Eggplant (Solanum melongena L.) is one of nutritious vegetables welcomed by consumers. However, the diseases occurred on eggplants, particularly soil-borne diseases became increasingly severe, which hampered sustainable development of eggplant production. Based on our investigation, eggplant rotation is able to reduce the occurrence of diseases significantly, but its mechanism has not been explained clearly.
In this study, we collected soil samples from different fields cultivated by eggplant continuous cropping and rotation to analyze their nutrients, enzymatic activities and microbial community structure using high throughput sequencing technique.
The results showed that the contents of available P, Ca, Mg and Mn decreased significantly, and the activities of polyphenol oxidase (PPO), urease (UE), alkaline protease (ALPT) decreased; the number of bacterial operational taxonomic units (OTUs) reduced but fungal OTUs increased, and the bacterial and fungal diversity indexes decreased and the dominance index increased in fields with four-year continuous cropping (eggplant-eggplant-eggplant-eggplant, EEEE), as compared with different eggplant rotation fields. However, there were significant differences in the nutrients, enzymatic activities and microbial community structure from different soil samples between the four-year eggplant rotation fields [eggplant-rice-rice-eggplant, ERRE or eggplant-green bean (the early half of the year)+bottle gourd (the latter half of the year)-green bean (the early half of the year)+bottle gourd (the latter half of the year)-eggplant, EGBE] as well. Compared with the EGBE, the pH and the contents of total P, available P, exchangeable Ca, Mg and Mn increased significantly, but the salinity and available boron (B) reduced significantly; the activities of peroxidase, acid protease, neutral protease decreased significantly but the catalase, UE and ALPT increased significantly; the number of bacterial OTUs increased significantly but fungal OTUs decreased; the bacterial and fungal diversity indexes increased and the dominance indexes decreased in ERRE.
In sum, ERRE is a good and worthy way for rotation by comprehensively considering soil pH, salinity, nutrients, enzymatic activities and microbial community structure in this study. The above results lay a theoretical foundation for choosing suitable cultivation system of eggplants in mountain regions.