Fundamentals for improving cotton crop
By Dr Shahzad M.A. Basra, Hassan Munir & M. Tariq Javed
DESPITE being one of the leading cotton producers, Pakistan ranks 13th in the world in the yield per acre. As a result, around 1.5 to 2.00 million bales of cotton are imported annually to meet the demand of the domestic textile industry, contributing 60 per cent of the export earnings. Therefore, it is necessary to increase the per acre yield.
There are a number of strategies to increase the yield and to reduce cost of production. These include efforts to minimise high temperature effects on cotton crop as well as for optimum crop stand to maximise yield. Every cotton grower is making efforts for better yield as it offers a lot of economic benefits.
Useful cotton textile products include terrycloth, used to make highly absorbent bath towels and robes, denim to make blue jeans, chambray used in the manufacture of blue work shirts (from which we get the term blue collar), corduroy, seersucker, and cotton twill. Socks, underwear, and most T-shirts are made from cotton. Bed sheets are usually made of cotton. Cotton yarn is used in crochet and knitting.
Fabric can also be made from recycled or recovered cotton. While many fabrics are made completely of cotton, some are made with materials blended with cotton as well as with other fibres, including rayon and synthetic fibres such as polyester.
In addition to the textile industry, cotton is used in making fishnets, coffee filters, tents and in bookbinding. The first Chinese paper was made of cotton fibre. Fire hoses were once made of cotton. Cotton hulls are used for fertiliser, fuel, and packing. The cottonseed is used to produce cottonseed oil, which after refining is used by human beings. The cottonseed meal is generally fed to livestock.
Successful cultivation of cotton requires a long growing season, plenty of sunshine and water during its period of growth, and dry weather for harvest. In general, these conditions are met within tropical and warm subtropical areas. Production of cotton crop for a given year usually starts soon after harvesting the preceding autumn. Planting time is between April and June ..
A "good stand" refers to the number of healthy, vigorous seedlings that are evenly distributed in the field. This may be two to four plants per foot of row depending on soil type, row width, planting date, and moisture during the growing season. Getting a stand requires proper seedbed preparation, favourable soil temperature, proper planting depth, adequate soil moisture, high quality seed, avoiding chemical injury and protecting the plants from high winds, blowing sand, insects and diseases.
Seed quality should be the top most concern of the cultivator. Poor seed is the primary cause of stand failure. Emerging seedlings are poorly equipped to withstand the challenges of diseases, insects, wind, and weather, including moisture stress and heat stress.
Only such seeds should be sown which have a cool-warm vigour index of 155 or higher. The vigour index is obtained by combining the warm germination test percentage with the cool germination test percentage. Under favourable conditions, emergence of seedlings can occur in four to five days after planting. Emergence will take longer if seed are planted in cool soils. Temperatures below 60°F are detrimental to germination, emergence, and seedling growth. During the first 60 to 100 hours of germination, the radical tip is easily damaged by chilling, lack of oxygen in the soil, or too much moisture. If the tip is killed, a shallow system of secondary roots develop that makes the plant more subject to moisture stress latter in the season.
For better germination and enhanced vigour, better quality seed is the pre-requisite. Under normal soil conditions, simple soaking of seed in water before sowing will serve the purpose. Experiments have shown that primed seeds emerged faster and grew more vigorously. They also flowered earlier (very important in drought-prone areas), matured earlier and gave higher yields.
Deterioration of cotton seed during storage is another problem. During storage various seed-born micro-organisms damage the seed. As a result the seed loses viability and germination capacity. In this scenario seed invigoration techniques offer a new hope.
At present, seed-priming has been commercially used to eliminate or greatly reduce the amount of seed-borne fungi and bacteria. Organisms such as Xanthomonas campestris in canola and cotton seeds and Septoria in celery have been shown to be eliminated within seed lots as a by-product of priming. In the case of Xanthomonas campestris in cotton, zero infection in 50,000 seeds is commonly reported. The mechanisms responsible for eradication may be linked to the water potentials that seeds are exposed to during priming, differential sensitivity to priming salts, and/or differential sensitivity to oxygen concentrations.
Cotton plant is highly sensitive to high temperature. It dries out, becomes hard and brittle and loses all elasticity at temperatures above 35°C. Extended exposure to light causes similar problems. A temperature range of 35°C to 45°C is the optimal range for fungus development. Because of high temperature these problems are frequently observed in cotton growing areas of southern Punjab and parts of Sindh.
The ideal daytime temperature for cotton production is 82 degrees Fahrenheit. In Multan and other cotton-producing areas, daytime temperatures often exceed 100 degrees Fahrenheit. Plant physiologists are of the view that high temperatures can adversely affect the function of plant enzymes, resulting in impaired photosynthesis and reduced yields of cotton as well as other crops.
To overcome high temperature problem in cotton, research activities are in progress at the University of Agriculture, Faisalabad, to address the high temperature as well as poor crop stand problem in cotton crop. However, due to some obstacles, collaboration with other leading national institutes like Pakistan Atomic Energy Commission (PAEC), Islamabad, National Institute for Biotechnology and Genetic Engineering (NIBGE) and Nuclear Institute of Agriculture and Biology (NIAB), Faisalabad, Central Cotton Research Institute (CCRI), Multan, and National Centre of Excellence in Molecular Biology (NCEMB) at Punjab University, Lahore, is need of the time.
Authorities should pay attention for developing this collaboration and should also encourage these research efforts for better outcomes. This is the only way by which we can play our role in improving cotton production and increasing the crop yield in the country.
http://www.dawn.com/2007/07/23/ebr4.htm
