Optimized N-mineralization parameters of loess soils from incubation experiments

Summary Nitrogen mineralization from long term incubation experiments with dried loess soils from southern Lower Saxony has been split by an optimization procedure into three contributing fractions: one from the resistant organic material (index rpm), another from decomposable plant residues (index dpm), and a third one from autolyzing microbial biomass (index bom). The nitrogen contents at the end of February averages 650 kg nitrogen per hectare and the 30 cm arable layer for the rpm, 30 to 50 kg N/ha for the dpm and about 65 kg N/ha for microbial biomass. The corresponding mean reaction coefficients at 35°C are .0058, .16 and about .35 per day, respectively. A rough approximation of the temperature dependence of the reaction coefficients has also been estimated.This paper was presented in part at the 1981 Congress of the German Soil Science Society held in Berlin, and at a colloquium at the Institute of Soil Chemistry, Pisa, Italy, Oct. 19th, 1981; nothing of it has been published before, however.