bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxygen Transport through Selected Aquatic Macrophytes
Authors: Moorhead K. K. , Reddy K. R.
Published: July 2010

The extent of O2 transport from aerial plant tissue into the root zone was evaluated for several floating and emergent aquatic macrophytes that have characteristics favorable for wastewater treatment. The highest O2 transport rates from aerial tissue into the root zone were associated with plants having a small root mass. As root mass increased, the rate of O2 transport decreased for aquatic macrophytes evaluated. Pennywort (Hydrocotyle umbellata L.) had the highest O2 transport rate of all aquatic macrophytes with an overall rate of 3.49 g O2 kg−1 dry root mass h−1. Pickerelweed (Pontederia cordata L.) had the highest O2 transport capacity of emergent plants with a rate of 1.54 g O2 kg−1 h−1. Waterhyacinth [Eichhornia crassipes (Mart.) Sollms], an important floating aquatic plant in wastewater treatment, had a transport rate of 1.24 g O2 kg−1 h−1. Nitrification in a waterhyacinth‐based water treatment system due to O2 transport was calculated to vary from 6 to 22 kg ha−1 d−1.
Nitrogen Dioxide Effects on Photosynthesis in Soybean
Authors: Sabaratnam Sashikala , Gupta Gian , Mulchi Charles
Published: July 2010

Very little information is available on the effects of nitrogen dioxide (NO2) on photosynthesis in soybean [Glycine max (L.) Merr.]. This investigation was undertaken to study the effects of NO2 (0.0, 0.1, 0.2, 0.3, and 0.5 µL/L) on net photosynthetic rate (PN), stomatal resistance (SR), and dark respiration rate (DR) of soybean cultivar Williams treated 7 h/d, for 5 d in a controlled environment. Measurements of PN, SR, and DR were made both immediately and 24 h after the termination of exposure, using a LICOR 6000 Portable Photosynthesis system. Treatment effects on PN and DR were statistically significant. Increases of 18 and 23% in PN were observed immediately following exposure to 0.2 µL/L NO2 and after a 24‐h recovery period. With the 0.5 µL/L NO2 treatment reductions in the PN of 23 and 50% were observed immediately after exposure and following the 24‐h recovery period. Dark respiration rates of leaves treated with NO2, 0.2 µL/L, were 13 and 46% higher than the control immediately after the exposure and after the 24 h recovery. Exposure to 0.2 µL/L of NO2 had a stimulating effect whereas 0.5 µL/L of NO2 inhibited photosynthesis in soybean.
Effects of Forest Floor Leachate on Sulfate Retention in a Spodosol Soil
Authors: Gobran George R. , Nilsson S. Ingvar
Published: July 2010

Because of the involvement of several different mechanisms, sulfate retention in forest soils is a rather complicated process. We have investigated the effect of the dissolved substances from the forest floor of a Haplorthod soil (A0 horizon) on SO2−4 mobility in the upper mineral soil (A1/A2 horizon). Sulfate retention (SO2−4 retained in a solid phase) was estimated using two different solutions—distilled water solution (DWS) and forest floor leachate (FFL). Different concentrations of SO2−4 (0.00–2000 mg S L−1) were added to both extractants as Na2SO4‐35S. The results show that sulfate retention by the mineral soil (A1/A2) increased linearly with increasing SO2−4 concentration in the DWS containing up to 500 mg S L−1, whereas retention was zero when the soil was equilibrated with the FFL containing <250 mg S L−1. However, retention started to increase linearly when the FFL contained more than 250 mg S L−1. These data indicate that in the range of SO2−4 found under field conditions, SO2−4 retention was completely inhibited by the leachate solutions. These data also suggest that the organic ligands in the FFL were competing with SO2−4 on the exchangeable positive charge sites. Moreover, they may have an inhibitory effect on the growth of some SO4‐Al mineral compounds, mainly jurbanite and/or basaluminite.
Disposal of Septic Tank Effluent in Calcareous Sands
Authors: Whelan B. R.
Published: July 2010

Perth, Western Australia, has 430 000 households with septic tanks discharging through sandy soils into the groundwater, which is pumped for domestic irrigation and public water supply. This study investigated the suitability of calcareous sands (Xeropsamment), one of Perth's major soil types, for treatment of septic tank effluent. Calcareous sands adjacent and below two septic tank systems were sampled to a depth of 8 m and the soil pH, soil N, and soil P contents were measured. The soil solution was sampled by an immiscible displacement technique and analyzed for N and P. Most of the NH4‐N in the effluent was oxidized to NO3‐N in the unsaturated zone just below the slime layer. Nitrate (NO−3) was present in the soil solution up to a concentration of 50 mg L−1 down to the maximum depth sampled of 8 m. The acidity produced during nitrification of the NH4 dissolved carbonates from the soil changing the soil pH. Below one system, the carbonates were completely removed from the first 4 m of soil lowering soil pH from 9.5 to 5.2. The NO3 in the soil solution was used to monitor the effluent flow pattern, which below one system had significant lateral flow indicating development of preferred flow paths. The soil P was increased by sorption and precipitation of P from the soil solution until it reached an equilibrium. At equilibrium the soil solution P was at the same concentration as in the effluent and the P sorbed on the soil was at a maximum for that concentration. Further down the profile where the sorbed soil P was not at its maximum, all the P was sorbed from the soil solution in a vertical distance of 0.5 m. The suitability of calcareous sands and limestone areas for acidic waste disposal may be limited by rapid dissolution of carbonate and the consequent release of previously sorbed P. Monitoring of effluent disposal in these calcareous soils is made more difficult by the development of preferred flow paths.
Microbial Biomass and Activity in a Subarctic Soil Ten Years After Crude Oil Spills
Authors: Sparrow Stephen D. , Sparrow Elena B.
Published: July 2010

