bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrate Losses through Subsurface Tile Drainage in Conservation Reserve Program, Alfalfa, and Row Crop Systems
Authors: Randall G. W. , Huggins D. R. , Russelle M. P. , Fuchs D. J. , Nelson W. W. , Anderson J. L.
Published: July 2010

Subsurface drainage of gravitational water from the soil profile through tiles is a common practice used to improve crop production on poorly drained soils. Previous research has often shown significant concentrations of nitrate‐N (NO3‐N) in drainage water from row‐crop systems, but little drainage research has been conducted under perennial crops such as those used in the Conservation Reserve Program (CRP). Four cropping systems (continuous corn, a corn‐soybean rotation, alfalfa, and CRP) were established in 1988 to determine aboveground biomass yields, N uptake, residual soil N (RSN), soil water content, and NO3 losses to subsurface tile drainage water as influenced by cropping system. Hydrologic‐year rainfall during the 6‐yr study ranged from 23% below normal to 66% above normal. In dry years, yields were limited, RSN accumulated at elevated levels in all crop systems but especially in the row‐crop systems, soil water reserves and RSN were reduced to as deep as 2.7 m in the alfalfa (Medicago sativa L.) and CRP systems, and tile drainage did not occur. Drainage occurred only in the corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] systems in the year of normal rainfall. In years of excess precipitation, drainage from the row‐crop systems exceeded that from the perennial crops by 1.1 to 5.3X. Flow‐weighted average NO3‐N concentrations in the water during the flow period of this study were continuous corn = 32, corn‐soybean rotation = 24, alfalfa = 3 and CRP = 2 mg/L. Nitrate losses in the subsurface drainage water from the continuous corn and corn‐soybean systems were about 37X and 35X higher, respectively, than from the alfalfa and CRP systems due primarily to greater season‐long ET resulting in less drainage and greater uptake and/or immobilization of N by the perennial crops.
Impact of Alternative Farm Management Practices on Nitrogen Pollution of Groundwater: Evaluation and Application of CENTURY Model
Authors: Yiridoe Emmanuel K. , Voroney R. Paul , Weersink Alfons
Published: July 2010

An important environmental issue for Canadian agriculture is groundwater‐N pollution. Addressing this issue requires understanding the impact of farm management practices on nitrate leaching, but empirical studies are limited by resource and time constraints. The CENTURY model was adapted to southwestern Ontario agricultural conditions and then used to predict short‐ to medium‐term effects of crop choice and crop rotation pattern, fertilizer management, and tillage practice on N leaching. CENTURY model evaluation suggests that aboveground C production (translated into grain yield) and N leaching predicted by CENTURY provide good representation of results from actual field‐measured data. Results suggest that relative reduction in groundwater‐N leached is markedly greater at higher rates of fertilizer application than at lower (below the maximum economic rate of N fertilization) rates. Although tillage may not dramatically affect N leaching, other farm management practices such as crop type and crop rotation choice, along with the carry‐over effects of these management activities on mineralization of soil organic matter, may have a significant effect on N leaching from the root zone.
Adsorption of Imazethapyr to Amended and Nonamended Soils and Humic Acids
Authors: Senesi Nicola , La Cava Paolo , Miano Teodoro M.
Published: July 2010

Soil amendment with municipal sewage sludge affects the total amount and chemical nature of soil organic matter, including its humic acid (HA) component. These effects are expected to modify the quantitative and mechanistic aspects of herbicide adsorption to soil. The magnitude and mechanisms of adsorption of the imidazolinone herbicide, imazethapyr, to sewage‐sludge amended and nonamended soils, and their HA components, were studied using a batch equilibrium method coupled with high‐pressure liquid chromatography, and by Fourier‐transform infrared (FT‐IR), fluorescence and electron spin resonance (ESR) spectroscopic techniques. Sludge‐amended soils exhibited nonlinear, L‐shaped adsorption isotherms, and much higher adsorption capacity than nonamended soils, which had linear isotherms. Soil‐solated HAs had nonlinear, L‐shaped isotherms and adsorbed imazethapyr in amounts much higher than the corresponding whole soils. Spectroscopic data indicate that imazethapyr may interact with HAs through multiple‐binding mechanisms including ionic, charge‐transfer, and hydrogen bonds. Results of this work indicate that organic matter applied as sludge amendment to soil is able to increase the magnitude and modify the mechanism of imazethapyr adsorption to soil, and confirms the prominent role played by HAs in this process.
Sorption Behavior and Competition of Bromacil, Napropamide, and Prometryn
Authors: Turin H. J. , Bowman R. S.
Published: July 2010

Groundwater contamination by pesticides is a problem of major and increasing concern. Detailed field measurements reveal that leaching of pesticides from soils is often faster than predicted using simple models. This discrepancy is likely due to a combination of physical effects (e.g., preferential pathways) and complexities in the chemical sorption process. To address the issue of sorption complexity, a series of laboratory batch sorption studies have been conducted to determine the detailed sorption behavior of three herbicides, bromacil [5‐bromo‐6‐methyl‐3‐(1‐methylpropyl)‐2,4(1H,3H)pyrimidinedione], napropamide [N,N‐diethyl‐2‐(1‐naphthalenyloxy)propanamide], and prometryn [N,N′‐bis(1‐methylethyl)‐6‐(methylthio)‐1,3,5‐triazine‐2,4‐diamine], onto a sandy loam soil. The studies were designed to determine the extent of nonideal sorption behavior, specifically nonequilibrium, nonlinearity, sorption hysteresis, and solute‐solute interactions. Results showed all three herbicides reached sorption equilibrium quickly, within 2 h. Both napropamide and prometryn were linearly sorbed, while bromacil sorption followed a Freundlich isotherm, with n = 0.92. All three herbicides displayed apparent sorption hysteresis. Bromacil and napropamide sorption decreased in the presence of the other herbicides, while prometryn sorption was unaffected. Contrary to most literature data, napropamide was more strongly sorbed than prometryn in these studies, due to the high pH of the soil. Results suggest that sorption nonlinearity and competition may increase field‐scale transport velocities by 10% or more.
Papermill Sludge Amendments, Tree Protection, and Tree Establishment on an Abandoned Coal Minesoil
Authors: Kost D. A. , Boutelle D. A. , Larson M. M. , Smith W. D. , Vimmerstedt J. P.
Published: July 2010

