Soil Salinity in India: Causes, Prevention and Solutions

Table of Contents

• What is “Soil Salinity”?
• What are the Major Causes of Soil Salinity?
• How to Identify if Soil has become Saline?
• How to Prevent Soil Salinization?

• • Better Irrigation Practices
  • Improved Drainage System
  • Mechanical/Physical Methods to Combat Soil Salinity
  • Soil Conditioning
  • Crop Management
  • Monitoring and Early Detection

• Major States in India Affected by Soil Salinity
• What is the Difference Between Saline Soil and Sodic Soil?

What is ‘Soil Salinity’?

The term "salinity" refers to the concentration of salt in soil or water. A high concentration of salt in the soil can frequently result in 'soil salinity,' which harms the soil's alkaline level and crop production. Fertilizers used in farming are usually made up of salts like potassium, calcium magnesium, chloride, and ammonium sulfate. When these fertilizers are spread on fields in an excessive quantity it could lead to soil salinity. Salt-affected soils occur in arid and semi-arid environments where evaporation occurs much faster than precipitation.

There are two types of soil salinity – primary soil salinity and secondary soil salinity. The primary soil salinity is mainly caused by the presence of naturally occurring salt. Whereas the secondary soil salinity develops because of the excessive use of fertilizers used on agricultural land or poor water management.

In India, approximately 6.73 million hectares of land are affected by Soil Salinity. This constitutes around 2.1% of the country's total geographical area.

What are the Major Causes of Soil Salinity?

Natural (primary) and human-induced (secondary) are the two major causes of soil salinity. Lets discuss them in more detail.

Natural Causes of Soil Salinity (Primary): Soil develops from rocks and minerals that naturally contain high levels of salts (e.g., gypsum, halite). Weathering of such parent materials can release salt into the soil. Low rainfall is another reason of soil salinity. In coastal regions, excessive groundwater pumping and rising sea levels can result in the mixing of seawater with the freshwater supply. The seawater eventually makes its way to farmland, where, through evaporation, it is transformed into soil.

Human Induced Causes of Soil Salinity (Secondary): Poor irrigation practices, excess water from water logging or irrigation without proper drainage system are the examples of human induced causes of salinity. Farm fertilizers contain high levels of salt content such as Potassium and magnesium. When used in excess without a proper schedule, it can lead to increase of the salt concentration in soil.

How to Identify if Soil has become Saline?

• Look for Signs on the Soil Surface: If there is a white crust forming on the soil surface it might indicate that the soil has a high saline level. These white crusts (salt particles) form when water evaporates and leaves behind a film of dissolved salt.
• Plant Health Indicators: Look for any signs of stress such as yellowing, browning, or burning of leaf edges. If you notice a drop in crop performance, growth, or productivity, saline soil might be one of the reasons affecting plant health.
• Soil Testing: A common method to assess soil salinity is by measuring its electrical conductivity. High EC levels typically indicate a high concentration of salts. Send your soil sample to a lab for detailed analysis that can provide information on salt concentrations and specific ions (like sodium, chloride, and sulfate).
• Check for Water Quality: If you’re using groundwater or surface water for irrigation, testing the water for salt content can also help determine if salts are being introduced to your soil.

How to Prevent Soil Salinization?

Proper irrigation practices, improved drainage, crop management, soil conditioning, etc. are some of the preventive measures of soil salinity. Let’s have a look at each point:

Better Irrigation Practices

1. Check the quality of Water: Whenever irrigating crops make sure to use water with low salt concentration to prevent additional salt accumulation.
2. Drip Irrigation: This form of irrigation applies water directly to the root zone which helps reduce evaporation and any form of salt buildup on the soil surface.
3. Schedule your Irrigations: Apply water in amounts that meet crop needs without causing waterlogging or over-irrigation.
4. Leaching: Leaching means the removal of salt below the solum of the soil. Leaching with high-quality water is the only practical method for removing excess salt from the soil. In cases where salt has already accumulated, add more water on a regular basis to flush them below the root zone.

Improved Drainage System

1. Upgrade Drainage Systems: Effective drainage systems help remove excess water, lowering the water table and minimizing salt accumulation.
2. Surface Drainage: Proper land grading and contouring can direct excess water away from fields, preventing salt from being drawn upward.

Mechanical/Physical Methods to Combat Soil Salinity

1. Scrap the Salt: If white salt concentrations are apparent, remove them immediately from the field using household instruments like khurpi.
2. Trenching Method: The procedure involves excavating tiny pits in the field and transferring subsoil to the surface to bury saline soil.
3. Flooding of Salt: The affected soil is first flooded with high-quality, salt-free water, then the dissolved salts are flushed down drainage channels. Repeating this method improves results by lowering surface layer salt concentrations.

Soil Conditioning

1. Gypsum Application: Gypsum (calcium sulfate) can help replace salt on soil particles, improving soil structure and helping to leach excess salts.
2. Organic Matter: Add organic matter to improve soil structure, enhance water infiltration, and increase microbial activity, which can help break down salt-affected compounds.
3. Mulching: Organic or synthetic mulches reduce evaporation from the soil surface, limiting the upward movement and concentration of salts.

Crop Management

1. Salt-Tolerant Crops: Select crops that can tolerate higher salinity levels. Crop rotation with salt-tolerant species can also help manage soil salinity.
2. Cover Crops: Planting cover crops can help reduce evaporation, maintain soil structure, and improve overall soil health.

Monitoring and Early Detection

1. Regular Soil Testing: Regularly conduct soil tests that include electrical conductivity (EC) measurements, to monitor salt levels.
2. Visual Inspections: Watch for signs such as salt crusts on the soil surface or plant stress symptoms (e.g., stunted growth, and leaf burn), which can indicate emerging salinity issues.

Major States in India Affected by Soil Salinity

According to a report from the Central Soil Salinity Research Institute (CSSRI), following are some of the Indian states highly affected by soil salinity:

What is the Difference between Saline Soil and Sodic Soil?