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The accuracy of plant growth models depends strongly on a precise calculation of radiation uptake. Numerous approaches exist to estimate light absorption in spatially heterogeneous canopies, but these either have restrictions with respect to canopy structure or involve complex and inflexible calculations. The objective of this study was to develop a simulation tool to assess radiation penetration into canopies that should (i) give details on light absorption in heterogeneous canopy architectures and (ii) comprise simple and easily adaptable routines. In the model, the complete canopy volume is subdivided into cubic units that are either empty or filled with leaf area. Leaf area can be distributed in an arbitrarily chosen geometric solid positioned anywhere in the model domain. Transmission through the cubes is calculated by following the path of solar rays from the top of the canopy to ground level. Daily canopy absorption is calculated separately for direct and diffuse radiation, taking reflection and scattering of the direct beam into account. Using only a few readily obtainable parameters, a close agreement between simulated and measured canopy transmission of a cauliflower (Brassica oleracea var. botrytis L.) crop was found (r2=0.97) Comparing different canopy structures ranging from single‐plant canopies to a closed canopy gave detailed information on the absorption characteristics and the distribution of light absorption in individual plants. Results for closed canopies and row crops were consistent with those of earlier models. It is thus useful as a reference model to identify possible simplifications in the quantification of light interception by heterogeneous crops.

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