bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Land‐Applied Tertiary‐Treated Effluent on Soil Biochemical Properties
Authors: Schipper Louis A. , Williamson J. C. , Kettles H. A. , Speir T. W. 
Published: July 2010

AbstractLand application is increasingly used for the disposal and treatment of effluents. We investigated how irrigation of tertiary‐treated domestic effluent influenced 14 soil biochemical properties in a Monterey pine (Pinus radiata D. Don) forest on volcanic soils. The soils were irrigated with either effluent or water at two loading rates (49 and 74 mm wk−1). Surface soils (0–5 cm) were collected from the effluent‐irrigated and adjacent nonirrigated control sites annually for 3 yr and for 2 yr from the water‐irrigated sites. Effluent irrigation significantly (P < 0.05) increased several soil properties including pH, invertase activity, denitrification, mineralizable N, and extractable nitrate. These increases were not observed in the water‐irrigated soils suggesting that the changes resulted from effluent chemistry rather than additional water loading. Phosphatase activity decreased with both water‐ and effluent‐irrigation. No changes were observed in total N, total C, basal respiration, microbial biomass, sulfatase activity, or extractable ammonium in the effluent‐ and water‐irrigated soils. Both rates of effluent application had the same effect on soil properties indicating that the threshold rate that changed soil properties was ≤49 mm of effluent per week.
Off‐Target Deposition of Pesticides from Agricultural Aerial Spray Applications
Authors: Bird Sandra L. , Esterly David M. , Perry Steven G. 
Published: July 2010

AbstractDrift of pesticides at the times of aerial spray application is a source of concern because of potential impacts on human health, contamination of crops and livestock, and endangerment of sensitive ecological resources. A substantial body of information from field trials aimed at evaluating off‐target deposition of pesticides from aerial spray applications was analyzed. Forty‐five trials previously reported in the open literature were extrapolated and normalized and quantitatively compared to trials performed during the summer of 1992 in Plainview, TX, by the Spray Drift Task Force (SDTF). In general, the results observed in the SDTF studies are consistent with those reported in the open literature. Both sets of data show median values of pesticide deposition dropping from ∼5% of the nominal application rate at 30 m downwind to ∼0.5% at 150 m during low‐flight applications. Based on results from these trials and others reported in the literature, droplet size is consistently the primary application variable controlling off‐target drift during low‐flight applications. Application of a fine spray with a volume median diameter (VMD) <200 µm in an oil‐based carrier, typical of ultra‐low volume (ULV) applications, can yield up to a 10‐fold increase in off‐target drift, whereas use of solid stream nozzles producing a relatively coarse spray (VMD > 500 µm) can reduce drift 10‐fold relative to conventional application equipment producing a medium spray (VMD ∼300 µm). Off‐target drift increases with increasing wind speeds, but the magnitude of the effect is less significant than effects of droplet size. The SDTF trials were performed under neutral to unstable atmospheric conditions and the effects of stability for this range of conditions were not distinguishable from the effects of wind speed. In previously reported studies under a wider range of conditions, stability effects are most significant 100 m downwind and beyond with an increase in deposition of more than 10‐fold reported on occasion between unstable and very stable conditions. Currently, pesticide use labels restrict application during strongly stable atmospheric conditions and during high winds. In conjunction with these weather‐related restrictions, clear specification of nozzles and operating conditions is the best approach for effective control of off‐site drift and deposition from aerial applications.
Mitigation Alternatives to Decrease Nitrous Oxides Emissions and Urea‐Nitrogen Loss and Their Effect on Methane Flux
Authors: Delgado J. A. , Mosier A. R. 
Published: July 2010

