Technologies and theoretical basis of light and simplified cotton cultivation in China

Since the beginning of the 21 st century, the rapid economic development and accelerated urbanization of China have caused major changes to the country's cotton cultivation technology. China has not replicated the completely mechanized approach used in developed countries. Rather, taking into account the underdeveloped economy and family-scale based cotton growing, China has established and implemented a light and simplified system of sustainable cotton production. Light and simplified cultivation (LSC) involves using modern agricultural equipment and technology adapted to the local economic level and mode of management of cotton production instead of manual operations. This method reduces labor intensity, simplifies cultivation management, reduces the frequency of field operations, integrates agricultural machinery and agronomic technology, and uses high-quality seeds and improved techniques to achieve light, simplified, and cost-effective cotton production. Cotton LSC includes the following key technologies: Single-seed precision sowing, simplified plant pruning, light and simplified fertilization, water and fertilization integration technology, and plant population structure control. Single seed precision sowing technology ensures robust seedling growth via differential expression of the key genes controlling hook formation and hypocotyl elongation at seed germination. Cotton planting at a relatively high plant density inhibits the growth of vegetative branches via differential expression of genes for hormone metabolism and compartmentation of hormones within a cotton plant. The high and stable yield of LSC lies in the adaptive coordination between the cotton yield components and between the biomass and the harvest index. According to the appropriate leaf area index and its dynamics, quantitative indicators such as suitable plant height, the ratio of fruiting nodes to branches in number, and the ratio of seed cotton to stalks in weight can produce plant populations with high solar efficiency. The basis of light and simplified fertilization is that the absorption of fertilizer N by cotton is concentrated within 20 days after flowering, and the fertilizer applied at early flowering was mainly distributed to reproductive organs and had higher N use efficiency than that applied at other stages. The water saving mechanism of partial root-zone irrigation is that methyl jasmonate serves as a signal substance to enhance the water absorption from the hydrated root side. Future development of cotton cultivation must include an in-depth investigation of the ecophysiology of LSC to further reform and optimize the planting systems and patterns. Innovation in cultivation technologies, development of new materials and equipment, and integration of agronomic technology and materials may provide solid theoretical and technical support for LSC and promote the sustainable cotton production in China.