bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Air‐Drying on Sorption Kinetics of the Herbicide Chlortoluron in Soil
Authors: Altfelder Sven , Streck Thilo , Richter Jörg
Published: July 2010

Batch techniques were utilized to investigate sorption kinetics of chlortoluron (3‐(3‐chlor‐p‐tolyl)‐1,1‐dimethylurea) in two field‐moist soils, a silt loam (Typic Hapludalf) and a loamy sand (Aquic Haplumbrept), containing 1.1 and 0.7% organic C. To investigate effects of soil pretreatment, a part of both soil samples was initially air‐dried. Initially sorption‐desorption isotherms were measured using field‐moist soils. Both isotherms exhibited pronounced hysteresis. The fit of a nonlinear kinetic two‐stage sorption model to the data suggests that hysteresis was caused by nonattainment of equilibrium within the 24‐h agitation periods. This hypothesis is supported by the fact that the estimated kinetic parameters were well suited to predict concentration vs. time experiments in both soils. The prediction of sorption‐desorption isotherms measured using air‐dried soils failed. Compared with the predicted data, adsorption in air‐dried soil was increased while desorption hysteresis was less pronounced. Further experiments indicated that changes of soil organic matter (SOM) caused by air‐drying were responsible for this effect. Measuring 24‐h partitioning coefficients using the air‐dried soils, rewetted to field‐moisture for varying periods of time, revealed that in the course of 80 h (silt loam) and 500 h (loamy sand) after rewetting, the sorption properties of the air‐dried soils were again equal to those of the respective field‐moist soils.
Baseline Concentrations of 15 Trace Elements in Florida Surface Soils
Authors: Chen Ming , Ma Lena Q. , Harris Willie G.
Published: July 2010

The objective of this study was to establish baseline concentrations for 15 potentially toxic elements (Ag, As, Ba, Be, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, and Zn) based on 448 representative Florida surface soils using microwave assisted HNO3‐HCl‐HF digestion. Baseline concentrations of those elements were (mg kg−1): Ag 0.07–2.50, As 0.02–7.01, Ba 1.67–112, Be 0.04–4.15, Cd 0–0.33, Cr 0.89–80.7, Cu 0.22–21.9, Hg 0.00075–0.0396, Mo 0.13–6.76, Ni 1.70–48.5, Pb 0.69–42.0, Sb 0.06–0.79, Se 0.01–1.11, and Zn 0.89–29.6, respectively. Upper baseline values for most elements corresponded with these reported in literature, except Ba, Hg, Mn, Sb, and Zn, which were 3 to 23 times lower. Soil properties, including pH, organic carbon (OC), particle size, cation‐exchange capacity (CEC), available water, extractable base, extractable acidity, total Ca, Mg, P, K, Fe, and Al concentrations, were related to metal concentrations using factorial analysis. Eight factors were identified (total Fe and Al, CEC, pH, clay, OC, total Ni and Mo, total Sb and Pb, and total Hg) and accounted for 87% of the total variance, suggesting that metal concentrations were primarily controlled by soil compositions. Multiple regression of elemental concentrations against total Fe, total Al, clay, OC, CEC, and pH was significant for all elements. Partial correlation coefficients indicated that total Fe and/or Al explained most of the variance for Mn, Ni, Ba, Be, Hg, As, Cd, Cr, Cu, Mo, Pb, and Zn concentrations. Most of the variance in Se was related to clay, whereas those of Ag and Sb related to clay and total Al.
Oxidation and Mobilization of Selenium by Nitrate in Irrigation Drainage
Authors: Wright Winfield G.
Published: July 2010

Selenium (Se) can be oxidized by nitrate (NO−3) from irrigation on Cretaceous marine shale in western Colorado. Dissolved Se concentrations are positively correlated with dissolved NO−3 concentrations in surface water and ground water samples from irrigated areas. Redox conditions dominate in the mobilization of Se in marine shale hydrogeologic settings; dissolved Se concentrations increase with increasing platinum‐electrode potentials. Theoretical calculations for the oxidation of Se by NO−3 and oxygen show favorable Gibbs free energies for the oxidation of Se by NO−3, indicating NO−3 can act as an electron acceptor for the oxidation of Se. Laboratory batch experiments were performed by adding Mancos Shale samples to zero‐dissolved‐oxygen water containing 0, 5, 50, and 100 mg/L NO−3 as N (mg N/L). Samples were incubated in airtight bottles at 25°C for 188 d; samples collected from the batch experiment bottles show increased Se concentrations over time with increased NO−3 concentrations. Pseudo first‐order rate constants for NO−3 oxidation of Se ranged from 0.0007 to 0.0048/d for 0 to 100 mg N/L NO−3 concentrations, respectively. Management of N fertilizer applications in Cretaceous shale settings might help to control the oxidation and mobilization of Se and other trace constituents into the environment.
Redistribution of Trace Elements from Contaminated Sediments of Lake Coeur d'Alene during Oxygenation
Authors: La Force Matthew J. , Fendorf Scott , Li Guangchao , Rosenzweig R. Frank
Published: July 2010

