Modelling compensatory effects of defoliation on leaf area growth and biomass of sunflower (Helianthus annuus L.)

Leaf area loss is a typical damage of fungal and insect attacks or hail. In this work growth responses to defoliation were analysed by removing 50% of leaf area at different phenological stages in sunflower (Helianthus annuus L.). Plants defoliated at head-visible stage showed an increased single leaf area which partly compensated the reduction in light interception during the season, while later treatments, during pre-anthesis and complete anthesis, did not show increased single leaf area but a delayed leaf senescence. A decrease in biomass accumulation was observed particularly in pre-anthesis treated plants. Results were implemented into the crop model OILCROP-SUN 6.0 to assess the impact of compensation on growth and yield. It was concluded that leaf area recovery should be incorporated into the growth models for a reliable simulation of yield after partial defoliation.