RA 00015.pdf - OAR@ICRISAT

A trial was conducted to explore the possibilities
of employing the minimum- and zerotillage
concept to reduce the time lag between
crops and to conserve soil moisture, both of
which are very critical for the optimum growth of
a postrainy season crop of chickpea. The maximum
yields of chickpea were obtained in the
following three treatments: optimum tillage and
hand weeding, paraquat and prometryne with no
cultivation, and paraquat and three cultivations
(Table 63).
Individual crops. Major emphasis is being directed
to determine the competitiveness with
weeds and herbicide tolerance of different cultivars
of sorghum, pigeonpea, pearl millet, chickpea,
and groundnut. Field trials involving many
cultivars of these crops conducted during the
1976-1977 seasons indicated that crop cultivars
differ in their tolerance to a given herbicide and
also vary in their weed competitive ability. As
this "intra specific differential response" may be
related to environmental conditions, continuing
research on this problem is planned before
Table 63. Crop stubble and postrainy season
weed management for chickpea on
Vertisols at ICRISAT Center,
1976-1977.
Weed dry
matter at
Treatments Yield harvest
(kg/ha)
(kg/ha)
1 Hand weeding + three 1060 300
cultivations
2 Three cultivations 790 1070
3 Paraquat (1.0 kg/ha) 1030 790
+ three cultivations
4 One minimum cultivation 530 980
+ paraquat (1.0 kg/ha)
5 Paraquat (1.0 kg/ha) 1030 650
+ prometryne
(0.75 kg/ha)
and no cultivation
L.S.D.(0.05) 240 420
drawing definite conclusions. Similarly, experiments
are also being continued to determine the
ability of different crop cultivars to suppress
weeds and their ability to grow well in spite of
them. In groundnut, spreading and semispreading
cultivars were significantly more competitive
with weeds than was the bunch type. In pearl
millet, tall and profusely tillering cultivars compete
with weeds more efficiently than dwarf and
poor tillering types. In sorghum, plant height and
initial seedling vigor were the characters identified
as responsible for weed competitive ability.
Herbicide screening. To determine the crop
tolerance and weed-control activity of some
selected herbicides, two herbicide-screening trials
were conducted. Visual evaluation of crop
injury and weed control from preemergence
applications of herbicides recorded on sorghum,
pearl millet, pigeonpea, chickpea, and groundnut
are as follows: On sorghum, atrazine (1 kg/
ha), prometryne (1.5 kg/ha), ametryne (1.5
kg/ha), terbutryne (1.5 kg/ha), and Tribunil (2.0
kg/ha) showed promise. Among the herbicides
tested on pearl millet, only atrazine (0.5 kg/ha)
and Tribunil (1 kg/ha) were found safe on the
crop. Nitrofen (2 kg/ha), dinitramine (0.5 kg/ha),
prometryne (1.0 kg/ha), ametryne (1.0 kg/ha),
terbutryne (1.0 kg/ha), Modown (2.0 kg/ha), and
Tribunil (2.0 kg/ha) were all found to be effective
on pigeonpea. Among the herbicides evaluated
on groundnut, dinitramine (0.5 kg/ha), alachlor
(2.0 kg/ha), nitrofen (2.0 kg/ha), Prefar (4.01/ha),
and devrinol (4 1/ha) proved promising. On
chickpea, nitrofen (2.0 kg/ha), alachlor (2.0
kg/ha), dinitramine (0.5 kg/ha), Prefar (4 1/ha),
prometryne (1.0 kg/ha), ametryne (1.0 kg/ha),
and terbutryne (1.0 kg/ha), were found to be
effective.
Weeds and weeding systems survey. In a few
selected villages representative of the Indian
SAT, surveys were made in collaboration with
ICRISAT economists to observe weed problems,
weeding systems, and the extent to which the
farmers understand their weed problems. The
existing methods of weed control are hand
weeding with a small hoe and intercultivating
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