Explanation:

Explanation:

• Due to salinity, plants are not able to draw as much water from the soil. When the soil salinity levels are high enough, the water in the roots is pulled back into the soil. The plants are not able to take in enough water to grow.

• The major source of salinity problems is usually irrigation water.

• Salt-affected soils can be corrected by:

• Improving drainage: In soils with poor drainage, deep tillage can be used to break up the soil surface as well as claypans and hardpans, which are layers of clay or other hard soils that restrict the downward flow of water. Tilling helps the water move downward through the soil. Hence option 1 is correct.
• Leaching: Leaching can be used to reduce the salts in soils. Adding enough low-salt water to the soil surface to dissolve the salts and move them below the root zone. The water must be relatively free of salts (1,500 – 2,000 ppm total salts), particularly sodium salts. A water test can determine the level of salts in your water. Hence option 2 is correct.
• Reducing evaporation: Applying residue or mulch to the soil can help lower evaporation rates. As an increase in evaporation increases salinity. Hence option 3 is not correct.
• Applying chemical treatments: Before leaching saline-sodic and sodic soils, treating them with chemicals, to reduce the exchangeable sodium content reduces salinity. Gypsum is the most commonly used to correct saline-sodic or sodic soils. Hence option 4 is correct.