When buying fertilizer, pay attention to the label. Bags of fertilizer are identified with three numbers, for example “10-20-20.” The first number stands for the amount of nitrogen (N), the second the amount of phosphorus (P), and the third for the level of potassium (K). All three are essential for healthy plant growth.
Phosphorus, the middle number, promotes root growth, blooming and fruit production. But too much phosphorus is a concern, especially near waterways, since the runoff into streams and systems like the Mid-Atlantic Chesapeake Bay promote algae growth that complicates the life for fish and shellfish.
Too Much Phosphorus
Almost 40 years ago, excess phosphorus in lakes and rivers prompted the ban on phosphates in laundry detergents. Since most people didn’t fertilize lawns in until prompted by the growth of housing development and neighborhood association practices in the last quarter of the 20th century, phosphorus in lawn fertilizers wasn’t a concern because most people didn’t fertilize their lawns. The marketing of lawn care products and growth of lawn care companies in the last couple of decades has generated an explosion in the use of turf fertilizers to aid in the growth of lush green lawns.
What Too Much Phosphorus Does to Water
Plants don’t absorb more phosphorus than they can use, so the runoff ends up running off to nearby waterways. Phosphorus that enters streams, creeks, lakes, and rivers and promotes excessive algae and weed growth. When these plants die, they float to the bottom. In the process of decomposition, they use oxygen. The amount of oxygen available for fish and other marine organisms is diminished. As their numbers are reduced, water quality worsens.
Waste water treatment plants, animal waste and fertilizer runoff from farms all contribute phosphorus. In fast-growing areas like the Virginia-Maryland Chesapeake Bay region, lawn fertilizers are blamed for as much as half of the phosphorus pollution.
Don’t “P” On Your Lawn
A new campaign called “Don’t ‘P’ on Your Lawn,” encourages the use of ‘Phosphorus’-free fertilizers. Several states have already banned the use of phosphorus in lawn fertilizer.
Fertilize Responsibly
Start with a soil test, available from local extension agent in some states, to make sure your lawn needs to be fed and to find out what nutrients you need to apply. Get recommendations on the specific rates and never apply more than is recommended. If soil has adequate phosphorus levels, ‘P’-free fertilizer is easy to find: look for a fertilizer with a zero as the middle number.
Apply fertilizer correctly. Drop spreaders are more precise than rotary spreaders. Don’t get fertilizer on hard surface areas like driveways, and avoid fertilizing natural drainage areas where runoff could be a problem. Never wash excess fertilizer into the street where it could enter a storm drain.
In the alternative, consider giving up the fertilizer habit and by a mulching lawnmower. Grass and leaf mulch fertilize your lawn naturally.
Sara E. Lewis - Sara E. Lewis is a writer and publications consultant. As a freelancer, she writes and produces marketing materials and especially enjoys ...
