Nitrogen balance is affected by application time and nitrogen fertilizer rate in irrigated no-tillage maize in Argentina

HERNÁN R. SAINZ ROZAS, HERNÁN E. ECHEVERRÍA PABLO A. BARBIERI.

AGRONOMY JOURNAL

ASA

Lugar: Madison,Wi; Año: 2004 p. 1622 - 1631

0002-1962

High N requirements of no-tillage (NT) maize makes it imperative that we develop management strategies that optimize crop production and N use efficiency (NUE) and decrease environmental pollution. A 4-year field experiment was conducted at Balcarce, Argentina (37° 45´ S, 58° 18´ W), on a soil complex of a fine, mixed, thermic Typic Argiudoll and a fine, illitic, thermic Petrocalcic Paleudoll. The objective was to evaluate the effect of urea rate (0, 70, 140 and 180 kg N ha-1) at planting (FPL) or V6 vegetative growth stage (FV6) on NH3 volatilization (VL) and denitrification losses (DL), residual nitrate in the soil (RN), N in the soil microbial biomass (NMB), maize N uptake and unaccounted N (UN). Fertilizer N uptake at physiological maturity was 168 and 192 kg N ha-1 (average of N rates) for FV6 and FPL, respectively. Gaseous N losses ranged from 7.6 to 13.8% of applied N and were not affected by the time of N fertilizer application. However, DL and VL were of a similar magnitude for the FPL treatment, while VL was larger for the FV6 than FPL. Relative to unfertilized control, fertilized treatments increased NMB (13.4 kg N ha-1) similarly for both fertilization times. The RN was increased by larger N rates applied at V6. For the FPL time UN was 55, 69, 86 and 103 kg N ha-1, for the 0, 70, 140 and 210 kg N ha-1 rates, respectively. The losses were attributed to nitrate (NO3) leaching. High fertilizer NUE in combination with economically competitive grain yields can be obtained when N is applied at the V6 growth stage because gaseous N losses are low (less than 11%) and NO3 leaching is significantly reduced. Key word: N balance-fertilization times-maize-no-tillage.