bluuebunny/crossref_metadata_2025 huggingface dataset:
Coamendments to Modify Phosphorus Extractability and Nitrogen/Phosphorus Ratio in Feedlot Manure and Composted Manure
Authors: Dao Thanh H.
Published: July 2010

A narrow nitrogen to phosphorus ratio (N/P) exists in animal manure, resulting in P high loading and pollution risks when land applications are made to meet N demands of a crop. Nonhazardous mineral by‐products potentially widen the effective N/P ratio in manure. We determined the effects of alum, caliche, and Class C fly ash on extractable P concentrations in stockpiled and composted cattle (Bos taurus) manure at rates of 0, 0.10, 0.25, and 0.50 kg kg−1 manure. The mixtures were also added to Amarillo fine sandy loam (Aridic Paleustalf) and Pullman clay loam (Torrertic Paleustoll) at the rate of 22 Mg ha−1. Caliche, alum, and fly ash reduced water‐extractable P (WP) in stockpiled manure by 21, 60, and 85% and by 50, 83, and 93% in composted manure at the O.1kg kg−1 rate. Alum and fly ash also significantly reduced Bray‐I P (BP) concentrations by 75 and 90% in stockpiled and composted manure, respectively, and >90% at higher rates. Fly ash also decreased Mehlich III‐P (MP) concentrations, ranging from 50 to 98%. Mixing these amendments with feedlot manure widened the effective manure N/P ratio by a factor ranging from 1.5 to 18. Applying fly ash‐treated stockpiled or composted manure reduced all extractable P fractions from amended soils. Alum and caliche consistently reduced the WP fraction only. Coapplications of mineral and animal by‐products stabilized manure P where uncovered storage is unavoidable or widened its effective N/P ratio, allowing land application rates needed to fulfill plant N requirements without causing water quality impairments.
Predicting Plant Available Nitrogen in Land‐Applied Biosolids
Authors: Gilmour John T. , Skinner Vaughn
Published: July 2010

The rate at which biosolids (municipal sewage sludge) may be applied to land is dependent on factors including concentrations of metals, pathogens, toxic organic compounds, and nutrients. Where other properties are not limiting, land application rates are often based on matching crop N needs with the plant available N (PAN). The objectives of this study were to quantify biosolids PAN under field conditions and to propose methods including computer simulation to estimate biosolids PAN in a land application program. Six biosolids were evaluated over a 2‐yr period. Laboratory incubations were used to obtain decomposition kinetics. Field studies provided a relationship between inorganic fertilizer N rate and sorghum sudangrass [Sorghum bicolor (L.) Moench] tissue N concentration, which was used to determine biosolids PAN in a Captina silt loam soil (fine‐silty, siliceous, mesic Typic Fragiudult). Biosolids PAN released during the field experiment was linearly related to biosolids C/N ratio, organic N, or total N. Computer model predictions of PAN in the field were also linearly related to field estimates of biosolids PAN. Decay series (first and second year N mineralization percentages) obtained using the computer model, average biosolids decomposition kinetics, and average application site weather were very similar to decay series obtained using the computer model, actual weather, and kinetic data. Either decay series and routine analytical data for biosolids are proposed to estimate PAN for a given situation. Use of the computer model and weather data makes the approach site‐specific, while analytical data for a specific biosolids makes the approach biosolids‐specific.
Partitioning of Heavy Metals in a Soil Contaminated by Slag: A Redistribution Study
Authors: Bunzl K. , Trautmannsheimer M. , Schramel P.
Published: July 2010

In order to interpret reasonably the partitioning of heavy metals in a contaminated soil as observed from applying a sequential extraction procedure, information on possible redistribution processes of the metals during the various extraction steps is essential. For this purpose, sequential extraction (extended Tessier procedure) was used to study the chemical partitioning of Ag, Cu, Ni, Pb, and Zn in a soil contaminated either by a slag from coal firing or by a slag from pyrite roasting. Through additional application of sequential extraction to the pure slags as well as to the uncontaminated soil, it was shown that during the various extraction steps applied to the soil/slag mixtures, substantial redistribution processes of the metals between the slag‐ and soil particles can occur. In many cases, metals ions released during the extraction with acid hydroxylamine or acid hydrogen peroxide are partially readsorbed by solid constituents of the mixture and will therefore be found in the subsequent fractions extracted. As a result, one has to realize that (i) it will be difficult to predict the chemical partitioning of these metals in contaminated soils by investigating pure slags only, and (ii) information on the partitioning of a metal in a slag contaminated soil will not necessarily give any relevant information on the form of this metal in the slag or in the slag/soil mixture, because the redistribution processes during sequential extraction will not be the same as those occurring in the soil solution under natural conditions.
Characterization of Technetium Species Induced in Spinach
Authors: Harms A. V. , Krijger G. C. , van Elteren J. T. , de Goeij J. J. M.
Published: July 2010

