EVALUATION OF SUB-RATES OF NON-SELECTIVE SYSTEMIC HERBICIDES IN SOYBEANS

Abstract

One experiment was conducted at Estação Experimental Agronômica/UFRGS, in Eldorado do Sul, Rio Grande do Sul, during the 1995/96 growing season, to evaluate the effects of use of sub-rates of non-selective systemic herbicides on soybean, applied at advanced developmental stages. The treatments consisted of applications of the herbicides 2,4-D at rates of 5 and 10 g/ha a.e., imazapyr at 25 and 50 g/ha a.e., and sulfosate at 25 and 50 g/ha te., sprayed at flowering initiation (R. stage) or at the beginning of pod development (12 5 stage). Imazapyr, regardless of the rate applied, reduced the first pod height and the soybean plant height when sprayed at beginning of pod formation. Imazapyr also reduced grain yield by 48% for rate 1 and by 81% for rate 2, when compared to untreated plots, and applied at beginning of pod development. The herbicides 2,4- D and sulfosate did not differ from the untreated check for the variables evaluated. In relation to the untreated plots, sulfosate incrcased soybean grain yield by 10%, on the average of rates.