bluuebunny/crossref_metadata_2025 huggingface dataset:
Movement of Pesticides under Two Irrigation Regimes Applied to Turfgrass
Authors: Starrett S. K. , Christians N. E. , Austin T. Al
Published: July 2010

Current public concern has focused attention on the environmental effects of chemical applications to turfgrass areas. Our objective was to investigate the movement of isazofos ([O‐[5‐chloro‐1‐(1‐methylethyl)‐1H‐1,2,4‐triazol‐3‐yl]O,O‐diethyl phosphorothioate]), chlorpyrifos ([0,0‐diethyl‐0‐(3,5,6‐trichloro‐2‐pyridinyl) phosphorothioate]), metalaxyl [N‐(2,6‐dimethylphenyl)‐N‐(methoxyacetyl) alanine methyl ester], and pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine] when applied to Kentucky bluegrass turf established on 50‐cm long and 20‐cm diameter undisturbed soil columns of Nicollet (fine‐loamy, mixed, mesic Aquic Hapludolls) in which the macropore system remained intact. This study was conducted for 28 d and used a heavy (four, 2.54‐cm applications) and a light (16, 0.64‐cm applications) irrigation regime. Average isazofos, chlorpyrifos, metalaxyl, and pendimethalin recovered (by extraction) from soil columns under the heavy irrigation regime, plus that collected in the leachate, were 8.8, 11.5, 23.8, and 7.9%, respectively. Isazofos, chlorpyrifos, metalaxyl, and pendimethalin recovery from soil columns under the light irrigation regime, plus that collected in the leachate, averaged 3.4, 6.6, 13.9, and 4.6%, respectively. On average, 6.3, 0.5, 7.7, and 0.2% of the applied isazofos, chlorpyrifos, metalaxyl, and pendimethalin, respectively, were measured in leachate from soil columns under heavy irrigation in contrast to 0.4, 0.0, 0.2, and 0.0%, respectively, from soil columns under light irrigation. Comparing the four applied pesticides, metalaxyl is most likely to be leached because of a low soil sorption, followed by isazofos, pendimethalin, and chlorpyrifos. Metalaxyl was found in the highest percentage in the leachate followed by isazofos, pendimethalin, and chlorpyrifos. From this research, we conclude that irrigation practices (frequency and depth of application) can have an impact on the movement of pesticides through soil profiles.
Side Effects of Rimsulfuron on the Microbial Biomass of a Clay‐Loam Soil
Authors: Perucci P. , Scarponi L.
Published: July 2010

The effect of Rimsulfuron treatment on soil microbial biomass was studied in a clay‐loam soil under field and laboratory conditions. Field trials were performed at the usual field rate (0.005 ppm; FR) and 10 times the field rate (10FR). In addition to FR and 10FR, one hundred (100FR) times the field rate was also assayed in laboratory experiments. Determinations of microbial biomass‐C content, fluorescein diacetatehydrolysis activity (FDA hydrolysis) and protease activity were carried out 0, 1, 2, 4, 7, 10, 15, 25, and 45 d after herbicide application. In the field trials there were no significant side effects on the investigated parameters at either rate. Conversely, laboratory experiments showed decreases in microbial biomass‐C levels and increases in FDA‐hydrolysis and protease activity at 10FR and 100FR within the first 10 d. As increases in the activity of FDA hydrolysis and protease were concomitant with the decreases in the microbial biomass‐C content a toxic effect on soil microrganisms with a consequent release of hydrolytic enzymes from cell lysis has been hypothesized. This effect was transitory and only at the higher rates of rimsulfuron was it significant.
Soil Response to Acid Percolation: Acid‐Base Buffering and Cation Leaching
Authors: Hartikainen Helinä
Published: July 2010

A gradual soil acidification was simulated in a percolation experiment with two cultivated soils differing markedly in their initial pH. Soil samples were repeatedly eluted with water or 0.002 M H2SO4, and the changes in the eluate and soil chemistry at various stages of soil acidification were monitored. Ion exchange properties responded to acid load more readily than did the eluate chemistry. Cation exchange at variable charge sites and dissolution reactions releasing from the nonexchangeable pool were important mechanisms consuming solution H+ ions. Alkali and alkaline earth saturation degree that was related to the potential cation exchange capacity (AAESpot) decreased in conformity with acid load, whereas that related to the effective cation exchange capacity (AAESeff) did not. In terms of eluate chemistry, two stages of acidification were identified in a circumneutral acid Podzol (CaCl2, pH 6.7). In the first stage, acidification proceeded with small changes in pH as long as buffering by variable charge exchange sites was available (above soil pH 5). In the second stage, percolate pH dropped drastically and the leaching of Al, Fe, and Mn was intensified because of a marked increase in their exchangeable pool. An acid Gleysol (pH 4.9) showed only the feature of the second stage of acidification. The acid‐induced losses of cations in the percolation were markedly lower than in a previous titration experiment. Magnesium was more sensitive to acid than Ca. The monovalent cations were only slightly affected. Response of Mn to acid was similar to the alkaline earth cations, whereas Al was not substantially displaced. Above pH 4.7, complexation by humus reduced the leaching of Al, but below this pH complexed Al began to decrease.
Effects of Initial Water Content on Macropore/Matrix Flow and Transport of Surface‐Applied Chemicals
Authors: Shipitalo M. J. , Edwards W. M.
Published: July 2010

