bluuebunny/crossref_metadata_2025 huggingface dataset:
Weed Seed Viability in Composted Beef Cattle Feedlot Manure
Authors: Larney Francis J. , Blackshaw Robert E.
Published: June 2010

Manure composting has gained increased acceptance by the beef cattle (Bos taurus) feedlot industry in southern Alberta, Canada. Unlike fresh manure, compost is often promoted as being “weed‐free.” Studies were conducted with five weed species in 1997 and thirteen in 1999 to examine the effect of feedlot manure composting on weed seed viability. Weed seeds were buried in open‐air compost windrows and recovered at various times during the thermophilic phase of composting. Windrow temperature and water contents were also measured. Germinability was zero for all composted weed seeds at all sampling times in 1997. However, some seeds remained viable (positive tetrazolium test denoting respiration) on Day 70. In 1999, only one of the thirteen species retained germinability on Day 21 and only two species had respiring seeds on Day 42. Time–viability relationships during composting were defined by exponential decay models. Lethal temperatures to eliminate viability was species‐dependent. In 1999, four weed species were killed in the initial 7 d of composting at a lethal temperature of 39°C while temperatures of >60°C were required for two species. Regression analysis on weed seed viability versus windrow temperature resulted in significant R2 values, which showed that only 17 to 29% of the variation in viability was accounted for by temperature. The lack of definitive relationships between temperature and weed seed viability demonstrated that factors other than temperature may play a role in eliminating weed seeds during composting.
Mineralization of Soil‐Aged Isoproturon and Isoproturon Metabolites by Sphingomonas sp. Strain SRS2
Authors: Johannesen Helle , S⊘rensen Sebastian R. , Aamand Jens
Published: June 2010

The aim of the study was to determine the effect of aging of the herbicide isoproturon and its metabolites monodesmethyl‐isoproturon and 4‐isopropyl‐aniline in agricultural soil on their availability to the degrading bacterium Sphingomonas sp. strain SRS2. The 14C‐ring‐labeled isoproturon, monodesmethyl‐isoproturon, and 4‐isopropyl‐aniline were added to sterilized soil and stored for 1, 49, 71, or 131 d before inoculation with strain SRS2. The availability of the compounds was estimated from the initial mineralization and the amount of 14CO2 recovered after 120 d of incubation. Aging in soil for 131 d reduced the initial mineralization of isoproturon and monodesmethyl‐isoproturon and, in the case of isoproturon, also reduced the recovery of 14CO2 Initial mineralization and recovery of 14CO2 from aged 4‐isopropyl‐aniline were slightly reduced, but less 14CO2 was generally produced than with isoproturon or monodesmethyl‐isoproturon. Thus, recovery of 14CO2 from 14C‐isoproturon and 14C‐monodesmethyl‐isoproturon was 50.7 to 64.4% of the initially added 14C, while recovery from 14C‐4‐isopropyl‐aniline was only 11.7 to 17.0%. Sorption measurements revealed similar Freundlich constants (Kf) for isoproturon and monodesmethyl‐isoproturon, whereas Kf for 4‐isopropyl‐aniline was more than fivefold greater. The findings imply that in soil, partial degradation of isoproturon to 4‐isopropyl‐aniline may lead to reduced mineralization of the herbicide due to sorption of the aniline moiety.
Comparison of Triticonazole Dissipation after Seed or Soil Treatment
Authors: Börjesson Elisabet , Stenström John , Johnsson Lennart , Torstensson Lennart
Published: June 2010

This study examined the long‐term fate of the fungicide triticonazole (TTZ; 5‐[(4‐chlorophenyl)methylene]‐2,2‐dimethyl‐1‐(1H‐1,2,4‐triazol‐1‐ylmethyl)cyclopentanol) applied at a normal field dose (8.9 g ha−1) via seed treatment, which is the normal alternative in practice. The TTZ was applied to wheat (Triticum aestivum L.) grains as a disinfectant before sowing or spraying on bare soil for comparison and reference to the seed treatment. The seeds were germinated and grown in pots in a greenhouse at 22 ± 3°C. The dissipation of TTZ was studied by gas chromatography–mass spectrometry (GC–MS) analysis of the residues every fourth week until no TTZ could be detected. The recovery for analysis of TTZ in soil was between 98 and 131%, and the quantification level was 0.002 mg kg−1 After 56 d of incubation, 20 and 28% of the TTZ applied remained in the soil and seed treatments, respectively, with corresponding half‐lives of 27 and 29 d. The microbial biomass initially decreased in the soil treatment but had recovered after 56 d. The active part of the biomass was not changed during the experimental time. Thus, with respect to dissipation of TTZ and its effect on the soil microbial biomass and activity, no long‐lasting difference between soil and seed treatments could be found.
Environmental Cadmium Levels Increase Phytochelatin and Glutathione in Lettuce Grown in a Chelator‐Buffered Nutrient Solution
Authors: Maier Elizabeth A. , Matthews Rosalyn D. , McDowell Jennifer A. , Walden Rebecca R. , Ahner Beth A.
Published: June 2010

