Abstract
A simple first-order mathematical function is presented to describe net nitrogen (N) immobilization and mineralization from organic materials spread on or incorporated into horticultural soils. To facilitate the representation of immobilization, kinetics are determined by a conveniently measured carbon dioxide (CO2-C) evolution rate. Other parameters include a substrate conversion efficiency, the C:N ratio of microbial decomposers, and the initial C and N contents of the materials. The model was parameterized using a previously reported incubation study of uncomposted lawn trimming materials (Sullivan et al., 2004). To avoid overfitting, parameters are lumped between the different treatments whenever reasonable. All parameters were lumped except for two labile/recalcitrant partition factors, one for C and one for N. Results for each of eight lawn trimming materials represented evolving C very well (r2=0.99). Nitrogen immobilization and release fits were reasonable (r2=0.71), predicting immobilization and mineralization appropriately. Parameterization options based on proximate carbon analysis were also introduced.
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