Pesticides and fertilizers are often broadcast on no‐till fields in the spring when soil water content can be quite variable. Soil water content may influence the contribution of macropores and matrix porosity to water movement and chemical transport in subsequent rainfalls. Therefore, we surface‐applied SrBr2 6H2O, atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine), and alachlor [2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl) acetanilide] on nine, 30 by 30 by 30 cm, undisturbed soil blocks obtained from a no‐till corn (Zea mays L.) field and maintained at three initial moisture levels 1 h before a 30‐mm, 0.5‐h simulated rain. To distinguish applied water from resident water and assess interaction of the rainwater with the soil matrix, RbCl was added to the simulated rain as a tracer. Sequential percolate samples were collected from the base of the blocks in ≈ 10‐mL increments using a 64‐cell grid lysimeter. Flow‐weighted concentrations of Cl− and Rb+, respectively, were 75 and 836% higher in percolate from dry (θ = 0.11 kg kg−1) than from wet blocks (θ = 0.21 kg kg−1), indicating that displacement of resident water and interaction of rainwater with the matrix increased with initial soil water content. As a result, percolate concentrations of the reactive, surface‐applied, constituents (Sr2+, atrazine, alachlor) decreased with increasing soil water content. High block to block variability precluded detection of significant differences in percolate volume and total chemical transport among moisture levels. The relative contribution of macropores to chemical transport and water movement appears to be greatest when the soil is dry and decreases as the soil becomes wetter.
Fate and Transport of Plutonium‐239 + 240 and Americium‐241 in the Soil of Rocky Flats, Colorado
Authors: Litaor M. Iggy , Barth G. R. , Zika E. M.
Published: July 2010

Actinides contamination of soils around Rocky Flats, CO, resulted from leaking drums of Pu‐contaminated oil stored at an outdoor site. The transport of these actinides through the soil to groundwater was studied using an advanced monitoring system (MS). The fully automated, remotely controlled MS gathered real‐time data on soil water content, groundwater level, and timing of gravitationally flowing water. Controlled rain simulations coupled with measurements of volume flux and actinide activities provided essential information about the fate and transport of Pu‐239 + 240 and Am‐241. Volume fluxes at most sampling locations were similar, regardless of the antecedent moisture or the duration, frequency, and intensity of the simulated rain. Actinide activities were not correlated with the measured volume flux, or the duration, frequency, and intensity of the simulated rain. Flow was facilitated primarily via macropore channeling. The relatively short residence time precluded a continuous interaction between the soil and the flowing water, which minimized the movement of actinides in the soil. Actinide activities in the interstitial water collected from the upper 20 cm of the soil were significantly higher (P > 0.001) than water collected at deeper sampling depths (20–70 cm). Actinide activity in water samples from the deepest sampling depth (40–70 cm) did not exceed 0.4 Bq/L. These results suggest that, under the experimental conditions, the movement of actinides was restricted to the top 20 cm. A transport mechanism involving discrete Pu oxide particles, coupled with macropore channeling is proposed to explain the observed actinide activities in the soil.
Predicting Long‐Term Decomposition of Biosolids with a Seven‐Day Test
Authors: Gilmour John T. , Clark Mark D. , Daniel Sharon M.
Published: July 2010

Decomposition of biosolids (municipal sewage sludge) in soil has been characterized by long‐term (>60 d) studies. This study was conducted to determine if short‐term incubations could be used to estimate long‐term decomposition behavior. Twenty‐four biosolid/soil combinations were incubated at 25°C for a period of about 60 d. Decomposition followed first order kinetics with two fractions, rapid and slow, based on decomposability. The percentage of biosolid C in the rapid fraction (%Rapid), and the rapid and slow fraction rate constants (kr and ks, respectively) were determined using linear regression of log transformed data (sequential decomposition model) and nonlinear regression of the original data (simultaneous decomposition model). Both models adequately estimated the %Rapid, kr, and ks. The sequential model provided the best relationship between %Rapid and the percent decomposition at 7 d, %D7, and the only relationship between kr and %Rapid. The slow fraction rate constants in this study were compared to those estimated using data from other studies. The slow fraction rate constant used in prediction of long‐term decomposition was from one of these other studies. Predictions of long‐term decomposition agreed well with observed values (r2 = 0.76). It is proposed that a single measurement, %D7, could be used to assess long‐term decomposition for biosolids similar to those reported here. The equation should not be applied to biosolids with small rapid fractions (<10%) such as those stored for extended periods or composted or to biosolids not originating from municipalities.
Phosphorus Mobility in Calcareous Soils under Heavy Manuring
Authors: James D. W. , Kotuby‐Amacher J. , Anderson G. L. , Huber D. A.
Published: July 2010

