The deficient fertilizers like nitrogen and phosphorus are added to the soil to increase the yield of crops. But sometimes these fertilizers get washed off due to irrigation and other human practices through a phenomenon called fertilizer runoff.
The runoff damages the environment by increasing the amount of these fertilizers in water bodies like watersheds, lakes and rivers. This increases the concentration of the fertilizers in the water bodies called eutrophication. This eutrophication is lower down the concentration of the oxygen in the water.
