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 = N 0 [1‐e − k t ] where N 0 is potentially mineralizable N and k is the mineralization rate constant) to predict growing season soil N supply (SNS) in potato ( Solanum tuberosum L.) fields under cool humid climatic conditions. Direct application of the kinetic model for the 0‐ to 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 N 0 , 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.