Md Abdul Awal, Wan Ishak Wan Ismail, Mohd. Haniff Harun, and Johari Endan

pp. 1083 - 1093

Abstract

Interception of light by a canopy is a fundamental requirement for crop growth and is important for
biomass production and plant growth modeling. Solar radiation is an important parameter for photosynthesis
and evapotranspiration. These two phenomena are dependent not only on the intensity of radiation but also
on the distribution of intercepted radiation within the canopy. In this study, two operational methods for
estimating the amount of photosynthetically active radiation (PAR) intercepted by a canopy of the oil palm
are presented. LICOR radiation sensors, model LI-190SA and model LI-191SA were used for photosynthetically active radiation (PAR) measurement above and below the canopy. We developed two methods, namely
″Triangular″ method and ″Circular″ method for PAR measurement. Results show that both methods were
suitable for oil palm PAR measurement. The triangular method is recommended for PAR measurements with respect to the whole plantation and the circular method is recommended for specific purposes, such as
growth analysis or growth modeling of the oil palm. However, practical considerations such as equipment
availability, purpose of the measurement, age of the palm, and the number of measuring points to be sampled
should be taken into account in the selection of a suitable method for a particular study. The results indicate
that the interception of radiation was affected by spatial variation, and the radiation transmission decreased
towards the frond tips.