bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Surface Water Critical Loads with PROFILE
Authors: Rapp L. , Bishop K. 
Published: June 2010

ABSTRACTThe critical load concept has become a valuable tool for policymakers in the European negotiations on emission reductions. Despite the international acceptance, ongoing validation of critical load methodology is of the utmost importance to avoid a situation where the calculation results are difficult to defend. In this paper we explore the potential of using the steady state soil chemistry model PROFILE as an alternative to the Steady State Water Chemistry (SSWC) method for calculating critical loads of acidity. The hypothesis is that the uncertainty in prediction of preindustrial leaching of base cations is reduced when soil properties instead of lake chemistry are used as input data. Paleolimnological reconstructions of preindustrial lake chemistry are used to test PROFILE. As PROFILE requires soil data that are not generally available on a catchment level, we used distributions of crucial parameters from soil survey data within the vicinity of five lakes for which paleoecological pH reconstructions were available. An important concern is the characterization of catchment hydrology. A calibration of the “effective” soil depth, needed to give PROFILE predictions that coincided with paleolimnology, suggested that approximately 0.6 m of the total soil depth was hydrologically active in supplying acid neutralizing capacity (ANC) to runoff through weathering. At present, there is insufficient evidence to either recommend or reject the PROFILE model for surface water critical loads. Before such a judgement can be made, the approach presented here has to be tested for other regions, and the definition of catchment hydrology needs to be investigated further.
Solute Movement through an Allophanic Soil
Authors: Magesan G. N. , Vogeler I. , Clothier B. E. , Green S. R. , Lee R. 
Published: June 2010

ABSTRACTAllophanic soils are widespread around the world, but little research has been done on their transport properties. This study reveals the effect of two soil water potential heads and two water‐flow regimes of continuous and intermittent flow on solute transport through undisturbed soil columns of Horotiu silt loam (Typic Hapludand), an allophanic soil. Two different methods—breakthrough curves (BTCs) and time domain reflectometry (TDR)—were employed to determine the extent of preferential solute transport in the topsoil. The TDR data were also used to look at the depth dependence of the transport properties. The convection–dispersion equation (CDE) with the appropriate boundary conditions adequately described the movement of both Br and Cl under the various flow conditions. Although no preferential flow was found under the imposed unsaturated flow conditions, the flow of water and transport of solute became more uniform with depth. The results show that both Br and Cl are retarded in this allophanic soil. Retardation values range from 1.5 to 1.9, and, as the TDR data showed, increase from the depth of 5.0 to 10.0 cm. Intermittent leaching results showed that there was no effect on solute concentrations in the leachate following no‐flow periods. This suggests that water and solute transport in this soil were either relatively uniform or that transverse mixing during flow was already fast enough to eliminate concentration gradients between regions of different “mobility.”
Impact of Genetically Modified Crops and Their Management on Soil Microbially Mediated Plant Nutrient Transformations
Authors: Motavalli P. P. , Kremer R. J. , Fang M. , Means N. E. 
Published: June 2010

ABSTRACTOne of the potential environmental effects of the recent rapid increase in the global agricultural area cultivated with transgenic crops is a change in soil microbially mediated processes and functions. Among the many essential functions of soil biota are soil organic matter decomposition, nutrient mineralization and immobilization, oxidation–reduction reactions, biological N fixation, and solubilization. However, relatively little research has examined the direct and indirect effects of transgenic crops and their management on microbially mediated nutrient transformations in soils. The objectives of this paper are to review the available literature related to the environmental effects of transgenic crops and their management on soil microbially mediated nutrient transformations, and to consider soil properties and climatic factors that may affect the impact of transgenic crops on these processes. Targeted genetic traits for improved plant nutrition include greater plant tolerance to low Fe availability in alkaline soils, enhanced acquisition of soil inorganic and organic P, and increased assimilation of soil N. Among the potential direct effects of transgenic crops and their management are changes in soil microbial activity due to differences in the amount and composition of root exudates, changes in microbial functions resulting from gene transfer from the transgenic crop, and alteration in microbial populations because of the effects of management practices for transgenic crops, such as pesticide applications, tillage, and application of inorganic and organic fertilizer sources. Possible indirect effects of transgenic crops, including changes in the fate of transgenic crop residues and alterations in land use and rates of soil erosion, deserve further study. Despite widespread public concern, no conclusive evidence has yet been presented that currently released transgenic crops, including both herbicide and pest resistant crops, are causing significant direct effects on stimulating or suppressing soil nutrient transformations in field environments. Further consideration of the effects of a wide range of soil properties, including the amount of clay and its mineralogy, pH, soil structure, and soil organic matter, and variations in climatic conditions, under which transgenic crops may be grown, is needed in evaluating the impact of transgenic crops on soil nutrient transformations. Future environmental evaluation of the impact of the diverse transgenic crops under development could lead to an improved understanding of soil biological functions and processes.
Impact of Glyphosate on the Bradyrhizobium japonicum Symbiosis with Glyphosate‐Resistant Transgenic Soybean: A Minireview
Authors: Zablotowicz Robert M. , Reddy Krishna N. 
Published: June 2010

