Cotton lint yields across the globe range from 180 to 2600 kg/ha but yields are low in Africa at 180 to 550 kg/ha and India at 480 to 550 kg/ha. While the yields in Australia were higher than 1,500 kg/ha after 2001, four major cotton growing countries, namely, Mexico, Brazil, China and Turkey have been harvesting more than 1,500 kg/ha in recent years. While yields in these five countries and a few major Mediterranean countries have been increasing constantly over the past two to three decades, yields in Africa have been stagnant for more than 25 years. The world average yields were about 770 kg/ha after 2004. However, the world average yields (without India and Africa) were above 1,000 kg/ha over the past 10 years.
High yields in the subtropical region appear to be due to two major factors; 1) strategic breeding plans for the development of new varieties that are adaptive for the local climate and 2) scientific advances in agronomic management practices. The new varieties were of compact architecture, short duration (130-160 days), high harvest index and suitable for machine picking with a narrow critical window (flowering to green boll formation) of 40-60 days that is crucial for the management of water, nutrients and bollworms. Agronomic practices ensured proper availability of water, nutrients and solar radiation in addition to improvisation of integrated pest management. However, countries in the tropical region have been growing long-duration (160-210 days) varieties that are bushy and have low harvest index. Such varieties have a long (80-100 days) critical window of management that makes it difficult to obtain high yields without intensive input management and high costs.
India and Africa could emulate the ‘high yield’ success stories of Australia, Turkey, Brazil, China and Mexico by experimenting breeding strategies for the development of short-duration varieties with compact architecture and high harvest index, coupled with canopy management and better management practices to enhance ‘water use efficiency (WUE)’, ‘nutrient use efficiency (NUE) and pest management.
Would like to add conscious efforts to improve GOT also as a part of the strategic breeding programme. But given the fact that reorienting the breeding programmes would take time to yield results, a proper diagnosis and characterisation of the soil and agro-eco system would help in identifying and validating and refining the agro-techniques to improve yields in the tropical regions in short run