This study documents the residual effects of summer and winter experimental oil spills on soil 10 yr after application. Measurements included adenosine triphosphate (ATP) levels, in vitro carbon dioxide evolution, cellulose and wood decomposition, soil N, and total and non‐oil C. About 18 and 14 kg petroleum residues per m2 remained in the soil in the winter and summer spills, respectively, and no reinvasion of plants had occurred in areas heavily impacted by the spills. Soil ATP levels averaged about 100 mg m−2 in the control soils and were about threefold higher than in the oiled soils, indicating reduced microbial biomass in the oily soils. There were no differences in in vitro CO2‐C evolution rates in the three soils, suggesting that there were similar levels of available substrate in both oiled and control soils. Cellulose and wood decomposition rates in the field were much lower in the oiled plots than in the unoiled soil. Nonpetroleum organic C levels averaged about 12 kg m−2 and were not significantly different between control and oiled soils, indicating that in the field little decomposition of organic matter had occurred in the oiled plots. Total N levels averaged about 5.5 kg m−2 in the oiled plots, which was significantly higher than the 4 kg N m−2 in the control plots. This was possibly due to N deposition of parts of plants killed by oil and to N2 fixation coupled with reduced N losses from the oiled soils. Ammonium‐N accumulated in the oiled soils at much higher levels than in the control soil. Results of this study showed that crude oil spills in subarctic forests can have long‐lasting effects on soil biological properties.
Growth and Uptake of Selenium by Swiss Chard in Acid and Neutral Soils
Authors: Zhang Penchu , Ganje T. J. , Page A. L. , Chang A. C.
Published: July 2010

The absorption of Se by plants in acid and neutral soils in relation to the concentration and chemical form of Se added was studied. Selenate‐Se added to an acid soil in amounts equal to or greater than 1.0 mg kg−1 significantly reduced yields of Swiss chard (Beta vulgaris L. var. cicla). Selenite‐Se, however, added to the acid soil at levels up to 2 mg kg−1 did not affect yields. Likewise, yields were also unaffected when selenite or selenate was added alone or in combination to a neutral soil at levels up to 2 mg Se kg−1. Amounts of Se absorbed by plants from soils where selenate was added were greater than where selenite was added. Selenate added to the soils was, in part, reduced to selenite during the growth period.
Atmospheric Sulfur Deposition to Agricultural Land in Northeastern Ohio
Authors: Morra M. J. , Dick W. A.
Published: July 2010

In certain forms, S is an important acid‐forming substance deposited from the atmosphere to the earth's surface. Controversy surrounds estimates of total S deposition because of an inability to accurately measure S in dry deposition (particulate fallout and gaseous sorption). In a field experiment in northeastern Ohio, the amount of S in dry deposition was determined over a 3‐yr period using 20 lysimeters (4.8 m by 1.7 m) cropped with soybean [Glycine max (L.) Merr.]. Two treatments consisting of tillage (conventional or no‐tillage) and elemental S addition (0 or 50 kg ha−1) were applied to the lysimeters. Sulfur inputs to the lysimeters as precipitation and agricultural amendments and S outputs, as runoff and leachate waters, were determined using ion chromatography or alkaline oxidation techniques. The net S output (total outputs minus measured inputs) was considered to equal dry deposition. Precipitation and agricultural amendment inputs of S were 10.2 and 3.8 kg ha−1 yr−1, respectively. In comparison, S in dry deposition ranged from 14 to 26 kg ha−1 yr−1 for the conventional tilled treatment and from 25 to 39 kg ha−1 yr−1 for the no‐tilled treatment, with the upper values of these ranges considered most accurate. Dry deposition is clearly as important as precipitation in contributing to the total S load at this location. A sulfur dry deposition estimate of only 15 kg ha−1 yr−1 was made based on average deposition velocity and ambient SO2 levels. Total deposition models, which rely on dry deposition estimates obtained by the use of SO2 concentrations and an average deposition velocity, may yield inaccurate values of total S additions to the earth's surface.
Effects of Simulated Acidic Precipitation on Plant‐Insect Interactions in Agricultural Systems: Corn and Black Cutworm Larvae
Authors: Stinner Deborah H. , Stinner Benjamin R. , McCartney David A.
Published: July 2010

Effects of simulated acidic precipitation on food utilization, growth, development, and herbivory of black cutworms (Agrotis ipsilon) on corn (Zea mays L.) in the most economically important life‐history combinations of plant and insect were investigated in a series of laboratory and greenhouse experiments. A nutritional‐index technique was used in petri‐dish experiments with fourth, fifth, and sixth instar black cutworms to determine if acid precipitation could affect the amount of food consumed via affects on insect physiological parameters. Larvae were fed corn plants that were watered two times weekly with simulated precipitation (pH 2.8, 4.2, and 5.6) until the larvae pupated (total deposition of 8–10 cm of precipitation). The inverse relationship between the index of approximate digestibility (AD), which was higher in the pH 2.8 and 5.6 treatments, and the efficiency of conversion of digested food indices (ECD), which was lowest in the pH 2.8 treatment, suggested a stress effect of high acidity. A series of six greenhouse pot experiments was conducted to assess effects of acid precipitation on black cutworms and their interactions with growing corn plants. Fourth, fifth, and sixth instar larvae were placed in pots containing soil and corn plants, which were initially in the first or second leaf stage, and simulated acid precipitation (pH 2.8, 4.2, and 5.6) was applied two times per week until the larvae pupated (8–16 cm total deposition). Significant treatment effects were observed in the sixth instar larvae on two‐leaf corn experiment, where the larvae grew larger and developed faster in the pH 2.8 and 4.2 treatments than in the 5.6 treatment. Acid precipitation treatments did not significantly affect black cutworm damage to corn plants in any of these experiments.
Preferred Movement of Nonadsorbed Chemicals on Wet, Shallow, Sloping Soils
Authors: Steenhuis Tammo S. , Muck Richard E.
Published: July 2010

