how to calculate rhizosphere effect

Rhizosphere effect is quantified by comparing microbial or biochemical parameters in rhizosphere soil to bulk soil. A common formula is: Rhizosphere Effect Index (REI) = (Parameter in rhizosphere / Parameter in bulk soil) – 1. It’s used to evaluate microbial abundance, enzyme activity, or nutrient availability influenced by root presence. Higher values indicate stronger root influence on the soil environment.