Phytochelatins are enzymatically synthesized peptides involved in metal detoxification and have been measured in plants grown at very high Cd concentrations, but few studies have examined the response of plants at lower environmentally relevant Cd concentrations. Using an ethylenediaminetetraacetic acid (EDTA)–buffered nutrient medium, we have varied Cd exposure and measured phytochelatin and glutathione concentrations in romaine lettuce (Lactuca sativa L. var. longifolia Lam. var. Parris Island) grown in a flow‐through hydroponic (FTH) system. Very low free ionic Cd (10−9.6 M) increased average phytochelatin concentrations above those of controls, and increasing Cd resulted in increased phytochelatin production, though increases were tissue dependent. Glutathione concentrations also increased with increasing Cd. In other standard hydroponic experiments, the media were manipulated to vary total Cd concentration while the ionic Cd was fixed. We found that the total amount of Cd (primarily EDTA bound) in the medium altered thiol production in roots, whereas thiols in leaves remained constant. The Cd uptake into roots and translocation to old leaves was also influenced by the total concentration in the medium. Cadmium in all tissues was lower and in some tissues thiol concentrations were higher than in FTH‐grown plants grown in identical medium, suggesting that nutrient delivery technique is also an important variable. Though phytochelatin and glutathione production can be sensitive to changes in bioavailable Cd, thiol concentrations will not necessarily reflect the Cd content of the plant tissues.
Phosphorus Runoff Relationships for Louisiana Coastal Plain Soils Amended with Poultry Litter
Authors: Gaston Lewis A. , Drapcho Caye M. , Tapadar Soma , Kovar John L.
Published: June 2010

Long‐term application of poultry (Gallus gallus domesticus) litter has built high levels of P in certain Coastal Plain soils of north Louisiana. However, soil P/runoff P relationships for soil and environmental conditions of the area have not been examined. This study measured soil P (total, Bray 1, Bray 2, Mehlich 3, resin‐exchangeable, and water‐extractable) and runoff P (dissolved P, DP; and total P, TP) at four pasture sites previously amended with poultry litter. Sites varied in soil P due to annual litter applications ranging from 1 to more than 20. Three replicated plots at each site were subjected to simulated rainfalls over 2 yr, and concentrations of DP and TP in runoff were measured and related to soil P. This allowed examination of soil P/runoff P relationships and their changes over time. Runoff DP was also related to DP desorbed from surface soil in a miscible displacement experiment. Among measures of soil P, only resin‐exchangeable and water‐extractable P showed significant decreases over 2 yr. These measures of soil P explained 54 to 64% of the variability in runoff DP data. However, the miscible displacement technique proved the best indicator of runoff DP, explaining 70% of the variability. Runoff varied among sites (decreasing with increasing years of litter application), limiting the predictive capability of the soil extraction methods. Linking runoff characteristics with miscible displacement data may be a useful predictive tool and warrants further examination.
Long‐Term Effects of Clipping and Nitrogen Management in Turfgrass on Soil Organic Carbon and Nitrogen Dynamics
Authors: Qian Y. L. , Bandaranayake W. , Parton W. J. , Mecham B. , Harivandi M. A. , Mosier A. R.
Published: June 2010

Experiments to document the long‐term effects of clipping management on N requirements, soil organic carbon (SOC), and soil organic nitrogen (SON) are difficult and costly and therefore few. The CENTURY ecosystem model offers an opportunity to study long‐term effects of turfgrass clipping management on biomass production, N requirements, SOC and SON, and N leaching through computer simulation. In this study, the model was verified by comparing CENTURY‐predicted Kentucky bluegrass (Poa pratensis L.) clipping yields with field‐measured clipping yields. Long‐term simulations were run for Kentucky bluegrass grown under home lawn conditions on a clay loam soil in Colorado. The model predicted that compared with clipping‐removed management, returning clippings for 10 to 50 yr would increase soil C sequestration by 11 to 25% and nitrogen sequestration by 12 to 28% under a high (150 kg N ha−1 yr−1) nitrogen (N) fertilization regime, and increase soil carbon sequestration by 11 to 59% and N sequestration by 14 to 78% under a low (75 kg N ha−1 yr−1) N fertilization regime. The CENTURY model was further used as a management supporting system to generate optimal N fertilization rates as a function of turfgrass age. Returning grass clippings to the turf–soil ecosystem can reduce N requirements by 25% from 1 to 10 yr after turf establishment, by 33% 11 to 25 yr after establishment, by 50% 25 to 50 yr after establishment, and by 60% thereafter. The CENTURY model shows potential for use as a decision‐supporting tool for maintaining turf quality and minimizing negative environmental impacts.
Manure History and Long‐Term Tillage Effects on Soil Properties and Phosphorus Losses in Runoff
Authors: Andraski Todd W. , Bundy Larry G. , Kilian Kenneth C.
Published: June 2010

Manure additions to cropland can reduce total P losses in runoff on well‐drained soils due to increased infiltration and reduced soil erosion. Surface residue management in subsequent years may influence the long‐term risk of P losses as the manure‐supplied organic matter decomposes. The effects of manure history and long‐term (8‐yr) tillage [chisel plow (CP) and no‐till (NT)] on P levels in runoff in continuous corn (Zea mays L.) were investigated on well‐drained silt loam soils of southern and southwestern Wisconsin. Soil P levels (0–15 cm) increased with the frequency of manure applications and P stratification was greater near the surface (0–5 cm) in NT than CP. In CP, soil test P level was linearly related to dissolved P (24–105 g ha−1) and bioavailable P (64–272 g ha−1) loads in runoff, but not total P (653–1893 g ha−1). In NT, P loads were reduced by an average of 57% for dissolved P, 70% for bioavailable P, and 91% for total P compared with CP. This reduction was due to lower sediment concentrations and/or lower runoff volumes in NT. There was no relationship between soil test P levels and runoff P concentrations or loads in NT. Long‐term manure P applications in excess of P removal by corn in CP systems ultimately increased the potential for greater dissolved and bioavailable P losses in runoff by increasing soil P levels. Maintaining high surface residue cover such as those found in long‐term NT corn production systems can mitigate this risk in addition to reducing sediment and particulate P losses.
Electromagnetic Induction Methods Applied to an Abandoned Manure Handling Site to Determine Nutrient Buildup
Authors: Eigenberg Roger A. , Nienaber John A.
Published: June 2010

