Executive Summary

Background

Salt-affected soils are soils with high amounts of soluble salts and/or sodium ions. The first global distribution of these soils was first estimated in the late 1970s at about 1 billion hectares. Since then, there has been inconsistent updates of the global distribution. Recent literature at the globalscale mostly use data that was collected in the late 1970s and still portray global distribution of affected areas at about 1 billion hectares. Evidently, a new update is necessary to improve knowledge of the status and actual distribution of salt-affected soils. Part of the reason for the inconsistent global update is due to unclear coordination for periodic data collection and harmonized data collection protocols to support it. The Global Soil Partnership (GSP) of the Food and Agriculture Organization (FAO) is leading global mobilization to kickstart information update from the country to global level. The GPS’s bottom-up approach is underpinned by the twin need to support countries to update their national information and to contribute to the update of global information of salt-affected soils. One of the challenges with this approach is the potential uncertainties due to differences in datasets and approaches by countries. The focus of this book is to provide guidelines for harmonizing input data and approaches for mapping saltaffected soils at all levels of information update. Developing spatial information of salt-affected soils Many methods exist in the literature for mapping salt-affected soils. They include methods based on soiltype mapsintegrated with expert opinions, remote sensing applications and soil indicator-based method. The requirements, limitations and example applications of these methods have been highlighted in this book. Prominence has been given to the indicator-based approach for mapping salt-affected soils because 1) the method is amenable to country-level harmonization of procedures, 2) it develops information of both salt-affected soils and soil properties related to salt problems, 3) the method is able to quantify mapping accuracy and uncertainty, 4) quantifies horizontal and vertical information. The description of its methodological steps has been illustrated using case-study test data from Northern Sudan and minimum requirement for input data, computer, and software. The intention is to present the steps as clearly and repeatable as possible to enable implementation with own datasets.

Resource mobilization

Developing information and updating the status of salt-affected soils is resource-intensive and should be properly planned. This book has dedicated the last two chapters for resources mobilization to build national information on salt-affected soils. It outlines key areas of focus for resource mobilization and steps for building technical resources to develop a harmonized database for assessing salt-affected soils. It also discusses steps for enriching spatial maps through value addition to improve their information resource.