The soil carbon cycle in the faba bean/maize Intercropping System

Intercropping systems are widely used worldwide because they are able to produce greater biomass per unit area than single crops as a result of complementarities in resource use and facilitation between component crops.

Maize-faba bean is a widely practiced intercropping system because nitrogen fixation by faba bean alleviates competition between the two crop species for an often scarce resource. In addition, on acid soils, root exudates of faba bean improve phosphorus uptake by both faba bean and maize. It is postulated here that intercropping may also enhance carbon storage in the soil. First of all, the above ground increase in biomass production is probably matched below ground. In addition, it has been suggested that interactions between roots result in greater production of root exudates, which would putatively result in greater carbon input into the soil in the form of organic molecules. While it seems likely that such deposits would be shortlived, empirical data are lacking, and the hypothesis is worth scrutiny. In this project, carbon deposition by intercrops will be empirically measured in short term experiments, while organic matter content in soils over time will be measured in long term experiments in monoculture systems and intercrop sequences, and by studying soils with different histories of monocropping and intercropping. Empirical research will be amplified by mechanistic models of the carbon economy in intercrops.

Results of this research will contribute to the scientific basis for policies and incentive programs that aim at enhanced carbon sequestration in agricultural soils.