ABSTRACTGlyphosate‐resistant (GR) soybean [Glycine max (L.) Merr.] expressing an insensitive 5‐enolpyruvylshikimic acid‐3‐phosphate synthase (EPSPS) gene has revolutionized weed control in soybean production. The soybean nitrogen fixing symbiont, Bradyrhizobium japonicum, possesses a glyphosate‐sensitive enzyme and upon exposure to glyphosate accumulates shikimic acid and hydroxybenzoic acids such as protocatechuic acid (PCA), accompanied with B. japonicum growth inhibition and death at high concentrations. In a series of greenhouse and field experiments, glyphosate inhibited nodulation and nodule leghemoglobin content of GR soybean. Glyphosate accumulated in nodules of field‐grown GR soybean, but its effect on nitrogenase activity of GR soybean was inconsistent in field studies. In greenhouse studies, nitrogenase activity of GR soybean following glyphosate application was transiently inhibited especially in early growth stages, with the greatest inhibition occurring under moisture stress. Studies using bacteroid preparations showed that the level of glyphosate inhibition of bacteroid nitrogenase activity was related to in vitro glyphosate sensitivity of the B. japonicum strains. These studies indicate the potential for reduced nitrogen fixation in the GR soybean system; however, yield reductions due to this reduced N2 fixation in early stages of growth have not been demonstrated.
Reduced Biodegradation of Benzonitrile in Soil Containing Wheat‐Residue‐Derived Ash
Authors: Zhang Ping , Sheng Guangyao , Wolf Duane C. , Feng Yucheng 
Published: June 2010

ABSTRACTBurning of crop residues is a common agricultural practice that incorporates the resulting particulate matter (ash) of high adsorptivity into soils. To investigate the effect of ash on the biodegradation of pesticides in soils, we measured the sorption, desorption, and biodegradation of benzonitrile in a silt loam in the presence and absence of an ash resulting from burning of wheat (Triticum aestivum L.) residue. Biodegradation experiments were conducted by inoculating sorbent slurries with a pure culture of benzonitrile‐degrading bacteria (Nocardia sp.). Both liquid‐ and sorbed‐phase benzonitrile concentrations were quantified over time. The ash was approximately 2000 times more effective per unit mass than the soil in sorbing benzonitrile. Amendment of the soil with 1% ash (by weight) resulted in a 10‐fold increase in sorption. Sorption of benzonitrile by the ash significantly decreased the solution‐phase concentration in the slurries of ash and ash‐amended soil. Desorption of benzonitrile from the ash required approximately 60 min to complete, whereas approximately 20 min were required for desorption from the soil. Benzonitrile in the extracts of various sorbents and soil slurry was completely degraded within 500 min. However, the degradation was substantially reduced in the presence of the ash. At 2000 min, only 20% of benzonitrile in ash slurry and only 44% in ash‐amended soil slurry were degraded. An acclimation period of approximately 100 min was observed in extracts and slurries containing the ash. Substantial reduction in the biodegradation of benzonitrile in the presence of wheat ash was apparently due to sorption of benzonitrile by the ash, slow desorption from the ash, and the increased acclimation period. Our results suggest that the presence of crop‐residue‐derived ash may increase the persistence of pesticides in agricultural soils.
Stream Nitrate Variations Explained by Ground Water Head Fluctuations in a Pyrite‐Bearing Aquifer
Authors: Grimaldi C. , Viaud V. , Massa F. , Carteaux L. , Derosch S. , Regeard A. , Fauvel Y. , Gilliet N. , Rouault F. 
Published: June 2010

ABSTRACTIn the context of agricultural nitrogen excesses in northwestern France, pyrite‐bearing weathered schist aquifers represent important hydrological compartments due to their capacity to eliminate nitrate NO3− Under oxygen‐free conditions, nitrate is reduced simultaneously with the oxidation of pyrite leading to the release of sulfate SO42− The aim of the present study is to identify the hydrological conditions under which the weathered schist ground water influences the stream water chemistry, leading to a decrease in NO3− concentration. We measured the ground water head on a small catchment over weathered schist, near the bank and under the streambed, and analyzed the chemical composition of the ground water as well as the stream water on both seasonal and storm‐event timescales. Using SO42− as a tracer of the weathered schist ground water, we showed that ground water inflow caused a decrease of NO3− concentration in the stream during the autumn as well as during storm events in spring and summer. In summer, the NO3− concentration was controlled by the sources of the stream, and in winter by the shallow ground water inflow. The effect of the weathered schist ground water on the NO3− depletion remained relatively limited in time. This effect persisted into late autumn as long as the NO3−–rich shallow ground water did not feed the stream. The duration and intensity of the effect would be extended by decreasing the shallow ground water inflow, which depends on climate as well as the presence of landscape features such as hedges and buffer zones.
Herbicide Selection of Italian Ryegrass under Different Levels of UVB Radiation
Authors: Martínez‐Ghersa M. Alejandra , Aiub Martín M. Vila , Ghersa Claudio M. , Gundel Pedro , Satorre Emilio H. 
Published: June 2010

