What is fertilizer?
Fertilizer is a word that most everyone knows, but what it is and what does it do?
Fertilizer is basically food for plants in a readily available form. Plants, just like humans, need a variety nutrients to grow and thrive. While humans get nutrients from the different foods (meat, vegetables, fruits, dairy, grains) they eat, plants obtain most of the nutrients they need from the soil. Many times the different types of soil don’t have the nutrients necessary for the plant to grow and thrive or the nutrients are bound to the soil in a form that makes it difficult for the plant to use. That’s where fertilizer comes in.
Fertilizer is used to supply plants with the nutrients they need, primarily nitrogen, phosphorus, and potassium, in a form that is easy to uptake and use by the plants roots. It is typically added to the soil when a newly planted seed or young plant is started to help the plant become established. Fertilizer can or may be added to the soil throughout the life of the plant to help keep it healthy and growing strong. But over-fertilizing can be a bad thing. Too much fertilizer can actually kill the plant and excess fertilizer can run-off into streams and lakes causing toxic algal blooms that are harmful to aquatic life.
It's Not Just Lawn Fertilizer
When fertilizer is applied to our lawns, nutrients are being added – something that all plants need to survive and grow. What isn’t always considered, though, is that the soil below may already have sufficient levels of these nutrients. Brand-new lawns or areas with very poor soils might be lacking in nutrients, but most established lawns do not lack these nutrients. When healthy, well-established lawns are fertilized anyway, the nutrients (mainly nitrogen and phosphorus) that aren’t used by the grass then runoff with the next rain (or lawn watering) and end up in our streams and reservoirs where they can feed algae. It takes just one (1) pound of phosphorous entering a waterway to produce 500 pounds of algae.
It’s not just lawn fertilizers that are the problem – any type of fertilizer can cause an algae bloom. Whether organic or inorganic, manure or bone meal, or applied on a lawn, an agricultural field, or a golf course, fertilizer is fertilizer and too much of it is a bad thing. Fertilizers used in agriculture are a significant source of nutrient pollution to water. In fact, nitrogen and phosphorus runoff from agricultural fields is one of the largest sources of pollution to dead zones across the United States. Perhaps the most infamous dead zone in the United States is an 8,500 square mile area (about the size of New Jersey) of the Gulf of Mexico, not far from where the nutrient-laden Mississippi River lets out. Farms throughout the Midwest drain into the Mississippi, thus causing it to be so overloaded with nutrients. The nutrient overload in the Gulf has ruined the region’s once booming shrimp industry and low oxygen levels in the water there have led to reproductive problems for fish, leading to lack of spawning and low egg counts.
Why are fertilizers so bad? Fertilizers are food for plants and as that they aren’t bad. What’s bad is misuse and over application of fertilizers. Think of it this way – too much of a good thing isn’t always a good thing. Plants don’t typically absorb nutrients they don’t need. So if more fertilizer than is needed is applied is just sits there, unused, until the next rain when it is washed into streams, rivers, lakes or reservoirs. Once the nutrients from the fertilizer reach the water, that’s when the problems begin.
When too much fertilizer (nutrients) enter the water it causes a type of pollution called eutrophication. Eutrophication causes algae growth to explode. Algae typically have a very fast life cycle and when this life cycle is accelerated it causes problems for water quality and aquatic life. The fast life cycle of algae can deplete oxygen from the water. This phenomenon, known as hypoxia, results in oxygen levels becoming so low that the water can no longer support aquatic life. The end result is a dead zone. In addition to dead zones, excess nutrients in the water and the resulting algae blooms can result in the production of algal toxins and strange tastes and smells (taste and odor compounds) in the water. Remember, it takes just one (1) pound of phosphorous entering a waterway to produce 500 pounds of algae.
For more information about eutrophication, hypoxia, dead zones, and algae check out the items on the sidebar to the right.
It's More Than Just Phosphorus
You might wonder if using organic or phosphorus-free fertilizers are the solution to preventing algae blooms or other risks to the environment. While those are certainly very important considerations and decisions when selecting fertilizer for your lawn and phosphorus does have a BIG impact (always use a phosphorus-free fertilizer!), that's not the whole fertilizer story, nor the end of harmful fertilizer impacts. Allowing too much nitrogen into waterways can be just as harmful to water quality as phosphorus.
Nitrogen, like phosphorus, is typically a large component of fertilizer. Nitrogen, or nitrate, also contributes to the excessive growth of algae and other plants. Nitrate, a water soluble form of nitrogen, is the form of nitrogen normally used by plants. Concentrations of nitrate in lakes and streams greater that 5 milligrams per liter (measured as nitrogen) can cause excessive growth of algae and other plants, just as phosphorus does. This growth can lead to rapid aging or “dying off” of lakes. It can also lead to low dissolved oxygen levels that in turn makes it hard for aquatic life to survive. Exposure to high levels of nitrate is also dangerous for animals and humans even without the consideration of algae growth and oxygen impacts. If humans consume water (drinking water) with a nitrate-nitrogen concentration greater than 10 milligrams per liter it can lead to a condition called methemoglobinemia or “blue baby syndrome” in infants and other negative health impacts. The best choice you can make is to only use the type and amount of fertilizer your lawn needs – test your soil first!