Períodos de interferência de plantas daninhas e seletividade a herbicidas em canola, niger e cártamo

Abstract

The aim with this work was determine the periods of weed interference and effect of competition on productivity, and evaluate the selectivity of herbicides in the pre-emergence in rapeseed, niger and safflower. The experiments were in 2014 and 2015, at the Experimental Farm of the Federal University of Grande Dourados, in Dourados, MS. The periods of control and coexistence periods after the emergence of were studied 14 days after emergence until the end of their cycles. To test the selectivity were applied in the pre-emergence of the crops the herbicides: S-metolachlor (0.6 and 1.2 kg ha-1), pendimethalin (0.75 and 1.5 kg ha-1), clomazone (0.375 and 0.75 kg ha-1), and sulfentrazone (0.3 and 0.6 kg ha-1). Visual evaluations of phytotoxicity were performed at 7, 14, 21 and 28 days after emergence of the crops. The herbicides that did not have a significant effect were considered selective. It was concluded that the weed competition caused a reduction of up to 88% in safflower production, up to 58.7% for rapeseed and up to 56% for niger. It is necessary to control them between 4 to 59 DAE, from 5 to 38 DAE and from 6 to 45 DAE for each culture respectively. S-metolachlor treatments (0.576 and 1.2 kg ha-1) were selective to all evaluated cultures; pendimethalin (0.75 and 1.5 kg ha-1) for rapeseed and safflower, and 0.75 kg ha-1 for niger; sulfentrazone (0.3 ha-1) for safflower and niger; and clomazone (0.375 and 0.75 kg ha-1) for rapeseed and niger.