ABSTRACTUltraviolet‐B radiation is an environmental stress for plants and this situation could become aggravated in the next decades. In this study we used Italian ryegrass (Lolium multiflorum Lam.) as a model system to test whether an environmental stress derived from global change, such as UVB, can influence the efficacy of control procedures and evolution toward herbicide resistance. We grew three generations of Italian ryegrass plants with and without UVB light and subjected them to a series of diclofop‐methyl {(±)‐2‐[4‐(2,4‐dichlorophenoxy) phenoxy] propanoic acid, methyl ester} doses. The effect of selection history was tested with herbicide dose response. The effect of herbicide application on plant survival and biomass varied significantly among herbicide doses and with absence or presence of UVB light. In the absence of herbicide, the decrease in individual fecundity with increasing plant density was similar under both no‐UVB and UVB light treatments. Only plants growing without UVB light increased production of reproductive structures in response to the decrease in density caused by herbicide application. Our study shows that UVB light was a weak stress factor for the ryegrass plants. However, when herbicide selection pressure was high, UVB light reduced the evolution toward herbicide tolerance. When selection pressure on the parental plants was lower, the two stress factors had a synergistic effect, causing changes in herbicide efficacy that in turn had demographic and evolutionary consequences. In the field, these interactions between stress factors might be of significance for annual weeds in which seed output is a major determinant in fitness.
Automated and Continuous Redox Potential Measurements in Soil
Authors: Vorenhout Michel , van der Geest Harm G. , van Marum Daan , Wattel Kees , Eijsackers Herman J. P. 
Published: June 2010

ABSTRACTRedox potential (Eh) describes the electrical state of a matrix. In soils, Eh is an important parameter controlling the persistence of many organic and inorganic compounds. A popular, but also criticized, manual measuring method makes use of a small tip of Pt placed on a copper wire that is placed in the soil; a reference electrode is placed in the same soil at a fixed distance. Fluctuations in redox potential values measured in the soil can be very large and depth‐dependent. This will be overlooked when making single‐point measurements. We developed the datalogger Hypnos 2.0 for continuous redox potential and temperature measurements at various depths in the soil and without disturbance of the site. Hypnos is field‐deployable, relatively cheap, and runs on batteries. The datalogger can use a “sleep mode” between sampling events. In sleep mode, there is no constant voltage on the Pt wire or the reference electrode, but there is only a short pulse during sampling. We did not measure an effect of this short pulse on the measured redox potential. In sandy soils in mesocosms and in a salt marsh soil we measured changes in the Eh as large as from −400 to +100 mV within 4 d, and daily cycles of 200 mV. Both absolute redox potential values and their diurnal variations were depth‐dependent. Because single redox measurements are insufficient in describing redox conditions in some soil systems, Hypnos can be a powerful tool when studying the effects of fluctuating redox conditions on metal availability and pollutant degradation.
An Improved Description of Pesticide Volatilization
Authors: Wolters André , Klein Michael , Vereecken Harry 
Published: June 2010

ABSTRACTThe consideration of pesticide volatilization from soil surfaces as an integral component of pesticide fate models is of importance, especially as part of the Predicted Environmental Concentrations (PEC) models used in the registration procedures for pesticides. The Pesticide Leaching Model (PELMO), which is used in the European registration process, was modified to allow for a reliable prediction of volatilization from soil. The previous PELMO version was upgraded by improving the spatiotemporal discretization at the soil surface, improving the empirical description of temperature dependence of Henry's law constants and including increased sorption of pesticides in dry soils. Comparison of predictions with experimental findings revealed the improvements of PELMO to contribute to a more realistic reflection of measurements, particularly at initial stages of the studies. The broad range of literature values of Henry's law constants was shown to have a significant effect on predicted volatilization fluxes. As a main refinement, the tendency of pesticides toward enhanced volatilization under moist conditions was correctly calculated by the improved model. Variations between model predictions and measurements were due to a lack of experimental data on soil sorption under dry conditions and indicated the need for further calibration of the model. The description of water content in the top layer was subject to uncertainty, which was exemplified by an overestimation of soil moisture during the last days of the field study. Thus, future model improvement will be dependent on experimental support to obtain more detailed information on soil–air–water partitioning of pesticides in the top soil layer.
Forecasting the Number of Soil Samples Required to Reduce Remediation Cost Uncertainty
Authors: Demougeot‐Renard Hélène , de Fouquet Chantal , Renard Philippe 
Published: June 2010

