Article published in
Souvenir of the ICAC 74th Plenary meeting held at JW Marriot Mumbai
6-11 December 2015.
Diagnosis holds the key to ‘problem-solving’ in cotton cultivation
K. R. Kranthi
ICAR-Central Institute
for Cotton Research, Nagpur
Cotton –‘the white gold’ is one of the few
commodity crops that have immense potential to bring sustained prosperity to
farmers, traders and Nations. Farmers prefer cultivating cotton over several
other crops, especially under rain-fed conditions. But, year after year,
problems keep cropping up in any of the 80+ cotton growing countries. A long
list of dynamic, unending woes, describes the predicament of the cotton farmers
in India and all across the globe. Most of the times unpredictable rains,
truant-weather, insects, diseases, costly inputs and non-remunerative market,
grab headlines.
Whenever problems crop up intermittently, the
general tendency is to find immediate short term remedies. For example, when
mealy bugs appeared in damaging proportions on cotton in India during
2004-2007, there was an immediate demand for insecticides that could kill the
insects. Any suggestion other than insecticides was scoffed at. History is
replete with such innumerable examples. But, the use of insecticides in many
cases led to the resurgence of the same species or resulted in the outbreak of
some other insects, most of which would have been insignificant otherwise.
Insecticide induced side-effects on ecosystems are not at all uncommon. But,
these are rarely noticed by non-experts. From a technical perspective, it is
important to reconsider the current ‘curative’ approach, in the interest of
sustainability. Ideally, a proper diagnosis of the root cause of a malady would
help in the development of strategies that can prevent the malady itself. This
article is an attempt to propose such approaches to find a path towards
sustainable cotton production in India.
ISSUES, NATURAL FACTORS, DIAGNOSIS AND
SOLUTIONS
ISSUES:
1.
LOW
YIELD: Cotton yields of 500-550 kg lint per hectare place India at 32-33rd
rank in the world. The average global yield excluding India is 904 Kg lint per
hectare. It is a matter of concern that the yields of irrigated cotton in India
are 1.5-2 fold less than the yields in rain-fed conditions of many other
countries.
2.
CHEMICALS
FOR BIOTIC STRESS MANAGEMENT: The number of insecticide applications on cotton per
season is amongst the highest in the world. Insect resistance to insecticides
is highest in India. Insecticide usage on cotton is probable the most
intensive and extensive in India compared to many major cotton growing
countries across the globe.
Insects: Cotton
crop is generally believed to be a haven of insects. Over the past 40 years,
the crop in India suffered the most due to insect attacks. A range of insects
such as aphids, jassids, whiteflies, mealy bugs, thrips, armyworms, hairy
caterpillars, semi-loopers, Spodoptera,
American bollworm, pink bollworm, spotted bollworm etc have been ravaging
cotton time and again.
Diseases: Though
there are a few diseases that are problematic in cotton, the cotton leaf curl
virus is most dreaded, because like many viral diseases it cannot be cured. The
disease is confined to north India and Pakistan.
Weeds: Cotton crop
is most adversely affected due to weeds during the first 60-70 days of the
crop. Therefore it is important that the crop is kept free of weeds during this
period.
3.
BOLLWORM
RESISTANCE TO BT COTTON: Bollworms are adapting to Bt-cotton. The damage by ‘BG-II resistant’ pink bollworms in
Gujarat was significant in 2014 and 2015 and is expected to continue in the
years to come.
4.
HIGH
FERTILIZER USAGE: Fertilizer usage on cotton is amongst the highest in the
world. The crop is responding less to fertilizer usage due to declining soil
health.
5.
RISING
COSTS & DECLINING PROFIT MARGINS: Data from the Ministry of Agriculture
show that over the past 10 years, from 2002 to 2012, the cost of cultivation
increased 3-fold. Seed cost increased 3.7-fold, labour cost increased 4.2-fold,
fertilizer cost per hectare increased 4.6-fold and insecticide costs per
hectare doubled over the past 5 years. The net profit plummeted to Rs 1758 per
hectare, which is almost equivalent to the general range of profits obtained
prior to 2004.
6.
FIBRE
QUALITY: In recent times, over the past 10 years, there has been a significant
improvement in fibre quality in India. However, issues with declining
micronaire and variable length and reduction in strength in second and
subsequent pickings, are causing concerns.
7.
WATER
& SOIL:
Water: Like for any crop, water is critical
for cotton. But, cotton is basically a xerophytic crop. Xerophytic plants are
those that can survive with less water. Kozlowski
– 2012 in his book ‘Additional Woody Plants’ writes that ‘Cotton plants (Gossypium)
are tropical and subtropical xerophytic, perennial shrubs.’
Cotton crop needs about 1000 mm water in its cycle. The requirement during
early vegetative stage is only 10-15% of the total water requirement of about
1000 mm for the crop. The crop needs 50-60% of the water requirement during
flowering period and rest of the water during boll formation stage.
