Abstract:

Wind erosion is a key factor of soil quality reduction in agro-ecosystems in arid area, and winter crop coverage can effectively reduce soil wind erosion. This study aims to construct a suitable annual cover crop rotation pattern based on the effect of different winter cover crop rotations integrated with green manure multiple cropping on soil carbon and nitrogen in Hexi irrigation area. A field experiment was carried out in spring wheat region of Hexi irrigation area where the temperature conditions were surplus for one season of crop but insufficient for two seasons of crop. The experiment was conducted with four rotation patterns of nested planting (WCP: spring wheat—winter rape—common vetch; WWP: spring wheat—winter wheat—common vetch; WP: spring wheat—common vetch; W and CK: spring wheat—spring wheat) and three nitrogen levels (N2: 360 kg/hm², N1: 270 kg/hm², N0: 0 kg/hm²). The effects of different crop rotation patterns on soil carbon and nitrogen content were analyzed. The results showed that the content of soil organic carbon, soil soluble organic carbon, thermally extracted organic carbon, nitrate nitrogen, ammonia nitrogen and microbial biomass carbon and nitrogen increased with the nitrogen application rate under the same rotation pattern. In WCP rotation mode, N1 did not decrease the content of soil organic carbon, soil soluble organic carbon, soil thermally extracted organic carbon and microbial biomass nitrogen, respectively, compared with N2. Under the condition of the same nitrogen application rate, the difference among the rotation patterns was not significant, but they significantly differed from CK. Among them, in 0-10 cm soil layer, WCP rotation mode increased the average content of soil organic carbon, soil soluble organic carbon, soil thermally extracted organic carbon, nitrate nitrogen, ammonia nitrogen, microbial biomass carbon and nitrogen by 5.42%, 9.78%, 10.96%, 20.51%, 15.76%, 18.94% respectively compared with CK; in 10-30 cm soil layer, the above indexes increased by 9.54%, 7.06%, 12.99%, 20.12%, 16.51%, 18.16%, respectively. Therefore, under the condition of nitrogen reduction, the spring wheat and winter rape rotation integrated with green manure multiple cropping pattern (WCP) has significant effect on improving farmland soil carbon and nitrogen, which is an appropriate annual cover crop rotation pattern in Hexi irrigation area.

Key words: crop rotation, winter mulch, winter rape, green manure, soil organic carbon