bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorus Concentrations in Drainage Water in the Everglades Agricultural Area
Authors: Izuno F. T. , Sanchez C. A. , Coale F. J. , Bottcher A. B. , Jones D. B.
Published: July 2010

Phosphorus in drainage water leaving the Everglades Agricultural Area (EAA) in southern Florida is alleged to be contributing to the accelerated eutrophication of Lake Okeechobee and the degradation of the Water Conservation Areas and the Everglades National Park ecosystems. Agricultural “best management practices” (BMPs) offer a means for achieving reductions in P in drainage water. Prior to developing and implementing BMPs, it is necessary to establish baseline EAA P concentrations. Baseline total P (TP) and total dissolved P (TDP) concentrations for various crop and field conditions in the EAA were determined. Thirty‐six 0.7‐ha plots were installed at four locations. Average TP and TDP concentrations were derived from 6 to 30 drainage events for each of five conditions between November 1988 and December 1989: sugarcane (Saccharum spp.), radish (Raphanus sativus L.), and cabbage (Brassica oleracea L.) production fields, flooded fallow fields, and drained fallow fields. Baseline TP and TDP concentrations for main farm canals and rainfall were also determined. Average TP concentrations ranged from 0.25 mg L−1 for radishes to 1.03 mg L−1 during the drain‐down of flooded fallow plots. Total dissolved P concentrations ranged from 48 to 80% of TP. Main farm canal TP concentrations averaged 0.16 mg L−1. Total P concentrations in rainfall averaged 0.07 mg L−1 Total P in drainage water during 1989 for sugarcane, cabbage, and drained fallow fields were 0.72, 1.38, and 0.59 kg ha−1, respectively. During the radish season, drainage water TP loading was 0.8 kg ha−1. Flooded fallow fields after radishes yielded a TP loading rate of 3.82 kg ha−1. Total P loading to the fields from rainfall averaged 0.70 kg ha−1. Total dissolved P loading rates ranged from 25 to 60% of TP. Potential areas for BMP development and implementation for P concentration and loading reduction in the EAA include drainage rate, volume, and timing management, fertilizer use reduction, and enhanced crop rotation strategies.
Bacterial Pollution of Waters in Pristine and Agricultural Lands
Authors: Niemi R. M. , Niemi J. S.
Published: July 2010

Concentrations of thermotolerant coliform bacteria, presumptive E. coli, and presumptive fecal streptococci were determined from ditches, brooks, and natural ponds in six agricultural areas and 22 uninhabited pristine areas in southern Finland in the summer of 1987. For comparison, the same fecal indicators were enumerated from the effluents of three wastewater treatment plants. The objective was to compare the importance of these waters as sources of fecal indicators in receiving waters. The numbers of bacteria in waters in agricultural areas often exceeded the limit of acceptable swimming water (1000 bacteria per 100 mL), especially during wet periods, which shows that diffuse loading can be a significant source of fecal pollution. Fecal indicators were detected in about half of the samples of pristine areas, sometimes in concentrations exceeding the limit of good swimming water (100 bacteria per 100 mL). This contamination was probably caused by wild animals, especially by elk (Alces alces) and deer (Odocoileus virginianus) living in the areas. The concentrations of bacteria were higher in running waters than in ponds. The reliabilities of routine enumeration methods for the bacteria were evaluated by carrying out confirmation tests for isolated strains. Thermotolerant coliforms were reliable indicators in waters contaminated by diffuse loading. The reliability of enumeration of fecal streptococci in these waters should be studied further.
A Functional Model of Solute Transport that Accounts for Bypass
Authors: Corwin D. L. , Waggoner B. L. , Rhoades J. D.
Published: July 2010

Public awareness of groundwater contamination has created renewed interest in solute transport models that can be practically applied as groundwater quality management tools. Because of their simplicity with regard to input requirements, functional models of solute transport are excellent groundwater quality management tools. A functional model of one‐dimensional solute transport that accounts for hydraulic bypass is presented. The transport model, TETrans, simulates the vertical movement of nonvolatile solutes (i.e., trace elements and nonvolatile organic chemicals) through the vadose zone. Plant water uptake is taken into account assuming no solute uptake by the plant. TETrans requires minimal input data for its operation. Since TETrans uses a mass‐balance approach to solute transport, it offers the speed of an analytical solution and the versatility of a numerical approach without the need for input parameters, which are difficult to measure. TETrans is able to account for bypass with a single term, the mobility coefficient. The mobility coefficient, γ, represents the fraction of the soil liquid phase, which is subject to piston‐type displacement; therefore, 1 ‐ γ represents the fraction of the liquid phase that is bypassed. The mobility coefficient is a temporally and spatially variable parameter (within a range of 0 to 1), which is calculated from the deviation of the measured chloride concentration from the predicted concentration assuming piston displacement and assuming complete mixing of the resident soil solution and incoming water for a given irrigation and volume of soil. A constant mobility coefficient for a given depth or entire profile can be determined by averaging temporally varying mobility coefficients or averaging spatially and temporally varying mobility coefficients, respectively. In essence, the mobility coefficient simplistically accounts for three physical transport phenomena in a single term. On a microscopic level there is flow through cracks and macropores that bypasses small and dead‐end pores. On a macroscopic level there is the flow of a mobile water phase independent of stagnant immobile phase of water, and the phenomenon of dispersion‐diffusion. Simulations of chloride movement through a soil lysimeter column for an 1100‐d period were compared to measured chloride concentrations in the soil solution at field capacity. A constant mobility coefficient significantly improved the capability of TETrans to describe the data when compared to simulations performed assuming complete piston‐type displacement. However, the best simulation to the measured chloride data was for the use of a spatially and temporally variable mobility coefficient.
Deep Nitrate Movement in the Unsaturated Zone of a Simulated Urban Lawn
Authors: Exner M.E. , Burbach M.E. , Watts D.G. , Shearman R.C. , Spalding R.F.
Published: July 2010

