EVALUATION OF NITROGEN APPLICATION METHODS AND RATES WITH NUTRISPHERE-N ON SOIL NITRATE-NITROGEN IN SOUTHEASTERN COASTAL PLAINS

Nitrogen (N) application with Nutrisphere-N polymer may affect soil Nitrate-Nitrogen (NO₃-N) movement in the soil. The objective was to evaluate two N application methods (all at planting and split application) and five N rates (0, 45, 90, 135 and 180 kg N ha^-1) with Nutrisphere-N polymer on soil NO₃-N in dryland corn (Zea mays L.) near Blackville, SC from 2010 to 2012. Soil samples were collected from the soil depth of 90 cm and divided into 15 cm increments following corn harvest. Compared to uncoated fertilizer, Nutrisphere-N improved NO₃-N concentration by 29.8% with 180 kg N ha^-1 in split applications at 0-15 cm depth and by 44.7% at 90 kg N ha^-1 applied at planting at 15-30 cm depth. Soil NO₃-N content increased with Nutrisphere-N by 26.2, 36.1, 28.0 and 17.3% at 45 kg, 90 kg, 135 kg and 180 kg N ha^-1 in split applications at 15-30 cm depth, respectively. Nutrisphere-N improved soil NO₃-N concentration by 40.1 and 31.6% at 90 kg and 135 kg ha^-1 over uncoated treatment for N applied in split applications at 30-45 cm depth, respectively. Soil NO₃-N content improved with Nutrisphere-N by 36.9% at 135 kg N ha^-1 applied at planting, while NO₃-N concentration improved by 33.9 and 34.9% at 135 kg and 180 kg N ha^-1 with Nutrisphere-N applied in split applications at 45-60 cm depth, respectively. At 60-75 cm depth, Nutrisphere-N decreased soil NO₃-N content by 22.0% at 180 kg N ha^-1 applied at planting and increased content by 37.5 and 59.9% with split N applications of 90 kg and 135 kg ha^-1, respectively. Soil NO₃-N concentration increased with Nutrisphere-N by 30.6% over untreated fertilizer at 135 kg N ha^-1 in split applications at 75-90 cm depth. Generally, N applications with Nutrisphere-N helped to reduce soil NO₃-N losses.