What are two disadvantages of using fertilizers?

Answer 1

Lush growth of body parts at the expense of flowers and fruits may be one disadvantageous consequence of using fertilizers. Unavailability of other necessary nutrients may be another.

Specifically, fertilizers tend to be heavy on the major nutrients of Nitrogen, Phosphorus and Potassium. In proper amounts and over a proper amount of time, the three encourage proper overall plant health and proper growth of such plant body parts as shoots, roots, buds, and blossoms. In improper amounts, the roots and shoots may become lush and extensive while the fruits and flowers are minimal or non-existent.

Additionally, too much nitrogen in the ground exhausts the soil. It can't be used by soil food web critters and by plant roots in other than soluble form. There already is nitrogen in the soil from the nutrients in rain and from decomposing animal and plant matter. The amount of nutrients therefore may exceed the amount of water in which said nutrients may be dissolved.

The combination of too much nitrogen and an altered pH level of the soil may make other necessary nutrients unavailable. Specifically, aluminum, magnesium and manganese may be present in the soil but unavailable in such a situation.