Sediments of Coeur d'Alene Lake in northern Idaho are contaminated with heavy metals as a result of mining in the Coeur d'Alene River basin. Dredging and disposal operations have been suggested as a possible means of environmental remediation; thus, detailed knowledge is required as to how sediment oxygenation can result in the redistribution of trace elements. To simulate changing physicochemical soil conditions, stirred batch experiments were conducted using fresh sediment core material retrieved from the lake. Fifty grams of sediment were added to 750 mL of double deionized water and mixed while being oxygenated for 260 h. The following parameters were monitored as a function of time: pH and Eh, contaminant trace‐element release into the aqueous phase, and metal abundance within operationally defined fractions of the solid phase: magnesium chloride (exchangeable), sodium hypochlorite (organic), sodium acetate‐acetic acid (carbonate), ammonium oxalate in the dark (non‐crystalline), hydroxylamine hydrochloride (crystalline), and potassium perchlorate‐hydrochloric‐nitric acid (sulfidic) extractable sediment fractions. In all trials, levels of aqueous‐phase Zn remained high throughout the simulations (6.60 mg L−1) and were highly correlated (sigma value = 0.95) with Mn. Oxygenation and disturbance resulted in a shift in trace element partitioning from the sodium hypochlorite (organic) and potassium perchlorate‐hydrochloric‐nitric acid extractable (sulfidic) fractions into the ammonium oxalate in the dark (noncrystalline) extractable fraction. Overall, these results indicate that oxygenation and agitation of anaerobic sediment results in Zn release into solution with concomitant redistribution of trace elements in the solid‐phase.
Seasonal Surface Runoff Losses of Nutrients and Metals from Soils Fertilized with Broiler Litter and Commercial Fertilizer
Authors: Wood B. H. , Wood C. W. , Yoo K. H. , Yoon K. S. , Delaney D. P.
Published: July 2010

While elevated concentrations of N and P have been observed in surface runoff from broiler litter‐amended fields, impacts of other nutrients in broiler litter such as Ca, K, Mg, Mn, Cu, and Zn have not been identified. A study was conducted on a 4% slope during 1991 to 1993 at Belle Mina, AL, on a Decatur silty clay (clayey, kaolinitic, thermic Rhodic Paleudult) to determine effects of broiler litter (BL) on seasonal transport losses of nutrients and heavy metals in surface water. A corn (Zea mays L.)‐winter rye (Secale cereale L.) cropping system was fertilized with either: (i) 9 Mg BL ha−1 (BL9), (ii) 18 Mg BL ha−1 (BL18), or (iii) commercial fertilizer at the recommended rate (CF). Runoff water samples were collected after each runoff producing rainfall event. Litter treatments decreased sediment flow‐weighted concentrations during the second corn growing season owing to residual broiler litter. Flow‐weighted concentrations of NO3‐N and NH4‐N were highest under BL18 during the second corn season. Total P and dissolved P flow‐weighted concentrations and seasonal transport losses were highest under BL18 during the second corn season. Sediment nutrient flow‐weighted concentrations of K, Mg, and Mn were highest under CF during the second corn season. Dissolved nutrient flow‐weighted concentrations of Ca, K, and Mg were highest under BL18 during the second corn season. Nutrient flow‐weighted concentrations, except Ca, from all treatments provide adequate levels to support algae growth.
Phosphorus Loss in Drainflow from Intensively Managed Grassland Soils
Authors: Hooda P. S. , Moynagh M. , Svoboda I. F. , Edwards A. C. , Anderson H. A. , Sym G.
Published: July 2010

The loss of P in subsurface drainage from lysimeters (0.5 ha), managed as either monoculture grass or grass‐clover for the last 9 yr have been quantified. Both systems received two to three cattle slurry applications annually and were cut two to three times before being grazed by dairy cattle. Mineral fertilizer‐P was applied only to the grass‐clover (about 25 kg P ha−1 yr−1). After 9 yr, NaHCO3‐soluble P in the topsoil (0–10 cm) averaged 38 and 47 mg P kg−1 for the grass and grass‐clover respectively, giving an average increase of 1.0 mg OIsen‐P kg−1 yr−1 in the grass‐clover. Drainage‐weighted molybdate‐reactive phosphorus (MRP) and total phosphorus (TP) concentrations ranged from 0.16 to 0.38 mg P L−1 and 0.45 to 0.79 mg P L−1, respectively during the 2‐yr study period. The MRP and TP losses in subsurface‐flow from the grass‐clover (1.68–2.03 and 3.47–5.03 kg P ha−1 yr−1, respectively) were significantly larger than those from the grass (1.27–1.34 and 2.97–3.58 kg P ha−1 yr−1, respectively). Averaged across years and pastures, MRP accounted for 42% of the TP loss, while a non‐MRP form accounted for 41% of the TP loss through field drains. Particulate‐associated P represented about 17% of the TP loss. The P losses in subsurface runoff measured in the present study were much larger than previous estimates. The results also showed that, despite the subsoil having much larger P‐sorption capacity than the topsoil, significant amounts of P losses could occur through preferential hydrological pathways.
Nitrogen Balance in a Pond System Receiving Tertiary Effluent
Authors: Lund L. J.
Published: July 2010

A constructed wetland system near Riverside, CA, received tertiary treated effluent from the local wastewater treatment plant. This nitrate‐dominated effluent flowed through four ponds with a combined area of 10 ha, which were connected in series. Flow measuring devices were installed on the inlet and outlet to the pond system and suction lysimeters were installed beneath the ponds. Flow data, samples of surface water, and lysimeter extracts were collected for over 18 mo. Water and N balances were developed for a 1‐yr period, during which flow to the ponds was continuous. Of the water entering the pond system, 37% left as outflow, 3% evaporated, and 60% infiltrated. The average total inorganic nitrogen (TIN) concentration in the outflow was reduced by 32% compared with the inflow concentration (11.1 mg L−1 vs. 16.3 mg L−1). The average TIN concentration was 3.6 mg L−1 in extracts from beneath the ponds. Using a mass balance approach, 62% of the inflow TIN was not accounted for by TIN leaving the pond system in surface and subsurface flow. This TIN was lost from the system, most likely by denitrification. When expressed on an area basis, the TIN loss was approximately 1500 mg m−2 d−1, a value typical for many effluent dominated wetlands. Based on the results of this study, the city of Riverside decided to expand and enhance the wetlands for use in meeting their N discharge requirements, rather than investing in major capital improvements in additional in‐plant treatment facilities.
Mode of Transport of Surface‐Applied Phosphorus‐33 through a Clay and Sandy Soil
Authors: Djodjic Faruk , Bergström Lars , Ulén Barbro , Shirmohammadi Adel
Published: July 2010

