Surface and Subsurface Phosphorus Losses from Sugarcane Fields with Different Management Practices

Phosphorus losses in runoff from sugarcane fields can contribute to non-point source pollution of surface and subsurface waters. The objective of this study was to evaluate the effects of three different management practices on P losses in surface runoff and subsurface leaching from sugarcane (Saccharum officinarum L.) fields. Field experiments with treatments including conventional burning (CB), compost application with burning (COMB), and remaining green cane trash blanketing (GCTB) treatments were carried out to assess these management practice effects on P losses from sugarcane fields. In the CB treatment, sugarcane residue was burned after harvest. The COMB treatment consisted of compost applied at “off bar” with sugarcane residue burned immediately after harvest. Compost was applied in the amount of 13.4 Mg ha−1 annually, 8 weeks before planting. In the GCTB treatment, sugarcane residue was raked off from the row tops and remained in the wheel furrow after harvest. Surface runoff was collected with automatic refrigerated samplers, and subsurface leachate was collected with pan lysimeters over a period of 3 years. Measured concentrations of total P (TP), dissolved reactive P (DRP), and particulate P (PP) in surface runoff from the COMB treatment were significantly higher than concentrations from the CB and GCTB treatments. The mean losses of P (TP and DRP) after burning (postharvest, years 2 and 3) were significantly greater than the no-burn treatment (preharvest, year 1) in the CB, COMB, and CB/COMB/GCTB combined options. Additionally, the mean losses of total suspended solid and total combustible solids in residue burning were, on average, 2.7 and 2.2 times higher than the no-burn practices, respectively (preharvest and GCTB treatment). Annual P losses from surface runoff in the third year of study were 12.90%, 6.86%, and 10.23% of applied P in CB, COMB, and GCTB treatments, respectively. However, the percent of annual DRP losses from applied P in COMB and GCTB treatments was similar magnitude, and their values were less than 50% compared to the value from CB treatment. In the leaching study, percent of monthly mean TP and DRP losses in the COMB and GCTB treatments were greatly reduced. Based on these results, the COMB and GCTB procedures were equally recommended as sugarcane management practices that improve water quality in both surface runoff and subsurface leachate.