Effect of cropping system on cotton biomass accumulation and yield formation in double–cropped wheat–cotton

Wheat–cotton double cropping practices on a large scale in cotton belt of the Yellow RiverValley and the Yangtze River Valley in China. Field experiments were conducted to determinethe effects of wheat–cotton double cropping on cotton biomass accumulation and yieldformation during 2011/12 and 2012/13 growing seasons. Two cotton cultivars, Siza 3 (mid–latematurity) and CCRI 50 (early maturity), were used in three cropping systems includingmonoculture cotton (MC), wheat/intercropped cotton (W/IC) and wheat/direct–seeded cotton(W/DC). Lint yield in double cropping systems were significantly lower than that inmonoculture. Compared with MC for Siza 3, lint yield in W/IC and W/DC were decreased by10.9 and 41.8%, respectively and 9.9 and 35.9% for CCRI 50, respectively. These reductionswere largely ascribed to the fewer cotton bolls per unit area. Growth analysis showed that ICshowed a pronounced delay in early development due to the initial shading from wheat oncotton seedlings and owing to delayed sowing, DC was easily affected by lower temperatureduring flowering and boll formation stage. And that consequently was delaying reproductivedevelopment, affecting cotton biomass accumulation and distribution and finally limiting cropproductivity. Further, the diminished source capacity coupled with inadequate biomassproduction was the main determinant factor to limit lint yield in W/IC, while the reduced sinkcapacity with less partition to reproductive organs was the primary factor limiting lint yield inW/DC. Comparing to mid–late maturity of Siza 3, early maturity cultivar of CCRI 50 had ayield advantage in double cropping sequential system, since its shorter growing period.