The increasing incidence of NO3 contamination in municipal wells is a growing concern in the Midwest. While leachates from N fertilizers applied to agricultural lands can impact the water quality in municipal wells, there is also the potential for leachates from turfgrass fertilizers to be groundwater contaminants. In this study, five plots were treated with ammonium nitrate (34‐0‐0,N‐P‐K) at rates of 0, 1.0, 1.5, 2.0, and 2.4 kg N/100 m2 and irrigated‐ The turf received approximately 640 mm of water during the 34‐d study. Analysis of soil water from 15, 6‐m continuous cores showed that as much as 95% of the NO3 applied in late August leached below the turfgrass root zone. Average NO3 concentrations in the pulse ranged from 34 to 70 mg/L NO3‐N. Thirty‐four days after fertilization the center of the pulse was at ≈1.2 m with the leading edge at 2 to 2.5 m. This vertical rate of movement is similar to that predicted by the one‐dimensional CMLS model. The relatively high uniform NO3 concentrations in the unfertilized plot indicated that with excessive irrigation the water alone supplies NO3 in excess of the turfgrass need.
Nitrogen and Phosphorus in Eroded Sediment from Corn and Soybean Tillage Systems
Authors: McIsaac Gregory F. , Hirschi Michael C. , Mitchell J. Kent
Published: July 2010

Runoff, soil loss and sediment bound total Kjeldahl nitrogen (TKN) and Bray P‐1 phosphorus (P) losses were measured corn (Zea mays L.) and soybean [Glycine max (L.)] tillage systems subjected to simulated rainfall. Runoff and soil loss were influenced by contouring and tillage treatment. After 60 min of simulated rainfall, there was little or no runoff or soil erosion from plots which had recently been ridge cultivated along the contour. Soil and nutrient losses from up‐and‐down slope ridge‐till plots were never significantly different than from the conventional tillage treatment. Bray P‐1 P concentration in the top 5 cm of soil and eroded sediment was significantly reduced by moldboard plowing. Concentrations of Bray P‐1 in the eroded sediment tended to decrease as soil loss increased. Bray P‐1 enrichment ratios ranged from 1.69 to 4.5, and were correlated to a greater extent with sediment concentration than with soil loss. The TKN losses were linearly related with soil loss and the average TKN enrichment ratio ranged from 1.02 to 1.28. The TKN enrichment ratio was not significantly correlated with Bray P‐1 enrichment ratio.
Denitrification in Grass and Forest Vegetated Filter Strips
Authors: Groffman Peter M. , Axelrod Eric A. , Lemunyon Jerrell L. , Sullivan W. Michael
Published: July 2010

Denitrification was measured in two grass and two forest vegetated filter strips (VFS) in Rhode Island. The grass plots were established on a well‐drained soil and were planted to either tall fescue (Festuca arundinacea) or reed canarygrass (Phalaris arundinacea). One forest site was on an excessively well‐drained soil and was dominated by oak (Quercus sp.), and the other was on a poorly drained soil and was dominated by red maple (Acer rubrum). Denitrification was measured using soil cores under aerobic and anaerobic conditions with a range of treatments: no amendment, acetylene, water, nitrate (NO−3), NO−3 plus C. Unamended rates of denitrification were low in all plots. Nitrate and NO−3‐plus‐C amended rates were consistently higher in the grass plots than in the forest plots. Nitrate‐plus carbon‐amended rates were higher than NO−3‐amended rates in all plots, but the differences were significant (P < 0.05) in the forest plots only. Denitrification enzyme activity (DEA) was measured in 14 additional forest sites of varying natural drainage classes and was related to soil moisture (r2 = 0.56, P < 0.01) and pH (r2 = 0.43, P < 0.01) at these sites. The results suggest that the ability of VFS to support denitrification varies strongly with vegetation, soil type and pH, and that denitrification in VFS may be amenable to management.
Effects of Dry Matter Content and Temperature on Ammonia Loss from Surface‐Applied Cattle Slurry
Authors: Sommer S. G. , Olesen J. E.
Published: July 2010

Effects of increasing dry matter content in slurry on NH3 loss was measured with a wind tunnel system, whereby parameters affecting the volatilization can be estimated under controlled conditions. The effect of dry matter content on NH3 loss was measured using a slurry adjusted to different contents of dry matter. The slurry was prepared by mixing the fibrous and liquid fractions of a mechanically separated cattle slurry. Slurry was applied to a 5 cm high grass ley (Lolium multiflorum Lam.) and to barley (Hordeum vulgare L.) at a rate of 3 L m−2. The content of dry matter varied from 0.9 to 22%, total N from 2.9 to 4.9 g N L−1, TAN (NH3 + NH−+4) from 1.6 to 3.0 g N L−1 and pH from 7.0 to 7.9. The results indicated that NH3 volatilization increased with increasing slurry dry matter content. The accamuiated 6‐d loss ranged from 19 to 100% of applied TAN from slurries having a dry matter content of 0.9 and 15.6%, respectively. The accumulated NH3 loss after 6 h exposure was linearly related to dry matter content. In the periods of 6 to 12 h, 12 to 24 h and 24 h to 6 d the loss was nonlinearly related to dry matter content. If the results were adjusted for effects of pH and temperature, NH3 loss tended to be sigmoidally related to content of dry matter in all four periods. Therefore, changes in slurry dry matter content on NH3 loss seemed to be small if the dry matter content was higher than 12% or lower than 4%.
Mineralization of Sulfur in Soils Amended with Organic Wastes
Authors: Tabatabai M. A. , Chae Y. M.
Published: July 2010

