Influence of Altering Sugarcane Harvesting Methods On Herbicide Fate and Transport.

Increased interest in the utilization of sugarcane biomass for bioenergy production has led to changes in harvesting methods in South Texas from traditional burning to mechanical green harvesting.  These harvesting changes coupled with current herbicide use in sugarcane production may lead to unanticipated changes in the chemical’s movement in soil in relation to the type of organic residues residing on the soil surface.  The herbicide atrazine (2-dichloro-4-ethylamino-6-isopropylamino-s-triazine) is used in the sugarcane industry and the objective of the study was to evaluate atrazine retention by sugarcane organic matter sources as dried (Green) leaf matter or burned (Ash) leaf residues and subsequent movement in a sandy loam soil.  The adsorptive capacity of atrazine to Ash (K_D=2006.6) residues was 100 times greater than Green (K_D=21.8) leaf residues.  Soil columns were packed with sandy loam soil with an additional 1% Ash vs Green organic matter.  After passing two pore volumes through soil columns, 73% of the atrazine leached out from the columns with Green residue added compared to only 3% leaching from the soil with Ash residue applied.  Results from this study suggest that prudent irrigation and soil management practices will be warranted to minimize atrazine movement undergoing green sugarcane harvesting practices.