No-till maize nitrogen uptake and yield: Effect of urease inhibitor and application time

No-tillage affects maize (Zea mays L) fertilizer Fi use efficiency when ure a is surface-applied, due to NH3 volatilization, A 3-year field experiment was conducted at Balcarce, Argentina (37 degrees 45' S, 58 degrees 18' W), on a soil complex of a fine, mixed, thermic Typic Argiudoll and a fine, ill itic, thermic Petrocalcic Paleudoll, The objective was to evaluate the effe ct of surface-applied urea rate (0, 35, 70, 140, and 210 kg N ha(-1)), with and without a urease inhibitor [N-(n-butyl) thiophosphoric triamide] (nBTP T) at different times (planting; six-leaf stage, V6) on NH3 volatilization losses, soil mineral N, and maize N uptake and grain yield under no-tillage , A semiopen static system was used to monitor NH3 volatilization losses. A mmonia N losses from urea without nBTPT ranged between 2.6 and 13.3% of app lied N, being greater with higher N rates and when the urea was applied at V6. Volatilization losses with nBTPT were not different than those from the control, The use of nBTPT did not increase soil mineral N consistently and did not increase N uptake nor grain yield. Relative to fertilization at pl anting, fertilization at V6 increased sail mineral S at flowering, N uptake at physiological maturity (167 and 155 kg ha(-1), respectively), and grain yield (11 003 and 10 440 kg ha(-1), respectively), For slightly acid and h igh organic matter soils, the use of nBTPT did not improve urea N use effic iency. Delayed urea application had a greater and more consistent effect th an the use of nBTPT on the increase of no-till maize grain yield and N use efficiency.