Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    In-situ measurement of free trace metal concentrations in a flooded paddy soil using the Donnan Membrane Technique
    Pan, Y. ; Koopmans, G.F. ; Bonten, L.T.C. ; Song, J. ; Luo, Y. ; Temminghoff, E.J.M. ; Comans, R.N.J. - \ 2015
    Geoderma 241-242 (2015). - ISSN 0016-7061 - p. 59 - 67.
    dissolved organic-matter - ray-absorption spectroscopy - copper redox transformation - reduced sulfur groups - ion activity model - sandy soil - humic substances - natural-waters - higher-plants - heavy-metals
    The field Donnan Membrane Technique (DMT) has been used successfully to measure in-situ free trace metal concentrations in surface waters. However, it has not been applied previously in submerged soil systems including flooded paddy rice fields.Wetested this technique in a columnexperimentwith a flooded paddy soil contaminated with trace metals and compared the DMT measurements with predictions from a geochemical speciation model. Flooding led to a strong gradient in the redox potential (Eh) along the soil column, and the pH and concentrations ofMn, Fe, and dissolved organic carbon increased with decreasing Eh. Total dissolved tracemetal concentrations decreased from the overlying water layer to the soil layers, which might be ascribed to the elevated pH outweighing the effect of the increased DOC concentrations under anaerobic conditions. Also, free trace metal concentrations were lower in the soil solution of the upper and bottom soil layers than in the overlying water layer, largely due to the increased pH under anaerobic conditions. The DMT measurements and model predictions were similar in the aerobic water layer, except for Pb. In both anaerobic soil layers, however, Cu and Pb were poorly predicted. The applied geochemical modeling approach, which is frequently being used and performswell under aerobic conditions, does not fully capture all the chemical processes occurring under anaerobic conditions. Overall, the field DMT proved to be a useful tool for the in-situ measurement of free trace metal concentrations in flooded paddy soils.
    Ethoprophos fate on soil-water interface and effects on non-target terrestrial and aquatic biota under Mediterranean crop-based scenarios
    Leitao, S. ; Moreira-Santos, M. ; Brink, P.J. van den; Ribeiro, R. ; Cerejeira, J. ; Sousa, J.P. - \ 2014
    Ecotoxicology and Environmental Safety 103 (2014). - ISSN 0147-6513 - p. 36 - 44.
    species sensitivity distributions - fungicide azoxystrobin - folsomia-candida - sandy soil - pesticides - toxicity - invertebrates - earthworms - bentazone - transport
    The present study aimed to assess the environmental fate of the insecticide and nematicide ethoprophos in the soil-water interface following the pesticide application in simulated maize and potato crops under Mediterranean agricultural conditions, particularly of irrigation. Focus was given to the soil-water transfer pathways (leaching and runoff), to the pesticide transport in soil between pesticide application (crop row) and non-application areas (between crop rows), as well as to toxic effects of the various matrices on terrestrial and aquatic biota. A semi-field methodology mimicking a "worst-case" ethoprophos application (twice the recommended dosage for maize and potato crops: 100% concentration v/v) in agricultural field situations was used, in order to mimic a possible misuse by the farmer under realistic conditions. A rainfall was simulated under a slope of 20° for both crop-based scenarios. Soil and water samples were collected for the analysis of pesticide residues. Ecotoxicity of soil and aquatic samples was assessed by performing lethal and sublethal bioassays with organisms from different trophic levels: the collembolan Folsomia candida, the earthworm Eisenia andrei and the cladoceran Daphnia magna. Although the majority of ethoprophos sorbed to the soil application area, pesticide concentrations were detected in all water matrices illustrating pesticide transfer pathways of water contamination between environmental compartments. Leaching to groundwater proved to be an important transfer pathway of ethoprophos under both crop-based scenarios, as it resulted in high pesticide concentration in leachates from Maize (130µgL(-1)) and Potato (630µgL(-1)) crop scenarios, respectively. Ethoprophos application at the Potato crop scenario caused more toxic effects on terrestrial and aquatic biota than at the Maize scenario at the recommended dosage and lower concentrations. In both crop-based scenarios, ethoprophos moved with the irrigation water flow to the soil between the crop rows where no pesticide was applied, causing toxic effects on terrestrial organisms. The two simulated agricultural crop-based scenarios had the merit to illustrate the importance of transfer pathways of pesticides from soil to groundwater through leaching and from crop rows to the surrounding soil areas in a soil-water interface environment, which is representative for irrigated agricultural crops under Mediterranean conditions.
