bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth and Yield of Field‐Grown Soybean in Response to Enhanced Exposure to Ultraviolet‐B Radiation
Authors: Sinclair T. R. , N'Diaye O. , Biggs R. H.
Published: July 2010

Concern has been raised about the projected depletion of stratospheric ozone and the resultant increased exposure of crops to ultraviolet (UV)‐B radiation. Studies done in growth chambers and greenhouses indicate that substantial decreases in photosynthetic activity and leaf area growth may result from enhanced exposure to UV‐B radiation. However, for soybean [Glycine max (L.) Merr.] very few studies have been done under field conditions, and these studies either used unfiltered UV lamps or harvested only a few plants to determine seed yield. The objective of this study was to examine the influence of a 32% enhancement of UV‐B irradiance at Gainesville, FL on the growth and yield under field conditions of six soybean cultivars. No influence of either UV‐A or UV‐B radiation was detected on any growth parameter studied. Leaf area development, internode length, phyllochron index, flowering date, podding date, crop growth rate, and final seed yield were unaffected by enhanced exposure to ultraviolet radiation. These results indicate that soybean crops are not in jeopardy from the projected increase in exposure to ultraviolet radiation.
Effects of Ozone, Sulfur Dioxide, Soil Water Deficit, and Cultivar on Yields of Soybean
Authors: Heggestad Howard E. , Lesser Virginia M.
Published: July 2010

The effects of ozone (O3) stress on bean yields and seed size of four soybean cultivars [Glycine max (L.) Merr.] grown in open‐top chambers in 1981, 1982, and 1983 are presented. The O3 treatments included charcoal filtered (CF) and nonfiltered (NF) air, and 0.03, 0.06, and 0.09 µL L−1 O3 added 7 h d−1 to NF air. The effects of SO2 in concentrations from 0.005 to 0.224 µL L−1 (4 h d−1, 5 d wk−1) from the seedling stage to maturity were studied in 1981 and 1982. In 1982 and 1983 the effects of soil moisture stress (SMS) and well‐watered (WW) soil conditions on the response of soybean to O3 stress were determined. The primary objective was the evaluation of 3 yr of soybean data from our site using the nonlinear Weibull and the polynomial dose‐response models to relate yield responses to O3 exposure doses. The variables also included SO2, soil moisture, and cultivar. The homogeneity of the response equations were compared to permit development of the smallest set of homogeneous equations over years. Both O3 and SO2 negatively impacted bean yields and seed size. No interactions between O3 and SO2 were indicated. With the Weibull model, interactions between O3 and soil moisture were observed with ‘Forrest’ in 1982 and ‘Williams’ in 1983. With an O3 level considered typical in soybean production areas (seasonal 7 h d−1, 0.055 µL L−1) compared to background O3 (0.025 µL L−1) and using all data from 3 yr of experiments, the Weibull model predicted the same (15%) mean yield loss under both SMS and WW regimes.
Relationship between Xylem Trace Metals and Radial Growth of Loblolly Pine in Rural Alabama
Authors: Jordan D. N. , Wright L. M. , Lockaby B. G.
Published: July 2010

This study was undertaken to evaluate the relationship between the metals Al, Cd, Cu, Mn, Pb, and Zn and the basal area increment (BAI) of loblolly pine (Pinus taeda L.) in an old growth stand in Alabama. The BAI is the annual stand average area increment at breast height, estimated from increment borer core samples at breast height. The sampled trees have inner annual ring dates ranging from 1843 to 1918. Significant negative linear relationships were found between concentrations of Cd, Pb, Zn, and the BAI series. Aluminum and Cu concentrations were inversely related to BAI. No significance was exhibited for Mn. These findings are discussed as potential contributing factors to forest decline. No correlation was found between the soil‐extractable levels of the metals and the concentration in the most recent xylem tissue. A significant correlation was found between bark Zn and recent xylem Zn concentrations. No other metals exhibited correlations between recent xylem and soil or bark concentration.
Metolachlor Transport in Surface Runoff
Authors: Buttle J. M.
Published: July 2010

In 1987 metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] was applied to a 5.5‐ha corn field in southern Ontario, Canada, in two separate areas—as a preemergence surface spray with cross‐contour plowing and as a pre‐plant incorporated treatment with contour plowing. The application rate for both treatments was 2.64 kg a.i. ha−1. Metolachlor concentrations in soils and in the dissolved and adsorbed phases in runoff from natural rainstorms were monitored throughout the growing season. Persistence in soils decreased exponentially after application, although there was evidence of temporary accumulation of metolachlor in footslope areas. Dissolved concentrations in runoff decreased with time, while temporal trends in adsorbed concentrations reflected changes in metolachlor persistence in soils. Average ratios of adsorbed to dissolved herbicide concentrations ranged from 7 to 57, and were dependent upon hydrological and pedologic conditions within the treatments. Sediment carried between 9 to 58% of the total metolachlor yield from runoff plots during individual storms, and 20 to 46% of the total yield over the monitoring period. Herbicide incorporation and contour plowing led to significant reductions in dissolved and adsorbed concentrations, and in total metolachlor loss in runoff, relative to application as a preemergence spray with cross‐contour plowing. Incorporation was associated with an increase in the relative importance of sediment in metolachlor transport. Variations in herbicide losses and the relative importance of transport vectors within a given treatment were linked to local hydrological processes.
Adsorption and Desorption of 2,4,6‐Trinitrotoluene by Soils
Authors: Pennington Judith C. , Patrick William H.
Published: July 2010

