Legacy effects of preceding crops improve flue-cured tobacco productivity in southwest China by optimizing soil structure, nutrients, and microbial interactions

The use of legume crops and garlic as preceding crops has positive effects on soil quality and crop yield. However, little is known about how preceding crops optimize and regulate the interactions among soil microbial communities, soil quality, and crop production.

We conducted a long-term 7-year field experiment under three cultivation systems (continuous cropping, faba bean and tobacco rotation, and garlic and tobacco rotation). Soil samples were collected to test the physical, chemical, enzyme and microbiome.

Compared with continuous cropping, crop rotation significantly improved the stability of soil aggregates, nitrogen and phosphorus contents, and acquisition efficiency of soil nutrients. Redundancy analysis confirmed that significant changes in soil microbial community structure were caused by the preceding crops. This increased the modularity, complexity, and information transfer efficiency of the microbial molecular ecological network. Legacy effects of preceding crops significantly increased tobacco yield (24.13–31.75%) and output value (31.31–44.96%). Compared with the preceding crop of faba bean, garlic has more advantages in promoting soil aggregate stability, carbon cycling efficiency, the abundances of Chloroflexi, Bacteroidetes, and Ascomycota, and the yield and output value of tobacco. Moreover, Mantel tests and partial least squares path model jointly confirmed that preceding crops would improve soil quality and tobacco productivity.

This study highlights the importance of the legacy effects of preceding crops, which optimize soil microbial community structure, soil aggregate stability, and nutrients in soil ecological function processes. Apparently, preceding crop of garlic has more advantages than faba bean in this study.