Soil Salinization: Solving a Serious Agricultural Concern

Soil Salinization: Solving a Serious Agricultural Concern
External Guest Writer
July 15, 2022

What is Soil Salinization?

Soil salinization is a form of land degradation where water-soluble salts in the soil hinder plant growth, and disrupt the natural soil ecosystem. It is a growing environmental concern as soil salinity interferes with the nitrogen absorption of plant roots, stunting plant growth.

Soil salinity may kill plants depending on the salt concentration, and the type of salts present in salt-affected soil may cause soil productivity to dwindle. Chloride is poisonous to plant life, and will hinder plants from growing, creating infertile soil. Salt-affected soils have reduced nutrient content, as well as a barren ecosystem as the salt kills off beneficial microbes.

What Causes Soil Salinization?

Irrigation Water

Soil salinization is primarily caused by inappropriate irrigation practices, namely using irrigation water with high levels of dissolved salts. Soil salinization occurs when salt-affected irrigation water contaminates soil with high concentrations of salts. This salt accumulates over time, increasing the concentration of salt-affected soils.

Water Tables

Water tables may also contaminate soil as the water evaporates through the soil surface, leaving a salt accumulation within the soil. The rise in water tables may be caused by crop rotation, where deep-rooted crop plants are replaced with shallow-rooted plants that are absorbing the moisture from the water table.

Sea Level Rise

Rising sea levels is a devastating effect of climate change that affects soil health. Sea water is naturally saline, and when the sea level rises, it can leave traces of dissolved salts in the soil, creating saline soils. As of 2018, the rise in sea levels has already caused soil salinization to grow from 1% to 33% since the 1990s.

The Main Indicators of Soil Salinity

Salt tends to pull moisture from the air, and consistently damp soil is one of the indicators of salt-affected soils. Saline soil will not support most plant life as well, which will produce barren spots of land. Sodic soils, or soil that has greater than 6% salt content, may be completely barren of all vegetation. Other indicators include:

  • Waterlogged or Moist Ground Surface
  • Salt-tolerant Plant Growth
  • Failure of Seed Germination and Growth
  • Bare Soils or Bare Spots
  • Livestock Rejecting Groundwater
  • Groundwater Salinization

In mild cases, salt-affected soils will present waterlogged areas after rains as salt traps moisture in the soil. However, severe cases of saline soils will present barren lands with visible salt crystals present in salt-affected areas. There may or may not be salt-resistant vegetation dominating the area, such as the wiry eragrostis which can grow in harsh conditions.

The Negative Effects of Soil Salinization

Soil health is most at risk in soil-affected areas. Physical or chemical weathering may occur as a result of the high salt concentration in the soil, and plants may undergo osmotic stress due to sodic soils. Salt-affected soils cause both land and groundwater degradation, and can affect the environmental health of the surrounding natural resources.

Negative Effects of Soil Salinity:

  • Osmotic Stress in Plants
  • Stunted Plant Growth
  • Lower or Barren Crop Yields
  • Degraded Quality of Groundwater
  • Soil Erosion
  • Soil Nutrient Loss
  • Disrupted Soil Ecosystem
  • Decrease in Beneficial Microbes and Earthworms

Soil salinization does not only affect agricultural production, but the environment as a whole. Salts interrupt the ecosystem within the soil, killing off beneficial bacteria and earthworms that thrive on soil nutrients. Soil salinization also affects water quality, and diminishes the purity of groundwater.

How to Prevent Soil Salinization

There are two commonly practiced measures to prevent soil salinization: controlled drip irrigation, and planting of salt-tolerant crops. These practices are meant to reduce the amount of salt in the soil by flushing them out of the land.

Drip Irrigation

Drip irrigation is meant to flush out the excessive accumulation of salt in the soil by controlling salt levels in the root zone. The key to maintaining a balance of salt in the soil is to irrigate excess water from the amount the soil depletes over a period of time.

Already sodic soils, however, will need to be flushed out of salt accumulation before any agricultural production can start. This may be done with constant and controlled drip irrigation of low-salt water over the barren land to dissolve the salts, and flush them away from the soil over the course of days to weeks depending on the concentration of salt.

Planting Salt-tolerant Crops

Salt-tolerant plants are vegetation that can grow even in saline soils. Halophytes can decrease the salt concentrations, and salt-tolerant crops provide avenues for farmers to grow crops in salt-affected soils. Planting deep-rooted vegetation, such as trees, will help lower water tables, and reduce salinity in the soil.

Preventing Secondary Salinization

Roads and pavements are sometimes salted to kill weeds, as well as clear snowy pathways. This practice causes secondary soil salinization as the salts run off into soil. Halting this practice, and doing managed clearing programs is the proper way of preventing secondary salinization.

Salt and Soil

Salt is naturally present in soil, albeit in minute amounts. Excessive concentrations of salt in soil particles is a growing concern as climate change affects the quality of land and water resources. Without proper and active measures to prevent soil salinization, land will continue to degrade, and prevent plant life from thriving.