Evolution de la conductivité hydraulique non Saturée en sols labouré et non labouré

Abstract

The blower disc is a tool particularly suitable for the measurement of the hydraulic conductivity of soils in the vicinity of the saturation potential for water between -25 and 0 cm of water, or to -2.5 - 0 kPa. It allows to explore the hydrodynamic operation of the macroporosity of soil in the pore diameter range equivalent greater than 0.12 mm. The work presented in this paper is devoted to the in situ hydraulic characterization of three soil types, near saturation, the use of the blower controlled suction disk. In the unsaturated area, the method (multi-potential, transient) was used in the field on the infiltration of water in the surface layer of soil. In this study, we sought to evaluate using infiltrometer to drive the hydraulic conductivity of the soil with successive potential infiltration -1 and -2 cm, measure the levels of initial and final water of surface horizon at lysimeter three boxes, each of 1.5 m2 having contrasting structures. This is a non-cultivated (SNT) for the first, cultivated soil (SC) who never worked for the second and worked soil (ST) last. The three sites whose conductivity has been studied and have different characteristics from each other at the time of the measurements. On each site were taken several series of blower door steps to get a better idea of the value of the hydraulic conductivity of surface horizons. The evolution of the hydraulic conductivity function h for the three study sites for potential h (-2, -1 cm) shows that the unworked Site (NTS) has a saturated hydraulic conductivity (Ksat = 3.87 cm / h) low compared to cultivated site (SC) and working site (ST) with respectively 7.94 and 12.72 cm / h. This hydraulic conductivity decrease is due to soil compaction for not worked Site (NTS). Note that the value of ks (3.87 cm / h) for not worked Site (NTS) is less rainfall intensities observed in Mediterranean environment. During rainfall, the low value of Ks causes heavy run off for this site. The presence of roots grown at the site (SC) and the tillage of the site worked (ST) may explain the abundance of pores in the range of the equivalent radius of potential measures (-2 and -1 cm) therefore the increase in hydraulic conductivity. The ground work has also led to an increase in pore size of the working site (ST).