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Saline incrustation in a PVC irrigation pipe from Brazil. Soil salinity is the salt content in the soil; the process of increasing the salt content is known as salinization. [1] Salts occur naturally within soils and water. Salination can be caused by natural processes such as mineral weathering or by the gradual withdrawal of an ocean.
The indirect effects of waterlogging and soil salination occur directly on the land being irrigated. The ecological and socioeconomic consequences take longer to happen but can be more far-reaching. Some irrigation schemes use water wells for irrigation. As a result, the overall water level decreases.
Dryland salinity is a sign that the water balance of the nearby area of land or catchment has been altered. Clearing as little as 25% of a catchment can cause salinity to occur. In addition to adding extra recharge, salinity may also be caused if the aquifers discharge capacity has been exceeded.
However, if the soil is under-irrigated, it gives poor soil salinity control, which leads to increased soil salinity with the consequent buildup of toxic salts on the soil surface in areas with high evaporation. This requires either leaching to remove these salts or a method of drainage to carry the salts away.
In irrigated agricultural land, waterlogging is often accompanied by soil salinity as waterlogged soils prevent leaching of the salts imported by the irrigation water. From a gardening point of view, waterlogging is the process whereby the soil hardens to the point where neither air nor water can soak through.
From figure 1 it is seen that 800 mm of water (or 8000 m 3 /ha) is required to bring the soil salinity down to 60% of its original value in the soil layer at 40 to 60 cm depth. When the salinity must be less than 60%, extrapolation of the leaching curve, the use of a leaching equation (see below) or a leaching model like SaltMod is necessary to ...
The primary method of controlling soil salinity is to permit 10–20% of the irrigation water to leach the soil, so that it will be drained and discharged through an appropriate drainage system. The salt concentration of the drainage water is normally 5 to 10 times higher than that of the irrigation water which meant that salt export will more ...
The salt level is often taken as the soil salinity or the salinity of the irrigation water. Salt tolerance is of importance in irrigated lands in (semi)arid regions where the soil salinity problem can be extensive as a result of the salinization occurring here. It concerns hundreds of millions of hectares. [2]