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.
Description
D5262
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