关键词: 宏基因组学, 有机肥, 盐碱土, 氮循环, 功能基因

Abstract: Exploring the regulatory impacts of organic fertilizer application on nitrogen cycling and analyzing the synergistic pathway between microbial community and functional genes can provide theoretical basis for sustainable improvement of saline alkali soil. We conducted a 4-year wheat experiment (2018-2022) at Nanpi Ecological Agriculture Experimental Station of the Chinese Academy of Sciences, with two treatments: chemical fertilizer (compound fertilizer with N:P₂O₅:K₂O=18:22:5) and organic fertilizer (decomposed cattle manure organic fertilizer was applied at the same amount of nitrogen). Through conventional nutrient analysis and high-throughput macro genome sequencing technology, combined with Mantel test and functional gene association analysis, we analyzed the impacts of organic fertilizer on the microbial community involved in nitrogen transformation in saline alkali soil and its regulation mechanism. The results showed that compared with chemical fertilizer treatment, the application of organic fertilizer significantly increased the total nitrogen and alkali hydrolyzed nitrogen content of the topsoil by 26.9% and 34.5%, respectively, while the nitrate content significantly decreased by 28.3%. The application of organic fertilizer significantly increased the ACE index, but did not affect the Shannon index. The organic fertilizer treatment increased the relative abundance of the salt-tolerant genus Pseudolabrys by 517.0%, altered the microbial community structure, increased the abundance of the nitrate reductase gene (napA) and denitrification genes (norB and nosZ), as well as the relative abundance of glutamine synthetase. The Mantel test revealed that the relative abundance of the false double headed axe shaped fungus genus was significantly positively correlated with soil total nitrogen, alkaline nitrogen, and ammonium nitrogen contents. Similarly, the abundance of the norB gene showed significant positive correlations with these three nitrogen indicators. Our results demonstrated that organic fertilizer alleviates nitrogen limitation in saline-alkali soils and altered the nitrogen metabolism network through altering key microbial taxa and functional gene abundance.

Key words: metagenomics, organic fertilizer, saline-alkali soil, nitrogen cycle, functional gene