Plants have the ability to accumulate the long‐lived fission product 99Tc. In this work, an attempt was made to separate and characterize technetium species induced by spinach plants (Spinacia oleracea L.) grown on a TcO−4 containing nutrient solution. Combination of data obtained with selective extraction (ammonium sulfate, acetone, diethyl ether, and 8‐hydroxyquinoline in chloroform) and chromatography (size‐exclusion chromatography and reversed‐phase ion‐pair chromatography) gave us insight into Tc speciation in spinach plants. The following classes of Tc species in spinach leaf homogenate were found after an incubation period of 11 d: TcO−4 (ca. 7%), TcV‐cysteine (ca. 25%), Tc bound to insoluble cell‐wall polysaccharides (ca. 17%), Tc bound to proteins (ca. 26%), and hydrophilic non‐protein Tc species (ca. 25%). These results may yield a new insight into the metabolic pathways of Tc in plants.
Chemical Composition of Leachate of Dairy Manure Mixed with Fluidized Bed Combustion Residue
Authors: Elrashidi M. A. , Baligar V. C. , Korcak R. F. , Persaud N. , Ritchey K. D.
Published: July 2010

This study was initiated to investigate the hypothesis that using Fiuidized Bed Combustion (FBC) residue to stabilize a dairy feedlot surface (DFS) could enhance element attenuation and minimize the environmental impact on water quality. The laboratory leaching experiment included FBC, dairy manure (DM), and DM/FBC treatments. The leaching process consisted of 10 weekly additions of distilled water, each of 460 mL. Using FBC with DM decreased the concentration of most elements (e.g., P, N, K, Ca, Al, Si, Fe, Mn, Cu, Zn, Pb, Cd, Co, Cr, Ni, As, and Se) in the leachate. A decrease ranging from 5.6 to 100% was obtained. The presence of high concentration of dissolved organic matter (DOM) is believed to enhance element attenuation by FBC minerals (e.g., Feo, and Al‐oxides). Several mechanisms involved in this process are proposed: (i) formation of insoluble metal‐organic complexes; (ii) sorption of soluble organic and inorganic species on mineral surfaces; and (iii) precipitation of soluble inorganic species. These mechanisms are discussed in relation to each of the measured elements. On the other hand, using FBC with DM appeared to increase the concentration of B (235%), S (47.3%), and Mg (36.5%) in the leachate. Reactions of DOM with FBC minerals to form soluble organic complexes were suggested to explain B and S increases. The increase in leached Mg could be attributed to the presence of SO2−4. Our results provide evidence that using FBC to stabilize DFS has the advantage of immobilizing a large portion of most elements present in DM leachate.
Some Equilibrium Approaches to Study the Retention and Release of Sulfate in Some Highly Acid German Subsoils
Authors: Ludwig Bernard , Khanna Partap , Prenzel Jürgen
Published: July 2010

A decrease in sulfate (SO4) deposition in recent years has been predicted to affect the long‐term changes in soil SO4 dynamics differently, depending upon the equilibrium approaches (sorption isotherms or AlOHSO4 solubility) used. This study reassesses the usefulness of equilibrium approaches using data from batch experiments where the solution concentrations were changed in small steps. Experiments were carried out using five highly acid German subsoils. The approaches included solubilities of SO4 minerals, the classical one‐ and two‐site Langmuir isotherms, an empirical Freundlich isotherm with a pH‐dependent coefficient and modified Langmuir isotherm approaches considering the activity of protons (H+‐dependent Langmuir) or the square of the proton activity ((H+)2‐dependent Langmuir) in the equations. The ion activity product of AlOHSO4 was not constant for most experiments but was a function of the SO4 sorption for all five soils. Dynamics of the retention and release of SO4 in these soils indicated the limitation in the use of one‐ and two‐site Langmuir isotherms considering the theoretical basis behind these isotherms. The (H+)2‐dependent Langmuir isotherm approach described SO4 sorption better than one‐ and two‐site Langmuir isotherms, but not as well as the pH‐dependent Freundlich and the H+‐dependent Langmuir isotherms. For describing SO4 sorption in highly acid soils it is important to include its relationship with protons. It would mean using any of the following approaches: (i) the empirical pH‐dependent Freundlich isotherm, (ii) the H+‐dependent Langmuir isotherm approach, or (iii) an ion activity product of AlOHSO4 as a function of SO4 sorption.
Nitrogen Management Impacts on Yield and Nitrate Leaching in Inbred Maize Systems
Authors: Rasse Daniel P. , Ritchie Joe T. , Peterson W. Richard , Loudon Ted L. , Martin Edward C.
Published: July 2010

Little information is available regarding N management of inbred maize (Zea mays L.), which exports less N than hybrid maize. Nitrate contamination of the groundwater has been a concern in St Joseph County in southwest Michigan where >20 000 ha of seed maize are grown on sand and sandy loam soils. Over application of N fertilizer potentially reduces profits of the local growers and poses a threat to the environment. A field experiment was conducted from 1990 to 1994 to estimate N fertilizer requirements of three different inbred varieties for maximizing yields while minimizing ground water pollution. Yield and N content of grain and stover were analyzed at the end of each growing season. Nitrate leaching was monitored throughout the 5 yr of study by collecting and analyzing drainage flows out of five large field lysimeters. Grain yield was the least responsive to N fertilization, compared with stover biomass, and grain and stover N concentrations. Analyses of yield, NO3‐N leaching and soil N balance indicated that the appropriate fertilization of the P38 mid‐season inbred approximated 108 kg N ha−1. Nitrate leaching out of unfertilized plots reached a threshold of 12 to 15 kg N ha−1 yr−1, during the last 2 yr of treatment. Application of 101 and 202 kg N ha−1 generated an average annual loss of 26 and 60 kg N ha−1, respectively, during the last 2 yr of treatment.
The Promotive Effect of Selenium on Plant Growth as Triggered by Ultraviolet Irradiation
Authors: Hartikainen Helinä , Xue Tailin
Published: July 2010

