Previous Year Question
Salinisation occurs when the irrigation water accumulated in the soil evaporates, leaving behind salts and minerals. What are the effects of salinisation on the irrigated land?
Correct Answer: B
Detailed Solution
Irrigation water contains a certain quantity of dissolved salts. During evaporation and transpiration by plants, water leaves the soil, but the salts remain behind. Repeated irrigation, high evaporation and inadequate drainage cause these salts to accumulate in the root zone.
High salinity increases the osmotic pressure of the soil solution. This makes it difficult for plants to absorb water from the soil and reduces seed germination, plant growth and crop production. Therefore, option (a) is incorrect.
Particularly in sodium-affected soils, fine soil particles expand and disperse. This destroys soil aggregates, blocks soil pores and severely reduces water infiltration and permeability. Consequently, some soils may become nearly impermeable.
A rise in the groundwater table and filling of soil air spaces with water are characteristics of waterlogging. Waterlogging may promote salinisation, but these are not direct effects of salinisation.