Surface Water Quality as Affected by Sugarcane Residue Management Techniques.

Sugarcane production in Louisiana with its current residue management practices impacts both air and water quality. Since majority of Louisiana sugarcane acreage is located in watersheds that contain water bodies designated as impaired and are included on the EPA 303-d list for the state, devising means to reduce runoff of nutrients, sediments, organic residues and pesticides from sugarcane fields are necessary. This study evaluated the effects of three sugarcane residue management practices, namely ground burning of residue (BR), shredding of residue (SR), and full post-harvest retention of residue (RR) on the water quality of surface runoff over 2 growing seasons. About 24 runoff events were recorded over the study period. Runoff samples were analyzed for total suspended solids (TSS), turbidity, total dissolved solids (TDS), total Kjeldahl nitrogen (TKN), nitrate-N, nitrite-N, chloride, bromide, sulphate, total phosphorus (TP), and biological oxygen demand (BOD₅) using approved EPA analytical methods. Rainfall amount explained about 47-69% (P < 0.001) of the variability associated with TSS, BOD₅, TKN, TP, and the inorganic anions, particularly in the BR and RR techniques. A highly significant relationship existed between TSS and Turbidity measurement (R² = 0.95, P < 0.001).  Total P in runoff samples was well correlated with TSS (R² = 0.80, P < 0.001), and turbidity (R² = 0.79, P < 0.001). In summary, the results indicated no significant effects of these management techniques on surface water quality. However, the RR techniques comparatively reflected lower TSS, BOD₅, TP and inorganic anions export during the study period. This was chiefly attributed to the lower sediment output exhibited by this management technique.