Phosphorus (P) is the limiting nutrient for primary production in most freshwater ecosystems. The magnitude of P leaching from agricultural soils is therefore critical. Preferential flow has been proposed as a major cause for high P losses in structured clay soils. Undisturbed soil of two texturally different soils, that is, a day soil in which preferential flow was expected to be the main mode of water transport and a sandy soil where piston flow is the dominant process, were used in this study. Use of labeled P made it possible to determine the origin of leached P. An equivalent of 100 kg P ha−1, labeled with 33P, was added to the soil surface of each lysimeter. Water equivalents to 100 mm were added on five occasions with 7 d between each watering event. Ponded flow conditions were established during periods when water was added, to trigger preferential Bow behavior. Phosphorus leaching loads from day columns were much higher than P loads from sand columns. The average P leaching load for the five day columns was 4.0 kg ha−1, compared to only 56 g ha−1 for the three sand columns. The main part of leached P was in dissolved (PO4‐P) form. The recently added P prevailed in leachate from the clay soil indicating rapid transport of added P from the soil surface through the profile via macropores.
Leaching of Total Nitrogen from Nitrogen‐15‐Labeled Poultry Manure and Inorganic Nitrogen Fertilizer
Authors: Bergström Lars F. , Kirchmann Holger
Published: July 2010

Field lysimeters containing an undisturbed sandy soil were used to evaluate leaching of manure‐derived N over 3 yr. Manure labeled with 15N (poultry excreta), which was either fresh or had been decomposed under aerobic or anaerobic conditions, was applied in May during the first year at a rate corresponding to 100 kg total N ha−1. For comparison, labeled 15NH415NO3 (100 kg N ha−1) was applied simultaneously to additional lysimeters while others were left unfertilized. During the second and third year, all lysimeters, except the unfertilized ones, received unlabeled NH4NO3 at a rate of 100 kg N ha−1. Each year, barley (Hordeum vulgare L.) was seeded prior to fertilization. Based on the difference method, leaching of total N during the first year was not significantly different (P > 0.05) between lysimeters treated with NH4NO3, fresh manure, and anaerobic manure, but lower from those with aerobic manure. Regarding leaching of residual manure‐ and fertilizer‐derived N estimated with the 15N method, there was a significant difference (P < 0.05) between the NH4NO3 fertilized and manured lysimeters. As much as 19, 28, and 26% leached in the treatments with fresh, anaerobically, and aerobically decomposed manure, respectively, whereas only about 3% leached in the NH4NO3 fertilized lysimeters in the two subsequent years. The crop uptake of labeled N were smaller in the manured lysimetcrs than in the NH4NO3 fertilized lysimeters. These results suggest that there is a greater potential for N leaching in the longterm from animal manures than from inorganic N fertilizers.
Phosphorus Retention Capacity of the Spodic Horizon under Varying Environmental Conditions
Authors: Nair V. D. , Villapando R. R. , Graetz D. A.
Published: July 2010

The spodic (Bh) horizon of Spodosols with Al, Fe, and C accumulations usually has a high P sorption capacity. However, the Bh horizon of prevalent Spodosols in the Lake Okeechobee basin of Florida is subject to a fluctuating watertable that could change the dynamics of P in these soils under alternating aerobic and anaerobic conditions. Further, the Bh horizon of this basin is often impacted by P moving vertically following heavy surface application of dairy manure. Our objectives were to relate the P retention capacity of the Bh horizons of the Lake Okeechobee basin to other soil parameters, and to evaluate P retention of manure‐impacted Bh horizons under aerobic and anaerobic conditions. High watertable decreased the P retention capacity for the majority of the soils in this study. High manure‐impacted areas have Bh horizons with high P concentrations as a result of P movement from the surface A horizon through the eluted E horizon. The P appeared to be temporarily retained and could be released upon prolonged contact with water. This P is likely to move horizontally above the Bh horizon to drainage ditches and eventually into the lake, causing eutrophication. The equilibrium P concentrations and water soluble P concentrations of Bh horizon soils that did not receive high rates of manure application (native soils and pasture soils) are low and it is unlikely that P would move laterally out of such systems, above the Bh horizon.
Soil Carbon Inventories under a Bioenergy Crop (Switchgrass): Measurement Limitations
Authors: Garten C. T. , Wullschleger S. D.
Published: July 2010