Soil: Medium and
heavy textures soils are suitable for cotton cultivation. But, contrary to this
common belief, the crop is also cultivated in light soils to obtain high
yields. Deep soils with good water holding capacity provide water and nutrients
to the crop during flowering and boll formation stage. The crop requires 0.5 to
1.0 kg/ha Nitrogen per day during vegetative phase and 3-4 Kg/ha Nitrogen per
day during flowering and boll formation stage.
8.
MISMATCH
OF WEATHER AND ‘CROP-NEEDS’: Despite the prevalence of ideal weather conditions
for cotton in India, the crop suffers because of the long duration of 180-240
days. The 80-90 day window of flowering and 100-140 day window of boll
formation get caught in a range of unsuitable weather conditions that lowers
the yields significantly. As mentioned above, the flowering and boll formation
window also suffers water and nutrient stress.
Weather: Compared to
many major cotton growing countries, Indian weather is best suited for cotton. The preferred temperature range for flowering and boll formation is 27 to 32oC
with day temperatures higher than 20oC and night temperatures higher
than 12oC. Many varieties and hybrids actually perform best under
short-day conditions.
DIAGNOSIS
1.
Low yields: Indian yields are low because of low plant density
of 11,000 to 16,000 plants per hectare as compared to 111,000 to 222,000 plants
per hectare in major cotton growing countries such as China, USA, Brazil,
Mexico and Australia. Because of low
plant density, each plant is expected to produce a large number of bolls per
plant, which takes a longer duration. The long duration extends the flowering
and boll formation into a staggered phase which coincides with the late season
when moisture and nutrients are not deficient.
2.
Water stress and
nutrient deficiency during flowering and boll formation is responsible for low
yields.
Cotton crop in India is of long duration. Flowering starts during the end of
monsoon and continues for about 80-90 days after the cessation of monsoon.
Under rain-fed conditions in India the crop suffers severe water stress and
nutrient deficiency specifically at the flowering and boll formation stage,
thereby resulting in low yields.
For example,
Maharashtra and Telangana together cultivate 5.7 million hectares, thus
accounting for half of India’s cotton area. More than 90% of the area in the
two states is under rain-fed conditions. Normal monsoon in the major cotton
growing areas of Maharashtra and Telangana starts in June and recedes by early
September. Peak flowering and boll formation windows start after September. The
crop suffers severe moisture, nutrient and weather stress during flowering and
boll formation stage this resulting in low yields. The yields are lowest in the
two states thus lowering down the average yields of India.
3. Acute insect pest
damage is because of the long duration of 180-240 day crop. The long 80-90 days flowering window and 100-140 days window of boll
formation in India leads to continuous influx of insects. In all the major
cotton growing countries, the crop is of short duration at 150-160 days and in
any case would be terminated before 180 days. Since the crop is under high
density each plant is expected to produce only 7-10 bolls per plant, the
flowering window is about 20-30 days and has less problem with the American
boll worms making it easier for pest management. Pink bollworm is a late season
pest and occurs mainly on the crop after the 180 day duration. Thus short
duration crops escape the pink bollworm because they are harvested before the
occurrence of the pest.
4. Late sown crop is more
vulnerable to the whiteflies, jassids, mealybugs thrips, boll worms and CLCuD. Yields are low under late in late sown crop because all the tender
stages of the crop coincide with the peak infestation of insect pests.
5.
Human interventions cause insect pests and diseases. Long duration hybrids need more nutrients and water. Excessive
application of water and nutrients especially urea leads to more foliage and
attracts sucking pests. Sucking pests necessitate application the recommended
groups of insecticides such as ‘organophosphate’ and ‘neonicotinoid’
insecticides. Application of these insecticides lead to staggered flowering and
delayed maturity, thus leading to more insects and more insecticide usage. It is an established fact that the whiteflies, aphids
and American bollworm problems were because of a combination of factors such as
long duration American cotton hybrids + repeated application of synthetic pyrethroids.
Apart from these indiscriminate use of insecticides causes pest resurgence,
resistance, residues and ecological
disruption apart from the toxicity to non-target organisms.
Mono-cropping
aggravates insect pests, diseases and causes nutrient deficiencies. Cotton as a sole crop year after year in the
same land leads to insect pest and diseases. In many parts of India cotton is
cultivated round the year from June to May. Insect pests such as mealy bugs and
pink bollworms thrive in repeated cycles and cause havoc to cotton sown in the
region.
SOLUTIONS:
1.
Cotton
varieties
a.
Short
duration of 150 days
b.
Compact
short statured -suitable for high density
c.
Resistance
to sap-sucking pests and CLCuD
2.
Early
or timely sowing, especially in rain-fed regions
3.
Avoidance
of excessive urea, organophosphates and neonicotinoid insecticides
4.
Integrated
pest management and insecticide resistance management tools for efficient pest
management would help in reducing chemical inputs.
5.
Intercropping
with legume crops such as soybean, greengram, blackgram or cowpea for nitrogen
fixation and IPM (integrated pest management)
6.
Desi
species Gossypium arboreum and Gossypium herbaceum are robust and are
ideally suited for tough conditions with low inputs. Short duration Desi
varieties under high density planting can provide high yields with low inputs
in rainfed farming.
