The suitability of particular water for irrigation is governed by the following factors.
• Chemical composition of water (TSS, pH, CO3, HCO3, Cl, SO4, Ca, Mg, Na and B).
• Total concentration of soluble salts or salinity (EC).
• Concentration of sodium ions, in proportion to calcium and magnesium or sodicity (SAR).
• Trace element boron may be toxic to plant growth, if present in limits beyond permissible.
• The effect of salt on crop growth is of osmotic nature. If excessive quantities of soluble salts accumulate in the root zone the crop has extra difficulty in extracting enough water from salty solution, thereby affecting the yields adversely.
• Besides this, total salinity depends on the extent to which exchangeable sodium percentage (ESP) of soil increase as a result of adsorption of sodium from water. This increase depends on sodium percentage.
• Soil characteristics like structure, texture, organic matter, nature of clay minerals, topography etc.
• Plant characteristics like tolerance of plant varies with different stages of growth. The germination and seedling stages are usually more sensitive to salinity.
• Climatic factors can modify plant response to salinity. Tolerance to saline water irrigation is often greater in winter than in the summer. Rainfall is the most significant factor for the leaching of salts from the plant root zone. Temperature also plays a vital role.
• Management practices also play great role. Wherever saline water is used for irrigation, adoption of management practices which allow minimum salt accumulation in the root zone of the soil is necessary.
The primary parameters that have to be considered to ensure effective irrigation management for salt control are the water requirement of crop and quality of irrigation water. Correct irrigation should restore any soil water deficit to control salt levels.
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