Selenium is known to be important in antioxidation in human and animals, but little attention has been paid to its role in higher plants. Chemically it is a photovoltaic element, and in order to study its effects on plants, ryegrass (Lolium perenne L.) and lettuce (Lactuca sativa L.) were cultivated in a pot experiment without or with H2SeO4 (0.1 and 1.0 mg Se kg−1) under normal light or subjected to UV(B)‐irradiation episodes. Without Se addition, UV(B) diminished markedly the yield of lettuce (by 8%) but not that of ryegrass. The lower Se dosage had no effect on yields under normal light conditions, but in combination with UV(B) it enhanced plant growth. This indicates that UV light acted as a trigger for the growth‐promoting effect of Se. The higher Se dosage was toxic to plants, but the toxicity was alleviated under UV(B). The positive interaction between the high‐energy light and Se was manifested also as increased concentrations of nucleic acids and soluble proteins. The synergistic effect was partly attributable to the antioxidative function of Se, shown as inhibition of lipid peroxidation and promotion of glutathione peroxidase (GSH‐Px) activity. Some other possible mechanisms of the positive action of Se are discussed.
Temperature and Moisture Effects on Fumigant Degradation in Soil
Authors: Gan J. , Papiernik S. K. , Yates S. R. , Jury W. A.
Published: July 2010

Recent discovery of the contribution of methyl bromide fumigation to stratospheric ozone depletion has revealed our limited understanding of the environmental processes of fumigants. For instance, little is known about fumigant degradation in soil under high temperature or low moisture conditions that prevail near the soil surface during fumigation. In this study we determined the interaction of soil temperature and moisture with degradation of 1,3‐dichloropropene (1,3‐D) and methyl isothiocyanate (MITC) for extended soil temperature and moisture ranges. Fumigant degradation increased 5 to 12 times when temperature increased from 20 to 50°C. It was further shown that chemical transformation of fumigants always increased with increasing temperature, but temperature effects on microbial degradation were fumigant dependent. The relative contribution of microbial degradation to the overall fumigant degradation was highest for the soil with highest organic matter content, and was greater for MITC than for 1,3‐D isomers. When the temperature was >30°C, microbial degradation of 1,3‐D was substantially suppressed, while that of MITC was greatly stimulated. As soil moisture content increased, 1,3‐D degradation accelerated, but that of MITC decreased. The specific responses of fumigant degradation to temperature and moisture variations should be considered when describing their transport in the environment, and also may be used for designing fumigation practices that allow reduced atmospheric emissions.
Oxyanion Sorption and Surface Anion Exchange by Surfactant‐Modified Clay Minerals
Authors: Li Zhaohui
Published: July 2010

In this study the sorption of nitrate (NO−3) and chromate (CrO2−4) from aqueous solution by surfactant‐modified clay minerals was investigated. Both the sorption and desorption of oxyanions were found to follow a Langmuir sorption isotherm. In general, the sorption affinity is higher for chromate than for nitrate, reflecting that the interaction between the divalent anions and the surfactant bilayer is stronger than that between the monovalent anions and the surfactant bilayer. Surfactant‐modified kaolinite has a higher sorption capacity for chromate. The sorption capacities for chromate and nitrate are equal for surfactant‐modified illite while the sorption capacity for nitrate is higher for surfactant‐modified smectite. Desorption by water revealed that chromate sorption was irreversible, while nitrate sorption was slightly reversible. In a mixed solution system, nitrate and chromate compete for the same sorption sites, resulting in a decrease in sorption capacity for each anion. Stoichiometric counterion desorption due to chromate and/or nitrate sorption further confirms that sorption of oxyanions by surfactant‐modified clay minerals was due to surface anion exchange. The selectivity coefficients were higher for chromate to replace bromide than for nitrate to replace bromide for surfactant‐modified kaolinite, but lower when surfactant‐modified illite and smectite were the anion exchangers. The results indicate that surfactant‐modified clay minerals are effective sorbents to remove anionic contaminants from water. However, the types of clay minerals should be correctly selected to maximize the contaminant removal efficiency.
Nitrite and the Two Stages of Nitrification in Nitrogen Polluted Onondaga Lake, New York
Authors: Gelda Rakesh K. , Effler Steven W. , Brooks Carol M.
Published: July 2010

Nitrite (NO−2) concentrations in the upper waters of N polluted Onondaga Lake, New York, are documented for the April through October interval for a 10‐yr (1989–1998) period. Inputs of NO−2 from a domestic waste treatment facility (METRO) and tributaries (4) to the lake are quantified for four of the years (1991–1994). The NO−2 concentrations measured in Onondaga Lake (e.g., annual maxima in the range 200–1000 mg N m 3) are some of the highest reported for lakes and rivers in the literature. These levels represent severe violations of toxicity standards. Annual average concentrations in the METRO effluent ranged from 412 to 1097 mg N m−3. The METRO load represented >90% of the total external NO−2 load to the lake. A mechanistic mass balance model for NO−2 and NO−3 is developed and applied for the lake to identify occurrences, and quantify the rates, of the first and second stages of nitrification. Nitrite is found to behave in a nearly conservative manner in the upper waters of the lake over the April to July interval. The progressive increases in concentrations over this interval have been largely in response to inputs from METRO. Major deviations from conservative behavior occurred for NO−2 in most years over the July to October interval as a result of the irregular operation of the two stages of the nitrification process. This has been manifested as large and abrupt changes in NO−2 concentration in the July to October interval. Potential factors responsible for the observed dynamics in nitrification and the NO−2 pool are considered.
Plant Community Responses to Disturbance by Mechanized Military Maneuvers
Authors: Milchunas Daniel G. , Schulz Keith A. , Shaw Robert B.
Published: July 2010