Confined animal production systems produce large amounts of manure that are usually disposed on limited land areas in proximity to the source. There is concern that continuous heavy manuring may saturate the soil's capacity to retain manure‐P and result in groundwater contamination with excessive P. The objectives of this research were to determine the fate of waste‐P in heavily manured soils and assess the risk of soil and water quality degradation in turkey (Meleagris gallopavo) and beef (Bos taurus) feed lot production areas. All soils were calcareous throughout the profile. Samples were collected by 30‐cm depth increments to a depth of 210 cm or a limiting layer and were analyzed for NaHCO3‐extractable P (including inorganic and organic), and total soil P. Large amounts of extractable organic P in the surface soil layers decreased to background levels within 2 to 3 yr after manuring ceased. In heavily manured fields extractable inorganic P was well above background concentrations to as deep as 210 cm, apparently because of movement and subsequent mineralization of organic P. Organic matter in these soils was about twofold higher than background levels. There appeared to be no practical limit to the P‐retention ability of these calcareous soils. Under these conditions the risk of groundwater contamination by organic or inorganic P from waste P disposal to land is negligible.
Land Treatment of Oil‐Based Drill Cuttings in an Agricultural Soil
Authors: Chaîneau C. H. , Morel J. L. , Oudot J.
Published: July 2010

The biodegradation, mobility, and phytotoxicity of fuel oil hydrocarbons (HC) contained in drill cuttings (DC) were investigated in a 28‐mo field experiment. In an agricultural soil, three plots were treated with DC on an extensive basis: 15, 30, and 60 Mg DC ha−1 corresponding to 1.5, 3, and 6 Mg HC ha−1. Concentration and chemical composition of residual HC in the soil profile (0–80 cm) were periodically determined. The decrease in HC concentration was proportional to the loading rates and mainly due to microbial biodegradation. Gas chromatographic analyses demonstrated the metabolism of n− and branched alkanes and of GC‐resolved aromatics. The persistence of some polycyclic saturates and aromatics was shown. At the end of the experiment, 10% of the initial HC amount persisted in the surface soil. A vertical selective migration of the lightest HC was shown during the first days and a low leaching of HC and metabolic byproducts toward the subsurface soil and drainage water occurred. The soil treatment modified the soil fertility: pH and Ca increased due to drill cuttings addition while P2O5 and K2O decreased. Crops (maize [Zea mays L.], wheat [Triticum aestivum L.], pea [Pisum sativum L.]) were successively cultivated and harvested. Phytotoxicity, resulting in significant reductions of yields was observed on the two first crops on the most heavily treated plots, but no uptake of HC in the seeds was measured.
Land Application of Wood‐Fired and Combination Boiler Ashes: An Overview
Authors: Vance Eric D.
Published: July 2010

Ashes from the burning of wood and other plant‐derived materials have been used as soil amendments for centuries. Although historical interest in land application of ashes declined following the advent of commercial fertilizers and alternative liming materials, additional incentives for this beneficial use have arisen in recent years. The first is from rapidly rising landfill costs for disposal of by‐product ashes produced from the paper and electric utility industries. Secondly, the environmental ethic of sustainable management and the concept of recycling have provided incentives to replace nutrients removed from forest and agronomic harvests. Field and greenhouse studies show that wood‐fired boiler ashes can be successfully used as a replacement for agricultural lime with additional nutrient benefits. Ash application on forest land is less common, but Scandinavian studies indicate that ashes can enhance long‐term productivity of some forested sites. The use of ashes alone or combined with other mill residues, fertilizers, or agricultural wastes could prove particularly valuable for sustaining productivity of intensively managed forests over successive rotations. This overview provides an introduction to a subset of papers presented at the “NCASI Symposium on Land Application of Wood‐Fired and Combination Boiler Ashes.”
Forest Soil and Water Chemistry following Bark Boiler Bottom Ash Application
Authors: Williams Thomas M. , Hollis Charles A. , Smith Bill R.
Published: July 2010

Ash from the bark‐fueled power boiler at International Paper's Georgetown mill was applied in a column study and a field trial to test land application. Tested application rates were 11, 22, and 44 Mg/ha of ash per rotation. The soil column study found a flush of cations, primarily K and Ca, with the initial 76 cm of 10−5 M oxalic acid leachate. Soils collected after field applications also had higher concentrations of exchangeable K and Ca in the surface soil. Concentrations were disproportionately larger with higher rates. There was little change in concentrations at 45‐cm depths and surface soils returned to near control levels on all sites, except those with the highest rate, within 60 wk. Groundwater samples showed very small differences that were only significant and consistent for Ca, K, and SO4. Heavy metal levels were near detection levels throughout the study. None of the application rates had an effect on groundwater that would compromise drinking water standards. Bark boiler ash, at application rates tested, appears to be safe on moderately well‐drained Atlantic Coastal Plain soils. The soil changes observed suggest ash application could be used to partially replace cations removed during harvest of short rotation pine plantations.
Paired Watershed Comparison of Tillage Effects on Runoff, Sediment, and Pesticide Losses
Authors: Clausen J. C. , Jokela W. E. , Potter F. I. , Williams J. W.
Published: July 2010

A paired watershed study was used to compare runoff, sediment, atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5 triazine), and cyanazine (2‐[[4‐chloro‐6‐(ethylamino)‐S‐triazin‐2‐yl]amino]‐2‐methyl propionitrile) losses from conventional‐tilled (CT) and reduced‐tilled (RT) corn (Zea mays L.) watersheds. During a 13‐mo calibration period both watersheds were moldboard plowed and runoff was measured in H‐flumes. Composite samples were analyzed for sediment and for atrazine and cyanazine in dissolved and sediment phases. During a 30‐mo treatment period, one watershed was moldboard plowed while the other was disk harrowed. Reduced tillage decreased runoff by 64% and sediment losses by 99% but did not change dissolved atrazine or cyanazine concentrations in runoff. Concentrations of sediment‐sorbed pesticides increased in runoff. The RT reduced mass losses of atrazine and cyanazine in runoff, primarily because of decreases in runoff volume and sediment mass. Most pesticide losses occurred within 3 wk of field application. Pesticide loss was primarily in the dissolved phase. The paired watershed approach was a useful technique for determining watershed treatment effects when differences existed between watersheds chosen for study.
Degradation of Atrazine in Two Soils as a Function of Concentration
Authors: Gan J. , Becker R. L. , Koskinen W. C. , Buhler D. D.
Published: July 2010

