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 CO2 emission and decreased the CH4 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.