Impact of High Rates of Vinasse on Some Pertinent Soil Characteristics and on Sugarcane Yield in Mauritius

Abstract

Ethanol production from the available 150,000 tons of molasses by the sugarcane industry in Mauritius would generate annually some 400,000 tons of vinasse that will need to be disposed of in an environmentally sound manner. As large scale application of vinasse has been reported to impart both benefits and demerits and data under conditions prevailing in Mauritius are lacking, the impact of disposing 25–100 m3 ha−1 vinasse in sugarcane fields on soil quality and on sugarcane production was studied in field trials at four different agroclimatic regions. Results showed that vinasse did not negatively affect soil pH and salinity. It increased slightly the soil organic carbon as well as the exchangeable K. The results, moreover, provided evidence that high application rates of vinasse would not affect cane or sugar yield. On the contrary, the data obtained during the three year study, which covered a plant cane crop and two ratoons, have shown that vinasse gave a higher cane yield (average of 84.9 T ha−1) than mineral fertilizers alone (average of 77.3 T ha−1). As all the treatment plots received the same N level, this increase in cane yield may be attributed to a better K nutrition as well as to an improvement in soil organic matter status brought about by the vinasse. The present study provides evidence that the sustainability of the productive capacity of soils in Mauritius would not be affected by the application of large doses of vinasse.