FAO’s Report On Soil Salinity

A report by the Food and Agriculture Organization (FAO) of the United Nations, titled ‘The Global Status of Salt-Affected Soils’, reveals that nearly 1.4 billion hectares of land, or 10.7 percent of the global land area, is affected by salinity.

About Salt-Affected Soils 

• Salt-affected soils are a specific group of soils that have elevated amounts of soluble salts (saline soils) or exchangeable sodium (sodic soils) that adversely affect the growth of most plants.

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Types of Salt-Affected Soils

• Saline Soils: Saline soil is defined as soil that has accumulated water-soluble salts such as chloride, sulphates, and carbonates. Saline soils tend to dominate in arid and semi-arid regions.
  • The soils have a stable structure.
  • Improving drainage, leaching of salts are some of the solutions for treating Saline soils.

• Sodic/ Alkali Soils: Sodic soils are formed when sodium ions are relatively higher than the other cations, impacting the soil structure. 
  • Sodic soils tend to dominate in semi-arid and sub-humid regions.
  • The soils have an unstable structure.
  • Soil amendments like addition of gypsum can improve sodic soil structure.

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Key Findings of FAO’s Report on Salt-Affected Soils

• Impact of Soil Salinity: An additional 1 billion hectares are at risk due to climate change and poor land management.
  • Salinity stress can reduce crop yields (e.g., rice and beans) by up to 70%, threatening global food security.
• Countries with the Largest Affected Areas: Australia (357 million ha), Argentina (153 million ha), Kazakhstan (94 million ha), Russia (77 million ha), and the U.S. (73.4 million ha).
• Countries with the Highest Proportional Impact: Oman (93.5% of land), Uzbekistan (92.9%), and Jordan (90.6%).
• Irrigated and Rainfed Cropland:
  • FAO’s global map of salt-affected soils reveals that 10% of irrigated cropland and 10% of rainfed cropland are currently impacted by salinity.This poses a significant threat to global food security.

• Status of salt-affected soils in India: 
  • Extent: India has 6.72 million ha of salt-affected soils (2.1% of its total land area).
    • Saline soils: 2.95 million ha.
    • Sodic soils: 3.77 million ha.
  • Most Affected States: Gujarat, Uttar Pradesh, Maharashtra, West Bengal, and Rajasthan made up about 75 per cent of the country’s salt-affected soils. 
  • Impact on Agriculture:
    • 20% of India’s agricultural land is impacted, especially in Jaisalmer, Gujarat coastline, and the Ganges basin.
    • The most cultivated crops grown on saline and sodic soils in India were rice, cotton, barley, sorghum and millets.
    • Almost 17 percent of the country’s irrigated agriculture had experienced secondary salinisation as a result of the use of brackish irrigation water.
• Causes of Soil Salinisation
  • Natural Causes: Climate change-induced aridity and freshwater scarcity.
    • Rising sea levels and thawing permafrost.
    • Irrigated soils in low rainfall regions also develop soil salinity and alkalinity due to accumulation of salts in surface layers through evaporating water.
  • Human-Induced Factors: Poor-quality irrigation water, inadequate drainage, and overuse of fertilisers.
    • Deforestation and removal of deep-rooted vegetation.
    • Overexploitation of aquifers and mining activities.
• Strategies for Management of Salt Affected Soils: The report offered a series of strategies for sustainable management of salt-affected soils to meet growing food demands. These were:
  • Mitigation: mulching, using interlayers of loose material, installing drainage systems and improving crop rotations
  • Adaptation: breeding salt-tolerant plants which flourish in mangrove swamps, tropical sand and cliff shorelines, and even salt deserts
  • Bioremediation: using bacteria, fungi, plants or animals to remove, destroy or sequester hazardous substances from the environment.
• Policy Recommendations
  • Develop legal frameworks for safeguarding natural saline ecosystems.
  • Promote sustainable soil management practices in irrigation areas at risk of salinization.

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Measures Taken For Tackling Soil Salinity In India

• Soil Health Card (SHC) is a printed report of a particular land holding which gives information on 12 soil parameters along with recommendation in dosage of nutrients to be utilised for different crops.
  • The Government issues individual soil cards to farmers once every 3 years.
  • The soil samples are tested for pH, Electrical Conductivity (EC), Organic Carbon (OC), Nitrogen (N), Phosphorus (P), Potassium (K), Sulphur (S), Zinc (Zn), Boron (B), Iron (Fe), Manganese (Mn), Copper (Cu) of farm holdings.
  • The card displays farmer’s detail, soil sample detail, soil test results and general recommendations.
• Promotion of Digital Agriculture: Digital agriculture refers to the integration of advanced technologies like IoT (Internet of Things), AI (Artificial Intelligence), big data, and machine learning into farming practices to optimize productivity, sustainability, and resource management.
  • Example: Smart irrigation systems integrate sensors and weather data to optimize water usage based on soil salinity levels, preventing over-irrigation and conserving water while managing soil salinity.

Way Forward

• Biodrainage: It is a technique used to lower groundwater levels in waterlogged areas by planting tree species that remove excess water through transpiration. 
  • This preventive method helps avoid salinity and waterlogging issues in canal command areas, especially when soils are still in the process of salinization. 
  • However, if the soils are already salinized it has limited scope. 
  • Promising species for biodrainage include Eucalyptus, Populus, Casuarina, and Bambusa.
• Biosaline Agriculture: It involves using salt-tolerant plants to manage saline soils and reclaim degraded land. 
  • Example: Planting of Leptochloa fusca, Prosopis juliflora, and Acacia nilotica.
• Updation of Groundwater Quality Map: The existing groundwater quality map needs to be updated to reflect current conditions, especially with regard to over-pumping in good-quality zones and limited extraction from poor-quality areas
• Sustaining Productivity in Reclaimed Areas: Through conservation agricultural practices including enhanced use of green manuring / organic manures needs promotion.