Herbicide retention as affected by sugarcane mulch residue

The purpose of this study was to evaluate the effectiveness of sugarcane residue (mulch cover) in reducing non-point source contamination of applied chemicals from sugarcane fields. For this purpose, two main treatments were investigated: (1) a no-till treatment (100% mulch), and (2) a burn treatment prior to harvest using a combine harvester. The effect of mulch residue on herbicide retention was quantified following pre-emergence as well as layby applications. The amounts of extractable atrazine, metribuzin, and pendimethalin from the mulch residue and the surface soil layer were quantified during 1999 and 2000 growing seasons. Significant amounts of applied herbicides were retained by the mulch residue. Extractable concentrations were an order of magnitude higher for the surface mulch compared with that retained by the soil matrix. Results from a laboratory study of the retention kinetics of the mulch residue were consistent with field measurements. A distribution coefficient (K-d) for mulch residue (23.40 cm(3)/g) was an order of magnitude higher than that for a Commerce soil (2.352 cm(3)/g).