Optimal drip-irrigation amount improving cotton yield and land-use efficiency in jujube-cotton intercropping system of southern Xinjiang

Abstract: In recent years, with the development of agriculture in southern Xinjiang, water and land resources shortage is increasingly prominent. Water-saving irrigation methods to efficiently use water resources and increase farmers' income have been proposed by Xinjiang Production and Construction Corps. Meanwhile, land resources and crop planting structure are adjusted and characteristic wood's fruit industry is developed. Jujube-cotton intercropping system in southern Xinjiang is a new type of agroforestry systems. It is unclear about the effect of jujube-cotton intercropping system with drip-irrigation on cotton growth and land use efficiency and the related mechanisms. This study aimed to investigate the influence of drip-irrigation quota on growth, yield and land use efficiency of cotton in jujube-cotton intercropping system. A field experiment was conducted in 2012 and 2013 using a randomized complete block design with jujube planting spacing of 1 m × 3 m, cotton planting spacing of 0.25 m × 0.60 m, and cotton and jujube spacing of 0.95 m. Drip-irrigation quota was 450 (GM-1), 750 (GM-2), and 1050 m3/hm2 (GM-3) for intercropping system and 750 m3/hm2 for cotton (CK-M) and jujube (CK-Z) monoculture. The stem height, diameter, aboveground dry matter, and yield of cotton were measured. The land equivalent ratio and system productivity index were calculated. The results showed that the cotton stem height was highest in the GM-3 among all treatments, and not significantly (P>0.05) different between GM-1 and GM-2. The changes in the stem diameter were similar with the height. The GM-3 treatment could adversely affect the cotton aboveground dry matter accumulation, but the GM-1 and GM-2 had similar role in increasing the cotton aboveground dry matter accumulation. The land equivalent ratio in the intercropping system was larger than 1, and greater than the monoculture system. For the two years of the experiment, the GM-2 treatment had the steadily highest land equivalent ratio and yield. Land use efficiency in jujube-cotton intercropping system was higher than the monoculture system. In addition, the system productivity index of GM-2 was relatively higher than the other treatments. In the intercropping system, the jujube was easily affected by irrigation amount and thereby its yield and productivity could be affected. The treatment of GM-2 could increase the production potential of jujube. The jujube-cotton intercropping system had a higher capacity to withstand market risks. In summary, the irrigation of 750 m3/hm2 had high land use efficiency and thus could be favorable to cotton growth and land use. The study suggested that optimal production capacity could be reached through reasonable irrigation in intercropping system. The results provided valuable information for the water resource use, and efficient land use in southern Xinjiang..