Nitrogen Fertilization Of Irrigated Corn In A High Residual Soil N Environment In The Arkansas River V

High levels of residual soil N03-N are present in the soils in the Arkansas River Valley where melons and other vegetable crops are produced. The amount of N fertilizer required to optimize the yield potential of crops, such as corn, following vegetables needs to evaluated to reduce N03-N leaching potential in the Valley where high N03-N levels have been reported in the ground water. This study evaluated the effects of N fertilizer rate (0, 50, 100, 150, 200, and 250 lb N/a) and N source (urea and Polyon®3) on corn yields following 5 years of alfalfa and one year of watermelon production. Corn grain yields were not increased by N fertilization in 2000 and were not influenced by N source. Corn plant stands were reduced by urea broadcast, incorporated application rates above 150 lb N/a in 2000, but were maintained when Polyon® was used. Silage yields increased with increasing N rate up to about 150 lb N/a, then decreased with increasing N rate. Soil residual N03-N levels increased with increasing N rate in 2000. In 2001, corn grain and silage yields did not increase with increasing residual soil N03-N levels (no N fertilizer applied). Based on this study, it appears that a minimal amount «50 lb N/a) of N fertilizer needs to be applied to corn to maintain grain and silage yields in the Valley in rotations with a vegetable crop like watermelon. Fertilizer N appears to be moving out of the root zone with downward movement of irrigation water.