On-farm testing of a dynamic model-based corn nitrogen management tool—Adapt-N—in Nebraska, USA

Abstract

Growers may be reluctant to adopt variable rate nitrogen (N) management because of concerns about the risk of yield loss. This study compares corn (Zea mays L.) N rate recommendations from Adapt-N, a dynamic soil-crop-weather model tool, with those provided by experienced grower research partners. Total N rate, yield, and partial factor productivity (PFP) were analyzed using data from on-farm trials conducted at nine locations in central-east Nebraska. The dataset was augmented with elevation, derived terrain attributes, and normalized difference vegetation index (NDVI) collected during the critical period for yield determination. To assess the impact of N management strategies, analyses were conducted at three scales: field-scale, across fields, and within-field productivity zones. A meta-analysis was performed to estimate the overall treatment effect among fields. Moreover, prescribed rates were compared with the agronomic optimum nitrogen rate (AONR). Results showed that in high-productivity zones, Adapt-N achieved higher yields at twice as many sites compared to grower-managed N applications while demonstrating higher PFP. Additionally, Adapt-N prescribed lower N rates in sites with lower elevation values and higher NDVI variability, suggesting that variable rate technologies can improve N management by responding to within-field variability. Despite these spatial differences, both strategies performed similarly in total N rate, yield, and PFP across fields. Both Adapt-N and Grower's had the ability to approximate the AONR with reasonable accuracy (RRMSE < 12%). Overall, the Adapt-N model offered good and similar-quality N rate recommendations to those used by experienced growers and research partners.