Movement of nutrients from livestock manure handling sites has the potential to negatively impact the environment. This study was conducted using electromagnetic induction (EMI) measurements to develop apparent soil electrical conductivity (ECa) maps to identify regions of nutrient buildup beneath an abandoned compost site. A trailer‐mounted EM‐38 coupled with a global positioning satellite system was towed across an area used for composting of feedlot manure. The resulting ECa maps were compared with known locations of compost rows confirming the alignment of row locations with high ECa regions. The identified rows were cored and compared with the region between the rows. The identified rows with a compost history demonstrated significant (P < 0.05) increases in soluble salts (1.6 times greater), NO3 (6.0 times greater), and Cl (2.0 times greater) compared with the area between the rows at a 1.5‐m depth. Image processing techniques were used to display yearly changes that were associated with nutrient movement and transformations in the soil beneath the site. Correlations between EMI measurements and soil core analyses for NO3–N, Cl, and EC provided ancillary support for the EMI methods. The use of EMI for mapping of sites having a history of livestock waste application was effective in delineating high nutrient buildup areas and for observing spatial ECa changes over time.
Nitrogen Management Considerations for Landspreading Municipal Solid Waste Compost
Authors: Wolkowski Richard P.
Published: June 2010

Many municipalities have examined composting as an alternative to landfilling for the management of organic solid waste materials. Ultimately these materials will be land‐applied and therefore some knowledge of nutrient availability will be necessary to optimize crop yield and minimize environmental risk. Field studies were conducted in 1993 and 1994 on a silt loam and a loamy sand soil in Wisconsin to determine the effect of municipal solid waste compost (MSWC) on corn (Zea mays L.) yield, plant nutrient concentration, and soil nitrate N content. Municipal solid waste composts with ages of 7, 36, and 270 d were applied at rates of 22.5, 45, and 90 Mg ha−1 to small plots. Rates of commercial nitrogen (N) fertilizer, ranging from 0 to 179 kg N ha−1, were applied to separate plots to determine the N availability from the MSWC. Treatments were applied in the spring and incorporated before planting corn. The 270‐d MSWC increased corn whole‐plant dry matter and grain yield at each location in both years above the 7‐ and 36‐d MSWC. Rate of MSWC only affected grain yield at the loamy sand site in 1994. Municipal solid waste compost had minimal effect on the levels of plant nutrients in the whole‐plant tissue measured at physiological maturity. Nitrate N measured in the top 90 cm of soil was higher throughout the growing season in treatments receiving recommended N fertilizer when compared with any of the MSWC treatments. It was estimated that 6 to 17% of the total N in the 270‐d MSWC became available in the first year. The land‐application of mature MSWC at the tested rates would be an agronomically and environmentally admissible practice.
Cadmium Availability from Granulated and Bulk‐Blended Phosphate‐Potassium Fertilizers
Authors: Chien S. H. , Carmona G. , Prochnow L. I. , Austin E. R.
Published: June 2010

Recent field experiments have shown that high chloride (Cl) in irrigation waters can increase soil cadmium (Cd) uptake by crops because of the formation of soluble ion‐pair complexes of Cd with Cl in soil solution. The present study was aimed at testing a hypothesis that KCl in granulated PK fertilizers may enhance Cd uptake by crops from Cd‐containing P fertilizers because of close contact between Cd and Cl in the same granules. Less effect would be expected if the same granular PK fertilizers were bulk‐blended because of separation of Cd and Cl in different granules. A single superphosphate (SSP) containing 32 mg Cd kg−1 was granulated by the compaction process with KCl at a P to K ratio = 1:1. Granular KCl was also bulk‐blended with granular SSP or Cd‐free monocalcium phosphate (MCP) at the same P to K ratio. An acid Ultisol (pH 5.2) was treated with PK fertilizers at 400 mg kg−1 each for P and K. Upland rice (Oryza sativa L.) and soybean [Glycine max (L.) Merr.] were grown to maturity, and signalgrass (Brachiaria decumbens Stapf.) was cut four times during the study. The results showed that the agronomic effectiveness in increasing crop yield was the same with SSP and MCP whether granulated or bulk‐blended with KCl. Concentrations of Cd in plant tissue samples of all crops were much lower for MCP than for SSP. In all the plant tissue samples, except grain samples of upland rice, Cd concentrations obtained with granulated (SSP + KCl) were significantly higher than that with bulk‐blended (SSP) + (KCl).
Determination of Polyacrylamide in Soil Waters by Size Exclusion Chromatography
Authors: Lu Jianhang , Wu Laosheng , Gan Jianying
Published: June 2010

Determination of polyacrylamide (PAM) concentration in soil waters is important in improving the efficiency of PAM application and understanding the environmental fate of applied PAM. In this study, concentrations of anionic PAM with high molecular weight in soil waters containing salts and dissolved organic matter (DOM) were determined quantitatively by size exclusion chromatography (SEC) with ultraviolet (UV) absorbance detection. Polyacrylamide was separated from interferential salts and DOM on a polymeric gel column eluted with an aqueous solution of 0.05 M KH2PO4 and then detected at a short UV wavelength of 195 nm. Analysis of PAM concentrations in soil sorption supernatants, soil leachates, and water samples from irrigation furrow streams showed that SEC is an effective approach for quantifying low concentrations (0–10 mg L−1) of PAM in waters containing soil DOM and salts. The method has a lower detection limit of 0.02 μg and a linear response range of 0.2 to 80 mg L−1 Precision studies gave coefficients of variation of <1.96% (n = 4) for >10 mg L−1 PAM and <12% (n = 3) for 0.2 to 3 mg L−1 PAM.
Enhancing Phytoextraction
Authors: Schmidt Ulrich
Published: June 2010

