Limitations of a calculated N mineralization potential in studies of the N mineralization process |
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Authors: | L Dendooven R Merckx K Vlassak |
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Institution: | (1) Laboratory of Soil Fertility and Soil Biology, Faculty of Agricultural Sciences, KU, Leuven, Kardinaal Mercierlaan 92, 3001 Leuven-Heverlee, Belgium |
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Abstract: | Soil is often incubated under controlled conditions to assess its capacity to mineralize nitrogen and to define the N mineralization potential (No) by fitting a negative exponential curve to N mineralization data. The specificity of No for a given soil and its relevance in N mineralization studies was examined as part of an overall study of the N mineralization process. Soil mixed with an equal amount of sand was aerobically incubated at 35 °C and leached at specific time intervals. Upon leaching, ammonium and nitrate were measured in the extract.It was found that N mineralization data did not always follow first-order kinetics making it difficult to calculate No. The computed No value was influenced by the shape of the curve, the duration of the incubation experiment and was reciprocally related to the N mineralization constant (kexp). No did not always give an adequate indication of the amount of N mineralized and was not soil specific as the time of sampling largely affected its size. The usefulness of No in the simulation of the N mineralization process with a kexp value valid for all soils was limited and a kexp value specific for each soil was required. A value combining the soil specific No and kexp values and reflecting the amount of N mineralized over one year was proposed as a suitable alternative to the use of No in comparative studies of the N mineralization process. It was concluded that a calculated No could not be used in studies comparing the N mineralization of different soils. In addition, the simulation of the N mineralization required the use of the soil specific kexp and could not be carried out with a kexp valid for all soils. |
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Keywords: | aerobic incubation nitrogen mineralization potential Stanford and Smith |
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