不同冬季覆盖作物轮作对农田土壤碳氮影响

Effects of Different Winter Cover Crop Rotations on Farmland Soil Carbon and Nitrogen

风蚀是干旱区农田生态系统中土壤质量降低的关键因素,冬季作物覆盖可有效减少农田的土壤风蚀。通过探究河西灌区不同冬季覆盖作物轮作复种绿肥对农田土壤碳氮影响,以期为构建合理的周年覆盖轮作模式提供理论依据。本研究在热量一熟有余两熟不足的河西灌区春小麦种植区把冬小麦、冬油菜两种冬季覆盖作物和绿肥还田处理嵌套种植形成:(1)春小麦—冬油菜—箭筈豌豆(WCP)、(2)春小麦—冬小麦—箭筈豌豆(WWP)、(3)春小麦—箭筈豌豆(WP)、(4)春小麦—春小麦(W,CK)不同种植模式,在360 kg/hm^(2)(N2)、270 kg/hm^(2)(N1)、0 kg/hm^(2)(N0)3个施氮水平下,研究不同轮作模式对农田土壤碳、氮含量的提升效应。结果表明:在同一种植模式下土壤有机碳、土壤可溶性有机碳、热提取态有机碳、硝态氮、氨态氮、微生物量碳氮含量随施氮量的增加而增加,但在氮肥减量(N1)的条件下,与常规施氮(N2)相比较WCP轮作模式土壤有机碳、土壤可溶性有机碳、热提取态有机碳含量及微生物量氮无显著降低。相同施氮条件下,轮作模式间差异不显著,但与CK间差异显著;其中,0~10 cm土层,WCP轮作模式土壤有机碳、土壤可溶性有机碳、土壤热提取态有机碳、硝态氮、氨态氮、微生物量碳氮含量平均较CK提高5.42%、9.78%、10.96%、20.51%、15.76%、18.94%;10~30 cm土层,提高9.54%、7.06%、12.99%、20.12%、16.51%、18.16%。因此,春小麦轮作冬油菜复种绿肥模式在氮肥减量条件下仍对农田土壤碳氮有明显的提升效应,为河西灌区良好的周年覆盖作物轮作模式。

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/hm;, N1: 270 kg/hm;, N0: 0 kg/hm;). 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 by9.54%, 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.