Quantifying lodging-induced yield losses in oilseed rape

Abstract

Lodging has been identified as one of the factors responsible for the lack of improvement in farm yields of oilseed rape. Despite this, no studies have attempted to quantify the cost of lodging at regional or national scales. The objectives of this study were to better understand the impact of timing and angle of lodging on seed yield and oil content of modern oilseed rape varieties, test whether a model predicting lodging-induced yield losses for wheat is appropriate for oilseed rape and quantify the extent of lodging in UK oilseed rape crops using an aerial photograph survey, estimating the consequential effects of lodging on the value of the crop at a national scale. Artificial lodging experiments showed that the crop developmental stage at which lodging occurred and the angle of lodging had a significant impact on yield, with lodging to 90° during flowering reducing yield by 46% and lodging to 45° during flowering reducing yield by approximately 20%. Variable, but usually smaller amounts of yield were lost when lodging occurred during seed filling. Reductions in oil content of the seed were greatest when lodging occurred to 90° at early flowering. Yield losses were mainly related to reductions in seeds/m2. A model for predicting lodging-induced yield losses in winter wheat was tested for its suitability in predicting the effect of different angles of lodging at different growth stages on yield in oilseed rape against the experimental datasets. This wheat model was based on existing models of canopy photosynthesis and respiration to account for lodging induced changes to the canopy and the impact on light capture and rates of photosynthesis and respiration. This was shown to provide a reasonable prediction of yield losses from lodging during flowering, which indicated that reductions in photosynthesis was the primary cause of yield loss. The model was less effective at predicting yield losses from lodging during seed filling and additional work is required to explore whether the model needs further development to be appropriate for sink limited crops such as oilseed rape. In 2012 and 2014, approximately 35% and 27% of oilseed rape fields surveyed in the UK contained some lodging respectively. It is estimated that lodging to 90° during early flowering could cost the UK oilseed rape industry£120 million per year and lodging to 45° during mid seed fill could cost £47 million per year.