Approximately 5 yr after planting, coarse root (>2 mm) carbon (C) and soil organic C (SOC) inventories (0–40 cm deep) were compared under different types of plant cover at four switchgrass (Panicum virgatum L.) production field trials in the southeastern USA. There was significantly (p ≤ 0.05) more coarse root C under switchgrass (Alamo variety) and forest cover than under tall fescue (Festuca arundinacea Schreb.), corn (Zea mays L.), or native pastures of mixed grasses. Inventories of SOC under switchgrass were not significantly greater than SOC inventories under other plant covers. At some locations the statistical power associated with ANOVA of SOC inventories was low, which raised questions about whether differences in SOC could be detected statistically. A minimum detectable difference (MDD) for SOC inventories was calculated. The MDD is the smallest detectable difference between treatment means once the variation, significance level, statistical power, and sample size are specified. The analysis indicated that a difference of ≈50 mg SOC/cm2 or 5 Mg SOC/ha, which is ≈10 to 15% of existing SOC, could be detected with reasonable sample sizes (n = 16) and good statistical power (1 − β = 0.90). The smallest difference in SOC inventories that can be detected, and only with exceedingly large sample sizes (n > 100), is ≈2 to 3% (≈10 mg SOC/cm2 or 1 Mg SOC/ha). These measurement limitations have implications for monitoring and verification of proposals to ameliorate increasing global atmospheric CO2 concentrations by sequestering C in soils.
Sewerage Overflows Put Production and Fertility of Dairy Cows at Risk
Authors: Meijer Gerwin A. L. , de Bree J. , Wagenaar J. A. , Spoelstra S. F.
Published: July 2010

More than 50% of the dairy farmers in the Netherlands use surface water as the main source of drinking water for their cows during the grazing season. The quality of this water may be affected by discharges from sewerage overflows, but possible effects on health of dairy cows have not been quantified. Our objective, therefore, was to assess the risk of impaired production and fertility in dairy cows that drink surface water in direct contact with a sewerage overflow. Standardized milk production of cows from 60 farms using surface water in direct contact with a sewerage overflow was 0.9 L d−1 less (P = 0.09) than that of cows from 397 farms using surface water not in contact with an overflow. Also, age at first calving was 20 d higher (P < 0.01) in heifers exposed to drinking water in contact with sewerage overflows. These results strengthen earlier suggestions that sewerage overflows may reduce production and fertility of dairy cows.
Herbicide Transport on Wind‐Eroded Sediment
Authors: Larney Francis J. , Cessna Allan J. , Bullock Murray S.
Published: July 2010

Although wind erosion is a pervasive soil degradation problem on the semiarid Canadian prairies, few studies have been conducted on wind‐eroded sediment as an environmental pathway for herbicide transport. An experiment was conducted on a clay loam soil at Lethbridge, AB, in 1993 to 1994, to examine wind‐eroded sediment as a transport mechanism for two soil‐incorporated [trifluralin (2,6‐dinitro‐N,N‐dipropyl‐4‐trifluoromethylaniline) and triallate (S‐2,3,3‐trichloroallyl diisopropylthiocarbamate)] and four surface‐applied herbicides [diclofop {(±)‐2‐[4‐(2,4‐dichlorophenoxy)phenoxy]propanoic acid), bromoxynil (3,5‐dibromo‐4‐hydroxybenzonitrile), mecoprop {(±)‐2‐(4‐chloro‐2‐methylphenoxy)propanoic acid}, and 2,4‐D (2,4‐dichlorophenoxyacetic acid)]. The concentrations of diclofop and bromoxynil in sediments decreased with increasing capture height, with the 100‐cm height having significantly lower concentrations (diclofop, 627 µg kg−1; bromoxynil, 70 µg kg−1) than the 10‐cm height (diclofop, 1132 µg kg−1; bromoxynil, 231 µg kg−1). This implies that these herbicides were primarily associated with larger soil particles captured closer to the soil surface. For the soil‐incorporated herbicides, concentrations were significantly higher in the surface soil (0–2.5 cm) than in the wind‐eroded sediment, whereas concentrations of surface‐applied herbicides were generally higher in wind‐eroded sediment than in surface soil. Overall wind erosion losses (expressed as a percent of amount applied) of the two soil‐incorporated herbicides (1.5%) were about three times lower than those of the four surface‐applied herbicides (average loss, 4.5%). The results demonstrate the potential hazard of environmental transport of herbicides on wind‐eroded sediment and its associated implications for off‐site air and water quality.
Organic Waste Amendments Effect on Zinc Fractions of Two Soils
Authors: Shuman Larry M.
Published: July 2010

Organic soil amendments can ameliorate metal toxicity to plants by redistributing metals to less available fractions. The objective of this study was to determine the effects of organic amendments on Zn distribution among soil fractions. Two soils (fine‐textured and coarse‐textured) were amended with five organic waste materials (some of which contained Zn) or commercial humic acid with and without 400 mg kg−1 Zn, incubated, and fractionated using a sequential extraction technique. Where no Zn was added most of the metals were in the residual fraction. Commercial compost, poultry litter, and industrial sewage sludge increased Zn in the exchangeable (EXC), organic (OM), and manganese oxide (MnOx) fractions due to Zn in the materials. Spent mushroom compost (SMC) redistributed Zn from the EXC fraction to the MnOx fraction for the coarse‐textured soil. Where Zn was added, most of the metal was in the EXC and OM fractions. The SMC and humic acid lowered Zn in the EXC fraction and increased Zn in the other fractions. Effects of the organic materials on Zn in soil fractions were more evident for the sandy soil dominated by quartz in the clay than for the finer‐textured soil dominated by kaolinite in the clay‐size fraction. It was concluded that organic materials high in Zn can increase Zn in the EXC, OM, and MnOx fractions where the soil is not contaminated and others such as SMC and HA can lower the potential availability of Zn in contaminated soils by redistributing it from the EXC to less soluble fractions.
Water Treatment Residual to Reduce Nutrients in Surface Runoff from Agricultural Land
Authors: Gallimore L. E. , Basta N. T. , Storm D. E. , Payton M. E. , Huhnke R. H. , Smolen M. D.
Published: July 2010

