Rate of nitrogen mineralized from incorporated crop residues as influenced by temperature.
Vigil M.F. | Kissel D.E.
Methods are needed to predict seasonal mineralization of N when crop residues are added to soils in order to assess N availability to crops. The objective of this investigation was to evaluate and develop methods for predicting the effect of temperature on the rate of N mineralization (Nmin) from crop-residue-amended soils maintained at near-optimum soil water content. Unamended and crop-residue-amended soils were incubated at temperatures between 5 and 35 degrees C to obtain Nmin rates for calculation of Q10 values, defined as the ratio of reaction rates at a temperature interval of 10 degrees C. Measured Q10 depended on the C/N ratio of the residue and incubation time, indicating that for predictive purposes a single Q10 value is inadequate for describing the effect of temperature on crop-residue Nmin. Temperature functions were developed from Nmin data collected from unamended soils incubated at four temperatures under laboratory conditions. These functions were then tested in the MINIMO model (a subroutine of CERES-MAIZE) for residue-amended soils at four temperatures for up to 160 d. Model-predicted mineralizations was close to measured Nmin for most crop-residue-soil mixtures tested. The use of the new temperature equations improved the precision of the model, reducing the residual sum of squares (RSS) from 9797 to 5286. However, the modified model was not able to accurately predict Nmin for crop residues with a C/N ratio of 10 and 28. Inadequate prediction at these C/N ratios may be related to how the model allocates the pool sizes for soluble and insoluble plant N and the cellulose-hemicellulose pool size of the crop residues.
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