Use of virtual 3D maize canopies to assess the effect of plot heterogeneity on radiation interception

Plants neighbouring gaps in the stand have a better grain yield because they intercept a larger amount of light. The question arises which part of this increase is due to larger incident radiation and which part to changes in plant morphology. Reproducible within-row and between-row variations in maize plant spacing relevant to agricultural practice were established in the field, by suppressing some seedlings just after the stand was establish. Virtual plots, with the same plant arrangement, were simulated with the ADEL-Maize model. The model, based on L-system formalism, simulated 3D canopies and a projection method was used to calculate intercepted radiation. Two types of simulation were performed, that is with or without the adaptations in plant morphology that had been observed in the field for plants adjacent to gaps. The accumulated radiation intercepted by individual plants calculated on models with unchanged leaf size is only from 89 to 98% of that corresponding with observed leaf size. We calculated the grain yield for each plant location, based on the radiation intercepted (calculated for virtual plants with observed leaf sizes, and for virtual plants with unchanged leaf sizes). Leaf size adaptation increases grain production by 0.6–11.7%. We calculated the cumulative radiation intercepted by three regular canopies, presenting a regular distribution at three different plant population densities. They consisted of the same plant number, on the same surface area as the irregular treatments in the neighbouring of the gaps. The irregularity of plant spacing resulted in an interception about 10% less than at constant plant population density.