Application of animal manures in excessive amounts can result in surface runoff of nutrients and degradation of surface water. Best management practices that use chemical or by‐products to sorb nutrients can reduce nutrient loss from agricultural land. The objective of this work was to determine the ability of water treatment residual (WTR) to reduce N and P runoff from land treated with poultry litter. Different WTR (ABJ or WISTER) were used in two experiments different locations. Three WTR treatments were applied to plots that received poultry litter at 6.72 Mg ha−1 broadcast on bermudagrass [Cynodon dactylon (L.) Pers.] pasture. Treatments were broadcast (11.2 or 44.8 Mg ha−1), and a buffer strip (44.8 Mg ha−1) to the bottom 2.44 m of the plot. Experimental plots received simulated rainfall for 75 min at 6.35 cm h−1 within 24 h of litter and WTR application. Nitrogen, NH4, P, Al, and dissolved solids in surface runoff were determined. Mean dissolved P of 15.0 mg L−1 was reduced to 8.60 mg L−1 by the high broadcast and to 8.12 mg L−1 by the buffer strip ABJ treatments. Reductions in runoff P were attributed to amorphous Al in the WTR. Soluble NH4‐N was reduced from 33.7 to 11.3 mg L−1 (high broadcast) and to 17.9 mg L−1 (buffer strip) by ABJ. WISTER did not, however, reduce soluble NH4‐N or total N. Reduction in NH4‐N was related to cation‐exchange capacity of the WTR. Land application of WTR did not increase dissolved solids or Al in surface runoff.
Preferential Flow and Water Quality in Two New Zealand Soils Previously Irrigated with Wastewater
Authors: Magesan G. N. , Dalgety J. , Lee R. , Luo J. , van Oostrom A. J.
Published: July 2010

Preferential flow of bromide tracer through two New Zealand soils, Horotiu (Typic Hapludand) and Te Kowhai (Typic Ochraqualf) soils, was examined. These two soils differed in physical, chemical, and drainage characteristics. These soils had been irrigated with meat‐processing wastewater for 38 mo that ceased 3 mo before this study. Impact of heavy rainfall on residual water quality from such wastewater applied soils was examined by measuring the concentrations of anions (nitrate and phosphate), and cations (Na, K, Ca, Mg, and ammonium) in leachates collected. Heavy rainfall did not appear to have any impact on leachate quality, as indicated by low nitrate‐N and phosphate concentrations compared with those measured during wastewater irrigation. While no preferential flow occurred in the Horotiu soil when it was wetted to field capacity, preferential flow occurred to depth in the Te Kowhal soil under similar conditions. Other water quality problems (e.g., pathogens), which were not investigated in this study may arise in Te Kowhai soils under heavy rainfall.
Lolium perenne Grasslands May Function as a Sink for Atmospheric Carbon Dioxide
Authors: van Ginkel J. H. , Whitmore A. P. , Gorissen A.
Published: July 2010

Model calculations and scenario studies suggest the existence of a considerable positive feedback between temperature and CO2 levels in the atmosphere. Rising temperatures are supposed to increase decomposition of soil organic C leading to increased production of CO2 and this extra CO2 induces a positive feedback by raising the temperature still further. Evidence was found that negative feedback mechanisms also exist: more primary production is allocated to roots as atmospheric CO2 rises and these roots decompose more slowly than roots grown at ambient CO2 levels. Experimental data partly obtained with 14C‐techniques were applied in a grassland C model. The model results show that at an atmospheric CO2 concentration of 700 µL L−1 increased belowground C storage will be more than sufficient to balance the increased decomposition of soil organic C in a ryegrass (Lolium perenne L.) grassland soil. Once a doubling of the present atmospheric CO2 concentration has been reached, C equivalent to 55% of the annual CO2 increase above 1 ha ryegrass can be withdrawn from the atmosphere. This indicates that grassland soils represent a significant sink for rising atmospheric CO2.
Mineralogy of Agricultural Source Soil and Respirable Dust in California
Authors: Clausnitzer H. , Singer M. J.
Published: July 2010

Inhalation of respirable dust (RD), defined as particles ≤4 µm in aerodynamic diameter, is a health concern. Soil disturbance by farming produces a range of airborne soil minerals of various sizes, but little is known about RD mineralogy compared with source soil or about mineralogy of RD as a function of particle size. General assumptions are that dust mineralogy reflects the source soil and that there is no sorting of RD mineralogy by particle size. We tested these assumptions by determining the size and mineralogy of RD particles from specific farming activities and comparing them to the source soil mineralogy. Samples were taken from plots growing furrow‐irrigated crops near Davis, CA. Source‐soil was analyzed by x‐ray diffraction (XRD). Respirable dust was analyzed by scanning electron microscopy and transmission electron microscopy (TEM) with selected area electron diffraction. Mineralogy and size data of mineral groups from the two techniques were different. The TEM method was more reliable because it included crystallographic data as well as elemental composition and particle morphology. The same major mineral groups (quartz, mica, feldspar, and clays) were found in the RD and the source soil, but minor constituents of the RD such as serpentine minerals and zeolites were not detected in the source soil because they were not sufficiently abundant to be detected by standard XRD techniques. No significant sorting of source soil mineralogy occurred over the short distance between soil and RD sampler.
Plant Nutrient Availability from Mixtures of Fly Ashes and Biosolids
Authors: Schumann Arnold W. , Sumner Malcolm E.
Published: July 2010

