Abstract:
Objective Continuous cropping resulted in soil microbial deterioration and serious soil-borne diseases. Earthworms could improve soil quality, however, there are few studies on the effect of earthworms to alleviate continuous cropping obstacles. This study determined how earthworms affected soil microecology and watermelon growth and the underlying mechanisms in the watermelon-earthworm co-culture pattern.
Method Based on a six-year watermelon continuous cropping system, three treatments were selected: no earthworms (CK), inoculated Eisenia fetida with 0.6 kg m−2(T1), inoculated Pheretima guillemi with 0.6 kg m−2 (T2). The changes of soil microecology nutrients, physicochemical properties, allelochemicals, microorganisms, and watermelon growth in different periods were monitored, and the correlation between them was analyzed.
Result The results showed that soil total nutrients and available nutrients of T1 and T2 were significantly higher than CK (23.92%-31.90%, 10.67%-13.70%, respectively) at the transplanting period of watermelon seedlings. Compared with CK, T1 and T2 significantly reduced soil pH (2.03%-8.25%), total phenolic acid (23.98%-60.80%), bulk density (3.79%-5.39%), the number of F. oxysporum f. sp. niveum (22.93%-59.18%), and significantly increased the number of bacteria and the ratio of bacteria to fungi. At the same time, T1 and T2 significantly promoted the growth of watermelon (the incidence of Fusarium wilt was reduced by more than 10.00%, and the length of the main vine was increased by more than 71.43%) compared with CK. Compared with T1, T2 was more effective in alleviating continuous cropping obstacles. Correlation analysis showed that soil microorganisms were the primary factor for earthworms to alleviate watermelon continuous cropping obstacles.
Conclusion Earthworms significantly improve soil microecology and promote the growth of watermelon, which will alleviate continuous cropping obstacles. Moreover, soil microecology and watermelon growth are closely related to soil microorganisms.