The salt content of the soil determines its salinity, and the process of raising the salt content is known as salinization. Salts are present in water and soils naturally. Natural processes like mineral weathering or the slow retreat of an ocean can also result in salination. It may also result from man-made activities like irrigation and salting of the roads. This article will explain to you about Salinization which will be helpful in preparing the Agriculture Syllabus for the UPSC Civil Service exam.

Salt affected Soil

Distribution of Saline soil

• Areas of western Gujarat and Kachchh: The southwest monsoon facilitates the introduction of seawater into the soil.
• Seawater intrusion in the delta area of the east coast and the Sundarbans encourages salinity in the soil.
• In the Punjab and Haryana region, poor drainage and excessive irrigation have turned alluvial soil into salty soil.
• When excessive irrigation is used in dryland areas, salt is accumulated in the top horizon of the soil, making the soil saline.

Causes of Salinization

• Excessive irrigation in dry weather encourages capillary actions that cause salt to build up in the top layer of soils.
• Alluvial soil and other types of soil can become saline due to inadequate drainage, waterlogging, or marshy places where soluble salt in water accumulates in the soil.
• Excessive irrigation and intensive farming results in salinization of alluvial soils.
• Due to the infiltration of seawater into the soil, soils in the delta area or coastal region become salty.
• When soluble salts are held in the soil, salinization develops. Either natural causes or incorrect human activity, notably in farming, contribute to it.
• The following factors also contribute to soil salinization:
  • Dry weather and low precipitation, which prevents the earth's excess salts from being washed away;
  • High evaporation rates, which add salt to the ground surface;
  • Poor drainage or waterlogging;
  • Irrigation with salt-rich water, which increases the salt content of the earth; and, finally, high evaporation rates.
  • Removal of deeply rooted vegetation, which raises the water table;
  • Seepage of sea salts into lower areas, which causes the sea level to rise; leakage into groundwater from geological deposits;
• Seawater submersion followed by salt evaporation, coastal winds that transport salty air masses to neighbouring locations, improper fertiliser application when excessive nitrification speeds up soil salinization, and more are all contributing factors.

Indicators of Salinization

• By examining the soil surface, rate of water infiltration, and plant condition, salinization may be seen visually.
• The indications worsen as the salinization process continues. For instance, a minor surface whitening transforms into discrete salt crystals.
• There are indirect signs of increased salt content in addition to visible changes such as poorer water quality or animal behaviour such as cattle not drinking water because it tastes salty are examples of this.
• In addition to eye assessment, there are more accurate ways to evaluate soil salinity, such as using specialised equipment to test the earth's electric conductivity.
• The conductivity of the solution increases together with the concentration of salt in the solution.

Consequences of Salinization

Production of Agriculture

• The amount of salts in the groundwater and the plant itself determine how much water is absorbed by plants.
• Osmosis is the mechanism by which water moves from locations with less salt concentration to those with greater concentration by being absorbed.
• The soil's osmotic potential is essentially negative when the salt content is too high.
• Osmotic stress occurs when plants are unable to absorb water, even though it is present in the soil.
• Because the earth is dry, the process essentially resembles drought stress.
• Ionic stress brought on by unfavourable ions in soil salts, such as chloride or sodium, is another way that soil salinity affects agriculture.
• These positively charged ions are poisonous in and of themselves, but they also prevent the uptake of other positively charged ions necessary for crop development (particularly potassium and calcium).
• Vegetation dies as a result, which is the same outcome as osmotic stress brought on by salinization.

Water Quality

• The issue with salinization is that salts not only build up in the ground but also seep into initially fresh water bodies, causing them to become salinized.
• It worsens irrigation and drinking water quality and contributes to the increasing salinization of drylands.
• One of the most severely impacted regions in the globe is the Colorado River basin.
• In the previous 60 years, the salinity of rivers in Colorado, Arizona, Utah, California, Wyoming, and New Mexico doubled.
• Other effects on water quality include:
  • ruins the taste of drinking water for people and domestic animals
  • pollutes farmlands
  • robs river species of their natural habitats
  • restricts access to fresh water for grazing cattle
  • deteriorates adjusting structures (concrete, wood, metal, etc.)

Biodiversity

• Strongly salinized soils are only suited for salt-tolerant species and halophytes, whereas non-saline soils have little effect on crops.
• Salinization thereby decreases ecological variety and jeopardises their ability to function normally.
• By reducing food chains and habitat sizes, a decrease in flora variety eventually results in a decrease in fauna as well.
• In freshwater lakes or rivers, salinization lowers biodiversity, reducing aquatic populations to just salt-tolerant species.
• As a result of farmers being driven to cultivate plants that can last in saline soils, soil salinization impacts agricultural diversity and consequently, food variety.

Soil Erosion

• Although soil salinization is a major issue in and of itself, it seldom occurs by itself.
• Due to the insufficient circumstances for plant growth, salinity results in a constant wetting of the ground surface and a lack of cover.
• These increase the likelihood of erosion in areas.

Flood Risk

• The earth's capacity for water infiltration is reduced by the rise in water table caused by salinization.
• Soils are unable to withstand significant water flows during torrential downpours or river flooding.
• Runoffs and flooding are the result of inadequate absorption.
• Strong water currents degrade aquatic environments, destroy agriculture, and destroy buildings.

Soil Salinity - Control and Prevention Methods

Reduced severity and extent of soil salinity is primarily a water management issue. There are two approaches to water management:

• by managing the area that contributes too much water to the soil (recharge area)
• by controlling the area where excess water rises to the surface (discharge area).

Recharge Management

• Reduce excess water infiltration into the soil in seep recharge areas by diverting surface water to downslope ponds.
• Keep the water table at a safe, low level. Over irrigation and a lack of natural drainage have raised water tables in some areas, necessitating the use of an artificial drainage system. The discharge of salty water from these drains may contribute to other problems offsite.
• Irrigate to keep soil salts at a level below the root zone.
• Cropping and tillage systems that promote adequate infiltration and permeability are recommended. This includes increasing organic matter in the soil and avoiding compaction.
• Plant crops that take advantage of the available soil moisture. Shallow-rooted crops may not be able to extract excess subsoil moisture, which can cause salinity.
• Using actively growing, deep-rooted plants, remove excess water from seep recharge areas.
  • Perennial plants and forages, particularly alfalfa, are useful for this purpose because they have a longer growing season and can absorb more water from a deeper layer of soil than annual plants.
• Return crop residue and manure to the soil to improve soilwater retention.
• Continuous cropping reduces summer fallow.
• Snow should be distributed evenly and not pond when it thaws.

Discharge Management

• Plant salt-tolerant crops.
• In high-risk areas, convert to permanent soil cover with salt-tolerant crops.
• Reduce deep tillage, which may bring salts from deeper soil horizons to the surface.
• To increase water use, plant forage crops or trees near bodies of water.
• Only install artificial drainage systems in the most severely affected areas.
• Remove seepage from irrigation canals, dugouts, and ponds.

Conclusion

Seawater submersion followed by salt evaporation, coastal winds that transport salty air masses to neighbouring locations, improper fertiliser application when excessive nitrification speeds up soil salinization, and more are all contributing factors to salinization. The effects of soil salinization on a variety of ecological and human elements of life are not good. It has an impact on the water supply and crop production sectors, increases the danger of flooding and soil erosion, and reduces biodiversity. The removal of soil salinity's detrimental impacts on the ecology and biodiversity would enable India to produce more crops from the same amount of fertile land.