Condappa de D. auteur aut IRD Galle Sylvie auteur aut IRD Dewandel B. auteur aut IRD Haverkamp Randel auteur aut IRD text journalArticle eng text/pdf born digital access The USDA soil textural triangle shows a zone where sods have a low silt fraction compared with the fractions of sand and day. These soils have a particle-size distribution function showing two local maxima in weight percentage for the particle-size ranges of sand and clay. The soils are referred to as bimodal soil, with an associated bimodal zone in the soil textural triangle. It was shown that processes of pedogenesis in tropical and subtropical regions favor the generation of bimodal soils. Data from the Maheshwaram watershed in South India (subtropical), the Oueme watershed in Benin (subhumid), and soil databases established for (sub)tropical regions confirmed that bimodal soils are common in (sub)tropical climates. These results were backed up by the fact that sample populations of bimodal soils are underrepresented in databases such as UNSODA, GRIZZLY, or the Soil Information System of the Netherlands, all three of which contain soils mainly from temperate regions. The consequences of bimodal soil behavior are important. The hydrodynamic flow behavior of these soils should be different from that of monomodal soils. The concept of shape similarity between the cumulative particle-size distribution curve and the water retention curve, validated for monomodal soils, implies that bimodal soils should theoretically exhibit bimodal hydraulic properties. These consequences are far reaching since most of the soil hydraulic models in the literature are monomodal and hence inadequate to describe the hydraulic behavior of bimodal soils from (sub)tropical regions. specialized 068 72 1 33-40 2008 0361-5995 https://www.documentation.ird.fr/hor/PAR00002205 10.2136/sssaj2006.0343 0361-5995 [F B010042483] https://www.documentation.ird.fr/hor/PAR00002205 https://www.documentation.ird.fr/intranet/publi/2008/03/010042483.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2008-03-31 2017-08-23 PAR00002205 fre