HOT-WATER SOLUBLE ORGANIC-MATTER AND AGGR EGATE STABILITY - METHODOLOGICAL ASPECTS AND APPLICATION TO FERRALLITIC SOILS OF THE CONGO

The structural stability of surface and deeper horizons of ferrallitic soils of the Congo was studied in relation to the land use and the to tal organic carbon content of the samples. The role of hot-water solub le carbon in aggregation was assessed with two experimental approaches , one by heating in an oven and the other in an autoclave under pressu re. The proportion of aggregates (> 200 mu m) stable in cold water wer e compared with that of macroaggregates stable in hot water. Cropping situations under study induced significant variations in total carbon content. Aggregate stability was highly correlated with both soluble a nd total carbon contents. However, amounts of water-stable aggregates obtained before and after solubilization of organic matter in hot wate r were not significantly different. This result would infirm the suppo sed aggregating role of soluble organic matter, inferred from statisti cal data only.