紫云英与油菜混播对稻田土壤N2O排放及相关功能基因丰度的影响

目的]探究绿肥混播对稻田土壤N2O的减排效果和机制,筛选既高产稳产,又减排的适合南方双季稻区发展应用的绿肥混播种植模式.方法]比较不同紫云英与油菜混播比例(单播紫云英(CK1)、单播油菜(CK2))、3/4紫云英+1/4油菜(3/4M+1/4R)、1/2紫云英+1/2油菜(1/2M+1/2R)、1/4紫云英+3/4...

Effects of the Mixted-cropping of Chinese Milk Vetch and Rape on Soil Nitrous Oxide Emission and Abundance of Related Functional Genes in Paddy Fields

【Objective】The aim of this study was to determine how a green manure mixted-cropping affected nitrous oxide (N₂O) emissions from soil and the abundance of related functional genes in paddy field soil. The ultimate aim of this research was to identify a green manure mixted-cropping that had high and stable yields and reduces emissions, and was suitable for cultivation in the double-rice areas of southern China. 【Method】The effects of mixted-cropping of Chinese milk vetch and rape at different ratios (single Chinese milk vetch, single rape, 3/4 Chinese milk vetch +1/4 rape, 1/2 Chinese milk vetch +1/2 rape, and 1/4 Chinese milk vetch +3/4 rape) on N₂O emissions and the abundance of related functional genes in paddy field soil were determined and compared. 【Result】(1) The crop species affected N₂O emissions. The N₂O emissions were similar among the different treatments. Among them the N₂O emissions from winter crop soil were mainly concentrated at its flowering stage, and those during the rice growing period were concentrated at the tillering, filling, and maturity stages of early and late rice crops. On the whole, the N₂O emissions from paddy fields were lower N₂O in the early rice season than that in the late rice season. The overall N₂O emissions flux in the paddy fields was higher in 2018 than that in 2019. (2) There was no significant difference in N₂O cumulative emission of early rice under different treatments. The cumulative N₂O emissions from a single seeding treatment were lower than those from mixed treatments over two consecutive years. The annual cumulative N₂O emissions were lowest under CK1 in 2019. Among all the mixed treatments, the 3/4 Chinese milk vetch +1/4 rape treatment had the lowest annual cumulative N₂O emissions. (3) In general, the copy number of amoA-AOA and amoA-AOB genes was higher in the soil of late rice than that in the soil of early rice, and the copy number of AmoA-AOA was up to two orders of magnitude higher in late rice soil than in early rice soil. The copy numbers of nirS, nirK and nosZ were higher in the soil of late rice crops than that in the soil of early rice crops, and the copy number of nirS was up to two orders of magnitude higher than those of nirK and nosZ in late rice soil. The mixted-cropping of Chinese milk vetch and rape increased the abundance amoA-AOA and amoA-AOB genes in soil, and amoA-AOA was the dominant functional gene. It also increased the abundance of nirS, nirK and nosZ genes in soil, and nirS gene was the dominant gene. The copy number of genes related to denitrification was one to three orders of magnitude higher than the copy number of genes related to nitrification, indicating that denitrification made a larger contribution to N₂O emissions. 【Conclusion】Overall, the 3/4 Chinese milk vetch + 1/4 rape-early rice-late rice was the best mixed planting system, because it had the best combination of low N₂O emissions as well as high yield and high fertility.