Different methods for predicting soil hydraulic properties: estimation of hydrolimits in NW Spain

Abstract

Different indirect methods have been developed for modelling and estimating soil hydraulic properties, particularly hydrolimits, based on properties that can be easily measured. All these methods are based on the use of pedotransfer functions (PTFs). In the study, the use of different PTFs developed by international authors using SOILPAR 2.00 and by Spanish authors such as Soto et al. (2001), who developed a PTF for NW Spain, is analyzed and compared with the use of a third approach at the local level. This third approach develops specific PTFs for the study area, both considered as a whole and divided into three categories according to soil, crop type and rooting depth. Favourable results were obtained for permanent wilting point (PWP) with the three approaches based on data from direct estimation with a pressure plate (PP) and a water activity meter (WAM). In regard to SOILPAR, the most suitable models were Mayr-Jarvis for WAM and EPIC for PP, with a value of R2 0.81 in both cases. The maximum value obtained for R2 using regional PTFs was 0.66. The development of specific PTFs for the study area revealed the most appropriate method. In the case of specific PTFs, the results were favourable, obtained values of R2 above 0.8, for estimates of permanent wilting point (PWP), field capacity (FC) and available water content (AWC). The results for FC and AWC were favourable when the area was divided according to the categories considered.