Dissipation of atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) in a Webster clay loam soil (fine loamy, mixed, mesic Typic Haplaquoll), and Estherville sandy loam (sandy, mixed, mesic typic Hapludoll) was determined over a concentration range of 5 to 5000 mg kg−1 in field and laboratory experiments. Over the first 6 mo in the clay loam soil, the persistence of atrazine (based on percent of applied) was greater for the high‐rate treatments than the low‐rate treatments. However, in the laboratory, there was no effect of concentration on dissipation; the amount of atrazine degraded increased proportionally with the increase of concentration. In the sandy loam, persistence was greater at high concentration in both field and laboratory studies. Mineralization was the most important pathway for the dissipation of atrazine at all concentrations in the clay loam soil and from 5 to 500 mg kg−1 in the sandy loam. It was postulated that soil microorganisms were able to use the N or C from the s‐triazine ring. Atrazine at 500 and 5000 mg kg−1 may have increased soil microbial growth and activity and thus increased the degradation of atrazine based on the increase in soil respiration in the clay loam soil. Degradation pathways in both soils apparently were not influenced by concentration. Ring cleavage and hydrolysis were the major metabolic pathways in both soils, with dealkylation of less importance. Addition of a dairy manure amendment increased the rate of atrazine mineralization, while corn meal decreased and (NH4)2HPO4 amendments prevented mineralization.
Green and Animal Manure‐Derived Dissolved Organic Matter Effects on Phosphorus Sorption
Authors: Ohno Tsutomu , Crannell Bradley S.
Published: July 2010

This study was conducted to investigate the effect of dissolved organic matter (DOM) extracted from common soil amendments and citric acid on the P sorption of an acidic soil. Hairy vetch (Vivia billosa L.) and crimson clover (Trifolium incarnatum L.) were used as sources for green manure‐derived DOM. Cattle manure (Bos taurus) and poultry manure (Gallus domesticus) were used as sources for animal manure‐derived DOM. The negative charge density of the water‐soluble DOM ranged from 4.6 to 13.4 mmolc g−1 C. Estimated molecular weight ranges were 710 to 850 for the green manure DOM and 2000 to 2800 for the animal manure DOM. Phosphorus sorption experiments were conducted at 40 mmol P kg−1 soil and 0, 5, 10, 15, and 20 mM total soluble carbon (Crs) for each green and animal manure source. The DOM extracted from vetch and clover, as well as citric acid, inhibited P sorption in the order citric acid > clover > vetch. The DOM extracted from the animal manures did not affect P sorption. The ability of the green manure DOM to inhibit P sorption was related to its ability to react with soil Al through ligand exchange reactions at lower DOM concentrations and through complexation reactions at higher DOM concentrations. The average ratio of Al solubilization to P sorption inhibition on a molar basis was 1.76 ± 0.44. Ultraviolet absorbance and fluorescence data suggested that the higher molecular weight of the animal manure derived‐DOM was a factor in its inability to react with soil Al. The results of this study suggest that management systems that use green manures may increase the availability of P by decreasing the sorption of added P to soils.
Plutonium Association with Selected Solid Phases in Soils of Rocky Flats, Colorado, Using Sequential Extraction Technique
Authors: Litaor M. Iggy , Ibrahim S. A.
Published: July 2010

Plutonium contamination in the soil environs of Rocky Flats, CO, has been a potential health risk to the public since the late 1960s. Although the measurement of total activity of Pu‐239 + 240 in the soil is important information in appraising this risk, total activity does not provide the information required to characterize the geochemical behavior that affects the transport of Pu from the soil and vadose zone to groundwater. A sequential extraction experiment was conducted to assess the geochemical association of Pu with selected mineralogical and chemical phases of the soil. In the surface horizons, Pu‐239 + 240 was primarily associated with the organic C (45–65%), sesquioxides (20–40%), and the residual fraction (10–15%). A small portion of Pu‐239 + 240 was associated with soluble (0.09–0.22%), exchangeable (0.04–0.08%), and carbonates (0.57–7.0%) phases. These results suggest that under the observed pH and oxic conditions, relatively little Pu‐239 + 240 is available for geochemically induced transport processes. Uncommon hydrogeochemical conditions were observed during the spring of 1995, which may have facilitated a partial dissolution of sesquioxides followed by desorption of Pu resulting in increased Pu mobility. Systematic errors in the sequential extraction experiment due to postextraction readsorption were evaluated using Np‐237 tracer as a surrogate to Pu‐239. The results suggested that postextraction readsorption rates were insignificant during the first 30 min after extraction for most chemical and mineralogical phases under study.
Soil Environmental Quality: A European Perspective
Authors: Bouma J.
Published: July 2010