    Multi-face modeling to predict free zinc ion concentrations in low-zinc soils
    Duffner, A. ; Weng, L. ; Hoffland, E. ; Zee, S.E.A.T.M. van der - \ 2014
    Environmental Science and Technology 48 (2014)10. - ISSN 0013-936X - p. 5700 - 5708.
    donnan membrane technique - organic-matter - heavy-metals - contaminated soils - isotopic exchange - humic substances - trace-metals - sandy soil - adsorption - speciation
    Multi-surface models are widely used to assess the potential ecotoxicological risk in metal-contaminated soils. Their accuracy in predicting metal speciation in soils with low metal levels was not yet tested. Now highly sensitive analytical techniques are available to experimentally validate such models at low concentration levels. The objective of this study was to test the accuracy of a multi-surface model to predict the Zn2+ concentration and to improve our understanding of Zn bioavailability in low-Zn soils. High-Zn soils were included as controls. Model parameters were determined independently on the basis of earlier peer-reviewed publications. Model output was validated against free Zn2+ concentrations determined with the soil column Donnan membrane technique in a range of soils varying in potentially available Zn, organic matter, clay silicate, and iron (hydr)oxide contents and pH. Deviations between predicted Zn2+ concentrations and experimentally determined values over the whole Zn concentration range were less or equal to the experimental standard error, except for one low-Zn soil. The Zn2+ concentration was mainly controlled by adsorption, where organic matter was predicted to be the dominant soil sorbent. The predicted Zn2+ concentration depends more sensitively upon changes of the reactive Zn pool (application of 0.6, 1.2, 2.4, and 3.6 mg of Zn kg–1 of soil) and organic matter content (±0.2 and 0.4%) than pH changes (±0.5 and 1 pH unit).
    Comparative assessment of maize, finger millet and sorghum for household food security in the face of increasing climatic risk
    Rurinda, J. ; Mapfumo, P. ; Wijk, M.T. van; Mtambanengwe, F. ; Rufino, M.C. ; Chikowo, R. ; Giller, K.E. - \ 2014
    European Journal of Agronomy 55 (2014). - ISSN 1161-0301 - p. 29 - 41.
    southern africa - soil fertility - pearl-millet - sandy soil - zimbabwe - variability - management - adaptation - productivity - agriculture
    Questions as to which crop to grow, where, when and with what management, will be increasingly challenging for farmers in the face of a changing climate. The objective of this study was to evaluate emergence, yield and financial benefits of maize, finger millet and sorghum, planted at different dates and managed with variable soil nutrient inputs in order to develop adaptation options for stabilizing food production and income for smallholder households in the face of climate change and variability. Field experiments with maize, finger millet and sorghum were conducted in farmers’ fields in Makoni and Hwedza districts in eastern Zimbabwe for three seasons: 2009/10, 2010/11 and 2011/12. Three fertilization rates: high (90 kg N ha-1, 26 kg P ha-1, 7 t ha-1 manure), low (35 kg N ha-1, 14 kg P ha-1, 3 t ha-1 manure) and a control (zero fertilization); and three planting dates: early, normal and late, were compared. Crop emergence for the unfertilized finger millet and sorghum was 70% for the fertilized treatments. In contrast, the emergence for maize (a medium-maturity hybrid cultivar, SC635), was >80% regardless of the amount of fertilizer applied. Maize yield was greater than that of finger millet and sorghum, also in the season (2010/11) which had poor rainfall distribution. Maize yielded 5.4 t ha-1 compared with 3.1 t ha-1 for finger millet and 3.3 t ha-1 for sorghum for the early plantings in the 2009/10 rainfall season in Makoni, a site with relatively fertile soils. In the poorer 2010/11 season, early planted maize yielded 2.4 t ha-1, against 1.6 t ha-1 for finger millet and 0.4 t ha-1 for sorghum in Makoni. Similar yield trends were observed on the nutrient-depleted soils in Hwedza, although yields were less than those observed in Makoni. All crops yielded significantly more with increasing rates of fertilization when planting was done early or in what farmers considered the ‘normal window’. Crops planted early or during the normal planting window gave comparable yields that were greater than yields of late-planted crops. Water productivity for each crop planted early or during the normal window increased with increase in the amount of fertilizer applied, but differed between crop type. Maize had the highest water productivity (8.0 kg dry matter mm-1 ha-1) followed by sorghum (4.9 kg mm-1 ha-1) and then finger millet (4.6 kg mm-1 ha-1) when a high fertilizer rate was applied to the early-planted crop. Marginal rates of return for maize production were greater for the high fertilization rate (>50%) than for the low rate (100%) than for the high rate (
    A software tool to visualize soil moisture dynamics of an irregular-shaped profile
    Wesseling, J.G. ; Oostindie, K. ; Ritsema, C.J. ; Dekker, L.W. - \ 2013
    Computers and Geosciences 60 (2013). - ISSN 0098-3004 - p. 51 - 57.
