Wind force and corn motion during senescence
Abstract
Lodging in corn (Zea mays L.) usually results from wind imposing a strain on the plant greater than it can withstand. Annual yield losses in the USA due to lodging range between 5 and 25%. The objective of this study was to characterize the wind force and the motion response of corn plants in the field during senescence. Plant motion was measured on several plants with a modified computer joystick during windy days 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 the wind force on a corn plant was highly variable, with the standard deviation always greater than the mean. The mean wind force on the stalk base was less than reported static lodging forces, although instantaneous values did exceed those forces. The absorbed wind force on a plant decreased with a decrease in plant height, a shift in leaf area distribution so that a greater portion was at lower heights, and a decrease in leaf area. Power spectra of the wind force showed that the wind energy was greatest at frequencies less than 0.01 Hz, and decreased with higher frequencies. The motion of a corn stalk in the wind was characterized by oscillation near its natural frequency ($\omega\rm\sb{n}$). The average $\omega\rm\sb{n}$ of plants in the field was 1.54 Hz, well above the frequency of highest wind energy. The average plant had a damping coefficient ($\zeta$) of 0.11. Lower stalk motion was generally well described by a second-order response model defined by $\zeta$, $\omega\rm\sb{n}$, and plant stiffness (K). In theory, plant motion will increase as $\omega\rm\sb{n}$, $\zeta$, and K decrease. The results suggest that lodging resistance may be increased if plant $\omega\rm\sb{n}$ is shifted to higher frequencies and/or if $\zeta$ is increased.
Degree
Ph.D.
Advisors
Grant, Purdue University.
Subject Area
Agronomy|Atmosphere|Agricultural engineering
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