This study was conducted to compare the mineralization of S in soils amended with various types of sewage sludges, animal manures, and plant materials. Field‐moist soils amended with organic waste materials at a 50‐Mg‐ha−1 rate were mixed with glass beads, packed in leaching columns, leached with 5 mM CaCl2 to remove the mineral S, and incubated at 30 °C. The leaching procedure was repeated every 2 wk for 26 wk. The leachates were analyzed for SO2−4‐S. The rate of SO2−4 release from sewage sludges was rapid during the first 6 wk, followed by a slow linear release. The release of SO2−4 from anhnal manures was linear with time of incubation. With the exception of alfalfa (Medicago sativa L.), which showed a rapid SO2−4 release within the first 2 wk and a subsequent linear release with time up to 26 wk, the addition of all other plant materials resulted in net S immobilization. The total net S mineralized from the organic waste materials varied considerably, depending on the type of soil and the C/N/S ratio of the organic waste material. The amounts of S mineralized in soils amended with sewage sludges and animal manures ranged from 99 to 345 mg S kg−1 and from 32 to 52 mg S kg−1 soil, respectively. The total S mineralized in soils amended with plant materials ranged from 15 to 57 mg S kg−1. Expressed as a percentage of total organic S added to soils, the S mineralized ranged from 41 to 97% for sewage sludges and from −62 to 127% for animal manures. The percentage of organic S mineralized in the plant materials ranged from −510% for cornstalk (Zea mays L.) to 87% for alfalfa. Soil types have marked effects on the mineralizable S (S0) pool and first‐order rate constants (k).
Fate of Heavy Metals in an Abandoned Lead‐Zinc Tailings Pond: I. Vegetation
Authors: Chambers Jeanne C. , Sidle Roy C.
Published: July 2010

A 50‐yr‐old abandoned tailings pond from a Pb‐Zn processing mill was studied to determine relationships among depositional processes, physical and chemical properties of surface soils, vegetation development, and plant foliar concentrations of Zn, Cd, Cu, and Pb. Five soil/vegetation types were identified ranging from loamy sand with arid land species and 14% aerial vegetation cover at the upper (north) end of the pond to clay loam with wet meadow species and 61% cover at the lower (south) end of the pond. Foliar concentrations of Cd, Zn, Cu and Pb in blue grama [Bouteloua gracilis (H.B.K) Lag.] and creeping bentgrass (Agrostis stolonifera L.) showed no significant differences among the soil/vegetation types in which they dominated. Concentrations of Cd and Pb in foliage of alkali muhly [Muhlenbergia asperifolia (Nees & Meyen) Parodi], a ubiquitous grass species, were higher at the south than the north end of the pond. Metal concentrations in alkali muhly showed significant linear relationships to soil concentrations of metals in the five soil/vegetation types for total Cd (r2 = 0.97; P ≤ 0.001) and Zn (r2 = 0.70; P ≤ 0.05), but exhibited negative exponential relationships for total Cu (r2 = 0.99; P ≤ 0.001) and Pb (r2 = 0.99; P ≤ 0.001). Lead concentrations in grasses within the lower meadows (37.6–69.0 mg kg−1 dry mass) exceeded levels known to be toxic to plants. The results were evaluated in terms of tailings pond reclamation.
Productivity of Clay Tailings from Phosphate Mining: III. Grain Crops
Authors: Mislevy P. , Blue W.G. , Roessler C.E. , Martin F.G.
Published: July 2010

Phosphatic clay is a waste product from the Florida phosphate mining industry presently totaling 41 000 ha. These clays contain no phytotoxic materials, are high in most plant nutrients, and 226Ra and average about 460 g moisture per kilogram. A split‐plot field experiment was conducted to study forage and grain yield, forage quality, plant nutrient concentrations, changes in soil nutrients, and 226Ra contents of four grain crops in various rotations. The crop rotations (i) corn (Zea mays L. ‘Jacques 247’)‐sunflower (Helianthus annuus L. ‘Cargill 205’), (ii) sunflower‐grain sorghum (Sorghum bicolor L. Moench ‘Northrup King Savanna 5’), (iii) soybean (Glycine max L. Merr. ‘Williams 80’)‐grain sorghum, and (iv) grain sorghum‐soybean ‘University of Florida V‐1’) were grown on a dry phosphatic clay with and without a 50‐mm surface layer of quartzsand tailings. Nitrogen was the only fertilizer element applied. Results show that corn and grain sorghum produced highest (P < 0.05) forage yields (15.7 and 13.4 Mg ha–1) and highest grain yields (8955 and 4302 kg ha–1) per harvest, respectively. Soybean harvested for forage (Crop 1) contained the highest crude protein (217 g kg–1) and in vitro organic matter digestibility (736 g kg–1). Concentrations of P, K, Ca, Mg, and Fe in most of the forages were adequate for the diets of beef cattle (Bos taunts), while those of Mn, Cu, and Zn were low. Mehlich I‐extractable soil P (1601 mg kg–1), Ca (4696 mg kg–1), and Mg (1173 mg kg–1) were considered very high and changed little over the 4‐yr production period. Application of 50 mm of sand tailings tended to increase (P < 0.05) Mehlich I‐extractable P, Ca, Mn, Cu, Zn, and Fe. Radium‐226 concentration in the forage of all grain crops averaged 8.5 Bq kg–1, which was about 17 times higher than that in the grain (0.4958 Bq kg–1) of the same crops. Concentrations of 226Ra in the forage (8.288 Bq kg–1) and grain (0.6771 Bq kg–1) were 1.1% and 0.09% of the concentration in clay (761 Bq kg–1) respectively. These data indicate that phosphatic clays can be a valuable resource for the production of corn and sorghum grain that contain low concentrations of 226Ra.
Leaching of Nitrate from Monolith Lysimeters of Different Types of Agricultural Soils
Authors: Bergström L. , Johansson R.
Published: July 2010