Potential environmental hazards are posed by the presence of 2,4,6‐trinitrotoluene (TNT) in soils of U.S. Army Ammunition Plants (AAP). Especially important is TNT interaction with the top several centimeters of soil, where highest concentrations occur. The TNT adsorption and desorption studies were conducted using soil samples collected from 13 AAP. Steady state adsorption and desorption of TNT with test soils was reached within 2 h. Batch TNT adsorption isotherms were best fit by the Langmuir adsorption model and had an average adsorption coefficient (Kd) of 4.0 for all soils. The TNT adsorption Kd's were most highly correlated with extractable Fe, cation exchange capacity, and clay content. Almost all of the adsorbed TNT was desorbed after three sequential desorption cycles. These results suggest that adsorption in surface soils will not greatly retard movement of TNT to lower soil horizons. The pH exerted little effect on adsorption and desorption, but oxidized conditions consistently decreased adsorption of TNT compared to reduced conditions. Two transformation products of TNT, 4‐amino‐2,6‐dinitrotoluene and 2‐amino‐4,6‐dinitrotoluene, were detected during the 24‐h test period under both oxidized and reduced conditions.
Adsorption, Degradation, and Plant Availability of 2,4‐Dinitrophenol in Sludge‐Amended Calcareous Soils
Authors: O'Connor G. A. , Lujan J. R. , Jin Yan
Published: July 2010

2,4‐Dinitrophenol (DNP) is a moderately weak acid that is expected to be highly labile (leachable and plant available) in high‐pH soils. The adsorption and degradation behavior of DNP in two sludge‐amended, calcareous soils was determined and used to explain DNP uptake by plants grown in the soils in the greenhouse. The DNP adsorption was minor in both soils and was only slightly affected by sludge. The DNP degradation was rapid in both soils and was unaffected by sludge. Thus, despite limited soil adsorption, plant uptake of DNP was minor in all crops and plant parts owing to rapid soil DNP degradation. Even if a municipal sludge highly contaminated with DNP was identified (an unlikely occurrence), concerns over possible plant contamination should not limit sludge applications to calcareous soils at agronomic rates. Rapid degradation will minimize opportunities for plant uptake of DNP from contaminated soils or leaching of DNP to groundwater, given careful water management.
Influence of Fly Ash on Soil Microbial Activity and Populations
Authors: Pichtel J. R. , Hayes J. M.
Published: July 2010

Incubation studies were conducted to assess the influence of various combination levels of alkaline (pH 12.2) powerplant fly ash and sewage sludge on soil microbial activity and numbers. A Glynwood (fine, illitic, mesic. Aquic Hapludalf) silt loam soil was mixed with 0, 5, 10, or 20% (w/w) ash and 0 or 5% composted sewage sludge. Respiration was strongly depressed in the 10 and 20% ash treatments over 28 d. Sludge addition improved respiration in all ash treatments except the 20% treatment. Total bacterial, actinomycete, and fungal counts in the soil typically decreased with increasing ash content. Counts were depressed by 57, 80, and 86%, respectively, at the 20% ash application rate. Sludge application increased microbial numbers but all populations were lower at the highest ash rates compared to the untreated control. Soil phosphatase, sulfatase, dehydrogenase, and invertase were inhibited as ash treatment levels increased. Catalase activity was not significantly affected by ash concentration. Addition of the sludge to the ash‐soil mixtures generally enhanced enzyme activity. The results indicate that high rates of fly ash to soils may hinder normal decomposition and nutrient cycling processes. This may be partially alleviated, however, by coapplication of a readily oxidizable organic substrate such as sewage sludge.
Sorption and Degradation of Pentachlorophenol in Sludge‐Amended Soils
Authors: Bellin Cheryl A. , O'Connor George A. , Jin Yan
Published: July 2010

Sorption and degradation of pentachlorophenol (PCP) by two alkaline and one acid soil was studied in the presence and absence of sewage sludge. The PCP concentrations used (0.1–10 mg kg−1) included PCP rates expected with land application of normal municipal sewage sludges. Sorption/desorption isotherms, derived using batch equilibrium techniques, were described by the Freundlich equation. The PCP sorption increased with increasing sludge additions. Desorption in the alkaline soils was completely reversible and no irreversible residues were formed. Leaching of PCP would be most likely in the unamended alkaline soils. Degradation of PCP at low (0.75 mg kg−1) initial concentration was rapid (t1/2 ≈10–15 d) in alkaline soils, but much slower (t1/2 ≈38 d) in the acid soils. Sludge additions to the soils did not substantially affect PCP degradation. More rapid degradation of PCP in the alkaline vs. acid soils was attributed to less sorption and more favorable conditions for microbial activity. Rapid degradation in the alkaline soil, and greater sorption in the acid soil, reduces the chance of PCP leaching. However, longer PCP residence times in the acid soil increase the possibility for plant uptake.
Nitrification in Sludge‐Amended Michigan Forest Soils
Authors: Burton Andrew J. , Hart James B. , Urie Dean H.
Published: July 2010

