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.