bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rates of Selenium Volatilization among Crop Species
Authors: Terry Norman , Carlson C. , Raab T.K. , Zayed Adel M. 
Published: July 2010

AbstractThe rate of Se volatilization per plant was measured for 15 crop species grown hydroponically (for 18–48 d depending on the species) in growth chambers. Selenium was supplied as 20 micromolar sodium selenate in 0.25 strength Hoagland's solution. Selenium volatilization was determined by enclosing plants in a Plexiglas plant chamber and trapping the volatile Se emissions in alkaline peroxide traps. The results show that rice (Oryza sativa L.), broccoli (Brassica oleracea botrytis L.), and cabbage (Brassica oleracea capitata L.) volatilized Se at the fastest rates, i.e., 200 to 350 µg Se per m2 leaf area per day (1500–2500 µg Se kg−1 plant dry wt. d−1). Carrot (Daucus carota L.), barley (Hordeum vulgare L.), alfalfa (Medicago sativa L.), tomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativus L.), cotton (Gossypium hirsutum L.), eggplant (Solanum melongena L.), and maize (Zea mays L.) had intermediate rates of 30 to 100 µg Se m−2 d−1 (300–750 µg Se kg−1 d−1). Sugarbeet (Beta vulgaris L.), bean (Phaseolus vulgaris spp.), lettuce (Lactuca sativa L.), and onion (Allium cepa L.) had the lowest rates, i.e., less than 15 µg Se m−2 d−1 (<250 µg Se kg−1 d−1). Comparing all plant species, Se volatilization rate was found to be highly correlated with Se concentration in plant tissues; we suggest that the ability of plants to absorb Se may be an important factor contributing to high rates of Se volatilization.
Lime Effects on Pine Forest Floor Leachate Chemistry and Element Fluxes
Authors: Marschner Bernd , Stahr Karl , Renger Manfred 
Published: July 2010

AbstractIn a 30‐mo field study, element inputs with throughfall and litter and leachate outputs from forest floor lysimeters were monitored in a control and a limed + K/Mg‐fertilized plot in a 40‐yr‐old pine plantation on a Cambic Arenosol. In the control, input‐output budgets show the retention of most elements, which probably is a natural phenomenon in this young ecosystem and not caused by inhibitory effects of anthropogenic inputs on decomposition processes. Despite the high Ca status of the forest floor, the H+ inputs of 70 to 90 mmolc m−2 yr−1 are buffered only to a small degree (0–30%). Internal H+ production from dissociation of organic acids and N transformations contributes up to 130 mmolc m−2 yr−1 to the acid load in the leachates. As a result, Zn and Cd are mobilized from the forest floor. In the limed plot, the applied K and Mg sulfates were washed out quantitatively within 1 yr. Due to the high solubility of the chalk‐lime, leachate Ca concentrations rose sharply and pH increased from 4.0 in the control to over 6, showing that acid from inputs and from internal production was almost completely neutralized. After a partial N immobilization in the 1st yr, total mineral N outputs were similar in both treatments. But in the limed lysimeters, the degree of nitrification in the leachates reached 85 to 95% compared to 30 to 55% in the control, which has consequences for N availability and for N leaching in the mineral soil. The retention of Cd and Zn was greatly increased by the treatment and reached 60 and 30% of total inputs, respectively.
Competitive Adsorption of Para‐Xylene and Water Vapors on Calcium, Sodium, and Lithium‐Saturated Kaolinite
Authors: Pennell K.D. , Rhue R.D. , Hornsby A.G. 
Published: July 2010

