Monitoring of salt affected soils #x2014; A case study using aerial photographs, salyut#x2010;7 space photographs, and landsat TM data

摘要

Soils of part of Ukai#x2010;kakarapar Command area, Gujarat (India) have been mapped at 1:25, 000 scale using aerial photographs of December 1977. It was observed that about 36.3 of the area was affected by soil salinity/alkalinity. The test area has been remapped using Salyut#x2010;7 space photographs taken during Indo#x2010;Soviet joint flight in April, 1984. The area affected by soil salinity/alkalinity was found to be substantially higher (80.3). The earlier mapping using aerial photographs was done when the soil surface was compartively moist (December 1977) as compared to date of Salyut#x2010;7 photography (April 1984), when the soil surface was likely to be devoid of moisture and the salts moved to the surface. To have easy comparision with the map prepared by using aerial photographs, Landsat TM data of December, 1985 was used in which 45.7 of the total area was mapped as salt affected. The extent of area delineated using Landsat TM was higher than that of 1977 but much lesser than the area delineated using Salyut#x2010;7 (MKF#x2010;6M) photographs. This indicated that the increase in the extent of salt affected area in the map prepared using the MKF#x2010;6M photographs might be partly due to actual increase in the salinity/alkalinity and partly due to the seasonal affects. Among the various bands of MKF#x2010;6M, band #x2010;4 was found to be the best for delineating the salt affected soils. The boundaries were sharper in the FCC and band No.4 of MKF#x2010;6M than in the aerial photographs.