[en] The exploitation of the magnetic susceptibility of soil particles to estimate the state of soil development or its degradation by erosion bases on the comparison of the magnetic susceptibility values and their evolution in depth between stable reference soil and soil which underwent erosion or, on the contrary, receive a contribution of particles. Measures of the magnetic susceptibility of the soil particles on 30 cms deep were made on pedological coverage of one substratum in four zones different by their slope and land use. In the first zone the soil is little evolved. It develops under an exceptionally worked fallow. The average of the magnetic susceptibilities is 7.41 10-8 m3 kg. In the second zone the ground is developed well on several decimeters. It is extensively exploited by cereal crops. The magnetic average susceptibility is 23.42 10-8 m3 kg. The third zone is a soil which evolves under a natural herbaceous coverage (alfa) moderately dense. The average of the magnetic susceptibilities of this zone is 13.75 10 8 m3 kg. The fourth zone completely lost its soil, the substratum is affected itself. The average of the magnetic susceptibilities of this zone is 6.5 108 m3 kg. By comparing the magnetic susceptibilities of these degraded soils and their evolution in depth to those of a stable soil (204.04 10 8 m3 kg) we notice a big difference which allows to estimate the state of their degradation and to determine the factors favoring this degradation. The position of cores on the hillside allowed to have an idea on the particles redistribution by the streaming and consequently on the geodynamics processes of the hillside surface.

[fr] L'exploitation de la susceptibilité magnétique des particules du sols pour l'estimation de l'état de développement pédogénétique ou de dégradation des sols par l'érosion repose sur la comparaison des valeurs de la susceptibilité magnétique et de leur évolution en profondeur entre des sols stables de référence et des sols qui ont subi une érosion ou, au contraire, un apport de particules. Des mesures de la susceptibilité magnétique des particules du sol sur 30 cm de profondeur ont été effectués sur quatre zones différentes par la pente et l'utilisation des sols de la couverture pédologique d'un même substrat. Dans la première zone le sol est peu évolué. Il se développe sous une jachère exceptionnellement travaillée. La moyenne des susceptibilités magnétiques mesurées est de 7,41 10-8 m3/kg. Dans la seconde zone le sol est bien développé sur plusieurs décimètres. Il est intensivement exploité par la éréaliculture. La susceptibilité magnétique moyenne est de 23,42 10-8 m3/kg. La troisième zone est un sol qui évolue sous une formation herbacée naturelle (alfa) moyennement dense. La moyenne des susceptibilités magnétique de cette zone est 13,75 10-8 m3/kg. La quatrième zone a complètement perdu son sol, le substrat est lui-même érodé. La moyenne des susceptibilités magnétique de cette zone est 6,5 10-8 m3/kg. En comparant les susceptibilités agnétiques de ces sols dégradés et leur évolution en profondeur à celles d'un sol stable (204,04 10-8m3/kg) on constate une grande différence qui permet d'évaluer l'état de leur dégradation et de déterminer les facteurs favorisant cette dégradation. La position des carottes sur le versant a permis d'avoir une idée sur la redistribution des particules par le ruissellement et par conséquent sur les processus de la géodynamique de surface du versant The exploitation of the magnetic susceptibility of soil particles to estimate the state of soil development or its degradation by erosion bases on the comparison of the magnetic susceptibility values and their evolution in depth between stable reference soil and soil which underwent erosion or, on the contrary, receive a contribution of particles. Measures of the magnetic susceptibility of the soil particles on 30 cms deep were made on pedological coverage of one substratum in four zones different by their slope and land use. In the fi rst zone the soil is little evolved. It develops under an exceptionally worked fallow. The average of the magnetic susceptibilities is 7.41 10-8 m3 / kg. In the second zone the ground is developed well on several decimeters. It is extensively exploited by cereal crops. The magnetic average susceptibility is 23.42 10-8 m3 / kg. The third zone is a soil which evolves under a natural herbaceous coverage (alfa) moderately dense. The average of the magnetic susceptibilities of this zone is 13.75 10-8 m3 / kg. The fourth zone completely lost its soil, the substratum is affected itself. The average of the magnetic susceptibilities of this zone is 6.5 10-8 m3 / kg. By comparing the magnetic susceptibilities of these degraded soils and their evolution in depth to those of a stable soil (204.04 10-8 m3/kg) we notice a big difference which allows to estimate the state of their degradation and to determine the factors favoring this degradation. The position of cores on the hillside allowed to have an idea on the particles redistribution by the streaming and consequently on the geodynamics processes of the hillside surface