ABSTRACTSampling scheme design is an important step in the management of polluted sites. It largely controls the accuracy of remediation cost estimates. In practice, however, sampling is seldom designed to comply with a given level of remediation cost uncertainty. In this paper, we present a new technique that allows one to estimate of the number of samples that should be taken at a given stage of investigation to reach a forecasted level of accuracy. The uncertainty is expressed both in terms of volume of polluted soil and overall cost of remediation. This technique provides a flexible tool for decision makers to define the amount of investigation worth conducting from an environmental and financial perspective. The technique is based on nonlinear geostatistics (conditional simulations) to estimate the volume of soil that requires remediation and excavation and on a function allowing estimation of the total cost of remediation (including investigations). The geostatistical estimation accounts for support effect, information effect, and sampling errors. The cost calculation includes mainly investigation, excavation, remediation, and transportation. The application of the technique on a former smelting work site (lead pollution) demonstrates how the tool can be used. In this example, the forecasted volumetric uncertainty decreases rapidly for a relatively small number of samples (20–50) and then reaches a plateau (after 100 samples). The uncertainty related to the total remediation cost decreases while the expected total cost increases. Based on these forecasts, we show how a risk‐prone decision maker would probably decide to take 50 additional samples while a risk‐averse decision maker would take 100 samples.
Development of a Phosphorus Index for Pastures Fertilized with Poultry Litter—Factors Affecting Phosphorus Runoff
Authors: DeLaune Paul B. , Moore Philip A. , Carman Dennis K. , Sharpley Andrew N. , Haggard Brian E. , Daniel Tommy C. 
Published: June 2010

ABSTRACTCurrently, several state and federal agencies are proposing upper limits on soil test phosphorus (P), above which animal manures cannot be applied, based on the assumption that high P concentrations in runoff are due to high soil test P. Recent studies show that other factors are more indicative of P concentrations in runoff from areas where manure is being applied. The original P index was developed as an alternative P management tool incorporating factors affecting both the source and transport of P. The objective of this research was to evaluate the effects of multiple variables on P concentrations in runoff water and to construct a P source component of a P index for pastures that incorporates these effects. The evaluated variables were: (i) soil test P, (ii) soluble P in poultry litter, (iii) P in poultry diets, (iv) fertilizer type, and (v) poultry litter application rate. Field studies with simulated rainfall showed that P runoff was affected by the amount of soluble P applied in the fertilizer source. Before manure applications, soil test P was directly related to soluble P concentrations in runoff water. However, soil test P had little effect on P runoff after animal manure was applied. Unlike most other P indices, weighting factors of the P source components in the P index for pastures are based on results from runoff studies conducted under various management scenarios. As a result, weighting factors for the P source potential variables are well justified. A modification of the P index using scientific data should strengthen the ability of the P index concept to evaluate locations and management alternatives for P losses.
Associated Release of Magnesium and Phosphorus from Active and Abandoned Dairy Soils
Authors: Josan M. S. , Nair V. D. , Harris W. G. , Herrera D. 
Published: June 2010

ABSTRACTDairy manure application to soils can result in phosphorus (P)‐related degradation of water quality. The P in these manure‐impacted soils can be labile even years after abandonment and under conditions normally associated with high P stability. Failure of P to stabilize with time compounds the environmental consequences of dairy manure disposal, especially on sandy soils. The objectives of this study were to compare chemical characteristics of active and abandoned dairy manure–impacted soils and minimally impacted soils and to assess the continuous release of P in relation to sparingly soluble salts using repeated water extractions, X‐ray diffraction, and speciation modeling of column leachates. Soil samples from Ap horizons were collected from nine highly manure‐impacted (total P > 1000 mg P kg−1 soil) areas on four active and five abandoned dairies and four minimally impacted soils (total P < 200 mg P kg−1 soil). Soil extracts were analyzed for electrical conductivity (EC), soluble reactive phosphorus (SRP), Ca, Mg, Na, and K. The EC of the soil solutions decreased as active dairy > abandoned dairy > minimally impacted soils. Release of Mg and SRP were significantly correlated (r2 = 0.68) and did not decline after abandonment; Ca release was not correlated with SRP (r2 = 0.01), and declined significantly (p < 0.05) after abandonment. Speciation data from column leachates suggested that Mg‐P phases and/or the most soluble Ca‐P phases could control P solution activities. An implication of this study is that P stabilization via crystallization of calcium phosphates (even at near‐neutral pH) may be preempted by Mg‐P association. Thus, mechanisms to minimize P release may require P‐retaining soil amendments or management of animal rations to eliminate Mg‐P formation.