Organic amendments enhance soil microbial diversity, microbial functionality and crop yields: A meta-analysis.

Fertilization plays an important role in changing soil microbial diversity, which is essential for determining crop yields. Yet, the influence of organic amendments on microbial diversity remains uncertain, and few studies have addressed the relative importance of microbial diversity versus other drivers of crop yields. Here, we synthesize 219 studies worldwide and found that organic amendments significantly increased microbial diversity components (i.e., Shannon, richness, and phylogenetic diversity) and shifted microbial community structure compared to mineral-only fertilization. The performance of microbial alpha diversity varied substantially with organic amendment types, microbial groups and changes in soil pH. Both microbial diversity and community structure exhibited significantly positive relationships with microbial functionality and crop yields. In addition, soil abiotic properties and microbial functionality had a much stronger impact on crop yields than microbial diversity and climate factors. Partial least squares path modeling showed that soil microbial diversity was an important underlying factor driving crop yields via boosting soil microbial functionality. Overall, our findings provide robust evidence for the positive diversity-functions relationships, emphasizing that substituting mineral fertilizers with organic amendments is a promising way to conserve microbial diversity and promote soil microbial functions and crop yields.