Preferred movement of chloride and nitrate during runoff events following nutrient application was studied experimentally on 109 m long fields with a hard pan at shallow depth near Ithaca, NY. Chloride and nitrate applications were surface‐applied and incorporated at 36 and 69 m uphill from the collection point. All of the applied chemicals, when surface‐applied on saturated soil, were completely lost in the surface runoff and interflow water. When incorporated, at most 60% of the mass applied was lost. The fraction lost appeared to be related to the initial moisture content of the soil. After a chemical application, the concentration in both runoff and interflow was initially high and then decreased exponentially. The concentrations in the runoff water, interflow, and macropores were approximately equal throughout a runoff event.
Is Water a Relevant Sampling Medium for Toxic Chemicals? An Alternative Environmental Sensing Strategy
Authors: Ongley Edwin D. , Birkholz Detlef A. , Carey John H. , Samoiloff Martin R.
Published: July 2010

Using an uncomplicated 960 km reach of the North Saskatchewan River, we examine pathways and distribution of anthropogenic contaminants in water and in suspended and bottom sediments. Synoptic sampling during stable low flow allows maximum inference of point sources and, therefore, of chemical complexity. After chemical extraction of contaminants into two fractions for aqueous samples, and five fractions for sediment samples, we are able to assess the toxicity of the fractions using two independent bioassays—the Panagrellus redivivus nematode assay and a nonstandard modification of the Ames bacterial test. Our observations include (i) little comparability between toxic response of whole water samples and suspended sediments contained in the whole water samples; (ii) a much greater toxic response and larger number of priority chemicals associated with suspended sediments than in water samples; (iii) observed priority chemicals can exist in water or on sediments, yet produce no toxic response in one or both of the bioassay procedures; and (iv) significant toxicity is observed in the absence of priority chemicals. Results lead to questioning of efficacy of a standard menu of priority chemicals applied to water samples for ambient (i.e., not end‐of‐pipe) aquatic quality sensing (monitoring) purposes. We conclude that water may be an inappropriate medium upon which to base toxic chemical criteria for toxic chemical sensing purposes in aquatic systems. The menu approach to toxic chemical sensing is neither cost nor information efficient. We propose an alternative sensing protocol using a coupled chemical‐bioassay protocol that reduces the number of chemicals analyzed, produces an objective biological index of relative toxic response, provides a backup for presence of toxic chemicals not included in the chemical screen, and conveys meaningful ecological information upon which agencies can make program decisions.
The Effects of Leaching and Whole‐tree Harvesting on Cation Budgets of Several Forests
Authors: Johnson D. W. , Kelly J. M. , Swank W. T. , Cole D. W. , Van Miegroet H. , Hornbeck J. W. , Pierce R. S. , Van Lear D.
Published: July 2010

The effects of acid deposition, natural leaching, and harvesting on base cation export from forests in Maine, Tennessee, South Carolina, North Carolina, and Washington were compared. Based on previous literature, we hypothesized that base cation export via whole‐tree harvesting (WTH) would be nearly independent of soil exchangeable base cation supplies; base cation export via leaching would be strongly dependent on the exchangeable cation supplies as well as the input, production, and mobility of anions. This hypothesis was supported by the data: mixed deciduous sites in Tennessee had among the highest base cation (principally Ca) exports via WTH (1.2 kmolc ha−1 yr−1), yet the lowest soil exchangeable supplies (35 kmolc ha−1), whereas the Washington sites had by far the highest base cation leaching (5–41 kmolc ha−1 yr−1, due to very high levels of naturally produced HCO−3) and soil exchangeable supplies, yet only relatively moderate base cation exports via WTH (0.4 kmolc ha−1 yr−1). Sulfate was either the dominant or a major anion in soil solutions from the eastern sites, suggesting that atmospheric deposition was a major factor in soil leaching from these sites (0.2–2.1 kmolc ha−1 yr−1), but total leaching rates from these sites were much lower than at the Washington sites. Indeed, some of the eastern sites showed a net annual accumulation of one or more base cations from atmospheric deposition. Some of the southeastern sites with Ultisols showed the expected net retention of SO2−4, but the sites in the Tennessee Valley near Oak Ridge showed surprisingly little ecosystem SO2−4 retention, perhaps due to lower soil SO2−4 adsorption in these soils than in other Ultisols.
The Distribution of Fallout Cesium‐137 in Southern Saskatchewan, Canada
Authors: Kiss J. J. , de Jong E. , Martz L. W.
Published: July 2010

