Abstract
Soil salinity is the most common land degradation agent that impairs soil functions, ecosystem services and negatively affects agricultural production in arid and semi-arid regions of the world. Therefore, reliable methods are needed to estimate spatial distribution of soil salinity for the management, remediation, monitoring and utilization of saline soils. This study investigated the potential of Landsat 8 OLI satellite data and vegetation, soil salinity and moisture indices in estimating surface salinity of 1014.6 ha agricultural land located in Dushak, Turkmenistan. Linear regression model was developed between land measurements and remotely sensed indicators. A systematic regular grid-sampling method was used to collect 50 soil samples from 0–20 cm depth. Sixteen indices were extracted from Landsat-8 OLI satellite images. Simple and multivariate regression models were developed between the measured electrical conductivity values and the remotely sensed indicators. The highest correlation between remote sensing indicators and soil EC values in determining soil salinity was calculated in SAVI index (r = 0.54). The reliability indicated by R2 value (0.29) of regression model developed with the SAVI index was low. Therefore, new model was developed by selecting the indicators that can be included in the multiple regression model from the remote sensing indicators. A significant (r = 0.74) correlation was obtained between the multivariate regression model and soil EC values, and salinity was successfully mapped at a moderate level (R2: 0.55). The classification of the salinity map showed that 21.71% of the field was non-saline, 29.78% slightly saline, 31.40% moderately saline, 15.25% strongly saline and 1.44% very strongly. The results revealed that multivariate regression models with the help of Landsat 8 OLI satellite images and indices obtained from the images can be used for modeling and mapping soil salinity of small-scale lands.
Highlights
Land degradation is one of the most important global concern of the 21st century, negatively affecting the productivity of agricultural lands, sustainability of ecosystem services and food security as well as the quality of life
Higher annual evaporation compared to the precipitation, and the saline character of groundwater in the region [31] caused an increase in salt content of soils in the area
The electrical conductivity (EC) value ranges from 3.0 dS m-1 to 35.6 dS m-1, and mean EC value was 11 dS m-1 which corresponded to strong soil salinity [33]
Summary
Land degradation is one of the most important global concern of the 21st century, negatively affecting the productivity of agricultural lands, sustainability of ecosystem services and food security as well as the quality of life. Soil salinity is one of the most important land degradation process, which threats agricultural productivity and sustainability in arid and semi-arid regions [1,2,3]. The accumulation of soluble salts in groundwater on soil surface causes primary soil salinity in arid and semi-arid regions where precipitation is less than evaporation, while irrigation of lands with high mineral content and drainage problems causes secondary soil salinity [4]. Reclamation of salt-affected lands is important to meet the food and fiber demands of increasing world population and ensure sustainable and economic use of agricultural lands. Mapping and monitoring of soil salinity are necessary to define the nature of salt-affected soils and to generate accurate and reliable information about the spatial and temporal expansion of salinity
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