Hydraulic properties of representative São Paulo State soils determined in evaporation experiments with polymer tensiometers

• Grant number: 11/23740-4
• Support type: Regular Research Grants
• Duration: April 01, 2012 - March 31, 2014
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Quirijn de Jong van Lier
• Grantee: Quirijn de Jong van Lier
• Home Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Correct estimates of soil water retention and conduction are important for forecasting and modeling in agro-ecology, hydrology and meteorology. Among methods for measuring soil water retention, the laboratory method with a funnel or pressure chamber with porous plate is the most common. For hydraulic conductivity, field and laboratory methods are available and in this case the methodological difficulties increase as the soil dries out due to the slowness of the process. The evaporation method is a feasible alternative for the determination of both water retention and hydraulic conductivity, but its application is usually limited to the measurement range of water filled tensiometers, the relatively wet range. The development of a new equipment, the polymer tensiometer, permits direct measurement of soil water tension down to the permanent wilting point, at 150 m tension. In this study the determination of water retention and hydraulic conductivity in eight common soil types in São Paulo State is proposed using the evaporation method together with polymer tensiometers. The tensiometers were acquired in a former Fapesp Project (2009/02117-7) and are available to be used in the presently proposed project. It is the aim to establish a laboratory method for the determination of soil hydraulic properties over a large range of water contents. Obtained information will be made available as Genuchten-Mualem and Brooks & Corey - Mualem parameters for water retention and hydraulic conductivity, determined for the entire range of water contents of agronomic and ecological interest, from close to saturation down to the permanent wilting point. The results will be compared to frequently used extrapolation equations. (AU)