Determining Daily Radiation Interception in a Semiarid Inter-cropping System

Abstract

Information on canopy radiation transmission is essential to understand energy balance in soil-plant-atmospherecontinuum, as net radiation is a major part of the energy balance. Compared with horizontally homogeneouscanopies, there could be large measurement errors in radiation transmission through heterogeneous canopies suchas row crops and inter-crops. In such canopies, the radiation transmission needs to be determined with greatcare. This study analysed the diurnal distribution of radiation transmission through maize and bean canopies inmono-cropping and inter-cropping using the data collected from field experiments in a semi-arid region of SouthAfrica, where solar radiation is not a limiting factor for plant growth. The results suggested that when the radiationtransmission is measured only at a given time, the measurement should be taken just before mid-morning (9:00–10:00) or mid-afternoon (14:00–15:00). This study further suggested feasibility of a simple rational model to estimatethe daily fraction of radiation intercepted by the canopies from the radiation interception measured at solar noon.