Bio efficacy and residue studies of herbicides in soybean wheat cropping system

Abstract

newline The field experiment was conducted at Palampur during kharif 2009 to Rabi 2010-11 to find out an effective weed control schedule in soybean-wheat cropping system. Eight weed control treatments viz. pendimethalin 1500 g ha-1 (pre), imazethapyr 200 g ha-1 (pre), quizalofop ethyl 60 g ha-1 (early post), imazethapyr 75 g ha-1 (pre) fb. imazethapyr 75 g ha-1 (early post), quizalofop ethyl 50 g ha-1 + chlorimuron ethyl 4 g ha-1 (early post), pendimethalin 1500 g ha-1 (pre) fb. chlorimuron ethyl 4 g ha-1 (early post), hand weeding (twice) and unweeded check in soybean as main plot factors and unweeded check, isoproturon 1000 g ha-1 + 2,4-D 500 g ha-1 and isoproturon 750 g ha-1 + 2,4-D 500 g ha-1 in wheat as subplot factors were tested in split plot design with three replications. The soil of the test site was acidic in reaction (pH-5.6), silty clay loam in texture and medium in available nitrogen (284.8 kg ha-1), phosphorus (14.6 kg ha-1) and potassium (268.0 kg ha-1). Among treatments applied in soybean, pendimethalin 1500 g ha-1 (pre) fb. chlorimuron ethyl 4 g ha-1 (early post) effectively managed weeds (Commelina, Echinochloa, Digitaria, Ageratum, Cyperus sp.) with an average weed control efficiency of 61.1 per cent and resulted in higher yield attributes viz. branches per plant, pods per plant and 1000-seed weight, seed yield (18.7 and 18.3 q ha-1) and seed quality (41.1 and 15.0 per cent higher oil and protein content than weedy check). In wheat, both isoproturon 1000 g ha-1 + 2,4-D 500 g ha-1 and isoproturon 750 g ha-1 + 2,4-D 500 g ha-1 were comparable in controlling weeds (Phalaris, Avena, Lolium, Vicia and Coronopus) and increasing yield attributes, yields (38.2 and 35.1 q ha-1) and protein content (14.3 and 13.1 per cent). None of the herbicides applied in soybean had any residual effect on wheat crop as well as on the test crop(s) studied in laboratory. Economic studies on system basis revealed that pendimethalin 1500 g ha-1 (pre) fb. chlorimuron ethyl 4 g ha-1 (early post) resulted in Rs.85096