ROTHAMSTED STUDIES OF SOIL STRUCTURE VI.

Abstract

Summary An ultrasonic method has been used to measure the stability index, σ, for each horizon of six soils. They provided three soil series comparisons: Hanslope‐Ragdale, Evesham‐Denchworth and Flint‐Salop, in which the first‐named series in each pair is ‘rarely problematic’, and the second ‘commonly problematic’ in management. The results for the top soils are presented in terms of the relationship between σ and the concentrations of those soil constituents likely to contribute to stability of aggregates: organic matter, clay, iron and aluminium oxides, and calcium carbonate. Regression analysis indicates significant correlations for all except the iron and aluminium oxide components. For each soil pair, the ultrasonic measures of stability did not reflect soil management experience, either for surface or sub‐soil horizons. In general the commonly problematic soil appeared to have the same if not higher stability than its rarely problematic partner. Ultrasonic measurement of stability to dispersion, whilst indicating possible mechanisms of soil aggregate formation and breakdown, gives little help in identifying soil management potential.