We measured survival, growth, and foliar nutrition of white ash (Fraxinus americana L.), sycamore (Platanus occidentalis L.), and black walnut (Juglans nigra L.) on a regraded minesoil (Typic Udorthent, pH 2.9) treated with four combinations of papermill sludge depth by incorporation methods. We also compared tree performance when protected from mammal damage by tube, netting, or no shelters. Sludge rates were approximately 860 Mg ha−1 for a 15‐cm depth and 3450 Mg ha−1 for a 60‐cm depth. After 4 yr, tree survival was 65% when either 15 or 60 cm of sludge was deep incorporated by a backhoe. Survival was 43% if 15 cm of sludge was rototill incorporated and 3% if 45 cm of sludge was surface applied over the rototiller‐incorporated sludge (60 cm total sludge depth). Trees were tallest (236 cm) on 15 cm‐backhoed, intermediate (204 cm) on 60 cm backhoed, and shortest (130 cm) on 15 cm rotilled treatments. Ash (56% survival) survived better than sycamore (40%) and walnut (36%). Tree survival was best (61%) in tubes, intermediate (43%) in nets, and worst (28%) with no protection. Ash and walnut were tallest (177 cm) in tubes, intermediate (124 cm) in nets, and shortest (103 cm) with no protection. Sycamore height (305 cm) was not affected by the shelters. Foliar nutrition of trees was adequate except for possible low P in ash. In summary, tree survival and growth were good if sludge was incorporated by backhoeing and trees were protected by tube shelters.
Evaluation of Leachate Quality from Codisposed Coal Fly Ash and Coal Refuse
Authors: Stewart Barry R. , Daniels W. Lee , Jackson Meral L.
Published: July 2010

The exclusion of coal fly ash from regulation as a hazardous waste has led to increased interest in returning ash to the coal fields for disposal. Bulk blending alkaline fly ash with acid forming coal refuse may present a disposal option that also aids in the control of acid mine drainage (AMD). A column leaching study was initiated to examine the leachate quality from acid forming coal refuse‐fly ash blends. Coal refuse alone (2.2% total S), and bulk blended coal refuse and alkaline fly ash (20 and 33% ash, w/w) were packed into 20‐cm diameter leaching columns and run under unsaturated conditions for over 4 yr. Leachates were analyzed for pH, electrical conductivity, Fe, Mn, and SO2−4 content. The coal refuse columns acidified quickly and produced leachates that, at peak levels, contained high contents of acidity (pH 1.6), Fe (10 000 mg L−1), SO2−4 (30 000 mg L−1), and Mn (300 mg L−1). The high levels of metals in these leachates decreased over time. The ash‐treated columns maintained leachate pH values near 8.0 with very low metal levels. The bulk mixing of alkaline fly ash and coal refuse, at high blending rates (>20%), appears to an effective codisposal option that also provides long‐term AMD control. Only B and SO2−4 appeared to leach at any significant level and the quality of leachates from the ash‐treated columns was significantly improved with respect to the untreated coal refuse.
Phytotoxicity and Plant Uptake of Fuel Oil Hydrocarbons
Authors: Chaîneau C. H. , Morel J. L. , Oudot J.
Published: July 2010

The phytotoxicity and phytoavailability of hydrocarbons (HC) were studied in soils artificially contaminated with fuel oil. The presence of HC in the soil inhibited seed germination and reduced plant growth. The germination and development of cultivated plants varied with the chemical structure of HC, the HC concentration in soil, and the plant species. The LC50 values for germination after 8 d in the presence of a fuel oil varied from 0.3 to 4% (oil/soil, w/w) for lettuce (Lactuca sativa L.), barley (Hordeum vulgare L.), clover (Trifolium repens L.), and maize (Zea mays L.) and from 4 to 9% for bean (Phaseolus vulgaris L.), wheat (Triticum aestivum L.), and sunflower (Helianthus annuus L.). Light aromatics and naphtas were the most phytotoxic HC. The inhibition of plant growth increased with HC concentration but was not linearly proportional to the loading rate. Reduction in aerial biomass was >80% for wheat and bean at a concentration of 0.3% and <30% for maize at 1.2%. No saturated nor aromatic fuel oil HC was detected by gas‐chromatography in the stems and leaves of maize grown during 110 d on 1.2% oil‐contaminated soil, indicating that no uptake of HC from soils occurred.
Cadmium Sorption and Desorption in Limed Topsoils as Influenced by pH: Isotherms and Simulated Leaching
Authors: Filius Angelika , Streck Thilo , Richter Jörg
Published: July 2010