AbstractNitrous oxide (N2O) and methane (CH4) are greenhouse gases that are contributing to global warming potential. Nitrogen (N) fertilizer is one of the most important sources of anthropogenic N2O emissions. A field study was conducted to compare N‐use efficiency and effect on N2O and CH4 flux, of urea, urea plus the nitrification inhibitor dicyandiamide (U + DCD), and a control release fertilizer, polyolefin coated urea (POCU) in irrigated spring barley (Hordeum vulgare L.) in northeastern Colorado. Each treatment received 90 kg urea‐N ha−1 and microplots labeled with 15N‐fertilizer were established. Average N2O emissions were 4.5, 5.2, 6.9, and 8.2 g N ha−1 d−1 for control, U + DCD, POCU, and urea, respectively. During the initial 21 d after fertilization, N2O emissions were reduced by 82 and 71% in the U + DCD and POCU treatments, respectively, but continued release of N fertilizer from POCU maintained higher N2O emissions through the remainder of the growing season. No treatment effect on CH4 oxidation in soils was observed. Fertilizer 15N found 50 to 110 cm below the soil surface was lower in the POCU and U + DCD treatments. At harvest, recovery of 15N‐fertilizer in the plant‐soil system was 98, 90, and 85% from POCU, urea, and U + DCD, respectively. Grain yield was 2.2, 2.5, and 2.7 Mg ha−1 for POCU, urea, and U + DCD, respectively. Dicyandiamide and POCU showed the potential to be used as mitigation alternatives to decrease N2O emissions from N fertilizer and movement of N out of the root zone, but N release from POCU does need to be formulated to better match crop growth demands.
Long‐Term Decomposition of Grass Roots as Affected by Elevated Atmospheric Carbon Dioxide
Authors: van Ginkel J. H. , Gorissen A. , van Veen J. A. 
Published: July 2010

AbstractCarbon input into the soil and decomposition processes under elevated CO2 are highly relevant for C sequestering in the soil. Plant growth and decomposition of root material under ambient and elevated atmospheric CO2. concentrations were monitored in wind tunnels. Grass roots (Lolium perenne L.) were homogeneously 14C‐labeled at 350 and 700 −L L−1 CO2 and at two N levels to obtain roots of different qualities. This root material was mixed with fresh loamy sand and transferred to four wind tunnels to observe its decomposition in bare soil and as affected by plant growth (L. perenne) at ambient CO2 and elevated CO2 for two growing seasons. After the second growing season, elevated CO2 had stimulated shoot and root growth by 13 and 92%, respectively. The CO2 and N concentrations at which the grass roots had been grown affected the decomposition rate. After the first growing season, the overall decomposition of 700 roots was 19% lower than that of 350 roots. The 14C‐labeled microbial biomass in the soil with 700 roots was higher (44%) compared with 350 roots. After the second growing season, the decomposition of 700 low N roots was 14% lower than that of 350 low N roots, whereas the decomposition of the high N roots was unaffected. The 14C‐labeled microbial biomass in the soil with 700 roots was still higher (30%) than with 350 roots. The combination of higher root yields at elevated CO2 combined with a decrease in root decomposition will lead to a longer residence time of C in the soil and probably to a higher C storage.
Understanding Phytotoxicity Thresholds for Trace Elements in Land‐applied Sewage Sludge
Authors: Schmidt J. P. 
Published: July 2010

AbstractSewage sludge contains trace elements. With repeated sludge applications as crop fertilizer, these trace elements may accumulate in the soil to phytotoxic concentrations. My objective was to assess the scientific basis for the current cumulative loading limits for Cu, Ni, and Zn in land‐applied sewage sludge. An overview of the USEPA's phytotoxicity risk assessment, the basis for these loading limits, was presented, discussed, and compared in the context of the underlying principles of phytotoxicity thresholds. I concluded that EPA phytotoxicity thresholds in immature plants were arbitrarily selected, and extrapolations to field applications of sewage sludge were not substantiated. Variability in plant accumulation rates and soil sorption capacities of trace elements were not adequately considered in the EPA analysis. Because of the assumptions, simplifications, and extrapolations introduced into the phytotoxicity analysis, the final results, that is, EPA's cumulative loading limits for Cu, Ni, and Zn, are not substantiated by the analysis. The phytotoxicity analysis does not represent an appropriate application of underlying scientific principles. A more appropriate basis for regulating trace element applications in sewage sludge would reflect an understanding of site‐specific characteristics, possibly including concentration limits for trace elements in plant tissue, soil, and/or groundwater. Additional research would be required to substantiate EPA's conclusions about the cumulative pollutant loading limits, as derived from EPA's phytotoxicity risk assessment.
Soil Microorganisms in Soil Cleanup: How Can We Improve Our Understanding?
Authors: Holden Patricia A. , Firestone Mary K. 
Published: July 2010

