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ASIMULATED INVESTIGATION TO MEASURE ACOUSTIC EMISSIONS CAUSED BY ROOT GROWTH

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASAE.  VOL. 43(6): 1905-1910 . (doi: 10.13031/2013.3095) @2000
Authors:   C. D. Durairaj, L. Okushima, S. Sase
Keywords:   Acoustic emission, Root growth rate, Root growth simulator

Monitoring root growth in greenhouses is essential for planned application of growth inputs to the plants and control of the growth environment. A possible method for detecting root growth is to measure the Acoustic Emissions (AE) caused by root-soil interaction. The use of such a technique necessitates a thorough understanding of the AE patterns caused by the root at each growth rate under controlled conditions. Because a real root cannot be controlled to grow at a constant rate, a dedicated root growth simulator was developed to push a probe into the soil at preset rates and thus simulate root growth. The simulator consisted of a stepper motor, allied driver circuitry, a timer module to control the penetration rate, and a hydro-mechanical transmission element. The simulation was conducted in a sand bath, which was instrumented with three AE sensors connected to a conventional AE monitor. Beforehand, the sensors were calibrated for their sensitivity using an AE generator built for this purpose. AE was measured in a noise proof environment in sand under both dry conditions and 10% moisture, with the simulated root growth varied at three levels of 0.5, 1.0, and 1.33 mm h 1 . Emissions from wet or dry sand were periodic and of high intensity. Spectral analysis techniques were used to recognize the dominant frequency at each level of growth rate. Simultaneously, the acoustic attenuation of sand was also measured and correlated with that of the AE signals to study the influence of sensor placement on AE detection. When AE measurements from real root growth were acquired and analyzed, the observed dominant frequencies varied in the same range acquired from the simulations. Hence if more relevant data on AE under simulated studies are acquired, possibilities do exist for this method to be useful for detecting real root growth.

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