Lodging reduces yield of rice by self-shading and reductions in canopy photosynthesis

Abstract The adverse effects of lodging on light interception, canopy photosynthesis and yield were evaluated during grain filling in modern irrigated rice and modern deepwater rice (DWR) cultivars. Lodging, i.e. the reduction in plant canopy height due to bending of the shoot from vertical, occurred in canopies of modern irrigated and DWR growing in the field under tropical conditions and ranged from 0 to 42% of canopies which were held erect using nets; this was associated with yield reductions of up to 2 t ha −1 . A 1% reduction in grain yield occurred for every 2% lodging when data from different seasons, cultivars, and lodging treatments were plotted together. Lodging treatments which reduced canopy height by 75% (75% lodging) resulted in a suboptimal stratified light interception of the canopy. In lodged and non-lodged canopies, more than 80% of light was intercepted within the top 5 cm and 80 cm of canopies respectively. Lodging reduced canopy photosynthesis by 60 to 80% relative to erect canopies of DWR and irrigated rice respectively, and for DWR the reductions in canopy photosynthesis gave predicted reductions in yield which were equivalent to the measured yield. Data are used to support the hypothesis that the adverse effects of lodging during grain filling are largely the result of self-shading by leaves and panicles.