Net nitrification following liquid sludge application to four Michigan forest types was studied by aerobically incubating intact cores containing the forest floor and upper 10 cm of mineral soil. Significant net nitrification occurred in cores receiving surface applications of anaerobically digested municipal sludge (22.3 g N m−2). Core NO3‐N contents at 8 wk were 4.7, 5.3, 4.9, and 2.0 g m−2 for aspen (Populus spp.), northern hardwoods, oak (Quercus spp.), and pine (Pinus spp.) forest types, respectively. Net nitrification did not occur during 8‐wk incubations of untreated control cores or cores receiving surface applications of sludge sterilized by freeze‐drying (24.5 g N m−2) or liming (25.7 g N m−2), suggesting that the nitrifiers responsible for net nitrification in cores receiving the anaerobically digested sludge were added with the sludge. Nitrate content at 8 wk in cores from an oak field site receiving anaerobically digested sludge (43.0 g N m−2) 33 mo prior to incubation was 72% of that in oak site soil cores treated immediately prior to incubation (22.3 kg N m−2), indicating that nitrifying populations introduced with sludge 33 mo prior were still viable. Nitrate content at 8 wk in oak cores was 77% lower when sludge was incorporated. Nitrate contents in incubated soil cores could not be used to directly predict NO3 concentrations in soil leachate and groundwater beneath sludge‐treated plots at the four field sites. Results indicate that nitrification and potential for NO3 leaching following sludge application to acid forest soils are influenced by sludge type, forest type, and history of prior sludge applications.
Definition of Adverse Effects for the Purpose of Establishing Secondary National Ambient Air Quality Standards
Authors: Tingey David T. , Hodsett William E. , Henderson Sandra
Published: July 2010

Under the Clean Air Act, the USEPA establishes ambient air quality standards to protect public welfare from known or anticipated adverse effects from criteria air pollutants. Although adversity is simply defined (i.e., opposed to one's interest; harmful), its determination is fraught with difficulties. The definition depends on one's view point; society has established that some effects are more serious than others. There is a view that ecological effects are adverse only if they can be expressed in economic terms. This leads to the conclusion that mitigative actions need not be taken unless the costs of the action are offset by sufficient benefits. Adverse effects, however, should be viewed in a broader societal content, i.e., the total benefits from ecological systems.
The Removal of Barium Ion from Solution using Datura innoxia Mill. Suspension Culture Cells
Authors: Jackson Paul J. , Torres Agapito P. , Delhaize Emmanuel , Pack Elizabeth , Bolender Sarah L.
Published: July 2010

Plant suspension culture cells derived from Datura innoxia (Mill.) anthers rapidly remove Ba2+ from solution. Free Ba2+ is removed as a result of a strong interaction with a component of the cell wall. Binding to this component occurs over a wide range of pH and salt concentrations and does not require active metabolism. Cells will remove Ba2+ from nutrient media or from waste solutions that cannot support cell growth. Implications for the use of plant cell suspension cultures to remove this and other toxic ions from industrial effluent are discussed.
Nutrient and Sediment Losses from Turfgrass
Authors: Gross C.M. , Angle J.S. , Welterlen M.S.
Published: July 2010

The contribution of turfgrass fertilizer to surface and groundwater pollution is not well documented. Two studies, at separate locations, were therefore initiated to examine losses of nutrients and sediment via leaching and runoff from turfgrass. Treatments included fertilizer applied in a liquid and granular form and an unfertilized control. Sodded tall fescue (Festuca arundinacea Schreb.)/Kentucky bluegrass (Poa pratensis L.) plots were fertilized at a rate of 220 kg N ha−1 yr−1 in metered applications of urea. Runoff was collected and analyzed for volume, suspended and soluble solids, NH4‐N, NO3‐N, total N, PO4‐P, total soluble P, and total P. Runoff losses of sediment and all nutrients were extremely low. Runoff losses of total N were significantly (P ≤ 0.05) higher when comparing the liquid and granular treatments to the control, although there was no difference between fertilizer treatments. Losses for all forms of P and sediment did not significantly differ with regard to treatment. Soil percolate (0.75 m depth) was collected monthly from the various treatments. Percolate NO3‐N concentrations from the liquid and granular treatments did not differ significantly, although both were significantly higher than the untreated control. Soil cores (2.1 m depth) were collected every spring and fall in 0.30‐m increments. Nitrate‐N concentrations generally decreased with depth; however, the granular treatment exhibited a higher soil NO3‐N concentration than either the liquid or control treatments. These results indicate that when compared with agronomic row crops, nutrient and sediment losses from turf via runoff, and leaching are very low.
Long‐Term Swine Lagoon Effluent Applications on ‘Coastal’ Bermudagrass: II. Effect on Nutrient Accumulation in Soil
Authors: King Larry D. , Burns J. C. , Westerman P. W.
Published: July 2010

