 mine soil sites with ages ranging from 1 to 30 yr were sampled and analyzed for N components. Young mine soils (> 10 yr) were dominated by seeded grass‐legume vegetation, while the older sites supported native mixed hardwoods. There was a considerable amount of indigenous N in the fresh spoils (250–475 mg kg−1), consisting primarily of fixed NH+4 (Fix‐N) held in micas and nonhydrolyzable organic N (NoHyOM‐N) bound in coal. Both the Fix‐N and NoHyOM‐N fractions were geologic N, stable in chemical character, and unavailable to plants. With time, N accumulation occurred primarily in the surface 0 to 5 cm, associated with A horizon development. In this layer, soil total N and active N [Act‐N, consisting of hydrolyzable organic N (HyOM‐N) and exchangeable N (Exch‐N)], were significantly correlated with site age. The corrected‐N (Corr‐N), which was obtained by subtraction of soil total N at 10 to 20 cm from soil total N at 0 to 5 cm at each site, had a much higher correlation coefficient with site age (r = 0.95, P < 0.0001) due to its correction for variation in soil indigenous N content among sites. The annual rate of N accumulation estimated by the Corr‐N method was 60.5 mg N kg−1 in soil (<2mm) or 23.4 kg N ha−1 in the top 0 to 5 cm. The total C content of the mine soils was correlated with site age (r = 0.65, P < 0.05), while pH, N availability index, Fix‐N, and NoHyOM‐N were not.