The influence of pH on cadmium (Cd) sorption and desorption isotherms was studied in sandy and clayey soils of northern Germany. Seventeen topsoils from four long‐term lime amendment experiment plots ranging in pH from 4.1 to 6.9 were collected. Batch adsorption isotherms demonstrated the strong influence of pH on Cd sorption behavior. Cadmium sorption increased with pH, even within a very narrow range of pH values (ΔpH ≈ 0.3). The experimental desorption isotherms, which were determined by widening the soil/solution ratio, differed markedly from the adsorption isotherms. Differences decreased when reaction time for desorption was prolonged. The data for Cd adsorption and desorption were pooled to derive the coefficients of a generalized Freundlich‐type expression S = S(CM) including soil pH in 0.01 M CaCl2 and organic C content (oc) (% by mass) (S = k* (H+)a ocb CM). Sorption isotherms were used for simulations to predict vertical displacement of Cd in the field. The simulations using measured field mean concentration profiles S(z) as initial values, showed Cd adsorption isotherms to be appropriate for describing longer‐term desorption equilibria.
Solubility and Plant Uptake of Metals with and without Liming of Sludge‐Amended Soils
Authors: Krebs R. , Gupta S. K. , Furrer G. , Schulin R.
Published: July 2010

Excessive applications of sewage sludge and pig manure have led to the accumulation of potentially toxic elements in soils. The objective of this study was to examine the NaNO3 extractability of Cu, Zn, and Cd with time and in relation to soil pH and soil organic matter content and to investigate the concentrations of these metals in pea (Pisum arvense L.) as a result of liming. The field study was conducted on an orthic luvisol with pig manure and sewage sludge application rates of 5 t dry organic matter ha−1 yr−1 from 1976 to 1984. After 1984, all field plots were equally treated with mineral fertilizers and in 1991, lime was added to half of each plot. The soil pH decreased in all unlimcd treatments about half a unit from 1985 to 1994. Concurrently, the Zn and Cd concentrations extractable with 0.1 M NaNO3 increased as well as the Cd concentrations in field pea. Liming raised the soil pH by approximately one unit to 6.4 and 6.9 in pig manure‐ and sewage sludge‐treated plots, respectively and resulted in decreasing concentrations of Cu, Zn, and Cd in seeds and crop residues of field pea. The results suggested that plant uptake and solubility of Zn, Cu, and Cd can continue to be higher in sewage sludge‐ and pig manure‐treated soils than in control plots during a 10‐yr period after the applications were ceased. Liming most effectively reduces the solubility and the plant uptake of Zn and Cd.
Adsorption and Desorption of Atrazine, Deethylatrazine, and Hydroxyatrazine by Soil Components
Authors: Moreau‐Kervévan C. , Mouvet C.
Published: July 2010

We studied the behavior of atrazine (AT), deethylatrazinc (DEA), and hydroxyatrazinc (HyA) in contact with humic acid, kaolinite, smectite, goethite, and ferrihydrite through adsorption kinetics and isotherms, and desorption isotherms, in laboratory batch systems. The initial triazine concentrations in solution ranged from 0.001 to 1 mg L−1. The adsorption of the three triazines by each component was significant (except for AT and DEA by the two iron oxides) and the adsorption equilibrium was reached after 72 h. The adsorption isotherms were described by Freundlich equations. Adsorption increased in the order iron oxides < clays < humic acid. On the humic acid and smectite, adsorption increased in the order DEA < AT ≪ HyA, whereas on kaolinite it increased in the order AT < DEA ≪ HyA. The desorption of the three triazines from each component was hysteretic. For each triazine, the amount of nonextractable residue (NER) followed the order kaolinite ~ smectitc < humic acid. On humic acid, the amount of NER increased in the order DEA < AT < HyA, whereas on the clays it increased in the order AT < DEA < HyA. The results demonstrate: (i) the coexistence of heterogeneous adsorption sites on each soil component, (ii) the importance of the intrinsic characteristics of the triazine (e.g., its pKa) (iii) the likely time‐dependent nature of hysteresis, and (iv) varying amounts of NER resulting from a combination of the number of adsorption sites occupied by the molecule and the energy level of the adsorption mechanisms involved.
Effects of Metam Sodium Fumigation on Soil Microbial Activity and Community Structure
Authors: Macalady J. L. , Fuller M. E. , Scow K. M.
Published: July 2010

Metam sodium (MS) is a widely used soil fumigant with broad biocidal activity. The impact of MS on soil microbial community structure and function is largely unknown. We investigated the effects of fumigation with field‐relevant doses of MS in soil microcosms using traditional heterotrophic activity measures (C and N mineralization), a substrate‐utilization assay, and fatty acid analysis. Our results suggest that fumigation with MS results in persistent changes (at least 18 wk) in heterotrophic activity and fatty acid composition of the microbial biomass. Lack of recovery of heterotrophic activity and changes in fatty acid composition after fumigation suggest that MS has the potential to alter important microbially mediated functions such as nutrient cycling and pollutant degradation. Preliminary fatty acid data suggest that actinomycetes and other gram‐positive organisms may recover preferentially after fumigation with MS. Although community fatty acid analysis shows promise as a screening tool in soil microbial toxicity studies, more detailed information can be obtained from analysis of phospholipid fatty acid (PLFA) and other specific lipid fractions.
A Bed Sediment Sampler for Precise Depth Profiling of Contaminant Concentrations in Aquatic Environments
Authors: Quinn Nigel W. T. , Clyde John R.
Published: July 2010

