Effects of planting pattern on growth and yield and economic benefits of cotton in a wheat-cotton double cropping system versus monoculture cotton

The double-cropping system of wheat and cotton is widely adopted in the Yellow River Valley of China, but it remains unclear if and how planting patterns impact cotton yield and economic benefits in this system. Using monoculture cotton (CM) as the control, we conducted a 2-year field experiment to investigate the effects of three planting patterns, cotton intercropped with wheat (CIW), cotton transplanted after wheat (CTW), and cotton direct-seeded after wheat (CDW) under the wheat-cotton double cropping system on cotton growth, yield and economic benefits in two fields differing in soil fertility. The results indicated that double cropping significantly decreased cotton yield relative to monoculture irrespective of planting pattern and fields, but the decrements were considerably reduced in the high soil fertility field. Averaged across two years, cotton yields of CIW, CTW and CDW were reduced by 16.2, 30.0 and 38.8% in the low fertility field relative to that of CM, while they were reduced by 7.5, 22.4 and 22.7% in the high fertility field. The yield difference among planting patterns was attributed to the variation in both the number of bolls and boll weight, while the yield difference between two fields was largely due to the number of bolls. Similar differences in biomass accumulation were observed among planting patterns. Accelerated early development of cotton, extended duration of the fast biomass accumulation and the enhanced total biomass and accumulation rate were observed in the high fertility relative to those in the low fertility field. Economic analysis showed that, based on total costs and output values of two crops, the net revenue of CIW, CTW and CDW was increased by 28.5, 10.9 and 36.5% in the low fertility field; and by 56.3, 31.8 and 74.4% in the high fertility field, compared to CM averaged by two years. CDW might be a new alternative for cotton production in Yellow River Valley when taking both profitability and management simplification into consideration. Our results also support that good soil fertility is a prerequisite for high yield and net return in wheat-cotton double cropping, especially for CDW.