Contribution à la planification territoriale : Élaboration de la carte de sensibilité du sol à l'encroûtement de la propriété de Torre Marimon et la municipalité de Caldes de Montbui

Both soil crusting and soil erosion involve the detachment and transport of particles. There are several common factors that affect them. The objective of this work is to generate a sensitivity map of soil crusting at small and large scales by studying the relationship between soil crusting, characterized by its mechanical impedance (IM), and water erosion. In order to do this, we established a methodology that consists of realizing the following specific objectives: First, we studied the factors affecting surface crusting in Torre Marimon (PTM) by measuring the evolution of the IM of the soil based on water content and tillage, using a manual penetrometer. Second, we studied the evolution of the IM of crusts generated in the laboratory in function with moisture (using soil texture and organic matter content) in order to better interpret the values obtained in the field and to determine the moisture level at which the crust becomes a true agricultural problem. Crusts were generated using the pulp saturation method, with a 1 cm thickness. IM was measured using a texture analyzer, "TAXT plus". Meanwhile, crust moisture was measured using the gravimetric method. Third, we mapped the PTM and the municipality of Caldes de Montbui (MCM) to determine the extent of soil erosion by water according to the RUSLE model. This was done using geographic information with the highest resolution and optimizing the calculation of RUSLE factors (mainly the LS factor, using a program that takes into account the cumulative length of slope in calculations). Eventually, we studied the correlation between the IM and the hydric erosion with the purpose of trying to obtain a model. Measurement of IM in the field showed that tillage reduces the resistance of soil to penetration and that loamy soils, especially the ones with less organic matter content, are the most susceptible to crusting. A very good exponential model explaining 83 per cent of the variation of IM as a function of moisture was obtained. Crust hardness was shown to increase exponentially in function with moisture decrease. Laboratory measurements showed big variations in IM as a consequence of slight moisture variations. In fact, 1M increased from 5 to 30 MPa as a result of very small moisture variations (2 per cent). Soil loss estimation was improved. The facteurLS.exe program produced LS values that are roughly comparable to those contained in the "RUSLE Handbook guidelines". Correlation between potential erosion and the average IM of the crusts, within a 0-5 per cent moisture range, showed a strong link. A good linear model that explains 81 per cent of the variation of average M was obtained. IM was shown to increase with increased erosion, a trend that can be explained by soil texture. By using this linear model, a sensitivity map of soil crusting was established both at the PTM scale and at the MCM level but with restrictions. We were able to identify areas with high sensitivity to crusting, requiring combative actions.