Sugarcane response to mill mud, fertilizer, and soybean nutrient sources on a sandy soil
Improving soil organic matter and soil fertility are important factors in the sustainability of sugarcane (Saccharum spp.) production. A 3-yr field trial was established in 2004 on a sandy Alfisol in Florida to compare the effect of organic and inorganic nutrient sources on sugarcane production. The three nutrient sources were (i) mill mud (filter cake, cachaza), (ii) local standard fertilizer, and (iii) soybean cropping system before sugarcane. Soybean green manure increased sucrose yield (TSH, t sucrose ha–1) 20% in plant cane, however when aboveground biomass was removed soybean rotation did not improve sugarcane yields. Fertilization did not increase yields if mill mud was added to plant cane. Soybean green manure did not improve sugarcane ratoon crop yields, and there were no significant interactions in the ratoon crops. The application of mill mud resulted in a 49% TSH increase in first ratoon and a 167% increase in second ratoon whereas inorganic fertilizer application increased TSH by 31 and 49% in first and second ratoon, respectively. Over the 3-yr crop cycle, addition of mill mud alone led to an increase of 4.1 TSH compared with inorganic fertilizer alone, whereas soybean green manure alone produced 2.6 TSH less than fertilizer. However, combinations of nutrient sources with mill mud had additive effects in the ratoon crops. Our results indicate that mill mud was more effective than soybean green manure or local standard fertilizer practices in increasing sugarcane yields on sand. However, growers should fertilize ratoon crops when mill mud has been applied to achieve maximum sugarcane yields.