AbstractVapor‐phase adsorption of volatile organic chemicals (VOC) on soils and clay minerals has been shown to be greatly reduced in the presence of water. Exchangeable metal cations are known to interact strongly with water, and thus may influence the competitive adsorption of water and organic vapors. Flow‐equilibration experiments were conducted to measure the concentration of water and p‐xylene vapors adsorbed on oven‐dried Ca‐, Na‐, and Li‐saturated kaolinite from single and binary vapor systems. Li‐saturated kaolinite adsorbed significantly less water than Ca‐ and Na‐kaolinite. This was attributed to a 50% reduction in cation exchange capacity (CEC) of Li‐kaolinite following heating at 110°C. The adsorption of p‐xylene vapors on Ca‐, Na‐, and Li‐kaolinite at 0% relative humidity (RH) was also related to the CEC and exchangeable cation species, which suggests that specific interactions occurred between exchangeable cations and p‐xylene molecules. When the RH was increased to 10 and 20%, p‐xylene adsorption decreased in small, but successive, increments. The competitive adsorption of both water and p‐xylene on Ca‐, Na‐ and Li‐kaolinite was underestimated by two‐component adsorption equations based on the Brunauer, Emmett, and Teller (BET) model. At low RH's, water adsorption on kaolinite was hypothesized to occur primarily at cation exchange sites, allowing for the continued adsorption of p‐xylene on exposed mineral surfaces. Thus, the assumption of complete monolayer coverage prior to the onset of multilayer formation, upon which the BET model is based, may limit the ability of these equations to accurately predict the competitive adsorption of polar and nonpolar vapors.
Modeling Soil Sulfate Sorption Characteristics
Authors: Comfort S.D. , Dick R.P. , Baham J. 
Published: July 2010

AbstractKnowledge of soil SO4 adsorption characteristics is required for predicting the fate of atmospheric S depositions on terrestrial ecosystems. This study developed two models for predicting the SO4 sorption characteristics of field moist soils from routinely measured soil physical and chemical properties. Sixty‐two soil samples from the U.S. Northeastern (NE) and Southern Blue Ridge Province (SBRP) regions were used in model development. The first modeling approach used stepwise multiple regression to identify which combinations of soil properties best predicted each Langmuir constant. The Langmuir constant regression equations were then substituted back into the Langmuir model and used to predict SO4 sorption for each equilibrium SO4 concentration. This approach described SO4 sorption reasonably well for both regions (R2 of 0.57–0.89). In the second approach, a better fit of SO4 sorption was achieved (R2 of 0.81–0.92) using fewer soil properties by expressing the Langmuir constants as linear functions of selected soil properties and directly estimating the soil property coefficients by nonlinear regression. Soil properties used in the second model included: dithionite‐citrate‐extractable Al (Ald), total organic C (TOC), and extractable SO4 for the NE region; and Ald, TOC, clay content, pH, and CEC for the SBRP region. These results indicated that regional soil SO4 sorption characteristics could be predicted for field moist soils with the knowledge of only a few routinely measured soil properties.
Sorption‐Desorption Kinetics of Alachlor in Surface Soil from Two Soybean Tillage Systems
Authors: Locke Martin A. 
Published: July 2010

AbstractAlachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)‐acetamide] sorption patterns were evaluated in surface (0–5 cm) Dundee silt loam (fine‐silty, mixed, thermic Aeric Ochraqualf) soil collected from long‐term conventional tillage (CT) and no‐tillage (NT) soybean [Glycine max (L.) Merr.] plots. Three concentrations of [14C] alachlor (0.58, 2.44, and 18.1 µmol L−1) in 0.01 M CaCl2 were added to soil (3 g/18 mL) and samples were shaken for time periods ranging from 1 min to 96 h. The difference between initial and final alachlor concentration was attributed to sorption. Desorption (0.01 M CaCl2) was measured for samples initially sorbed for 1, 24, or 96 h. Desorbed soils were extracted with methanol and then combusted. Freundlich parameters (Kf [1/n]) were calculated for alachlor sorption and desorption using nonlinear regression. Sorption Kf values for soil from both tillage systems increased as sorption shaking time increased. Desorption was hysteretic, and length of sorption shaking increased non‐singularity. Sorption Kf values measured for NT were greater than CT for each of the 1, 24, and 96 h sorption shaking times. Similarly, desorption Kf values for NT were greater than for CT. Kinetics were evaluated using a three‐site model. Sorption patterns indicated rapid initial sorption up to approximately 3 h followed by slower sorption. No change in solution alachlor was observed after 48 h for either tillage treatment. Labile and restricted fractions increased with time, especially for NT. The increased rate and overall quantity of alachlor sorption in NT was attributed to higher soil organic residues.
Water Quality Impacts Associated with Pre‐ and Postemergence Applications of Atrazine in Maize
Authors: Pantone D.J. , Young R.A. , Buhler D.D. , Eberlein C.V. , Koskinen W.C. , Forcella F. 
Published: July 2010

