When the topsoil of a sandy loam previously under fallow was removed, loosening the subsoil had negligible effect on pore space, but applying strong compaction decreased the pore space by about 4%, causing anaerobic conditions in the wet state; this effect persisted almost unchanged for 3 1/2 years. Under a. cropping sequence, light compaction (I kg/cm2) had similar effect to loosening, but heavy compaction (1 kg/cm2) decreased the pore space and the air content by about 2 and 2 1/2%

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... y. Despite vigourous plant growth, this small effect persisted unchanged during 6 1/2 years. Farmyard manure stimulated plant growth and decreased the adverse effect of heavy compaction. (Abstract retrieved from CAB Abstracts by CABI's permission)