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A comparison of five instruments for measuring soil strength in cultivated and uncultivated cereal seedbeds
Author(s) -
O'SULLIVAN M. F.,
BALL B. C.
Publication year - 1982
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1982.tb01792.x
Subject(s) - penetrometer , loam , cohesion (chemistry) , geotechnical engineering , soil water , geology , shear (geology) , cone penetration test , soil science , materials science , composite material , chemistry , organic chemistry
Summary A torsional shear box, shear vane. cone penetrometer, drop‐cone penetrometer and pocket penetrometer were used to measure soil strength at several depths less than 150 mm in cultivated and uncultivated seedbeds in a loam and a sandy clay loam. From the shear box results, cohesion was higher and the angle of friction was lower in the sandy clay loam than in the loam. Angle of friction was independent of cultivation but cohesion was higher in uncultivated than in cultivated soil. Despite these differences cone resistance was similar in both soils above 70 mm depth. Vane shear strength and drop‐cone penetration, although empirical, indicated strength differences between soils and cultivations similar to those found with the torsional shear box. Vane shear strength, at 42 kPa, was about twice as high as cohesion in the sandy clay loam and, at 33 kPa, over four times as high as cohesion in the loam. These overestimates increased with increasing bulk density. The range of measurement of the pocket penetrometer was inadequate to cover the range of soil strengths encountered. The coefficient of variation within plots for cone resistance decreased from 76 per cent at 10 mm depth to about 22 per cent at 70 mm depth and below, and for vane shear strength it was 33 per cent near the soil surface. The drop‐cone penetrometer results were the most variable, reflecting the log‐normal distribution of penetrations. The cone penetrometer was the fastest method, followed by the shear vane, drop‐cone penetrometer and torsional shear box in that order.