Combating salinity

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Soil and water salinity can be prevented or reduced under the right conditions. The objective of combating salinity is to bring soil and water conditions back to levels that allow optimal crop production, or more precisely, to reduce the salt stress on crop production.

Preventing salinity in irrigation water supply

One option to reduce the accumulation of salts in agriculture is by reducing the salts in the irrigation water. This can be achieved through a regional approach to water management. A study of water volume and salt concentrations in the watershed could reveal where salts are mobilized into the water system. Activities can be employed to reduce these salts to enter the river system, such as managing drainage water within upstream irrigation districts through evaporation ponds, thus solidifying the salts and allowing easy disposal, as well as installation of groundwater interception schemes, where groundwater pumps are installed to intercept the saline groundwater that otherwise would discharge into the river system. The pumped water can be disposed of in evaporation ponds to solidify the salts for easier disposal. The intercepted salts will reduce impact on downstream areas. Examples of this approach are presented in the Murray-Darling salinity management framework

Leaching salts from the soil profile

Through allowing irrigation water applications to be higher than only the crop water requirement, leaching of salts through the soil profile can be achieved. This is only possible if sufficient water supply is available, and if the conditions of water disposal (drainage) are favorable. Leaching already occurs when the irrigation efficiency (defined as the crop water requirement divided by the applied water) is less than 1. This is common, since it is almost impossible to apply the exact amount that a crop requires. Under-irrigation, where less water is applied than needed for the crop results in an irrigation efficiency larger than 1, which indicates that there is no water available for leaching. Several methods to calculate leaching fraction are available to calculate the balance between required average root zone salinity and the volumes of excess water needed for leaching.

Increasing drainage

When leaching is applied without sufficient natural drainage, installation of additional man-made drainage is required. This can be done through open drains as well as through tile-drains. Several methods to calculate drainage design parameters are available to calculate drain interval distance, drainage installation depth, and tile drain diameter requirements.