Soil Salinity in India: Causes, Prevention and Solutions

Table of Contents

• Introduction
• What is ‘Saline Soil’?
  • Types of Soil Salinity
• Difference Between Saline Soil and Sodic Soil?
• Top States in India Afflicted by Saline Soil
• Causes of Soil Salinity
  • Natural Causes of Soil Salinity
  • Human Induced Causes of Soil Salinity
• How to know if your Soil is Saline?
• Prevention and Management of Saline Soil
  • Better Irrigation Practices
  • Improved Drainage System
  • Mechanical/Physical Methods to Combat Soil Salinity
  • Soil Conditioning
  • Crop Management
  • Monitoring and Early Detection

Introduction

Agriculture plays an important role in India’s economy. The agriculture sector supports around 47 percent of the country's population. For this reason, farmers need to make sure that their farmland has healthy soil in order to grow crops successfully. Crop cultivation, however, frequently fails for a variety of reasons, such as natural disasters or water scarcity. One of the most common reasons why crop cultivation often fails is due to Soil Salinity. 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. The most affected states include Gujarat, Uttar Pradesh, Maharashtra, West Bengal, and Rajasthan.

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. Fertilisers 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.

Soil salinity can be extremely detrimental to crop production and acts as one of the primary causes of land degradation. Higher saline levels in fields can typically result in lower agricultural production, poor plant growth, and the soil being entirely unusable for future farming.

Types of Soil Salinity

Primary Salinity – Primary salinity in the soil is mainly caused by the presence of naturally occurring salt. This type of soil salinity is frequent in arid or semi-arid environments with minimal rainfall and high evaporation levels.

Secondary Salinity - This type of salinity develops as a result of excessive fertiliser use on agricultural land or poor water management.

Difference between Saline soil and Sodic soil

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:

Causes of Soil salinity

Saline soils contain a high concentration of soluble salts, which can be harmful to plant growth and soil health. There are two main causes of Saline soil. Natural (primary) and human-induced (secondary).

Natural Causes of Soil Salinity (Primary)

Parent Material – 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.

Climate - In regions with low rainfall and high evaporation rates, water drawn from the soil surface evaporates quickly. As the water evaporates, it leaves behind salt that accumulate over time.

Seawater – In coastal regions, excessive pumping of groundwater and rising sea levels can result in the mixing of seawater with fresh water supply. The seawater eventually makes its way to farmland where due to evaporation it turns into soil.

Human Induced Causes of Soil Salinity (Secondary)

Over irrigation and Poor drainage – When irrigation is not done properly, and excess water is left behind which leads to water logging. As the water evaporates, it leaves salt behind. This is recurring in areas with naturally high salt content in the subsoil or groundwater.

Overuse of fertilizers – 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. This is especially common in areas where rain density is much lower than the rate of evaporation.

Disruption in farming – Removing vegetation (due to deforestation or any kind of land clearing) can disrupt the natural balance of soil moisture. When there is no plant uptake to help regulate water content, the water level can rise, bringing salt to the surface through capillary action.

How to tell if your Soil has Become Saline?

1. 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. Saline soil can appear compacted or have an unusual surface texture due to salt deposition.

2. 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.

3. 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).

4. 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.

Prevention and Management of Saline Soil

Managing and preventing saline soils requires a combination of preventive practices and rehabilitation approaches that address both the source of salinity and the effects it has on plant growth. Here are several strategies:

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.

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.