For heavy metal–contaminated agricultural land, low‐cost, plant‐based phytoextraction measures can be a key element for a new land management strategy. When agents are applied into the soil, the solubility of heavy metals and their subsequent accumulation by plants can be increased, and, therefore, phytoextraction enhanced. An overview is given of the state of the art of enhancing heavy metal solubility in soils, increasing the heavy metal accumulation of several high‐biomass‐yielding and metal‐tolerant plants, and the effect of these measures on the risk of heavy metal leaching. Several organic as well as inorganic agents can effectively and specifically increase solubility and, therefore, accumulation of heavy metals by several plant species. Crops like willow (Salix viminalis L.), Indian mustard [Brassica juncea (L.) Czern.], corn (Zea mays L.), and sunflower (Helianthus annuus L.) show high tolerance to heavy metals and are, therefore, to a certain extent able to use the surpluses that originate from soil manipulation. More than 100‐fold increases of lead concentrations in the biomass of crops were reported, when ethylenediaminetetraacetic acid (EDTA) was applied to contaminated soils. Uranium concentrations could be strongly increased when citric acid was applied. Cadmium and zinc concentrations could be enhanced by inorganic agents like elemental sulfur or ammonium sulfate. However, leaching of heavy metals due to increased mobility in soils cannot be excluded. Thus, implementation on the field scale must consider measures to minimize leaching. So, the application of more than 1 g EDTA kg−1 becomes inefficient as lead concentration in crops is not enhanced and leaching rate increases. Moreover, for large‐scale applications, agricultural measures as placement of agents, dosage splitting, the kind and amount of agents applied, and the soil properties are important factors governing plant growth, heavy metal concentrations, and leaching rates. Effective prevention of leaching, breeding of new plant material, and use of the contaminated biomass (e.g., as biofuels) will be crucial for the acceptance and the economic breakthrough of enhanced phytoextraction.
Contribution of Particulate Phosphorus to Runoff Phosphorus Bioavailability
Authors: Uusitalo Risto , Turtola Eila , Puustinen Markku , Paasonen‐Kivekäs Maija , Uusi‐Kämppä Jaana
Published: June 2010

Runoff P associated with eroded soil is partly solubilized in receiving waters and contributes to eutrophication, but the significance of particulate phosphorus (PP) in the eutrophying P load is debatable. We assessed losses of bioavailable P fractions in field runoff from fine‐textured soils (Cryaquepts). Surface runoff at four sites and drainflow at two of them was sampled. In addition to dissolved molybdate‐reactive phosphorus (DRP) losses, two estimates of bioavailable PP losses were made: (i) desorbable PP, assessed by anion exchange resin‐extraction (AER‐PP) and (ii) redox‐sensitive PP, assessed by extraction with bicarbonate and dithionite (BD‐PP). Annual losses of BD‐PP and AER‐PP were derived from the relationships (R2= 0.77–0.96) between PP and these P forms. Losses of BD‐PP in surface runoff (94–1340 g ha−1) were typically threefold to fivefold those of DRP (29–510 kg ha−1) or AER‐PP (13–270 g ha−1). Where monitored, drainflow P losses were substantial, at one of the sites even far greater than those via the surface pathway. Typical runoff DRP concentration at the site with the highest Olsen‐P status (69–82 mg kg−1) was about 10‐fold that at the site with the lowest Olsen P (31–45 mg kg−1), whereas the difference in AER‐PP per mass unit of sediment was only threefold, and that of BD‐PP 2.5‐fold. Bioavailable P losses were greatly influenced by PP runoff, especially so on soils with a moderate P status that produced runoff with a relatively low DRP concentration.
Prediction of Trace Element Mobility in Contaminated Soils by Sequential Extraction
Authors: Pueyo M. , Sastre J. , Hernández E. , Vidal M. , López‐Sánchez J. F. , Rauret G.
Published: June 2010

The modified three‐step sequential extraction procedure proposed by the Community Bureau of Reference (or Bureau Communautaire de Référence, BCR) was used to predict trace element mobility in soils affected by an accidental spill comprising arsenopyrite‐ and heavy metal–enriched sludge particles and acid waste waters. The procedure was used to obtain the distribution of both the major (Al, Ca, Fe, Mg, and Mn) and trace elements (As, Bi, Cd, Cu, Pb, Tl, and Zn) in 13 soils of contrasting properties with various levels of contamination and in the sludge itself. The distributions of the major elements enabled us to confirm the main soil fractions solubilized in each of the three steps, and, in turn, to detect the presence of pyritic sludge particles by the high Fe extractability obtained in the third step. Cadmium was identified as being the most mobile of the elements, having the highest extractability in the first step, followed by Zn and Cu. Lead, Tl, Bi, and As were shown to be poorly mobile or nonmobile. In the case of some of the trace elements, the residual fractions decreased at higher levels of contamination, which was attributed to the anthropogenic contributions to the polluted samples. Comparison with soil–plant transfer factors, calculated in plants growing in the affected area, indicated that a relative sequence of trace element mobility was well predicted from data of the first step.
Temperature and Microbial Activity Effects on Trace Element Leaching from Metalliferous Peats
Authors: Qureshi Shabnam , Richards Brian K. , McBride Murray B. , Baveye Philippe , Steenhuis Tammo S.
Published: June 2010

