Nitrogen Uptake By Corn Under Different Fertilizer, Irrigation and Tillage Management.

Loss of nitrogen (N) from fertilized land has economic as well as environmental implications. In corollary, N and soil management practices that improve crop N uptake will positively affect economic profit and cause less harm to environment. Three different studies at different locations were conducted to evaluate crop N uptake under different N sources and placement, irrigation and tillage systems in corn production. At location 1 (loamy sand), split-applied urea (split-U), polymer-coated urea (PCU), and urea with inhibitors (IU) were evaluated under irrigated and non-irrigated systems. At location 2 (silt loam), anhydrous ammonia (AA) applied at two different depths were evaluated under conventional tillage (CT) and no-till (NT). At location 3 (silt loam), urea, PCU, and IU were evaluated under two different placement (broadcast incorporation; BI and mid-row subsurface banding; MRB). Total above-ground N uptake was estimated by summing up N uptake by above-ground biomass (grain, cob and stover). Nitrogen fertilizer recovery efficiency (NFRE) was calculated by subtracting the total aboveground N uptake in the control treatment (N = 0) from that in each N treatment and expressing the result as a percentage of the total fertilizer N applied. At location 1, irrigation increased total above-ground N uptake and NFRE differed by N sources (split-U > PCU = IU). At location 2, total above-ground N uptake was greater in CT than in NT at P = 0.16 but did not differ by depth of AA application. At location 3, above-ground N uptake and NFRE did not differ by N sources or placement.  This summary report of three studies suggest a need to consider different management practices such as irrigation and tillage that may affect performance of different N sources in improving crop N uptake.