Long-term mulched drip irrigation facilitates soil organic carbon stabilization and the dominance of microbial stochastic assembly processes

• Published in: Agricultural water management Vol. 302; p. 109008
• Main Authors: Liu, Jieyun, Qiu, Husen, He, Shuai, Tian, Guangli
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2024; Elsevier
• Subjects: Ascomycota; Assembly processes; Bacterial and fungal communities; Basidiomycota; carbon dioxide fixation; Carbon stabilization; catechol oxidase; cotton; Enzyme activities; fungi; microirrigation; mulching; Oligotroph/copiotroph ratios; soil organic carbon; soil salinization; subsoil; topsoil; water management; Enzyme activities; Oligotroph/copiotroph ratios; Assembly processes; Bacterial and fungal communities; Carbon stabilization
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/j.agwat.2024.109008

Mulched drip irrigation (MDI) is generally accepted as a method to decrease soil salinization and improve crop yields in arid and semi-arid regions. However, there remain gaps in how MDI drives soil organic carbon (SOC) dynamic microbial assembly processes with time, and the mediating role of microorganisms remains unclear. In this study, we investigated the aforementioned issues across soil profiles in cotton fields with different years of MDI. The results showed that MDI did not cause the differences in SOC, particular organic carbon (POC), and mineral-associated organic carbon (MOC) in soil layers. The POC and MOC contents had a parabola relationship with time, and showed an opposite trend in soil. After 15 years of MDI, the ratio of MOC/SOC increased to a peak value of 50 % and 52 % in topsoil and subsoil, respectively; the ratio of POC/SOC decreased to valley values of 50 % and 48 %, respectively (P < 0.05). Long-term MDI reduced the differences in oxidase between soil layers but accelerated SOC loss by increasing polyphenol oxidase activity (P < 0.05). Compared with that of other years, with 10 years of MDI, bacterial Shannon diversity decreased to a valley value, and fungal Shannon diversity reached to a top value in subsoil (P < 0.05). In general, stochastic processes were mainly controlled by dispersal limitation, and undominated processes dominated microbial assembly; however, there was a close relationship between bacterial communities and organic carbon fractions. The high percentage of positive linkages among microorganisms indicated that long-term MDI was beneficial for carbon fixation. Additionally, a decrease of fungal oligotroph/copiotroph ratio, the relative abundance of Ascomycota and Basidiomycota was beneficial for the accumulation of SOC and POC in topsoil (P < 0.05). In conclusion, long-term MDI is useful for the fixation of organic carbon via improving soil POC content and strengthening linkages within community assemblies. •The content of MOC increased with prolonging of MDI.•Long-term MDI weakens the effect of soil depth on microbial community structure.•Bacterial and fungal community assemblies were dominated by stochastic processes.•Long -term MDI decreased soil TDS, and increased MOC by improving PPO activity.•Fungal oligotroph/copiotroph ratio regulates SOC fractions in topsoil.