    sandy soil
    Software for two dimensional visualization of values that have been automatically measured with in place sensors is difficult to find. Usually these programs assume a regular area and a regular grid of measuring points. In practice, however, both the shape of the area and the position of the sensors are often irregular. This paper describes the program TDRFree, which visualizes the soil moisture content that has been automatically measured with a set of measuring devices distributed over an irregular 2-dimensional soil profile. The output consists of a series of contour-plots which can be easily combined and presented as an animation. It is also possible to generate values for a derived property such as soil water repellency, which depends on moisture content. The program can be applied to any data set that is measured in a 2-dimensional grid.
    Description of the phosphorus sorption and desorption processes in lowland peaty clay soils
    Schoumans, O.F. - \ 2013
    Soil Science 178 (2013)6. - ISSN 0038-075X - p. 291 - 300.
    semiarid altered wetland - acid soils - phosphate adsorption - agricultural land - organic-matter - flooded soils - iron-oxides - sandy soil - aluminum - release
    To determine phosphorus (P) losses from agricultural land to surface water, information is needed about the behavior of P in soils. In this study, the sorption and desorption characteristics of lowland peaty clay soils are described based on experimental laboratory studies. The maximum P sorption capacity is comparable to that of acid sandy soils if based on the amount of oxalate-extractable aluminum and iron. A fraction of the maximum amount of sorbed P is bound reversibly (Q), which can be measured with an iron-impregnated paper. The fraction of the maximum reversibly sorbed P depends on the amount of oxalate-extractable aluminum and iron. In the topsoil, the maximum of the fraction of reversibly bound P (Qm) is about one third of maximum P sorption capacity; and in the subsoil, about two thirds. All sorption and desorption parameters are related to soil characteristics of peat samples.
    Comparison of two methods to assess heterogeneity of water flow in soils
    Lichner, L. ; Dusek, J. ; Dekker, L.W. ; Zhukova, N. ; Fasko, P. ; Holko, L. ; Sir, M. - \ 2013
    Journal of Hydrology and Hydromechanics 61 (2013)4. - ISSN 0042-790X - p. 299 - 304.
    preferential flow - sandy soil - hydrophysical parameters - field experiment - loam - infiltration - movement
    The heterogeneity of water flow and solute transport was assessed during radioactive tracer infiltration experiment in a black clay loam soil using modified methods to estimate the effective cross section (ECS) and the degree of preferential flow (DPF). The results of field and numerical experiments showed that these parameters characterized the heterogeneity of water flow in the soils unequivocally. The ECS decreases non-linearly and the DPF increases linearly with an increase of the bypassing ratio (ratio of macropore flow rate to total flow rate). The ECS decreased and the DPF increased with depth, which suggests an increase in the heterogeneity of water flow with depth. The plot of the DPF against ECS values calculated from the tracer experiment data was consistent with the relationship obtained by the numerical simulation assuming preferential flow in the neighbourhood of three probes.
    Managing soil fertility to adapt to rainful variability in smallholder cropping systems in Zimbabwe
    Rurinda, J. ; Mapfumo, P. ; Wijk, M.T. van; Mtambanengwe, F. ; Rufino, M.C. ; Chikowo, R. ; Giller, K.E. - \ 2013
    Field Crops Research 154 (2013). - ISSN 0378-4290 - p. 211 - 225.
