Nodulation and nitrogen fixation in soybeans treated with herbicides

Abstract

Under greenhouse condition an experiment was carried out to evaluate trifluralin, chlorimuron and clomazone effects on nodulation and nitrogen fixation in soybeans (Glycine max (L.) Marr. cv Uberlândia). Nitrogen fixation was assessed by the xylem-solute technique. The samples were collected at 14 day intervals, from 14 up to 126 days after emergence (DAE). Chlorimuron treated plants showed a reduction in the number (Nn) and dry matter of nodules (Wn) up to 28 and 42 DAE, respectively. Trifluralin (800 g a.i./ha) stimulated both Wn and Nn up to 28 DAE, whereas at its highest rate (1600 g a.i./ha) it decreased both Wn and Nn, up to 42 DAE. Clomazone did not affect Wn; however, its application increased the number of nodules in treated plants up to 28 DAE. Finally, the highest rates of herbicides reduced N2 fixation during the first vegetative growth stages.