Nitrate leaching was measured in field lysimeters containing undisturbed soils of different texture and organic matter content. Spring barley (Hordeum distichum L.) was sown on each lysimeter and fertilized with 100 kg N ha–1. Each soil type received supplementary watering to simulate either “average” or “worst‐case” precipitation. The largest leaching losses of NO–3, ca. 65 kg N ha–1 yr–1, occurred in a sandy soil that contained little organic matter and in a peat soil. Two loamy soils lost between 25 and 40 kg N ha–1 yr–1. Smallest leaching losses, ca. 20 kg N ha–1 yr–1 or less, occurred in a clay soil and another sandy soil rich in organic matter. With the exception of the clay and peat soils, the watering treatment did not significantly affect the amounts of NO–3 leached, although the temporal distribution of leaching was clearly influenced by weather conditions. The difference in leaching between the two sandy soils was explained by differences in crop growth, whereas leaching differences between soil types were mainly considered to be due to different textural and structural properties. The results show that to make a thorough comparison of NO–3 leaching between different soil types they have to be tested simultaneously at the same site.
Nonequilibrium Sorption and Degradation of Three 2‐Chloro‐s‐Triazine Herbicides in Soil‐Water Systems
Authors: Gamerdinger A. P. , Lemley A. T. , Wagenet R. J.
Published: July 2010

Miscible displacement techniques were used for the simultaneous study of nonequilibrium sorption and degradation of atrazine (2‐chloro‐4‐etbylamino‐6‐isopropylamine‐s‐triazine), simazine (2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine), and cyanazine (2‐(4‐chloro‐6‐ethylamino)‐s‐triazine‐2‐ylamino‐2‐proprionitrile) on two central New York soils. A bicontinuum model, which considers sorption in two domains and includes a description of first‐order degradation, was applied to describe experimentally determined breakthrough curves. Values of the equilibrium sorption constant, K, and first‐order degradation rate constant, µ, were independently measured using batch and mass‐balance techniques. Values of the sorption rate coefficient (fitted with a bicontinuum model) were inversely correlated with K, and were dependent on concentration and velocity. Estimates of the rate of atrazine degradation were on the same order, but slower when measured with miscible displacement vs. batch incubation techniques. The techniques presented in this study provide an opportunity to better quantify sorption and degradation parameters that are required in environmental fate models.
Popular Formulations for Modeling Tree Rings from Climate: A Unifying Approach
Authors: Van Deusen P. C.
Published: July 2010

There are several model formulations in current use for predicting tree‐ring widths from climate variables. The results of such studies may aid in predicting past climate or in understanding how trees will respond to future climate change. However, it isn't clear if the results of such investigations depend on the particular modeling strategy selected. In an effort to answer this question, a general formulation is presented that includes the most commonly used models as special cases. The general formulation and selected special cases are then fit to the same tree ring dataset. Procedures are demonstrated for choosing among the various formulations based on information criteria and evaluating Kalman filter prediction errors.
Soil Chemistry and Nutrition of North American Spruce‐Fir Stands: Evidence for Recent Change
Authors: Joslin J.D. , Kelly J.M. , Van Miegroet H.
Published: July 2010

One set of hypotheses offered to explain the decline of red spruce (Picea rubens Sarg.) in eastern North America focuses on the effect of acidic deposition on soil chemistry changes that may affect nutrient availability and root function. Long‐term soils data suggest that soil acidification has occurred in some spruce stands over the past 50 yr, with plant uptake and cation leaching both contributing to the loss of cations. Studies of tree ring chemistry also have indicated changes in Ca/Al and Mg/Al ratios in red spruce wood, suggesting increases in the ionic strength of soil solution. Irrigation studies using strong acid inputs have demonstrated accelerated displacement of base cations from upper horizons. Spruce‐fir (Abies spp.) nutrient budgets indicate that current net Ca and Mg leaching loss rates are of the same order of magnitude as losses to whole tree harvest removals, spread out over a 50‐yr rotation. For most cations, red spruce foliar nutrient levels decline with elevation, but it is difficult to assess the contribution of the elevational gradient in atmospheric deposition to this pattern. Compared to northeastern sites, spruce‐fir soil solutions in the southern Appalachians have higher nitrate levels and higher Al concentrations, which at times approach the Al toxicity threshold for red spruce seedlings and frequently are at levels known to interfere with cation uptake. There is little evidence that either nutrient deficiencies or Al toxicity are primary causes of red spruce decline in the Northeast, though both may play a role in the Southeast. Major factors that could affect soil chemistry in spruce‐fir stands in the future are (i) changes in S and N deposition, (ii) climate changes affecting soil organic matter decomposition and nutrient uptake, and (iii) tree mortality and physical disturbances to soils resulting in soil nitrate release.
Desorption and Unavailability of Aged Simazine Residues in Soil from a Continuous Corn Field
Authors: Scribner Stephen L. , Benzing Thomas R. , Sun Shaobai , Boyd Stephen A.
Published: July 2010