    climate-change - southern africa - sandy soil - corn production - use efficiency - food security - management - maize - farmers - yield
    Adaptation options that address short-term climate variability are likely to lead to short-term benefits and will help to deal with future changes in climate in smallholder cropping systems in Sub-Saharan Africa (SSA). In this study we combined field experimentation and long-term rainfall analyses in Makoni and Hwedza districts in eastern Zimbabwe to evaluate cropping adaptation options to climate variability. Analyses of long-term rainfall data closely supports farmers’ perceptions that the mean annual total rainfall has not changed, but the pattern of rainfall within-season has changed: the number of rainfall days has decreased, and the frequency of dry spells has increased at the critical flowering stage of maize. On-farm experiments were conducted over two cropping seasons, 2009/10 and 2010/11 to assess the effects of planting date, fertilization and cultivar on maize production. Three maize cultivars were sown in each of the early, normal and late planting windows defined by farmers. Each of the nine cultivar-planting date combinations received N, P, K and manure combinations at either zero, low or high fertilization rates. Overall, there were no significant differences in maize development or grain yield among cultivars. Maize grain yield was increased by increasing the amount of nutrients applied. Average yield was 2.5 t ha-1 for the low rate and 5.0 t ha-1 for the high rate on early planted cultivars on relatively fertile soils in Makoni in 2009/10 season. Yields on poorer soils in Hwedza were small, averaging 1.5 t ha-1 for the low rate and 2.5 t ha-1 for the high rate. Maize grain yields for the early and normal planted cultivars were similar for each fertilization rate, suggesting there is a wide planting window for successful establishment of crops in response to increased rainfall variability. Yield reduction of >50% was observed when planting was delayed by 4 weeks (late planting) regardless of the amount of fertilizer applied. Soil nutrient management had an overriding effect on crop production, suggesting that although the quality of within-season rainfall is decreasing, nutrient management is the priority option for adaptation in rain-fed smallholder cropping systems.
    The Influence of Long-Term Copper Contaminated Agricultural Soil at Different pH Levels on Microbial Communities and Springtail Transcriptional Regulation
    Boer, T.E. de; Tas, N. ; Braster, M. ; Temminghoff, E.J.M. ; Roling, W.F.M. ; Roelofs, D. - \ 2012
    Environmental Science and Technology 46 (2012)1. - ISSN 0013-936X - p. 60 - 68.
    heavy-metal contamination - bacterial community - organic status - fungal communities - arable soil - sandy soil - diversity - toxicity - microorganisms - microarray
    Copper has long been applied for agricultural practises. Like other metals, copper is highly persistent in the environment and biologically active long after its use has ceased. Here we present a unique study on the long-term effects (27 years) of copper and pH on soil microbial communities and on the springtail Folsomia candida an important representative of the soil macrofauna, in an experiment with a full factorial, random block. design. Bacterial communities were mostly affected by pH. These effects were prominent in Acidobacteria, while Actinobacteria and Gammaroteobacteria communities were affected by original and bioavailable copper. Reproduction and survival of the collembolan F. candida was not affected by the studied copper concentrations. However, the transcriptomic responses to copper reflected a mechanism of copper transport and detoxification, while pH exerted effects on nucleotide and protein metabolism and (acute) inflammatory response. We conclude that microbial community structure reflected the history of copper contamination, while gene expression analysis of F. candida is associated with the current level of bioavailable copper. The study is a first step in the development of a molecular strategy aiming at a more comprehensive assessment of various aspects of soil quality and ecotoxicology.
    A novel method for quantifying nitrous oxide reduction in soil
    Klefoth, R.R. ; Oenema, O. ; Groenigen, J.W. van - \ 2012
    Vadose Zone Journal 11 (2012)4. - ISSN 1539-1663 - 7 p.
    n2o production - sandy soil - denitrification - emissions - subsoil - fractionation - management - atmosphere - dynamics - columns
    A method to quantify the biochemical conversion of the strong greenhouse gas N2O into the environmentally benign N2 was developed. It is based on N2O gas diffusing through a soil core under specified laboratory conditions. Soil moisture level in the soil significantly influenced the N2O reduction potential of the soil. Nitrous oxide is produced in soil by nitrifying and denitrifying microorganisms. Most of the N2O produced in soil is reduced to N2 in the final step of denitrification, and only a fraction is released into the atmosphere. No reliable methods exist, however, to quantify N2O reduction and its controlling parameters in soil. In this study, we investigated: (i) a novel method to quantify the reduction of N2O in soil as it diffuses upward; and (ii) the effects of soil moisture content on N2O reduction. We developed a setup where a silicone tube coil permeable to N2O linked to an N2O reservoir simulated a subsoil with a known, artificial N2O source. A soil core filled with repacked sandy soil (a Typic Endoaquoll) was placed on top of the silicone coil. Experimental treatments included water-filled pore space (WFPS) levels of 60, 75, and 90%, as well as a quartz sand treatment at 90% WFPS that served as an abiotic control. Soil surface N2O emissions were measured for 21 d, and after the experiment, residual N2O in the system was determined. During the experiment, 41, 39, and 0% of the applied N2O was emitted as soil surface flux for the 60, 75, and 90% WFPS treatments, respectively. In the 90% WFPS treatment, 52% of applied N2O was reduced to N2. We conclude that our method enables us to quantify N2O reduction in soil columns. Our results further show that wet soils can be effective in reducing N2O to N2 during upward diffusion from the subsoil.
