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.
Salinity can affect plant growth in several ways, directly and indirectly:
Direct soil salinity damages
Indirect soil salinity damages
Several factors affect the amount and composition of salts in soils:
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.
Irrigation regimen and type of irrigation system - The higher the water quantity applied, the closer soil salinity is to irrigation water salts concentration. When the soil dries, the concentration of salts in the soil solution is increased.
Since salts move with the wetting front, the salts accumulate in specific profiles according to the irrigation regimen and the type of irrigation used. For instance, when irrigating using sprinklers, water and salts move deeper, according to the soil's infiltration capacity and the water quantity, until they stop at a certain depth. When using drip irrigation - there is also a lateral movement of water and salts.
Field's characteristics and agricultural history - 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.