AbstractSuccessful in situ biodegradation must depend on microbial catalysis as well as physical transport. While there has been much effort directed toward understanding vadose zone transport processes, our understanding of the microbial ecology of the indigenous catalysts limits our ability to manage biodegradation processes in soil. The environmental factors commonly listed as controlling in situ biodegradation are water, oxygen, redox potential, nutrients, pH, and temperature. Simplistic statements concerning the environmental determinants of in situ biodegradation may reflect a naive understanding of microbial ecology and may in fact direct management efforts in inappropriate directions. We discuss what we need to know about soil microbial ecology to elevate in situ biodegradation to a reliable and well‐understood remediation option. We need to know the following: What controls the presence of the desired metabolic capability; the distribution of degrading communities relative to contaminant source; and what controls activities of relevant communities?
Heavy Metal Displacement in a Sandy Soil at the Field Scale: I. Measurements and Parameterization of Sorption
Authors: Streck Thilo , Richter Jörg 
Published: July 2010

AbstractDownward displacement of cadmium (Cd) and zinc (Zn) at the field scale was investigated in a sandy soil irrigated under controlled conditions for 29 yr with a total of 12.8 m3 m−2 of municipal wastewater. On a 0.86 ha grid a total of 720 samples was taken from 0 to 1.2 m depth. Cadmium and Zn contents were determined in all samples by extraction with 0.025 M ethylene‐diamine‐tetra‐acetic acid (EDTA) on the assumption that this fraction represents the solution and sorbed phases in soil. Solution phase concentrations of 480 samples were estimated by equilibrating the samples with 0.0025 M CaCl2. Heavy metal downward displacement is spatially highly variable. Five percent of EDTA‐extractable Cd and Zn were found below 0.7 and 0.9 m depth, respectively. Spatial variability of heavy metal load as measured by recovered mass per unit area reflects the geometry of irrigation systems employed. Measured sorption equilibria could be well described as a function of organic C content and pH by extending the Freundlich equation.
Boric and Silicic Acid Adsorption and Desorption by a Humic Acid
Authors: Meyer Michael L. , Bloom Paul R. 
Published: July 2010

AbstractBoron is an essential plant nutrient having a narrow range between concentrations that cause deficiency or toxicity symptoms in plants. Boric acid (B[OH]3) and silicic acid (Si[OH]4) have many chemical similarities and both are thought to be associated with organic matter in soils. The objectives of this study were to investigate the variation in boric and silicic acid adsorption and desorption in low ash humic acid over a range of B and Si concentrations and pH values. Borate adsorption by humic acid increased significantly from pH 3.67 to 8.70. The data fit the Freundlich equation better than the Langmnir model at high pH; however, both fit well at pH < 7. Adsorption was greatest at pH 8.5 to 10 and decreased at pH >10. The constant capacitance model predicted B adsorption and the pH maximum using catechol as the adsorbing ligand and published stability constants. The predicted adsorption envelope was narrower than experimental data. This could be due to variation in stability constants that result from variation in substitution on other sites on the aromatic ring. Inclusion of glucose and salicylate in the adsorption model would also broaden the adsorption envelope by increasing adsorption at pH > 9 and < 9, respectively. Desorption of B from humic acid appears to show hysteresis effects at pH 7.6 but not at pH 8.15 and 8.7. Generally, B will be easily released from HA as solution concentrations decrease. Silicic acid did not adsorb in humic acid. The stability constant of Si‐catechol humate complexes is apparently too low for adsorption of Si to occur at the pH and solution concentrations used in this experiment.
Pig Slurry Amendment and Herbicide Coapplication Effects on s‐Triazine Mobility in Soil: An Adsorption‐Desorption Study
Authors: Businelli Daniela 
Published: July 2010

AbstractAmendments with pig slurry containing dissolved organic matter (PSDOM) and herbicide coapplication are agronomical practices that can influence the mobility of herbicides through the soil profile, thus enhancing the risk of groundwater pollution. Batch equilibrium experiments were conducted on a clay loam soil to quantify the influence of these practices on the sorption and desorption of three s‐triazine herbicides: atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐l,3,5‐triazine), prometryn (2,4‐bis (isopropylamino)‐6‐methylthio‐1,3,5‐triazine), and terbuthylazine (2‐tert‐butylamino‐4‐chloro‐6‐ethylamino‐ 1,3,5‐triazine). Soil adsorption and desorption capability for atrazine was reduced when it was applied with the other two s‐triazines in the batch experiment solution. The PSDOM treatment immediately after atrazine application had a greater enhancing effect on its desorption than treatment with a 0.01 M CaCl2 solution alone. No enhanced desorption effect was observed on any of the three s‐triazines when PSDOM treatment was carried out after repeated 0.01 M CaCl2 treatments. Soil treatment with PSDOM before atrazine application enhanced soil adsorption capability for the herbicide. On calculating the balance between the adsorbed and desorbed atrazine in the PSDOMtreated soil, a fourfold increase of the atrazine retained was observed. Therefore, to reduce the risk of groundwater s‐triazine pollution, pig slurry should be applied to the soil before herbicide treatment.
Spatial Variability of Throughfall in a Subtropical Rain Forest in Taiwan
Authors: Lin Teng‐Chiu , Hamburg Steven P. , King Hen‐Biau , Hsia Yue‐Joe 
Published: July 2010

