Answer:
Water pollution.
Step-by-step explanation:
If the water bodies get contaminated with unwanted substances then such type of contamination is known to cause water pollution.
In the given situation, it is mentioned that the farmer has applied excess of fertilizer on the field just before the rainstorm. As a result of this, the excess fertilizer along with the rainwater will be carried into the water bodies as well as would seep into the ground water and cause water pollution.