Environmental quality is a major political concern in Europe and the important role of the soil is widely recognized. However, soil science still has an important role to play in translating good intentions into policies supporting the implementation of innovative soil management procedures that can ensure sustainable production systems in harmony with nature. Society is impatient and demands solutions from science. This could in time lead to only holistic, applied research that is not adequately supported by basic research. A plea is made for establishing research chains in which a holistic, interdisciplinary analysis of a problem to be studied is followed by reductionistic basic research in relevant areas. Results are again communicated to and analyzed by the holistic team to be integrated in the overall analysis. Two areas of particular concern in soil research are discussed: (i) the implications of variability in space and time on defining characteristic threshold values for environmental indicators, and (ii) providing data to economists, which will allow them to express environmental effects of soil management practices in monetary terms.
Soil Quality and its Dependence on Dynamic Physical Processes
Authors: Wagenet R. J. , Hutson J. L.
Published: July 2010

Protecting the ability of the soil resource to operate for the benefit of all biological entities is a necessary and unarguable goal. Soils are central to life, and the processes that occur in soils are crucial components of the global ecosystem. Protecting these resources from deterioration as a result of human activities is the present focus of many, not only in the scientific community, but in society at‐large. Ecologists, climatologists, hydrologists and, of course, agriculturalists are well aware of the importance of protecting soil quality. So too, have land‐use planners, public works engineers, water quality specialists, and fertilizer and pesticide dealers become aware of the importance of maintaining the ability of soil to sustain plant growth, infiltrate and redistribute water and chemicals, and act as natural biological filters. The dynamic processes that exist in a soil system are the determinants of the soil's condition, or quality, at any one time. These dynamic processes determine the potential of the soil to, for example, redistribute water, allow gas exchange, and bear a load at a specific time. Prediction of soil quality must project the effect of these dynamic processes in current or proposed management systems, if soil quality is to be maintained or enhanced.
Determining Soil Hydraulic Properties by Inverse Method in One‐Dimensional Unsaturated Flow
Authors: Lehmann François , Ackerer Philippe
Published: July 2010

For physically based models, the hydraulic conductivity function and the effective fluid saturation function are the most important parameters affecting water and solute movements in the vadose zone. Direct parameter measurements in heterogeneous soils are very difficult and scale‐dependent. The inverse approach is an indirect and interesting way to estimate hydrodynamic parameters. In‐situ soil water retention and hydraulic conductivity relations were determined for a layered soil from knowledge of initial and boundary conditions and observed pressure heads during infiltration, evaporation, and redistribution. We will present efficient algorithms for inverse problems applied to both synthetic and real test cases. The location and the number of observation points are very important; the number of observations must be sufficient, i.e., the variables have to be measured for each layer of the soil. Large differences in sensitivity are observed among the various model parameters.
Comparative Fates of Atrazine and Deethylatrazine in Sterile and Nonsterile Soils
Authors: Kruger Ellen L. , Rice Pamela J. , Anhalt Jennifer C. , Anderson Todd A. , Coats Joel R.
Published: July 2010

Assessment of biotic and abiotic mechanisms of atrazine (ATR) and deethylatrazine (DEA) breakdown is necessary to identify major degradation pathways and understand soil conditions necessary for these mechanisms to occur. Our purpose was to compare fates of ATR and DEA in laboratory radiotracer studies to elucidate the effects of soil moisture status and soil depth on degradation and persistence. Atrazine and DEA were more persistent in subsurface soil than in surface soil. After 120‐d incubation, bound residues were significantly greater in surface soils than in subsurface soils. In 14C‐DEA‐treated soil, biological activity contributed to decreased persistence of DEA in saturated surface soil in contrast with unsaturated surface soil after 60 d. Biological activity also contributed to decreased persistence of ATR in saturated subsurface soil in contrast with unsaturated subsurface soil after 120 d, and the decreased persistence corresponded to significantly greater amounts of DEA, deisopropylatrazine (DIA), and polar degradation products compared with other treatments. The percentage of applied 14C‐ATR that degraded to DEA and DIA increased approximately threefold during the 60‐ to 120‐d incubation in nonsterile saturated subsurface soil. Greater quantities of polar degradation products were formed in 14C‐DEA‐treated nonsterile compared with sterile soils. Half‐lives (from first‐order degradation rate constants) of ATR and DEA were significantly longer in subsurface soil compared with surface soils. Biotic mechanisms contributed to the half‐lives of ATR (in surface and subsurface soil) and DEA (in subsurface soil) being significantly shorter under saturated soil moisture conditions compared with unsaturated soil moisture conditions.
Agriculture and Nitrate Concentrations in Maryland Community Water System Wells
Authors: Lichtenberg Erik , Shapiro Lisa K.
Published: July 2010

The presence of NO3‐N in well water is a cause of growing concern throughout the USA. Previous studies indicate that agriculture is a major contributor to this problem. This study uses data on NO3‐N concentrations in drinking water wells, on hydrological characteristics of those wells, and on measures of agricultural activity and of the extent of residential land use to construct statistical relationships between land use and well water quality in Maryland community water system wells. Tobit regression was used to correct for truncation bias arising from the fact that NO3‐N was not reported at concentrations below 0.1 mg/L. Exponential and linear specifications were estimated; non‐nested hypothesis tests indicated that the exponential specification fit the data better than the linear one. Deeper wells appear less vulnerable to NO3‐N contamination, wells in unconfined aquifers and especially limestone formations, more so. Broiler and corn (Zea mays L.) production were associated with higher NO3‐N concentrations in drinking water in both specifications, indicating that agriculture‐oriented efforts aimed at preserving groundwater quality should be concentrated on corn and broiler production. Septic systems for waste disposal also appear to have a substantial impact on NO3‐N concentrations in drinking water, suggesting that land use planning measures such as minimum lot size zoning may be needed to prevent conversion of crop and livestock production to residential units relying on septic systems from exacerbating groundwater quality problems.
Nitrate Leaching under a Cereal Rye Cover Crop
Authors: Brandi‐Dohrn Florian M. , Hess Mario , Selker John S. , Dick Richard P. , Kauffman Susan M. , Hemphill Delbert D.
Published: July 2010