The effects of 10 yr of military training exercises on vegetation structure were assessed across plant communities that differed in physiognomy and soil texture at Pinon Canyon Maneuver Site (PCMS), Colorado, after release from previous grazing management. Covariate analyses aided in separating temporal trends due to both release from grazing and imposition of training disturbance from the direct effect of training. The shift in land use had both synergistic and antagonistic impacts on successional trajectories of communities, and on horizontal and vertical structural heterogeneity. Vegetation basal cover declined with increasing intensity of disturbance by tracked vehicles, but release from grazing acts additively in this ecosystem. Litter cover increased following release from grazing, even though it declined with increasing levels of disturbance. Vehicular maneuvering generally reduced woody life forms in tail‐height classes to a greater extent than short‐height classes. Low growing cacti were susceptible to crushing. Species and functional group responses to vehicular disturbance were sometimes dependent on community type. Long‐lived perennials declined, but were replaced by short‐lived perennials in only the shrub‐grassland community. Annuals and exotics did not show relationships with intensity of disturbance, though some weed species increased. Community‐wide species dissimilarity did not show large shifts, and patterns in species diversity or richness were not related to intensity of disturbance. The PCMS appears to be in a transient stage where release from grazing has had as much or more impacts as did the imposition of military training. Fine textured soils may be more susceptible to the cumulative effects of vehicular loads.
Physiological Effects of the Mexico City Atmosphere on Lichen Transplants on Oaks
Authors: Zambrano A. , Nash T. H. , Gries C.
Published: July 2010

Two lichen species, Usnea ceratina Ach. and Everniastrum neocirrhatum (Hale M. Wirth) Hale ex Sipman, were transplanted for 54 d into an oak forest (Quercus rugosa) in the vicinity of Mexico City to assess their ability to survive near a highly polluted urban environment. Net photosynthesis based on dry weight and chlorophyll b decreased respectively ca. 30 and 25% compared with control samples in a less polluted site, ca. 100 km north of Mexico City. There was no interspecific difference in the response of carbon fixation, but E. neocirrhatum was more sensitive to chlorophyll b degradation near Mexico City than U. ceratina. Chlorophyll a was also degradated (ca. 15%) near Mexico City. Changes in total carotenes were mostly dependent on species and time rather than on location. High concurrent levels of ozone and sulfur dioxide in the air are discussed as possible causes of the decline in the lichen photosynthesis and chlorophyll content.
Radiological Impact of Phosphogypsum Applied to Soils under Bahiagrass Pasture
Authors: Alcordo I. S. , Rechcigl J. E. , Roessler C. E. , Littell R. C.
Published: July 2010

Phosphogypsum (PG), a by‐product in the manufacture of phosphoric acid, is primarily gypsum. The USEPA regulates the removal of PG from stacks because it contains 226Ra. Measures to quantify the transfer of radioactivity in PG to the agricultural environment are needed. The objective of the study was to collect data needed for assessment of the radiological impacts of PG applied to two Florida soils. Field experiments using 0, 10, and 20 Mg PG ha−1 were conducted for 2 yr at the University of Florida RCREC, Ona, FL. PG‐attributable levels of 226Ra, 210Pb, and 210Po were observed in the top 5‐cm layer of the soils. Surface 222Rn flux increased by 0.067 to 0.078 mBq m−2 s 1 per Mg PG ha−1. Radionuclide concentrations in regrowth forages increased at one site where the first post‐treatment rainfall did not occur until 20 d after PG application. In mature forages, radionuclide levels generally increased with PG in both soils. No effects on radionuclide levels in subsurface water down to 90 cm and only slight effects on gamma radiation and on airborne 222Rn measured 1 m from the ground were noted. The linear regression slope for a radiological parameter normalized with respect to the pertinent radionuclide applied per m2 per Mg PG ha−1 is proposed as the transfer factor (TF) of that radionuclide in PG to the agricultural medium in terms of that parameter. The TF permits the calculation of the potential effect on certain radiological parameters of PCs containing different radionuclide concentrations from the one used in this study.
Long‐Term Monitoring of Soil Gas Fluxes with Closed Chambers Using Automated and Manual Systems
Authors: Scott Albert , Crichton Ian , Ball Bruce C.
Published: July 2010

We describe two gas sample collection techniques, each of which is used in conjunction with custom made automated or manually operated dosed chambers. The automated system allows automatic collection of gas samples for simultaneous analysis of multiple trace gas efflux from soils, permitting long‐term monitoring. Since the manual system is cheaper to produce, it can be replicated more than the automated and used to estimate spatial variability of soil fluxes. The automated chamber covers a soil area of 0.5 m2 and has a motor driven lid that remains operational throughout a range of weather conditions. Both systems use gas‐tight containers of robust metal construction, which give good sample retention, thereby allowing longterm storage and convenience of transport from remote locations. The containers in the automated system are filled by pumping gas from the closed chamber via a multiway rotary valve. Stored samples from both systems are analysed simultaneously for N2O and CO2 using automated injection into laboratory‐based gas chromatographs. The use of both collection systems is illustrated by results from a field experiment on sewage sludge disposal to land where N2O fluxes were high. The automated gas sampling system permitted quantification of the marked temporal variability of concurrent N2O and CO2 fluxes and allowed improved estimation of cumulative fluxes. The automated measurement approach yielded higher estimates of cumulative flux because integration of manual point‐in‐time observations missed a number of transient high‐flux events.
The Influence of Nitrilotriacetate on Heavy Metal Uptake of Lettuce and Ryegrass
Authors: Kulli B. , Balmer M. , Krebs R. , Lothenbach B. , Geiger G. , Schulin R.
Published: July 2010

