Simulating light regime and intercrop yields in coconut based farming systems

Intercropping experiments of corn and mungbean have been conducted at the Davao Research Center of the Philippines Coconut Authority under coconut stands at different densities. Yields obtained in these experiments are more or less linear functions of the photosynthetically active radiation measured under the trees. In order to extrapolate these results for other palm ages and densities, the following steps have been achieved: (1) measurement and modeling of the architecture of 5, 20 and 40 year old palms, (2) generation of virtual coconut stands, (3) simulation of light transmission using these virtual stands, (4) prediction of intercrop yields by combining the results of intercropping experiments and the simulated light transmission. The simulated light transmission 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 could thus be performed in order to assess the effect of coconut density on photosynthetically active radiation (PAR) transmission as well as the effect of frond pruning. Results exhibit a nearly linear relationship 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 yields by combining radiative simulations and field intercropping experiments. (C) 1997 Elsevier Science B.V.