Though most of the organic cotton in the world comes from Asia, Texas in the USA is also a major producer. Although specific growing methods may vary based on region and farm size, there are general principles that can be applied throughout the world when it comes to growing organic cotton
There are many reasons to grow cotton organically. The market share of organic cotton has grown from 1% in 2008 to 21% in 2018. Half of this is grown in India, with China (17%), Kyrgyzstan (7%), and Turkey (7%) being the next major producers.
It takes three years for farmers to convert to organic farming, as this is the time required for soil to become free of chemical fertilizers and pesticides. Initially, the organic yield is less. However, by the third year, the yield was similar to conventional farms, in an Indian experiment, and the ROI of organic cotton was 25% higher, as production costs are less.
Organic cotton growers in Texas also get yields similar to conventional farms, according to Textile Exchange, and the organic seeds cost only $70 per bag compared to $400 for GMO seeds.
Also, there are savings in water use. “An average sized t-shirt resulted in a savings of 1,982 gallons of water compared to the results of chemically grown cotton,” notes La Rhea Pepper, the Managing Director of Textile Exchange.
One of the main challenges of growing cotton organically is that it needs twice the number of days as conventional cotton.
Cotton (Gossypium spp) belongs to Malvaceae and grows in tropical to subtropical climates. Cotton needs temperatures around 86 degrees Fahrenheit, plenty of sunshine, and at least 500 mm of rainfall. Cotton doesn’t tolerate waterlogging, so soils should be well-drained. The crop needs rich soil and does well in black soils, but can be grown in sandy areas.
Usually, 30% of flowers result in bolls, but drought, pest, waterlogging, or low temperatures can bring this figure down to 10%.
To optimize growing conditions, the following organic cultivation methods are recommended, and Figure 1 shows the best timing for each operation.
- Correct selection of varieties
- Manure and minerals for nutrient application
- Crop rotation
- Controlling biotic stress
Figure 1: Timing of different operations and the growth cycle in organic cotton. (Image credits: Aboutorganiccotton.org)
Though seed selection is an important strategy to enhance cotton yield, 80% of farmers, globally, have problems finding organic varieties.
Most farmers use hybrids created for conventional farming as GMO seeds are not considered organic.
Several non-hybrid varieties that can be multiplied by farmers are being produced, but the progress is slow. In countries where GMO cotton seeds are allowed like the USA and India, contamination of seeds due to cross-pollination from neighboring fields growing GMO crops remains a challenge.
Growers must keep in mind the soil type and depth while selecting varieties.
Deep-rooted varieties are high-yielders and have long fibers and are suitable for deep black soils. Hybrids resistant to common pests like bollworms, aphids, miners, and jassids make these hybrids
- The American Upland a hybrid of Gossypium hirsutum used in the US
- Sea Island cotton from Gossypium barbadense
- H-10 and JHK-1 in India
Local varieties available in countries like India are suitable for shallow soils.
In the US, the recommended cotton population is 40,000 to 45,000 plants per acre, with seeds planted in 38-40-inch rows.
The aim is to have “approximately 3-4 living plants per foot,” according to the Mississippi State University Extension Service. “Planters should always be calibrated to deliver a specified number of seed per foot of row and "NOT" a specified number of pounds of seed per acre.”
In India, the seed rate is recommended depending on the soil type and availability of irrigation.
- Narrow spacings of 2 x 2 feet for light soils and farms with little irrigation
- Broad spacing of 4 x 4 feet for heavy soils and properly irrigated farms
In Egypt, cotton is planted with an inter-row spacing of 70 cm (27 inches) and intra-row spacing of 20 cm (eight inches).
Cotton needs fertile soils, but farmers should not try to use natural alternatives at fertilizer dosages recommended for conventional farms. Instead, the focus should be to build soil fertility and improve storage of nutrients through crop rotation, intercropping, mulching, and manures.
The total nutrients that cotton should get are:
- Nitrogen (N) : 100-120 kg/ha
- Phosphorus (P) : 50-60 kg/ha
- Potassium (K) : 40-50 kg/ha
Manure restores soils that have lost fertility and structure due to the continuous use of chemicals. The humus encourages the growth of beneficial soil micro-flora and fauna which make the soil looser and also help in nutrient cycling. The manure will also supplement missing nutrients.
Two-thirds of the manure should be added during the first two months. The timings can be:
- A basal dosage of manure or farm compost during sowing
- One-two head applications of oil cakes and poultry manure 2-3 weeks before the start of square bud formation, as this is the time needed for the release of nutrient from oil cakes
Besides manure, crop residues, and compost, additional sources for
- P are rock phosphate and wood ash
- K are muriate of potash and wood ash
- N are nitrogen fixation from legume cover crops and vermicompost
According to the Organic Cotton Crop Guide, biodynamic farms also need:
- 125 g/ha of BD 500
- 5 g/ha of BD 501
- 125 g/ha of CCP
Farmers can further boost soil fertility by aiding natural soil processes. There are many ways to do this:
1. Add microbial fertilizers, that is formulations that contain various beneficial bacteria, usually species of Bacillus. They increase soil nutrient content and their utilization by plants, and bind soil granules and improve structure. They can also produce various phytohormones that leak into the soil promoting root growth.
Moreover, “through competition, parasitism, occupation, and other relationships, they can inhibit and reduce the propagation opportunities of pathogenic bacteria,” says Darren Chan.
2. Use mycorrhizae, a type of fungus that lives in the soil and increases plants’ access to water and nutrients. One way to increase them is to grow cover crops before or with cotton.
