Soil Salinity: A Closer Look at Soil Microbe Inoculation

Harvested Grain Field

While better farm practices have reduced the risk of soil salinity in Canada, there are areas where it remains a significant problem.  Salinity impacts crop growth, nutrient availability, and overall soil health. However, the addition of active soil microbes can result in improvements to soil health and minimize the overall impact of salinity. 

Salinity and Its Effects

Saline soils have excessive levels of soluble salts in the soil water.  Salts are naturally occurring in many of the sedimentary rock and glacial material in Canada.  Some of those salts, like Calcium, Magnesium carbonates, and Sulphates are slowly soluble and are beneficial to crop growth.  However, other salts like sodium chloride (NaCl) and calcium sulfate (CaSO₄), disrupt plant physiology and nutrient uptake. Salinity-induced osmotic imbalance restricts water absorption, inhibits enzyme activity, and damages cell membranes. As a result, crops suffer reduced yields and stunted growth.

Soil Inoculation for Salinity

For soil microbes to improve crop outcomes in saline conditions, the soil microbiome needs to consist primarily of salt tolerant microbes.  To achieve this, an addition of diverse and active fungi and bacteria is necessary.  Soil inoculants like H-Start are emerging as a viable way to introduce this diverse microbial community.  

Barley on salinity lajord3

Barley grown in saline conditions near Lajord, SK.
The plants on the left were grown in soil treated with H-Start. 
The plants on the right were not.

How Soil Microbes Affect Soil Salinity

Once present, these microbes impact the salinity response of a crop in several ways.  A diversity of fungi and bacteria provide the greatest mix of benefits. 

Stabilized Soil Aggregates

Soil microbes break down organic matter which creates more stable soil aggregates.  As a result, we see several actions taking place to reduce salinity. 

  • Improved water infiltration and drainage with large pore spaces helps move excess salts from the rooting zone.
  • A better rooting zone allows roots to penetrate more easily, take up water and nutrients, and maintain a better salt concentration balance.
  • The larger pores reduce the capillary rise which means less upward movement of saline water into the rooting zone.
  • Organic matter breakdown creates humus which acts as a sponge to hold water as well as bind salts to reduce the overall salt concentration.

Mycorrhizal Fungi

Mycorrhizal fungi form a symbiotic relationship with plant roots. They extend their fine filaments (hyphae) into the soil, significantly increasing the root surface area. 

  • In saline soils, where nutrients are often scarce due to high salt concentrations, mycorrhizal fungi help plants access essential nutrients such as N, P, and K.
  • They act as buffers, shielding plant roots from direct exposure to high salt concentrations.
  • Promote plant vigor, making them more resilient to salt-induced damage.

Plant-growth-promoting rhizobacteria (PGPR)

PGPR (Plant Growth-Promoting Rhizobacteria) are beneficial bacteria that reside in the rhizosphere, which is the soil region surrounding plant roots. PGPR play a crucial role in enhancing plant growth by promoting nutrient uptake, improving stress tolerance, and protecting against diseases. The positive effect of PGPR make them valuable in challenging environments, not just saline conditions.

Exopolysaccharides (EPS)

Exopolysaccharides (EPS) are compounds produced by microbes as a survival strategy under harsh environmental conditions including salinity. 

  • Create a protective shield around the seeds and plants they interact with. Seeds are protected from desiccation, pathogens, and the uptake of toxic metals. 
  • Bind to sodium salts making them less accessible to the plant.  
  • Contribute to improved soil aggregation.

Osmotic Imbalance and Water Movement

Water availability in saline soils decreases due to osmotic stress. The soil solution has a higher salt concentration than the plant cells.  As a result, water moves out of plant cells through osmosis, leading to dehydration and wilting. This imbalance affects crop health and productivity.  Soil microbes, especially rhizosphere bacteria, contribute to water balance regulation:

  • Microbes produce compounds called osmo-protective substances under saline stress conditions. These substances help maintain cell water balance and prevent excessive water loss from crop cells.
  • Microbes also produce phytohormones, which promote plant tolerance to stressors including osmotic stress.

Nutrient Cycling

Microbes have an important role in nutrient cycling.  This includes the release of essential nutrients like Iron, Zinc, and Copper which are often deficient in saline soils.

ACC Deaminase and Ethylene

In response to environmental stress, like saline conditions, plants produce more ethylene which can lead to growth inhibition and reduced crop yield.  Some soil microbes produce the enzyme ACC deaminase which reduces the levels of ethylene in the plant.

Learn More

If you’d like to learn more about the independent research trials and observations in saline and non-saline conditions, get in touch with our team.  We partner with several research organizations across Canada to test H-Start under different growing conditions and with different crops.