Different no-till grain production systems with Urochloa spp.affect soil microbial community structure,biomass and activity in a tropical Ultisol

Integrated grain cropping systems promote soil health(SH)and sustainability.Microbial biomass and activity(MBA)and community structure(MCS)are key to SH.Integration of maize with Urochloa pastures strongly impacts MBA and MCS.MBA is more sensitive than MCS to shifts in grain cropping systems.Systems under continuous Urochloa increased microbial activity and AMF abundance.Tropical soils are prone to degradation.Adoption of conservation agricultural practices is essential to improve soil health,which is influenced by soil microbes.In this study we analyzed shifts in microbial biomass and activity(MBA)and microbial community structure(MCS)based on fatty acid methyl esthers(FAMEs)between five no-till agricultural practices:maize monoculture(MM);maize annualy intercropped with Urochloa decumbens(M/Ud);M/Ud with soybean rotation every other year(M/Ud-S);M/Ud keeping the pasture for the next two years(M/Ud-Ud-Ud);and maize intercropped with U.ruziziensis keeping the pasture for the next two years(M/Ur-Ur-Ur).Results indicated that MBA was affected by the inclusion of Urochloa intercropping and by rotation with soybean.Systems under a longer residence time with Urochloa in the field had higherβ-glucosidase activity and soil basal respiration,indicating a greater microbial activity.MCS was less affected than MBA by the investigated cropping systems.MCS changed only in the continuous pasture systems,which were enriched in arbuscular mycorrhyzal fungi(AMF).Additionally,the continuous pasture systems had lower microbial stress ratios than the other agricultural practices.In sum,our study showed that utilization of Urochloa spp.under longer periods in no-till agricultural practices contributes to increase microbial activity,AMF abundance and decrease microbial stress ratio.These changes are primarily beneficial for soil health.