“The cover crops act as a host plant for arbuscular mycorrhizal fungi, which are microbes that have a direct effect on plant health and nutrient storage capacity of the soil within the root zone of the plant,” says Pat Rogers.
Cotton has to be rotated with other crops to be called organic. The three-year cycle, recommended in Figure 2, serves to:
- Improve soil structure by alternating short and long-rooted crops
- Cereals loosen the soil with their shallow fibrous roots
- Grains with deep roots like corn add organic matter to deeper layers of soils
- Prevent depletion of nutrients at the same soil depth and enhance fertility
- Legumes will increase nitrogen content in the soil
- Vegetable crops are known to have high carryover nutrients when manure is added, reducing the need to supplement nutrients for succeeding crops
- Avoid population build-up of weeds, pests, and diseases. The University of California Agriculture and Natural Resources (UCIPM),
recommends crop rotation to decrease the severity of bollworms, nematodes, and pathogens causing Verticillium wilt, seedling diseases, etc.
Figure 2: Recommended crop rotations. (Image credits: Infonet biovision)
One of the crops that should be included in the crop rotation is cover crops that can provide green manure adding organic matter and nitrogen to the soil. Cover crops build soil fertility by breaking down soil carbon and helping in nutrient cycling through exudates.
Green manure crops can also be used as intercrop and planted after cotton emerges. These are cut before or during flowering to provide mulch or are incorporated into the soil to provide manure.
In the tropics, sun-hemp or cowpea are used as green manure. Small pulses like black gram, cowpea, moong dal, and small grains are allowed to mature and harvested for pulses and grains. The planting rate is usually 5kg of green manures/ ha in India.
Growing more than one crop at the same time increases crop diversity and is another pillar of organic farming that is beneficial for cotton.
Legumes included as intercrops add nitrogen to the soil for cotton. Other crops decrease pests and diseases spread by localizing them. Being unsuitable hosts, the second crop functions as a barrier for the movement of pests and pathogens.
Trap plants can be grown as border crops or also as intercrop as every ninth row in between cotton. They protect the cotton from pests by acting as alternate hosts.
Border crops could be sunflower and carob; or also be plantations of banana, coffee, cassava, and mango, that provide indirect benefits of shade and soil fertility, or provide income at different times of the year to a farmer.
Cotton requires large quantities of water and is often irrigated. Rainfed crops require at least 1000 mm of rainfall in the tropics.
Use precision and smart farming methods to closely monitor the water status of the soil and its impact on the cotton crops to decide the timing and amount of irrigation to minimize water use and yet optimize plant growth.
In India, farmers plant a local croton, to act as an early indicator of drought stress to irrigate cotton crops.
New precision equipment needed for irrigation can be used with old machinery too.
In the tropics, water use is reduced through drip irrigation, which also allows farmers to start early. However,
In general, in the first 6-7 weeks, the watering should be moderate to prevent too much vegetative growth and to let deeper roots develop.
- Using the microbial fertilizers, like Bacillus mucilaginosus to improve soil structure and increase water retention and reduce irrigation needs
- Shallow hoeing to break the soil capillaries to decrease evaporation
The main sources of biotic stress in cotton are pests and diseases, and weeds to a lesser extent.
Leaf sucking insects are the main problem, however, once the
- Common boll pests are the American bollworm, pink bollworm, spotted bollworm, spiny bollworm, and cutworms
- Leaf sucking pests are the aphids, whitefly, spider mites, cotton stainer, and thrips
A combination of crop rotation, intercropping, and Integrated Pest Management can help in the biological control of pests.
Scouting should be a regular and ongoing process until harvest to spot the insects early to take preventive measures. Here again, precision farming methods to detect pest stress can be useful. Growers in smaller tropical farms walk their fields.
There are well
Large farms can use variable rate application machinery to use permitted natural pesticides, such as neem spray. In addition to commercial pesticides, many natural self-made sprays of garlic extract, wood ash, flour, soft soap, milk, sulfur, lantana leaf extract, giant milkweed (Calotropis procera) are used depending on the pests.
Natural enemies like disease-causing microbes are also used. For example,
- NPV (nuclear polyhedrosis virus) against American bollworms
- Bacillus thuringensis Bt spray for leaf-eating caterpillars
- Beauvaria bassiana, a fungus against cutworms and budworms
Soil-borne diseases are a major cause of yield reduction. The common diseases that threaten cotton are the bacterial blight, which affects leaves, stem, and causes boll shedding, and root and boll rot caused by fungus and bacteria.
Cow urine spray is used as a treatment in India for blight and rots. Trichoderma viride is a biocontrol method to control wilt, blight, and root rot. “It should be used in the soil, and avoid spraying on the stems and leaves,” recommends Darren Chan.
Wilt can be also controlled by cultural practices such as crop rotation, removing the previous cotton stalks residues, and using clean seeds not infected by the disease.
Weeds are a problem only in the initial stages of cotton. Once the crop is established, its canopy controls the growth of weeds. In the tropics, many weeds act as trap plants for pests.
Weeds can be controlled by:
- Crop rotation and cover crops to prevent weed establishment
- Shallow but timely soil cultivation with hoes and weeders in the initial stages
- Hand weeding to control early outbreaks of weeds
In the US, where cotton farms can be 200-400 hectares large, harvesting is done with cotton strippers or pickers. In the tropics, the cotton is usually hand-picked.
Closing the Demand and Supply Gap
Certification of cotton is necessary as much of the trade in organic cotton is international. Though the demand for organic cotton is increasing, nearly 30% of cotton certified as organic has to be sold as conventional ware. This gap in marketing needs to be fixed to encourage more farmers