Cesium‐137 is a radioactive fallout isotope that is strongly adsorbed by soil particles and has been used by numerous researchers to estimate soil erosion and deposition. In this study, background or baseline levels of 137Cs on native, noneroded soils in southern Saskatchewan are presented. The activity of 137Cs in well‐drained, native soils was measured at 363 sites in the agricultural portion of Saskatchewan. The 137Cs activity at these sites was believed to reflect fallout input to the land surface and therefore represent the background 137Cs activity levels for the sites. In this regional study, 137Cs activity levels in native soils were found to range from 840 to 4570 Bq m−2, with a mean of 2422 ± 505 Bq m−2. The spatial variation in 137Cs activity was complex, and could not be adequately described by a second‐order trend surface function. In the study area there was a general trend toward increasing 137Cs activity with increasing precipitation during the peak fallout period; however, the relationship showed a great deal of scatter. The variation in 137Cs activity levels in the native soils was considered to be largely caused by local meteorological conditions during the peak 137Cs fallout period. Accurate local determination of background 137Cs activity levels for erosional studies in southern Saskatchewan must be based on local sampling of native soils, as predictions based on either location or local precipitation amounts are unlikely to be adequate.
Annual Elemental Input/Output Estimates for Two Forested Watersheds in Eastern Tennessee
Authors: Kelly J. M.
Published: July 2010

Atmospheric inputs of SO2−4, NO−3, PO3−4, NH+4, Ca2+, Mg2+, Na+, and H+ via wet and dry deposition were compared to stream water outputs at two study sites, Camp Branch and Cross Creek, during the period 1978 to 1983. The Cross Creek site is located 19 km from a major coal‐fired point source and has been subjected to approximately 30 yr of elevated atmospheric input while Camp Branch is located in an area removed from the possible local influences of a major point source. Hydrologic comparison of mean streamflow output to incoming precipitation indicates a greater loss of water (64%) to streamflow at Cross Creek than Camp Branch (56%). No site differences (p = 0.05) could be detected in mean annual wet input for any element. The dryfall comparison indicated only a higher level of Mg2+ input at Cross Creek. The relative contributions of anions and cations in both wetfall and dryfall was similar at both sites with SO2−4 > NO−3 > PO3−4 for the anions and H+ > Ca2+ > NH+4 > Na+ > Mg2+ > K+ for the cations. Export of anions in streamflow had the same relative relationship as observed for wetfall and dryfall. The SO2−4 ion accounted for 86% of the measured anion export at Camp Branch and 91% at Cross Creek. Although SO2−4 export varies between sites as a function of flow, concentration values remain relatively constant from year to year. Cation export was dominated by Mg2+ at Camp Branch, followed by Ca2+ > Na+ > K+ > NH+4 > H+. At Cross Creek, the order of cation export was Mg2+ > Ca2+ > Na+ > K+ > H+ > NH+4. Comparing base cation inputs to outputs, there is a mean efflux of 203 molc ha−1 yr−1 at Cross Creek. Although SO2−4 retention rates are 78% of input, it is still the dominant measured companion anion, although there is circumstantial evidence for a substantial HCO−3 contribution. The H+ ion input is also almost completely retained within the system. Base cation loss at Cross Creek was 31% higher than that at Camp Branch. However, it is difficult to demonstrate any significant impact of the elevated historical S input because nutrient export was highly correlated with streamflow and streamflow volume was 29% higher at Cross Creek.
Efficacy of Various Sorbic Media in Attenuation of Selenium
Authors: Fritz Steven J. , Hall Steven D.
Published: July 2010

A series of adsorption tests were performed on material used in the construction of a clay‐lined fly‐ash waste pile at a lignite‐burning power plant in Texas to determine which soil component is the most effective in adsorbing selenium. Selenium, in the form of selenite, is adsorbed by hydrous iron oxides to a greater extent than selenite adsorbed by clays chemically treated to remove organics and free iron. In natural systems, clays will be coated by iron oxides and organic material, and these coatings may prevent anions like HSeO−3 and SeO−23 from sorbing onto positive exchange sites of clay surfaces. However, anions can be effectively adsorbed by these highly reactive surface coatings. Thus, the efficacy of clay as an adsorption medium may be overestimated in construction of environmental barriers for retention of elements like selenium.
Long‐term Phytoavailability of Soil‐applied Organo‐borates
Authors: Adriano D. C. , Kaplan D. I. , Burkman W. G. , Mills G. L.
Published: July 2010

Sodium tetraphenylboron (NaTPB) is expected to be used in large quantities to separate radiocesium from high‐level nuclear wastes. Greenhouse experiments were conducted to determine the long‐term effects of NaTPB, diphenylboric acid (DPBA, a major degradation by‐product of NaTPB) and boric acid (BA) on the extractability of soil B and plant B nutrition. Sorgrass (Sorghum vulgare sudanense Hitchc. ‘Dub‐L‐Graze’) was planted in sandy and loamy sandy soils in two separate 2‐yr studies. Results indicate that initial differences between effects of the B sources on biomass, plant B concentration, plant B uptake and hot‐water extractable B disappeared after the first harvest, while differences among these parameters due to soil type and application rate remained throughout the experiments. Extractable soil and plant B concentrations tended to decrease more gradually in the loamy sand than in the sandy soil. Plant toxicity from organic sources was noted only during the first harvest while BA had no adverse effects. Both NaTPB and DPBA reduced biomass, the former more than the latter. Initially, plant B concentrations were higher in NaTPB than BA treatments. The cumulative percentage of soil‐applied B removed after 2 yr by sorgrass remained fairly similar, 20.0 ± 1.7% (1 SD) among B sources and application rates. This suggests that a large fraction of B applied to the soil was not taken up by the plant, presumably due to soil fixation. Biphenyl, another major breakdown product of NaTPB, had no effect on sorgrass growth, tissue B concentration, and soil B concentration.
Bacterial Water Quality Responses to Four Grazing Strategies—Comparisons with Oregon Standards
Authors: Tiedemann A. R. , Higgins D. A. , Quigley T. M. , Sanderson H. R. , Bohn C. C.
Published: July 2010

