Joao Jose de Miranda Milagres1, Carlos Roberto Sant'Ana Filho1, Evandro Luiz Schoninger Sr.2, Andre Cesar Vitti3, Paulo C. Ocheuze Trivelin Sr.2 and Jose Albertino Bendassolli Sr.1, (1)Stable Isotope Laboratory, CENA, University of Sao Paulo, Piracicaba - SP, Brazil (2)Stable Isotope Laboratory, CENA, University of Sao Paulo, Piracicaba, Brazil (3)Agencia Paulista de Tecnologia dos Agronegocios, Secretaria de Agricultura e Abastecimento do Estado de Sao Paulo, Piracicaba - SP, Brazil
The 15N gas flux method can be used to determine the emission factor of N2O being unnecessary the inclusion of treatments without the application of fertilizer. In Brazil, the world’s largest sugarcane producer, it is common the use of vinasse (liquid waste from ethanol production) as organic fertilizer for the crop, and this practice can increase N2O emissions, because the vinasse is rich in carbon (C) and nitrogen (N). The aim of this study was to determine the emission factor of a sugarcane crop, ratoon cane, with or without the application of vinasse, using the 15N gas flux method. The study was conducted in São Paulo State, Brazil, using a randomized block design with a 2 x 2 factorial treatment containing four replicates and a total 16 plots with one 1.5-m long rows of sugarcane in 1.5m intervals. The factors corresponded to application or not of vinasse (100 m3 ha-1) in plots with two different levels of N (55 and 110 kg ha-1 as ammonium nitrate doubly labeled with 15N at 31.9 atom %). During 10 consecutive days, gas samples were taken from glass chambers (6 cm of diameter, 7 cm of height, 200 cm3) installed in the line of fertilization. The chambers were closed for 3 h (from 8 to 11 am) to allow N2O detection. The concentration and 15N content of N2O-N was determined by automated isotope ratio mass spectrometry (IRMS). Cumulatively, the highest emissions were observed for ratoon cane treated with vinasse. The emission factor ranged from 0.01 (without vinasse) to 0.35 % (with vinasse), both smaller than the 1% suggested by the Intergovernmental Panel on Climate Change. The 15N gas flux method allowed quantifying N2O emissions under field conditions, indicating a low emission factor for the cultivation of sugarcane, even using vinasse.