EFFECT OF POST EMERGENCE HERBICIDES ON GROWTH, PHYSIOLOGICAL PARAMETERS AND YIELD OF BLACKGRAM (Vigna mungo (L.) Hepper)

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Date
2016
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Acharya N.G. Ranga Agricultural University
Abstract
The present investigation entitled “Effect of post emergence herbicides on growth, physiological parameters and yield of black gram [Vigna mungo (L.) Hepper]” was undertaken at Agricultural College Farm, Bapatla during kharif, 2015. The experiment was laid out in Randomised Block Design with ten treatments replicated thrice. Post emergence herbicides viz., imazethapyr @ 50g and combined use of acifluorfen sodium 16% EC + clodinafop propargyl 8% EC (24%EC) @ 240 and 300g a.i ha-1 applied at 15 and 25 DAS caused injury to blackgram plants in terms of stunting and yellowing/discoloration of leaves during initial stages i.e. 5 days after herbicide application (DAHA), indicating a condition of oxidative stress in blackgram due to herbicide injury. However, blackgram plants recovered quickly by 10 DAHA by possessing highest SOD activity (antioxidant defense enzyme) in the first five days after application and the phytotoxicity symptoms were disappeared by 40 DAS and ultimately no deleterious effect on the mature plants was observed in all the treatments, except acifluorfen sodium + clodinafop propargyl @ 300g a.i ha-1 at 25 DAS (T8), which caused severe stunting, discoloration and wilting of leaves at 5 DAHA and the symptoms remain unchanged upto maturity that adversely affected growth attributes and yield of blackgram. Weed free treatment (i.e. hand weeding at 15 and 30 DAS) and post emergence application of acifluorfen sodium 16% EC + clodinafop propargyl 8% EC (24%EC) @ 240 and 300g a.i ha-1 at 15 DAS recorded superior performance by increasing plant height, number of branches and leaf area over un weeded control and other treatments. These three treatments significantly reduced the weed population (i.e. both monocot and dicot weeds) and weed drymatter compared to un weeded control and other herbicidal treatments at 60 DAS and registered higher weed control efficiencies i.e. 83.0, 70.6 and 68.0 per cent, respectively. At harvest, total drymatter of blackgram plants was increased by 1.56, 1.54, 1.50 folds with weed free check and acifluorfen sodium + clodinafop propargyl @ 300 and 240g a.i ha-1 applied at 15 DAS, respectively, over weedy check. Photosynthetic pigments viz., chlorophyll a, chlorophyll b, total chlorophyll and carotenoid contents decreased in blackgram leaves during first 5 DAHA due to phytotoxicity of these herbicides. However, the blackgram plants recovered from the phytotoxicity of acifluorfen sodium + clodinafop propargyl and imazethapyr by 10 DAHA. Weed free check and acifluorfen sodium + clodinafop propargyl @ 300 and 240g a.i ha-1 applied at 15 DAS increased the total chlorophyll content by 34.3, 28.7 and 27.2 per cent, respectively and carotenoid content by 10.3, 9.4, 8.7 per cent, respectively, over weedy check at 40 DAS (i.e. 25 DAHA). Higher SOD activity was recorded during first five days after application with acifluorfen sodium + clodinafop propargyl @ 300 and 240g a.i ha-1 at 15 DAS, which helped in the mitigation of herbicide injury. Weed free check and post emergence application of acifluorfen sodium + clodinafop propargyl @ 300 and 240g a.i ha-1 at 15 DAS increased the yield attributes and seed yield of blackgram. These three treatments increased the seed yield by 77.6, 69.4 and 67.8 per cent, respectively, over unweeded control. Though, imazethapyr @ 50g ha-1 at 15 and 25 DAS recorded significant increase in yield (25.3 and 29.9 percent, respectively) over weedy check, but these two treatments were inferior over the combined use of acifluorfen sodium + clodinafop propargyl @ 240 and 300g a.i ha-1 at 15 DAS. The highest benefit cost ratio was recorded with acifluorfen sodium + clodinafop propargyl @ 240g a.i ha-1 (i.e. 1.59) and this was closely followed by acifluorfen sodium + clodinafop propargyl @ 300g a.i ha-1 (i.e. 1.56). From this study, it can be concluded that post emergence application of acifluorfen sodium 16% EC + clodinafop propargyl 8% EC (24% EC) @ 240g a.i ha-1 at 15 DAS is recommended for weed control in blackgram as it improved the growth, physiological parameters, photosynthetic pigments and yield of blackgram.
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