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Title: SOIL STRUCTURE EVALUATION BY USE OF FIBER-OPTIC SENSOR

Author
item ZUO YUEMING - SHANXI UNIV., P.R. CHINA
item Erbach, Donald
item MARLEY STEPHEN J - IOWA STATE UNIVERSITY

Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Abstract Only
Publication Acceptance Date: 6/23/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Soil structure is an important measure of soil quality and has significant effects on crop production, water-use efficiency, and soil erosion. Considerable effort and money is expended to modify the structure of agricultural soil. However, we have no effective and practical method to measure soil structure. Therefore, to evaluate existing soil structure and to determine whether management practices are improving or degrading soil structure, techniques to measure soil structure are needed. A fiber-optic displacement sensor (Series 88, Philtec, Inc.) was used to scan the surface of bulk samples of soil aggregates. The soil was air dried and sieved to aggregate size fractions of <180 um, 180-250 um, 250 um-0.5 mm, 0.5-1 mm, 1-2 mm, 2-4 mm, and 4-8 mm. The surface was prepared by moving a blade at 5.08 mm/s over the soil. Immediately following preparation, a sensor was moved over the surface by use of a universal testing machine (Model 8500, Instron, Corp.). Voltage output of the sensor was recorded by use of Labtech Notebook at sampling rates of 10, 100, and 200 hz. Mean sensor output voltage decreased significantly (P=0.005) as aggregate size increased. Measured mean voltage values for the aggregate size fractions, in the order listed above, were 4.6, 3.1, 2.5, 1.5, 0.8, and 0.2 v. Therefore, it appears that mean sensor output voltage may be used as an index of soil structure. The Fast Fourier Transform (FFT) of the data also was sensitive to aggregate size. Data sampling rate affected the FFT but had a negligible effect on mean output voltage. The results indicate that the fiber-optic soil-structure sensor may have potential for use on a probe to measure in-situ soil structure or as a sensor on a tillage tool to provide feedback control information.