Over-cultivation, unrestricted grazing and deforestation results in all of the following except:

Increase in soil salinity

The correct answer is Option (3) → Increase in soil salinity 

Over-cultivation, unrestricted grazing, and deforestation lead primarily to soil erosion, desertification, and leaching. These activities degrade the land, reduce vegetation cover, and deplete soil nutrients, leading to the loss of fertile topsoil and contributing to desert-like conditions (desertification). Leaching, or the washing away of nutrients from the soil, also occurs as soil structure deteriorates.

Soil salinity, however, is typically caused by irrigation practices that leave salts behind as water evaporates, not directly by over-cultivation, grazing, or deforestation. Irrigation without proper drainage of water leads to waterlogging in the soil. Besides affecting the crops, waterlogging draws salt to the surface of the soil. The salt then is deposited as a thin crust on the land surface or starts collecting at the roots of the plants. This increased salt content is inimical to the growth of crops and is extremely damaging to agriculture. Therefore, increase in soil salinity is not a direct result of these practices.