Elizabeth, K SyriacSheeja, K RajKAU2020-07-152020-07-152016173688http://krishikosh.egranth.ac.in/handle/1/5810149188PhDThe experiment entitled "Herbicide mixtures for weed management in direct seeded puddled rice Oryza saliva L." was carried out at College of Agriculture, Vellayani, during the period from 2013 - 2016, to assess the bioefficacy of two post emergence herbicide mixtures viz., bispyribac sodium + metamifop and penoxsulam + cyhalofop butyl in direct seeded rice; to study the residual effect in soil; to investigate the impact on microbial and earth worm population, soil enzyme activity and weed seed bank and also to assess the in vitro sensitivity to soil borne pathogen, Rhizoctonia solani, bio control agents and bio fertilizer organisms. Field experiment was undertaken during first and second crop seasons of 2014-15 at Nemom block at farmer's field. The experiment was laid out in RED with 12 treatments and three replications. Bispyribac sodium + metamifop @ 60, 70, 80 and 90 g ha"*,penoxsulam + cyhalofop butyl @ 120, 125, 130 and 135 g ha"*, bispyribac sodium @ 25 g ha"', penoxsulam @ 22.5 g ha"', hand weeding twice and weedy check constituted the treatments. The higher three tested doses of penoxsulam + cyhalofop butyl v/z.,125, 130 and 135 g ha ' and the highest tested dose of bispyribac sodium + metamifop viz., 90 g ha"' were better than other weed management treatments in improving the growth and yield attributes of rice. Pooled analysis indicated the superiority of penoxsulam + cyhalofop butyl @ 135 g ha"' which recorded the highest grain yield (8463 kg ha ' ) and it was statistically on par with its lower doses (130 and 125 g ha*'). Straw yield was not significantly influenced by the weed control treatments. Penoxsulam + c^lofop butyl @ 135 g ha"' recorded the highest net returns (93744 ha *) and B: C ratio (2.43), which was on par with its lower dose (130 g ha"'). Penoxsulam + cyhalofop butyl @ 135 g ha"' was more effective in reducing the total density of weeds. With regard to the control of sedges and BLW, penoxsulam + cyhalofop butyl was more effective, but with respect to grasses, both the herbicide mixtures were more or less similar in effectiveness. Penoxsulam + cyhalofop butyl @ 135 and 136 registered higher weed control efficiency and lower weed index than other treatments. Uncontrolled weed growth caused a yield reduction of 50.38 per cent. Herbicide treatments significantly reduced the nutrient uptake by weeds and enhanced the nutrient uptake by crop over weedy check. The higher doses of penoxsulam + cyhalofop butyl (125,130 and 135 g ha"') and bispyribac sodium + metamifop (70, 80 and 90 g ha*') were more effective in maintaining higher nutrient content in soil. Dynamics of soil microbial population, earthworm population, soil enzyme status and organic carbon content of soil consequent to the application of herbicide mixtures revealed that, both penoxsulam + cyhalofop butyl and bispyribac sodium + metamifop at their tested doses did not have any inhibitory effect. Results of screening trial revealed that maize was the most sensitive indicator plant for both the herbicide mixtures. Dry weight and fresh weight of maize shoot were adjudged as the best parameters for assessing the residual effect of bispyribac sodium + metamifop and penoxsulam + c>^Iofop butyl in soil respectively. Pot culture bioassay studies revealed that the tested herbicide mixtures and their doses did not have any residual effect. In vitro sensitivity studies of bispyribac sodium + metamifop and penoxsulam + cyhalofop butyl to Rhizoctonia solani pointed out that both the herbicide mixtures inhibit the growth of Rhizoctonia solani. Studies on the in vitro effect of herbicide mixtures to Trichoderma viride indicated that bispyribac sodium + metamifop was safe to the fungus, whereas penoxsulam + cyhalofop butyl was moderately toxic. Compatibility studies revealed that both the herbicide mixtures were highly compatible with Psetidomonas fluorescenSy Azospirillum lipoferum and Azotobacter chroococciim. Weed seed bank assay results indicated the effectiveness of the higher doses of penoxsulam + cylialofop butyl (135, 130 and 125 g ha'') in depleting the seed bank compared to other treatments. The present study revealed the superiority of heibicide mixtures over individual herbicides in the management of weeds in wet seeded rice. Application of penoxsulam + cyhalofop butyl @ 135 or 130 g ha*', at 15 DAS could be adjudged as the most economic and ecofriendly weed management practice for wet seeded rice as evidenced by high weed control efficiency, net returns and B: C ratio; environmental safety, high inhibitory effect to Rhizoctonia solani and good compatibility with bio control agents and bio fertilizer organisms.ennullThesis