Bio-efficacy of some promising herbicides in transplanted kharif rice and their influence on soil microflora.

摘要

Field experiments with the objectives (i) to evaluate the bio-efficacy of different promising herbicides for environmentally safe and economically viable weed control measure, (ii) to evaluate the phytotoxicity in crop plants, (iii) to study the effect of herbicides on soil micro flora were conducted in Gangetic Inceptisol at the Viswavidyalaya Farm, Kalyani during kharif 2005-06 with 9 treatments viz. Ethoxysulfuron 60 WG @ 15, 17.50, 20 & 40 g ha-1, Ethoxysulfuron 15 WP @ 18.75 g ha-1, Almix 20 WP @ 4 g ha-1 all applied at 15 DAT, 2,4-DEE 38 EC @ 400 g ha-1 at 20 DAT, hand weeding twice at 20 & 40 DAT and the unweeded control. The treatments were replicated thrice in a RBD design. Predominant weeds were Echinochloa Crusgalli, Echinochloa colona, Cyperus iria, Cyperus difformis, Fimbristylis littoralis, Alternanthera philoxeroides, Stellaria media, Ludwigia parviflora, Ammania baccifera and Marsilea quadrifolia. Results revealed that hand weeding twice gave highest grain yield (5.08 t/ha) and this treatment did not differ significantly with Almix 20 WP @ 4 g ha-1 (5.01 t ha-1) and the three higher doses (18.75, 20 & 40 g ha-1) of Ethoxysulfuron. Weed control efficiency of Almix 20 WP @ 4 g ha-1 at 60 DAT was highest (90.44%) among the tested herbicides. Regarding benefit:cost ratio, the highest value (1.41) was obtained with Almix 20 WP @ 4 g ha-1 among the herbicides tested in this experiment. No phytotoxic effect on the crop was observed. The soil microflora study showed that all the herbicides tested had no detrimental effect after 30 days of application though population in the initial stage showed slightly decrease in fungi, actinomycetes and total bacteria. Almix 20 WP @ 4 g ha-1 or the higher two doses of Ethoxysulfuron 60 WG @ 20 and 40 g ha-1 or Ethoxysulfuron 15 WP @ 18.75 g ha-1 as post-emergence can profitably and safely replace the tedious, time consuming and expensive hand weeding practice in this Gangetic Inceptisol without any injury to the crop plant and the soil micro-flora also.