AbstractEight rainfalls were intensively sampled in a subtropical rain forest in northeastern Taiwan. This study, carried out at Fu‐shan Experimental Forest was designed to examine variability of throughfall characteristics. The volume and chemistry of the throughfall associated with individual rains have a high degree of spatial variability, with throughfall chemistry more variable than volume. When data from all of the storms were combined, there was lower variability than that seen with individual storms, largely as a result of a lack of consistent storm to storm spatial variation. Thus, individual storms cannot be used to represent the seasonal or annual pattern of spatial variation in throughfall chemistry or volume of the study forest. Twenty samples were required to estimate throughfall volume within 10% of the population mean with 95% confidence for individual storms. Yet, more than 100 samples were required to estimate the throughfall chemistry of some ions (e.g., H+). When the data from all eight storms were combined, 7, 20, and 25 samples were necessary to estimate throughfall volume, ion concentrations, and ion fluxes (except for Mg2+ and H+) within 10% of the population mean with 95% confidence. In the absence of estimates of spatial variation, differences in sampling protocols among throughfall studies make comparisons of throughfall characteristics difficult. In this study three funnels were used in tandem to capture small scale variability at each sample location, thus reducing spatial variability of throughfall chemistry.
Fate of Carbon‐14 Diazinon during the Composting of Yard Trimmings
Authors: Michel Frederick C. , Reddy C. Adinarayana , Forney Larry J. 
Published: July 2010

AbstractThe fate of lawn care pesticides during the composting of yard trimmings is largely unknown. In this study we investigated the fate of diazinon (0,0‐diethyl 0‐[2‐isopropyl‐6‐methyl‐4‐pyrimidinyl] phosphorothioate), the most widely used lawn care pesticide, during the composting of a mixture of leaves and grass (2:1 w/w). The yard trimmings were amended with [Δ‐2‐14C] labeled diazinon (10 mg kg−1 wet wt.) and composted in a laboratory scale compost system for 54 d. During composting, 48% of the initial total organic matter (OM) was lost as CO2, the pH increased from 6.2 to 8.2, the oxygen uptake rate declined from 3.5 to 0.09 (mg O2 g OM−1 h−1), the humification index dropped from 1.0 to 0.37, and 11% of the 14C‐diazinon was mineralized to 14CO2. Initially most of the added 14C‐diazinon was ether extractable (83%) but <1% was ether extractable after composting. A water extract of the finished compost contained 36% of the added 14C. Thin layer chromatography and mass spectrometry analyses of this water extract indicated that the 14C was in the form of 2‐isopropyl‐6‐methyl 4‐hydroxy pyrimidine (IMHP) a hydrolysis product of diazinon. The remaining 14C was either unextractable (32%), or was associated with a high molecular weight fraction of a 0.1M NaOH/Na4P2O7 extract of the finished compost (19%). Volatilization of diazinon was negligible (0.2%). The results show that during the composting of yard trimmings, a relatively small amount of diazinon is mineralized to CO2, while a majority of the diazinon is converted to potentially leachable, but less toxic IMHP, high molecular weight residues, and unextractable residues that are presumed to have low bioavailability.
Kinetics of Cadmium Release from Soils as Influenced by Organic Acids: Implication in Cadmium Availability
Authors: Krishnamurti G. S. R. , Cieslinski G. , Huang P. M. , Van Rees K. C. J. 
Published: July 2010

