CALCULATION OF NET NITROGEN MINERALIZATION FROM THE DECOMPOSABLE SOIL ORGANIC MATTER POOL

The calculation of Net Nitrogen Mineralization (NNM) presented in this paper was based on the assumption that soil organic matter carbon may be divided into a stable, texture dependent pool (C_stab) and a labile, decomposable pool (C_dec). Because the C_stab pool is biologically inert due to its interaction with fine-grained mineral soil particles, only the C_dec pool reflects man made changes in the soil organic matter content.
Consequently, to estimate the rate constant of soil organic matter carbon, the CO₂-C production of soils was related to the corresponding amounts of C_dec. Because this rate constant k_dec was derived from incubation experiments, the influence of actual decomposition conditions in the field was calculated according to the concept of “Effective Mineralization Time” (EMT). Setting the C/N ratio of C_dec = 10, the NNM from the C_dec pool was calculated according to the Equation: NNM = 0.1 * C_dec * k_dec* EMT. To evaluate the calculation method of NNM, the nitrogen uptake of plants was related to nitrogen supply.
It was estimated that the mean recovery of N by different vegetable crops grown on plots without mineral nitrogen fertilizer was about 70% of the total nitrogen supply (including the NNM and the N_min values at the start and the end of the cultivation period).

International Workshop on Ecological Aspects of Vegetable Fertilization in Integrated Crop Production

J. Rühlmann

carbon, fertilizer, fraction, rate constant, recommendation, texture

https://doi.org/10.17660/ActaHortic.1999.506.23