Nutrient imbalances, both deficiencies and excesses, are one reason for the poor acceptance of waste materials as fertilizer substitutes. Two greenhouse experiments were established using 24 different fly ashes with sewage sludge and poultry manure to estimate nutrient availability and imbalances to maize (Zea mays L.). The maximum maize growth attained with fly ash amendment of 80 Mg ha−1 was significantly less (50%) than a fertilized control treatment. The additional growth improvements obtained from mixtures with sewage sludge or poultry manure ranged from 30 to 49% and 30 to 71%, respectively. Organic materials applied alone achieved only 54 and 62% of the maximum potential, while growth on poultry manure mixtures was up to 94% of the best performing fertilized treatment. Results of foliage and soil analyses suggest that P and K were the main nutrient deficiencies, while B phytotoxicity and an imbalance in the K/Ca/Mg ratio also were likely causes of plant growth reduction. Fly ashes did not contribute significant P or K to correct soil and plant deficiencies, but more often exacerbated the imbalances by precipitation or adsorption of soil P. Sewage sludge mixed at 26% and poultry manure at 13% (DM) with fly ash had negligible effect on availability of phytotoxic fly ash B, but were good sources of P (both) and (poultry manure). Good agreement between plant nutrition in pot experiments and previous laboratory extraction studies implies that chemical analysis, efficient formulation and optimized application rates may overcome nutrient limitations for use of wastes as fertilizer substitutes.
Biodegradation and Mineralization of Atrazine in Shallow Subsurface Sediments from Illinois
Authors: Ames Rachel A. , Hoyle Blythe L.
Published: July 2010

Agricultural chemical dealerships represent potential point sources of contamination by the corn (Zea mays L.) herbicide atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine), which is frequently detected in ground water in the Midwestern USA. The objective of this study was to investigate the potential for atrazine to biodegrade under imposed N‐limited conditions in subsurface sediments collected from a contaminated former dealership in Illinois. Ten cores, 4.9 to 6.1 m deep, were obtained from four locations within the 3‐ha dealership. Forty‐four selected samples were screened in duplicate for the ability to biodegrade 21 mg L−1 atrazine in the presence of 1 g L−1 each of the C sources citrate and succinate. Although the shallow stratigraphy was fairly uniform across the site, the biodegradation of atrazine occurred predominantly in samples obtained from the southeastern corner of the site. In most of these samples atrazine was biodegraded to concentrations below detectable levels within 40 to 80 d with no detectable metabolites. In one sample from this location, indigenous bacteria mineralized 80% of applied [U‐ring‐14C]atrazine in 100 d. Sediment N and atrazine residue concentrations were not good primary predictors of the samples' ability to biodegrade atrazine. These results indicate that without knowledge of the distribution of atrazine‐degrading microorganisms, comparisons of bulk sediment parameters are useless for predicting biodegradation potential.
Isoxaben Dissipation in Field Soil as Affected by Application Timing
Authors: Chandran Rakesh S. , Derr Jeffrey F.
Published: July 2010

Timing of preemergence (PRE) herbicide application is critical for effective weed management in turfgrass and ornamentals. Information on soil dissipation, as affected by application timing and rate, is needed when using preemergence herbicides for weed control. Field studies were established at Blacksburg, VA, to determine the effect of spring, fall, and a double (spring followed by fall) application on the dissipation of isoxaben applied at 0.56, 0.84, and 1.12 kg a.i. ha−1. The half‐life of isoxaben was estimated to be 2.7 mo following spring application, 5.7 mo following fall application, and 6.1 mo following spring plus fall application. Application rate did not affect the degradation pattern of isoxaben following spring or fall application. Residues of isoxaben at 3 and 6 months after treatment (MAT) following fall application at 1.12 kg ha−1 were higher than that following spring application. A positive correlation (γ = 0.62) was determined between daily isoxaben breakdown rate and mean ambient daily temperatures following the two application timings. Degradation following fall application may be slower than that following spring application due to lower microbial activity during winter months. Negligible levels of the herbicide remained in the top 3.8 cm of soil 9 mo following spring or fall application. Double application of isoxaben resulted in higher mean levels of isoxaben residues than single spring or fall application at 0, 1, 6, and 9 MAT.
Nitrate Leaching from Grassed Lysimeters Treated with Ammonium Nitrate or Slow‐Release Nitrogen Fertilizer
Authors: Owens L. B. , Edwards W. M. , Van Keuren R. W.
Published: July 2010

Nitrate leaching is a potential in humid regions when crops and forages are fertilized. This study was conducted to compare NO3 leaching with two different N fertilizer formulations applied to forages. For 11 yr, ammonium nitrate (AN) was applied to a large (8.1 m2 surface area), undisturbed, monolithic lysimeter Y101B at an annual rate of 168 kg N ha−1, and methylene urea (MU), a slow‐release fertilizer, was applied to a similar lysimeter (Y101D) at the same rate. Nitrate‐N concentrations in the percolate from these 2.4 m‐deep lysimeters were measured weekly. Even though NO3‐N levels increased steadily with the AN applications, the greatest increases occurred during the eighth year of treatment and reached levels above 20 mg L−1. With the MU, NO3‐N concentrations remained relatively constant until after 8 yr of treatment, reaching concentrations of 6 mg L−1. The highest rates of annual NO3‐N transport in percolate were 42.3 and 12.1 kg ha−1 from lysimeters treated with AN and MU, respectively. (Losses from NH3 volatilization were measured at 12.0 and 44.8 kg N ha−1 for AN and MU, respectively.) Nitrate‐N transport in percolate varied seasonally with the greatest amounts being moved during the late winter‐early spring. Following 11 yr, the NO3‐N concentrations in each lysimeter declined to approximately 1 mg L−1. Based on this study with a 168 kg N ha−1 annual application rate, less NO3‐N leaching will occur when a slow‐release N fertilizer, such as MU, is applied to forages than when AN is applied.
Field‐Scale Study of Chlortoluron Movement in a Sandy Soil over Winter: I. Experiments
Authors: Zander Christine , Streck Thilo , Kumke Thomas , Altfelder Sven , Richter Jörg
Published: July 2010

