Developments in soil salinity assessment, modeling, mapping, and monitoring from regional to submicroscopic scales

Abstract

Soil salinity spreads in more than 100 countries, and no continent is completely free from salinity. The level of salinity problem varies trans-country and even within the country at different locations, landforms, and irrigated agriculture regions to farmers’ fields. Local climatic, environmental, and management conditions determine the salinity problem. Current global estimates reveal over one billion ha area affected to various degrees of soil salinization. Soil salinization in the coastal areas due to seawater intrusion developed very strongly saline soils called sabkha. Human-induced salinization occurs in irrigated agriculture farms due to poor management of soil and water resources, high water table, poor drainage conditions, and the use of saline-brackish water for irrigation with less emphasis on leaching fraction. There have been signi ficant innovative advancements in technologies to assess, map, and monitor soil salinization spatially and temporally, from regional, national, to farm levels and submicroscopic scales. In this chapter, a comprehensive array of routine and modern techniques to address salinity issues at various scales using remote sensing and GIS, geophysical methods, and modeling are presented to guide stakeholders for the selection of appropriate technology to suit their needs and budget. A comprehensive review of such technologies and their applications has been included in this chapter, and salinity diagnostic procedures from regional to submicroscopic levels with relevant examples are described. Soil salinity classi fication systems used in various countries such as Australia, China, FAO-UNESCO, Russia, the USA, and Vietnam have been described. The chapter also presents global distribution of salt-affected soils.