|Sudduth, Kenneth - Ken|
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2006
Publication Date: 2/24/2006
Citation: Chung, S.O., Sudduth, K.A., Hummel, J.W. 2006. Design and validation of an on-the-go soil strength profile sensor. Transactions of the American Society of Agricultural and Biological Engineers. 49(1):5-14.
Interpretive Summary: Precision agriculture aims both to minimize costs and environmental damage caused by agricultural activities and to maximize crop yield and benefits, all based on information collected at within-field locations. One factor that can vary considerably within fields and can also greatly affect crop yields is soil strength, or compaction. Because of this, a quick and inexpensive compaction measurement device is needed by farmers and consultants. Addressing this need, we built an on-the-go sensor that can take measurements continuously while traveling across a field. The sensor is attached to a tractor and consists of a narrow vertical blade. Extending forward from the front edge of the sensor blade are cutting tips that measure compaction at five depths. Compaction measurements were obtained with the sensor in the field to select the best configuration for the cutting tips. Sensor data was also compared to data from the standard device currently used to measure compaction, the cone penetrometer. Measurements from the two devices were similar, so the many scientific findings from cone penetrometer research can also be applied to our sensor. These results will help companies wanting to develop a commercial compaction sensor that farmers and consultants can use. Compaction maps from such a sensor would help farmers interpret variations in yield maps and would also provide the information needed to control precision tillage operations.
Technical Abstract: Soil strength has traditionally been determined using the cone penetrometer, an instrument that provides highly variable discrete point measurements, making it difficult to detect statistically significant differences in the soil strength profile among treatments or locations. Generally, this problem has been addressed by obtaining a large number of measurements, a process that is time-consuming and labor-intensive. Our objective was to develop a soil strength profile sensor (SSPS) that could take measurements continuously and more efficiently while traveling across the field. The on-the-go SSPS was designed and fabricated using an array of load cells, each of which was interfaced with a soil-cutting tip. These multiple prismatic tips were extended forward from the leading edge of a vertical blade and spaced apart to minimize interference from the main blade and adjacent sensing tips. Prismatic soil strength index (PSSI, MPa) was defined as force divided by the base area of the sensing tip. The sensing tip had a 60 degree cutting or apex angle and a base area of 361 sq mm. The design maximum operating depth was 0.5 m, and the upper limit and resolution of soil strength were 19.4 MPa, and 0.14 MPa, respectively. Field tests determined that the optimum extension and spacing of the cutting tips were 5.1 and 10 cm, respectively. A significant (alpha<0.01) linear relationship between PSSI and penetrometer cone index (CI), with a slope of approximately 0.6, was found for field data collected at a 30-cm depth. The ability to develop such relationships comparing penetrometer and SSPS data will allow SSPS data to be interpreted with respect to the available body of penetrometer literature.