🧫 Saline-Sodic Soils

This lesson explains key concepts in a structured way and connects them to practical agricultural applications and exam-oriented understanding.

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Saline-Sodic Soils

Definition and Properties

Saline-sodic soils possess the combined characteristics of both saline and sodic soils. They are defined by the following criteria:

Parameter	Value
Electrical Conductivity (ECe)	> 4 dS/m
Exchangeable Sodium Percentage (ESP)	> 15
pH	Variable (usually < 8.5)

These soils contain both excess soluble salts and high exchangeable sodium. The presence of high salt concentration (high electrolyte level) keeps the clay in a flocculated state despite the high ESP. Therefore, the physical properties of saline-sodic soils are relatively better than those of purely sodic soils. The soil structure remains intact and permeability is reasonable as long as the salt concentration is maintained.

Critical Management Concern

The most important management consideration with saline-sodic soils is that if the salts are leached out without first replacing exchangeable sodium, the soil converts into a sodic soil. As the electrolyte concentration decreases during leaching, the dispersive effect of sodium becomes dominant, causing clay dispersion, structural collapse, and severe reduction in permeability. This makes the soil worse than its original condition.

The correct sequence is:

1. Apply calcium-rich amendments (gypsum) to replace exchangeable sodium
2. Then leach out the displaced sodium along with excess salts

If this sequence is reversed (leaching first), the result is a degraded sodic soil that is extremely difficult to reclaim.

Combined Management Approach

Step 1: Chemical Amendment

Apply gypsum or other calcium amendments to the soil surface. The calcium replaces sodium on the exchange complex while the existing high electrolyte concentration maintains soil structure and permeability, allowing the amendment to work effectively.

Step 2: Leaching

After sufficient sodium replacement has occurred, apply good quality irrigation water to leach the displaced sodium salts (Na2SO4) and remaining excess salts out of the root zone. Since calcium now occupies the exchange sites, the soil maintains its flocculated structure during leaching.

Step 3: Drainage

Install adequate surface and subsurface drainage to remove the saline leachate and prevent water table rise. Without drainage, salts accumulate again.

Step 4: Crop Selection

Select crops based on the residual salinity and sodicity levels:

• Initial phase — highly tolerant crops like barley, dhaincha (green manure), kallar grass, rice
• Intermediate phase — moderately tolerant crops like wheat, mustard, sorghum, cotton
• Later phase — gradually introduce less tolerant crops as soil conditions improve

Monitoring and Maintenance

Regular monitoring of ECe, pH, and ESP at different soil depths is essential to track reclamation progress. Key practices for long-term maintenance include:

• Use of good quality irrigation water (low EC, low SAR)
• Maintaining adequate drainage
• Regular addition of organic matter (FYM, compost, green manure) to improve soil structure
• Periodic soil testing (every 2–3 years)
• Avoiding over-irrigation that may raise the water table

The Indian Council of Agricultural Research (ICAR) through its institute CSSRI has developed comprehensive technology packages for reclamation of saline-sodic soils across different agro-climatic zones of India.

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Summary Cheat Sheet

Key Recall Points

• Saline-sodic soils show both salt accumulation and sodium hazard constraints.
• Management is staged: lower salinity, correct sodicity, and maintain drainage.
• Water quality and post-reclamation crop planning control relapse risk.

Exam Traps

• Treating saline-sodic soils like purely saline soils can worsen sodicity.
• Sodium correction without salt leaching is incomplete management.
• Reclamation outcomes differ by soil texture and groundwater behavior.

References

3 sources • [1] [2] [3]

[1]

ICAR-CSSRI Reclamation Packages for Saline-Sodic Soils

Official

[2]

FAO and USDA Principles for Mixed Salt-Affected Soils

Website

[3]

Reclamation Chapters in Standard Agronomy Texts

Book