Metal uptake and removal from the soil by plants may be a useful measure to remediate contaminated soils. These processes can be enhanced by adding metal chelators to soil. We investigated the effect of nitrilotriacetate (NTA) and urea on the uptake of Cd, Cu, and Zn by lettuce (Lactuca sativa L. cv. Orion) and Italian ryegrass (Lolium perenne L. cv. Bastion) in pot experiments. Nitric acid‐extractable heavy metal concentrations in the contaminated soil were 2 mg Cd, 530 mg Cu, and 700 mg Zn kg−1. Three NTA treatments (0.5, 1.8, and 5.3 mol m−2) were compared with two urea treatments (0.25 and 0.9 mol m−2), and a control. Nitrilotriacetate and urea increased the NaNO3‐extractable soil concentrations of the three metals. At the highest NTA dose, metal concentrations in the aboveground plant biomass was 4 to 24 times greater than in the control plants. While NTA increased plant metal concentrations, it reduced plant matter production. At lower doses, this effect was small. At the highest NTA dose, plant growth was almost completely inhibited. Severe visual symptoms indicated metal toxicity as the likely cause. The urea treatments generally increased the plant matter production. Total metal uptake was in general larger at the lowest or at the intermediate NTA dose than at the highest doses. Little additional total metal uptake was achieved with NTA treatments than with urea. Compared with the controls, neither NTA nor urea enhanced total uptake under the given conditions by more than threefold.
Efficiency of Hexane Extraction of Napropamide from Aldrich Humic Acid and Soil Solutions
Authors: Williams C. F. , Letey J. , Farmer W. J. , Nelson S. D. , Anderson M. , Ben‐Hur M.
Published: July 2010

Dissolved organic matter (DOM) has been shown to form a stable complex with Napropamide [2(α‐naphthoxy)‐N,N‐diethyl propionamide] and to facilitate its transport through soil columns. Liquid‐liquid extraction of organics is a common method to transfer napropamide from water into an organic phase for gas chromatography analysis. A study was conducted to determine the effect of Aldrich humic acid, soil‐derived dissolved organic matter, electrical conductivity, and hydrogen ion activity on the ability of hexane to extract napropamide from solutions and from soil extracts. The electrical conductivity of Aldrich humic acid solutions (0.0, 48, and 100 mg C L−1) were adjusted to 0.01, 0.97, and 1.69 dS m−1 by adding NaCl and CaCl2, and pH (8.2, 7.4, and 5.6) was adjusted using HCl and NaOH. Electrical conductivity had no effect on extraction efficiency. In the absence of DOM pH had no effect on extraction efficiency. Extraction efficiency decreased with increasing DOM concentration. Maximum reduction in extraction efficiency occurred in the presence of DOM when solution pH was near neutrality. A maximum extraction efficiency of 100% was observed in the absence of DOM and a minimum of 68% when napropamide was added to DOM solutions at pH 8.2 and then lowered to pH 5.6. Management practices such as liming and allowing napropamide to dry on the soil may increase environmental transport. Also quantification of napropamide in environmental samples can be affected by DOM.
Design and Characterization of a New Dialysis Chamber for Investigating Dissolved Organic Matter‐Organic Complexes
Authors: Williams C. F. , Farmer W. J. , Letey J. , Nelson S. D.
Published: July 2010

Equilibrium dialysis is commonly used to measure the complex formed between dissolved organic matter (DOM) and pesticides such as napropamide [2(α‐naphthoxy)‐N,N‐diethyl propionamide]. Currently the dialysis method most often used employs dialysis tubing that is clamped on both ends. Limitations of the dialysis tubing method include difficulty in sample addition to the dialysis tubing, dilution effects, and the need for large sample volumes. A new dialysis chamber constructed of Teflon and using flat dialysis membranes is described and characterized using napropamide as a model compound. Using a dialysis membrane with a molecular weight cut off of 500 Daltons the system reached equilibrium across the membrane within 120 h. Significant sorption of napropamide to the membrane was observed. Napropamide sorption was linear, reversible, and dependant on the membrane used. Sample addition and removal from the chamber is possible without destroying the integrity of the membrane. The dialysis chamber allowed for fast and easy quantitative addition and removal of sample for dialysis without wasting sample. The small chamber made possible dialysis of very small samples (as little as 1.5 ml.) while maintaining a large surface area for diffusion. The chamber also provided dialysis with a maximum dilution factor of two since the volume of dialysate needed is equal to the volume of sample introduced.
Fate of Soil Applied Herbicides: Experimental Data and Prediction of Dissipation Kinetics
Authors: Baer U. , Calvet R.
Published: July 2010

