Predicting yield losses caused by lodging in wheat

Lodging is a major limiting factor for wheat (Triticum aestivum L.) production, yet few studies have investigated the mechanism by which it reduces yield. This paper tests the hypothesis that lodging-induced yield losses in wheat can be predicted by calculating the reduction in canopy photosynthesis that results from lodging-induced changes to the architecture of the canopy. An existing model of canopy photosynthesis has been further developed to account for the effect of lodging-induced changes to the canopy architecture on photosynthesis and grain yield. The model predicted that lodging at 90° from the vertical will reduce yield by approximately 61%. The ability of the model to predict lodging-induced yield losses was tested against observations made in three separate field experiments. The model predicted 71% of the variation in the proportion of yield lost due to lodging (YLOSS) and the best-fit line was not significantly different from the 1:1 relationship. Sensitivity analysis showed that the proportion of yield lost was relatively insensitive to the model parameters. As a result it was shown that a simplified model could be employed without losing predictive accuracy. YLOSS=∑if(L90×0.7+L65×0.3+L25×0.1)/n In this equation i and f are the 1st and last days of grain filling, L90 is the proportion of crop area lodged at 85–90° from the vertical, L65 is the proportion of crop area lodged between 46° and 84°, L25 is the proportion of crop area lodged between 5° and 45° and n is the number of days of grain filling.

► A model of canopy photosynthesis has been developed to account for lodging.
► The model predicted that severe lodging will reduce yield by 60–70%.
► Predicted versus observed lodging-induced yield losses regression had R2 of 71%.
► The first model that we know of that predicts lodging-induced yield losses in wheat.