Design and development of a tractor-mounted, recording penetrometer

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Virginia Polytechnic Institute and State University


As part of a long term study dealing with the effect of continuous use of no-till practice on soil structural characteristics, this study was conducted with the following objectives: (i) to design and develop a tractor-mounted, hydraulically-operated, recording penetrometer, (ii) to collect the initial penetration resistance data from the experimental plots established for the long term study.

A penetrometer assembly was designed and constructed with the capability of collecting penetration resistance across two crop rows. At any point, the penetration resistance data could be collected up to a depth of 60 cm. A simple hydraulic circuitry was developed to control the rate of penetration at 3 cm/s.

A micro-computer based data acquisition system was developed to record the penetration resistance and depth data during each penetration test. This data acquisition system together with a cassette tape recorder could record the data from large number of tests under field conditions. The data stored on the tape could be transferred to a personal computer for data reduction and analysis.

Field tests were conducted to evaluate the system developed and to establish the initial data for the experimental plots established for long term study. Results of these tests indicated that the system functioned satisfactorily and there exists significant difference in penetration resistance from plot to plot and as a function of depth within each plot.