    Simulation of movement of pesticides towards drains with a preferential flow version of PEARL
    Tiktak, A. ; Hendriks, R.F.A. ; Boesten, J.J.T.I. - \ 2012
    Pest Management Science 68 (2012)2. - ISSN 1526-498X - p. 290 - 302.
    dutch clay soil - unsaturated soils - solute transport - macropore flow - water-flow - sandy soil - model - infiltration - rainfall - bromide
    Background: As part of the Dutch authorisation procedure for pesticides, an assessment of the effects on aquatic organisms in surface waters adjacent to agricultural fields is required. The peak concentration is considered to be the most important exposure endpoint for the ecotoxicological effect assessment. Macropore flow is an important driver for the peak concentration, so the leaching model PEARL was extended with a macropore module. The new model has two macropore domains: a bypass domain and an internal catchment domain. The model was tested against data from a field leaching study on a cracking clay soil in the Netherlands.Results: Most parameters of the model could be obtained from site-specific measurements, pedotransfer functions and general soil structural knowledge; only three macropore-flow-related parameters needed calibration. The flow-related macropore parameters could not be calibrated without using the concentration in drain water. Sequential calibration strategies, in which firstly the water flow model and then the pesticide fate model are calibrated, may therefore be less suitable for preferential flow models.Conclusion: After calibration, PEARL could simulate well the observed rapid movement towards drains of two pesticides with contrasting sorption and degradation rate properties. The calibrated value for the fraction of the internal catchment domain was high (90%). This means that a large fraction of water entering the macropores infiltrates into the soil matrix, thus reducing the fraction of rapid flow.
    Natural and fire-induced soil water repellency in a Portugese Shrubland
    Stoof, C.R. ; Moore, D. ; Ritsema, C.J. ; Dekker, L.W. - \ 2011
    Soil Science Society of America Journal 75 (2011)6. - ISSN 0361-5995 - p. 2283 - 2295.
    coarse-textured soils - forest soils - pine forests - hydrological behavior - eucalyptus-globulus - spatial variability - prescribed fire - sandy soil - hydrophobicity - moisture
    Post-fire land degradation is often attributed to fire-induced soil water repellency, despite the fact that soil water repellency is a natural phenomenon in many soils and is therefore not necessarily caused by fire. To improve our understanding of the role of soil water repellency in causing fire-induced land degradation, a long-term monitoring study was performed in which the temporal variation of topsoil water repellency (0–2.5-cm depth) was captured in a Portuguese shrubland before and after fire between November 2007 and March 2010. In addition, similarities and dissimilarities between changes following burning and clipping were assessed in a plot experiment. Soil water repellency appeared to be the rule rather than the exception, both before and after fire, and was strongly related to soil moisture and organic matter content. Surprisingly, despite the low soil temperatures during the fire (60°C) and the lack of direct soil moisture changes, fire significantly increased the persistence of soil water repellency (the water drop penetration time). Vegetation removal by burning and clipping played a key role in determining post-fire water repellency in litter and at the soil surface and considerably reduced the time needed to both develop and eliminate water repellency of the litter and surface soil. Where pre-fire (or “natural”) soil water repellency is abundant, an increase in erosion after fire cannot be solely caused by soil water repellency. Nevertheless, fire-induced removal of the protective canopy cover may increase the hydrologic significance of soil water repellency in burned landscapes
    Hydropedological insights when considering catchment classification
    Bouma, J. ; Droogers, P. ; Sonneveld, M.P.W. ; Ritsema, C.J. ; Hunink, J.E. ; Immerzeel, W.W. ; Kauffman, S. - \ 2011
    Hydrology and Earth System Sciences 15 (2011). - ISSN 1027-5606 - p. 1909 - 1919.
