Emissão de óxido nitroso e produtividade do girassol sob diferentes fontes de adubação nitrogenada

Abstract

The sunflower crop stands as one of oilseeds with high potential for use as a source of feedstock for biodiesel production in Brazil. However, there is a lack of studies with the use of organic fertilizer sources to evaluate the fertilizer efficiency and the effect of these in emissions of greenhouse gases, especially nitrous oxide (N2O), in sunflower crops in Brazil. In this context, the aim of this study was to evaluate the effect of sources of organic fertilization on N supply, the grain yield and N2O emissions in the cultivation of sunflower in system tillage. The experiment was carried out in the years 2011/12 and 2012/13 on a Paleudalf. The treatments applied on sunflower were: mineral fertilizer (NPK), poultry litter (CF); pig deep litter (CS), and control without nitrogen fertilization. The application of organic fertilizers increased N accumulation and yield of sunflower, presenting results similar to mineral fertilization. However, N2O emissions increased with application of organic and mineral fertilizers, especially in the first 40 days evaluation. The largest cumulative emissions of N2O-N, in average of the two crops were observed in treatments with organic manure, ranging from 3.1 (CS) to 3.85 (CF) N-N2O kg ha-1. The accumulated emission of N2O-N observed in CS and CF treatments was, respectively, 76 and 70% for first crop and 55 and 53% higher than accumulated emission control treatment without N application in second crop. At the end of two years of cultivation the average emission factor of N2O in the treatments with application of organic fertilizers ranged from 0.87% of applied N with pig deep litter to 1.18% of N applied with poultry litter. The average emission factors obtained in this study, according to the methodology IPCC, for treatments with organic fertilization are close to the default value 1%. For mineral fertilizer the emission factor obtained was lower than indicated by the IPCC. Thus, treatments with organic fertilization had greatest potential N2O emission in relation to mineral fertilization. On the other hand, the results of this study show that the CF and CS have potential N supply similar to mineral fertilization and indicate that these residues can replace the organic mineral N fertilization in the cultivation of sunflower in no-tillage.