Tomato Residue Retention Alters Soil Nutrient and Organic Acid Composition, Influencing the Rhizosphere Microbial Community and Metabolic Profile of Subsequent Crops

To enhance the benefits and ecological safety of tomato residue retention, this study evaluated the regulatory effects of conventional ambient temperature retention (CR) and solar high-temperature retention (TR) on the initial soil environment and rhizosphere microecology of subsequent crops (continuous tomato and rotational cucumber). The results showed that CR promoted the accumulation of humic acid and increased the contents of phenolic acids and small-molecule organic acids in the soil. TR also increased small-molecule organic acids but primarily enriched fulvic acid, accompanied by higher concentrations of phenolic acids. Regarding microecological responses, CR enriched potential plant-growth-promoting bacteria (Pseudomonas, Sphingomonas, Lysobacter) in the rhizosphere, but it also increased the relative abundance of the potential pathogen Fusarium. In contrast, TR promoted the colonization of heat-tolerant beneficial biocontrol microbes (Bacillus, Chaetomium, Mycothermus), with no Fusarium enrichment observed. Redundancy analysis and Mantel tests revealed that the changes in soil nutrients and organic acid fractions induced by residue retention were correlated with the succession of the rhizosphere microbial community and the reconstruction of the metabolic profile. This study demonstrates that TR can effectively mitigate the risk of pathogen enrichment associated with ambient temperature retention, constructing a potentially disease-suppressive initial microecological environment for subsequent crops.