AbstractHerbicide contamination in surface runoff varies greatly depending on the herbicide management alternatives used. This study was conducted to determine if herbicide runoff is influenced by the timing of herbicide application with respect to maize (Zea mays L.) emergence. Preemergence (PRE) and postemergence (POST) applications of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] were compared during 1988 and 1989 on a field with no prior history of atrazine use on a Barnes loam (fine‐loamy, mixed Udic Haploboroll) soil at the Swan Lake Research Farm near Morris, MN. A rainfall simulator applied precipitation events of 50 min with an intensity of 64 mm h−1 on Days 1,7, and 30 after PRE or POST applications of atrazine. Rainfall 1 d after application resulted in 32 g ha−1 of atrazine (less than 2% of the amount applied) in the runoff water and sediment for PRE treatments compared with 16 g ha−1 (less than 1% of the atrazine applied) for POST treatments. Similarly, 7 d after the herbicide applications, 20 g ha−1 was lost with PRE treatments and 1 g ha−1 for POST treatments. At 30 d, PRE treatments resulted in 8 g ha−1 being transported in the water and sediment compared with 1 g ha−1 for POST treatments. The rate of surface runoff, rather than the concentration of herbicide in the runoff, was the critical factor responsible for the reduction of the quantity of atrazine in the surface runoff with the POST treatments as compared with the PRE treatments.
Coupling Groundwater Contamination with Economic Returns When Applying Farm Pesticides
Authors: Hoag Dana L. , Hornsby Arthur G. 
Published: July 2010

AbstractA methodology is presented that permits simultaneous consideration of the economics of production and groundwater contamination hazard of pesticide use. An example is constructed for weed control in soybean (Glycine max L.) production at Clayton, NC. A cost/groundwater hazard frontier is developed that can be used to identify and illustrate the cost tradeoffs of selecting alternative weed control strategies that reduce the risk of adverse health effects from drinking contaminated groundwater. The methodology relies on models to estimate costs, crop yields, pest competition, and leaching of pesticides; thus, its applicability depends on availability of local data and appropriately validated models for the site considered. The cost/groundwater hazard frontier provides a useful decision aid to assist pesticide users in making cost‐effective and environmentally favorable production decisions. It is also useful in evaluating policy or the value of new pest control technologies, as it indicates a farmer's ability to substitute alternatives for currently used practices.
Nitrogen Outputs from a Field‐Size Agricultural Watershed
Authors: Lowrance Richard 
Published: July 2010

AbstractNitrogen outputs from a 0.34‐ha field were measured for 1984 through 1987. The field consisted of Cowarts loamy sand (fine‐loamy, siliceous, thermic Typic Hapludult) managed in a summer row crop‐winter cover crop sequence. Outputs measured were subsurface flow, surface runoff, and denitrification. Monthly sampling of denitrification rates showed a high degree of temporal and spatial variability. Rates significantly increased with soil moisture and depth. Denitrification also increased after irrigation events. Nitrogen movement in subsurface flow was 97% NO3‐N and was about 10 times that in surface runoff. Most subsurface flow and movement of N (77 kg NO3‐N ha−1) occurred in December 1986 through February 1987 when 62 cm of precipitation fell in a 12‐wk period (December 1986–February 1987) following fertilizer application. This period accounted for one‐half the total subsurface nitrate movement for the 4‐yr study. Even though no crop was harvested in 1985, subsurface outputs of N were low in winter of 1985–1986. Soil NH4‐N levels were significantly higher after the year without a harvest, indicating that more of the N in crop residue was found in the soil pool.
Nitrate Dynamics in Riparian Forests: Microbial Studies
Authors: Groffman Peter M. , Gold Arthur J. , Simmons Robert C. 
Published: July 2010

