Ecological and economic benefits of planting winter rapeseed (Brassica rapa L.) in the wind erosion area of northern China.

Winter and early spring wind soil erosion have considerable impacts on ecosystems, human well-being and agricultural production in the low precipitation zones of northern China. Little is known about the impact of growing winter rapeseed on ecological cropping systems and the associated economic benefits in the wind erosion area. To explore the winter rapeseed cover effect, we conducted a field experiment in which we covered the soil with winter rapeseed, winter wheat and wheat stubble at different plant density levels and used the spring bare ground as the control (CK). The effects of wind erosion, the "winter rapeseed + " multiple cropping system, and the economic benefits were compared. There was a large difference in the dry matter, the maximum water absorption, the maximum water storage, the soil evaporation and total wind erosion, the amount of sediment transported in the stratum and the wind erosion modulus. Among them, the mean wind erosion modulus of spring sowing bare land was as high as 490.9 kg·hm-2·h-1, which was 7 and 13 times that of winter wheat and winter rapeseed, respectively. As the wind speed increased from 14 to 22 m·s-1, from a small density to a large density, the mean wind erosion modulus decreased from 68 to 17 kg·hm-2·h-1 for winter rapeseed, and 150 to 31 kg·hm-2·h-1 for winter wheat. Total wind-erosion of sediment transport of CK was 18.6 g·m-2 min-1, which was 16 and 31 times the mean value of winter wheat and winter rapeseed, respectively. "Winter rapeseed + " replanting peanuts, potatoes, rice, seed melons and other crops generally increased the production value by 5-74% compared with wheat and corn intercropping, which was 98-255% higher than the traditional wheat single crop. Our results suggested that the suitable area for planting winter rapeseed in northern China was approximately 3.3 × 106 hm2, and in terms of the best economic and ecological effects, the appropriate density was 5 × 105 plants·hm-2 in northern China. Our results indicated that Chinese winter rapeseed was the best choice for preventing wind erosion and improving ecological and economic benefits in winter and spring in northern China; additionally, winter rapeseed has important impacts on agricultural sustainability in semi-arid and arid climates.