Selectivity and effectiveness of herbicides in the grain sorghum crop

Abstract

Over the years, cultivated areas of sorghum have expanded considerably in Brazil. Chemical weed control has become an obstacle due to the scarcity of herbicides registered for the crop. The aim of this study was to evaluate the efficiency of weed control and selectivity of herbicides applied in pre and post emergence in the crop. Two experiments were conducted. In one of them, the hybrid BRS 310 was used while DKB 550 was used in the other. The experiments were performed in the field in randomized block design, evaluating seven treatments with four replications. The used treatments were: 1. Hand weeding, 2. S-metolachlor (1,440 g a.i. ha-1), 3. S-metolachlor (1,440 g a.i. ha-1) + atrazine (2,000 g a.i. ha-1), 4. atrazine (2,000 g a.i. ha-1), 5. atrazine (3,000 g a.i. ha-1), 6. atrazine (2,000 g a.i. ha-1) + mineral oil (0.25%), and 7. atrazine (2,000 g a.i. ha-1) + mineral oil (0.5%). It was verified that post-emergence atrazine was efficient in the weed control and selective to the sorghum crop, not affecting productivity, except in mixture with mineral oil (0.5%). Smetolachlor cannot be recommended in pre-emergence for the tested cultivars because it is not selective, reducing plants and productivity