Dissipation kinetics of several soil‐applied herbicides [atrazine (6‐chloro‐2 ethylamino‐4 isopropyl‐1,3,5‐triazine‐2,4 diamine), simazine (6‐chloro‐2,4‐diethyl‐1,3,5‐triazine‐2,4‐diamine), diuron (3‐(3,4‐dichloro‐phenyl)‐1,1‐dimethylurea), and sulcotrione (2‐(2‐chloro‐4‐mesyl‐benzoyl)cyclohexane‐1,3‐dione)] are studied at three sites having different climatic, pedological, and agronomical characteristics. Field data were obtained during 2 yr, 1993 and 1994. Information was completed by laboratory measurements of adsorption, desorption, and disappearance kinetics obtained at two temperatures (15 and 28°C) and two soil water contents (50 and 90% soil water capacity). Adsorption and desorption conform to the Freundlich description, sulcotrione being the less adsorbed. Laboratory disappearance kinetics can be approximately described with a first‐order law under some conditions. Calculated laboratory disappearance rate coefficients are used to simulate field dissipation kinetics in the 0‐ to 10‐cm soil layer, taking into account the effects of soil temperature (Arrhenius formula) and water content (Walker relation). Observed field dissipation kinetics, which are not fully described by a first‐order law, can be approximately simulated. Results are discussed from the points of view of agronomy and environment.
Multi‐Residue Analysis of Corn and Soybean Pesticides in Brazilian Oxisols Using Gas Chromatography and Mass Selective Detection
Authors: Laabs V. , Amelung W. , Zech W.
Published: July 2010

Available methods for measuring pesticide residues in soils usually have not been tested for tropical soils nor do they cope with the spectrum of pesticides used in the tropics. An accurate and efficient method for the simultaneous determination of 14 corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] pesticides in Oxisols is presented in this study. The quantification of the pesticides was achieved using gas chromatography coupled with mass selective detection. For the extraction of aged pesticide residues from soil samples, combinations of acetone, ethylacetate, hexane, methanol, water, and salt solutions were tested. Of the 20 different solvent systems evaluated, the mixture of acetone‐ethylacetate‐water 2:2:1 (v/v/v) was most efficient for the extraction of all pesticides except metribuzine [4‐amino‐6‐ (1,1‐dimethylethyl)‐3‐(methylthio)‐1,2,3‐ triazine‐5(4H)‐one]; this herbicide was recovered best by ethylacetate‐water4:1 (v/v). Different sample aging‐times (5–30d) did not affect the recovery of pesticides from incubated samples. Extraction of pesticides from field‐soil samples also was best with acetone‐ethylacetate‐water. No differences in extraction efficiency were observed between a simple shake extraction (4h) and batch extractions with an additional rise in temperature (60°C) or a sonication (30 min). The elimination of the water from the soil extract was achieved by a liquid‐liquid extraction with dichloromethane, which recovered the whole polarity spectrum of pesticides quantitatively. The method recovery from soil samples of freshly spiked pesticides averaged 94.8 ± 2.4%. The method was validated for Oxisols of contrasting clay and organic C content.
Field‐Scale Study of Chlortoluron Movement in a Sandy Soil over Winter: II. Modeling
Authors: Streck Thilo , Richter Jörg
Published: July 2010

This study was conducted to evaluate different modeling approaches for their ability to predict chlortoluron movement observed in a 4‐mo field study. The data base includes the results of a Br− transport experiment performed at the same site and of laboratory sorption‐desorption (SD) experiments. The approaches tested are based on the one‐dimensional convection dispersion equation (CDE) with two‐stage or equilibrium sorption. The CDE was applied either at the field scale or, to account for parameter variability, within a parallel soil columns (PSC) approach. Parallel soil column simulations were realized by the Monte Carlo (MC) method. Transport and sorption parameters and their distributions were estimated from Br− concentration profiles and SD isotherms, respectively. Chlortoluron degradation had been investigated in a joint project. The CDE with two‐stage sorption represented the movement of the chlortoluron peak well, but not its spreading. Similar results were obtained assuming equilibrium sorption, provided the same sorption parameters were used. If the sorption parameters were derived from the 1‐d sorption isotherm instead, displacement was overpredicted. Accounting for the variability of sorption and transport parameters through the PSC approach affected the simulation results only slightly. All simulations substantially underpredicted chlortoluron spreading, probably because the time scales of the laboratory and the field experiments were too different. To convert the estimated rate parameter to the appropriate time scale, we derived a simple formula that is based on the hypothesis of intrasorbent diffusion. Application of the CDE with the rescaled rate parameter distinctly improved the agreement between modeled and measured chlortoluron concentration profiles.
Stocking Method Effects on Nutrient Runoff from Pastures Fertilized with Broiler Litter
Authors: Kuykendall H. A. , Cabrera M. L. , Hoveland C. S. , McCann M. A. , West L. T.
Published: July 2010

Repeated applications of broadcast broiler (Gallus gallus domesticus) litter can increase nutrient runoff from pastures. Rotational stocking (RS) of cattle, as compared with continuous stocking (CS), may be useful in decreasing surface nutrient runoff because of better manure distribution and more uniform forage accumulation to act as filters and trap nutrients. Our objective was to measure nutrient runoff from six 0.75‐ha tall fescue (Festuca arundinacea Schreb.)—common bermudagrass [Cynodon dactylon (L.) Pers.] pastures fertilized with 13 to 15 Mg (dry weight) broiler litter per hectare per year and managed under RS or CS. Two cross‐bred beef (Bos taurus) steers were maintained on each pasture year around for 2 yr, with additional steers added to maintain similar forage availability between stocking methods. In each pasture, surface runoff was directed to a flume where it was sampled by an automatic sampler. Runoff was analyzed for total Kjeldahl N, (NO−3 + NO−2)−N, NH+4‐N, total Kjeldahl P, and dissolved reactive P (DRP). Grazing method had no effect (P > 0.10) on surface runoff quality or quantity. Average runoff expressed as a percentage of the rain was 15% for the first year and 12% for the second year. The average flow‐weighted concentrations of DRP and NH+4‐N were 5.08 mg P L−1 and 1.07 mg N L−1 for the first year, and 8.22 mg P L−1 and 10.11 mg N L−1 for the second year (P < 0.10).
Precipitation Effects on Sediment and Associated Nutrient Discharges from Rhode River Watersheds
Authors: Correll David L. , Jordan Thomas E. , Weller Donald E.
Published: July 2010

