COTTON, which is also known as ‘white gold’, is an important crop in many developing countries. The yield of the crop is dependent upon the environment in which it is grown and the management practices of the cropping system.
Cotton yields are stagnant for the last several years. Factors responsible for the stagnant cotton production include: excessive rain at the time of sowing, high temperature at flowering stage, late wheat harvesting resulting in decline of area under the crop, leaf curl virus incidence, soil system, weather adversaries, pest attack and improper production technology in major cotton growing areas of Punjab and Sindh. There are many social as well as economic problems facing cotton production including, illiterate farming community, high cost of inputs, small landholdings, less adoptability of innovations by the farmers, lack of guidance to farmers, high cost of production and insecurity in the market, the cost of production being the most significant among them.
In recent past two major factors had a significant impact on the economics of cotton production. They are extensive use of agrochemicals and yield stagnation. Among all agrochemicals, fertilisers and insecticides are of utmost importance. There are no efficient alternatives to synthetic fertilisers and cotton production has to bear the use of nutrient supplements in the form of inorganic fertilisers. Among pesticides, insecticides are group of agrochemicals which is extensively used on cotton.
Insects, being living organisms, have adjusted with the injurious chemicals and learned to survive with insecticides. Consequently, insecticide use kept increasing causing a serious impact on the economics of cotton production. Currently, there is a greater need for new developments in production research but more and more researchers are confronted with maintaining the current status of yields in their countries. The cost of production has increased to unacceptable levels in many countries that threaten the economics of cotton production.
Cultural Problems: There are also many aspects which can affect fibre quality and yield. Agronomic practices affecting the yield include sowing time, low quality and adulterated seed, timing of harvest, irrigation, use of plant growth regulators, soil fertility, tillage, and cultivar selection.
Currently cottonseed must be delinted to be used in modern planting equipment. The two most common methods are wet acid delinting using sulphuric acid and gas delinting using hydrogen chloride. There are several possible problems associated with acid delinting including damage to seed quality by improper procedures during the acid delinting process, damage to the seed by ammonia during the neutralisation process, worker safety concerns, and disposal issues.
Seed germination: Seed dormancy is a significant factor involved in germination of cotton crop. Additionally, some forms of cotton may produce ‘hard seeds’ that, upon drying, become impermeable to water and suffer delayed germination. Priming improved emergence and early growth of maize and cotton in drying soils in the laboratory. On-farm seed priming can partly compensate for the negative effects of low soil water potential and large aggregate sizes on crop establishment. Some studies have shown that conservation-tillage systems can also decrease cotton yields by increasing soil compaction and reducing water availability.
Pests: Cotton is a pest-loving plant and due to this habit it has become a problematic crop for the farmers. More than 1326 species of insects have been reported in commercial cotton fields worldwide but only small proportions are pests. Of the 30 pests of cultivated cotton the most important are the caterpillars of pink, spotted and American bollworms, aphids, whitefly, jassids, mealy bugs and the spider mite.
The bollworm/budworm complex is a primary insect pest problem with larvae attacking squares and bolls causing significant yield losses if left uncontrolled. The cotton whitefly is a pest of primary importance for fibre, horticultural and ornamental crops worldwide. It can cause extensive damage through direct feeding, honeydew production and as a viral vector.
Pink hibiscus mealy bug is an emerging threat to the cotton crop. Its host records extend to 76 families and over 200 genera, with some preference for Fabaceae, Malvaceae and Moraceae. Growing points infested with cotton mealy bug become stunted and swollen. This varies according to the susceptibility of each host species. Plant protection products are of limited effectiveness against the bug because of its habit of hiding in crevices, and the waxy covering of its body.
Poor spraying techniques and over-use of chemicals has led to the pest becoming resistant to most of the available insecticides. Seeing their crops devastated by bollworms, and desperate to salvage something from their losses, farmers have continued to buy more toxic (and expensive) chemicals and to spray more frequently, but with decreasing effectiveness.
Diseases: Never has a single pathogen or insect pest threatened Pakistan’s cotton culture, as has the cotton leaf curl virus (CLCuV). In 1993-94, about 0.89 million hectares were badly damaged resulting about two million bales loss in production due to CLCuV. In economic term, the country had suffered a loss of about 7.6 million bales, which costs to the tune of Rs71 billion since 1988 due to the infestation of CLCuV. Yield decreased from1.938 million metric tons in 1991 to 1.445 million metric ton in 1992 and fell further to 1.105 million metric ton in 1993.
Recently, cotton leaf curl virus has again emerged as a key disease in the province of the Punjab in general and Burewala area in particular. The re-emergence of virus commonly called as Burewala Strain of Cotton Virus (BSCV) has dangerous version and could develop into a serious problem.
The continued use of CLCuV-susceptible varieties without any programme of their replacement constitutes a major risk for cotton production in Pakistan. So a premier focus should be given to eliminate the CLCuV disease and a well-planned programme of evolution and introduction of CLCuV-resistant varieties of desired characteristics must be in place to gradually replace the existing CLCuV-susceptible varieties. This is only the sole and the most promising and least expensive method of disease suppression.
Other important diseases are seedling diseases caused by the fungi Pythium and Rhizoctonia, Black root rot, Fusarium wilt and Verticillium wilt, Alternaria Leaf spots and Bacterial blight.
