Effect of crop rotation system on diversity and community structure of soil microorganisms with nifH gene in Panxi Plateau, China

Abstract:

[Background] A few studies of the effect of rotation system on the community structure and diversity of soil nitrogen-fixing microorganisms on plateau are available. [Objective] To clarify the effect of rotation system on farmland soil fertility and diversity and community structure of soil microorganisms with nifH gene on Panxi Plateau and screen a reasonable rotation system. [Methods] Soil samples were collected from five crop rotation systems: 15-year Vicia villosa Roth-flue-cured tobacco rotation (G1), 20-year V. villosa -flue-cured tobacco rotation (G2), tartary buckwheat (Fagopyrum tataricum)-flue-cured tobacco rotation (KQ), barley (Hordeum vulgare L.)-flue-cured tobacco rotation (DM), and abandoned soil (CK) in Mianning county, Liangshan prefecture. Through chemical analysis and high-throughput sequencing of nifH, soil physico-chemical properties and community structure and diversity of soil nitrogen-fixing microorganisms were analyzed. [Results] The total nitrogen content, ammonium nitrogen content, nitrate nitrogen content, organic carbon content, and water content were the highest in the CK (P <0.05) and the pH value was below 7 in all rotation systems. Under KQ, content of soil available phosphorus and available potassium was 43.0% and 2.60% higher, respectively. Soil physico-chemical parameters were lower under DM rotation than in CK. Soil nitrogenase activity was highest in CK and lowest under G2. The diversity of nitrogen-fixing microorganisms was the highest under G1 and lowest under G2. At the phylum level, the relative abundance of Proteobacteria was the highest, accounting for 63.0%-92.4% of the total abundance. At genus level, Azohydromonas dominated the soils under crop rotation and Bradyrhizobium was most abundant in CK. Redundancy analysis revealed that soil pH and water content were the key factors driving the composition of soil nitrogen-fixing microorganisms. [Conclusion] Rotation systems obviously changed the soil fertility and the composition of nifH gene community, particularly the G1 which improved soil nutrient content and diversity of soil nitrogen-fixing microorganisms.