Abstract

Improving the strategy of nitrogen fertilization in agroecosystems through the use of coated fertilizers and the definition of critical periods of the crop when N deficiency is detrimental, are alternatives that can be integrated to optimize the production of the wheat crop and reduce the losses of Nitrogen (N) in the system. The objective of this work was to evaluate the effect of a coated urea fertilizer of slow release on the production of aerial vegetable biomass of wheat, the concentration of N in the aerial biomass and the content of mineral N in an Andisol, Valdivia agroecosystem. The treatments consisted of two ammonia fertilizers, commercial Urea and Urea-Nutrisphere, four doses of N fertilization (100, 200, 250 and 300 kg ha-1) and three application strategies, sowing (S), partialization (P), and tiller (M), evaluated in two seasons (late sowing, 2015-2016 and early sowing, 2016-2017). It includes a control with cultivation without fertilization and plots without crop to evaluate the mineralization of N in the field. The experimental design was complete random blocks. The samples of aerial biomass and soil (20 cm deep) were collected in five growth stages (Z21, Z31, Z39, Z45, Z69 on the Zadoks scale). The variability in the production of aerial biomass in the wheat until to the phenological stage of Antesis (Z69) under conditions of the Valdivia agroecosystem, depends on the moment of application of ammoniacal fertilizer, the dose used and the date of sowing. There were no significant differences in biomass production when comparing the fertilizers evaluated between the treatments in each season. Concentrations of N in the aerial biomass below the critical level (Nc = 5.3W-0.44, Justes et al., 1994) occurs in the early stages of cultivation (Z21 and Z31), given by the amount of fertilizer applied and the strategies of application of N. In conditions of growth in the Valdivia agroecosystem, the use of coated urea does not increase the production nor the concentration of N in the aerial biomass, in comparison with uncoated urea fertilizers. However, higher content of mineral N from coated fertilizer was determined than uncoated urea in the first 20 cm of depth in an Andisol during the season of wheat growth evaluated under field conditions