Maize Stalk Lodging: Field Tests of a New Device for Measuring Stalk Strength.

A team of engineers has been collaborating with plant scientists to address the problem of maize stalk lodging. In a recent laboratory study conducted by this team, 5 commercial varieties of maize were grown at 5 planting densities and 2 locations with 2 replicates. Maize stalks from this experiment were submitted to a battery of tests to measure geometric and material features and stalk strength. While rind penetration resistance predicted just 18% of the observed variation in stalk strength, an engineering quantity known as flexural stiffness predicted 81% of the variation in strength. Furthermore, the relationship between flexural stiffness and stalk strength was unaffected by changes in planting density, and hybrid type.

Devices have now been developed for measuring stalk strength and stalk flexural stiffness in the field. Preliminary field tests were performed at three locations and involved both maize and sorghum. These tests indicated that stalks could be tested at rates of 120-180 stalks per hour. A relationship between strength and stiffness was found for both maize and sorghum ranging from R² = 0.49 (sorghum, green stalks) to R² = 0.78 (maize, dry stalks).

A field experiment is now in process to determine the broader relevance of the testing device. The experiment consists of 72 varieties grown at 10 locations across the United States. Stalk strength and stiffness will be measured immediately prior to harvest for 20 stalks per location. This data will be analyzed to determine differences (if any) in the strength of each hybrid, location effects on strength, and the stiffness-strength relationship. Once validated, this device could become a valuable breeding tool for increasing stalk strength.