Development of a model of lodging for barley

Lodging in barley (Hordeum vulgare L.) can result either from buckling of any part of the stem (stem lodging) or failure of the root-soil anchorage system (root lodging). A framework for calculating the risk of stem lodging is developed which takes account of the shoot's height, ear area, natural frequency, weight, the flexural rigidity of the stem and changes in stem strength along its length. The model predicted that stem lodging in barley cultivars would occur half way up the stem, and stem lodging in wheat would occur close to the soil surface. These predictions are consistent with general observations of stem lodging in barley and wheat. The higher position of stem lodging in barley, compared with wheat, was caused by the greater flexibility of the barley stems and a more rapid reduction in stem strength up the stem. A sensitivity analysis showed that the stem diameter of the middle internodes had the greatest effect on the risk of stem lodging. Changes to ear area, drag coefficient, crop height, shoot natural frequency and the strength of the stem wall had a moderate influence. Measurements of anchorage strength in barley and wheat plants indicated that the mechanism of anchorage failure was the same for both species and that a model of root lodging developed for wheat could be successfully adapted for barley.