Due to geochemical processes, peat soils often have elevated concentrations of trace elements, which are gradually released following drainage for agriculture. Our objectives were to use incubation temperatures to vary microbial activity in two metalliferous peats (M7 acidic peat and M3 neutral peat) from the Elba, New York region, and to use periodic leaching to assess the extent of trace element release from these soils. Dried soils were mixed with glass beads to maintain aeration, moistened, and incubated at 4, 16, 28, and 37°C in 10‐cm‐diameter × 8‐cm‐tall columns. Five incubation–leaching cycles were performed, each consisting of 7.3 d of incubation (28 d for the final cycle) followed by 16 h of leaching with synthetic acid rain at 2.5 mm h−1 Microbial activity was determined initially and after the final leaching by measuring C mineralization following glucose stimulation. Cumulative respiration results were ranked 28 > 16 > 4 > 37°C, with M7 acidic peat respiration values greater than M3 neutral peat at each temperature. Initial leachate pH levels were between 2 and 4, with acidification less pronounced and shorter‐lived for the M3 peat. Leachate S, dissolved organic carbon (DOC), NO3–N, and trace elements declined with successive leachings (rebounding slightly in the final M3 leachate), with concentrations typically greater in the M7 leachate. Elemental losses followed the same general ranking (28 > 16 > 4 > 37°C); losses at 28°C were 15 to 22% for As, Cd, Ni, and Zn from the M7 peat; losses from M3 were comparable only for Cu (1%) and Ni (19%). The correlation of respiration with S, DOC, and trace elements losses indicates that microbial processes mediated the release of trace elements in both peat soils. Neutral M3 peat pH levels limited losses of most analytes.
Effect of Rainfall Simulator and Plot Scale on Overland Flow and Phosphorus Transport
Authors: Sharpley Andrew , Kleinman Peter
Published: June 2010

Rainfall simulation experiments are widely used to study erosion and contaminant transport in overland flow. We investigated the use of two rainfall simulators designed to rain on 2‐m‐long (2‐m2) and 10.7‐m‐long (32.6‐m2) plots to estimate overland flow and phosphorus (P) transport in comparison with watershed‐scale data. Simulated rainfall (75 mm h−1) generated more overland flow from 2‐m‐long (20 L m2) than from 10.7‐m‐long (10 L m2) plots established in grass, no‐till corn (Zea mays L.), and recently tilled fields, because a relatively greater area of the smaller plots became saturated (>75% of area) during rainfall compared with large plots (<75% area). Although average concentrations of dissolved reactive phosphorus (DRP) in overland flow were greater from 2‐m‐long (0.50 mg L−1) than 10.7‐m‐long (0.35 mg L−1) plots, the relationship between DRP and Mehlich‐3 soil P (as defined by regression slope) was similar for both plots and for published watershed data (0.0022 for grassed, 0.0036 for no‐till, and 0.0112 for tilled sites). Conversely, sediment, particulate phosphorus (PP), and total phosphorus (TP) concentrations and selective transport of soil fines (<2 μm) were significantly lower from 2‐ than 10.7‐m‐long plots. However, slopes of the logarithmic regression between P enrichment ratio and sediment discharge were similar (0.281–0.301) for 2‐ and 10.7‐m‐long plots, and published watershed data. While concentrations and loads of P change with plot scales, processes governing DRP and PP transport in overland flow are consistent, supporting the limited use of small plots and rainfall simulators to assess the relationship between soil P and overland flow P as a function of soil type and management.
Cotton Defoliant Runoff as a Function of Active Ingredient and Tillage
Authors: Potter Thomas L. , Truman Clint C. , Bosch David D. , Bednarz Craig W.
Published: June 2010

Cotton (Gossypium hirsutum L.) defoliant runoff was recently identified as an ecological risk. However, assessments are not supported by field studies. Runoff potential of three defoliant active ingredients, dimethipin (2,3‐dihydro‐5,6‐dimethyl‐1,4‐dithiin 1,1,4,4‐tetraoxide), thidiazuron (N‐phenyl‐N‐1,2,3‐thidiazol‐5‐yl‐urea), and tribufos (S,S,S‐tributyl phosphorotrithioate) was investigated by rainfall simulation on strip (ST) and conventionally tilled (CT) cotton in south central Georgia. Simulated rainfall timing relative to defoliant application (1 h after) represented an extreme worst‐case scenario; however, weather records indicate that it was not unrealistic for the region. Thidiazuron and tribufos losses were 12 to 15% of applied. Only 2 to 5% of the more water soluble dimethipin was lost. Although ST erosion rates were less, loss of tribufos, a strongly sorbing compound, was not affected. Higher sediment–water partition coefficients (kd) were measured in ST samples. This likely explains why no tillage related differences in loss rates were observed, but it is unknown whether this result can be generalized. The study was conducted in the first year following establishment of tillage treatments at the study site. As soil conditions stabilize, ST impacts may change. Data provide an estimate of the maximum amount of the defoliants that will run off during a single postapplication storm event. Use of these values in place of the default value in runoff simulation models used in pesticide risk assessments will likely improve risk estimate accuracy and enhance evaluation of comparative risk among these active ingredients.
Contrasting Physiological Responses of Dwarf Sea‐Lavender and Marguerite to Simulated Sea Aerosol Deposition
Authors: Sánchez‐Blanco M. J. , Rodríguez P. , Morales M. A. , Torrecillas A.
Published: June 2010

