Soil Salinity and Salinisation in India Explained

In India, soil salinity is the build-up of soluble salts, and sometimes of sodium, in the root zone of farmland to a level that stunts crops and cuts yields, and it affects millions of hectares across the Indo-Gangetic plains, the arid west and the coasts. Salinisation, the process that creates these soils, is often called a silent disaster because it advances slowly, leaves white crusts on the ground and usually follows the very irrigation that made the land productive.

Salt-affected land is not an exotic problem on the margins of Indian agriculture. It runs through the wheat and rice belt of Haryana, Punjab and Uttar Pradesh, the canal commands of Rajasthan and Gujarat, the black soils of Maharashtra and Karnataka, and the delta lands of West Bengal and Tamil Nadu. This explainer describes the types of salt-affected soil, their causes, their extent in India and the proven ways of bringing such land back into production.

Key Takeaways

• Soil salinity covers two related problems: saline soils, which hold too many soluble salts, and sodic or alkali soils, which hold too much sodium that ruins soil structure.
• The leading cause in India is human-made: irrigation without adequate drainage raises the water table and brings salts to the surface as water evaporates.
• Salt-affected soils in India are commonly estimated at close to seven million hectares, and projections suggest the area will grow if irrigation practices do not change.
• Coastal salinity is a separate pressure, driven by seawater intrusion, tidal flooding, cyclone surges and sea-level rise in places such as the Sundarbans and Gujarat.
• Gypsum with leaching is the classic cure for sodic soils, while subsurface drainage is the main fix for waterlogged saline soils.
• Salt-tolerant crop varieties, trees and good water management allow farmers to keep producing on land that would otherwise be abandoned.

What is soil salinity?

Soil salinity is the concentration of dissolved salts in soil, and when the level becomes high enough, plants cannot take up water properly and their growth is reduced. Salts are a natural part of all soils, but problems arise when they accumulate faster than rain or irrigation water can wash them away.

The salts involved are mostly chlorides, sulphates, carbonates and bicarbonates of sodium, calcium and magnesium. A plant root draws water from soil by osmosis, so when the water in the soil is saltier than the water inside the root, the plant struggles to absorb it, even if the soil appears wet. Farmers describe the result as crops that wilt in moist ground. Some salts, notably sodium and chloride, are also directly toxic to plant tissues.

Soil scientists measure salinity by the electrical conductivity of the soil’s saturation extract, expressed in decisiemens per metre. A reading above about four decisiemens per metre is generally treated as saline, though sensitive crops can suffer at lower levels. The measurement is useful because dissolved salts conduct electricity, and a handheld meter gives a quick field check.

What is the difference between saline and sodic soils?

Saline soils contain too many soluble salts but have a normal structure, whereas sodic or alkali soils contain high exchangeable sodium that makes the soil sticky, dense and alkaline. The two need very different treatments, so telling them apart is the first step in any reclamation plan.

In sodic soil, sodium ions replace calcium on the clay particles, which then disperse when wet. The soil seals at the surface, blocking air and water, so seedlings struggle to emerge and roots cannot penetrate. When dry, such land bakes into a hard crust. The high pH also locks up nutrients such as zinc and iron, so even crops that survive often look yellow and stunted.

What causes soil salinity in India?

Soil salinity in India is caused by natural conditions such as arid climate and salt-rich parent material, but the area has been vastly expanded by human activity, above all irrigation without enough drainage. The common thread is that water evaporates and the salts it carried are left behind.

• Over-irrigation and waterlogging: excess irrigation raises the water table, and when it comes within a couple of metres of the surface, capillary rise draws salty water up and evaporation deposits the salt in the root zone.
• Canal seepage: unlined canals leak water into the ground, lifting the water table around command areas in Haryana, Punjab, Uttar Pradesh and Rajasthan.
• Poor drainage: flat plains and heavy clay soils slow the movement of water, and drains that are blocked or never built let salts accumulate.
• Saline groundwater: pumping brackish tubewell water for irrigation adds salts year after year, particularly in arid parts of Rajasthan, Gujarat and Haryana.
• Coastal intrusion: seawater enters aquifers when too much fresh groundwater is pumped, and tides, storm surges and cyclones flood fields with salt water.
• Arid climate: high evaporation and low rainfall mean there is little water to flush salts out of the soil.
• Poor-quality water use: irrigating with water high in sodium or bicarbonate gradually creates sodic conditions.