Application of effluent from animal manure lagoons to cropland is an effective method of utilizing the nutrients in the effluent and minimizing groundwater and surface‐water pollution. The objective of this study was to determine the effect of land application of effluent from a swine (Sus scrofa domenticus) manure lagoon on selected soil chemical properties at the end of an 11‐yr study. Effluent was applied at rates to supply approximately 335, 670, and 1340 kg of N ha−1 yr−1 to ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.) on a Paleudult soil from 1973 through 1983. Soil cores taken to a depth of 210 cm were analyzed for H2O‐extractable NO3‐N and Mehlich 1‐extractable P and cations. Nitrate‐N concentrations (1‐5 mg kg−1) with the two lower rates were similar to concentrations where no effluent was applied. At the high effluent rate, NO3‐N concentrations were elevated, particularly in the subsoil, and 540 kg NO3‐N ha−1 was present in the profile. Phosphorus increased with loading rate and at the high rate, P concentrations (450 mg kg−1) in the 0‐ to 15‐cm zone was 10 times the level above which no response to P fertilization would be expected. Potassium concentration increased with loading rate throughout the profile. Magnesium accumulation was inversely related to effluent loading rate in the 0‐ to 15‐cm zone, but accumulation in the subsoil was directly related to loading rate. Comparison of profile nutrient distributions at the high rate for Years 6 and 11 showed no appreciable accumulation of NO3‐N during the period. Accumulation of other nutrients during this 5‐yr period was P, 210%; K, 200%; Ca, 140%; Mg, 60%; and Na, 10% as compared with Year 6. Soil pH was decreased by the high effluent rate but did increase from 4.2 at Year 6 to 5.0 at Year 11 due to the increased rate of application of basic cations during that period. The high rate poses a groundwater pollution hazard because of the large quantity of NO3‐N present in the profile. In previous years, appreciable NO3‐N was also present at the medium rate, but NO3‐N was low at this rate in Year 11. The high P concentrations in the surface soil increase the potential for runoff transport of P, which might pose a surface‐water pollution problem.
Application of Ecological Classification to Environmental Effects Analysis
Authors: Jensen Mark E. , McNicoll Cecilia H. , Prather Martin
Published: July 2010

The Northern Region of the USDA‐FS has developed an efficient and consistent method for assessing environmental effects of management practices on the soil and vegetation resources it administrates. Ecological classification and analysis constitute the basis of this method. Because many of the management activities in the region alter the present vegetation of a site (and consequently its values for a variety of resource uses) an understanding of plant succession relationships is critical to proper effects analysis. The ecological approach to effects analysis presented in this paper has proven effective in the Northern Region and is applicable to other wildland areas.
Salinity and Boron Tolerances of Candidate Plants for the Removal of Selenium from Soils
Authors: Parker D.R. , Page A.L. , Thomason D.N
Published: July 2010

Agricultural drainage water from the west side of the San Joaquin Valley, CA is highly salinized, and is often contaminated with an assortment of metals and metalloids, including Se. Among proposed disposal options, vegetation management may be a critical component of remediation strategies designed to reduce soil or sediment concentrations of Se to safe levels. Soil salinity (mostly sodium sulfate) and B pose serious limitations to the use of many plant species. We screened a number of cultivars or lines of species from the genera Astragalus, Leucaena, Medicago, Trifolium, Elymus, Elytrigia, Festuca, Leymus, Oryzopsis, Psathyrostachys, Puccinellia, and Sporobolus for tolerance to salinity and B using solution culture methods. Considerable variation in tolerance to salinity, both within and across species, was observed during seed germination. Electrical conductivities required to produce a 50% reduction in germination (EC50) ranged from 5 to 30 dS m−1. Boron levels up to 4.0 mM had only minimal effects on germination. The most promising genotypes, representing some 15 species, were then tested for salinity and B tolerance during the seedling growth stage. Lines of five species (Astragalus bisulcatus, A. racemosus, Elytrigia pontica, Puccinellia dlstans, and Sporobolus airoides) appeared most promising; all exhibited EC50 values > 20 dS m−1 and were unaffected by B concentrations up to 4.0 mM during seedling growth. Astragalus bisulcatus and A. racemosus are considered primary accumulators of Se; their tolerance of high salinity and B daring seedling growth make them particularly good candidates for remediation of Se‐enriched soils and sediments.
Microlysimeter Soil Columns for Evaluating Pesticide Movement through the Root Zone
Authors: Fermanich K. J. , Daniel T. C. , Lowery B.
Published: July 2010

Field approaches to studying pesticide movement are subject to numerous variables of the environment, many of which are difficult and expensive to monitor. This study describes the design, construction, operation, and performance of intact microlysimeter soil (Plainfield loamy sand—mixed, mesic, Typic Udipsamment) columns used to examine the mobility of two insecticides through soil from two tillage plots (conventional‐moldboard plow and no‐till tillage). Field leaching conditions were approximated by simulating a moisture and temperature regime characteristic of a natural soil profile. Measured daily and seasonal temperature fluctuated according to a pattern characteristic of a field soil. Evapotranspiration (ET) from the soil columns was 61% of the total water applied and was nearly equal to the ET measured (63%) from field lysimeters of this soil planted to corn (Zea mays L.). Variation in cumulative drainage was small; total drainage from all columns was within a range of 3.9 cm. There was no significant difference in the transport of bromide (conservative tracer) through columns from the two tillage plots. Bromide leachate loss was 62 and 63% of the amount applied for conventional‐moldboard plow and no‐till columns, respectively. Intact soil columns established in a microlysimeter fashion provided a means to compare the movement of agricultural chemicals under controlled conditions in the greenhouse that approximate conditions/processes in the field.
Laboratory Measurements of Diffusion Coefficients for Trichloroethylene and Orthoxylene in Undisturbed Tuff
Authors: Fuentes H. R. , Polzer W. L. , Smith J. L.
Published: July 2010