The sorption/desorption behavior of field weathered (aged) simazine (2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine) residues from a 20‐year continuous corn (Zea mays L.) field was compared to that of 14C‐simazine recently added to the same soil. The apparent sorption coefficients of the aged residues determined from 24‐h and 48‐h desorption experiments were approximately 15 times higher than the sorption coefficients of added simazine. Aged simazine residues were also shown to be biologically unavailable to sugarbeet (Beta vulgaris L.) and to microbial degraders, whereas recently added simazine showed herbicidal damage to sugarbeet and was substantially (ca. 48%) degraded during a 34‐d incubation in soil. Apparently, the process of pesticide aging results in simazine residues that are less bioavailable, as shown by their resistance to plant uptake and microbial degradation, and that desorb slowly into soil solution. The concentration of simazine in water from field soil‐samples (C) was monitored throughout a growing season, and compared to the equilibrium aqueous phase concentration (Cc) predicted from the laboratory determined sorption coefficient (Koc of added 14C‐simazine. The fractional equilibrium values (C/Ce.) were approximately 1 at the time of simazine application in May but fell to 0.05 during July and August. These results show that the concentration of simazine in water contacting field soil is likely to be substantially lower than that predicted from laboratory determined sorption coefficients, except immediately following application.
Selective‐Placement Burial of Drilling Fluids: II. Effects on Buffalograss and Fourwing Saltbush
Authors: McFarland Mark L. , Ueckert Darrell N. , Hons Frank M. , Hartmann Steve
Published: July 2010

Surface disposal of spent drilling fluids used in petroleum and natural gas exploration causes surface soil contamination that severely inhibits secondary plant succession and artificial revegetation efforts. Selective‐placement burial was evaluated at two locations in western Texas for on‐site disposal of drilling fluids in arid and semiarid regions. Establishment, yield, and chemical composition of fourwing saltbush [Atriplex canescens (Pursh) Nutt.] and buffalograss [Buchloe dactyloides (Nutt.) Engelm.] transplants on undisturbed soils and plots with spent drilling fluids and cuttings buried 30, 90 (with and without a 30‐cm coarse limestone and capillary barrier) and 150 cm were compared. Survival of boths pecies was 97 to 100% 17 months after planting on plots with buried drilling wastes. Canopy cover and aboveground biomass of fourwing saltbush were greater over buried drilling wastes than on untreated plots, whereas canopy cover and aboveground biomass of buffalograss were not affected by the treatments. Significant increases in Na, K, and Mg concentrations in buffalograss after 17 months on plots with drilling fluids buried 30 cm deep at one location indicated plant uptake of some drilling fluid constituents. Elevated Zn concentrations in fourwing saltbush indicated that a portion of the Zn in the drilling fluids was available for plant uptake, while no evidence of plant accumulation of Ba, Cr, Cu, or Ni from drilling fluids was detected. Selective‐placement burial of drilling fluids offers an environmentally sound technique that will enhance revegetation efforts.
Estimating the Percent Aromatic Carbon in Soil and Aquatic Humic Substances Using Ultraviolet Absorbance Spectrometry
Authors: Novak J. M. , Mills G. L. , Bertsch P. M.
Published: July 2010

The aromatic C content of humic substances is an important chemical property that can be used to explain formation, source, and potential interactions of the humic substances with pesticides and other contaminant organics. The relationship between the UV absorptivity at 272, 254, and 205 nm of six aquatic fulvic acids, eight soil fulvic acids, and four water soluble organic C (WSOC) fractions, and their aromatic C content, as determined by 13C cross‐polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy was evaluated. The percent aromatic C (determined by NMR) for the pooled soil and aquatic fulvic acids and WSOC fractions data was poorly correlated (r < 0.7) with the UV absorptivity measurements at all three wavelengths. When the soil fulvic acid was considered individually, however, a relatively high correlation (r = 0.80 to 0.85, P < 0.05) resulted for the prediction of aromatic C content using UV absorptivity. Poor correlations were found for the other individual fractions. Our data suggest that the prediction of aromatic C content using UV absorptivity was applicable only for base‐extracted soil fulvic acids and not for the aquatic fulvic acids and soil WSOC fractions used in this study.
Soil Science for Environmental Quality—How Do We Know What We Know?
Authors: Warkentin B.P.
Published: July 2010

It is argued that the soils information we have available to apply to environmental issues has depended on the kinds of questions we have asked in soil science. Four periods are identified in the last 150 yr when we asked different kinds of questions. The last period brings us back to some of the same questions asked in the first period. The characteristics of these periods are discussed to give us a perspective as our thinking is now changing from soils as an input into crop production to include a greater emphasis on soil processes that mediate global changes.
Accumulation of Some Metals by Legumes and Their Extractability from Acid Mine Spoils
Authors: Taylor R.W. , Ibeabuchi I.O. , Sistani K.R. , Shuford J.W.
Published: July 2010

