Abstract
Two degrees of compaction, 'heavy' with a flattyred vehicle wheel, and 'light' with a ring roller, were given to the seed beds after sowing barley and globe beet on three contrasted soils. Changes in pore space of the soils and the responses of the crop to the changed physical properties were measured. The sites used were: Barnfield at Rothamsted, a heavy clay loam long under arable cultivation and having little organic matter; Pastures Field at Rothamsted, a field of silty clay loam ploughed after an 8-year ley; Stackyard field at Woburn, a light sandy loam long in arable cultivation and containing little organic matter.