Exploratory laboratory research was performed to evaluate the fate of two organic contaminants in the unsaturated zone of the Bandelier Tuff at Los Alamos National Laboratory chemical waste site. Studies concentrated on vapor phase diffusion for trichloroethylene and orthoxylene known to occur in significant amounts at the site. This research was undertaken in support of the geohydrological characterization of the unsaturated zone and ultimately to facilitate environmental transport predictions. In these vapor phase diffusivity studies a laboratory method was developed for direct measurement of gaseous diffusion through undisturbed cores of Bandelier Tuff. Core preparation required careful handling to maintain the in situ structure of the tuff samples, which were mostly cohesionless. Effective diffusion coefficients were calculated from a one‐dimensional steady‐state solution of Fick's first law. Effective diffusion coefficients for the target organics were determined for samples from two locations within each of two lithologic units of the Bandelier Tuff at two average extreme moisture contents, 1 to 3% and 12 to 15% (by mass). The higher moisture content decreased the flux of the organics by approximately one order of magnitude. Differences among effective diffusion coefficients between sampling locations and lithologic units were not significant for each organic at a 5% significant level. Results provide an insight on the effect of moisture content, but data are needed to further develop or validate a relationship between diffusion and moisture content.
Railway Right‐of‐Way Contaminants in the Lower Mainland of British Columbia: Polycyclic Aromatic Hydrocarbons
Authors: Wan Michael T.
Published: July 2010

Ballast from five railway rights‐of‐way and the adjacent ditches flowing to salmon streams in the Lower Mainland of British Columbia, Canada, were sampled in 1989 to determine the occurrence and levels of 16 selected polycyclic aromatic hydrocarbons (PAH). Reference and background levels of PAH in ditches leading to fish streams were obtained from pristine parklands and agricultural lands. PAH levels in sediments reported by Goyette and Boyd (1989) for Burrard Inlet (Inner Harbour), the commercial harbour of Vancouver, British Columbia, were used for comparison. All 16 PAH were found in the ballasts and ditch sediments/water of the five railway rights‐of‐way. In the ballasts, total levels of the 16 PAH varied from 1.562‐58.773 g/m2, averaging 18.069 g/m2. The mean concentration of the total 16 PAH in ditch sediments was 213.47 µg/g (range, 1.89‐1168.71 µg/g). PAH were not consistently found in ditch water at all study sites, but at sites where they occurred, the selected 16 compounds had an average total concentration of 606.9 ug/L (range, 1‐3515.9 µg/L). PAH were not detected in the ditches of pristine parklands but low concentrations were detected in some agricultural samples. The total level of the 16 PAH in sediments from railway ditches were respectively 205 and 40 times higher than levels found in the sediments of farmland ditches and Burrard Inlet. Some biological implications of PAH‐contaminated sediments and water from railway ditches discharging into fish habitats are discussed.
The Measurement of Bioavailable Phosphorus in Agricultural Runoff
Authors: Sharpley Andrew N. , Troeger W. W. , Smith S. J.
Published: July 2010

The role of sediment‐bound or particulate P in agricultural runoff in accelerating the biological productivity of surface water can be assessed if the biological availability of particulate P (PP) is known. Previous research has indicated amounts of P extracted from deposited river and lake sediments by 0.1 M NaOH to be correlated with P uptake by the alga Selenastrum capricornutum. This study investigates a modification of this extraction to allow routine quantification of potentially bioavailable particulate P (BPP) content of agricultural runoff from the Reddish Prairies and Rolling Red Plains land resource areas. In the proposed method, 20 mL of unfiltered runoff is shaken with 180 mL of 0.11 M NaOH for 17 h and BPP concentration calculated by subtraction of the soluble P (SP) concentration of the runoff sample. Total bioavailable P concentration (TBP) of runoff can be represented by BPP plus SP concentration. Growth of P‐starved S. capricornutum, incubated for up to 29 d with runoff sediment from nine watersheds, as the sole P source, was correlated (r2 = 0.76 to 0.95) with potentially BPP content of the added sediment. Sample dilution had no effect on the amount of P extracted from runoff sediment by NaOH across a range in sediment concentration of the extraction medium, equivalent to that observed for 95% of the runoff events. If the sediment concentration of runoff exceeds 20 g L−1, a smaller runoff sample is used in the extraction. The results indicate the applicability of the proposed extraction method to quantify the bioavailability of P transported in agricultural runoff.
Water Quality Impacts Associated with Sorghum Culture in the Southern Plains
Authors: Sharpley Andrew N. , Smith S. J. , Williams J. R. , Jones O. R. , Coleman G. A.
Published: July 2010

Nonpoint‐source pollution of surface water by the transport of sediment, N, and P in agricultural runoff is one of the nation's major water quality concerns. Consequently, concentrations and amounts of sediment, N, and P in runoff from Conventional Till (CT), Reduced Till (RT), and No Till (NT), sorghum [Sorghum bicolor (L.) Moench.] watersheds in the Southern Plains, were measured during a 5‐yr period to evaluate water quality impacts of sorghum culture. Mean annual sediment and total N and P loss in runoff from NT (281, 0.76, and 0.28 kg ha−1 yr−1, respectively) and RT (523, 0.99, and 0.37 kg ha−1 yr−1, respectively) were lower than from CT sorghum (8877, 7.28, and 2.5 kg ha−1 yr−1, respectively). In contrast, tillage effects on soluble N and P losses were generally small and less consistent, although soluble P concentrations exceeded limits associated with accelerated eutrophication (0.01 mg L−1). Predicted losses of soluble P and particulate N and P using desorption kinetics and enrichment ratio relationships were not significantly different from measured values for all tillage practices (r2 ranged from 0.66 to 0.99). Overall, conservation tillage (NT and RT) reduced sediment, N, and P transport in runoff relative to CT and thereby lessened the potential impact of sorghum culture on surface water quality in the Southern Plains.
Hydraulic Conductivity and Nitrogen Removal in an Artificial Wetland System
Authors: McIntyre Beverly D. , Riha Susan J.
Published: July 2010

