CORN MOTION IN THE WIND DURING SENESCENCE .1. MOTION CHARACTERISTICS

Lodging in corn (Zea mays L.) is often the result of wind-induced motion, which creates a strain on the stalk and root system. A study was conducted to characterize corn motion during windy periods at senescence and examine the implications for lodging. Motion was measured on 23 plants with a modified computer joystick during 6 d in October, 1988, at West Lafayette, IN. The wind force on each plant was estimated from within-canopy wind speeds, foliage area distribution, and foliage drag coefficients. Results showed that corn stalk displacement during windy periods was variable over time. The displacement pattern was distinct from the wind force pattern, and characterized by a resonant oscillation at a frequency near 1 Hz. Generally there was greater displacement in the across-row direction than in the along-row direction, with the across-row displacement variance more than four times larger than the along-row variance. There was little effect of wind direction on motion characteristics. In addition, there was a decrease in maximum displacements and the amplitude of resonant oscillation when the ear fell from an upright position to a hanging position. The nature of the corn motion suggests that dynamic plant motion characteristics may be important in determining lodging resistance.