Plants of two wild native species from littoral areas, marguerite [Argyranthemum coronopifolium (Willd.) C.J. Humphries] and dwarf sea‐lavender [Limonium pectinatum (Aiton) O. Kuntze], grown in an unheated plastic greenhouse, were sprayed 2 to 3 min per day over a 7‐d period with different aqueous solutions containing (i) an anionic surfactant (S1); (ii) a solution simulating the composition of sea aerosol (S2); (iii) a solution simulating sea aerosol with anionic surfactant (S3), and (iv) deionized water alone (control). The plant resistance to sea aerosol and the ability to recover from treatments were studied. By the end of the spraying period, marguerite showed a significant reduction in growth compared with control. However, most of the growth parameters were significantly unaffected in dwarf sea‐lavender when plants were treated with sea aerosol containing surfactant. Measurements of water relations variables in marguerite showed a slight decrease in leaf turgor potential after spraying with sea aerosol containing surfactant. The surfactant enhanced the foliar absorption of salt in marguerite plants, inducing reductions in leaf stomatal conductance and causing such damage in the photosynthetic apparatus that the level of net photosynthesis decreased and had not recovered by the end of the experiment. The treatments had no effect on leaf stomatal conductance and photosynthesis rate in dwarf sea‐lavender plants. The response of the species studied to sea aerosol was related to the degree of salinity tolerance. Although both species are wild native plants from littoral areas, marguerite is not salt tolerant and was the most sensitive to the sea aerosol treatments, while dwarf sea‐lavender, a halophyte species, was more efficient at decreasing the toxic salt content of the tissues as its growth and ornamental characteristics were not affected.
Infiltration and Adsorption of Dissolved Atrazine and Atrazine Metabolites in Buffalograss Filter Strips
Authors: Krutz L. J. , Senseman S. A. , Dozier M. C. , Hoffman D. W. , Tierney D. P.
Published: June 2010

Vegetated filter strips (VFS) potentially reduce the off‐site movement of herbicides from adjacent agricultural fields by increasing herbicide mass infiltrated (Minf) and mass adsorbed (Mas) compared with bare field soil. However, there are conflicting reports in the literature concerning the contribution of Mas to the VFS herbicide trapping efficiency (TE). Moreover, no study has evaluated TE among atrazine (6‐chloro‐N‐ethyl‐N′‐isopropyl‐[1,3,5]triazine‐2,4‐diamine) and atrazine metabolites. This study was conducted to compare TE, Minf, and Mas among atrazine, diaminoatrazine (DA, 6‐chloro‐[1,3,5]triazine‐2,4‐diamine), deisopropylatrazine (DIA, 6‐chloro‐N‐ethyl‐[1,3,5]triazine‐2,4‐diamine), desethylatrazine (DEA, 6‐chloro‐N‐isopropyl‐[1,3,5]triazine‐2,4‐diamine), and hydroxyatrazine (HA, 6‐hydroxy‐N‐ethyl‐N′‐isopropyl‐[1,3,5]triazine‐2,4‐diamine) in a buffalograss VFS. Runoff was applied as a point source upslope of a 1‐ × 3‐m microwatershed plot at a rate of 750 L h−1 The point source was fortified at 0.1 μg mL−1 atrazine, DA, DIA, DEA, and HA. After crossing the length of the plot, water samples were collected at 5‐min intervals. Water samples were extracted by solid phase extraction and analyzed by high performance liquid chromatography (HPLC) photodiode array detection. During the 60‐min simulation, TE was significantly greater for atrazine (22.2%) compared with atrazine metabolites (19.0%). Approximately 67 and 33% of the TE was attributed to Minf and Mas, respectively. These results demonstrate that herbicide adsorption to the VFS grass, grass thatch, and/or soil surface is an important retention mechanism, especially under saturated conditions. Values for Mas were significantly higher for atrazine compared with atrazine's metabolites. The Mas data indicate that atrazine was preferentially retained by the VFS grass, grass thatch, and/or soil surface compared with atrazine's metabolites.
Modeling Macropore Flow Effects on Pesticide Leaching
Authors: Roulier Stéphanie , Jarvis Nicholas
Published: June 2010

Macropore flow is a key factor determining pesticide fate, but models accounting for this process need parameters that cannot be easily measured. This study was conducted to investigate the use of inverse techniques to estimate parameters controlling macropore flow and pesticide fate in the dual‐permeability model MACRO. Undisturbed columns were sampled at three landscape positions (hilltop, slope, hollow) with contrasting texture and organic carbon content. Transient leaching experiments were performed for an anionic tracer and the herbicide MCPA (4‐chloro‐2methylphenoxy acetic acid) during a 4‐mo period, first under natural rainfall, and then under controlled irrigation in the laboratory. The tracer breakthrough for the finer‐textured soil from the hilltop showed strong evidence of macropore flow, resulting in a rapid leaching of MCPA, while leaching was minimal from the organic‐rich hollow soil, since macropore flow was weaker and adsorption stronger. The MACRO model was linked to the inverse modeling program SUFI (Sequential Uncertainty Fitting) to enable calibration of nine key model parameters. Based on calculated model efficiencies, MACRO–SUFI gave generally good predictions of water movement and tracer and pesticide transport, although some errors were attributed to difficulties in simulating the effects of soil moisture on degradation and the timing of water outflows. Even after calibration, significant uncertainties remained for some key parameters controlling macropore flow. Nevertheless, the parameter estimates were significantly different between landscape positions and could also be related to basic soil properties. The posterior uncertainty ranges could probably be reduced with a more exhaustive sampling of the parameter space and improved experimental designs.
Effect of Peroxide on Neutralization‐Potential Values of Siderite and Other Carbonate Minerals
Authors: Jambor J. L. , Dutrizac J. E. , Raudsepp M. , Groat L. A.
Published: June 2010

