Perdas gasosas de nitrogênio de vinhaça e uréia em solos cultivados com cana-de-açúcar

Gaseous losses of nitrogen from vinasse and urea application to clay textured Latosol and sandy textured Podzol were evaluated in laboratory at the Centro de Energia Nuclear na Agricultura/Universidade de Sao Paulo (CENA/USP), Piracicaba, State of Sao Paulo, Brazil, in 1990. Acidulated extracts containing volatilized nitrogen from soils incubated during 17 days with the 15 N labelled sources (urea and vinasse) were obtained from a forced draft system. The origin of the lost nitrogen (urea-N, vinasse-N and soil-N) and the nature (volatile organic-N and volatilized NH 3 -N) of the applied sources were determined in these extracts. The soil 15 N-balance at the end of the experiment allowed the estimation of total losses of the sources. In relation to urea source, the gaseous losses of applied N were estimated as 11.2 and 16.0% in Latosol and 17.5 and 26.4% in Podzol, when it was applied once and complemented to vinasse, respectively. The gaseous losses of vinasse-N were 56.8 and 12.7% in the Latosol and Podzol, respectively, when the soils were treated with vinasse complemented with urea. The results also showed that losses from both sources were only of ammoniacal nature. Greater volatilized-N losses from applied vinasses to clay soils, would explain larger productivity responses of ratoon sugar-cane in these kind of soils, when vinasse is complemented with fertilizer-N