AbstractThe low‐molecular‐weight organic acids (LMWOAs) secreted by plant roots modify the mobility of Cd through formation of soluble complexes in the soil rhizosphere; the kinetics of Cd release as influenced by organic acids and its impact on Cd bioaccumulation remains to be established. The influence of LMWOAs (10−3 and 10−2 M), viz., acetic, citric, oxalic, fumaric, and succinic acids, which are present in the soil rhizosphere, on the kinetics of Cd release from selected soils (Luseland, Waitville, and Jedbergh) of Saskatchewan, Canada, was investigated at 25°C and at an ionic strength of 0.1 M NaNO3. It was observed that the Cd release from the soils increased initially up to a reaction period of about 2 h and then slowly decreased with time. With time, the LMWOAs were apparently microbially degraded and the soil solution Cd2+, which was transformed from the Cd‐LMWOA complexes by microbial degradation, was adsorbed onto the negatively charged soil particles. Increasing amounts of Cd were released from the soils to the soil solution with the renewal of LMWOAs after every 2 h. The short‐term (reaction period of 0.25 to 1 h) kinetics of Cd release from the soils was described by a parabolic diffusion kinetic model. The overall diffusion coefficient of the Cd release from the soil and the Cd released by the renewal of LMWOAs followed the same trend as the Cd availability index of the soils: Luseland >> Waitville > Jedbergh. Thus, the results presented in this investigation indicate the importance of the kinetics of the Cd release from the soils by the LMWOAs excreted by root exudates in understanding the availability of soil Cd.
Identification of Coniferous Forests with Incipient Nitrogen Saturation through Analysis of Arginine and Nitrogen‐15 Abundance of Trees
Authors: Näsholm Torgny , Nordin Annika , Edfast Ann‐Britt , Högberg Peter 
Published: July 2010

AbstractStands of Norway spruce [Picea abies (L.) Karst.] differing in throughfall N deposition and NO3− leaching were investigated to determine if arginine concentrations and δ15N abundances of needles could be used to predict NO3− leaching from stands. Twenty‐three stands, all located in southern Sweden, were sampled and five of these had average NO3− concentrations > 0.1 mg NO3−‐N L−1 in soil water at a 50‐cm depth. Arginine concentrations and δ15N abundances of needles were significantly higher for sites that exhibited NO3− leaching. The δ15N enrichment (ε), i.e., difference between foliage and soil organic matter in δ15N, showed less variation than δ15N of needles alone in regressions against NO3− leaching and was, thus, a better predictor of leaching. All sites that exhibited N leaching had arginine concentrations > 5 µmol g dw−1 and ε > −0.5 (‰) and thus, there was strong correlation between arginine and ε values. To test if arginine accumulation, as such, can affect the δ15N of needles, arginine and δ15N were determined for Scots pine (Pinus sylvestris L.) trees given different amounts of N fertilizer. Although fertilization caused a dramatic increase in arginine concentrations of needles, no immediate change in δ15N was observed. A hypothesis is proposed to explain the causal linkage between elevated arginine and δ15N of needles and leaching of N. Thus, arginine accumulation in trees corresponds to decreased uptake rates of NH4+ leaving NH4+ ions available for nitrification. During nitrification, discrimination against the heavier takes place resulting in a depleted NO3− pool and enriched NH4+ pool. Preferential uptake of NH4+ by conifer trees will then lead to elevated 15N abundance of needles. It is concluded that N leaching coniferous forests can be identified through analysis of arginine and δ15N of needles.
Laboratory‐Scale Measurements and Simulations of Effect of Application Methods on Soil Methyl Bromide Emission
Authors: Gan J. , Yates S. R. , Spencer W. F. , Yates M. V. , Jury W. A. 
Published: July 2010

AbstractMethyl bromide (bromomethane, MeBr), which originates from the oceans, fumigation, and a few other sources, is reportedly contributing to the ozone depletion in the stratosphere. Due to the heavy reliance on this fumigant in the production of many crops, it is of particular importance to accurately quantify the atmospheric input of MeBr arising from agricultural uses, and develop feasible measures to minimize these emissions. In this study, we determined the effect of two important application variables, surface tarp and injection depth, on MeBr transport and transformation in the soil and its emission from the soil surface under controlled conditions. Following 20‐ and 30‐cm injections, covering the soil surface with 1‐mil (0.025 mm) high‐density polyethylene film resulted in an average of 48% reduction in MeBr emission. Increasing the injection depth from 20 to 60 cm caused a decrease in MeBr emission of 54% under untarped conditions and 40% under tarped conditions. The influence of application methods on MeBr atmospheric emissions should be considered when estimating the contribution of agricultural fumigation to the overall atmospheric MeBr burden on a global scale. The results also indicate that MeBr emission after soil fumigation may be substantially minimized by using surface tarpaulins and deep injections.