A greenhouse study was conducted to investigate the growth (dry matter yield) of selected legume cover crops; phytoaccumulation of metals such as Zn, Mn, Pb, Cu, Ni, and Al; and extractability of heavy metals from three different Alabama acid mine spoils. The spoils were amended based on soil test recommended levels of N, P, K, Ca, and Mg prior to plant growth. Metals were extracted by three extractants (Mehlich 1, DTPA, and 0.1 M HCl) and values correlated with their accumulation by the selected legumes. Among the cover crops, kobe lespedeza [Lespedeza striata (Thung.) Hook & Arn.], sericea lespedeza [Lespedeza cuneata (Dum.) G. Don], and red clover (Trifolium pratense L.) did not survive the stressful conditions of the spoils. However, cowpea (Vigna unguiculata L.) followed by ‘Bragg’ soybean [Glycine max (L.) Merr.] generally produced the highest dry matter yield while accumulating the largest quantity of metals, except Al, from spoils. The extractability of most metals from the spoils was generally in the order of: 0.1 M HCl > Mehlich 1 > DTPA. Mehlich 1 did not extract Pb and 0.1 M HCl did not extract Ni, whereas DTPA extracted all the metals in a smaller amount relative to HCl and Mehlich 1. All the extractants were quite effective in removing plant‐available Zn from the spoils. In general, the extractants' ability to predict plant‐available metals depended on the crop species, spoil type, and extractant used.
Distribution and Partitioning of Trace Metals in Contaminated Soils near Leadville, Colorado
Authors: Levy D.B. , Barbarick K.A. , Siemer E.G. , Sommers L.E.
Published: July 2010

Mountain meadows near Leadville, CO, were contaminated with trace metals through the deposition of hydraulically transported mine tailings in the early 1900s. A study was conducted to: (i) characterize the physical and chemical properties of contaminated soils, (ii) determine the soil depth distribution of total, organically bound, oxide‐bound, exchangeable, and water‐soluble metals, and (iii) evaluate trace metals in forages grown in contaminated meadows. One uncontaminated and four contaminated locations in a north‐south transect were studied. Total soil metals ranged from: Cu, 14 to 1200 mg kg−1; Cd, 3 to 110 mg kg−1; Pb, 46 to 49000 mg kg−1; and Zn, 44 to 12000 mg kg−1. The greatest concentrations of total metals were found either in the surface horizons or in hydraulically deposited sand layers that were buried at three locations. Copper was predominantly associated with the organic fraction at four of the five locations, while Cd, Pb, and Zn were mainly bound to Fe and Mn oxides at all locations. The concentrations of Cd, Pb, and Zn in forages were significantly related to various fractions of soil metals and were found to be potentially detrimental to livestock health and plant growth.
The Effects of Herbicides on Development of Myriophyllum spicatum L. Cultured In Vitro
Authors: Christopher Susan V. , Bird Kimon T.
Published: July 2010

Tissue cultures of the aquatic plant, Myriophyllun spicatum L., were used to evaluate the effects of four different herbicides and a leaf defoliant on development. The developmental parameters used were the production of new axillary buds, leaves, roots and branches. Production of new branches was the most sensitive measure. The order of developmental inhibition was: 2,4‐dichlorophenoxyacetic acid > atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) > glyphosate [N‐(phosphonomethyl)glycine] > thidiazuron (N‐phenyl‐N′‐1,2,3‐thiadiazol‐5‐ylurea). The herbicide linuron [8‐(3,4‐dichlorophenyl)‐1‐methoxy‐1‐methyl urea] showed no statistically significant toxic effects below 100 mg L−1. This bioassay system provided a quick, sensitive measure of herbicide effects on aquatic plant development. The short time period of only 5 d permits more rapid bioassays than conventional whole plant bioassays.
Photosynthesis and Growth Response of Almond to Increased Atmospheric Ozone Partial Pressures
Authors: Retzlaff W.A. , DeJong T.M. , Williams L.E.
Published: July 2010

Uniform nursery stock of five almond cultivars [Prunus dulcis (Mill) D.A. Webb syn. P. amygdalus Batsch, ev. Butte, Carmel, Mission, Nonpareil, and Sonora] propagated on peach (P. domestica L. Batsch.) rootstock were exposed to three different atmospheric ozone (O3) partial pressures. The trees were planted in open‐top fumigation chambers on 19 Apr. 1989 at the University of California Kearny Agricultural Center located in the San Joaquin Valley of California. Exposures of the trees to three atmospheric O3 partial pressures (charcoal filtered air, ambient air, or ambient air + O3) lasted from 1 June to 2 Nov. 1989. The mean 12‐h [0800–2000 h Pacific Daylight Time (PDT)] O3 partial pressures measured in the open‐top chambers during the experimental period were 0.038, 0.060, and 0.112 µPa Pa−1 O3 in the charcoal filtered, ambient, and ambient + O3 treatments, respectively. Leaf net CO2 assimilation, trunk cross‐sectional area growth, and root, trunk, foliage, and total dry weight of Nonpareil were reduced by increased atmospheric O3 partial pressures. Mission was unaffected by O3 and Butte, Carmel, and Sonora were intermediate in their responses. Foliage of Nonpareil also abscised prematurely in the ambient and ambient + O3 treatments. The results indicate that there are almond cultivars that are sensitive to O3 exposure.
An Improved Method For Field Extraction and Laboratory Analysis of Large, Intact Soil Cores
Authors: Tindall James A. , Hemmen K. , Dowd J.F.
Published: July 2010

Various methods have been proposed for the extraction of large, undisturbed soil cores and for subsequent analysis of fluid movement within the cores. The major problems associated with these methods are expense, cumbersome field extraction, and inadequate simulation of unsaturated flow conditions. A field and laboratory procedure is presented that is economical, convenient, and simulates unsaturated and saturated flow without interface flow problems and can be used on a variety of soil types. In the field, a stainless steel core barrel is hydraulically pressed into the soil (30‐cm diam. and 38 cm high), the barrel and core are extracted from the soil, and after the barrel is removed from the core, the core is then wrapped securely with flexible sheet metal and a stainless mesh screen is attached to the bottom of the core for support. In the laboratory the soil core is set atop a porous ceramic plate over which a soil‐diatomaceous earth slurry has been poured to assure good contact between plate and core. A cardboard cylinder (mold) is fastened around the core and the empty space filled with paraffin wax. Soil cores were tested under saturated and unsaturated conditions using a hanging water column for potentials ≤0. Breakthrough curves indicated that no interface flow occurred along the edge of the core. This procedure proved to be reliable for field extraction of large, intact soil cores and for laboratory analysis of solute transport.
Conceptual and Empirical Foundations for Agricultural‐Environmental Policy Analysis
Authors: Antle John M. , Just Richard E.
Published: July 2010

