Effects of Long-Term Nitrogen Management on Nitrogen Budgets of Irrigated No-till Corn.

Effects of nitrogen management on irrigated no-till (NT) corn (Zea Mays L) yields were studied from the 1999 to 2015 growing seasons in a Fort Collins clay loam soil at the CSU ARDEC near Fort Collins, CO.  The NT N fertilizer rates averaged 0, 34, 67, 134, 202 and 246 kg N ha^-1. Fifteen corn plants were collected at 146 days after planting (DAP) to determine corn grain, cob, stalk and total aboveground biomass. Harvest grain yields were determined by harvesting 15 m of row at 173 DAP. We measured N uptake in the aboveground plant compartments and in the 0 – 1.5 m soil profile. Nitrogen fertilizer inputs increased soil organic N (P<.001) and reduced N use efficiencies (P<.001). A nitrogen budget will be presented for this corn-corn rotation and assessment of the losses of N and pathways for these losses will be presented.