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Determining Daily Radiation Interception in a Semiarid Inter-cropping System

M Tsubo
H.O Ogindo
S Walker
M.N.V Dingaan


Information on canopy radiation transmission is essential to understand energy balance in soil-plant-atmosphere
continuum, as net radiation is a major part of the energy balance. Compared with horizontally homogeneous
canopies, there could be large measurement errors in radiation transmission through heterogeneous canopies such
as row crops and inter-crops. In such canopies, the radiation transmission needs to be determined with great
care. This study analysed the diurnal distribution of radiation transmission through maize and bean canopies in
mono-cropping and inter-cropping using the data collected from field experiments in a semi-arid region of South
Africa, where solar radiation is not a limiting factor for plant growth. The results suggested that when the radiation
transmission 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 estimate
the daily fraction of radiation intercepted by the canopies from the radiation interception measured at solar noon.