The knowledge base necessary to support informed agricultural‐environmental policy involves many disciplines. This article presents a conceptual framework for agricultural‐environmental policy analysis based on integration of disciplinary knowledge. The framework demonstrates that, with suitably coordinated data collection and research design activities, policy analysis can be conducted on the basis of disciplinary research. In other words, interdisciplinary data collection rather than interdisciplinary research is needed. Current publicly financed data generation efforts could serve agricultural‐environmental policy needs if disciplinary expertise were used to ensure compatibility with disciplinary requirements while coordinating efforts so as to allow data integration for subsequent policy analysis.
Sorption of the Herbicides Atrazine and Metolachlor to Selected Plastics and Silicone Rubber
Authors: Topp Edward , Smith Ward
Published: July 2010

The adsorption of atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) or metolachlor (2‐chloro‐6′‐ethyl‐N‐(2‐methoxy‐1‐methylethyl)acet‐o‐toluidine) to a variety of plastics and silicone rubber was determined. Both herbicides adsorbed rapidly to silicone rubber, Nalgene 180, Tygon R‐3603, and somewhat less rapidly to low‐density polyethylene. Neither of the herbicides was significantly adsorbed by high‐density polyethylene or acrylic plastic. Very little sorbed metolachlor or atrazine was extracted with methanol and acetone from low‐density polyethylene, indicating that the compounds were tightly adsorbed. Radiolabeled atrazine residues slowly desorbed from Nalgene plastic into water with only the parent compound detectable by gas chromatography, indicating that no chemical transformation had taken place. Organic materials used in containers or equipment coming in contact with atrazine or metolachlor should be screened for their interaction with these compounds.
Selenium and Sulfur Relationships in Alfalfa and Soil under Field Conditions, San Joaquin Valley, California
Authors: Severson R. C. , Gough L. P.
Published: July 2010

Relationships between total Se and S or soluble SeO4 and SO4 in soils and tissue concentrations in alfalfa (Medicago sativa L.), under field conditions in the San Joaquin Valley of California, suggest that the rate of accumulation of Se in alfalfa may be reduced in areas where high Se and S concentrations in soils were measured. These data suggest that the balance between carbonate and sulfate minerals in soil may have a greater influence on uptake of Se by alfalfa than does the balance of SeO4 and SO4 in soil solution. Soil and alfalfa were sampled from areas representing a wide range in soil Se and S concentrations. Specific sampling locations were selected based on a previous study of Se, S, and other elements where 721 soil samples were collected to map landscape variability and distribution of elements. Six multiple‐linear regression equations were developed between total and/or soluble soil chemical constituents and tissue concentrations of Se in alfalfa. We chose a regression model that accounted for 72% of the variability in alfalfa Se concentrations based on an association of elements in soil (total C, S, Se, and Sr) determined by factor analysis. To prepare a map showing the spatial distribution of estimated alfalfa Se concentrations, the model was applied to the data from the previously collected 721 soil samples. Estimated alfalfa Se concentrations in most of the study area were within a range that is predicted to produce alfalfa with neither Se deficiency nor toxicity when consumed by livestock. A few small areas are predicted to produce alfalfa that potentially would not meet minimum dietary needs of livestock.
Degradation of Perchloroethylene by Fenton's Reagent: Speciation and Pathway
Authors: Leung Solomon W. , Watts Richard J. , Miller Glenn C.
Published: July 2010

Silica sand contaminated with perchloroethylene (PCE) was effectively treated by Fenton's reagent. Silica sand contaminated with PCE at 1000 mg/kg was totally mineralized in 3 h by Fenton's reagent with initial concentration of about 2.1 M of H2O2 and 5 mM of FeSO4. Results from gas chromatography‐mass spectroscopy (GC‐MS) revealed that dichloroacetic acid was the sole significant intermediate species generated, and was believed to be the limiting species leading to mineralization. Experimental measurements of chloride and total organic C suggested that total dechlorination was achieved before decarboxylation in the process of mineralization. A degradation pathway of PCE with Fenton's reagent is proposed based on experimental observations and reactions reported in literature. Formic acid is proposed to be the final intermediate species before it is mineralized to CO2. Perchloroethylene and H2O2 followed pseudo first‐order decomposition kinetics and the rate constants were determined to be 1.65/h ± 0.475/h and 0.206/h ± 0.036/h, respectively.
Nutrient Transformations in Sediments as Influenced by Oxygen Supply
Authors: Moore P. A. , Reddy K. R. , Graetz D. A.
Published: July 2010