A greenhouse study using aquatic macrophytes rooted in sand was conducted to test if the presence of belowground plant material increases or maintains permeability in horizontal subsurface flow systems constructed for wastewater treatment. Nutrient solutions low in suspended solids (SS) and biochemical oxygen demand (BOD) were substituted for actual wastewater. Three batch applications of NH4‐N and three of NO3‐N were added for 48‐h periods at concentrations of approximately 20, 55, and 80 mg L−1 to assess the ability of these systems to remove N. Saturated hydraulic conductivity, Ks, was monitored over 236 d in boxes of sand planted with two different aquatic macrophytes—Typha glauca Godr. and Scirpus acutus Muhl. The Ks decreased over time in the vegetated and nonvegetated (control) systems. The decrease was significantly greater in the vegetated systems (55%) than in the control (41%). Despite these decreases, Ks at the end of the study was still high (0.62 cm s−1) even in the vegetated systems. The vegetated systems were significantly more effective than the nonvegetated at removal of NH4‐N and NO3‐N. No significant difference was noted in the N removal efficiency of the two plant species. Our results suggest that artificial wetlands using sand can be used to remove N from wastewater, but decreased soil permeability may occur.
Nitrification Potential in Reclaimed Coal Mine Spoils and Soils in the Semiarid Southwest
Authors: Sorensen D. L. , Fresquez P. R.
Published: July 2010

The functioning of the N cycle within mining wastes is necessary for revegetation and long‐term stability of the disturbed ecosystem. In view of this, an undisturbed area and eight reclaimed topsoil‐covered and without‐topsoil spoil areas at the San Juan coal mine in northwestern New Mexico (Fruitland formation, Upper Cretaceous period) were analyzed for initial N contents and nitrification rates to determine the potential of these disturbed but reclaimed areas to cycle N. The age of the reclaimed area varied from 0.2 to 8 yr. Total N, NH+4‐N, and NO−3 NO−2‐N concentrations were significantly higher (P ≤ 0.05) in without‐topsoil spoil areas than in the undisturbed soil or in any of the topsoil‐covered areas. Initial, potential nitrification activity was highest in a 5‐yr‐old reclaimed spoil area that also had the highest extractable NH+4‐N. Ammonium and nitrite oxidation activities were measurable in all of the reclaimed areas and in the undisturbed control. Rates of initial NH+4 and NO−2 oxidation were not well correlated but were similar in magnitude. Mixing as much as 0.75 kg kg−1 spoil material with soil delayed, but did not inhibit, nitrification.
Preferential Solute Transport through Macropores in Large Undisturbed Saturated Soil Columns
Authors: Singh Piyush , Kanwar Rameshwar S.
Published: July 2010

Six large undisturbed soil columns (61 cm in length, 15 cm in diameter) were collected from three no‐till and three conventional tillage field plots. The side walls of these columns were sealed with either plaster of paris or paraffin wax to eliminate wall effects. After these columns were saturated with CaSO4 (0.005 M), CaCl2 (0.005 M) was applied at the surface and the effluent was collected at the bottom. Effluent samples were later analyzed for Cl (chloride) concentrations. The Cl breakthrough‐curves (relative Cl concentration vs. relative pore volume) were developed and the degree of preferential flow analyzed. Shape and other breakthrough‐curve parameters, such as immobile pore‐water fraction and initial breakthrough, indicated the occurrence of preferential flow through all columns. The degree of preferential flow, however, was greater in no‐till than in conventional tillage columns (average immobile pore‐water fraction was 56% for no‐till and 49% for conventional tillage columns).
Nitrogen Leaching Losses from Irrigated Orchardgrass on Sandy Soils
Authors: Watts D.G. , Hergert G.W. , Nichols J.T.
Published: July 2010

Irrigated pasture may provide an alternative forage source for livestock producers in Nebraska's Sandhills. As with any heavily fertilized crop, there is a significant potential for groundwater contamination by nitrate nitrogen (NO3‐N) leached from the crop root zone. A 3‐yr experiment was conducted in West Central Nebraska to evaluate water and nitrate (NO−3) leaching losses from irrigated orchardgrass (Dactylis glomerata L.) seeded on a Valentine fine sand (Typic Ustipsamments). Three irrigation levels (slight deficit, slight excess, and excess) and four N amounts (0, 112, 224, and 336 kg−1) were applied. Deep percolation and NO−3 leaching were measured with Duke‐Haise trough‐type extractors. All irrigation treatments had more deep percolation than expected, as the crop coefficient used for irrigation scheduling proved to be too large. The deficit irrigation treatment served as a “close management” treatment since percolation was minimal and yield was not reduced by water stress. During the first 2 yr of operation, in‐season percolation losses averaged 7, 28, and 47 cm yr−1 for low, medium, and high irrigation levels, respectively. Total in‐season NO3‐N leaching loss for the same period ranged from 6 to 228 kg ha−1, depending on N and irrigation amount. Winter and early spring N leaching losses, as estimated by soil sampling, were a significant part of total N loss. Under reduced inseason drainage and an N rate commensurate with 80 to 85% of maximum production, a minimum annual N leaching loss of 35 kg ha−1 can be expected. Greater losses are probable under average water and N applications and average management skills.
Effects of Soil‐Applied Selenium on the Growth and Selenium Content of a Forage Species
Authors: Carlson Claire L. , Adriano Domy C. , Dixon Philip M.
Published: July 2010