The Green Revolution intensified some of these pressures. Rice and wheat cultivation in the northwest relied on heavy irrigation, and in areas where canals were added without a matching drainage system, waterlogging and salinisation followed within a few decades. The problem is therefore a classic example of how success in one area can seed trouble in another.

How much salt-affected land does India have?

India has roughly seven million hectares of salt-affected soils, according to widely cited estimates from the Indian Council of Agricultural Research and its institutes, and the area may rise substantially by mid-century if trends continue. A little under half of this is saline and the rest is sodic or saline-sodic, though the exact split depends on the survey.

Gujarat has the largest share of salt-affected land, much of it coastal or in the Kachchh region, where natural salinity is combined with human pressure. Uttar Pradesh has the largest area of sodic soils, in the central and western plains. Maharashtra, West Bengal, Rajasthan, Tamil Nadu, Andhra Pradesh, Haryana, Punjab, Karnataka and Odisha also contain significant areas.

These figures are estimates, and different surveys give different numbers because salinity changes with season, depth and irrigation. Experts agree on the direction of travel. Mapping from satellites and soil surveys, led by the ICAR-Central Soil Salinity Research Institute at Karnal and by the National Bureau of Soil Survey and Land Use Planning, continues to refine the picture. The economic cost is also considerable, running to a loss of many million tonnes of crop production in a year, and it falls hardest on small farmers who cannot afford to treat or leave the land.

How does soil salinity affect crops and farmers?

Soil salinity reduces crop yields by limiting water uptake, causing nutrient imbalance and poisoning roots, and in severe cases it leaves land too barren to cultivate at all. Germination is often the first casualty, so fields appear patchy and thin.

Crops vary widely in tolerance. Rice, wheat, mustard, barley, cotton and sugar beet are more tolerant than pulses, maize, groundnut and many fruit trees such as citrus, mango and guava, which suffer even at modest levels. Barley, date palm and sugar beet are among the most salt-tolerant of cultivated plants, whereas beans and most vegetables are sensitive.

The human cost follows. Yields fall, input costs rise as more irrigation and fertiliser are applied to compensate, and in extreme cases families abandon fields or migrate. Salt-affected land often belongs to farmers at the tail end of canals or in poorer coastal villages, so the burden is unequal. In the Sundarbans, repeated flooding by saline water after cyclones such as Aila in 2009 and Amphan in 2020 has forced households to shift from rice to other livelihoods such as aquaculture.

How is salt-affected land reclaimed?

Salt-affected land is reclaimed by removing or neutralising the excess salts and sodium, which usually means applying gypsum to sodic soil, flushing salts with good-quality water and installing drainage so that the water table stays low. The method depends on whether the soil is saline, sodic or both.

Gypsum for sodic soils

Gypsum, or calcium sulphate, supplies calcium that replaces sodium on the clay particles. The released sodium can then be washed below the root zone as soluble sodium sulphate. Farmers typically level and bund the field, apply gypsum based on a soil test, flood it to leach the salts and then grow salt-tolerant crops such as rice. India’s large uptake of this method, notably the sodic land reclamation projects in Uttar Pradesh, brought several hundred thousand hectares back into production over recent decades.

Drainage and leaching for saline soils

Saline soils are treated by leaching, meaning applying more water than the crop needs so that salts are carried down and out. This works only if the water can drain away, so surface or subsurface drainage is essential. Subsurface drainage systems, in which perforated pipes buried below the field carry off salty water, have been tried in Haryana, Rajasthan and Gujarat with good results, although cost and the disposal of the saline drainage water remain challenges.

Other practical measures

• Organic matter: farmyard manure, green manure and press mud improve structure and help gypsum work.
• Irrigation management: lining canals, using drip or sprinkler irrigation, and avoiding over-watering lower the water table.
• Mulching and ridge planting: ridge and furrow systems keep seeds away from the saltiest soil, and mulches reduce evaporation.
• Bio-drainage: planting water-hungry trees such as eucalyptus pumps water out of the soil and lowers the water table.
• Conjunctive use: blending canal and saline groundwater lets farmers use poor water without damaging the soil.

