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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Agricultural and Biosystems Engineering

First Advisor

Daniel S. Humburg


A device mounted to the three-point hitch of a tractor to measure in-situ soil bearing capacity and cone index was developed and tested. The device contained a footing for bearing capacity tests and a probe for cone penetrometer tests. A hydraulic cylinder powered by the tractor's auxiliary hydraulic circuit forced the footing or cone penetrometer into the soil. Load cells were used to measure bearing plate and cone penetrometer loads. A linear potentiometer was used to measure penetration depth. This device is capable of measuring bearing capacities up to approximately 560 kPa and cone index up to about 7 MPa. A computer-implemented data acquisition system with National Instruments LabView software was used to measure, display, and record data.
Tests were performed in fields containing silty clay loam soils located about 2 miles northwest of Brookings, SD. The following conclusions were obtained for the soil bearing capacity and cone penetrometer tests. For com plots, a tilled soil exhibited significantly higher bearing capacities for all three plots compared to a no-till soil, while cone index tests revealed no significant difference. The overall average bearing capacities in the com plots for tilled and no-till were 488.8 and 440.0 kPa, respectively. For wheat plots, a tilled soil exhibited significantly higher bearing capacities for 2 plots and no significant difference for a third plot compared to a no-till soil. The overall average bearing capacities in the wheat plots for tilled and no-till were 505.4 and 477.1 kPa, respectively. Cone index tests in the wheat plots indicated a significant difference in tillage regimes at the 0.05-0.12 m range with higher cone indices in the no-till plots.

Library of Congress Subject Headings

soil mechanics
agricultural machinery


Includes bibliographical references (68-72)



Number of Pages



South Dakota State University


Copyright © 2002 Bernard R. Jahn. All rights reserved