Residual de herbicidas do grupo químico das imidazolinonas na cultura da aveia

Abstract

Herbicides of the imidazolinones chemical group such as imazethapyr and imazapyr + imazapic are often used in the weeds management in irrigated rice; however, the carryover activity of these can limit development of plants used in succession/ rotation crop. The aim of this work was to evaluate the carryover imidazolinone chemical group in oat crop used in succession to irrigated rice Clearfield® system, in different depths soil and two types moisture. For this, the soil sample was collected in the 0-5; 5-10; 10-15; 15-20 cm, one received application of imazethapyr and another imazapyr + imazapic. The soil with imazethapyr application was collected 1 year and 2 months after herbicide application, and imazapyr + imazapic, had been application eight months before the soil sampling. The treatments were constituted the same for both experiments, and these different soil conditions (satured and field capacity) and different depths. The soil in each experiment was arranged in pots 200 mL, seeded with outs, and they were arranged in randomized experimental design with four replications. Preliminary experiment was conducted to determine dose-response curve. The herbicide imazethapyr doses used were 0; 0,2; 0,4; 0,8; 1,6 commercial times the recommended dose (106 g ha-¹). To imazapyr + imazapic they were used the same doses of 0; 0,2; 0,4; 0,8; 1,6 times the commercial dose recommended (140 g ha-¹). The evaluated variables were injury, plant height and shoot dry mass (SDM). For imazethapyr, the herbicide carryover was quantified 95,4 and 242,7 g a.i., for the saturated soil condition and field capacity, respectively. At 20 cm depth was quantified 183 g a.i., 3 times more than 10 cm depht. For imazapic + imazapyr, saturated soil in 20 cm depth was observed residual herbicide 18,3 g a.i., already on the ground at field capacity at 20 cm depth was observed carryover 42 g a.i. The variable injury presented the results representative soil residual herbicide. For both herbicides in this study, the highest injury values here found in field capacity type, and pronounced in 20 cm soil depth. Values of plant height and SDM oat plants were higher in saturated soil condition to both herbicides. After 1 year and 2 months the imazethapyr application, and eight months imazapyr + imazapic sprayed, observed carryover herbicide sufficient to affect the oat crop development.