Abstract

Maize is one of the most widely cultivated grains in the world, making it crucial to world food security and important economically. One major problem in maize production is stalk lodging (greensnap), which results in billions of dollars in lost harvests annually for maize farmers in the US alone. Understanding the mechanical properties of maize plants is crucial to addressing this problem. Previous studies have suggested that the leaf blades and leaf sheaths affect maize mechanical properties. The objectives of this thesis are twofold: to present measurement techniques for the stalk bending strength, damping ratio, and natural frequency of maize and show how these properties are affected by the leaf sheath and blade. Over the course of two years, the "DARLING" (Device for Assessing Resistance to Lodging in Grains) was used to make over 1000 field measurements of stalk bending strength for plants with and without the leaf sheath. The leaf sheath was found to have a significant effect on stalk strength. A statistical model is presented which shows leaf-sheath influence was largest for younger stalks, and became less pronounced as the stalks matured. In addition, a novel measurement system, the CAMP (Corn Accelerometer Measurement Platform), is presented and demonstrated to be effective for capturing the dynamic behavior (damping ratio and natural frequency) of maize plants. Using free vibration method in the field, the CAMP was used to assess the damping ratio and natural frequency of 43 mature maize plants in three states: whole, with leaves removed, and with leaf sheaths removed. Using a forced vibration method in a laboratory, a similar experiment was performed on 25 newly-tasseled maize plants in pots. The free vibration method was deemed to be superior to the forced vibration method. The results of the studies validate the measurement methods, quantify the effect of the leaf sheath on plant strength, and provide preliminary info on the effects of the leaves on dynamic behavior that will inform future studies. Ultimately, the lessons learned improve understanding of the effects of the leaves on mechanical properties of maize plants and are one step closer towards reducing the negative effects of stalk lodging.

Degree

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

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