Abiotic stresses: Water deficit, in conjunction with high temperatures and incident radiation, poses the most important constraint to plant survival and crop productivity. Cotton crop was affected by drought and there was yield reduction of 1.1per cent during the year 2003. Drought stress causes severe shedding of small squares, resulting in a decrease in flowering. An understanding of the response of plants to water deficits is important in efforts to model cotton growth, estimate irrigation needs, and breed drought-resistant cultivars.
Although the cotton plant is a “sun-loving” plant, an excessively higher temperature at reproductive phase (above 36oC) decreases its production significantly. According to an estimate, cotton plant sheds about 65–70 per cent of its fruiting points due to heat-induced sterility, spotted bollworm attack and increased humidity during monsoon. High temperature disrupts the movement of water, ion, and inorganic solutes across the plant membrane, which interferes with photosynthesis and respiration. Clearly, an increase in high temperature at the reproductive phase is the major factor of low productivity of cotton varieties grown in the cotton belt of Pakistan.
Soil and fertility: Several soil conditions and farming practices in Pakistan are perceived as being likely to induce micronutrient deficiencies, including high soil pH, calcareousness of soils, low soil organic matter and use of fertilisers poor in micronutrients. Boron contents of soils and plants from light and medium textured soils were less than the critical levels. High soil pH, calcareousness and low organic matter in such soils might be rendering the B less available to the plants.
There may be less availability of phosphorus (P) in a rapidly drying soil due to reduced P diffusion and poor uptake by roots. This may result in inadequate P nutrition for cotton plants.
Nutrient-poor, degraded, and often acidic, soils limit crop production in many tropical regions. Limiting amounts of phosphorous and excessive levels of aluminium are characteristic problems of acidic soils.
Saline soils are found naturally in many locales and have been created in others by poorly managed irrigation. Both the timing and method of application of fertiliser are important, though some evidence suggests that one method may be better than the other under particular circumstances, most of the literature suggests that timing of applications of fertilizer is a much more important determinant of yield response than method of application.
Salinity affects large areas of irrigated land, and is a particular problem in NW India and in Pakistan, where it is often combined with water-logging. The two stresses together have far more severe effects than either alone: root ability to screen out salt is much reduced, and lack of O2 leads to metabolic problems.
In Pakistan, about 6.3 million hectare was affected by salinity, and groundwater in most of these saline areas is brackish and thus unfit for irrigation. So current cropping intensities and groundwater usage in irrigated agriculture are not sustainable due the problem of salinity.
Environmental and health hazards: During July-March, 2005-06, 17,900 and 36,000 tons of agricultural pesticides were imported and locally formulated and most of them were applied on cotton. Chemical pesticides affect human health as well as biological diversity and surface and groundwater quality. Some pesticides leave persistent residues in soil, groundwater, and the food chain, thus exposing human population to slow and cumulative poisoning (WTO).
Pesticides also affect wildlife, domestic animals, and biological diversity. Pesticide poisoning remains a daily reality among agricultural workers in developing countries, where up to 14 per cent of all occupational injuries in the agricultural sector and 10 per cent of all fatal injuries can be attributed to pesticides.
Marketing: Between 1960–64 and 1999–2003 real cotton prices fell by 55 per cent, quite similar to the 50 per cent decline in the broad agriculture price index of 22 commodities. The grower-to-market links are usually absent, and the research-extension-grower links essential to the transfer of technology are often weak.
It is found that the incidence of poverty among cotton growers could rise in the short run from 37 per cent to 59 per cent while the average incidence of rural poverty could rise from 40 per cent to 48 per cent. So it appears that cotton growers are heavily taxed both directly, through the lower prices received by the state company which purchases cotton and indirectly through the (likely misaligned) exchange-rate regime. This assessment is shared by a recent report which concluded that only one third of the world price of cotton reaches the producers.
Strategies and prospects: Considering such a high importance of the cotton crop in the national economy, the problems and issues pertaining to this crop should be very carefully evaluated and monitored.
The main objectives of government are overcoming the scarcity of water through augmentation and conservation means i.e. by construction of medium and large dams and by efficient utilisation of irrigation water, restoring the productivity of agricultural land through control of water logging, salinity and floods.
The government should also provide farmers with the credit facilities that they might be able to purchase good quality inputs to raise high yielding stands of the crop. Threshold-based sprays against the main pests, the use of a cotton growth regulator, and earliness of cotton cultivar and seed treatment are accountable for savings in pesticide sprays. Bt cotton varieties should be locally developed and distributed among the farmers to avoid the high incidence of bollworms.
There are various management practices that should be followed to help mitigate some of the environmental risks associated with growing cotton. They include selection of adapted cultivars, planting within the recommended range of favourable planting dates and environmental conditions, use of seed and seedling protectants to avoid stress or early season diseases and insects, use of effective pest management tactics to avoid competition and damage by weeds and insects, management for optimal soil moisture, proper fertility management, and management for maturity and readiness for harvest at optimum times.
One of the tools used in reducing environmental risks and increasing the possibilities of a profitable yield is cultivar development through breeding and genetics. Breeding for heat, salinity and water logging tolerance accompanied with higher percentage of seedlings will emerge to produce even and uniform plant stands. Grower-to-market and the research-extension-grower links are essential to avoid farmer against the clutches of middleman and to the transfer of technology.
Courtesy: The DAWN