Concentrations of fecal coliform (FC) and fecal streptococcus (FS) were measured weekly during summer 1984 in streamwater of 13 wildland watersheds managed under four range management strategies. The strategies were (A) no grazing; (B) grazing without management for livestock distribution; (C) grazing with management for livestock distribution; and (D) grazing with management for livestock distribution and with cultural practices to increase forage. Counts of FC were compared to Oregon water quality standards. Data for FS were used for determining the FC/FS ratio to assess origin of FC organisms. Counts of FC were significantly lower under strategies A and C than under strategy D, but no significant differences were apparent among other strategy comparisons. Two strategy D watersheds violated the Oregon water quality 30‐d log10 standard of no more than 2 × 103 FC L−1 (200 FC·100 mL−1). One watershed was in violation for most of the sampling period. Ratios of FC to FS indicated that wildlife was the major source of FC bacteria in strategies A, B, and C watersheds. Cattle were the primary source of FC bacteria on strategy D watersheds.
Shallowly Placed, Low Pressure Distribution System to Treat Domestic Wastewater in Soils with Fluctuating High Water Tables
Authors: Stewart L. W. , Reneau R. B.
Published: July 2010

Soils with seasonal fluctuating high water tables are common in the Atlantic Coastal Plain and are considered to be unsuited for conventional on‐site wastewater disposal systems (OSWDS). This study was conducted to monitor the performance of a shallowly placed, low pressure OSWDS in a Typic Ochraquult. Low pressure distribution and shallow placement were used to achieve uniform distribution and maintain an unsaturated zone in the more biologically active upper soil horizons. This combination was used to reduce movement of bacteria and P while utilizing water table fluctuations to enhance denitriflcation. Changes in water table levels, effluent distribution, and movement of fecal coliforms and selected chemical contaminants in groundwaters were monitored in situ from December 1980 through May 1982. An unsaturated zone was present beneath the OSWDS during the entire study except for the period from January through May of 1982. During this period the water table intersected the OSWDS, for some time interval (<24 h), on 36 d primarily following large rainfall events. Movement of fecal coliforms and P were restricted both horizontally and vertically. Nitrate concentrations were highest beneath the OSWDS during periods of rising water tables following prolonged periods of time when the water table was deeper than 1.5 m. Following the accumulation of NO−3‐N in the upper portion of the water table, NO−3‐N concentrations decreased rapidly. The observed decrease in NO−3‐N was attributed to denitriflcation and was supported by NO−3‐N/Cl− ratios. Based on NO−3‐N/Cl− ratios, approximately 90% of the NO−3‐N could not be accounted for with increased distance from the OSWDS.
Implications of a Global Climatic Warming for Agriculture: A Review and Appraisal
Authors: Smit B. , Ludlow L. , Brklacich M.
Published: July 2010

Recently it has been recognized that changes in the chemical composition of the atmosphere are likely to alter the earth's climate, and that these alterations may have severe implications for agriculture and other economic activities. This has stimulated research into the possible consequences of altered climatic regimes on several attributes or components of agri‐food systems. Current consensus suggests that a global climatic warming, induced by increased concentrations of CO2 and other “greenhouse” gases, is likely, and hence the possible implications of warmer climates for agriculture has received considerable attention. Several analytical procedures have been employed in these studies and it is timely to assess the characteristics and achievements of these independent efforts. This paper classifies and reviews studies that examine the implications of climatic warming for agriculture. Three approaches to assessment are recognized. Crop yield analysis identifies the effects of a specified change in climate on productivity levels for individual crops in particular locations. Spatial analysis examines the implications of climatic warming for the area and location of lands suitable for crop production. Agricultural systems analysis focuses on the relationships among components of agri‐food systems. Much remains to be learned about the effects of climatic warming on agriculture. The use of existing information to develop a comprehensive analysis is hampered by differences in analytical approaches and in climatic change scenarios, and by the virtual absence of information on the possible implications of climatic change on agriculture in developing nations. Nevertheless, current evidence suggests that a warmer climate could create a more favorable environment for wheat (Triticum aestivum L.) and grain corn (Zea mays L.) in Canada, Northern Europe, and the USSR, and restrict opportunities in the USA.
Quality of Diets with Fluidized Bed Combustion Residue Treatment: I. Rat Trials
Authors: Cahill Nancy J. , Reid R. L. , Head M. K. , Hern J. L. , Bennett O. L.
Published: July 2010

Feeding trials were conducted with rats (Rattus rattus) to examine effects of soil application, or dietary inclusion, of fluidized bed combustion residue (FBCR) on the composition and quality of foods. Four diets (vegetable protein, egg protein, chicken, chicken + dietary FBCR) prepared with either FBCR or lime (control) treatments, were fed to weanling, female rats in three growth and reproduction trials. Intake, growth rate, and composition of body and organs of rats were measured. Rats in one trial were bred, their litters maintained on dietary treatments, and the offspring rebred. Treatment (FBCR vs. lime) × diet interactions on food composition and animal responses generally were not significant. Treatment had little effect on element composition of diets; mineral concentrations were in normal ranges. Diet treatment with FBCR depressed (P < 0.01) food intake and growth of rats in one trial, but not in others, and had no effect (P < 0.05) on body water, protein, ether extract, or gross energy composition. Some differences in element concentrations in the carcass and organs of rats and pups resulted from FBCR treatment, but effects were small and inconsistent. Litters from the first reproductive cycle appeared normal, except for animals fed the chicken + dietary FBCR treatment, on which pups showed poor growth and anemia. Offspring from certain diets were rebred and litters showed a high mortality, although this was not associated specifically with FBCR treatment. Results indicated no major detrimental effects on food composition, or growth, tissue element accumulation, and reproduction in the rat relating to use of FBCR as a soil amendment.
Quality of Diets with Fluidized Bed Combustion Residue Treatment: II. Swine Trials
Authors: Whitsel T. J. , Reid R. L. , Stout W. L. , Hern J. L. , Bennett O. L.
Published: July 2010

