Nitrogen-Enriched Vinasse as a Means of Supplying Nitrogen to Sugarcane Fields: Testing the Effectiveness of N Source and Application Rate

Vinasse is a by-product generated during the distillation phase of ethanol production. Vinasse can be concentrated and enriched with N to be used as a means of supplying nitrogen (N) to sugarcane fields. However, it remains necessary to ascertain the most effective N source and application rate to be mixed with concentrated vinasse (CV) in order to maximize crop productivity. In this study, we aimed to address three major questions: (i) which is the best combination of N source [urea or uran (urea+ammonium nitrate)] and application rate (0, 40, 80 or 120kgha(-1) of N) to mix with CV; (ii) can the addition of acid fertilizers (boric acid and phosphoric acid) to CV reduce the volatilization of NH3 and/or increase sugarcane yield; and (iii) is there a correlation between the N-NH3 volatilization loss and the sugarcane yield. We conducted a sugarcane field trial to coincide with the second ratoon during the dry season. Applying N-enriched CV to sugarcane straw yielded only nominal NH3 losses. This outcome was attributed to a deficit in the water supply which limited urea hydrolysis and ammonia formation during the dry season. The addition of acid fertilizers (boric acid and phosphoric acid) was able to further reduce volatilization losses. Both, urea and uran appear to be feasible N sources for the enrichment of CV as they did not differ in their degree of accumulated NH3 volatilization. In terms of crop productivity, however, the use of uran appears to equate to greater sugarcane yield and leaf N content. The N rate of 80kgha(-1) provides lower accumulated NH3 volatilization along with a higher sugarcane yield reflected in the correlation with productivity parameters. Our results suggested that application of CV enrichedwith Noffers a promising means of improvingsugarcane yield.