Sensor‐Based Nitrogen Applications Out‐Performed Producer‐Chosen Rates for Corn in On‐Farm Demonstrations

TLDR

Optimal nitrogen rates for corn vary across fields, yet current practices ignore this variability, and crop‑reflectance sensors can diagnose N need at fine spatial scales. The study assessed whether sensor‑based variable‑rate nitrogen applications outperform producer‑chosen constant rates for corn. Fifty‑five replicated on‑farm demonstrations from 2004‑2008 used sensors mounted on producers’ equipment to direct sidedress N at V6‑V16, alongside a fixed producer‑chosen rate. Sensor‑guided applications raised partial profit by $42 ha⁻¹, increased yield by 110 kg ha⁻¹, cut N use by 16 kg ha⁻¹—about a 25 % reduction in excess N—confirming sensors outperform producer rates.

Abstract

Optimal N fertilizer rate for corn ( Zea mays L.) and other crops can vary substantially within and among fields. Current N management practices do not address this variability. Crop reflectance sensors offer the potential to diagnose crop N need and control N application rates at a fine spatial scale. Our objective was to evaluate the performance of sensor‐based variable‐rate N applications to corn, relative to constant N rates chosen by the producer. Fifty‐five replicated on‐farm demonstrations were conducted from 2004 to 2008. Sensors were installed on the producer's N application equipment and used to direct variable‐rate sidedress N applications to corn at growth stages ranging from V6 to V16. A fixed N rate chosen by the cooperating producer was also applied. Relative to the producer's N rate, sensors increased partial profit by $42 ha −1 ( P = 0.0007) and yield by 110 kg ha −1 ( P = 0.18) while reducing N use by 16 kg N ha −1 ( P = 0.015). This represents a reduction of approximately 25% in the amount of N applied beyond what was removed in the grain, thus reducing unused N that can move to water or air. Our results confirm that sensors can choose N rates for corn that perform better than rates chosen by producers.