Growing pigs (Sus scrofa domesticus) were fed for an 8‐wk period in two trials on diets produced on soils treated with fluidized bed combustion residue (FBCR) or limestone. Diets contained corn (Zea mays L.) and wheat (Triticum aestivum L.) mixtures with soybean [Glycine max (L.) Merr.] meal, supplemented with vegetables, fruits, and meat. Pigs were fed ad libitum and effects of diet treatment on rate of gain, N balance, blood composition, and element composition of the carcass and organs were determined. The FBCR diet caused a decrease (P < 0.05 in Trial 1, P < 0.07 in Trial 2) in body weight gains of pigs, but increased (P < 0.05) N retention in one trial. Blood composition was not influenced markedly by diet treatment, with small but significant differences in serum Ca, triglycerides, certain amino acids, and whole blood Pb concentrations; effects were not consistent between trials. Urinary As concentration was slightly higher for pigs on FBCR diets. Analysis of the carcass and organs of pigs slaughtered posttrial showed significant differences in element levels from those of pretrial animals, but differences in tissue mineral concentrations related to diet treatment were few and inconsistent. Element concentrations in the organs of pigs were within normal ranges. No explanation for the depression in weight gain of pigs fed FBCR‐treated diets was found. Except for the weight response, results support data from other trials with laboratory animals showing no apparent adverse effects of FBCR application to soils on nutritive quality of foods.
Municipal Sludge for Minespoil Reclamation: II. Effects on Organic Matter
Authors: Seaker E. M. , Sopper W. E.
Published: July 2010

A field study of five coal stripmine sites reclaimed with sewage sludge and one site reclaimed with chemical fertilizer was conducted to determine the effects of sludge amendments and time on dry matter yields, detritus accumulation, root growth, organic matter content, and soil organic C and N content. The reclaimed sites ranged in age from 1 to 5 yr following reclamation with sludge at rates of 120 to 134 Mg ha−1 (dry wt. basis). The fertilizer‐amended site was 5 yr old. All sites were planted in grass and legume cover. On the sludge‐amended sites, yield, detritus, root growth, and organic matter were positively correlated with site age, increasing from the 1‐yr‐old to the 3‐yr‐old site. On the 4‐yr‐old and 5‐yr‐old sites values were greater than or equal to the 2‐yr‐old site, and no indication of site deterioration was evident. Organic C significantly increased from the 1‐yr‐old to the 2‐yr‐old site, and was highest on the 5‐yr‐old site. Total N remained constant on all sites. On the three older sites detritus accumulation and root growth surpassed that of the 5‐yr‐old fertilizer‐amended site. Yield and organic matter content on the four oldest sludge sites surpassed that of the fertilizer‐amended site, and organic C and N content on all sludge sites surpassed that of the fertilizer‐amended site. As measured by these parameters, eventual soil development and ecosystem recovery appear to be accelerated on the sites reclaimed with sludge compared to the fertilizer‐amended site.
Contaminant Transport in Agroecosystems through Retention of Soil Particles on Plant Surfaces
Authors: Pinder J.E. , McLeod K.W.
Published: July 2010

The contamination of plant surfaces with soil particles is a potentially important process in the transport of insoluble contaminants such as radionuclides, heavy metals, and hydrophobic organics in agroecosystems, but few data are available to assess the significance of this mechanism for different crop species. The mass of soil particles retained on the surfaces of corn (Zea mays L.) and sunflower (Helianthus annuus L.) grown under field conditions were measured using the 238Pu content of the plants to indicate retention of soil. The crops demonstrated similar quantities and height distributions of soil retained on leaf and stem surfaces. Mean retention was 0.86 g soil retained on corn vegetation per square meter of land surface and 0.79 g m−2 retained on sunflower. Most of the soil was on the lower 1 m of the vegetation. The height distributions of retained soil can explain the larger concentrations of soil observed in the mechanically harvested grains of short stature crops such as wheat (Triticum aestivum L.) (120 mg soil per kg grain) and soybean [Glycine max (L.) Merr.] (82 mg kg−1) than that observed in taller crops such as corn (2 mg kg−1). The significance of soil retention in determining the accumulation of contaminants in grains is evaluated for several important agricultural crops.
Selenate Transport in Steady‐State, Water‐Saturated Soil Columns
Authors: Alemi M. H. , Goldhamer D. A. , Nielsen D. R.
Published: July 2010

