IRRIGATION AND NITROGEN MANAGEMENT FOR SPRINKLER-IRRIGATED CABBAGE ONSAND

Six field studies were conducted from 1980-88 to evaluate the response of cabbage (Brassica oleracea L., Capitata group) to sprinkler irriga tion and sprinkler-applied N fertilizer on a coarse-textured soil. The plots were irrigated using a modified self-moving lateral sprinkler i rrigation system that applied rive levels of water and rive levels of N (liquid NH4NO3) in specified combinations of central composite rotat able design. Cabbage yields were significantly increased by water and N applications in all experiments. The N rates predicted for maximum y ield exceeded typical cabbage N fertilizer recommendations. However, t he above-average plant populations used in these studies resulted in a bove-average yields and plant N accumulation. Deficit and excess irrig ation produced negative results. Generally, cabbage production was opt imized and N losses to the environment were minimized when crops were irrigated for evapotranspiration (ET) replacement However, even when i rrigated for ET replacement, these data demonstrate the potential for N leaching at high N rates, presumably as a result of rainfall.