Incorporating rhizosphere processes into field-scale (agro)ecosystem models

Abstract

Three different strategies for incorporating rhizosphere processes within field-scale models are compared, taking triple-cropped irrigated rice production as a common system and CH₄ emission as a common focus of interest. The strategies may be characterised as homogeneous (model I; root C deposition is added to the bulk soil compartment), areal (model II; roots contribute via aerenchymatous exchange to an increased soil-atmosphere interfacial surface area), and volumetric (model III; roots create around themselves a specific rhizosphere compartment). Model I is simpler than model II, which is simpler than model III. With identical parameters all models lead to similar seasonally integrated CH₄ emissions, but when the pattern of emission and the simulated CH₄ concentration in the soil is brought into the reckoning, the following order of precedence (greater is better) becomes clear: model III≥model II>model I. Current field-scale models of soil organic matter (SOM) transformation, especially in rice soils, could be improved by taking explicit account of the rhizosphere and the processes which occur within it.