EFFECT OF UREA WITH NUTRISPHERE-N POLYMER IN FALL AND SPRING NITROGEN APPLICATIONS FOR CORN

Polymer coated urea may be a viable option to improve Nitrogen (N) uptake and corn (Zea mays L.) grain yields, especially in areas with relatively high soil N loss. The objective of this study was to evaluate the effect of two urea application timings (fall and spring) and three N rates (90, 180 and 270 kg N ha^-1) with and without Nutrisphere-N polymer on irrigated corn near Scandia, KS from 2006 to 2008. Compared to uncoated N, urea coated with Nutrisphere-N improved grain yields by 18.3% with applications of 180 kg N ha^-1 in the fall. Application of urea with Nutrisphere-N in the spring produced similar grain yields for treatments with and without Nutrisphere-N. Corn ear-leaf content was highest with urea applied at 90 kg N ha^-1 in the fall and urea coated with Nutrisphere-N at 180 and 240 kg N ha^-1 in the fall and spring. Grain N content was highest from urea coated with Nutrisphere-N application at 270 kg N ha^-1 in the fall and spring. Compared to untreated urea, Nutrisphere-N improved grain N removal by 29.6% at 180 kg N ha^-1 applied in the fall. Spring urea application with Nutrisphere-N produced similar grain N removal compared to urea without Nutrisphere-N. Generally, adding Nutrisphere-N to urea fertilizer may help improve N content in leaves and grain and increase grain yields of corn, especially with the fall N applications having higher potential of soil N loss.