Dry-wet alternation influenced microbial community structure in the apple root zone

Soil water management is a key factor influencing the soil microenvironment. This study aimed to investigate the effects of the dry-wet alternating irrigation regimen on the growth of apple roots (two-year-old potted Red 'Fuji' apple), the composition of the rhizosphere microbial community, and the transformation of soil nitrogen, using stable dry and stable wet treatments as controls. The results showed that the dry-wet alternating irrigation significantly promoted apple root growth, with increases in root length, root weight, and total nitrogen content ranging from 20.66% to 40.94%, 56.19% to 134.80%, and 84.33% to 190.03%, respectively. Furthermore, the diversity and structure of the microbial community within the rhizosphere and roots were modified by the dry-wet alternating treatment. Specifically, this treatment led to a 93.03% increase in rhizosphere microbial abundance compared to the stable dry treatment, while concurrently reducing denitrification microbial abundance by 55.34% compared to the stable wet treatment. This shift contributed to increased soil available nitrogen content, with average enhancements of 16.88% for NH4+-N and 96.45% for NO3--N. Overall, the results from the partial least squares pathway model (PLS-PM) indicated that varying soil water states significantly influenced the interactions within the soil-microorganism-plant system, underscoring the importance of these findings for informing water management practices in orchard settings.