Ideal Soil Salinity Level
Non-saline soil is considered the best type of soil for growing most plant species, as it contains very low levels of salts such as sodium, potassium, magnesium, and calcium. The salinity of non-saline soil is expressed as being less than 2 dS/m (decisiemens per meter).
Below are other soil salinity classifications:
- Low-salinity soil: Contains low salt levels that most plants can tolerate, though growth may be slightly affected. Its salinity ranges between 2–4 dS/m.
- Moderately saline soil: The growth of most plants is significantly affected, leading to reduced yield. Salinity ranges from 4–8 dS/m.
- Highly saline soil: Most crops are harmed due to salt levels ranging between 8–16 dS/m.
- Very highly saline soil: Crops cannot survive, including most salt-tolerant plants. Salinity exceeds 16 dS/m.
How to Measure Soil Salinity
Soil salinity is measured using electrical conductivity meters, as high salt levels increase the soil’s ability to conduct electricity. Soil samples may be tested directly in the field or taken to a laboratory.
Salinity is expressed in dS/m, and electromagnetic induction devices may also be used for salt measurement.
How to Reduce Soil Salinity
Soil salinity can be reduced or prevented using several agricultural practices, including:
- Improving field drainage through deep tillage.
- Flooding fields with low-salinity water to leach salts deeper into the soil.
- Reducing evaporation by keeping the soil covered with crops or mulching materials.
- Treating soil with chemical amendments such as gypsum, which reacts with sodium.
- Choosing salt-tolerant crops instead of conventional ones.
Negative Effects of Soil Salinity
Soil salinity negatively impacts many environmental and agricultural aspects:
1. Agricultural Production
High salinity prevents plants from properly absorbing water, leading to osmotic stress. It also affects the absorption of nitrogen and other nutrients. As a result, plant growth slows or stops, reducing yield.
2. Water Quality
Salts may leach into freshwater bodies, degrading water quality and harming drinking water sources, irrigation water, and aquatic life.
3. Biodiversity
When plants fail to grow in saline soils, herbivores lose their food sources, disrupting food chains and reducing biodiversity.
4. Soil Erosion
High salinity forces water to the soil surface, reducing vegetation cover and increasing erosion.
5. Flooding
Saline soil absorbs less water, increasing the risk of flooding during heavy rainfall or river overflows.
Summary
The ideal soil salinity level for agriculture should be below 2 dS/m. Higher salinity negatively affects plant growth, soil structure, biodiversity, and water quality. Although soil salinity can cause severe problems, it can be managed through proper drainage, leaching, gypsum application, and planting salt-tolerant crops.
