Effects of Continuous Cropping and Two Alleviating Agents on Root Yield and Active Constituents of Salvia miltiorrhiza

Salvia miltiorrhiza (SM) is an important annually harvested herb, with the roots being important medicinal tissues. The occurrence of continuous cropping (CC) obstacles hampers the development of SM roots and leads to yield loss. To reveal the different responses of SM varieties to CC, we investigated root yield and active compound content of six SM germplasms that were potted in the second year of replanted soil. A space-bred variety Hangtian No. 1 (HT) was cultivated to examine the effects of marigold dry straw and an anticontinuous cropping biofertilizer in alleviating SM CC obstacles. The results showed that three SM varieties─LD and two white flowering varieties─were reduced by about 50% under CC conditions, whereas HT, HN, and SL exhibited no significant root yield reduction, compared to controls. High-performance liquid chromatography-based quantitation revealed that the active compounds of six SM varieties were affected differently by CC, but all met the minimum quality requirement of SM. Two levels of marigold and biofertilizer failed to increase HT root yield under CC conditions. However, the contents of polyphenolic acids and tanshinones were increased by these alleviating agents. Our research suggested that further optimization of alleviating strategies should focus on the improvement of SM root yield in replanted soil.