Water-fertilizer regulation improves yield, quality, and water-fertilizer use efficiency of greenhouse lettuce by altering the bacterial community in nutrient solutions

In response to the challenges of limited water and soil resources, sustainable agricultural practices must balance productivity with environmental preservation. This study concentrated on greenhouse lettuce, investigating the impact of varying irrigation lower limits (40%, 55%, 70%, and 85% of field capacity) and nutrient solution concentrations (50%, 75%, 100%, and 125% of Hoagland’s solution) on yield, quality, water-fertilizer use efficiency, and microbial communities within the nutrient solution. Results showed that lettuce growth improved with higher irrigation limits and peaked at moderate nutrient concentrations, with the W85N100 treatment achieving the highest yield and quality. Both irrigation lower limits and nutrient solution concentrations exhibited notable impacts on the Alpha and Beta diversity of bacteria within the nutrient solution. However, irrigation lower limits (R 2 = 0.221) exerted a stronger influence on bacterial community composition compared to nutrient solution concentrations (R 2 = 0.19). Through null model analysis, it was revealed that the bacterial community assembly transitioned from a random-deterministic equilibrium to a stochastic process as lettuce growth advanced. Redundancy analysis identified that nutrient indicators served a pivotal function in shaping bacterial community structures within the nutrient solution. Random forest modeling further predicted that bacterial communities, especially during the middle stage of cultivation, had a strong relationship with lettuce yield and quality. Three beneficial bacterial genera, namely Bosea , Ferribacterium , and Acinetobacter , were associated with the enhancement of lettuce yield and quality, correlating positively with available potassium, nitrate, and total nitrogen, respectively. These bacteria contributed to improving yield and quality through mechanisms such as nitrogen fixation, phosphorus removal, and involvement in nutrient cycling. The study’s findings provide valuable insights into the mechanisms by which water-fertilizer regulation can enhance the efficiency and quality of greenhouse lettuce production, offering new scientific evidence to support the sustainable development of greenhouse vegetable cultivation. • The lower limit of irrigation has a significant impact on the composition of bacterial communities. • Nutritional indicators drive the construction of bacterial community (except for AP). • Bose , Ferribacter , and Acinetobacter are positively correlated with lettuce growth.