The efficiency of adjusting nutrient solution renewal frequency on physicochemical properties and microbial community of cucumber exudates under closed cultivation tank.

The closed nutrient solution management method allows for the recycling and utilization of nutrient solutions, improving the efficiency of water and fertilizer utilization. This study was conducted to investigate the effects of changing the frequency of nutrient solution renewal and method of nutrient supply on the microbial communities composition, yield, and quality in closed soilless systems by using high-throughput sequencing technology and combining the physicochemical properties of root exudate solution. The results showed that different nutrient solution management modes had a significant impact on the structure and diversity of root exudate solution microbial communities. The abundance and diversity of microorganisms in inorganic perlites were correlative with EC. The abundance and diversity of bacterial communities in the root exudate solution of open liquid supply (CK) were higher than that of closed liquid supply, while the abundance and diversity of fungal communities in the root exudate solution of closed liquid supply (T1, T2, T3) were higher than that of open liquid supply. As the frequency of nutrient solution interval decreased, the accumulation of salt in root exudate solution and the richness and diversity of the fungal community also decreased, especially increasing the K+, Ca2+, and Mg2+ contents, which were positively correlated with potential beneficial Candidatus_Xiphinematobacter, Arachidicoccus, Cellvibrio, Mucilaginibacter, Taibaiella communities and decreasing the content of soluble protein, Vitamin C content, but not significantly increased cucumber yield.