This study was conducted to determine the effects of soil‐applied selenate and selenite on the growth and Se content of a forage species, sorgrass (Sorghum vulgare var. sudanense Hitchc.), grown on acid southeastern soils under different soil conditions. A greenhouse pot study was conducted using a factorial design, with two soil types varying in clay and hydrous oxide content (Blanton sand, a loamy, siliceous, thermic Grossarenic Paleudult; and Orangeburg loamy sand, a loamy, siliceous, thermic Typic Paleudult), two soil treatments (limed and unlimed), two Se forms (selenate, SeO2−4, and selenite, SeO2−3), and four Se concentrations (0, 1, 2, and 4 mg Se kg−1 soil). Additions of Se in the selenate form had a greater toxic effect on the plants, reducing plant biomass as much as 97% and increasing plant Se concentrations to as high as 1153 mg Se kg−1. Selenite additions generally did not affect plant biomass, but still resulted in accumulations of Se in aboveground tissues to levels potentially toxic to animals. Selenium concentrations were higher in plants grown on the soil lower in clay and hydrons oxide content. Liming resulted in lower tissue Se concentrations in plants grown on either soil treated with selenate.
Soil Chemistry after Eleven Annual Applications of Cattle Feedlot Manure
Authors: Chang C. , Sommerfeldt T. G. , Entz T.
Published: July 2010

In a long‐term experiment at Lethbridge, AB, the effects of cattle (Bos sp.) manure on soil characteristics were determined after 11 annual applications. Manure, incorporated by cultivating, rototilling, or plowing, was applied annually from 1973 to 1983 at 30, 60, and 90 Mg ha−1 (wet wt.) and 60, 120, and 180 Mg ha−1, respectively, to nonirrigated and irrigated dark brown Chernozemic (Typic Haploborolls) clay loam soil. On both the nonirrigated and irrigated soil, the effects from manure, applied annually at greater than recommended rates for 11 yr, were minimal on Cu and NH4 content and substantial on other parameters determined. There were no significant effects due to tillage methods on these soil parameters. The effects on these soil parameters extended to greater depths under irrigation than under nonirrigation. Most of the applied NH4 was nitrified, volatilized, or fixed. The accumulation of organic matter, total N, NO3, total P, available P, soluble Na, Ca + Mg, Cl, SO4, HCO3, and Zn in the soil increased with increasing rates of manure applied. The electrical conductivity and sodium adsorption ratio of the soil increased and the soil pH in the surface 60 cm of nonirrigated and 90 cm of irrigated decreased with increased manure rates. The total NO3 accumulation in the 150‐cm soil depth was near 1 Mg ha−1, even at recommended rates, and was high enough to potentially cause soil and water pollution. The available P accumulated mostly in the surface soil and might be sufficient to interfere with the nutrient balance of some crops. Long‐term annual application of cattle manure to southern Alberta soils at maximum recommended rates [30 mg ha−1 and 60 Mg ha−1 (wet wt.) for nonirrigated and irrigated land, respectively] is not advisable.
Use of Enzymes to Detoxify Pesticide‐Contaminated Soils and Waters
Authors: Nannipieri P. , Bollag J.‐M.
Published: July 2010

Applying enzymes to transform or degrade pesticides is an innovative treatment technique for removal of these chemicals from polluted environments. Enzyme‐catalyzed degradation of a pollutant by a parathion hydrolase may be more effective than existing chemical methods. Removal of certain pollutants (for instance phenols and aromatic amines) from wastewater may be achieved by applying phenoloxidases that can convert these chemicals to water‐insoluble polymers that can then be removed by filtration or sedimentation. Another decontamination method involves the enzyme‐catalyzed incorporation of pesticides into organic matter. This procedure reduces the mount of leachable pesticides as well as the toxicity and bioavailability of the chemicals. Pesticide‐detoxifying enzymes must be immobilized before they can be used in the environment. In spite of promising potential applications, very few enzymes have been tested as possible tools in the detoxification of pesticides. Research in this domain can contribute greatly to developing new methods for pollution control.
Arsenic and Selenium Chemistry as Affected by Sediment Redox Potential and pH
Authors: Masscheleyn P. H. , Delaune R. D. , Patrick W. H.
Published: July 2010

The influence of sediment redox potential and pH on As and Se speciation and solubility was studied. Hyco Reservoir (North Carolina) sediments were equilibrated under controlled redox (500, 200, 0, and −200 mV) and pH (5, natural, and 7.5) conditions. Redox potential and pH affected both speciation and solubility of As and Se. Under oxidized conditions As solubility was low and 87% of the As in solution was present as As(V). Upon reduction, As(III) became the major As species in solution, and As solubility increased. Total As in solution increased approximately 25 times upon reduction to −200 mV. No organic arsenicals were detected. In contrast to As, Se solubility reached a maximum under highly oxidized (500 mV) conditions and decreased significantly upon reduction. Selenium(VI) was the predominant dissolved Se species present at 500 mV. At 200 and 0 mV, Se(IV) became the most stable oxidation state of Se. Under strongly reduced conditions (−200 mV) oxidized Se species were no longer detectable and Se solubility was controlled by the formation of elemental Se and/or metal selenides. Biomethylation of Se was important under oxidized and moderately reduced conditions (500, 200, and 0 mV). More alkaline conditions (pH 7.5) resulted in both greater As and Se concentrations in solution. Dissolved As and Se increased up to 10 and 6 times, respectively, as compared to the more acidic equilibrations.
Off‐Field Movement and Dissipation of Soil‐Incorporated Carbofuran from Three Commercial Rice Fields
Authors: Nicosia S. , Carr N. , Gonzales D. A. , Orr M. K.
Published: July 2010

