Using Satellite Images for Multi-Annual Soil Salinity Mapping in the Irrigated Areas of Syrdarya Province, Uzbekistan

抄録

Soil salinity occurs on over 50% of the irrigated land and is one of the limiting factors for food crop production in the Central Asian region. Identification and mapping of salt-affected areas is a first step to coping with soil salinity. Traditional methods of mapping soil salinity, based on soil sampling and laboratory analyses, are time consuming and costly. Remote sensing-based approach has been developed to track historical changes in occurrences of soil salinity during the period 2000-2011. The method was tested for Syrdarya Province, Uzbekistan, where rapid salinity build-up has been recorded since 1965 when 300,000 ha of virgin land were developed based on canal irrigation. The seasonal Landsat images for the period 2000-2011 were used to calculate the radiance, reflectance and Normalized Difference Vegetation Index (NDVI) raster layers. The seasonal NDVI values were used to estimate the maximum annual NDVI values for three periods: 2000-2003, 2004-2007 and 2008-2011. The method was calibrated using field data from two farm unions, Gafur Gulyam and Galaba, located in two different parts of Syrdarya Province. The field data contains extensive measurements of bulk soil electrical conductivity using EM-38 and chemical analyses of soil samples. Soil salinity maps, created using Landsat images, have four classes: no salinity, low salinity, moderate salinity and high salinity. The results of soil salinity mapping indicated a significant increase in moderately saline soils from 40.7% to 45.4% and a decrease in low saline soils from 40% to 34.4% during the period 2000-2011.