Total suspended sediment (TSS) concentrations and their nutrient composition were studied in discharges from seven contiguous small watersheds on the Atlantic Coastal Plain in Maryland for up to 22 yr. All watersheds were equipped with V‐notch weirs and volume‐integrating, flow‐proportional samplers. Spot samples were also taken for analysis of TSS concentrations and the composition of dissolved and particulate nutrients at known water discharge rates. Interannual variations in annual and seasonal precipitation during this study spanned approximately the range of 160‐yr weather records in the vicinity. Mean annual TSS fluxes were 263, 546, 134, and 92 kg ha−1 for the area‐weighted mean of the overall Rhode River watershed, and for subwatersheds that were primarily‐cropland, completely forested, and grazed, respectively. TSS fluxes were highest in the summer, followed by spring, winter, and fall. Regressions of TSS flux vs precipitation were used to calculate TSS fluxes for seasons and years with average, above and below the average precipitation. TSS flux from the Rhode River watershed was 12‐fold higher in very wet years than in very dry years and 271‐fold higher in very wet summers than in very dry summers. At base flow, TSS had high nutrient content, but as flow rates increased TSS nutrient content rapidly declined. At base flow, most of the total‐P, TPi, TKN, and organic‐C was in the dissolved phase, while at higher flows, most of these nutrients were in the TSS phase.
Responses of Boreal Plants to High Salinity Oil Sands Tailings Water
Authors: Renault S. , Paton E. , Nilsson G. , Zwiazek J. J. , MacKinnon M. D.
Published: July 2010

In the extraction of bitumen from oil sands ore, large volumes of railings water (CT water) containing elevated levels of Na, sulfate, bicarbonate and chloride are produced. High salinity process waters will probably affect terrestrial reclamation options. The present study tested the impact of tailings waters on boreal forest species including aspen (Populus tremuloides Michx.), buffalo berry [Sheperdia canadensis (L.) Nutt], northwest hybrid poplar (Populus deltoides × Populus balsamifera), dogwood (Cornus stolonifera Michx.), jack pine (Pinus banksiana Lamb.), and white spruce [Picea glauca (Moench) Voss]. Seedlings were grown in solution culture containing mineral nutrients and different dilutions of CT water, with and without supplemental salts (Na2SO4 and NaCl). After 4 wk of treatment, dogwood, hybrid poplar, and buffalo berry showed relatively high resistance to saline CT waters. Conifer seedlings developed leaf necrosis in all treatments, while aspen seedlings rapidly lost their foliage and produced new leaves. In comparison to the controls, elevated Na levels were measured in plant tissue of all species grown in CT water. However, some differences between species were observed, with jack pine seedlings showing much higher Na content than aspen, dogwood, or hybrid poplar. In hybrid poplar, the accumulation of Na was accompanied by a significant reduction in K, Mg, Ca, and P. Buffalo berry, aspen, jack pine, and white spruce showed elevated levels of S after growth in the sulfate‐enriched CT waters. High tissue Na content did not induce leaf injury in dogwood, hybrid poplar and buffalo berry, suggesting possible Na resistance.
Comparison of Simulated Forest Responses to Biosolids Applications
Authors: Luxmoore R. J. , Tharp M. L. , Efroymson R. A.
Published: July 2010

Organic matter and N are added to humus pools of the LINKAGES simulator of forest growth and N cycling at a range of application rates to investigate long‐term effects of biosolids (sewage sludge) on forest productivity. Two conifer plantations (Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco var. menziesii], loblolly pine [Pinus taeda L.]) and a northern hardwood forest located in contrasting climatic regions are investigated. Single applications of biosolids are given at 0, 5, 10, 20, and 40 Mg/ha, and multiple applications are given on seven occasions at 3‐yr intervals at rates of 5 and 10 Mg/ha. Highly significant increases in aboveground phytomass and net primary productivity of Douglas‐fir plantations are obtained in a 100‐yr simulation with increasing biosolids application rates. Results for loblolly pine from a 50‐yr simulation produced about half the growth response of Douglas‐fir. Long‐term simulations of northern hardwoods showed modest growth responses and small increases in NPP with added biosolids.. The phytomass of one overstory and three understory species in the hardwood forest changed in response to different biosolids applications and varying species sensitivity to N supply. Biosolids are a significant resource for enhancing forest productivity, particularly in conifer plantations. Estimates of N leaching losses from simulated forest sites combined with a literature review of leaching losses suggest that biosolids applications at 3‐yr intervals with rates less than 8.5 Mg/ha (0.4 Mg N/ha) during active forest growth may pose little offsite contamination risk to ground water or surface waters.
Estimation of Nitrate Contamination of an Agro‐Ecosystem Outwash Aquifer Using a Nitrogen Mass‐Balance Budget
Authors: Puckett Larry J. , Cowdery Timothy K. , Lorenz David L. , Stoner Jeffrey D.
Published: July 2010

