The correct answer is D. All of the above.
Over-irrigation can lead to waterlogging, soil salinity, and reduced crop yields.
Waterlogging occurs when the soil becomes saturated with water. This can happen when too much water is applied to the soil, or when the soil is not able to drain properly. Waterlogging can damage crops by depriving them of oxygen, and it can also lead to the growth of harmful bacteria and fungi.
Soil salinity occurs when the concentration of salt in the soil becomes too high. This can happen when water that contains salt is applied to the soil, or when salt-rich water moves up from the groundwater. Soil salinity can damage crops by making it difficult for them to absorb water and nutrients.
Reduced crop yields occur when crops are not able to produce as much food as they would if they were not over-irrigated. This can happen because of waterlogging, soil salinity, or other problems that can be caused by over-irrigation.
Over-irrigation can have a number of negative consequences, so it is important to manage irrigation carefully to avoid these problems.