A bed sediment and detritus sampler has been developed for use in aquatic environments, such as in canals, rivers or lakes, for determining precise depth profiles of contaminants. The device is superior to currently available commercial push‐tube and piston samplers in its simplicity, ease of use and its ability to retrieve and extrude sample cores. The sampler has been used with success during the past 12 mo to determine a profile of bed sediment Se concentrations within an earth‐lined canal, alternatively used for conveyance of agricultural drainage and wetland water supply.
Nutrients in a Playa Wetland Receiving Wastewater
Authors: Pezzolesi T. P. , Zartman R. E. , Fish E. B. , Hickey M. G.
Published: July 2010

We determined nutrient sequestration differences in soil and vegetation within two regions of a playa wetland that receives agricultural runoff and secondarily treated wastewater. Playas are small, topographically closed, ephemeral wetlands that serve as catchments for surface runoff in the Southern High Plains of the USA. The wetland studied received natural runoff and secondarily treated wastewater from the U.S. Department of Energy, Pantex facility near Amarillo, TX. Soil and aboveground biomass N, P, Cu, and Fe and water N and P were evaluated seven times during a 2‐yr period in cattail (Typha domingensis Pers.) and pink smartweed [Persicaria pensylvanica (Raf.) Nieuw.] dominated regions of the playa. Spatial and temporal variabilities were observed in water, vegetation, and soil‐nutrient concentrations. These variabilities were likely due to fluctuation of water depth and quality in the playa. Water was deeper (P < 0.05) in the cattail region compared with the smartweed region. Water quality [Total Kjeldahl N (TKN) and total P (TP)] was not effected (P > 0.05) by vegetation type. Soil concentrations of TKN, TP, Cu, and Fe were not significantly different (P > 0.05) between cattail and smartweed vegetative types. Cattail had significantly greater (P < 0.05) levels of TKN, TP, Cu, and Fe than did smartweed. Aboveground biomass was greatest in August. Based on nutrient sequestration this playa wetland functioned quite well as a receptor for added nutrients from runoff and the wastewater treatment facility.
In‐Stream Nonpoint Source Nutrient Prediction with Land‐Use Proximity and Seasonality
Authors: Tufford Daniel L. , McKellar Hank N. , Hussey James R.
Published: July 2010

This research developed multiple regression models relating land use to in‐stream concentrations of total nitrogen (TOTN) and total phosphorus (TOTP) in eight, low‐order watersheds on the coastal plain of South Carolina. The study area (4860 km2) included dominant land‐use categories of agriculture, forest, urban, and wetland comprising the lower portion of the Lake Marion drainage. Land‐use data were obtained from a pre‐existing GIS database derived by classification of satellite images. The models partitioned land‐use categories according to distance from stream channels using a series of buffer zones around each stream. Effects of point source contributions were removed from observed in‐stream concentrations so that nonpoint source effects could be more clearly delineated. All models except two were significant at P < 0.05. The models for TOTN (r2 from 0.25–0.63) explained more variability of stream nutrient concentrations than those for TOTP (r2 from 0.16–0.39). Greater predictive strength for TOTN than TOTP likely reflects differing pathways from terrestrial to aquatic systems. Land close to the stream channel (<150 m) was better predictor of nutrient concentrations than land away from the channel (>150 m). Land‐use change scenarios (converting forest and wetland to agriculture) support the conclusion that management of stream water quality will be most effective with emphasis on riparian and adjacent lands. Seasonal models were generally significant (P < 0.05) and demonstrate that the seasonal profile of stream nutrient concentrations is dependent on the mosaic of land uses in a specific subbasin.
Sediment Enrichment Mechanisms of Organic Carbon and Phosphorus in a Well‐Aggregated Oxisol
Authors: Wan Y. , El‐Swaify S. A.
Published: July 2010

Mechanisms of organic carbon (OC) and P enrichment in sediment eroded from well‐aggregated soils are not well understood. This study was conducted to examine why OC and extractable P (ext‐P) were enriched in sediment with a well‐aggregated Oxisol. Soil samples presented four field treatments: no fertilization (NF), short‐term P fertilization (STP), long‐term P fertilization (LTP), and organic waste fertilization (OW). Organic C in dry‐sieved aggregates increased with decreasing aggregate size for all treatments, suggesting that OC is preferentially retained in small aggregates and, perhaps, protected from microbial attack. Extractable P concentration changed little with aggregate size for the NF treatment, but increased significantly with decreasing aggregate size for the STP and OW treatments and for liquid‐P incubated NF soil. This difference was attributed to the blockage of interior sorption sites within large aggregates. Breakdown of dry STP and OW aggregates by simulated storms produced fine aggregates that were richer in OC and ext‐P than the original larger ones. Most of the fine aggregates were created in the early phase of rainfall by slaking dry aggregates, and further breakdown by stripping water‐stable aggregates was more difficult and slow. Sediment enrichment observed in eroded sediment was caused by selective transport of P and OC‐rich fine aggregates induced by the effects of aggregation blockage and aggregate breakdown by slaking and stripping. For the LTP treatment, however, ext‐P concentration was independent of aggregate size, indicating that a uniform P distribution in aggregates can be reached given sufficiently long equilibration time.
Patchiness in Groundwater Nitrate Removal in a Riparian Forest
Authors: Gold A. J. , Jacinthe P. A. , Groffman P. M. , Wright W. R. , Puffer R. H.
Published: July 2010