Transport of selenate (Se6+) in steady‐state, water‐saturated soil columns was evaluated under different pore water velocities, ionic compositions, and two soil bulk densities. The soil was Panoche loam (Typic Torriorthents) saturated with 0.005 M CaSO4, 0.005 M CaCl2, or 0.05 M CaCl2. To examine the movement of selenate in soil relative to water and SO2−4 (a biogeochemically similar anion), breakthrough curves of 75SeO2−4, along witH+3H2O or 35SO2−4, were observed. Selenate appeared before elution of one pore volume and always ahead of the 3H2O and SO2−4 except in 0.05 M CaCl2, indicating exclusion of selenate by the soil matrix. On the other hand, soil analysis of selenate following the leaching indicated that selenate was retained by the soil, suggesting simultaneous exclusion and adsorption of selenate. Increasing pore water velocity and soil bulk density did not shift the position of the breakthrough curves significantly. Assuming equilibrium linear adsorption‐desorption of selenate by soil, the values of the apparent diffusion coefficient (D) and the retardation factor (R) were obtained by fitting the solution of the solute transport equation without sink and source terms to the measured breakthrough curves of selenate. The values of D showed an increasing trend with pore water velocity and the values of R were influenced by ionic composition of the soil solution.
Subsoil Thickness Effects On Yield and Soil Water When Reclaiming Sodic Minespoil
Authors: Oddie Thomas A. , Bailey Arthur W.
Published: July 2010

Minespoil sodicity has the potential to limit plant growth and impede reclamation success on surface‐mined land. A joint government/coal industry experiment was established near Highvale, AB, to determine suitable subsoil thicknesses (0, 55, 95, 135, 185, and 345 cm underlying 15 cm topsoil) for reclaiming sodic minespoil and maximizing production of an annual barley (Hordeum vulgare L.) cereal crop or a perennial alfalfa‐smooth bromegrass (Medicago sativa L., Bromus inermis Leyss.) forage mixture. Barley and forage yields were lower on the 0‐cm subsoil treatment than all other treatments. Yields for both crops increased as subsoil thickness increased to 55 cm. There was a consistent trend toward optimum yields on the 95‐cm subsoil treatment, but the difference between 55 and 95 cm was not significant. The replacement of 55 to 95 cm subsoil plus 15 cm topsoil appeared sufficient to restore post‐mine productivity to the potential achieved on surrounding agricultural land. Root depth under the forage mixture increased as total soil thickness increased, while increases under the cereal were not generally significant. The average effective root zone extended to about 85 cm under barley and 185 cm under alfalfa‐smooth bromegrass. Average seasonal soil water within the effective subsoil root zone generally increased under barley and decreased under alfalfa‐smooth bromegrass over time. Lower consumptive use of available soil water and a shallower effective root zone under barley contributed to accumulations of soil water above the subsoil/minespoil interface. Perennial forages appeared to be more effective in reducing soil water accumulations above the interface and promoting reclamation success of sodic minespoil.
Injury and Yield Response of Cotton to Chronic Doses of Ozone and Soil Moisture Deficit
Authors: Heagle Allen S. , Miller J. E. , Heck W. W. , Patterson R. P.
Published: July 2010

Plant response to ozone (O3) is known to be modified by soil moisture deficit, which occurs in varying degrees during most growing seasons. Thus, we examined the response of cotton (Gossypium hirsutum L. ‘McNair 235’) to different levels of seasonal stress by O3 when grown at two soil moisture levels. The cotton was exposed for 12 h d−1 in open‐top field chambers to five O3 doses (seasonal 12 h d−1 means from 0.020 to 0.074 µL L−1) under well‐watered (WW) conditions or under water‐stressed (WS) conditions with periodic cycles of low soil moisture. Exposures began when the fifth leaves were expanding and continued for 124 d when most leaves were chlorotic or had abscised. Ozone caused significant yield loss in WW plots but not in WS plots. Based on estimates from polynomial regression analysis, ambient O3 (seasonal 12 h d−1 mean of 0.044 µL L−1) caused a yield decrease of 19% in the WW plots compared to the O3 level in our charcoal‐filtered air plots (seasonal 12 h d−1 mean of 0.022 µL L−1). The comparable estimate for data from the WS plot was 7%, but this regression was not statistically significant. Results indicate that soil moisture deficit can decrease the impact of O3 on cotton yield.
Growth of Cotton under Chronic Ozone Stress at Two Levels of Soil Moisture
Authors: Miller Joseph E. , Patterson Robert P. , Heagle Allen S. , Pursley Walter A. , Heck Walter W.
Published: July 2010

Recent field research has shown that ambient concentrations of ozone (O3) have the potential to reduce yield of a number of economically important crop species. Soil water levels have been shown sometimes to modify the extent of the reduction. The primary emphasis of most of these studies has been on the plant component that represents economic yield. Less emphasis has been placed on characterization of the effects of O3 on growth of the total plant that ultimately determines yield. In this study, we measured season‐long growth of field‐grown cotton (Gossypium hirsutum L. ‘McNair‐235’) that was exposed to a range of O3 concentrations at two levels of soil moisture, well‐watered (WW) and water‐stressed (WS). The cotton was exposed for 12 h d−1 throughout the growing season in open‐top chambers to five O3 concentrations that ranged from 0.020 to 0.074 µL L−1 (seasonal mean 12 h d−1 concentration). Three cotton plants were sampled from each chamber at 2‐ to 3‐ wk intervals during the season, and biomass and growth measurements were made on all major plant parts. Ozone stress reduced leaf and root biomass in particular, while stem tissues were less affected. Partitioning of biomass among plant tissues was affected by O3 at certain times during the season. Leaf area duration (LAD) was reduced by O3 in both WW and WS treatments, but changes in the yield/LAD ratio and net assimilation rate indicated that reduced efficiency of leaves also was responsible for yield reductions in the WW plots. Water stress caused fewer significant effects overall than did O3, although it appeared to reduce the growth of most plant parts, especially at low O3 concentrations. There were no significant O3 × water interactions for the growth variables measured.
Migration of Technetium, Iodine, Neptunium, and Uranium in the Peat of Two Minerotrophic Mires
Authors: Sheppard Marsha I. , Thibault Denis H.
Published: July 2010

