A scalable, long-term assessment of N2O emission from the Midwest agroecosystem

Abstract:

Excess application of N-fertilizer has been pervasive among the Midwest farmers because of the relatively cheap fertilizer cost compared to the possible yield losses caused by N deficit. The surplus N input lost from the agroecosystem through multiple pathways such as N leaching and N2O emission has become a major threat to the environment. To help farmers and policymakers manage N in smarter and more sustainable ways, deeper mechanistic understanding and better quantification of these N losses are needed. This study presents our first step to develop a reliable and effective tool for spatially-explicit, field-based assessment of different N-fertilizer practices that can be scalable. Using long-term experiment data collected from two research centers in Minnesota and Wisconsin, we trained a process-based crop model, Ecosys, to simulate the variation of N2O emissions from three different crop systems: continuous corn, corn-soybean rotation, and corn-alfalfa-alfalfa-alfalfa rotation. Model configurations are prepared in a scalable way such that satellite observations, reanalysis weather products and SSURGO soil data replace all local measurements. With the well calibrated model, we further evaluate the N2O emissions in response to concurrent environmental conditions, and compare the effects of intensive versus conservative management practices. Our study has demonstrated the potential of constraining crop model simulations with several publicly available geospatial datasets, in particular, satellite-derived products, for realistic simulation of N losses at field scale.