1A Tool for Estimating Soil Water Available for Plants Using the 1:1,000,000 Scale Soil Geographical Data Base of Europe

For agricultural or environmental purposes, the European Union needs to have tools giving sufficient and reliable information on soils at a global scale for decision making. For example, the MARS project developed an agrometeorological model for predicting yield at regional and national levels for the main crops in Europe. The knowledge of Soil Water Available for Plants (SWAP) is essential for estimating the water balance. The Soil Geographical Data Base of Europe at scale 1:1,000,000 represents the most detailed data source on soil covering the whole European territory. Using this database, a tool for estimating SWAP was developed. This tool estimates SWAP using basic variables from the Soil Geographical Data Base, variables estimated by pedotransfer rules stored in a knowledge data base, and users-defined parameters. The calculation is made on three layers which limits are determined by the users-defined parameters and the estimated depth of soil. The available water for each layer is calculated using three suction limits: at-5 kPa for field capacity,-200 kPa for the easily available water limit, and-1500kPa for the wilting point. The SWAP corresponds to the summing of the available water of each layer. The tool was developed within the same system as those used to store the Soil Geographical Data Base, and the knowledge database. This leads to an easy access to the results and allows easy thematic mapping. 2