Agricultural fertilizer is used to help farmers keep their plants and crops healthy. Fertilizer is necessary because crops that are cut down do not die and decay like plants in the wild. In nature, the decaying plants enrich the soil and replenish the minerals and nutrients that the crops extracted from it. Scientists have found that plants need 13 different nutrients to grow. Some of these are nitrogen, phosphorus, potassium, sulfur, calcium, and boron.