    simulate preferential flow - repellent porous-media - remotely-sensed data - land-use history - sandy soil - modeling approach - water repellency - loess plateau - clay soil - infiltration
    Soil classification systems are analysed to explore the potential of developing classification systems for catchments. Soil classifications are useful to create systematic order in the overwhelming quantity of different soils in the world and to extrapolate data available for a given soil type to soils elsewhere with identical classifications. This principle also applies to catchments. However, to be useful, soil classifications have to be based on permanent characteristics as formed by the soil forming factors over often very long periods of time. When defining permanent catchment characteristics, discharge data would therefore appear to be less suitable. But permanent soil characteristics do not necessarily match with characteristics and parameters needed for functional soil characterization focusing, for example, on catchment hydrology. Hydropedology has made contributions towards the required functional characterization of soils as is illustrated for three recent hydrological catchment studies. However, much still needs to be learned about the physical behaviour of anisotropic, heterogeneous soils with varying soil structures during the year and about spatial and temporal variability. The suggestion is made therefore to first focus on improving simulation of catchment hydrology, possibly incorporating hydropedological expertise, before embarking on a catchment classification effort which involves major input of time and involves the risk of distraction. In doing so, we suggest to also define other characteristics for catchment performance than the traditionally measured discharge rates. Such characteristics may well be derived from societal issues being studied, as is illustrated for the Green Water Credits program.
    Strategies in the application of the Donnan membrane technique.
    Weng, L.P. ; Vega, F.A. ; Riemsdijk, W.H. van - \ 2011
    Environmental Chemistry 8 (2011)5. - ISSN 1448-2517 - p. 466 - 474.
    metal-ion concentrations - soil solution - chemical speciation - organic-matter - heavy-metals - sandy soil - dynamic speciation - humic substances - model parameters - trace-metals
    e Donnan membrane technique (DMT) can be applied to measure free ion concentrations both in laboratory and in situ in the field. In designing DMT experiments, different strategies can be taken, depending on whether accumulation is needed. (1) When the free ion concentration is above the detection limit of the analytical technique (e.g. ICP-MS), no accumulation is needed and no ligand is added to the acceptor. Measurement can be based on the Donnan membrane equilibrium. (2) When an accumulation of less than 500 times is needed, an appropriate amount of ligand can be added to the acceptor and measurement can be based on the Donnan membrane equilibrium. (3) When an accumulation factor of larger than 500 times is needed, a relatively large amount of ligand is added to the acceptor and measurement can be based on the transport kinetics. In this paper, several issues in designing the DMT experiments are discussed: choice of DMT cell, measurement strategies and ligands and possible implication of slow dissociation of metal complexes in the sample solution (lability issue). The objective of this paper is to give better guidance in the application of DMT for measuring free ion concentrations in both synthetic and natural samples.
    Towards an agronomic assessment of N2O emissions: a case study for arable crops
    Groenigen, J.W. van; Velthof, G.L. ; Oenema, O. ; Groenigen, K.J. van; Kessel, C. van - \ 2010
    European Journal of Soil Science 61 (2010)6. - ISSN 1351-0754 - p. 903 - 913.
    nitrous-oxide emissions - greenhouse-gas emissions - fertilizer nitrogen - n-fertilization - wheat rotation - sandy soil - long-term - management - tillage - systems
    Agricultural soils are the main anthropogenic source of nitrous oxide (N2O), largely because of nitrogen (N) fertilizer use. Commonly, N2O emissions are expressed as a function of N application rate. This suggests that smaller fertilizer applications always lead to smaller N2O emissions. Here we argue that, because of global demand for agricultural products, agronomic conditions should be included when assessing N2O emissions. Expressing N2O emissions in relation to crop productivity (expressed as above-ground N uptake: ‘yield-scaled N2O emissions') can express the N2O efficiency of a cropping system. We show how conventional relationships between N application rate, N uptake and N2O emissions can result in minimal yield-scaled N2O emissions at intermediate fertilizer-N rates. Key findings of a meta-analysis on yield-scaled N2O emissions by non-leguminous annual crops (19 independent studies and 147 data points) revealed that yield-scaled N2O emissions were smallest (8.4 g N2O-N kg-1N uptake) at application rates of approximately 180–190 kg N ha-1 and increased sharply after that (26.8 g N2O-N kg-1 N uptake at 301 kg N ha-1). If the above-ground N surplus was equal to or smaller than zero, yield-scaled N2O emissions remained stable and relatively small. At an N surplus of 90 kg N ha-1 yield-scaled emissions increased threefold. Furthermore, a negative relation between N use efficiency and yield-scaled N2O emissions was found. Therefore, we argue that agricultural management practices to reduce N2O emissions should focus on optimizing fertilizer-N use efficiency under median rates of N input, rather than on minimizing N application rates.