The oxidation status of sediments greatly affects biogeochemical processes. The objective of this study was to determine the influence of various levels of O2 on nutrient transformations in lake sediments. Decomposition of sediment organic matter was evaluated under varying levels of O2. Bulk sediment samples obtained from a hypereutrophic lake in central Florida were incubated in stirred microcosms at 25°C for 100 d at four O2 levels. The O2 levels were accomplished by bubbling N2 containing 0, 0.2, 2.0, and 20.0% O2 through the stirred suspensions. Redox potential (Eh) measurements indicated that the two highest O2 levels (i.e., 2.0 and 20.0% O2) resulted in oxidizing conditions (Eh > 400 mV), whereas the lowest O2 levels (0 and 0.2% O2) resulted in reduced conditions (Eh < −300 mV). First‐order rate constants calculated based on CO2 evolution were 0.00010, 0.00027, 0.00062, and 0.00068 d−1 for the 0, 0.20, 2.0, and 20.0% O2 levels, respectively. Methane was detected in the sediments incubated under 0 and 0.2% O2 level, with CO2/CH4 ratios of 3.5 and 160, respectively. Accumulation of soluble organic C (SOC) was greater under reduced conditions than oxidized conditions. Ammonium concentrations decreased rapidly in the oxidized treatments, with concurrent increases in NO3‐N concentrations, whereas under reducing conditions NH4‐N concentrations slowly increased. Rates of N mineralization were slightly higher under oxidized conditions. Although the ratio of N mineralized to CO2 evolved was higher at low O2 levels, the amount of N mineralized vs. the sum of C metabolites (CO2 + CH4 + SOC) was relatively constant under all O2 levels (6.7:1). Reducing conditions resulted in a depletion of SO2−4, whereas under oxidizing conditions SO2−4 concentrations increased, probably due to sulfide oxidation. Soluble reactive P concentrations were lower under oxidizing conditions.
Long‐Term Groundwater Quality Changes from a One‐Time Surface Bromide Application
Authors: Owens L. B. , Edwards W. M.
Published: July 2010

The purpose of this experiment was to use a conservative tracer to study the impacts on groundwater quality of a one‐time application of a water soluble chemical. Potassium bromide was applied at a rate of 168 kg Br−/ha to two 1.1‐ha pasture watersheds in east‐central Ohio. The watersheds had well‐drained residual silt loam soils and with slopes of 12 to 25%. A nearly impermeable clay layer under the watersheds created a perched aquifer from which groundwater samples could be taken at developed springs. There were seasonal variations in Br− concentrations in the groundwater and the highest concentrations (9.2 mg/L maximum peak) occurred within 3 yr following the Br− application. Ten years following the Br− application, Br− concentration in the groundwater was still slightly above initial baseline levels. Even with a one‐time application of a soluble chemical constituent on the surface of a small aquifer system, a multiyear impact was produced on the quality of groundwater.
Neutralization of Soil Acidity and Release of Phosphorus and Potassium by Wood Ash
Authors: Ohno Tsutomu
Published: July 2010

Wood ash is a residual by‐product being produced at an annual rate of 1.5 to 3.0 million t by wood burning power plants in the USA. Currently, much of this ash is being landfilled. Landspreading of wood ash, which is an alternative liming agent, on both agricultural and forest soils is being proposed as a means of disposal that is both environmentally and economically attractive. As with any soil amendment, there is a potential of adverse environmental impact from the landspreading of wood ash. An experiment was conducted to evaluate the initial rate of soil acidity neutralization by wood ash and the release of P and K into suspensions of 10 acid soils. The wood ash had a CaCO3 equivalence of 480 g kg−1. Changes in soil suspension pH, which were used to quantify the rate of acid neutralization by wood ash, and concentrations of P and K of wood ash‐amended soil suspensions were measured at reaction periods ranging from 30 to 300 s. Soil acidity neutralization rates were strongly correlated with soil pH and decreased 41% per unit pH increase in the pH 3.8 to 6.2 range. After the initial release of P into suspension, sorption of released P resulted in decreasing P concentration in the suspension with increasing reaction time for 7 of the 10 soils. Sorption of released P was greater at lower soil pH values, suggesting precipitation as Al and Fe phosphates. In contrast, the solubility of wood ash K was very high. The increase of suspension K levels resulted from the release of wood ash K as well as from the displacement of K on soil exchange sites by Ca and other exchangeable cations released directly from wood ash into the soil suspension. The increase in suspension K was equivalent to 55% of the total K content of the wood ash. The net K content of the suspensions remained near the same level during the reaction period suggesting that soil solution levels of K would immediately increase upon landspreading of wood ash.
Pesticides in Iowa Precipitation
Authors: Nations B.K. , Hallberg G.R.
Published: July 2010

Rainfall was sampled for pesticides to assess their occurrence in precipitation and potential impacts on water resources. Three areas in Iowa were sampled; two localities were in rural settings, and a third in an urban area. Fourteen pesticides, including ten herbicides and four insecticides, were detected from October 1987 through September 1990. Atrazine, alachlor, cyanazine, and metolachlor were the most commonly detected, with one or more of these four herbicides found in almost every rainfall sample during the growing season. Concentrations of individual pesticides ranged from 0.1 µg L−1 to 40.0 µg L−1, with most detections under 1.0 µg L−1. Pesticide detections in rainfall began in April and ended in July or August, probably related to the timing of chemical application and greater volatilization rates during warmer weather. Samples from the urban site had detections of the same agricultural chemicals found at the rural sites, but in lesser quantities. In addition to the commonly detected herbicides, three of the four insecticides detected in rainfall were only found in urban samples. Two of these have urban as well as agricultural uses. Some variation of pesticide detections were seen at the three sampling localities, related to regional and local use patterns. Concentrations were greater at sampling sites near fields where pesticides are applied, suggesting that local volatilization and distance of transport affect the concentrations in rainfall. Pesticide concentrations were highest at the beginning of a rainfall event with concentrations becoming lower in samples taken later in the event.