Excessive Phosphorus in Soil

Sources

• Much of the excess phosphorus content in soil comes from the improper application of fertilizers. While much of this occurs on a large scale from commercial agricultural farms, it can also be further aggravated by the improper application of fertilizers in the private home. When homeowners apply too much fertilizer or apply it too often, it can be more than the grass is capable of absorbing and will result in the accumulation of phosphorus. Most organic and inorganic fertilizers contain a high amount of all three macronutrients, so the content of phosphorus is one of the main concerns of overapplication.

  Phosphorus also ends up in the soil from other sources, such as detergents and soaps, pet waste and other animal wastes. Farms and livestock holding areas are a large source of excess phosphorus.

Soil Effects

• When present in soil in the right amounts, phosphorus encourages plant growth and is used to create healthy seeds from the parent plants. When there is too much phosphorus in the soil, the results can be very different. Lawns, gardens and other plants can be burned by the presence of too high a concentration of the nutrient, turning brown and dying. A high presence of phosphorus can also make other, unwanted plants grow out of control, increasing a weed problem and encouraging the growth of undesired, invasive species that can otherwise be easily kept under control by routine maintenance.

Other Effects

• When phosphorus isn't used right away, it binds to the soil molecules. When this happens, it can easily be picked up by the wind and scattered into other areas. The same phosphorus can also be carried away by rain and runoff, and will eventually be carried to a body of water, where it will collect.

  Algae will grow as much as the phosphorus content of the water will allow, and when too much phosphorus ends up in the water it can result in the development of algal blooms. While this phenomenon happens naturally, artificially-induced blooms can stay for long periods of time, robbing the water of its oxygen and blocking out the sun. When this happens, the entire ecosystem can be disrupted.

Prevention

• At a residential level, it is vitally important to always follow the instructions when applying fertilizer to lawns and gardens. Since there is not always a need for them and some soils are naturally rich in phosphorus, conducting a soil test before even purchasing fertilizer will give a good idea on whether or not it is even needed. Local college extension offices or environmental conservation offices will have the resources to perform soils tests.

  Because some soaps -- and particularly dishwashing liquids -- have almost as much phosphorus in them as fertilizers, it is important to always dispose of these liquids properly. Do not use more than necessary for outdoor activities like washing the car, and do not use more than necessary when doing chores that generate waste water.