    Pesticide Leaching from Agricultural Fields with Ridges and Furrows
    Leistra, M. ; Boesten, J.J.T.I. - \ 2010
    Water Air and Soil Pollution 213 (2010)1-4. - ISSN 0049-6979 - p. 341 - 352.
    irrigated potato - sandy soil - water - transport - stemflow - flow
    In the evaluation of the risk of pesticide leaching to groundwater, the soil surface is usually assumed to be level, although important crops like potato are grown on ridges. A fraction of the water from rainfall and sprinkler irrigation may flow along the soil surface from the ridges to the furrows, thus bringing about an extra load of water and pesticide on the furrow soil. A survey of the literature reveals that surface-runoff from ridges to furrows is a well-known phenomenon but that hardly any data are available on the quantities of water and pesticide involved. On the basis of a field experiment with additional sprinkler irrigation, computer simulations were carried out with the Pesticide Emission Assessment at Regional and Local scales model for separate ridge and furrow systems in a humic sandy potato field. Breakthrough curves of bromide ion (as a tracer for water flow) and carbofuran (as example pesticide) were calculated for 1-m depth in the field. Bromide ion leached comparatively fast from the furrow system, while leaching from the ridge system was slower showing a maximum concentration of about half of that for the furrow system. Carbofuran breakthrough from the furrow system began about a month after application and increased steadily to substantial concentrations. Because the transport time of carbofuran in the ridge soil was much longer, no breakthrough occurred in the growing season. The maximum concentration of carbofuran leaching from the ridge–furrow field was computed to be a factor of six times as high as that computed for the corresponding level field. The study shows that the risk of leaching of pesticides via the furrow soil can be substantially higher than that via the corresponding level field soil.
    Uncertainly analysis of the nonideal competitive adsorption-Donnan model: effects of dissolved organic matter vaiability on predicted metal speciation in soil solution.
    Groenenberg, J.E. ; Koopmans, G.F. ; Comans, R.N.J. - \ 2010
    Environmental Science and Technology 44 (2010)4. - ISSN 0013-936X - p. 1340 - 1346.
    humic substances - fresh-waters - heavy-metals - ion-binding - sandy soil - cu - complexation - pb - parameters - acids
    Ion binding models such as the nonideal competitive adsorption-Donnan model (NICA-Donnan) and model VI successfully describe laboratory data of proton and metal binding to purified humic substances (HS). In this study model performance was tested in more complex natural systems. The speciation predicted with the NICA-Donnan model and the associated uncertainty were compared with independent measurements in soil solution extracts, including the free metal ion activity and fulvic (FA) and humic acid (HA) fractions of dissolved organic matter (DOM). Potentially important sources of uncertainty are the DOM composition and the variation in binding properties of HS. HS fractions of DOM in soil solution extracts varied between 14 and 63% and consisted mainly of FA. Moreover, binding parameters optimized for individual FA samples show substantial variation. Monte Carlo simulations show that uncertainties in predicted metal speciation, for metals with a high affinity for FA (Cu, Pb), are largely due to the natural variation in binding properties (i.e., the affinity) of FA. Predictions for metals with a lower affinity (Cd) are more prone to uncertainties in the fraction FA in DOM and the maximum site density (i.e., the capacity) of the FA. Based on these findings, suggestions are provided to reduce uncertainties in model predictions
    Speciation of Water-Extractable Organic Nutrients in Grassland Soils
    Ros, G.H. ; Tschudy, T.C. ; Chardon, W.J. ; Temminghoff, E.J.M. ; Salm, C. van der; Koopmans, G.F. - \ 2010
    Soil Science 175 (2010)1. - ISSN 0038-075X - p. 15 - 26.
