EFFECT OF ORGANIC CONSTITUENTS AND COMPLEXED METAL IONS ON AGGREGATE STABILITY OF SOME EAST ANGLIAN SOILS

Paired soils of high and low organic matter content from the East Anglian silts were used to determine the role of different organic constituents and complexed metal ions in relation to aggregate stability. Although leaching with periodate and borate caused some loss of stability for most of the soils, the changes were much less than those due to extraction of the soils with pyrophosphate or acetylacetone which were more effective in removing organic materials complexed with iron and aluminium. Amounts of iron and aluminium extracted were not well correlated with changes in stability. The results indicate that in these soils polysaccharides are less important to aggregate stability than organic matter bonded to the clay particles through association with aluminium or iron.