Residues of curbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate) were detected in agricultural drain water collected in the Sacramento Valley, a major rice (Oryza sativa L.) growing region of California. Runoff water from rice fields was suspected as the major source for these residues. In response to this problem we measured soil‐incorporated carbofuran; (i) discharged in runoff, (ii) dissipated from paddy soil and water, and (iii) recovered in paddy soil vs. paddy water over time. This work was conducted in three commercial rice fields in Colusa and Glenn Counties in California. A total of 1.72, 5.40 and 11.03% of carbofuran mass applied was discharged in runoff water from Fields 1, 2, and 3, respectively, during a 54‐ to 80‐d period after flooding. Downstream concentrations, up to 4.4 µg L−1, indicated the need for reduced carbofuran discharges to meet a 1991 regional standard of 0.4 µg L−1. Most of the carbofuran lost in runoff was discharged during the first 30‐d period after initial flooding in Field 2, and during the 31‐ to 60‐d period in Fields 1 and 3. Dissipation of carbofuran mass, measured separately in rice paddy soft and rice paddy water, was a log‐linear function of time in both media. An exception occurred in paddy soil of Field 3 where carbofuran mass did not decline significantly over a 70‐d sampling period. Soil half‐lives were 58 and 43 d after flooding for Fields 1 and 2, respectively. Water half‐lives for Fields 1, 2, and 3 were 22, 26, and 18 d, respectively. Most of the carbofuran mass applied to the fields remained in paddy soil and, on average, no more than 27% of the applied mass was found in paddy water on any single day during the study. Soil‐incorporation may reduce the amount of carbofuran released into paddy water, and subsequently moved off‐field in runoff.
Response of Net Carbon Exchange Rate of Soybean to Ozone at Different Stages of Growth and its Relation to Yield
Authors: Miller Joseph E. , Pursley Walter A. , Vozzo Steven F. , Heagle Allen S.
Published: July 2010

High concentrations of ozone (O3) occur episodically during the growing season, but the impacts of O3 stress on photosynthesis and crop yield when O3 episodes occur at various stages of growth are not known. Also, quantitative relationships between reduction of photosynthesis and yield suppresion by O3 have not been established for most species. Field experiments with soybean [Glycine max (Merr.) cv. Davis] were performed to determine the impact of O3 exposure at different stages of plant development on net carbon exchange rate (NCER) and to establish the relationship between NCER and yield for different O3 exposure periods. The growing season was divided into four quarters (Q1–Q4) of 31 d each for O3 treatment. In each quarter, O3 treatments in open‐top chambers were either charcoal‐filtered air (C) or nonfiltered air (N) to which O3 was added to achieve approximately 100 nL L−1 O3 (mean 7 h d−1 average for the quarter). The NCER was measured in eight O3 treatments (CCCC, NNCC, CNCN, NCCN, CNNC, NCNC, CCNN, and NNNN) where each letter indicates the O3 treatment for successive quarters. The NCER measurements during Q4 (R6–R7) provided the best relationship to yield in a linear regression model (R2 = 0.919). A significant relationship with yield was obtained also with NCER measurements from Q3 (R2–R5) (R2 = 0.626), whereas measurments during Q2 (V10‐R1) were poorly related to yield (R2 = 0.072). Good linear relationships of yield and NCER were found also when Q3 and Q4 or Q2, Q3, and Q4 data were combined. In all cases, however, Q4 data were essential to a good correlation between NCER and yield. It is likely that NCER measurements taken during Q4 correlated well with yield, because that was the period when the requirement for energy from photosynthesis is most critical for yield.
Effects of Collection Interval on Quality of Throughfall Samples in Two Northern Hardwood Stands
Authors: Liechty Hal O. , Mroz Glenn D.
Published: July 2010

The chemical stability of weekly and biweekly throughfall collection intervals were compared at two northern hardwood stands in the Great Lakes region. Throughfall concentrations of Cl−, NO−3, SO2−4, Ca2+, Mg2+, and K+ were not significantly (p ≤ 0.05) affected by the increased collection time, where as throughfall concentrations of NH+4 and H+ collected biweekly were significantly different (p ≤ 0.05) than concentrations of these ions in weekly samples. The 1‐wk increase in collection interval at one stand decreased concentrations of NH+4 and increased concentrations of H+ 88 and 131%, respectively. The chemical instability of these ions appeared to be related to biological assimilation and/or nitrification of NH+4. Stability of these ions decreased with increasing concentrations of inorganic N in the throughfall. These changes in concentrations of NH+4 and H+ may introduce sampling bias when estimating throughfall fluxes or concentrations of these ions from biweekly collections. The decreased stability of these ions with increased concentrations of inorganic N should be an important consideration when selecting sampling intervals for stands that receive differing deposition levels of atmospheric N or have different canopy retention rates of N.