New Approaches to Predicting Stalk Strength.

A forensic analysis of lodged corn stalk suggested that principles from engineering beam theory may provide novel insights into the problem of stalk lodging. In particular, it was hypothesized that the area moment of inertia to radius ratio of stalks (an engineering quantity used in analyzing structural members) would be highly predictive of stalk strength and therefore lodging propensity.

Laboratory based experiments conducted on 2 replicates of 5 commercial varieties of dent corn grown at 5 planting densities in 2 locations were used to investigate this hypothesis. Stalks were imaging via high resolution X-ray computed tomography to acquire a detailed representation of stalk morphology.  Subsequently, stalk strength was measured by subjecting stalks to a 3-point bending test which produced the same failure types and patterns observed in naturally lodged plants.

Results demonstrated that several morphological quantities derived from engineering beam theory were highly predictive of stalk strength. In particular, the area moment of inertia to radius ratio of corn stalk was found to predict stalk strength with four times the accuracy of rind penetration measurements.  Furthermore, strength predictions based on the area moment of inertia to radius ratio were not confounded by environmental effects such as planting density. However, rind penetration predictions were found to be significantly confounded by environmental effects. A field deployable tool to measure the area moment of inertia to radius ratio of stalks in a more cost effective manner (i.e. without the use of X-rays) is being developed. A field study will be conducted in the Fall of 2016 to assess the effectiveness of the tool in predicting stalk strength, as well as time to phenotype.