To assess quantitatively the effect of peroxide addition to standard static tests of the neutralization potential (NP) of mine wastes, 10 specimens of carbonate minerals, including five of siderite (FeCO3) and two of rhodochrosite (MnCO3), were analyzed by electron microprobe. The compositions of the siderite span a range from 60 to 86 mol % Fe. Tests of NP for the siderite diluted with 80% (w/w) kaolinite gave values of 647 to 737 kg CaCO3 equivalent per Mg for determinations by the standard Sobek method. However, if it is assumed that the ferrous carbonate component of the mineral does not contribute to NP in field situations because oxidation of Fe(II) to Fe(III) and the subsequent hydrolysis of Fe(III) leads to the release of an equivalent amount of acid, then the calculated NP for the samples ranges from 110 to 390 kg CaCO3 equivalent per Mg. Two different methods involving the addition of peroxide to the test solutions were successful in bringing the measured NP values closer to the theoretical ones. By contrast, the tests with rhodochrosite indicated the Mn(II) to be stable. For long‐term environmental planning, especially for wastes from metalliferous sulfide‐poor deposits in which gradual dissolution of silicate and aluminosilicate minerals may be involved in attenuating the acidity, consideration in the overall NP budget needs to be given to the ferrous iron content of those minerals. The presence of Fe2+–bearing minerals, especially carbonates, in tested mine‐waste materials may lead to overestimated Sobek NP values, thus increasing the risk of poor‐quality drainage and the need for costly remediation.
Effects of Static vs. Tidal Hydrology on Pollutant Transformation in Wetland Sediments
Authors: Catallo W. James , Junk Thomas
Published: June 2010

This work addressed effects of hydrology on biogeochemical processes relevant to pollutant chemical transformation in wetland sediments. Microcosms were designed to impose three hydrologic conditions on salt marsh sediments: (i) drained–oxidized redox potenial (Eh); (ii) flooded–reduced Eh and, (iii) diurnal tide–oscillating Eh. The test chemicals were N‐ and/or S‐heterocycles (NSHs) including quinoxaline (1,4‐benzodiazine), 2‐methylquinoxaline(2‐methyl‐1,4‐benzodiazine), 2,3‐dimethylquinoxalinen (2,3‐dimethyl‐1,4,benzodiazine), phenazine (2,3,5,6‐dibenzo‐1,4‐diazine), acridine (2,3,5,6‐dibenzopyridine), dibenzothiophene (2,3,5‐dibenzothiophene), phenothiazine (dibenzo‐1,4‐thiazine), and phenanthridine (2,3‐benzoisoquinoline). Biogeochemical processes reflected the hydrologic conditions in ways analogous to field settings, e.g., Eh characteristics were drastically different: static (flooded and drained) systems had reduced (μ = −428 mV ± 57) and oxidized (μ = +73 mV ± 32) values, respectively, with no evidence of periodic variation while the tidal systems exhibited regularly oscillating Eh (amplitudes 40–250 mV). Sediment trace gases also corresponded to the Eh, with the major species detected being CO2 and H2O (drained, tidal) vs. CO2 + H2O + sulfides + methane (flooded). The NSH transformation rates were different in each hydrologic regime and decreased as follows: tidal ≥ drained ≫ flooded. These results indicated that there were subtle differences in NSH processing in drained and tidal systems, but both of these systems transformed NSHs faster and to lower levels than flooded sediments. These data suggest that in situ remediation options that preserve wetland integrity and tidal hydrology can be as or more effective than static conditions that obtain in approaches such as impoundment and excavation–upland placement.
Nitrification and Denitrification Rates of Everglades Wetland Soils along a Phosphorus‐Impacted Gradient
Authors: White John R. , Reddy K. R.
Published: June 2010

Little information is available on the effect of phosphorus (P) enrichment on nitrogen (N) biogeochemical cycling in wetland soil. Of particular importance are the coupled nitrification–denitrification reactions that regulate the microbially mediated loss of N from wetland systems. Soils from the northern Florida Everglades have been affected by P loading from surface waters over the past 40 years. Elevated P levels have been show to have an effect on the size and activity of the microbial pool and a decrease in the N to P ratio of the microbial biomass. The objective of the study was to determine if P enrichment in soils affected microbial activities related to nitrification and denitrification in these flooded, peat soils. Potential nitrification rates of soil and detritus were determined using constantly stirred reactors under aerobic conditions while denitrification rates were determined from anaerobic incubations of slurry. Nitrification rates showed two distinct linear phases, a slower initial rate, signifying activity of nitrifiers present, followed by a sharp increase in the NH4+conversion rate indicative of maximum potential rates. Initial rates of nitrification were highest in the surficial detrital layer decreasing with soil depth and did not correlate to soil total P. The potential rates of nitrification were 13 times greater than the initial rates. Potential denitrification rates were highest in the detritus and 0‐ to 10‐cm soil interval with significantly lower values in the 10‐ to 30‐cm soil interval, significantly correlated to total P of the soil. A significant (P< 0.01) relationship was seen between potential denitrification rates and soil total P suggesting an increased rate of N removal from P‐enriched regions of the northern Everglades.
Ammonia Volatilization from Marsh–Pond–Marsh Constructed Wetlands Treating Swine Wastewater
Authors: Poach M. E. , Hunt P. G. , Reddy G. B. , Stone K. C. , Matheny T. A. , Johnson M. H. , Sadler E. J.
Published: June 2010

Ammonia (NH3) volatilization is an undesirable mechanism for the removal of nitrogen (N) from wastewater treatment wetlands. To minimize the potential for NH3 volatilization, it is important to determine how wetland design affects NH3 volatilization. The objective of this research was to determine how the presence of a pond section affects NH3 volatilization from constructed wetlands treating wastewater from a confined swine operation. Wastewater was added at different N loads to six constructed wetlands of the marsh–pond–marsh design that were located in Greensboro, North Carolina, USA. A large enclosure was used to measure NH3 volatilization from the marsh and pond sections of each wetland in July and August of 2001. Ammonia volatilized from marsh and pond sections at rates ranging from 5 to 102 mg NH3–N m−2 h−1 Pond sections exhibited a significantly greater increase in the rate of NH3 volatilization (p < 0.0001) than did either marsh section as N load increased. At N loads greater than 15 kg ha−1 d−1, NH3 volatilization accounted for 23 to 36% of the N load. Furthermore, NH3 volatilization was the dominant (54–79%) N removal mechanism at N loads greater than 15 kg ha−1 d−1 Without the pond sections, NH3 volatilization would have been a minor contributor (less than 12%) to the N balance of these wetlands. To minimize NH3 volatilization, continuous marsh systems should be preferred over marsh–pond–marsh systems for the treatment of wastewater from confined animal operations.
Biodegradation of Polycyclic Aromatic Hydrocarbons in Oil‐Contaminated Beach Sediments Treated with Nutrient Amendments
Authors: Xu Ran , Obbard Jeffrey P.
Published: June 2010