AbstractWhile riparian forests have a demonstrated ability to remove nitrate (NO−3) moving from uplands before it enters streams, there is considerable uncertainty as to the mechanisms of NO−3 removal in these areas. We characterized spatial and temporal variation in denitrification enzyme activity (DEA), microbial biomass C and N content, soil respiration and potential net N mineralization and nitrification in three riparian forest sites consisting of soil catenas containing moderately well, somewhat poorly, poorly, and very poorly drained soils (inceptisols and entisols). These measurements were made in conjunction with studies of NO−3 removal from groundwater during growing and dormant seasons that are reported in a companion paper. Two of the sites were on stratified glacial drift, one with an undeveloped upland and one with an upland with high density unsewered residential development that produced groundwater at the edge of the riparian zone with NO−3‐N concentrations between 8 and 12 mg/L The third site was on unstratified glacial drift with an undeveloped upland. Hydric surface (0–15 cm) soils (poorly and very poorly drained) consistently had higher DEA than upland‐wetland transition zone (moderately well and somewhat poorly drained) surface soils. Spatial patterns of microbial biomass C and N content were more variable but showed the same general pattern as DEA. Levels of DEA and microbial biomass were consistently low or undetectable at and below the seasonal high water table. Surface soil DEA and microbial biomass were correlated with NO−3 removal from groundwater during the growing season. Low levels of DEA and microbial biomass in the subsurface however, suggested that plant uptake was the dominant groundwater NO−3 sink during the growing season. During the dormant season, water table levels were higher and groundwater‐borne NO−3 was able to interact with near surface soil and be removed by denitrification and/or microbial immobilization. Potential net N mineralization was quite variable both within and between sites, while potential net nitrification was very low at most sites. A notable exception was in the transition‐zone soils at the stratified drift site with a densely developed upland, which had relatively high rates of net NO−3 production. The high nitrification rates observed at this site may suggest that the long‐term buffering potential of this site is limited.
Spatial and Temporal Variability of Carbofuran Degradation in Soil
Authors: Parkin T.B. , Shelton D.R. 
Published: July 2010

AbstractLoss of pesticide efficacy resulting from enhanced rates of microbial degradation has been observed with several pesticides including the insecticide carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate). Soils in which this phenomenon occurs are often referred to as “problem soils.” Several previous studies have documented the temporal aspects of the conversion of a nonproblem soil to a problem soil, and have compared carbofuran degradation rates in problem vs. nonproblem soils. There have been few studies of the spatial or temporal variability of pesticide degradation, and no studies of the variability of carbofuran degradation, however. Our study was designed to evaluate the spatial variability of carbofuran degradation activity in a conventional‐till and a no‐till corn (Zea mays L.) field, and to assess temporal variations of carbofuran degradation activity. Soil samples were collected at two positional locations in each field (in‐row and between‐row) at three times during the growing season. Within the planting furrow, maximum rates of carbofuran degradation were higher and resulting half‐lives of carbofuran (DT‐50%) were lower than in samples collected between corn rows. Interactive effects of both microbial biomass and soil water content appeared to contribute to the observed differences in carbofuran degradation kinetics as well as to the positional differences observed. Temporal variations in carbofuran degradation appeared to be dominated by soil water content. At this time it remains unknown whether the observed increase in carbofuran degradation activity, in the row, occurred in response to the banded application of carbofuran, or to increased C availability in the rhizosphere.
Effect of pH on Sorption and Desorption of Imazaquin and Imazethapyr on Clays and Humic Acid
Authors: Che M. , Loux M. M. , Traina S. J. , Logan T. J. 
Published: July 2010

