Journal of Food, Agriculture and Environment

Multiprobe soil compaction sensor: An acoustical approach

Author(s):

Abbas Moallemi-Oreh ¹, Saeid Minaei ^2*, Ahmad Sharifi-Malvajerdi ³, Ali Mohammad Borghaee ¹

Recieved Date: 2010-07-23, Accepted Date: 2010-10-29

Abstract:

Compaction of agricultural soil, its measurement and management have been a matter of concern to farmers, equipment manufacturers and agricultural researchers for many years. In this research, an on-the-go multiprobe acoustic soil compaction estimation system was developed using three equally spaced microphone-fitted cone-shaped tips, horizontally mounted on a vertical tine. With this arrangement, the system estimates soil compaction in three layers (5-15, 15-25 and 25-35 cm) based on measurement of power spectral density (PSD) of the sound created by the tine being pulled through the soil. The sensing tips were tested at a speed of 0.5 m s^-1 in a soil bin while operating at 10, 20 and 30 cm depths. Five soil density levels were created for this purpose by 1, 2, 4, 6 and 10 passes of a compression roller. Preliminary tests showed a direct relationship between sound amplitude and compaction levels in the 5.5 to 7.5 kHz frequency range of the spectrum. Therefore, a filter bank was utilized consisting of five filters having frequency domains of 5.5-5.9, 5.9-6.3, 6.3-6.7, 6.7-7.1 and 7.1-7.5 kHz. In each frequency domain, the average of PSD was measured and the relationship between absolute value of PSD and cone index was determined. Results of tests demonstrated that in the 5-15 cm layer, linear regression of CI_5-15 as a function of PSD was not significant in any of the frequency domains, because the sensing tip at the 10 cm depth was working above the critical depth. However, this relationship was significant in the 15-25 cm (R² = 0.62) and 25-30 cm (R² = 0.77) layers in the 7.1-7.5 kHz frequency domain. The acoustic sensor utilized in the soil compaction estimation system is a very small, simple and inexpensive microphone. Hence, it can easily be mounted on tillage tines to obtain information about soil compaction for spot tillage as well as making other management decisions.

Keywords:

Acoustic sensor, soil compaction measurement, precision tillage

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Journal: Journal of Food, Agriculture and Environment
Year: 2010
Volume: 8
Issue: 3&4
Category: Agriculture
Pages: 747-750

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