The main source of salinity in the soil is irrigation that damages the crops in the field. The water that is used for irrigation has salts and minerals in it.
When there is a over irrigation, the extra water gets evaporated due to the sunlight. The left over substance is salt. This increase in the concentration salt in crops leds to destruction of crops.
<span>The question is asking how over-irrigation is damaging to soil. Over-irrigation means that too much water is being delivered to the soil, and too much water can wash some other important ingredients out - such as organic material. Therefore, the correct answer is:
a. It reduces the amount of organic material in soil.</span>
