Responses of Soil Microbial Community Characteristics And Enzyme Activities To Different Irrigation Modes Over Four Wheat-Maize  Rotation Seasons

Abstract

Water scarcity in arid and semiarid areas highlights the importance of developing water-saving irrigation techniques. Soil extracellular enzyme activities (EEAs) and microbes are important for biochemical cycles and plant growth. However, little is understood about how soil EEAs and microbial communities respond to water-saving irrigation regimes. Therefore, in the present study, a field experiment was carried out over four consecutive wheat-maize seasons to explore the effects of surface irrigation (SI) and drip irrigation (DI) coupled with different irrigation amounts (65 mm/event, adequate irrigation; 50 mm/event, mild deficit irrigation; 35 mm/event, moderate deficit irrigation; 20 mm/events, serious deficit irrigation) on the plant biomass, soil properties, soil extracellular enzyme activities (EEAs) and bacterial communities. The results revealed that mild deficit irrigation showed no significant influence on plant biomass, soil properties, EEAs and bacterial communities. Serious and moderate deficit irrigation significantly decreased crop biomass, but increased soil available K accumulation and soil urease activity compared with sufficient irrigation. Drought stress induced by serious deficit irrigation shifted the bacterial community structure, but did not influence its diversity. The relative abundances of Firmicutes, Gemmatimonadota and Myxococcota significantly increased under serious deficit irrigation, while Acidobacteriota and Methylomirabilota significantly decreased. Moderate deficit irrigation under DI did not shift bacterial community structure, while under SI did. Soil pH, electrical conductivity (EC), available K and plant biomass were the major factors influencing the bacterial community compositions. Serious deficit irrigation reduced the complexity and stability of soil bacterial co-occurrence network. Network of DI had more significant interactions among bacterial than the SI. Under moderate deficit irrigation, DI is more beneficial to maintain crop yield and the stability of bacterial community structure than SI.

Keywords: drip irrigation, Deficit Irrigation, Soil enzyme activities, Bacterial communities, Co-occurrence networks