An Integrated Multi-Media Modeling System for Regional- to National-Scale Nitrogen and Crop Productivity Assessments.

Excessive nutrients transported from agricultural fields into the environment are causing environmental and ecological problems. This study uses an integrated multi-media modeling system version 1 (IMMMS 1.0) linking air, land surface, and watershed processes to assess corn grain yield and nitrogen (N) losses resulting from changing fertilization conditions across the contiguous United States. Two fertilizer management scenarios (FMSs) were compared and evaluated: 2006 FMS, developed based on the 2006 fertilizer sales data; and 2011 FMS, developed based on 2011 fertilizer sales and manure. Corn grain yields captured historical reported values with average percent errors of 4.8% and 0.7% for the 2006 FMS and 2011 FMS, respectively. Increased nitrogen (N) application of 21.2% resulted in a slightly increased corn grain yield of 5% in the 2011 FMS, but the simulated total N loss (through denitrification, volatilization, water, and sediment) increased to 49.3%. A better correlation was identified between crop N uptake and N application in the 2006 FMS (R = 0.60) than the 2011 FMS (R = 0.51), indicating that applied N was better utilized by crops in the 2006 FMS. Animal manure could create nutrient surpluses and lead to greater N loss, as identified in the regions of the Pacific and Southern Plains in the 2011 FMS. Manure nutrient management is important and urgently needed to protect our air and water quality. The IMMMS 1.0 is responsive to different FMSs and can be utilized to address alternative management scenarios to determine their impact when addressing the sustainability of food production and environmental issues.