Nitrogen is the plant nutrient required in the largest quantity, the most likely to be deficient, and the most impactful on corn yield as well as grower profit. Providing N to a corn crop in the right amount while minimizing loss is difficult because of complex biological and chemical reactions that result in the loss of N from the crop root zone via deep percolation to ground water, lateral flow, runoff and erosion to surface waters, and volatile losses to the atmosphere as ammonia, nitrogen gas, nitric oxide, nitrous oxide, etc. Increasing crop utilization of N and reducing loss of N outside the field is important to the sustainability of corn production in the Corn Belt.

Optimizing the rate of fertilizer N based on profit is one approach to reducing fertilizer N loss from corn production systems. Nitrogen rate recommendations for most Corn Belt states are based on the aggregation of results from numerous N response trials and a simple economic analysis that considers the value of grain and the cost of N. This approach is commonly referred to as MRTN – Maximum Return to Nitrogen (Sawyer et al., 2006). Nitrogen recommendations from this approach “should provide an N rate that reflects economic value and probability of achieving expected economic return across a range of locations and period of time”. The recommendations are general in nature and therefore not responsive to variations in seasonal weather.

Adapt-N is a mechanistic model that utilizes several soil and management parameters, anticipated yield, and actual and historic weather to provide a field- and season-specific N recommendation that is purported to be more accurate than the general recommendation given by the MRTN approach (http://adapt-n.cals.cornell.edu/manual/index.html).

This project compared the accuracy and profitability of N recommendations from MRTN and Adapt-N in Iowa, Indiana, and Wisconsin.