The objective of this work was to evaluate the carryover potential of the herbicides imazaquin (150 and 300g eq. acid ha-1) and alachlor+atrazine (1430+1430 and 2860+2860g ha-1), applied respectively to soybeans and corn crops, aiming at determining the smallest period of time between utilization of these products and canola planting date succeding these crops. Soil samples were collected at 15, 30, 60, 90 and 120 days after application (DAA) of the herbicides on field and ten canola seeds were sown in each pot. Canola germination was reduced up to 30DAA of imazaquin applied at recommended rate (150g eq. acid ha-1) and up to 60DAA at double the recommended rate. In relation to plant growth, imazaquin inhibited in 30 and 32.5% (rates of 150 and 300eq. acid ha-1, respectively) canola shoot dry biomass production, in soil samples collected at 15DAA. Nevertheless, after 30DAA, no visual symptoms of phytotoxicity were shown. For alachlor+atrazine, the effects on germination and growth were more intense in samples collected up to 30DAA, but phytotoxicity symptoms decreased gradually and after 90DAA no negative effects were observed for the parameters evaluated. The results suggest that canola can be planted 90 days after spraying imazaquin and alachlor+atrazine, with no damage to emergence or crop development derived from residues of these herbicides present in soil.
Brassica napus; herbicides; persistence; residues
