A model of radiation interception and use by a maize–bean intercrop canopy

A modelling study on intercropping was carried out to understand the radiation interception and use. The radiation transmission models on both instantaneous and daily bases were described and validated. For testing the model, photosynthetically active radiation was measured above and beneath a maize–bean intercrop canopy in both north–south (NS) and east–west (EW) rows at Bloemfontein, Free State, South Africa. Both models accurately predicted radiation transmitted through the intercrop canopy throughout the vegetative stage. For the instantaneous model, two methods were compared, namely, the geometrical method versus the statistical method. The geometrical method was equal in radiation transmitted per unit row to the statistical method. The daily amount of radiation intercepted and used by each component crop was estimated. Concerning the radiation utilisation, the intercropping was equivalent in growth efficiency of maize to the sole cropping whereas beans had greater radiation use efficiency in intercropping than in sole cropping, which might explain the intercrop yield advantage.