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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    We will mail you new results for this query: keywords==calcium-chloride
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Asymmetric flow field-flow fractionation of manufactured silver nanoparticles spiked into soil solution
Koopmans, G.F. ; Hiemstra, T. ; Regelink, I.C. ; Molleman, B. ; Comans, R.N.J. - \ 2015
Journal of Chromatography. A, Including electrophoresis and other separation methods 1392 (2015). - ISSN 0021-9673 - p. 100 - 109.
natural organic-matter - engineered nanoparticles - calcium-chloride - ionic-strength - humic acids - molar-mass - aggregation - retention - ph - speciation
Manufactured metallic silver nanoparticles (AgNP) are intensively utilized in consumer products and this will inevitably lead to their release to soils. To assess the environmental risks of AgNP in soils, quantification of both their concentration and size in soil solution is essential. We developed a methodology consisting of asymmetric flow field-flow fractionation (AF4) in combination with on-line detection by UV–vis spectroscopy and off-line HR-ICP-MS measurements to quantify the concentration and size of AgNP, coated with either citrate or polyvinylpyrrolidone (PVP), in water extracts of three different soils. The type of mobile phase was a critical factor in the fractionation of AgNP by AF4. In synthetic systems, fractionation of a series of virgin citrate- and PVP-coated AgNP (10–90 nm) with reasonably high recoveries could only be achieved with ultrahigh purity water as a mobile phase. For the soil water extracts, 0.01% (w:v) sodium dodecyl sulfate (SDS) at pH 8 was the key to a successful fractionation of the AgNP. With SDS, the primary size of AgNP in all soil water extracts could be determined by AF4, except for PVP-coated AgNP when clay colloids were present. The PVP-coated AgNP interacted with colloidal clay minerals, leading to an overestimation of their primary size. Similar interactions between PVP-coated AgNP and clay colloids can take place in the environment and facilitate their transport in soils, aquifers, and surface waters. In conclusion, AF4 in combination with UV–vis spectroscopy and HR-ICP-MS measurements is a powerful tool to characterize AgNP in soil solution if the appropriate mobile phase is used.
The arable farmer as the assessor of within-field soil variation
Heijting, S. ; Bruin, S. de; Bregt, A.K. - \ 2011
Precision Agriculture 12 (2011)4. - ISSN 1385-2256 - p. 488 - 507.
management zones - electrical-conductivity - precision agriculture - calcium-chloride - knowledge - information - variability - maps - community
Feasible, fast and reliable methods of mapping within-field variation are required for precision agriculture. Within precision agriculture research much emphasis has been put on technology, whereas the knowledge that farmers have and ways to explore it have received little attention. This research characterizes and examines the spatial knowledge arable farmers have of their fields and explores whether it is a suitable starting point to map the within-field variation of soil properties. A case study was performed in the Hoeksche Waard, the Netherlands, at four arable farms. A combination of semi-structured interviews and fieldwork was used to map spatially explicit knowledge of within-field variation. At each farm, a field was divided into internally homogeneous units as directed by the farmer, the soil of the units was sampled and the data were analysed statistically. The results show that the farmers have considerable spatial knowledge of their fields. Furthermore, they apply this knowledge intuitively during various field management activities such as fertilizer application, soil tillage and herbicide application. The sample data on soil organic matter content, clay content and fertility show that in general the farmers’ knowledge formed a suitable starting point for mapping within-field variation in the soil. Therefore, it should also be considered as an important information source for highly automated precision agriculture systems.
Nitrogen Fractions in Arable Soils in Relation to Nitrogen Mineralization and Plant Uptake
Bregliani, M. ; Temminghoff, E.J.M. ; Riemsdijk, W.H. van; Hagg, E.S. - \ 2006
Communications in Soil Science and Plant Analysis 37 (2006)11-12. - ISSN 0010-3624 - p. 1571 - 1586.
0.01 m cacl2 - organic nitrogen - n mineralization - extraction procedure - calcium-chloride - biomass
Nitrogen (N) as a major constituent of all plants is one of the most important nutrients. Minimizing input of mineral nitrogen fertilizer is needed to avoid harm to the environment. Optimal input of mineral nitrogen should take the nitrogen supply of the soil into account. Many different soil tests have been proposed for determining soil nitrogen availability. In this article we present a new approach that is based on the measurement of nitrate, ammonium, and dissolved organic nitrogen (DON) in a 0.01 M CaCl2 soil extract. Eighteen agricultural soils, differing widely in the availability of nitrogen were used, fertilized and unfertilized. It is shown that the nitrogen uptake by maize plants (Zea Mays L.) in both ¿N-fertilized¿ and ¿N-unfertilized¿ soils as measured in a pot experiment can be described with a simple model using the measured nitrogen fractions in the extract. The main source of nitrogen uptake by the plants is the mineralized organic nitrogen during the growing period. It is shown that the initial measured DON fraction is a good indicator of the nitrogen mineralized during plant growth
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