Review of the technology for high-yielding and efficient cotton cultivation in the northwest inland cotton-growing region of China

The northwest inland is currently the most dominant cotton-growing region in China. In 2015, the region measured 2.3 million hectares with a total output of 4.28 million tons of cotton. The unit yield was 1900 kg hm−2, which was not only 21, 41 and 121% higher than the national averages of China, Brazil and the United States, respectively, but also 2.37 times as much as that of the world's average. Enhanced cotton production, particularly the high unit yield, can largely be attributed to the adoption of a series of key cultivation techniques. These techniques, including earliness-stimulating cultivation for full utilization of accumulated heat, close planting and short plant height for adequate use of light energy, and drip irrigation under plastic mulching for water saving and yield improvement, have been recently established and applied in the northwest inland of China. At the same time, a series of labor and cost-saving technologies or practices have been adopted to increase net production returns. Mechanization and precision seeding has greatly reduced labor inputs, rational high-density planting techniques combined with chemical regulation has simplified plant pruning and harvesting, and the integrated application of water and fertilizer has reduced the inputs and costs in field management. In particular, the integration of these agronomic techniques and material equipment has not only enhanced yields, but is also convenient, cost-effective and simple. These factors have all led to the establishment of the northwest inland as the largest predominantly cotton-growing area in China. However, the region is currently facing major issues including stagnated cotton yields, serious plastic film pollution, continuous degradation in fiber quality, substantial increases in the cost of cotton production and continuously declining profits. These factors necessitate that cotton cultivation strategies in the region need to be further optimized. Yields can be enhanced by exploring heat and water potential, while quality and economic benefits can be improved by exploring light potential, fertigation and integrating agronomic techniques with mechanization. Greater attention should be paid to seed quality and seeding processes to further reduce costs and improve efficiency. Comprehensive steps for improving the cultivation system at all stages of production should also be taken to enhance the quality of the cotton fiber.