The transport of the herbicide chlortoluron (3‐(3‐chlor‐p‐tolyl)‐1,1‐dimethylurea) was monitored in Northern Germany in a sandy soil between November 1994 and March 1995. On a 0.86‐ha grid, soil cores were taken down to a depth of 0.3 m and analyzed for total chlortoluron concentrations at 0.03‐m intervals. A bromide (Br−) transport experiment was carried out at the same site. Thirty‐three, 61, and 136 d after application, corresponding to 54, 115, and 305 mm of precipitation, chlortoluron was found almost exclusively in the upper two, four, and six layers, respectively. In these layers, coefficients of variation (CVs) varied from about 50 to >200%. At the first sampling, about 1% of applied chlortoluron was detected in the layer just above the plow‐sole. Mean travel depths of chlortoluron were distinctly more variable than those of Br−, showing no spatial correlation. The retardation factor of chlortoluron, expressing its displacement relative to that of Br−, considerably increased during the experiment, on the average from 11.5 at the first sampling to 26.3 at the third sampling. Only then, the local mean travel depths of chlortoluron showed a significant (positive) correlation with those of Br− and a significant (negative) correlation with organic C contents. Sorption kinetics of chlortoluron were investigated in laboratory sorption‐desorption (SD) experiments at 3 and 20°C. Sorption‐desorption isotherms showed pronounced hysteresis. The influence of experimental temperature was small. The collected data are intended as a basis to evaluate the ability of different modeling approaches to represent pesticide displacement at the field scale.
Dye Adsorption in a Loam Soil as Influenced by Potassium Bromide
Authors: Allaire‐Leung S. E. , Gupta S. C. , Moncrief J. F.
Published: July 2010

FD&C Blue #1 and Rhodamine WT have been used in soils to trace preferential flow paths while bromide has been used to study flow paths of water or nonretarded chemicals. This study quantified the interactions of KBr, FD&C Blue #1, and Rhodamine WT on dye adsorption in Forman loam (fine‐loamy, mixed Udic Argiboroll) soil. The experiment involved characterization of adsorption isotherms and breakthrough curves for various mixtures of tracers at different concentrations. Batch equilibration studies showed that the adsorption of FD&C Blue #1 and Rhodamine WT on Forman loam was not influenced by the presence of each other. The adsorption of FD&C Blue #1 and Rhodamine WT, however, increased with an increase in the concentration of KBr. The slope of linear adsorption isotherm (Kd) increased from 5.0 to 15.0 cm3 g−1 for FD&C Blue #1 and from 4.2 to 5.0 cm3 g−1 for Rhodamine WT on addition of 1000 mg L−1 of KBr. In a flow‐through experiment, FD&C Blue #1 movement was twice as slow in presence of KBr than in absence of KBr. The Kd values from the flow‐through experiment were lower than those from the batch equilibration experiments. We conclude that the retardation coefficients estimated from the batch equilibration studies are not realistic for application to leaching experiments, and the presence of tracer interaction can potentially complicate the interpretation of dye flow patterns observed with the use of multiple tracer technique.
Nutrient Leaching from Corn Residues under Simulated Rainfall
Authors: Schreiber J. D.
Published: July 2010

Crop residues left on the soil surface after harvest are effective in reducing erosion; however, when subjected to rainfall‐leaching, the residues are a significant source of soluble nutrients to agricultural runoff. Nutrient leaching from crop residues as a function of rainfall intensity, and residue loading rate, was studied in a series of laboratory experiments under controlled conditions. Using a multiple‐intensity rainfall simulator corn (Zea mays L.) stover placed on a nylon screen at an equivalent field loading rate of 10 t ha−1, was subjected to simulated rainfall at intensities of 6, 12, 25, 51, and 99 mm h−1. In another series of experiments, simulated rainfall was applied at 25 mm h−1 to four stover loading rates of 5, 7, 10, and 15 t ha−1. In both experiments, leachate was sampled as a function of time and analyzed for PO4‐P, NH4‐N, NO3‐N, and total organic carbon (TOC). Nutrient concentrations and losses were generally greater at the lower rainfall intensities and higher stover loading rates. In each study, nutrient concentrations decreased hyperbolically with either time or cumulative leachate volume. For all loading rates and rainfall intensities, nutrient amounts (kg ha−1) leached from the stover followed the order C ≫N = P; however, the amounts of N as (NH4‐N + NO3‐N) or C leached were ≤1.5% of total nutrient in residue compared with 2.8 to 6.0% of total nutrient in residue for P. Stover exposed to field conditions over time showed leaching kinetics similar to freshly collected residues.
Estimating Errors Associated with Extracting Phosphorus Using Iron Oxide and Resin Methods
Authors: Uusitalo Risto , Yli‐Halla Markku
Published: July 2010