    phosphorus-compounds - forest floor - sandy soil - matter fractions - mineral soil - heavy-metals - nitrogen don - land-use - carbon - temperature
    The release of dissolved organic matter (DOM) from agricultural land can have a large impact on the transport of N and phosphorus (P) to surface waters leading to water quality impairment. The speciation of DOM in agricultural grassland soils has received little attention thus far. Quantification of DOM speciation can improve our knowledge of its fate in these soils. Furthermore, the influence of temperature on DOM concentration and composition is still ambiguous. In this study, we determined the concentration and composition of water-extractable organic carbon (EOC), water-extractable organic N (EON), and water-extractable organic P (EOP) before and after incubation of sand, peat, and clay grassland soils at different temperatures (1.5 °C, 10 °C, and 20 °C) for 35 days. Extracted organic compounds were fractioned in three operationally defined fractions: humic acids (HA), fulvic acids (FA), and hydrophilic (Hy) compounds using a recently developed batch fractionation method. Both EON and EOP formed a major fraction of total N and P. Concentrations of EOC, EON, and EOP were different among the sand, peat, and clay soils, but their speciation was remarkably similar. The EOC and EON were mainly present in the hydrophobic form (HA and FA), whereas EOP was mainly present in the Hy fraction. An increase in temperature generally resulted in a decrease of the total EOC, EON, and EOP concentrations, whereas the speciation remained constant. The effect of temperature on the dynamics of DOM is not necessarily related to net changes in pool size of the HA, FA, and Hy fractions. Insight into the influence of incubation temperature on the dynamics of EOC, EON, and EOP can only be achieved when the processes responsible for the consumption and the production of dissolved organic nutrients are quantified
    Donnan Membrane Technique (DMT) for Anion Measurement
    Alonso Vega, M.F. ; Weng, L.P. ; Temminghoff, E.J.M. ; Riemsdijk, W.H. van - \ 2010
    Analytical Chemistry 82 (2010)7. - ISSN 0003-2700 - p. 2932 - 2939.
    dissolved organic-matter - metal-ion concentrations - soil solution - chemical speciation - heavy-metals - sandy soil - colloidal particles - aqueous-solutions - water extracts - activity model
    Donnan membrane technique (DMT) is developed and tested for determination of free anion concentrations. Time needed to reach the Donnan membrane equilibrium depends on type of ions and the background. The Donnan membrane equilibrium is reached in 1 day for Cl-, 1-2 days for NO3-, 1-4 days for SO42- and SeO42-, and 1-14 days for H2PO4- in a background of 2-200 mM KCl or K2SO4. The strongest effect of ionic strength on equilibrium time is found for H2PO4-, followed by SO42- and SeO42-, and then by Cl- and NO3-. The negatively charged organic particles of fulvic and humic acids do not pass the membrane. Two approaches for the measurement of different anion species of the same element, such as SeO42- and HSeO3-, using DMT are proposed and tested. These two approaches are based on transport kinetics or response to ionic strength difference. A transport model that was developed previously for cation DMT is applied in this work to analyze the rate-limiting step in the anion DMT. In the absence of mobile/labile complexes, transport tends to be controlled by diffusion in solution at a low ionic strength, whereas at a higher ionic strength, diffusion in the membrane starts to control the transport
    Transfer functions for solid-solution partitioning of cadmium, copper, nickel, lead and zinc in soils: derivation of relationships for free metal ion activities and validation with independent data
    Groenenberg, J.E. ; Römkens, P.F.A.M. ; Comans, R.N.J. ; Luster, J. ; Pampura, T. ; Shotbolt, L. ; Tipping, E. ; Vries, W. de - \ 2010
    European Journal of Soil Science 61 (2010)1. - ISSN 1351-0754 - p. 58 - 73.
    dissolved organic-matter - donnan membrane technique - contaminated soils - heavy-metals - sandy soil - chemical speciation - trace-metals - pore-water - ph - cu
    Models to predict the solid-solution partitioning of trace metals are important tools in risk assessment, providing information on the biological availability of metals and their leaching. Empirically based models, or transfer functions, published to date differ with respect to the mathematical model used, the optimization method, the methods used to determine metal concentrations in the solid and solution phases and the soil properties accounted for. Here we review these methodological aspects before deriving our own transfer functions that relate free metal ion activities to reactive metal contents in the solid phase. One single function was able to predict free-metal ion activities estimated by a variety of soil solution extraction methods. Evaluation of the mathematical formulation showed that transfer functions derived to optimize the Freundlich adsorption constant (Kf), in contrast to functions derived to optimize either the solid or solution concentration, were most suitable for predicting concentrations in solution from solid phase concentrations and vice versa. The model was shown to be generally applicable on the basis of a large number of independent data, for which predicted free metal activities were within one order of magnitude of the observations. The model only over-estimated free-metal ion activities at alkaline pH (>7). The use of the reactive metal content measured by 0.43 m HNO3 rather than the total metal content resulted in a close correlation with measured data, particularly for nickel and zinc
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