Bio-efficacy of herbicides in groundnut and residues of pendimethalin in soil under fingermillet - groundnut cropping system.
Field experiments were conducted during 1996-97 and 1997-98 in a red sandy loam soil in Bangalore, Karnataka, India, under finger millet-groundnut cropping system. The treatments comprised an unweeded control; pre-emergence application (3 days after sowing) of pendimethalin and metolachlor at 1.00 kg/ha; post-emergence application (15 days after sowing) of fluazifop-P-butyl [fluazifop-P] at 0.125 kg/ha; and hand weeding 20 and 45 days after sowing. The major weed flora observed were Cynodon dactylon and Cyperus rotundus (sedges), Digitaria marginata [Digitaria ciliaris], Dactylotium aegyptium [Dactyloctenium aegyptium] and Chloris barbata (grasses), Acanthospermum hispidum, Ageratum conyzoides, Borreria articularis and Commelina benghalensis (broadleaf weeds). Pendimethalin controlled weeds effectively and the yields were comparable to that of hand weeding, followed by metolachlor. Fluazifop-P-butyl could control only grassy weeds. The residues of pendimethalin persisted in the soil up to 60 days only. The half-lives, determined by chemical assay method, were 31.32 and 32.27 days during the two-year study period.