Evaluation of in-season Nitrogen management strategies for corn production
Nitrogen is an important and costly input for corn (Zea mays L.) production. With rising prices and environmental concerns, producers are looking for ways to better manage N fertilization. A project designed to evaluate in-season N management strategies for adjusting N rate was conducted in 30 Iowa cornfields from 2004 to 2006. Nitrogen rates applied preplant or early sidedress (PRE-N) and corn plant sensing with a chlorophyll meter (CM) to detect N stress was used to determine as-needed in-season post sensing nitrogen application (POST-N). Field-length strips were replicated three times with six N treatments: zero-N control, 67 kg N ha–1 (reduced PRE-N rate), 67+ (reduced PRE-N rate plus POST-N), 134 kg N ha–1 (agronomic PRE-N rate), 134+ (agronomic PRE-N rate plus POST-N), and 268 kg N ha–1 (PRE-N non-N limiting reference rate). Nitrogen deficiency stress sensing was partially successful, with 70 to 80% correct N deficiency detection. Mean yield increased 0.5 Mg ha–1 across all sites with the POST-N applied to the 67 kg N ha–1 PRE-N rate. The 67+ POST-N strategy had a similar total N applied as the agronomic 134 kg N ha–1 PRE-N rate, but the yield was 0.5 Mg ha–1 lower. This indicates yield potential loss and poor recovery from the POST-N applications. Economic return comparisons indicated that the agronomic 134 PRE-N rate and 134+ POST-N in-season strategy were similar and had higher return than the 67+ POST-N strategy. The agronomic PRE-N rate, with confirmation of N stress and determination of additional N need through plant sensing, was a more cost effective in-season strategy than starting with the reduced PRE-N rate.