Which salt-tolerant crops and trees can be grown?

Salt-tolerant crops and trees allow farmers to produce food and fuel on land that cannot yet be fully reclaimed. Indian research has developed several improved varieties of rice, wheat, mustard and other crops that tolerate saline or sodic conditions better than ordinary types.

The ICAR-Central Soil Salinity Research Institute has released many such varieties, including rice lines in the CSR series, wheat lines in the KRL series and salt-tolerant mustard, and it has developed agroforestry systems. Suitable trees for sodic and saline sites include Acacia nilotica (babul), Prosopis juliflora, Tamarix, Casuarina, Eucalyptus and Terminalia arjuna, while grasses such as Karnal grass (Leptochloa fusca) are used as fodder and as pioneer cover. On coastal lands, farmers adopt saline-tolerant traditional rice varieties and integrated systems that combine shrimp or fish ponds with crops and mangroves.

These options are not a substitute for fixing the cause. Salt-tolerant crops can sustain yields on marginal land, but if the water table keeps rising, even tolerant plants eventually fail. The best programmes combine tolerant varieties with better water management and drainage.

Can soil salinity be prevented?

Soil salinity can largely be prevented by applying only the water crops need, keeping the water table deep, lining leaky canals and providing drainage in every irrigation scheme. Prevention is far cheaper than reclamation, which can take years and substantial money.

Policy plays a role. Efficient irrigation under programmes such as the Pradhan Mantri Krishi Sinchayee Yojana, which promotes micro-irrigation, helps reduce the over-watering that drives waterlogging. Monitoring of groundwater levels and quality, crop diversification away from water-hungry rice in vulnerable areas, and the use of treated or good-quality water for leaching all help. Farmers who test their soil and water regularly can spot rising salinity before yields collapse. Climate change adds urgency, because rising seas, stronger cyclones and higher evaporation will push salinity further inland.

Bottom Line

Soil salinity is a slow-moving threat that has already taken millions of hectares of Indian farmland out of full production, and it is the price of irrigation without adequate drainage. The remedies are well known: gypsum for sodic soils, drainage and leaching for saline soils, salt-tolerant crops and careful water use. What is needed now is the will and funding to apply them at scale.

Frequently Asked Questions

What is soil salinity in simple terms?

Soil salinity is the build-up of too much salt in the soil, which makes it hard for plant roots to absorb water and reduces crop growth. It often shows up as white crusts on the ground and patchy, stunted crops. It is usually caused by irrigation without proper drainage.

What is the difference between saline and sodic soils?

Saline soils contain too many soluble salts but usually keep a good soil structure, while sodic soils contain too much exchangeable sodium, which makes the soil dense, sticky and highly alkaline. Saline soils are fixed mainly by leaching and drainage, and sodic soils need gypsum as well. Some soils are both.

How much land in India is affected by salinity?

Estimates from Indian agricultural research institutions put salt-affected land at roughly seven million hectares. Gujarat, Uttar Pradesh, Maharashtra, West Bengal and Rajasthan are among the states with the largest areas. The figure is approximate, and projections suggest it could increase if irrigation and drainage practices do not improve.

What causes soil salinisation in Indian farmland?

Soil salinisation in Indian farmland is mainly caused by over-irrigation, poor drainage, canal seepage, the use of saline groundwater and, near the coast, seawater intrusion and flooding. In dry regions, evaporation leaves salts behind. Arid climate and naturally salty soils add to the problem, but human irrigation practice is the biggest driver.

How is salt-affected soil reclaimed?

Salt-affected soil is reclaimed by flushing salts out with good-quality water, installing drainage to keep the water table low, and applying gypsum to sodic soils to replace sodium with calcium. Organic manures and salt-tolerant crops and trees help restore productivity. The right mix depends on a soil test.

Which crops can grow in saline soil?

Salt-tolerant crops include barley, mustard, cotton, sugar beet and improved salt-tolerant varieties of rice and wheat developed by Indian research institutes. Trees such as babul, tamarisk, casuarina and eucalyptus also grow well on affected land. Sensitive crops such as pulses, maize and many fruit trees should be avoided until the soil is reclaimed.

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