Effects of ridge-furrow mulching system and limited supplementary irrigation on soil microbial community structure, function and carbon emissions

Limited supplementary irrigation under the ridge-furrow mulching planting technology (R) is an important high-efficiency water-saving agricultural measure promoted in the dryland area. To systematically clarify the mechanism of R and supplementary irrigation on soil microorganisms and carbon emissions in farmland, this study investigated dryland farming systems under R with three irrigation amount, using traditional planting (T) as the control, the effects of different irrigation on soil microbial community structure, carbon cycle function gene diversity, carbohydrate-active enzymes and carbon emissions were explored. The results showed that R and supplementary irrigation significantly changed the carbon emission. R increased the CO 2 emission and decreased the CH 4 absorption. It increased the microbial richness but had no significant impact on species diversity, Sphingomonasy and Nocardioides were dominant bacterial groups in farmland. The functional gene diversity of carbon cycle and carbohydrate-active enzymes were studied, in the same irrigation treatment, the Ace and Shannon index of carbon cycle function genes in R increased by 0.05 %-4.85 % and 0.48 %-3.86 % compared with T. The abundance of GTs and GHs under R increased by 3.20 %-20.97 % and 0.68 %-14.00 %, while the CEs family decreased significantly by 34.72 %-36.31 %. Pearson analysis indicated that the cultivation patterns and supplementary irrigation mainly affected farmland carbon emissions by influencing shannon index of carbon cycle functional genes, bacterial Lysobacter, carbohydrate-active enzymes GH74 and PL22 . The results of this study can provide a scientific basis for a deeper understanding of the microbial-mediated carbon cycle process under the R with limited supplementary irrigation in dryland farming areas. • Limited irrigation under ridge-furrow mulching system(R) lead to more C emission. • The R improved soil microbial richness but had no obvious impact on species diversity. • Amount of supplementary irrigation affected microbial community randomness. • 4. The R improved the abundance of carbon cycle functional genes and carbohydrate enzyme. • 5. The main bacteria/enzymes driving the production of CO 2 were obtained.