7.
Short
duration varieties sown in time with onset of monsoon, under high density
planting will be able to get proper soil moisture and nutrients. Such varieties
will have a narrow flowering window of 20-30 days that would possibly enable
the crop to escape the American bollworms. Soil moisture would also be available
adequately during the short flowering and boll formation window for the 7-9
developing bolls per plant. With available soil moisture, the plants are able
to absorb available nutrients. Under high density planting of 1.6 to 2.0 lakh
plants per hectare, 7-9 bolls per plant result in high yields in a short time. Weather
conditions of 27 to 32 oC with day temperatures higher
than 20oC and night temperatures higher than 12oC are prevalent during
the monsoon and the immediate period after cessation of monsoon, which
coincides with the 20-30 day flowering and 60-90 day boll formation phase. Boll
bursting is synchronous in high density planting. With the availability of
adequate soil moisture and nutrients the fibre quality is uniform and good.
Intercropping with short duration legumes provides adequate nitrogen exactly at
the flowering and boll formation stage. Legume intercropping provides a wide
range of beneficial natural enemies that assist in IPM, thereby reducing the
need for insecticides. Cultivation of legume intercrops in between rows in high
density systems or in crop rotation reduces the need for repeated weeding and
can assist in conservation agriculture.
QUESTIONS AND ANSWERS
1. Why are the yields low in India? Can the yields be
enhanced form the current Indian average of 500 kg/ha to the world average
(excluding India) of 904 kg/ha?
Yields
are low in India because of low plant density and long duration. High yields can
be obtained through short duration varieties planted in high density.
2. Why are the insect pest problems so acute on cotton in India unlike in other
countries?
Insect pest problems are very acute in India because of the long
duration of the crop and the long flowering and boll formation window.
3.
Why did the Indian farmer resort to highest number of
insecticide applications prior to Bt-cotton and now despite Bt-cotton?
Excessive application
of urea in hybrids leads to luxuriant vegetation and a long flowering window
which attract insects over a long period of time. The continuous stream of
insects on the long duration hybrids necessitates insecticide applications that
disrupt ecosystems and lead to the need for repeated insecticide applications.
Insecticides were used mostly for bollworm control prior to Bt-cotton. The area
under hybrids increased from 38% in 2002 to 95% in 2012. Because of long
duration, the hybrids are more vulnerable to a wide range of insects. While
bollworms were being effectively controlled by Bt, sap-sucking insects needed
insecticide applications. Thus far more than 1600 Bt-hybrids have been approved
in India. Most of these are susceptible to sap-sucking insects. Thus farmers
have been using insecticides on sucking pests now and also against the pink
bollworm which developed resistance to Bt-cotton in some parts of the country.
4. Are insecticides and GM (genetic modification) the only reliable technologies
for insect pest management? Without the use of chemicals or (GM) technologies,
is it possible to prevent insects from causing economic damage?
Many countries circumvent the need for chemicals and GM crops by using
short duration cotton varieties. Turkey and Uzbekistan are good examples.
5.
Why did the fertilizer usage increase so significantly
in recent years?
Cotton crop is not
responding positively to chemical fertilizers due to deterioration in soil
health and the poor organic carbon content.
Chemical fertilizer
usage increased with the increase of Bt cotton hybrid area.
6.
Without irrigation, is it possible to ensure that the
crop gets adequate water during the crucial stage of flowering and boll
formation stage?
Short duration crop
with early maturity has flowering and boll formation stages that are adequately
covered by the monsoon regimen. Therefore there would be no separate need to
irrigate the crop at the crucial stage.
7.
Without fertilizer application, is it possible to
ensure that the crop gets adequate nitrogen during flowering and boll formation
stage?
Legume
intercrops, FYM, vermi-compost and bio-fertilizer application can provide the
short duration varieties adequate amount of nutrients for a healthy crop and
high yields. There may be less need for chemical fertilizers with improvement
in soil health due to the intercrops and reduction in the use of chemical
application.
8.
Is it possible to
ensure that the crop gets the desirable weather conditions during flowering and
boll formation?
Early sowing of short duration cotton in half of
India’s rainfed cotton which is in the two states of Maharashtra and Telangana,
helps in creating a match between desirable weather and flowering and boll
formation
9. Without herbicide usage, which are the other technologies to prevent weed
damage?
Intercrops, high density and conservation
agriculture can help in minimizing weeds.
10. Can we prevent the CLCuD (Cotton leaf curl virus disease) in north India
with simple strategies?
The best solution to the CLCuD is early sowing in
April with varieties tolerant to whiteflies and the CLCuD. Desi cotton
varieties are immune to the CLCuD and highly tolerant to whiteflies.
CONCLUSION
Simple
solutions can provide major relief. Short duration cotton varieties sown early
in high density with legumes either as intercrops or in crop rotation in high
density planting systems can help in IPM, escape almost all insect pests and
obtain water and legume-fixed-nitrogen during the critical flowering and boll
formation window. Thus high yields can be obtained from low input agriculture.