EDAFOLOGÍA, VOL 13. (1), PP 44-55. 2006
EVALUACIÓN DEL AGUA ÚTIL A PARTIR DE CURVAS CARACTE- RÍSTICAS DE
HUMEDAD Y CURVAS DE INTRUSIÓN DE Hg
Ma J. FERNÁNDEZ RUEDA, A. PAZ & E. VIDAL
Facultad de Ciencias. Universidade da Coruña. Campus de A Zapateira s/n.
15071 A Coruña, España – Tel: (+34) 981 167 000 – Fax: (+34) 981 167 065 E-mail:
tucho@udc.ess
Soil pore-size distributions are described using different methods, but water retention cha- racteristic curve is the most widely used method. As an alternative mercury intrusion porosimetry may also be performed in order to assess pore-size distributions. The aim of this work was to compare soil available water as obtained by both techiques in soil samples with a wide range of textures. Soil water retention curves were measured by means of a Richards apparatus, at water potentials of -5, -10, -50, -100, -300, -1000 and -1500 kPa. Mercury intrusion porosimetry curves were measured by means of a Micromeritics 9310 porosimeter. Boths determinations were performed on 2-3 mm diameter aggregates for 20 soil samples. Available water obtained as the difference between water content at -10 kPa and at -1500 kPa was compared with storage porosity. Medium textured soil samples a significant relationship was obtained between available water measured with these two different methods. Mercury intrusion porosimetry understimates available water in clay tex- tured soil samples, whereas it was overestimated in coarse textured samples. Soil porosity system as asses- sed both in the wet state (pF curves ) and in the dry state (mercury porosimetry) indicates that increasing soil organic matter content increases mesoporosity (storage porosity), i.e. pore-sizes which are responsible for available water storage.
Key words: pF curves, Hg intrusion, diferential poroity, available
water.