A mass‐balance budget of N cycling was developed for an intensive agricultural area in west‐central Minnesota to better understand NO−3 contamination of ground water in the Otter Tail outwash aquifer. Fertilizer, biological fixation, atmospheric deposition, and animal feed were the N sources, and crop harvests, animal product exports, volatilization from fertilizer and manure, and denitrification were the N sinks in the model. Excess N, calculated as the difference between the sources and sinks, was assumed to leach to ground water as NO−3. The budget was developed using ground water data collected throughout the 212‐km2 study area. Denitrification was estimated by adjusting its value so the predicted and measured concentrations of NO3 in ground water agreed. Although biological fixation was the largest single N source, most was removed when crops were harvested, indicating that inorganic fertilizer was the primary source of N reaching the water table. It was estimated that denitrification removed almost half of the excess NO−3 that leached below the root zone. Even after accounting for denitrification losses, however, it was concluded that the ground water system was receiving approximately three times as much N as would be expected under background conditions.
Development of Pedotransfer Functions to Quantify Phosphorus Saturation of Agricultural Soils
Authors: Kleinman Peter J. A. , Bryant R. B. , Reid W. S.
Published: July 2010

Soil P saturation affects the risk of P loss to surface and ground water and is therefore a critical environmental indicator in regions where eutrophication is a concern. In the USA, most soil testing laboratories do not include environmental indicators such as soil P saturation as standard soil test options. Development of pedotransfer functions that relate soil test data to soil P saturation, however, would enable soil testing laboratories to estimate soil P saturation as part of soil test results without significant additional expenditures. This study examines associations between readily‐available soil test data (pH, soil organic matter, and extractable P, Al, Fe, and Ca) and soil P saturation as estimated by acid ammonium oxalate extraction. Fifty‐nine soil samples were collected from the Delaware River Watershed in New York State (42°21′N, 74°52′W) and subjected to standard soil test analyses as well as to acid ammonium oxalate extraction. Some soil test variables were well correlated with soil P saturation. As a single predictor, soil test P was most highly correlated to soil P saturation (r = 0.88). This association supports the use of soil test P as an environmental indicator. Soil test Al also was well correlated with soil P saturation following logarithmic transformation (r = 0.73). Multivariate pedotransfer functions containing soil test P, Al, Fe, soil organic matter, and pH did not significantly improve estimation of soil P saturation (R = 0.91) above soil test P alone.
Prospects for Minimizing Phosphorus Excretion in Ruminants by Dietary Manipulation
Authors: Valk H. , Metcalf J. A. , Withers P. J. A.
Published: July 2010

In most intensive dairy farms, P input exceeds output, causing potential P losses to the environment, which results in leaching to ground water and eutrophication. Phosphorus in fertilizer and purchased feeds are the main contributors to P input, whereas milk P is the main output. In the Netherlands, new legislation has been introduced to substantially reduce P surpluses. However, since P is essential for maintenance and milk production, the dietary P supply must be maintained, especially for high‐yielding dairy cows. This paper reviews how dairy cow diets can be manipulated to reduce potential P‐loss to the environment without negative effects on animal health, feed intake, or milk production. The availability of P in forages, purchased feed, and inorganic phosphate supplements for ruminants may differ substantially and more research work is needed to elucidate the relevant factors influencing feed P availability. There is a lack of understanding of how and to what extent P is absorbed from the small intestine and the relationship to hydrolysis and microbial P utilization in the rumen. Comparing national P requirement systems indicates that the systems used in the UK and Italy should be revised to minimize unnecessary P accumulation in the soil. In addition, the impact of manipulating the dietary P supply to decrease P losses from dairy farming systems is evaluated. Whole farm system studies have illustrated the potential environmental benefits of more closely monitoring imports of purchased feeds onto the farm.
A Review of New Zealand Research Measuring Phosphorus in Runoff from Pasture
Authors: Gillingham Allan G. , Thorrold Bruce S.
Published: July 2010

New Zealand pastoral farm land is intensively grazed and receives predominantly single superphosphate fertilizer. Resource managers and policymakers are concerned about the effects of such land use on P enrichment of waterways and lakes. This paper reviews New Zealand research on the effects of agricultural land use on P losses in water runoff and highlights priorities for management and future research. Diffuse agricultural sources contribute about 91% of total P entering fresh waters annually, with 0.11 to 1.67 kg P ha−1 yr−1 being removed, mostly in particulate forms. Despite a number of studies showing good site‐specific correlation, no widely applicable soil test method for estimating runoff dissolved P concentration has been found. The effects of (i) fertilizer application in increasing surface runoff P concentrations (ii) riparian areas in both source and control roles, and (iii) subsurface drainage, in reducing losses of P in surface runoff from pasture land, are reported. A catchment scale simulation model, Basin New Zealand (BNZ), for intensively grazed pastures, has been produced based on CREAMS (chemicals, runoff, and erosion from agricultural management systems). This model adequately predicts P loss at the field scale but is less reliable at the catchment scale, which indicates differences in predominant P and sediment sources at the two scales. Corrective management has alleviated eutrophication problems in some lakes and waterways; however better information is yet required to understand, model, and manage the more insidious losses of P to waterways from New Zealand farm land.