Remote Sensing and Geographic Information System for Appraisal of Salt‐Affected Soils in India

Abstract

Quantification of the nature, extent, and spatial distribution of salt-affected soils (SAS) for India and the world is essential for planning and implementing reclamation programs in a timely and cost-effective manner for sustained crop production. The national extent of SAS for India over the last four decades was assessed by conventional and remote sensing approaches using diverse methodologies and class definitions and ranged from 6.0 to 26.1 million hectares (Mha) and 1.2 to 10.1 Mha, respectively. In 1966, an area of 6 Mha under SAS was first reported using the former approach. Three national estimates, obtained using remote sensing, were reconciled using a geographic information system, resulting in an acceptable extent of 6.73 Mha. Moderately and severely salt-encrusted lands having large contiguous area have been correctly mapped, but slightly salt-encrusted land having smaller affected areas within croplands has not been accurately mapped. Recent satellite sensors (e.g., Resourcesat-1, Cartosat-2, IKONOS-II, and RISAT-2), along with improved image processing techniques integrated with terrain and other spatial data using a geographic information system, are enabling mapping at large scale. Significant variations in salt encrustation at the surface caused by soil moisture, waterlogging conditions, salt-tolerant crops, and dynamics of subsurface salts present constraints in appraisal, delineation, and mapping efforts. The article provides an overview of development, identification, characterization, and delineation of SAS, past and current national scenarios of SAS using conventional and remote sensing approaches, reconciliation of national estimates, issues of SAS mapping, and future scope.

Soil Salinity Mapping and Monitoring in Arid and Semi-Arid Regions Using Remote Sensing Technology: A Review

“…The spatial, temporal and vertical variability in the soil profile are the limiting factors in the assessment and mapping of soil salinity using remote sensing data because the spectral reflectance is unable to provide information on the whole soil profile, as it only observes the soil surface [98,99]. Moreover, the surface characteristics in many cases may not be representative of the deeper soil profile [100].…”

“…Additionally, different plants generally grow in different levels of salinity, so that the NDVI is considered an uncertain indicator for soil salinity monitoring and mapping. Besides, the existence of halophytic plants may confuse soil salinity detection based on the NDVI due to mixing with the spectral signature of salt, which then will lead to classification errors [98]. Hence, to overcome this issue and remove classification errors to some degree, the SAVI index and other indices and enhancement models have helped to separate soil and vegetation signals [105].…”

From QTL to variety-harnessing the benefits of QTLs for drought, flood and salt tolerance in mega rice varieties of India through a multi-institutional network

“…Most rice cultivars cannot survive complete submergence for more than a week [10,11]. In India 30% of the rice growing area (12)(13)(14) Mha) is prone to flash flooding resulting in severe losses with average productivity of only 0.5 to 0.8 t ha -1 [12]. The late duration varieties grown in rainfed lowlands usually face submergence stress at seedling stage followed by drought stress during flowering leading to huge yield losses.…”

Regional scale soil salinity evaluation using Landsat 7, western San Joaquin Valley, California, USA

“…Maps inventorying salinity and monitoring the spatio-temporal changes in salinity for the WSJV are vital to the management of salinity and allocation of limited water resources, particularly during recurring periods of drought. Recent advances in the use of satellite imagery (Metternicht and Zinck, 2003;Caccetta et al, 2010;Furby et al, 2010;Lobell et al, 2010;Singh et al, 2010) and electromagnetic induction (Corwin and Lesch, 2014) have made positive strides in regional-scale salinity assessment.…”