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 River Valley and the Yangtze River Valley in China. Field experiments were conducted to determine the effects of wheat-cotton double cropping on cotton biomass accumulation and yield formation during 2011/12 and 2012/13 growing seasons. Two cotton cultivars, Siza 3 (mid-late maturity) and CCRI 50 (early maturity), were used in three cropping systems including monoculture 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 in monoculture. Compared with MC for Siza 3, lint yield in W/IC and W/DC were decreased by 10.9 and 41.8%, respectively and 9.9 and 35.9% for CCRI 50, respectively. These reductions were largely ascribed to the fewer cotton bolls per unit area. Growth analysis showed that IC showed a pronounced delay in early development due to the initial shading from wheat on cotton seedlings and owing to delayed sowing, DC was easily affected by lower temperature during flowering and boll formation stage. And that consequently was delaying reproductive development, affecting cotton biomass accumulation and distribution and finally limiting crop productivity. Further, the diminished source capacity coupled with inadequate biomass production was the main determinant factor to limit lint yield in W/IC, while the reduced sink capacity with less partition to reproductive organs was the primary factor limiting lint yield in W/DC. Comparing to mid-late maturity of Siza 3, early maturity cultivar of CCRI 50 had a yield advantage in double cropping sequential system, since its shorter growing period.