Winter cover crops hold potential to capture excess NO3− and reduce leaching by recycling nutrients. The objective of this study was to compare winter NO3‐N leaching losses under winter‐fallow and a winter cereal rye (Secale cereale L.) cover crop following the harvest of sweet corn (Zea mays L.) or broccoli (Brassica oleracea var. italica Plenck). Leachate was sampled with passive capillary wick samplers that apply a suction of 0 to 5 kPa to the soil‐pore water and intercept leachate in a pan of known area. Without disturbing the over‐laying soil profile, 32 samplers (0.26 m2) were installed at a depth of 1.2 m in a Willamette loam (fine‐silty mixed mesic Pachic Ultic Argixeroll). The randomized complete‐block split plot design of this cover crop‐crop rotation study (initiated in 1989) has cropping system (winter fallow vs. winter cereal rye) as main plots and three N application rates, ranging from 0 to 280 kg N ha−1 yr−1, as subplots. At the recommended N rate for the summer crops, NO3 leaching losses were 48 kg N ha−1 under sweet corn‐winter‐fallow for winter 1992–1993, 55 kg N ha−1 under broccoli‐winter‐fallow for winter 1993–1994, and 103 kg N ha−1 under sweet corn‐winter‐fallow for winter 1994–1995, which were reduced to 32, 21, and 69 kg N ha−1, respectively, under winter cereal rye. For the first two winters, most of the variation (61%) in NO3− leaching was explained by N rate (29%), cereal rye N uptake (17%), and volume of leachate (15%). Seasonal, flow‐weighted concentrations at the recommended N rate were 13.4 mg N L−1 under sweet corn‐winter‐fallow (1992–1993), 21.9 mg N L−1 under broccoli‐winter‐fallow, and 17.8 mg N L−1 under sweet corn‐winter‐fallow (1994–1995), which were reduced by 39, 58, and 22%, respectively, under winter cereal rye.
Nutrient, Carbon, and Mass Loss during Composting of Beef Cattle Feedlot Manure
Authors: Eghball Bahman , Power James F. , Gilley John E. , Doran John W.
Published: July 2010

Quantification of nutrient and mass loss during composting is needed to understand the composting process, to implement methods for nutrient conservation, and to reduce potential adverse environmental impact. Beef cattle feedlot manure was composted in a windrow on an open concrete area in 1992, 1993, and 1994 to determine the amounts of nutrient, C, and mass loss during composting. The area was enclosed on all sides with a 0.2 m high metal sheet to direct runoff to a fiberglass tank (4000 L) during rainfall. Nutrients in runoff represented combined runoff and leaching losses. Nutrients, C, and mass loss during composting was determined by the difference between the amounts at the beginning and at the end of the composting. Nitrogen loss during composting ranged from 19 to 42% and was related to the initial manure N content. Ammonia volatilization (calculated by difference) accounted for >92% of the N loss whereas combined runoff nitrate and ammonium loss was <0.5%. Mass loss was relatively low (15–20%) while loss ranged from 46 to 62% and was basically all through bio‐oxidation. Phosphorus runoff loss, the main mechanism for P loss, was low (<2%). Manure N/P ratio decreased during composting, indicating a greater soil P buildup potential with compost application. Potassium and Na losses in runoff were high (>6.5% each) 1992 and 1993; they were low (<2% each) in 1994 due to fewer rainfall. Calcium and Mg losses were <6% each year. Nutrient and salt loss during composting resulted in reduced electrical conductivity of the composted manure. Ammonium and P concentrations in runoff would create surface water pollution if runoff was not diluted with fresh water.
Kinetics and Temperature Dependence of Potential Denitrification in Riparian Soils
Authors: Maag Michael , Malinovsky Michael , Nielsen Steen M.
Published: July 2010

We studied factors influencing potential denitrification activity (PDA) in anaerobic soil samples amended with NO3− from a riparian meadow with agricultural uplands, and a reedswamp receiving nitrate‐containing creek water at two loading rates. Both sites had high levels of PDA (3–28 mg N kg−1 h−1), which decreased exponentially with depth. High correlations were seen between PDA and mineralizable and water soluble C. At the meadow site, high apparent Km values (29–51 µM N) were found in the upper 150 cm of the soil profile due to a lateral flow of nitrate‐rich water. Below this depth, Km values were 10 to 30 times lower due to the influence of nutrient poor groundwater. In the 0‐ to 10‐cm profile of the reedswamp soil, the highest apparent Km (89 µM N) was found on the high load site, while no differences between the high and low load sites were seen below this depth (range 0.6–11 µM N). The capacity to reduce nitrate (Vmax) was in the order riparian meadow ≅ high loaded reedswamp > low loaded reedswamp. The activation energy for PDA ranged from 47 to 89 kJ mol−1, and Q10 for the 5 to 15°C interval ranged from 2 to 3.8. Our data suggest that long‐term use of riparian areas to attenuate high loads of NO3− can increase the maximum NO3− removal capacity of these areas, but at the same time increase the concentration of NO3− in water leaving this area compared with water leaving low loaded sites.
Relationships between Soil Nutrients and Plant Species Composition in Everglades Peatlands
Authors: Craft Christopher B. , Richardson Curtis J.
Published: July 2010

