Effect of long-term no-tillage with stubble on soil fertility and diversity of prokaryotic microbiome in dryland wheat soils on the Loess Plateau, China

In dryland regions, conservation tillage has the advantages of reducing soil erosion, maintaining soil structure, improving soil physical and chemical properties, and promoting microbial reproduction, compared with traditional farming methods. Up to now, the effect of long-term conservation tillage on soil prokaryotic microbial community has not been adequately reported for the China's Loess Plateau region. To understand the effects of long-term conservation tillage on soil prokaryotic microbial community diversity and soil fertility in dryland wheat fields on the Loess Plateau, the Illumina Hiseq 2500 high-throughput sequencing and physicochemical test methods were used to analyze the effects of different tillage measures on soil physical and chemical properties and the diversity of soil prokaryotic microbial community in the wheat fields in Linfen City, Shanxi Province. Tillage measures adopted in the study area for 26 years included no-tillage with stubble (NTS), no-tillage with stubble after subsoiling (SNTS) and traditional tillage (TT1). The results showed that:1) while soil contents of total nitrogen, available nitrogen, available phosphorus, available potassium, and soil water storage capacity and water content under NTS and SNTS treatments were significantly higher than those under TT1, soil pH under NTS and SNTS was lower than that under TT1. NTS and SNTS treatments reduced soil bulk density in the 0-10 cm soil layer, but increased it in 10-20 cm soil layer compared with TT1 treatment. Meanwhile, SNTS treatment significantly increased soil organic matter content. 2) The results of the Illumina Hiseq high-throughput 16S rRNA gene sequencing in area Ⅴ4 indicated that:SNTS treatment significantly reduced the relative abundance of Chloroflexi, compared with TT1 treatment. NTS treatment significantly reduced the relative abundance of Verrucomicrobia and Chloroflexi, compared with SNTS treatment. NTS treatment significantly increased the diversity of soil prokaryote community, but not significantly changed the abundance of prokaryote community. SNTS treatment not significantly changed the diversity and richness of prokaryote community. Biomarkers under NTS treatment were higher than under other treatments. The relative abundance of other prokaryotes at the phylum division was not significantly different among three treatments. 3) UPGMA analysis showed that prokaryote community structures of NTS and SNTS were significantly different from those of TT1, and the differences between NTS and SNTS were small. 4) CCA analysis showed that soil pH, contents of organic matter, available nitrogen, available phosphorus and available potassium were important for changes in genetic diversity of soil prokaryote communities. Although NTS and SNTS treatments could change soil prokaryotic microbiome structure greatly, there was still structural similarity among the soil prokaryotic microbiomes among three treatments. To sum up, long-term conservation tillage had obvious positive effects on soil microbial diversity, richness and soil fertility in dryland wheat fields on the Loess Plateau.