Drip irrigation frequency influences the composition of soil microbial communities and enzyme activities, and improves the growth and yield of long-season cultivated tomatoes

Protected vegetable production relies on drip irrigation for precise water and fertilizer delivery, which modifies the root zone microenvironment and microbial structure to influence yield and quality. In this study, compared with the conventional water and fertilizer treatment as a control (CK1), by using the tomato nutrient solution of Yamazaki, equal quantities of water and fertilizer were provided over a 12-d cycle, but with differing frequencies among the groups: every 12 d (CK2), 6 d (T1), 4 d (T2), and 2 d (T3). Results showed stem diameter and net photosynthetic rate were 4.1%, 4.9%, 5.5%, and 2.5% and 37.1%, 7.9%, 9.7%, and 8.9% higher in T2 than in CK1, CK2, T1, and T3, respectively. The root surface area and root volume were 59.0%, 62.1%, 29.1%, and 16.3% and 34.1%, 43.4%, 25.1%, and 17.0% higher in T2 than in CK1, CK2, T1, and T3, respectively. Furthermore, the yield was 12.2% higher in T2 than in CKl, and WUE was 12.2% higher in T2 than in CKl. The richness and diversity of bacteria were higher in T2 than in CK1, and the abundance and diversity of fungi were inversely related. The abundance of the genera Sphingomonas, Arthrobacter, and Ramlibacter increased, whereas that of Mycothermus decreased. Network and correlation analyses demonstrated that microorganisms and enzyme activities could interact to enhance the capacity of root systems to acquire nutrients from the soil. The present findings will aid the development and use of drip irrigation strategies in tomato cultivation in protected areas.