Soil Salinity in South India: Problems and Solutions

Soil salinity is assuming menacing proportions for production of agricultural and horticultural crops in South India. South India comprises of Andhra Pradesh (AP), Tamil Nadu (TN), Karnataka, Kerala, Goa, and Islands in Bay of Bengal (Andaman and Nicobar) and Arabian Sea (Lakshadweep). It comprises central uplands, Deccan plateau (Karnataka plateau and Telangana plateau of AP), Nilgiri hills of TN, South Sahiailri, Eastern hills (Eastern Ghats, TN, upland) and Coastal Plains. The rainfall ranges from 400 to 500 mm in AP, 450 to 1300 mm in Karnataka, 500 to 1215 mm in TN, 100 to 450 mm in Kerala. Climate is mainly semi-arid in nature. Red soils (Alfisols, Inceptisols, and Entisols) make up about 60–65% and are well drained, blacksoils (Vertisols and Inceptisols) comprise about 20–25% and the rest are coastal sands. Soil salinity problems are encountered in almost all the districts in Karnataka and AP. The area extends to about 0.176 million ha in AP, 0.2 million ha in Karnataka, 0.0427 million ha in TN and about 0.03 million ha in Kerala. Introduction of canal irrigation water and use of underground saline waters accelerated the appearance of salt affected soils. Soil salinity observed in South India ranges from hydrometphic saline soils in Kerala to highly saline (EC 20–30 dS m−1) in Karnataka and AP. Saline soils were classified in to Natrargids or Solarthrids at subgroup level depending on the occurance of nitric or salic horizon within few centimetres of the surface. Soil salinity has reduced crop yields upto 50% and consequently cropping has been abandoned in many areas. Excess soluble salts can be removed through scrapping the surface salt crust or flushing and leaching or through subsurface drainage depending on the problem. Crops also vary in their ability to tolerate salinity at different stages of growth. In most crops subjected to irrigations with saline waters, germination and early seedling stages are generally the most sensitive and their tolerance increases with age. Salt tolerant varieties and nutrient management of crops in saline soils are important solutions for crop production under saline soils.