Nitrogen application decision-making under climate risk in the U.S. Corn Belt

Abstract Nitrogen fertilizer is one of the most important inputs to corn production and farmers manage their crop by deciding how much to apply, when to apply it and how to apply it to maximize their yields and resulting profit. There is risk inherent in crop fertility management because once nitrogen is applied to the soil it is no longer immobile and cropland is subject to loss of this costly input under different weather conditions. Days suitable for field work, a farm’s machinery set, and weather conditions determine when field preparation and planting activities are completed each year. This paper documents the methods and data used to evaluate the economic costs and benefits of the agronomic practice of “splitting” nitrogen fertilizer—applying some at or just before planting and a second application after the plant has already emerged and is in greatest need of nutrients. An example of how to use the free online decision support tool Corn Split N DST (splitn.agclimate4u.org) to evaluate the climate risk and economics of post-planting N applications is developed to illustrate the application of methods described.