SIMULATING LIGHT REGIME AND INTERCROP YIELDS IN COCONUT BASED FARMINGSYSTEMS

Intercropping experiments of corn and mungbean have been conducted at the Davao Research Center of the Philippines Coconut Authority under c oconut stands at different densities. Yields obtained in these experim ents are more or less linear functions of the photosynthetically activ e radiation measured under the trees. In order to extrapolate these re sults for other palm ages and densities, the following steps have been achieved: (1) measurement and modeling of the architecture of 5, 20 a nd 40 year old palms, (2) generation of virtual coconut stands, (3) si mulation of light transmission using these virtual stands, (4) predict ion of intercrop yields by combining the results of intercropping expe riments and the simulated light transmission. The simulated light tran smission under 5, 20 and 40 year old coconut stands were close enough to field measurements to consider that both computerized coconut mock- ups and radiative models are valid. Radiative simulation experiments c ould thus be performed in order to assess the effect of coconut densit y on photosynthetically active radiation (PAR) transmission as well as the effect of frond pruning. Results exhibit a nearly linear relation ship between light transmission and tree density. Pruning also appears as an effective mean of increasing the light permeability of coconut stands. These results are interpreted in terms of corn and mungbean yi elds by combining radiative simulations and field intercropping experi ments. (C) 1997 Elsevier Science B.V.