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Biochar was more effective at saturation due to the increased porosity, while kaolinite responds similarly to biochar. It is, however, shown that most of the water retained by the Na-betonite may not be available to plants, particularly at high amendment rate. Furthermore, the clay and biochar materials improved particle bonding in the fine sand with the Na-bentonite being more effective than biochar and kaolinite (in that order) in strengthening interparticle bonds and improving the resilience of fine sand, if the rate of amendment is kept at ≤50 g kg-1. [ABSTRACT FROM AUTHOR]

The hydrophysical properties of the prevalent Humic Latosols (organic matter rich and charcoal stained soils) were related to structural sustainability under loading. Intact cores collected at the Ap, AB, Bw horizons were used for hydrophysi-cal characterization. Precompression stresses at 10 suctions were obtained to estimate the load bearing capacities. We observed the dominance of kaolinite with some occurrences of gibbsite and hydroxy-interlayered vermiculite in the clay mineralogy. The high organic matter content in the Ap horizon favours crumb struc-ture with the structural unit presenting high porosity and water retention. The structure of the AB and Bw horizons was, how-ever, granular with structural units having low porosity. Possible influence of earlier incidences of fire enhanced the organic mat-ter and carbon content in the soil reducing down the profile from 42.5 g kg-1at the Ap to 16.4 g kg-1at the Bw horizon. The C/N ratio increased from 14 at the Ap to 17 at the Bw, and air capacity increased from 18.1% atAp to 32.0% at Bw. Precompression stress values were: 100.6±40.7 kPa at Ap, 117.4±44.6 kPa at AB, and 116.1±58.9 kPa at Bw. Load bearing capacities at the AB and Bw horizons were homogenous. [ABSTRACT FROM AUTHOR]