Lawns and gardens need to be fertilized because most soils do not provide the essential nutrients required for optimum growth. Even if you are lucky enough to start with great soil, as your plants grow, they absorb nutrients and leave the soil less fertile.
By fertilizing your lawn and garden, you replenish lost nutrients and ensure that this year's plants have the food they need to flourish.
There are six primary nutrients that plants require. Plants get the first three—carbon, hydrogen and oxygen—from air and water. The other three are nitrogen, phosphorus and potassium.
Using this chart, you can determine the percentages of these nutrients in a fertilizer. A 5-2-0 fertilizer like Milorganite is 5% Nitrogen, 2% Phosphorus and 0% Potassium.
Fertilizers come from many sources. Synthetic fertilizers are manufactured from minerals, gasses from the air, and waste materials. Organic fertilizers obtain their nutrients from natural organic sources such as microbes, organic wastes, and other similar materials. Learn more about the differences between organic and synthetic fertilizers.