AbstractThe interaction of imazaquin (2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐3‐quinolinecarboxylic acd) and imazethapyr ((±)‐2‐4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐5‐ethyl‐3‐pyridinecarboxylic acid) with clay suspensions and humic acid was studied using a batch equilibrium method and by fluorescence emission spectroscopy. The objectives of this study were to: (i) determine the effect of different sorbents and pH on the sorption of imazaquin and imazethapyr, and the hysteresis in adsorption‐desorption isotherms, and ii) evaluate the effect of pH on the mechanisms of imidazolinone herbicide sorption by specimen hectorite. Sorption of both herbicides increased as pH decreased, but the increased sorption was most evident as soil pH decreased from 5 to 3. Illite and kaolinite, which exhibit more pH‐dependent charge characteristics and less total surface area than hectorite, can impart important adsorptive character to soil, especially with regard to imazethapyr. Humic acid had much greater affinity for both herbicides than clay did, indicating that organic matter content could be a major factor controlling the sorption of these herbicides in soils. The rate of desorption varied among absorbents and between herbicides; imazethapyr desorbed more readily than imazaquin from most adsorbents. The results of fluorescence emission spectroscopy indicated that imazaquin and imazethapyr molecules were protonated and sorbed on the clay surface under acidic conditions. The extent of protonation was greater in the clay suspensions than in clay‐free solutions.
Organic and Inorganic Amendments to Reduce Ammonia Losses from Liquid Hog Manure
Authors: Al‐Kanani T. , Akochi E. , MacKenzie A. F. , Alli I. , Barrington S. 
Published: July 2010

AbstractLiquid hog manure (Sus scrofa domesticus) is in common use as a fertilizer or a soil conditioner in agricultural production. Liquid hog manure (LHM) suffers from N loss through volatilization of ammonia (NH3), however. Reduction of NH3 loss from 4% total solids LHM was studied using added Sphagnum peat moss (Sphagnum fuscum peat), sulfuric acid, phosphoric acid, monocalcium phosphate monohydrate (MCPM), elemental S, and calcium carbonate. Cumulative losses of NH3‐N ranged between 0 and 711 mg N kg−1 LHM applied. Elemental Sulfur and calcium carbonate (CaCO3) treatments induced greater NH3 losses compared with the nonamended LHM, whereas acidic treatments including Sphagnum peat moss (SM) reduced NH3 losses by at least 74.6%. Volatilization of NH3 from LHM increased as the pH of amended LHM treatment increased. The relationships between cumulative (15 d) NH3 volatilized and initial pH of amended LHM varied, depending on the amendment. The nutrient values of amended LHM stored for 25 d under continuous aeration were assessed on two soils mapped as Chicot (fine loamy, mixed, nonacid, mesic Typic Hapludoll) and Uplands (coarse loamy, mixed, nonacid, Typic Haplorthod) from eastern Canada. Treatment of LHM with SM at greater than 1% (w/w) reduced NH3 volatilization. Added CaCO3 increased NH3 loss. In general, amendments did not reduce effectiveness of LHM‐N for barley (Hordeum vulgare L.) growth. An exception was the 1% SM + 2% CaCO3 amendment that reduced plant growth.
Wastewater Renovation in Buried and Recirculating Sand Filters
Authors: Gold A.J. , Lamb B.E. , Loomis G.W. , Boyd J.R. , Cabelli V.J. , McKiel C.G. 
Published: July 2010

AbstractA replicated, multiyear field study was conducted to assess the reduction of N, P and microbial indicators by a recirculating sand filter (RSF) and buried multilayer sand filter patterned after the RUCK filter. The RSF's received 38 L m−1 d−1 of septic tank effluent, while the buried sand filters were loaded at 76 L m−2 d−1. The RSF's had significantly greater reductions of N and P (21 and 31%, respectively) than the buried filters (8 and 1%, respectively); however, reduction was not significantly different per unit area. The lower daily loading rate and even distribution of effluent on the recirculating filters may have contributed to the elevated P reductions noted. Total Kjeldahl N (TKN) reductions in the RSF's were markedly lower during the cold season (≤ 10 °C) than the warm season. In contrast, TKN reductions in the buried sand filters were relatively constant, except during the coldest periods of winter. Substantial TKN reductions occurred under acidic conditions. During warm weather sampling, both types of filters dramatically reduced levels of fecal coliform, enterococci, and F male‐specific bacteriophage. During cold conditions, the buried sand filters produced greater reductions of fecal coliforms and enterococci levels, while neither filter consistently reduced the levels of Clostridium perfringens or F phage. Increased reductions in fecal coliform, enterococci and F phage were associated with lower effluent pH for both sand filters.