Simulating effects of MERN and other BMPs on subsurface drainage water quality and crop yield in southern Ontario

摘要

In Ontario, the Most Economic Rate of Nitrogen (MERN) application is being promoted to achieve optimal crop production. However, the potential long-term environmental impact of such nitrogen (N) application rates is not yet known. The Root Zone WaterQuality Model (RZWQM) was used to evaluate the long-term effect of MERN, side-dress versus pré-plant N application, split N applications over the growing season, pre side-dress N test (PSNT), and reduced N application through crop rotation on crop yieldand nitrate-nitrogen (NO_3-N) loss through the tile drainage system. The results indicate that MERN for corn production fluctuates significantly from year-to-year in response to annual climatic conditions. However, the long-term average MERN of 184 kg/ha was close to current corn production recommendation of 175 kg/ha. The results of this study also indicate that planting time N application could result in slightly (1.4%) higher NO_3-N losses in the tile outflow than side-dress application of nitrogen.Split applications of N could lead to 11.3% reduction in long-term annual NO_3-N loads but this practice can also result in about 7.6% decline in long-term com yield compared to MERN application at planting time. Overall, this study shows that under Ontario conditions timing and rate of nitrogen applications are important in minimizing the amount of NO_3-N losses to subsurface drains, particularly during the late winter and spring seasons.