Combining Subsurface Pipe Drainage With Organic Fertilization to Improve the Microbial Community Composition of Saline–Alkaline Soils for Sustainable Agriculture

Subsurface pipe drainage (SPD) has been widely studied as an effective strategy for alleviating the adverse effects of soil salinization. However, the effects of the combined application of SPD and organic fertilization on soil microbial characteristics in severely saline–alkaline soils remain unclear. A field experiment was accordingly conducted in this study to explore how different combinations of SPD and organic fertilization treatments comprising CK (SPD at a depth of 1.5 m), CM (cattle manure treatment at 37.0 Mg·ha −1 and CK), and BCM (biofertilizer treatment at 4.5 Mg·ha −1 , cattle manure treatment at 30.0 Mg·ha −1 , and CK) affect the physicochemical properties and microbial community composition of a saline–alkaline soil. The CM and BCM treatments significantly decreased the electrical conductivity of the soil by 14.5%–17.3% and the exchangeable sodium ion contents by 33.8%–36.2% compared with the CK, whereas the exchangeable calcium ion content significantly increased by 22.3%–45.2%, particularly for the BCM treatment. Furthermore, the CM and BCM treatments exhibited microbial biomass carbon and nitrogen contents that were 51.8%–68.3% and 27.2%–33.8% higher, respectively, than those of the CK treatment; similarly, their dissolved organic carbon and nitrogen contents were 24.1%–34.7% and 40.3%–48.1% higher, respectively, than those of the CK treatment. As a result, both the CM and BCM treatments enhanced soil microbial diversity and richness towards taxa responsible for decomposing organic matter (e.g., Acidobacteria and Gammaproteobacteria ), which was most likely due to the greater levels of DOC/MBN and lower levels of exchangeable sodium ions. Thus, the combination of SPD with organic fertilization, particularly biofertilizers, is an effective approach for improving saline–alkaline soil environments to realize sustainable agriculture.