Fertilizer Phosphorus – On the Way Out
In the fall of 1989, I moved into my first home in Castle Rock. It had sat vacant for the entire summer as a HUD home. The sprinklers were turned off and nobody fertilized or cared for the lawn. The lawn was a barren wasteland the following spring. I did everything to nurture the few grass shoots that survived. I even washed my car on the front lawn to maximize the use of the water. A few days after washing my car the grass noticeably began to grow and start filling in.
What caused this accelerated growth? Two things possibly.
First, back in the days, many cleaning products and detergents contained phosphates, including Spic and Span, which I used to wash my car. Phosphorus is important for photosynthetic properties as well as stimulating root growth in plants. I attributed the improvement of my lawn to the abundance of phosphates in this cleaning product. I routinely added Spic and Span to my hose sprayer and applied it to my lawn that season as part of my fertilizing program. It not only stimulated the grass roots to grow well, I had the cleanest lawn on the block too.
Furthermore, another important property of detergents is they act as a wetting agent. Wetting agents allow water to infiltrate the soil better through reducing surface tension between the soil particles and water. When watering is restricted, wetting agents improve the soil’s ability to let the water through to the root zone and cuts down on runoff. Organic products containing wetting agents can be bought at most garden centers.
So, should you run out and buy cleaning products to spray all over your lawn? No. Most cleaning products and detergents are now phosphate-free. Stick with products designed for lawns. However, have you noticed that fertilizer manufactures are removing phosphates from their fertilizers as well?
The second number listed on a bag of fertilizer is the percentage of phosphorus in the product. Soon, I’ve been told, most fertilizers will be phosphorus-free because the EPA is attempting to cut down on phosphates entering our waterways. Phosphorus in our bodies of water encourages algal blooms, which quickly die and begin to decay, using up the dissolved oxygen in the water, which leads to the death of most aquatic life. Fertilizers designed to be applied to start new lawns still contain phosphorus to help new grass shoots get off to a good start. Established yards usually have enough phosphorus present for grass to use. Some research indicates that adding phosphorus with every fertilizer application isn’t necessary.
Phosphorus is returned to the soil by the decaying plants and organisms that once lived in the lawn. If grass is constantly bagged and removed however, the soil loses phosphate. Mulching your grass clippings returns phosphates to your lawn. Adding organic matter such as composted manure through top-dressing adds phosphate and microorganisms that will make phosphate in the soil available to the grass roots. Using organic fertilizers is a wise alternative to synthetic products and will continue to improve the soil food web and provide phosphate to your lawn in a more natural way.