Reason for arable land turning saline in irrigated zones of India:

Over irrigation:
- Over irrigation is the main reason for the salinization of arable land in the irrigated zones of India.
- When excessive water is applied to the land, it increases the water table and causes the rise of saline groundwater to the root zone of plants.
- The excessive water leaches salts from the soil surface to the root zone, leading to the accumulation of salts in the topsoil.
- This accumulation of salts in the root zone hampers the growth and productivity of crops, eventually making the land unsuitable for agriculture.

Impact of over irrigation on arable land:
- Over irrigation leads to waterlogging, which reduces the oxygen supply to the roots of plants, causing their death or reduced growth.
- The presence of excessive water also hampers the drainage capacity of the soil, leading to the accumulation of salts.
- The dissolved salts in water get deposited in the soil profile as the water evaporates, leading to the salinization of the land.
- Salinity affects the physical and chemical properties of the soil, making it less fertile.
- It also affects the osmotic potential of the soil solution, making it difficult for plants to absorb water and nutrients, thus reducing their growth and yield.
- The accumulation of salts also causes a decline in soil microbial activity, further affecting the overall soil health.

Prevention and management of salinization:
- Proper irrigation management practices can help prevent the salinization of arable land.
- Crop rotation and selection of salt-tolerant crops can help mitigate the impact of salinity.
- Adequate drainage systems should be in place to prevent waterlogging and to remove excess salts from the root zone.
- The use of gypsum can also help in reclaiming saline soils by replacing sodium ions with calcium ions, which are less harmful.
- Timely soil testing and monitoring of soil salinity levels can help in implementing appropriate measures to prevent or manage salinization.

In conclusion, over irrigation is the primary reason for the salinization of arable land in the irrigated zones of India. It leads to the accumulation of salts in the soil, affecting the growth and productivity of crops. Proper irrigation management, drainage systems, and the use of gypsum can help prevent and manage salinization.