Reconnaissance mapping and management of salt-affected soils using satellite images

The Indo-Gangetic alluvial plain is subjected to large scale soil alkalizat ion. In order to map and characterize salt-affected soils, with the aim of applying management techniques, Etah district in Uttar Pradesh, located bet ween 26 degrees 45' to 28 degrees 02' N and 78 degrees 15' to 79 degrees 20 ' E was selected. Multidate, high resolution, IRS-LISS II, geocoded FCC ima ges on 1:50 000 scale were used. Integrating visual image interpretation, p hysiographic analysis, ground data and laboratory analysis of soil samples, a legend for mapping salt-affected soils ( SAS) was formulated. Based on v ariations in physicochemical properties: nature, intensity and depth wise d istribution of salts, five categories of SAS requiring specific reclamation measures were identified. Soil categories S2, S3 and S4 have a gypsum requ irement ( GR) of 20, 12 and 4 t/ha(-1) respectively. Reclamation of medium to heavy textured highly alkali soils requires the addition of amendments a nd a rice-wheat rotation for the initial 3-4 years. Under resource constrai nts, pit planting of Prosopis juliflora can bring about slow but effective reclamation. The soil category S5 is slightly alkali in the substratum, nee ding only biological reclamation by growing salt tolerant varieties of rice and wheat crops. Soils of category S1 are saline and need management by hy drological treatments. Incorporation of village boundaries on a map showing SAS would facilitate decision taking in planning reclamation projects and accelarate management operations directly at village level.