Mires may become receptors of hazardous wastes transported by the groundwater from surface or underground disposal facilities. Should the contributing water sources contain dissolved solutes, they may sorb onto the organic matter in the mire, precipitate out of solution, or form more or less mobile complexes or colloids. Our study investigated the vertical migration of Tc, I, Np, and U in two types of mires typical of the Precambrian Shield. We also report seasonal groundwater level fluctuations and chemical composition changes in the mires. Our results indicate dramatic seasonal changes in the pH and chemical composition of the groundwater, particularly the concentrations of Na, Mg, Ca, and SO4. Iodine, in spite of being sorbed to the peat with a sorption coefficient, Kd, of 0.2 to 64 L kg−1, migrated quickly through the peat in the porewater. The aeration status and the botanical origin of the peat seem to be factors in the retardation of I. Iodine accumulated on the mire surface in late summer when the water table was lower. However, Tc, U, and Np were quickly immobilized in the reducing environment of the mire and did not migrate very far from their entry point. Geometric mean Kd values for U in the three peats varied from 2600 to 19 000 L kg−1. The Kd values for U did not depend on porewater concentration, humification, or aeration. A comparison between Kd values for U obtained in situ and in laboratory studies showed that our incubation‐sorption system may be a satisfactory technique for U. Neptunium Kd values varied from 31 to 2600 L kg−1 and Tc Kd values were > 2 L kg−1 in these three peats. The Kd values are general indicators of the mobility of these elements in mires, the most mobile being I followed by Tc, Np, and U.
Availability and Form of Copper in Three Soils following Eight Annual Applications of Copper‐Enriched Swine Manure
Authors: Payne G. G. , Martens D. C. , Kornegay E. T. , Lindemann M. D.
Published: July 2010

The use of high levels of Cu in swine (Sus scrofa domesticus) production to stimulate growth and improve feed efficiency is presently being questioned due to the potential environmental hazard from repeated usage of the resulting Cu‐rich manure in agricultural land. Three field studies were established in 1978 and continued through 1985 to determine the effects of long‐term applications of Cu, as either CuSO4 or Cu‐enriched swine manure, at high rates on corn (Zea mays L.) production. The studies were conducted on Bertie fine sandy loam (Aquic Hapludults), Guernsey silt loam (Aquic Hapludalfs), and Starr‐Dyke clay loam (Fluventic Dystrochrepts‐Typic Rhodudults) in the Coastal Plain, Ridge and Valley, and Piedmont regions of Virginia, respectively. These soils have CEC ranging from 5.0 to 12.3 cmolc kg−1. According to USEPA guidelines, which are based on the CEC values and pH levels ≥6.5, the three soils have a maximum safe Cu loading rate of 280 kg Cu ha−1. After 8 yr, 890.4 t ha−1 of wet Cu‐enriched manure had been applied to these soils. The manure contained up to 1550 mg Cu kg−1 and was produced by pigs fed diets with an average of 251 mg Cu kg−1. Application of 336 kg Cu ha−1 as CuSO4, or up to 264 kg Cu ha−1 as Cu‐enriched manure, from 1978 through 1985 did not decrease corn grain yields on the three soils. The eight annual Cu applications increased Cu concentrations in ear leaf tissue by ≤2.1 mg kg−1, but did not affect the Cu concentrations in the grain. The Cu levels in all plant tissue remained within normal ranges. Diethylenetriaminepentaacetic acid (DTPA)‐extractable Cu was linearly related to the amount of Cu applied to the three soils (r = 0.93−0.98, α = 0.01) and was unrelated to Cu levels in grain or leaf tissue. Small increases, up to 1.6 mg Cu kg−1, in extractable Cu in the B horizons of the Bertie and Starr‐Dyke soils indicated little downward movement of the applied Cu. Larger increases in extractable Cu in the Guernsey subsoil were attributed to downward movement caused by plowing. Copper fractionation data indicated that a substantial portion of the applied Cu has reverted to forms not available to plants.
Effects of Sewage Sludge on Di‐(2‐Ethylhexyl) Phthalate Uptake by Plants
Authors: Aranda J. M. , O'Connor G. A. , Eiceman G. A.
Published: July 2010

Di‐(2‐ethylhexyl) phthalate (DEHP) is a priority organic pollutant frequently found in municipal sludges. A greenhouse study was conducted to determine the effects of sludge on plant uptake of 14C‐DEHP (carbonyl labeled). Plants grown included three food chain crops, lettuce (Lactuca sativa L.), carrot (Daucus carota L.), and chile pepper (Capsicum annuum L.) and tall fescue (Festuca arundinacea Schreb.) Net 14C concentration in plants grown in soil amended with 14C‐DEHP‐contaminated sludge was independent of sludge rate (at the same DEHP loading) for lettuce, chile fruit, and carrot roots. Net 14C concentration, however, was inversely related to sludge rate in carrot tops, fescue, and chile plants. Intact DEHP was not detected in plants by gas chromatography/mass spectrometry analysis. Calculated plant DEHP concentrations (based on measured net 14C concentrations and DEHP specific activities) were generally correlated better with DEHP soil solution concentrations than with total DEHP soil concentrations. Net 14C‐DEHP bioconcentration factors were calculated from initial soil DEHP concentration and plant fresh weights. Bioconcentration factors ranged from 0.01 to 0.03 for fescue, lettuce, carrots, and chile, suggesting little DEHP uptake. Additionally, because intact DEHP was not detected in any plants, DEHP uptake by plants was of minor importance and would not limit sludge additions to soils used to grow these crops.