Stress equation for a cantilever beam: a model of lodging resistance in field pea

Mechanically harvested crops must be erect (lodging resistant) to facilitate harvest. Stem lodging changes canopy structure, increases disease pressure, reduces yield, and reduces harvest efficiency in pea. A number of studies have examined the traits that cause lodging susceptibility, but the relative impact of each trait is difficult to determine. A great need exists in pea breeding to develop a working model to explain lodging resistance. This study used the flexure formula to predict the amount of lodging variation explained by some of the major traits. Datasets from pea indicate that the percent variation explained by this lodging model is ~58%, and this model can be used to predict the relative impact of an increase in load, height, stem diameter, stem wall thickness, or yield on lodging susceptibility. This study indicates that plant height is strongly correlated with lodging susceptibility, but stem diameter is positively correlated with lodging resistance. Stem wall thickness appears to have no major effect on lodging resistance, which has not been previously reported in pea. Any doubling in plant height would also double the amount of stem material, but stem stress is expected to increase fourfold. A doubling in stem diameter is expected to increase the amount of stem material by fourfold and decrease stem stress by eightfold. The results of this study indicate that plant breeders should focus on increasing basal stem diameter to increase lodging resistance.