Farmer Motivations for Excess Nitrogen Use in the U.S. Corn Belt

Improving the use efficiency of nitrogen fertilizer is one of the most effective ways to mitigate agriculture's contributions to climate change and water-quality degradation. However, studies suggest that many farmers worldwide are exceeding annual-profitable nitrogen rates and thus "overapplying" nitrogen. This paper utilizes a case study to understand overapplication at the individual level, focusing on (1) prevalence and severity of overapplication as defined by maximum profitable thresholds and (2) gaining an understanding of what factors limit overapplying farmers' desire and capacity to lower their rates. Using a sample of 132 interviews with row-crop farmers in three states in the Midwestern United States, I find that 37% of interviewed farmers overapplied nitrogen by 5 lbs./ acre or more, with few farmers adjusting rates annually and the largest farmers being most likely to overapply. When asked what prevented them from reducing their rates, overapplying farmers felt their current rates were appropriate or profitable, and thus, they did not desire to reduce them. Of these farmers, some assumed they could not be overapplying, some used more N to achieve maximized production, while others intentionally overapplied as a risk-mitigation strategy. I conclude by offering recommendations for policy and future research to build on this case study.