Field Evaluation of Concentrated Molasses Stillage as a Nutrient Source for Sugarcane in Swaziland

Stillage or vinasse, which is a byproduct of ethanol production, is produced from the fermentation of molasses and is used as a source of potassium on cane fields at Simunye-Royal Swaziland Sugar Corporation. Due concern regarding its high salt content and Chemical Oxygen Demand (COD), a trial was established on an S set soil (Mayo form) to study the effect of increasing levels of concentrated molasses stillage (CMS) on cane and sucrose yield, recovery of ash in the mill and the impact of CMS on soil quality and the environment. The results of two crop harvests indicated no significant differences in cane and sugar yields when the K source was either muriate of potash or CMS, provided the recommended amount of K was adhered to. The low CMS treatment of 3 t/ha banded on the row initially produced the highest sucrose yield and this provided approximately 160 kg/ha K. Doubling the CMS rate to 6t/ha impacted negatively on cane growth and sucrose yield but no evidence of salt accumulation or pH change was found. The results suggested that the application of CMS at the recommended rate to supply K, would maintain sugar productivity and soil fertility and cause no environmental contamination.