Soil nitrogen availability evaluated by kinetic mineralization parameters

Mathematical models can be used to test or predict observed phenomena or experimental data in order to assist the development of suitable tillage practices. This article describes the kinetic nitrogen (N) mineralization parameters for the corn crop in soils from Rio Grande do Sul State, Brazil. Experiments were carried out to determine the total N mineralized over 32 weeks of incubation and the uptake by corn (Zea mays L.) plants 45 days after planting. A comparison of the experimental results with the kinetic parameters calculated using eight different algorithms showed that mineralized or potentially mineralizable N (N-o) was best described by the active N fraction of N mineralization. The active fraction and N-o described by a hyperbolic equation, were the best predictive parameters for nitrogen availability to corn. Potentially mineralizable N could not be estimated adequately in this experiment by the double exponential models and by its parameters described as labile and recalcitrant or easily and not easily mineralizable N. The conclusion is that no different fractions estimated by mathematical equations make up the organic N content during the incubation period employed here, and that this property is best estimated by the N. concept.