Our ability to identify and manage riparian sites for groundwater nitrate (NO−3) removal is limited by uncertainty surrounding the relative importance of plant uptake vs. microbially mediated removal processes. Microcosm studies often demonstrate negligible transformation rates in the subsoil of riparian forests, even in situations where groundwater well networks showed substantial groundwater NO−3 removal during the winter and a decline in dissolved oxygen (DO) in ambient groundwater moving through the site. We hypothesize that microcosm studies may miss groundwater transformations that occur within microsites, that is, “hotspots” of riparian subsoils. We created mesocosms of large (15 cm diam. × 40 cm length), undisturbed cores from the seasonally saturated zone of poorly drained (PD) and moderately well drained (MWD) sandy soils from a forested riparian area in southern New England. We dosed the mesocosms for 130 d with ambient groundwater amended with NO−3‐N and Br−. Changes in the NO−3‐N/Br− ratios were used to calculate groundwater NO−3‐N removal rates. The PD treatment demonstrated substantial groundwater NO−3‐N removal rates. The PD mesocosms contained patches of dark‐stained material that often surrounded roots in various stages of decay. The dry mass of patches in the PD treatment ranged from 0.07 to 1.4% of the mesocosms. The MWD treatment contained no patches and exhibited no groundwater NO−3‐N removal. Further investigations on the relationships between the extent of subsurface patchiness, water table dynamics and plant characteristics might yield fruitful insights into the management of vegetated riparian zones for groundwater NO−3‐N removal.
Greenhouse Evaluation of Agronomic and Crude Oil‐Phytoremediation Potential among Alfalfa Genotypes
Authors: Wiltse C. C. , Rooney W. L. , Chen Z. , Schwab A. P. , Banks M. K.
Published: July 2010

Phytoremediation is an effective, non‐intrusive, and inexpensive means of remediating soils contaminated with organic chemicals. Different plant species have different remediation capabilities, so intraspecies variation may also exist. If intraspecific variation exists and is heritable, population improvement for performance in and phytoremediation of contaminated soils should be possible. The objectives of this study were (i) to determine if variability exists among alfalfa (Medicago sativa L.) genotypes for agronomic performance in and phytoremediation of crude oil‐contaminated soil and (ii) to determine the effect of contaminated soil on the agronomic performance of alfalfa. In one greenhouse experiment, 20 genotypic clones were transplanted into 20 g kg−1 crude oil‐contaminated soil. After 1 yr, differences existed among genotypes for total forage yield (P < 0.05), maturity at harvest (P < 0.001), plant height (P < 0.01), and phytoremediation potential (P < 0.001). Degradation rates ranged from 33 to 56% among genotypes with 46% for the unvegetated control. Two genotypes had significantly greater degradation rates than that of the unvegetated control. In a second greenhouse experiment, eight genotypes from the previous experiment were compared with their clones in uncontaminated soil. After 1 yr, mean total forage yield in contaminated soil was 32% of the yield of the same clones in uncontaminated soil. Plants in contaminated soil also matured later and were shorter. Genotype variability was present for all traits but not on all evaluation dates. The results indicate that overall agronomic performance is reduced in contaminated soil, but variability exists among genotypes for growth in and phytoremediation of contaminated soils.
Agricultural Phosphorus and Water Quality: A U.S. Environmental Protection Agency Perspective
Authors: Parry Roberta
Published: July 2010

Pollution of lakes, rivers, and estuaries from agricultural sources of P is a major water quality problem in the USA. This paper explains the regulatory and nonregulatory programs developed by the U.S. Environmental Protection Agency (USEPA) to implement its legal mandate to control water pollution from these sources. The Clean Water Act defines concentrated animal feeding operations as point sources of pollution that are required to obtain permits to discharge into waters of the USA. All other agricultural sources are considered nonpoint and are not regulated under federal law. The USEPA prorides grant money to the states to develop and implement nonpoint source programs. The Coastal Zone Act Reauthorization Amendments of 1990 requires coastal states to adopt nonpoint management measures that are backed by enforceable policies and mechanisms. For water bodies that continue to be impaired despite the basic implementation of these laws and other programs, states are required to develop a total maximum daily load (TMDL). The TMDL process is the quantitative basis for reaching water quality standards. The USEPA is putting a new emphasis on controlling nutrient pollution sources to meet the goal of the Clean Water Act.
Modeling Phosphorus Dynamics in Ecosystems: Mass Balance and Dynamic Simulation Approaches
Authors: Cassell E. A. , Dorioz J. M. , Kort R. L. , Hoffmann J. P. , Meals D. W. , Kirschtel D. , Braun D. C.
Published: July 2010

Phosphorus (P) export from agriculture is a major cause of eutrophication in many lake ecosystems. Human activity, hydrology, and physicochemical and biological processes that store, transform, and transport P, define P export patterns over time and space. We suggest that an ecosystem paradigm is useful to holistically view P dynamics within complex watersheds. An ecosystem model of a dairy agricultural system was created within a hierarchical compartment‐flux structure of a conceptual watershed ecosystem. Mass balance calculations with our Agriculture Ecosystem model (AEP model) describe P dynamics for the farm system, which are driven by the amount of P stored in agricultural soils and system management practices. Longterm P dynamics respond predominately to human interventions in watersheds and define conditions for future generations. Model simulations suggest that long‐term environmental protection programs should incorporate the notions of P sustainability into management decisions. Dynamic simulation modeling is a valuable paradigm for understanding how complex watersheds process P and for developing management perspectives and public policy to achieve goals of environmental quality as well as economic and resource sustainability.
Plant Genetic Approaches to Phosphorus Management in Agricultural Production
Authors: Ertl D. S. , Young K. A. , Raboy V.
Published: July 2010