Base cations (Ca, Mg, K, Na) and metals (Al, Fe, Mn) were measured in peatlands of the northern and central Everglades to (i) determine the extent and degree of elemental enrichment of the peat caused by agricultural drainage and (ii) assess the relationship between cattail (Typha latifolia L.) encroachment into sawgrass (Cladium jamaicense Crantz) communities and elemental (cations, metals, P) enrichment of the peat. Soil Ca, Mg, and Na (0–10 cm) decreased, and Al and Fe increased from north to south through the northern and central Everglades. In particular, nutrient‐enriched (P) areas of northern WCA 2A had higher concentrations and accumulation rates of Ca, Mg, and Na than areas to the south. A detailed investigation along a P enrichment gradient in northern WCA 2A revealed a gradient of Ca and Na enrichment extending 1.6 to 3.4 km downstream of the Hillsboro canal, the source of agricultural drainage to WCA 2A. Rates of Ca (35 g/m2 per yr) and Na (1.5–3.2 g/m2 per yr) accumulation were 2 to 10 times greater 1.6 km below the Hillsboro canal than in areas 3.4 to 10.7 km downstream. Correlation analysis revealed that macrophyte species composition along the enrichment gradient was highly correlated with soil P (0–24 cm) but not with soil Na or Ca. The percent frequency of cattail (r = 0.74) and other species (r = 0.66) was positively correlated while sawgrass (r = −0.83) was inversely correlated with soil P content. These findings suggest that cattail encroachment into sawgrass communities is favored by enrichment of the peat with P loadings from agricultural drainage pumped into northern WCA 2A.
Heavy Metal (Copper, Lead, and Zinc) Accumulation and Excretion by the Earthworm, Dendrobaena veneta
Authors: Marinussen Mari P. J. C. , van der Zee Sjoerd E. A. T. M. , de Haan Frans A. M. , Bouwman Lydia M. , Hefting Mariet M.
Published: July 2010

To obtain knowledge about heavy metal kinetics in earthworms (Dendrobaena veneta), we performed accumulation and excretion experiments under laboratory conditions using soils from a heavy metal (Cu, Pb, and Zn)‐contaminated site. To determine heavy metal accumulation rate, earthworms were exposed for 1, 2, 3, 7, 14, 28, 56, or 112 d to soil MH (Cu: 815 mg kg−1, Pb: 340 mg kg−1, and Zn: 225 mg kg−1). After exposure for 28 d to soil LB (Cu 242 mg kg−1, Pb: 109 mg kg−1, Zn 72 mg kg−1) or for 112 d to soil MH, D. veneta were transferred to uncontaminated soil and sampled after 1, 2, 3, 7, 14, 28, or 56 d to determine heavy metal excretion rates. Fourteen days after the transfer to the uncontaminated soil, some earthworms were transferred back to soil LB to determine the accumulation after a short recovery period. The Cu accumulation until Day 56 could be described by a one‐compartment model. At Day 112, however, we observed an unexpected further increase in tissue Cu concentration (CCu). We observed a significant increase in CZn, only at Day 112. Excretion of Cu could be described excellently by a two compartment model, the half‐life times being t1/2;1 ≈ 0.36 d, and t1/2;2 ≈ 37 d. Excretion of Pb could be described with a one‐compartment model. After a fast initial excretion (t1/2 ≈ 0.70 d), Pb excretion stagnated. The accumulation after a 14‐d recovery period appeared to be significantly less than the initial accumulation. The Pb accumulation appeared to be slower after recovery than before.
Soil Denitrification and Nitrous Oxide Losses under Corn Irrigated with High‐Nitrate Groundwater
Authors: Qian Jin H. , Doran John W. , Weier Keith L. , Mosier Arvin R. , Peterson Todd A. , Power James F.
Published: July 2010

