Beta-testing the Adapt-N Tool in On-farm Strip Trials

Optimum nitrogen (N) fertilizer application rates for corn vary from year to year due to weather. Many current N rate recommendations do not account for this variability. Several major consulting services are beginning to offer services that address weather variability. The goal of this project was to validate a computer model-based tool that provides N fertilizer recommendations adjusted to the spring rainfall and temperature conditions of the current season. This model, Adapt-N, uses high-resolution weather data, and field-specific information on soil properties and soil and crop management. The objectives of this project were to validate the Adapt-N tool for on-farm use and promote greater grower adoption of Adapt-N as part of their tool kit for adaptive N management, focused on rate and timing of fertilizer application. The main hypothesis is that the Adapt-N tool provides more accurate estimates of the current season’s optimum N rate than conventional methods and tools.

From 2011 through 2014, averaged across 113 on-farm strip trials in Iowa and New York, relative to the grower's chosen rate, Adapt-N rates increased grower profits by US$26/A, and reduced losses of N by 25 lb/A, with no statistically significant difference in yields. At site-years with high spring rainfall, notably in 2013, profit gains of up to $120/A were realized through increased N rates that resulted in increased yields. Relative to grower practice, Adapt-N increased profit at 77% of the sites, and at only 14% did profit losses exceed $10/A. The Adapt-N tool is being further developed to accommodate the use of cover crops. These results have been accepted for publication in the Agronomy Journal. Some of the results have also been highlighted in Better Crops and in Case Study 7.4-4 of the IPNI 4R Plant Nutrition Manual.

This work serves as proof of concept for recent initiatives to offer crop modeling services to growers. Further efforts to improve the predictive power of the modeling tool are warranted. More widespread adoption of the adaptive weather-based N management approach can contribute to the improvement of N use efficiency in North American corn production. Additionally, the approach helps educate growers about the multiple pathways of N loss, and provides a quantification of environmental benefits. This project was completed in 2015. The Adapt-N tool was tested in Michigan in 2015 and 2016, in project USA-MI14.