Maize Stalk Lodging: The Governing Effects of Stalk Morphology.

Stalk lodging has been studied from biological, chemical, and agronomic perspectives, but still persists as a frustrating problem for farmers and plant scientists. A structural engineering perspective is now being applied to this problem. A recent study by our group involved the creation and analysis of a computational model of the maize stalk. A sensitivity analysis of this model indicated that stalk morphology exerted a much higher influence on mechanical stresses within the stalk than did tissue properties.

The purpose of this study was to investigate the influence of stalk morphology on maize stalk strength. A set of 5 commercial hybrids were grown at 5 different planting densities at 2 locations in Iowa with 2 replicates per location. At the time of harvest, a set of 10 stalks were sampled from each plot. Geometric data was obtained via high-resolution CT scanning. A customized computer code was used to extract over 40 different geometric features from the CT data. These factors included both basic geometric measurements such as diameter and rind thickness, as well as more complex engineering quantities such as area moment of inertia to radius ratio. After scanning, stalks were tested in 3-point bending to determine stalk strength. Rind penetration measurements were also recorded as a point of reference.

The ratio of area moment of inertia to minor radius of the stalk was found to be highly predictive of stalk strength (0.70 < R² < 0.85). Engineering theory provides an explanation since this ratio is closely related to bending stress. The relationship between stalk strength and this geometric parameter was unaffected by environmental factors such as planting density and hybrid. It was also much better predictor of strength than rind penetration resistance measurements. This new information may be useful for studying lodging in other species and for breeding purposes.