Inappropriate management of irrigation water and fertilizer N in irrigated corn (Zea mays L.) has resulted in excess N leaching from the rooting zone and NO−3 contamination of groundwater. A better understanding of microbially mediated conversion of plant available N to gaseous N forms is needed for more efficient N use, to evaluate the impact of radiatively important gas production such as nitrous oxide (N2O) on air quality, and to determine the potential of microbial denitrification for remediating high‐NO−3 irrigation water. Soil denitrification and N2O losses from pivot irrigated corn were measured during the 1991 and 1992 growing seasons using surface gas chambers at the Management System Evaluation Area (MSEA) site for water quality research in the Central Platte Valley near Shelton, NE. Denitrification and N2O losses remained low throughout most of the growing season, generally ranging from 10 to 50 g N ha−1 d−1, when soil water contents were generally below 60% water‐filled pore space (WFPS). Nitrous oxide was the major gaseous N product under these conditions. When soils were wetted by irrigation or rainfall to >70% WFPS, denitrification losses ranged from 0.2 to 1.4 kg N ha−1 d−1 with N2 comprising 80 to 98% of the denitrification gases measured. Monthly average denitrification losses across years were highly correlated (r = 0.693) with time of growing season, suggesting a possible link between plant growth and denitrification. Seasonal gaseous N losses via denitrification and N2O emission from irrigated corn represented 1 to 5% of the N applied as fertilizer or in irrigation water during a relatively dry 1991 season and the 1992 season with near normal precipitation. Results of our 2‐yr study indicate that under good irrigation and N management practices gaseous N losses from denitrification and N2O production pose little additional threat to atmospheric quality or N‐use efficiency but also provide little hope for bioremediation of high‐NO−3 groundwater.
Organic Phosphorus in Solutions and Leachates from Soils Treated with Animal Slurries
Authors: Chardon W. J. , Oenema O. , del Castilho P. , Vriesema R. , Japenga J. , Blaauw D.
Published: July 2010

A substantial part of the total phosphorus (P) in soil solution and leachates can be present as dissolved organic phosphorus (DOP). The DOP may be more mobile than inorganic orthophosphate and thus it can be an important P source for surface water eutrophication. This paper describes a series of four experiments that investigated the effects of animal waste application to sandy soil on DOP leaching. The first experiment examined the effect of storing pig slurry on DOP fractionation, using gel permeation chromatography. Experiment two and three examined the immediate and long‐term effects of animal waste application to soil in laboratory columns and outdoor maize‐grown lysimeters, respectively. In the fourth experiment concentrations of DOP and total P (TP) in soil solutions at various depths were determined in a long‐term field experiment. Results indicate that DOP in pig slurry is mainly found in high molecular weight (MW) compounds (Exp. 1). From the soil column more than 90%, and from the lysimeters more than 70% of TP leached as DOP (Exp. 2 and 3). In the lysimeter experiment (Exp. 3), leaching of TP mainly occurred in periods of low Cl and NO3 concentrations, induced by high leaching rates. This may indicate that P transport in these periods was mediated by DOC or other colloidal particles. The field experiment (Exp. 4), showed that DOP as a percentage of TP in the soil solution increased from about 10% in the topsoil to more than 70% at 70 to 80 cm depth, which was mainly due to a decrease in MRP. Thus, DOP is an important form of P in leachates and in soil solutions in the subsoil, and characterization of this DOP can improve our understanding of P leaching from soils.
Testing Denitrification Functions of Dynamic Crop Models
Authors: Marchetti R. , Donatelli M. , Spallacci P.
Published: July 2010

Denitrification (DN) has an important role in models simulating soil nitrate leaching, because denitrification losses influence the soil N budget, hence the amount of nitrate available for leaching. In spite of the importance of DN estimate, the behavior of submodels simulating DN losses is not well known. The aim of this study was to improve the knowledge of the behavior of submodels simulating DN losses in selected crop growth/N‐leaching models. To remove the interference of the other processes on the results, we isolated the algorithms predicting the denitrification rate (DNR) and applied them to three data sets selected from the available literature. Denitrification subroutines were taken from the models EPIC, CropSyst, CREAMS, GLEAMS, CERES‐N, and NLEAP. A preliminary sensitivity analysis emphasized how quite similar algorithms can give rise to considerably different predictions. The measured vs. predicted values comparison confirmed DNR to be remarkably affected by the soil water content (SW) relationship with soil water values at field capacity and/or at saturation. CERES‐N, CREAMS, GLEAMS, and EPIC submodels underestimated even up to 100% the number of occasions where DNR > 0, since they simulated the DN process only when SW values were higher than SW at field capacity, whereas in real systems DN occurs even at lower SW values. Results suggest that DN modeling should take into greater account the contribution to DN losses during aerobic conditions. The large natural variation of DNR measurements invalidates the use of statistical criteria for the comparison of measured vs. estimated DN values in deterministic models.
Pesticides in the San Joaquin River, California: Inputs from Dormant Sprayed Orchards
Authors: Domagalski Joseph L. , Dubrovsky Neil M. , Kratzer Charles R.
Published: July 2010

Rainfall‐induced runoff mobilized pesticides to the San Joaquin River and its tributaries during a 3.8‐cm rainstorm beginning the evening of 7 February and lasting through the morning of 8 Feb. 1993. Two distinct peaks of organophosphate pesticide concentrations were measured at the mouth of the San Joaquin River. These two peaks were attributed to contrasts between the soil texture, basin size, pesticide‐use patterns, and hydrology of the eastern and western San Joaquin Valley. The fine soil texture and small size of the western tributary basins contributed to rapid runoff. In western valley streams, diazinon concentrations peaked within hours of the rainfall's end and then decreased because of a combination of dilution with pesticide‐free runoff from the nearby Coast Ranges and decreasing concentrations in the agricultural runoff. Peak concentrations for the Merced River, a large tributary of the eastern San Joaquin Valley, occurred at least a day later than those of the western tributary streams. That delay may be due to the presence of well‐drained soils in the eastern San Joaquin Valley, the larger size of the Merced River drainage basin, and the management of surface‐water drainage networks. A subsequent storm on 18 and 19 February resulted in much lower concentrations of most organophosphate pesticides suggesting that the first storm had mobilized most of the pesticides that were available for rainfall‐induced transport.