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Weed control for quality
cotton production
 THE
rate of productivity of cotton in the country is far below
the world average. Last year cotton was cultivated on an
area of three million hectares with an average yield of 2682
kg per hectare, while the yield potential of recommended
cotton varieties is 4,000 kg per hectare. There is a huge
gap between the actual and the potential yields.
Among various factors like poor plant population, attack of
insect pests, imbalanced use of fertilisers and cotton leaf
curl virus, weeds also play major role in reducing the seed
cotton yield on an average by 30 per cent. Weeds are very
efficient users of resources. They compete with the crop for
space, sunlight, nutrients, moisture; release toxic
compounds and also provide shelter and food for insect pests
and plant pathogens. Control of weeds is essential to reduce
the yield gap between actual and potential yield.
Chemical control of weed is an efficient method, but
environmental concerns and resistance developed in weeds
against herbicides, its use cannot be promoted. There is
also demand for chemical-free cotton worldwide because of
increasing skin and other diseases in human. Moreover, there
are no selective post emergence herbicides available for
weed control in cotton. Therefore, integrated weed
management approaches are emphasised for controlling weeds
in cotton.
Integrated weed control: An integrated weed control
programme is based on use of all possible methods of weed
control starting with sowing of the crop and applying
herbicides only if needed. There are several advantages of
integrated weed control strategies in cotton like
cost-effective, environment- friendly and safe for humans
and animals. All weed control methods should be used by
farmers in the following integrated way for successful weed
control in cotton:
Seed should be of recommended variety, pure and free of weed
seeds. Delinted seed at 20 to 25 kg per hectare gives
optimum plant population. There should be 65,000 to 75,000
plants of cotton in one hectare. When sufficient number of
plants is present in the field the weeds growth is checked
due to increased competition and suppressive/smothering
effects of the crop population on weeds.
Clean cultivation: The farm machinery, particularly drill
used for sowing, should be clean and free of weed seeds.
Similarly clean and weed free water channels, paths, canals,
field bunds are helpful in considerable reduction in weed
population.
Crop rotation: It is growing of crops one after other in a
sequence on the same piece of land. It is an important
cultural practice that reduces the weed flora of a field
without any extra expenditure. Crops like sorghum, maize and
sunflower can be included in rotation for controlling weeds
of cotton.
Intercropping: The crops like soybean, mungbean, sesame,
dwarf sorghum and sunflower can be intercropped in between
cotton rows for suppressing weeds and getting higher net
benefits.
Hoeing is a successful method of controlling weeds. Farmers
with small land holdings particularly practice this method.
Dry hoeing 20-25 days after emergence of crop and/or first
irrigation is done with the help of kasola.
Interculture: Varieties of weeders are available for
inter-cultivation during initial stages of crop growth.
Cultivation is a cheap and effective method of controlling
weeds. Special types of weeders are being used by
progressive farmers for cotton crop sown on beds. Ridger,
used for earthing up, is an important tool for controlling
cotton weeds.
Decomposed farm yard manure: Most of the farmers apply fresh
farm yard manure, which contains weeds seeds. These weeds
seeds directly go to field and germinate when find suitable
conditions. If well decomposed farm yard manure is used then
weed seeds present in it will not be able to germinate and
helps in reducing weed populations.
Balance use of fertilisers: Healthy crop plants successfully
compete with weeds and spare very little space for weeds to
grow. Balanced amount of nitrogen, phosphorus and potassium
should be used to obtain competitive cotton plants.
Allelopathy: Allelopathy being a natural phenomenon is
environment- friendly and can be manipulated for weed
management. The production and release of allelo chemicals
from leaves, flowers, seeds, stems and roots of living and
decomposing plant materials can influence weed density and
growth. Crops like sorghum, sunflower, brassica, maize,
rice, wheat, tobacco and higher plants like mulberry,
eucalyptus, and neem have allelopathic potential against
different broad and narrow leave weeds of field crops.
Theses can be used as intercrops, in rotation or as
allelopathic water extracts alone and in combination with
reduced doses of herbicides.
Chemical control: Use of herbicides is an effective way to
control weeds; however, continuous use of herbicides has
hazardous effects. Therefore, it may be included in the weed
control programme when other methods have been applied.
Knowledge of weed flora prior to sowing cotton crop could
help make decision for using pre or post emergence
herbicides. Weed inspection has great significance with
respect to herbicides application. Farmers should visit
their fields at least twice in a week and record the extent
of weed population and type of weeds present in the field.
On the basis of this information herbicides should be
selected. Pre-emergence application of herbicides like
pendimethalin (Stomp) and Dual Gold are very effective for
controlling broad leave as well as narrow leave weeds. In
case of purple nutsedge, pendimethalin is ineffective.
However, shielded spray of paraquat (Gramoxon) and round-up
(Glyphosate) can be applied only on weeds in the inter row
space carefully, avoiding the cotton. This cannot be
practiced when cotton plants are small. Unfortunately, no
selective post emergence herbicides are available for weed
control in cotton. The best, safe and most economical way to
keep the weeds away and increase yield is by using resistant
varieties of seeds.
Courtesy:
The DAWN
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