Soil water retention and conduction properties assessed in field conditions

Abstract

Water and soil are the most important natural resources of our planet and the concern for their conservation must be permanent. Thus, the adoption of a more sustainable agriculture implies the efficient and responsible use of these resources. The comprehension of water movement within the soil profile plays a very important role in this context. The hydraulic properties of interest are the soil water retention curve, hydraulic conductivity as a function of water content or soil matric potential and hydraulic diffusivity as a function of soil water content. These properties depend on the size, shape, distribution and degree of pore interconnections. The instantaneous profile method is widely used for determining the hydraulic conductivity of unsaturated soil. However, there are some important issues to be clarified in the method, like the use of the soil water retention curve to estimate the water content, the existence of soil profiles with hardened layers, which can lead to misguided estimates, as well as the correct evaluation of the pore system of the soil. Given these facts, the goals of the project are to assess: (1) the hydraulic conductivity as a function of soil water content, in two structurally distinct soils, by the instantaneous profile method, estimating the water content via retention soil water retention curves determined in the laboratory and in field, with and without the removal of layers /overlying horizons and (2) the porous system of the soil using techniques of image analysis and correlate the results to the hydraulic conductivity of unsaturated soil obtained by the instantaneous profile method. (AU)