The correct answer is: Improper irrigation practices.
Salinity is a problem in some areas of Manipur due to improper irrigation practices. When water evaporates from the soil, it leaves behind salts. If the soil is not properly drained, these salts can build up and make the soil too salty for plants to grow.
Seawater intrusion is another cause of soil salinity, but it is not a major problem in Manipur. Poor drainage can also cause soil salinity, but it is usually not as severe as when it is caused by improper irrigation practices. Excessive fertilization can also contribute to soil salinity, but it is usually not a major problem unless it is done over a long period of time.
Here are some additional details about each of the options:
- Improper irrigation practices: When water is applied to soil, some of it evaporates and some of it seeps into the ground. The water that seeps into the ground can carry salts with it. If the soil is not properly drained, these salts can build up and make the soil too salty for plants to grow.
- Seawater intrusion: Seawater intrusion occurs when seawater moves into freshwater areas. This can happen when sea levels rise, when rivers and streams flow into the ocean, or when canals are built that connect freshwater and saltwater bodies. Seawater intrusion can cause soil salinity because it contains a high concentration of salts.
- Poor drainage: Poor drainage can occur when the soil is compacted, when there is a lot of clay in the soil, or when there is a lot of organic matter in the soil. When the soil is poorly drained, water cannot flow through the soil easily. This can cause water to pool on the surface of the soil, which can lead to soil salinity.
- Excessive fertilization: When fertilizer is applied to soil, it can help plants grow. However, if too much fertilizer is applied, it can cause the soil to become too salty. This is because fertilizer contains salts, and when too much fertilizer is applied, the salts can build up in the soil.