Soil is the medium of growth of natural vegetation on earth’s surface. Various factors affect its composition such as climate, water level, biological properties and Salinity etc. The Salinity of soil refers to the amount of salts in the soil and it can be estimated by measuring the electrical conductivity (EC) of an extracted soil solution (EC increase with increase ion concentration). Salinity measurements are an important aspect of soil, crop and environmental protection, research and management.
Soil Salinity Tester measures the total amount of soluble salts in solution in a given soil sample. These tester based on electrical conductivity or total dissolved solids/ions measurements.
Applications of Soil Salinity Tester are:
- Efficient monitoring of Soil Salinity.
- Plant nutrient status and Fertigation.
- Pollution and land reclamation.
- Soil moisture mapping.
Two common ways for measuring Soil Salinity
- Electrical Conductivity; EC meters measures how much electricity moves through a solution – the saltier the solution, the more the electricity moves through it, and higher the conductivity reading. EC for soil is measured in dS/m (deciSiemens/metre).
- Total dissolved solids or total dissolved ions; measures how much salt is dissolved in soil solution. It is measured in units of mg/l (milligrams/litre) or ppm (parts per million). Higher readings mean more salt is present in the solution.
Effect of Soil Salinity on Plant Growth
Salinity can affect plant growth in several ways, directly and indirectly. High concentration of salt in soil can deteriorate the agricultural value of land.
Direct soil salinity damages
- Decreased water uptake; High salts concentration results in high osmotic potential of the soil solution, so the plant has to use more energy to absorb water. Under extreme salinity conditions, plants may be unable to absorb water and will wilt, even when the surrounding soil is saturated.
- Ion-specific toxicity
When a plant absorbs water containing ions of harmful salts (e.g. Sodium, Chloride, excess of Boron etc.), visual symptoms might appear, such as stunted plant growth, small leaves, marginal necrosis of leaves or fruit distortions.
Indirect soil salinity damages
- Interference with uptake of essential nutrients
An imbalance in the salts content may result in a harmful competition between elements. This condition is called “antagonism“, i.e. an excess of one ion limits the uptake of another ion.
- Sodium effect on soil structure
In saline soils, sodium replaces calcium and magnesium, which are adsorbed to the surface of clay particles in the soil. Thus, aggregation of soil particles is reduced, and the soil will tend to disperse. When wet, a sodic soil tends to seal, its permeability is dramatically reduced, and thus water infiltration capacity is reduced as well. When dry, a sodic soil becomes hard has the tendency to crack. This may result in damages to roots.
Factors affecting soil salinity
- Irrigation water quality; the total amount of dissolved salts in the irrigation water, and their composition, influence the soil salinity. Therefore, various parameters, such as source water EC and its minerals content should be tested.
- Fertilizers applied; The type and amount of fertilizers applied to soil, affect its salinity. Some fertilizers contain high levels of potentially harmful salts, such as potassium chloride or ammonium sulphate. Overuse and misuse of fertilizers leads to salinity buildup, and should be avoided.
- Field’s characteristics;a poorly drained soil might reach salinity level that is harmful to the plants and to the whole crop. A soil that was not flushed after a previous growing cycle might contain high level of accumulated salts.