Much of the P in corn (Zea mays L.) grain is present in the form of phytic acid. Phytic acid P is unavailable to monogastric animals with most being excreted in the waste. As a result, the substantial P stores in grain are essentially wasted and may contribute to water pollution rather than animal productivity. The initial goal of this research was to isolate chemically induced mutants with reduced levels of phytic acid P in corn. Such mutants, referred to as low phytic acid or Ipa, were isolated and were found to have little or no other effect on kernel composition including no effect on total grain P content. The first mutant characterized, Ipal‐1, a 65% reduction in phytic acid and is accompanied by a molar‐equivalent increase in inorganic P. This mutant was backcrossed into elite corn inbred lines and resulting hybrids were evaluated for yield and other important agronomic traits. Preliminary field trials indicated germination, stalk strength, grain moisture at harvest, and flowering date were not affected by Ipal‐1. Some, but not all, Ipal‐1 hybrids had yield reductions. In a preliminary chick feeding trial, the low phytic acid grain resulted in greater P availability and reduced P content in the waste. Altering the phytic acid content genetically in corn is possible and may have the potential to improve feeding efficiencies and reduce P released to the environment.
Seasonal and Spatial Patterns of Nitrate and Silica Concentrations in Canajoharie Creek, New York
Authors: Wall G. R. , Phillips P. J. , Riva‐Murray K.
Published: July 2010

The impact of nonpoint‐source pollution on surface waters in agricultural watersheds is an emerging environmental issue. As part of the U.S. Geological Survey National Water Quality Assessment program in the Hudson River Basin, Canajoharie Creek was monitored for seasonal and spatial patterns of nutrient chemistry from March 1993 to January 1996. Nitrate and silica concentrations in Canajoharie Creek suggest that seasonal and spatial variations of these nutrients are dominated by biological processes, particularly uptake by phytoplankton. Observed concentration patterns were more typical of those observed in much larger, low‐gradient streams. The median nitrate and silica concentrations in Canajoharie Creek were significantly lower from April through November than during winter. Concentrations of both constituents declined downstream from the headwaters during base‐flow conditions in June 1995. Groundwater and surface water chemistry data support biological causes for downstream decreases in silica. The strong correlation between nitrate and silica in samples collected along the mainstem suggests that most of the nitrate decrease is due to uptake by diatoms. Downstream patterns of chlorophyll‐a in phytoplankton strongly suggest the conversion of in‐stream nutrients to algal biomass. Data collected from Canajoharie Creek outlet during the northeast drought of 1995 indicate that silica concentrations in May had possibly declined to a level that adversely affected the diatom community. This decline in the diatom population and subsequent resurgence is inferred from a sharp rise in silica concentrations between May and July and a reversal of this trend from mid‐July through October without associated changes in hydrology.
Phosphorus Sorption Capacities of Wetland Soils and Stream Sediments Impacted by Dairy Effluent
Authors: Reddy K. R. , O Connor G. A. , Gale P. M.
Published: July 2010

The ability of stream sediments and adjacent wetlands to retain added P depends on the P sorption capacity and physico‐chemical properties of sediments or wetland soils. The objectives of this study were to: (i) determine the potential P sorption capacities of wetland soils and stream sediments in systems with distinctly different P loadings, and (ii) establish the relationship between P sorption capacity and selected physico‐chemical properties. Batch sorption isotherms were measured under aerobic and anaerobic conditions for sediments and wetland soils along a stream‐wetland‐upland continuum at two sites in the Lower Kissimmee River Basin and Taylor Creek/Nubbin slough of the Okeechobee Basin, Florida. Soluble P and equilibrium P concentrations (EPC) of stream sediments generally decreased along the wetland‐upland continuum. The EPC values were about twofold greater under anaerobic conditions than aerobic conditions; however, P sorption capacities decreased by about 35% under anaerobic conditions compared with aerobic conditions. The P sorption maxima, estimated by a single point isotherm measured at an added P level of 1000 mg P kg−1. correlated well with Langmuir adsorptive maxima. Phosphorus retention by stream sediments and wetland soils was strongly correlated with contents of amorphous and poorly crystalline forms of Fe and Al, which explained 87% of the variability in P retention maximum. Addition of total organic C to predictive equations improved the predictability by only 5%.
Preferential Transport of Phosphorus in Drained Grassland Soils
Authors: Stamm C. , Flühler H. , Gächter R. , Leuenberger J. , Wunderli H.
Published: July 2010

Phosphorus is the limiting factor for primary production in most freshwater ecosystems. In many areas, diffuse P losses from intensively cultivated land cause severe eutrophication of surface waters. We investigated the P export from two drainage systems under intensively used grassland in a catchment of the Swiss Plateau. Flow rate and nutrient concentrations were measured with a high temporal resolution during discharge events. During most flow peaks, P concentrations strongly increased with increasing flow rates. Concentrations of soluble‐reactive P (SRP) reached up to 155 µmol L−1. Phosphorus was mainly transported as soluble‐reactive and particulate P. Organic P compounds, as well as P associated with colloids between 0.05 and 0.45 µm in effective diameter, were of minor importance. Estimated P loads from the drainage systems were 227 g SRP ha−1 within a period of 2.5 mo at site I and 1290 g ha−1 during 6 mo at site II. Estimation uncertainty was large (±21 and ±36% for the two sites, respectively) due to the weak correlation between discharge and concentration for all data from a given site. Water‐extractable P in the soil was concentrated in the uppermost layer of the profiles or, for short periods after spreading of manure, deposited on the vegetation. The discharge‐concentration relationship indicated that P was transported through preferential flow paths extending from close to the surface to the drains. Sprinkling experiments with a blue dye confirmed this conclusion. At one site, we observed preferential flow in a downhill direction within the saturated zone.
Transport and Persistence of Pesticides in Alluvial Soils: II. Carbofuran
Authors: Cogger C. G. , Stark J. D. , Bristow P. R. , Getzin L. W. , Montgomery M.
Published: July 2010

Carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate), a soil‐applied insecticide, is a potential leaching risk when applied to permeable soils overlying shallow, unconfined aquifers. We conducted this project to evaluate the long‐term movement, persistence, and leaching risk of carbofuran applied to perennial small fruit crops grown on alluvial soils with shallow (<3 m deep) groundwater. Carbofuran was applied to strawberry (Fragaria × ananassa Duch.) and red raspberry (Rubus idaeus L.) in paired plots at two sites in western Washington. Strawberry received carbofuran at 2.2 kg ha−1 in a 30‐cm wide band each August, and raspberry received 3.1 kg ha−1 in a 90‐cm band each November. We applied carbofuran yearly from 1986 to 1989, and sampled soil (to 180 cm) and shallow groundwater monthly until April 1991, and at one site again in March 1994. Carbofuran was initially mobile, and significantly more carbofuran moved below 60 cm in raspberry than in strawberry. Differences in carbofuran leaching between sites corresponded to differences in soil‐binding constants. The disappearance half‐life of carbofuran decreased from 110–221 d in 1986–1987 to 69–100 d in 1989–1990, evidence of enhanced degradation. Enhanced degradation appeared to affect freshly added carbofuran, but not residual carbofuran that had become more tightly bound to the soil over time. Carbofuran was found in shallow groundwater beneath both crops and sites the first winter. The leaching risk declined after the first winter, which is probably a result of enhanced degradation and nonequilibrium binding.
Low Molecular Weight Aliphatic Acid Contents of Composted Manures
Authors: Baziramakenga R. , Simard R. R.
Published: July 2010

Composted organic wastes improve nutrient availability by releasing organic compounds, particularly low molecular weight organic acids, which may affect nutrients availability in soils. In this study, composts were collected from different farms and industries across the Quebec Province (Canada). Low molecular weight aliphatic acids (LMWA) were extracted with water or Ca(OH)2, and analyzed by ion chromatography. The main LMWA were acetic, formic, and oxalic acids. Small amounts of lactic, propionic, malic, citric, and aconitic acids were also found. The total amount of water‐soluble LMWA ranged from 5.88 to 69.17 mmol g−1. Compared with fresh manure, the quantities of LMWA decreased with composting time. The volatile aliphatic acids (VAA) accumulated in the early stage of composting while larger amounts of the nonvolatile aliphatic acids (NVAA) were found in the later stages. Turned and uncovered composts contained small amounts of LMWA. High amounts of LMWA were found in compost made with straw or wood residues. Land application of compost may introduce large amounts of LMWA to soils and strongly affect nutrient mobility and plant availability.
Biointrusion of Protective Barriers at Hazardous Waste Sites
Authors: Bowerman Andrew G. , Redent Edward F.
Published: July 2010

At locations throughout the world, hazardous wastes have been buried in an attempt to ensure the health and safety of the environment. The ability of simple and complex barriers to protect against biotic intrusion in the short‐ and long‐term is questionable. Little research has been conducted to assess the risk that biota may pose to barrier integrity. Evidence of documented and potential cases of biointrusion of protective barriers by various species of plants, burrowing mammals, and invertebrates at various hazardous waste sites throughout the USA is examined to assess whether biointrusion has occurred. Studies documenting plant root intrusion were examined to assess their ability to affect barrier integrity. Various plant species, including kochia [Kochia scoparia (L.) Schrader], crested wheatgrass (Agropyron cristatum L.), big sagebrush (Artemisia tridentata ssp. wyomingensis Nutt.), and salt cedar (Tamarix ramosissima Ledeb.) were found to have penetrated into protective barriers in mesic and arid environments. There is also evidence of biointrusion by harvester ants (Pogonomymrmex owyheii) through rock barriers. Mice (Perognathus parvus, Peromyscus maniculatus), kangaroo rats (Dipodyms ordii), pocket gophers (Thomomys bottae), ground squirrels (Spermophilus elegans, S. townsendii), and prairie dogs (Cynomyous leucurus) are also a threat to the integrity of protective barriers. These results indicate that plants, invertebrates, and burrowing mammals pose a threat to barrier integrity and waste isolation. Engineered protective caps have been designed without the consideration of ecological principles and processes. The incorporation of these components into barrier designs may be crucial to their performance.
Physical Properties of Minesoils in West Virginia and Their Influence on Wastewater Treatment
Authors: Skousen J. , Sencindiver J. , Owens K. , Hoover S.
Published: July 2010

Wastewater treatment in southern West Virginia is limited by steep terrain and shallow soil. Surface mine reclamation replaces soil materials that may be suitable for wastewater treatment. Two minesoil series, Kaymine (a loamy‐skeletal, mixed, nonacid, mesic Typic Udorthent) and Sewell (a loamy‐skeletal, mixed, acid, mesic Typic Udorthent), were selected and soil samples were collected on six reclaimed surface mines to determine texture, bulk density, water retention, and saturated hydraulic conductivity (Ksat). Kaymine had more clay and silt and higher moisture retention than Sewell. In A horizons, Kaymine Ksat was about two orders of magnitude faster than Sewell, but Ksat values were highly variable within and among sites. On two reclaimed mine sites (one Sewell and one Kaymine), tapwater or wastewater was surface applied to 9 m2 field plots over 32 wk. Leachate was collected in 50 and 100 cm wells and analyzed for chemical and microbiological properties. On the Sewell minesoil, little water was collected in wells after application, therefore water failed to move adequately in this minesoil. On Kaymine, Fe, Mn, sulfate, and suspended solids were present in all wells, indicating flushing of these materials from minesoils into wells. Nitrate (NO3)‐N was about two times greater in wastewater than tapwater and this same ratio was found in corresponding wells. Biological oxygen demand was decreased by 87% from wastewater to water in wells. Fecal coliform bacteria were not removed by wastewater passing through Kaymine soils. In general, these minesoils are not suitable for wastewater renovation based on the application methods and rates employed in this study.
Nitrate Removal from Groundwater Using a Denitrification Wall Amended with Sawdust: Field Trial
Authors: Schipper Louis , Vojvodić‐Vuković M.
Published: July 2010

