Efficacy of imidazolinone herbicides in green gram (Vigna radiata L.) and their persistence in soil
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Date
2017
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CCSHAU
Abstract
The study an “Efficacy of imidazolinone herbicides in green gram (Vigna radiata L.) and their
persistence in soil” was studied through one field experiment on “Bioefficacy of imazethapyr and its ready-mix
combination with imazamox (Odyssey) against weeds in green gram and their residual carryover effects on
succeeding crop” conducted at Agronomy Research Area of Department of Agronomy, two pot experiments on
“Degradation of imazethapyr and imazethapyr + imazamox (RM) in sterilized and unsterilized soil” and
“Persistence of imazethapyr and imazethapyr + imazamox (RM) as affected by soil” conducted in Screen
House of Department of Agronomy and one laboratory study on “Dissipation behavior of imazethapyr and
imazethapyr + imazamox (RM) in soil by GC-MS” conducted in Residue Testing Laboratory of Department of
Agronomy, CCS Haryana Agricultural University, Hisar, Haryana.
The major weed species in the experimental field were Trianthema portulacastrum and Cyperus
rotundus. Other weeds present in experimental field were Convolvulus arvensis, Digitaria sanguinalis,
Dactyloctenium aegyptium, Celosia argentea, Physalis minima and Cynodon dactylon during both the years.
Imazethapyr at 80 g/ha PPI and imazethapyr + pendimethalin (RM) at 1000 g/ha PRE (being at par with each
other) gave excellent control of complex weed flora and increased seed and biological yield of green gram
significantly over weedy check during both the years.
As the dose of imazethapyr applied in green gram as PPI and POE increased from 70 to 80 g/ha,
phytotoxicity on mustard increased singnificantly. Plant population, growth parameters viz. emergence, number of
leaves, plant height, seed yield and biological yield also reduced significantly with increasing imazethapyr doses,
during both the years.
The experiment on effect of sterilization on persistence of imazethapyr and imazethapyr + imazamox
(RM) revealed that unsterilized soil resulted in better growth of mustard at each incubation period and
concentration than sterilized soil. Half-life of imazethapyr and imazethapyr + imazamox (RM) were estimated to
be 27 and 20 days in sterilized soil compared to 20 and 14 days in unsterilized soil, respectively.
The studies on effect of soil texture on persistence of imazethapyr and imazethapyr + imazamox (RM)
showed that reduction in growth indices viz. emergence per cent, plant height, number of leaves and dry weight per
plant of mustard was significantly higher in clay loam soil than sandy loam and loamy sand soil at each
concentration of imazethapyr and imazethapyr + imazamox (RM) and increased growth with increasing incubation
periods. Growth of mustard decreased significantly as imazethapyr and imazethapyr + imazamox (RM)
concentration increased from 0 to 140 g/ha. The dry weight per plant decreased by 61 to 98 per cent in sandy loam,
42 to 92 per cent in loamy sand and 72 to 96 per cent in clay loam soil as imazethapyr concentration increased
from 0 to 140 g/ha compared to 44 to 86 per cent in sandy loam, 27 to 86 per cent loamy sand and 61 to 90 per
cent clay loam soil with imazethapyr + imazamox (RM) in respective doses. Half-life of imazethapyr in sandy
loam, loamy sand and clay loam was 20, 14 and 23 days as compared to 14, 9 and 12 days with imazethapyr +
imazamox (RM) in respective soil textures.
Residue analysis of experimental field soil by GC-MS-tandem mass spectrometry equipped with
capillary column revealed that per cent recoveries at fortification level 0.003 and 0.006 μg/g in both the herbicides
were more than 80 per cent depicting validity of methods used for present studies. Dissipation followed a first
order kinetics with a half-life of imazethapyr was 25, 21 and 16 days when applied as PPI, PRE and POE at single
dose (70 g/ha) as compared to 30, 25 and 18 days in double dose (140 g/ha), thereby shows greater persistence of
imazethapyr when applied as PPI whereas, half-life of imazethapyr + imazamox (RM) was 20, 18 and 13 days at
single dose (70 g/ha) as compared to 26, 21 and 16 days in double dose (140 g/ha) at respective times of
application. Persistence of imazethapyr was found to be greater than imazethapyr + imazamox (RM) at all the
application times (PPI, PRE and POE) and at both the doses, higher at double dose as compared to single dose for
both the herbicides. Half-life of imazethapyr and imazethapyr + imazamox (RM) was in order of PPI > PRE >
POE.
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