Net mineralization and nitrification rates in a clay soil measured and predicted in permanent grassland from soil temperature and moisture content |
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Authors: | J H Macduff R E White |
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Institution: | (1) Department of Agricultural Science, University of Oxford, Parks Road, OX1 3PF Oxford, UK;(2) Present address: Department of Soil Science, University of Reading, London Road, RG1 5AQ Reading, UK |
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Abstract: | Summary Net mineralization of N and net nitrification in field-moist clay soils (Evesham-Kingston series) from arable and grassland sites were measured in laboratory incubation experiments at 4, 10 and 20°C. Three depth fractions to 30 cm were used. Nitrate accumulated at all temperatures except when the soil was very dry ( =0.13 cm3 cm–3). Exchangeable NH4-ions declined during the first 24 h and thereafter remained low. Net mineralization and net nitrification approximated to zero-order reactions after 24 h, with Q10 values generally <1.6. The effect of temperature on both processes was linear although some results conformed to an Arrhenius-type relationship. The dependence of net mineralization and net nitrification in the field soil on soil temperature (10 cm depth) and moisture (0–15, 15–25, 25–35 cm depths) was modelled using the laboratory incubation data. An annual net mineralization of 350 kg N ha–1 and net nitrification of 346 kg N ha–1 were predicted between September 1980 and August 1981. The model probably overstressed the effect of soil moisture relative to soil temperature. |
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Keywords: | Ammonification Clay soil Exchangeable ammonium Grassland Incubation Kinetics Nitrate Nitrification N cycle N mineralization Soil Moisture Soil temperature |
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