Fig. 9

The response of food crop yield and biomass production to biochar application, n means the number of observations. An effect is significant (P < 0.05) if its 95% confidence interval (CI) does not include 1. The biochar treatment is considered to have no effect when the \(lnRR=1\), a positive effect when \(lnRR>1\), and a negative effect when \(lnRR <1\). The reason why confidence intervals are not symmetrical around the effect sizes is that they were transformed back from the log response ratio