A laboratory penetrometer for the measurement of the strength of soil clods

A penetrometer was devised to allow a rapid empirical assessment of clod strength to be made by measuring the maximum resistance met by a pneumatically driven penetration tool as it passed vertically through the clod. The penetrometer and its operating procedure are described and factors affecting the results obtained from it are investigated. A penetration tool comprising a 60° cone with a base dia of 50 mm, operated at a rate of penetration of 30 mm/s, has been adopted as standard for routine clod strength measurements made in the study of potato harvesting problems. In this form the penetrometer has been used to test more than 16,000 clods.