Dissolution of particulate P from adhering soil material may cause an error in estimating bioavailable P with Fe oxide‐impregnated filter paper (FeO) strips and anion exchange resin (AER) bags. This error was assessed with two clayey soil samples and agricultural runoff waters high in suspended clay. Iron oxide strips were shaken either unprotected in soil suspension or enclosed in nylon mesh bags. Resin in bags and loose AER beads were used in the AER extractions. Sodium chloride and HCl extractions were compared in the displacement of P retained by the AER. Aluminum and Si served as index elements for the presence of soil material. Overestimation of desorbable P by 2.5 to 2.7 mg kg−1 for each strip was measured, compared with about 30 mg kg1 of FeO strip‐extractable P in the soils. Enclosing the FeO strips in nylon mesh bags reduced soil attachment by about 60%. The error due to dissolution of particulate P was negligible with the AER method. The FeO‐strip procedure was problematic in the water sample study. The highest P yield occurred when FeO strips were protected with nylon mesh, followed by unprotected FeO strips, AER(HCl), AER(NaCl), and loose AER beads. Overnight shaking with an unprotected FeO strip extracted 23 to 65% more P, and four sequential extractions 140 to 196% more P, than the AER(NaCl) method. In analysis of turbid water samples, the risk of overestimating P bioavailability was much lower with the AER(NaCl) method than with the FeO‐strip method.
Effect of Various Pollutants and Soil‐Like Constituents on Laccase from Cerrena unicolor
Authors: Filazzola M.T. , Sannino F. , Rao M. A. , Gianfreda L.
Published: July 2010

Laccase from Cerrena unicolor catalyses the oxidation of a wide range of aromatic compounds, either xenobiotic or naturally occurring phenols, leading to the formation of polymeric products. These are characterized by their low solubility and often may form precipitates or aggregates. The oxidizing efficiency of the enzyme is strictly dependent on the number of hydroxyl groups and the position of substituents on the phenolic molecules. During the reaction with some substrates, the enzyme is inactivated, because of possible adsorption of laccase molecules on newly formed polyphenols. By contrast, the oxidation of humic precursors (i.e., resorcinol, gallic acid, and pyrogallol) does not influence greatly the residual laccase activity. The triazinic herbicides, triazine and prometryn (2,4‐bis(isopropylamino)‐6‐methylthio‐s‐triazine), are not substrates of laccase. They, however, inhibit laccase activity assayed with 2,4‐dichlorophenol (2,4‐DCP) or catechol as substrates. The reduction of substrate oxidation rates is usually accompanied by the retention of higher levels of residual enzymatic activity. These results, together with the slight recovery in laccase activity following dialysis of the assay mixture, provide further evidence that the enzyme may be incorporated into or adsorbed onto polyphenolic products, with a consequent reduction in the concentration of active forms of laccase.
Methane Emissions of Beef Cattle Grazing Tall Fescue Pastures at Three Levels of Endophyte Infestation
Authors: Pavao‐Zuckerman Mitchell A. , Waller John C. , Ingle Teri , Fribourg Henry A.
Published: July 2010

Methane (CH4) is produced by fermentation in the rumen of cattle. Methane may play a part in global warming scenarios. Tall fescue (Festuca arundinacea Schreb.) is an important forage in the eastern United States. The toxic syndrome associated with the endophytic fungus Neotyphodium coenophialum (E+) can be mitigated with management strategies that improve forage quality of E+ tall fescue pastures and animal performance. The sulfur hexafluoride (SF6) tracer technique was used to determine the effects of tall rescue pasture management on CH4 production in 1997–1998. Two steers (Bos taurus) on two pastures each of E+ tall fescue, of endophyte free (E−) tall fescue, of E+/E−(1:1 ratio), and of E+/ladino white clover (Trifolium repens L.), and four steers and four lactating cows with nursing calves grazing either unimproved (UP) or best management practices (BMP) pastures were used to collect eructated CH4 samples. Daily CH4 emissions were about 95 to 200 g d−1 for steers and 150 to 240 g d−1 for cows. Steers grazing E+/clover pastures emitted 20% less CH4 kg−1 d−1 than steers grazing E+, E−, or E+/E− in summer. Season and animal size were the major factors affecting CH4 emissions. This first estimation of CH4 emissions from free‐roaming cattle grazing tall fescue pastures indicates that (i) improved forage management strategies have little effect on daily emissions per animal that are primarily a function of rumen size and intake, and (ii) the amount of emission per unit of animal product is reduced when improved practices are implemented.
Responses of a Nitrogen‐Saturated Forest to a Sharp Decrease in Nitrogen Input
Authors: Quist Maud E. , Näsholm Torgny , Lindeberg Johan , Johannisson Christian , Högbom Lars , Högberg Peter
Published: July 2010

The reversibility of induced N saturation was investigated in a 46‐yr‐old pine (Pinus sylvestris L.) forest in northern Sweden. Ammonium nitrate has been applied annually since 1971 to plots (30 by 30 m) at average dosages of 36 (N1), 72 (N2), and 108 (N3) kg N ha−1 yr−1, with or without P and K addition (background N deposition is <4 kg ha−1 yr−1). In 1990, after two decades of treatment, the largest N application (N3) was suspended, while N1 and N2 still received ammonium nitrate applications. Seven years after the last application in N3, the N availability measured as N concentration in plants [pine roots and needles and in leaves of the grass Deschampsia flexuosa (L.) Trin.] and activity of the enzyme nitrate reductase in leaves of D. flexuosa, and 15N uptake by excised pine roots, was at the same levels as in N1, although more than twice the amount of N has been applied in total to N3. The arginine concentrations in pine needles, concentrations of exchangeable mineral N in the organic layer, and the uppermost 20 cm of the mineral soil were at the same levels as in the control plots. Thus, an experimentally induced N excess was, according to these measurements, to a high degree reversed 7 yr after the last N application. However, the composition of the understory vegetation still differed markedly from the untreated control 8 yr after the last N3 application.