Microbial biodegradation of polycyclic aromatic hydrocarbons (PAHs) during the process of bioremediation can be constrained by lack of nutrients, low bioavailability of the contaminants, or scarcity of PAH‐biodegrading microorganisms. This study focused on addressing the limitation of nutrient availability for PAH biodegradation in oil‐contaminated beach sediments. In our previous study, three nutrient sources including inorganic soluble nutrients, the slow‐release fertilizer Osmocote (Os; Scotts, Marysville, OH) and Inipol EAP‐22 (Ip; ATOFINA Chemicals, Philadelphia, PA), as well as their combinations, were applied to beach sediments contaminated with an Arabian light crude oil. Osmocote was the most effective nutrient source for aliphatic biodegradation. This study presents data on PAH biodegradation in the oil‐spiked beach sediments amended with the three nutrients. Biodegradation of total target PAHs (two‐ to six‐ring) in all treatments followed a first‐order biodegradation model. The biodegradation rates of total target PAHs in the sediments treated with Os were significantly higher than those without. On Day 45, approximately 9.3% of total target PAHs remained in the sediments amended with Os alone, significantly lower than the 54.2 to 58.0% remaining in sediment treatments without Os. Amendment with Inipol or soluble nutrients alone, or in combination, did not stimulate biodegradation rates of PAHs with a ring number higher than 2. The slow‐release fertilizer (Os) is therefore recommended as an effective nutrient amendment for intrinsic biodegradation of PAHs in oil‐contaminated beach sediments.
Adsorption and Desorption of Metolachlor and Metolachlor Metabolites in Vegetated Filter Strip and Cultivated Soil
Authors: Krutz L. J. , Senseman S. A. , McInnes K. J. , Hoffman D. W. , Tierney D. P.
Published: June 2010

Previous studies have indicated that dissolved‐phase metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(methoxy‐1‐methylethyl)acetamide] transported in surface runoff is retained by vegetative filter strips to a greater degree than either metolachlor oxanilic acid [2‐[(2‐ethyl‐6‐methylphenyl)(2‐methoxy‐1‐methylethyl)amino]‐2‐oxoacetic acid] (OA) or metolachlor ethanesulfonic acid [2‐[(2‐ethyl‐6‐methylphenyl)(2‐methoxy‐1‐methylethyl‐1)amino]‐2‐oxoethanesulfonic acid] (ESA), two primary metabolites of metolachlor. Adsorption–desorption of ESA and OA in vegetated filter strip soil (VFSS) has not been evaluated, yet these data are required to assess the mobility of these compounds in VFSS. The objective of this experiment was to compare metolachlor, ESA, and OA adsorption and desorption parameters between VFSS and cultivated soil (CS). Adsorption and desorption isotherms were determined using the batch equilibrium procedure. With the exception of a 1.7‐fold increase in organic carbon content in the VFSS, the evaluated chemical and physical properties of the soils were similar. Sorption coefficients for metolachlor were 88% higher in VFSS than in CS. In contrast, sorption coefficients for ESA and OA were not different between soils. Relative to metolachlor, sorption coefficients for ESA and OA were at least 79% lower in both soils. Metolachlor desorption coefficients were 59% higher in the VFSS than in the CS. Desorption coefficients for ESA and OA were not different between soils. Relative to metolachlor, desorption coefficients for ESA and OA were at least 66% lower in both soils. These data indicate that the mobility of ESA and OA will be greater than metolachlor in both soils. However, higher organic carbon content in VFSS relative to CS may limit the subsequent transport of metolachlor from the vegetated filter strip.
Cover Cropping to Reduce Nitrate Loss through Subsurface Drainage in the Northern U.S. Corn Belt
Authors: Strock J. S. , Porter P. M. , Russelle M. P.
Published: June 2010

Despite the use of best management practices for nitrogen (N) application rate and timing, significant losses of nitrate nitrogen NO−3–N in drainage discharge continue to occur from row crop cropping systems. Our objective was to determine whether a autumn‐seeded winter rye (Secale cereale L.) cover crop following corn (Zea mays L.) would reduce NO−3–N losses through subsurface tile drainage in a corn–soybean [Glycine max (L.) Merr.] cropping system in the northern Corn Belt (USA) in a moderately well‐drained soil. Both phases of the corn–soybean rotation, with and without the winter rye cover crop following corn, were established in 1998 in a Normania clay loam (fine‐loamy, mixed, mesic Aquic Haplustoll) soil at Lamberton, MN. Cover cropping did not affect subsequent soybean yield, but reduced drainage discharge, flow‐weighted mean nitrate concentration (FWMNC), and NO−3–N loss relative to winter fallow, although the magnitude of the effect varied considerably with annual precipitation. Three‐year average drainage discharge was lower with a winter rye cover crop than without (p = 0.06). Over three years, subsurface tile‐drainage discharge was reduced 11% and NO−3–N loss was reduced 13% for a corn–soybean cropping system with a rye cover crop following corn than with no rye cover crop. We estimate that establishment of a winter rye cover crop after corn will be successful in one of four years in southwestern Minnesota. Cover cropping with rye has the potential to be an effective management tool for reducing NO−3–N loss from subsurface drainage discharge despite challenges to establishment and spring growth in the north‐central USA.