Prediction of Soil Nitrogen Supply in Potato Fields in a Cool Humid Climate.

This study evaluated different strategies for use of a simple first-order kinetic model (N_min= N₀ [1-e^-kt] where N₀ is potentially mineralizable N and k is the mineralization rate constant) to predict growing season soil N supply (SNS) in potato fields under cool humid climatic conditions. Direct application of the kinetic model for 0-15 cm depth significantly underestimated a field-based measure of plant available soil N supply (PASNS). Modeling strategies that considered the soil mineral N (SMN) present at the start of the growing season, or included a pool of labile mineralizable N (Pool I) not normally considered in determination of N₀, performed better, but still underestimated high values of PASNS. Strategies which included a greater soil depth (0-30 cm), or which assumed that the mineralizable N pool was replenished during the growing season, overestimated PASNS. A strategy which used a higher value of k for Pool I gave the most promising results. Results of this study highlight the importance of considering both SMN and labile mineralizable N pools in predicting SNS, and suggest that it is possible to estimate growing season SNS in humid regions using simple kinetic models.