GROWTH, YIELD, AND QUALITY OF FORAGE MAIZE UNDER DIFFERENT NITROGEN MANAGEMENT-PRACTICES

Maize (Zea mays L.) forage producers need more information on how N management affects dry matter (DM) yield, forage quality, and residual soil NO3--N concentrations. Studies were conducted in New York to evaluate three hybrids under different sidedress N rates (0, 56, 140, and 255 kg N ha-1 at the V4 stage) and timing (70 + 70 kg N ha-1 at V4 and V8 and 75 + 75 + 75 kg N ha-1 at V4, V8, and R1 stages). The DM yields, which averaged 25% lower in 1991 (12.3 Mg ha-1) compared to 1990 (16.9 Mg ha-1), responded curvilinearly to N rates with maximum economic yields of 140 and 160 kg N ha-1, respectively. Whole-plant neutral detergent fiber (NDF), acid detergent fiber (ADF), and N concentrations responded linearly to N rates in 1990 indicating that forage quality improved with each additional increment of N. Higher N rates, however, increased residual soil NO3--N concentrations in the upper 0.3 m soil depth in 1990 (0, 3, 30, and 32 mg kg-1) and 1991 (0, 0, 17, and 17 mg kg-1 for the 0, 56, 140, and 225 kg N treatments, respectively). Split-N applications compared to respective single rate N applications did not increase DM yields, improve forage quality, or decrease residual soil NO3--N concentrations. When applying higher rates of N fertilizer, maize forage producers must balance potential benefits of higher DM yields and improved forage quality with the potential risk of increased residual soil NO3--N concentrations.