Nitrate (NO3) contamination of groundwater can cause pollution of receiving waters. We examined the mechanisms by which a “denitrification wall” removed NO3 from shallow groundwater. The denitrification wall was constructed by digging a trench (35 m long, 1.5 m deep, and 1.5 m wide) that intercepted groundwater. The excavated soil was mixed with sawdust (30% v/v) as a C source then returned to the trench. We assessed NO3 removal and denitrification in the wall for 1 yr. Incoming concentrations of NO3 in groundwater ranged from 5 to 16 mg of N L−1 but these decreased to <2 mg N L−1 in the denitrification wall. Total N in the wall declined during the year demonstrating that N immobilization was not a large sink for NO3. Denitrifying enzyme activity (DEA) reached a maximum of 906 ng of N g−1 h−1 after 6 mo of operation, indicating that denitrification was an important mechanism for NO3 removal. We calculated a maximum rate of NO3 removal by denitrification of 3.6 g N m−3 d−1. Substrate‐amendment experiments showed that denitrification in the wall was primarily limited by NO3 concentration and not C. During the study there was no significant decrease (P < 0.05) in total C but the availability of the remaining C declined. Despite this decrease, the DEA and microbial biomass were stable during the last 6 mo. This study demonstrated that denitrification walls can effectively remove NO3 from groundwater thereby protecting receiving waters.
Nitrous Oxide Emission in Three Years as Affected by Tillage, Corn‐Soybean‐Alfalfa Rotations, and Nitrogen Fertilization
Authors: MacKenzie A. F. , Fan M. X. , Cadrin F.
Published: July 2010

Nitrous oxide (N2O) produced from agricultural activities must be determined if management procedures to reduce emissions are to be established. From 1994 to 1996, N2O emissions were determined using a closed chamber technique. Continuous corn (Zea mays L.) at four N rates of 0, 170, 285, and 400 kg of N ha−1 was used on a Ste. Rosalie heavy clay (a very‐fine‐silty, mixed, nonacid, frigid Typic Humaquept) and a Chicot sandy loam (a fine‐loamy, frigid, Typic Hapludalf). On two additional sites, a Ste. Rosalie clay and an Ormstown silty clay loam (a fine‐silty, mixed, nonacid, frigid Humaquept) no‐till (NT) and conventional tillage (CT); monocultural corn (CCC), monocultural soybean (Glycine max L.) (SSS); corn‐soybean (SSC, CCS); and soybean‐corn‐alfalfa (Medicago sativa L.) phased rotations (SAC, CSA, and ACS) were used. Nitrogen rates of 0, 90, and 180 kg of N ha−1 for corn and 0, 20, and 40 kg of N ha−1 for SSS were used. Rates of N2O emission were measured from April to November in 1994 and 1995, and from mid‐March to mid‐November in 1996. Maximum N2O emissions reached from 120 to 450 ng of N m−2 s−1 at the Ormstown site to 50 to 240 ng of N m−2 s−1 at the Ste. Rosalie soil. Generally, N2O emissions were higher in the NT systems, with corn, and increased linearly with increasing N rates, and amounted to 1.0 to 1.6% of fertilizer N applied. The N2O emission rates were significantly related to soil denitrification rates, water‐filled pore space, and soil NH4 and NO3 concentrations. A corn system using conventional tillage, legumes in rotation, and reduced N fertilizer would decrease N2O emission from agricultural fields.
The Influence of Planting and Soil Characteristics on Mineralization of 2,4,5‐T in Rhizosphere Soil
Authors: Boyle Jay J. , Shann Jodi R.
Published: July 2010

Phytoremediation is a potential means of addressing soil contamination. It is not understood, however, what limits or fosters the degradation of xenobiotics in planted soil. This study examined the relative influence of plant species and soil type on biodegradation in the rhizosphere. In a complete design, three plant species (sunflower, Timothy grass, and red clover) were grown in three field‐collected soils (Jules silt loam [a coarse‐silty, mixed (calcareous), mesic Typic Udifluvent]; Miamian clay loam [a fine, mixed, mesic Typic Hapludalf]; Parke silt loam [a fine‐silty, mixed, mesic Ultic Hapludalf]). Soil characteristics and microbial activity, biomass, and mineralization of 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T), were determined in soil before and after planting. In general, the characteristics of an unplanted soil were correlated to its microbial biomass and activity. Not suprisingly then, soil type was the most significant determinant of xenobiotic degradation in both planted and unplanted systems. In spite of this strong soil effect, planting always resulted in a significant increase in 2,4,5‐T mineralization. The magnitude of this effect varied with soil. The soil initially low in organic matter, K, and P, appeared to gain the most from being planted. The plant species used produced a minor effect, but resulted in significant (mineralization) differences only in higher fertility soils.