Influence of post emergence herbicides on weeds, nodulation and yields of soybean and soil properties

A field experiment was conducted at Pantnagar during kharif 2008 to examine the effect of postemergence herbicides in soybean on productivity, weed infestation and soil health. Treatments consisting of clodinafop-propargyl 8% EC at 80, 100 and 165 g a.i. ha⁻¹, Na-acifluorfen 20% SL of 165 and 206.2 g a.i. ha⁻¹, combination of clodinafop-propargyl 8% EC + Na-acifluorfen 16.5% SL at 80 + 165, 100 + 206.2 and 160 + 330 g a.i. ha⁻¹, imazethapyr 10% SL at 100 g a.i. ha⁻¹, weed free and weedy check were tested in RBD with 3 replications. The soybean variety used for the study was PS1347. Treatment of weed free check was found best by recording highest nodulation, yield and yield attributes, N uptake and soil parameters. It was at par with imazethapyr 10% SL @ 100 g a.i. ha⁻¹, the treatment that showed highest nodule and plant dry weight, weed control efficiency, grain yield (1975 kg ha⁻¹), straw yield (2445 kg ha⁻¹), N uptake (136.4 kg ha⁻¹ in grain and 40.9 kg ha⁻¹ in straw), soil organic carbon, available N, P, K, microbial counts and dehydrogenase activity among different herbicides treatments. Clodinafop-propargyl 8% EC + Na-acifluorfen 16.5% SL was also found effective in weed control with 100 + 206.2 g a.i. ha⁻¹. It was comparable to imazethapyr 10% SL @ 100 g a.i. ha⁻¹ in weed index, weed control efficiency, nodule dry weight, grain and straw yields, N uptake, soil organic C, available N and K, microbial counts and dehydrogenase activity. The highest net return of Rs. 39563 ha⁻¹ was obtained with weed free check, which was at par with imazethapyr 10% SL @ 100 g a.i. ha⁻¹ and Clodinafop-propargyl 8% EC + Na-acifluorfen 16.5 SL @ 100 + 206.2 g ai ha⁻¹.