Sugarcane Crop Residue Decomposition, Organic Matter Accumulation and N Mineralization In Florida Sandy Entisol.

Sugarcane (Saccharum spp.) is a biomass-producing crop that requires considerable input of water and nutrients, especially nitrogen (N) for maximum yields. There is worldwide pressure on sugarcane industries to adopt “green cane” harvesting systems that do not involve burning. A two-year field experiment was conducted in 2006 and 2007 to determine how selected crop residue management systems affect organic matter (OM) accumulation and N mineralization after two selected harvest dates. Treatments included 1) pre-harvest burn, 2) harvest green+disking between rows and 3) harvest green + no till. These treatments were implemented in Hendry County, FL on a sandy Entisol, Treatments were arranged in spit- plot design with time of harvest as main plots and residue management system as the subplots. Tissue, residue and soil samples were collected periodically. Soil samples were collected monthly at three selected depths (0-15, 15-30 and 30-45 cm) and analyzed for ammonium (NH₄-N), nitrate (NO₃-N) and OM contents. The Objectives of this study were to: 1) Quantify the rate of residue decomposition and nutrient release on sandy soils after green cane harvest, and 2) Compute N mineralization and nitrifications rates in the soil. Plant data indicated that there was no significant effect of residue management system on plant NPK content for all harvest. Analysis of crop residue for both harvest dates were not significantly different for N and P content by sample date while the effect on residue K content was significant. Soil analysis for all harvest dates suggest that there was no significant effect of treatment on OM, and NH₄-N content but were significantly different for NO₃-N content. Results of this experiment indicate that decomposition of crop residue had no affect on OM and NH₄-N accumulation but did contribute to greater soil NO₃-N concentration compared with current pre-harvest residue burning.