Revista Brasileira De Herbicidas 2010; 9(1): 1-8

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Weed management in sugarcane (Saccharum spp.) grown with break-backs operation aiming mechanized harvesting

DOI: 10.7824/rbh.v9i1.73

Mechanized harvesting has introduced some new factors in the cultivation of sugar cane which affect the dynamics of occurrence and weed control. One such factor is the operation of break-backs performed 60 to 90 days after planting in order to standardize the soil to work the machine harvester, but this operation causes damages to residual herbicides applied at planting. The present work was to evaluate the selectivity and performance of chemical weed control applied in two seasons: the planting of the crop and after the operation of break-backs. The experiment was carried out from November 2008 to June 2009, in the growing area of Vale do Parana distillery, Brazil, in plant-cane variety RB 92579, spaced 1.5 m between rows. The operation of break- backs was performed 70 days after planting. The experimental design was randomized blocks with 8 treatments and 4 replicates. The applications were performed in preemergence (at planting) and post-emergence of crop (after the break-backs), using a pressurized sprayer (CO2), with a bar equipped with four nozzles of the fan type, spaced at 0.5 m and a volume of 200 L ha-1. It was observed that treatment s-metolachlor (1920 g ha-1 at planting) and s-metolachlor + ametryn (1920 + 1500 g ha-1 after the break-backs) was effective in control of Brachiaria decumbens and Mimosa pudica, and was selective to plants of sugar cane. The treatment s-metolachlor (1920 g ha-1 at planting) and s-metolachlor + hexazinone+diuron (1920 + 900 g ha-1, after the break-backs) was effective in controlling B. decumbens and was selective to plants of sugar cane. The treatment s-metolachlor (1920 g ha-1 at planting) and s-metolachlor + amicarbazone (1920 + 1050 g ha-1, after the break-backs) was highly efficient in controlling B. decumbens and M. pudica, but had little selectivity to plant sugar cane. The treatment smetolachlor + ametryn (960 + 750 g ha-1 at planting) and s-metolachlor + ametryn (960 + 1500 g ha-1 after the break-backs) was effective in controlling M. pudica and was selective to the crop.