Microbial inoculants enhance crop yield, photosynthesis and disease suppression in China: a meta-analysis

Microbial inoculants (MIs) represent a nature-based alternative to chemical fertilizers and pesticides, promoting crop growth and offering a promising route toward low-carbon development. To evaluate the effects of MIs on crops in China, we conducted a meta-analysis based on 1110 effect sizes derived from 172 studies, with the evidence base dominated by peer-reviewed Chinese-language literature. Overall, MIs application significantly increased crop growth by 23.45% (P < 0.001), with the harvest yield sub-indicator showing a 14.92% relative increase. This response was also significantly moderated by fertilization strategy (F₍₁₎ = 6.80, P = 0.009). Neither the composition of MIs (bacterial, fungal, or mixed) nor their source (commercial or non-commercial) exerted a significant moderating effect on the yield response of crops. The photosynthesis was also significantly enhanced under MI application, with an average increased by 18.53% (P < 0.001). The MIs source (F₍₁₎ = 6.69, P = 0.009), MIs application method (F₍₃₎ = 3.22, P = 0.022), MIs application frequency (F₍₁₎ = 4.59, P = 0.032) and fertilization strategy (F₍₁₎ = 11.41, P < 0.001) significantly affected the response pattern. The MIs application significantly suppressed disease incidence by 46.90% (P < 0.001), and decreased the disease index by 51.87% (P < 0.001). The disease incidence response differed significantly (F₍₁₎ = 4.42, P = 0.035) between commercial MIs (-66.98%) and non-commercial MIs (-41.09%). The disease index response was significantly affected by crop subclass (F₍₆₎ = 5.59, P < 0.001) and marginally affected by fertilization strategy (F₍₆₎ = 3.57, P = 0.059). Furthermore, when focused on bacterial MIs, the multi-strain MIs significantly outperformed single-strain in growth promotion (P = 0.022) and disease index suppression (P = 0.004). These results highlight the potential of MIs to improve crop performance, and their efficacy warrants further investigation under diverse field conditions to optimize their practical application.