Feeding the Lawn - Without Killing Off the Birds, Dogs,
Cats, Kids, Lizards, Raccoons, Chickens, Squirrels, Praying Mantis, Frogs, Earthworms, Butterflies, Fishes and the Deep Blue Sea . . .

For many people, keeping the lawn looking nice is the most important outdoor chore they have. Weekends are spent mowing, edging, watering and fertilizing. In the past few years there has been more emphasis on designing gardens with less high-maintenance grass and more native grass, ground cover, and other material that requires less effort. Still, having a nice lawn is desirable and city-dwellers in particular are interested in having healthy, beautiful grass while at the same time using fewer chemicals, less water, and exerting less effort.

The City of Austin Grow Green program recently commissioned a study that was conducted by Texas A&M. The questions of the study centered around how lawn fertilizers impact the quality of water in the area. Because there is growing recognition that we have a limited supply of fresh water and the demands on that water are increasing rapidly, the City of Austin wanted to know how best to maintain water quality in environmentally-sensitive recharge zones.

High nitrates, which often result from use of fertilizer, can cause algae blooms which deplete the water of oxygen and can lead to fish kills and other risks to aquatic life.

The study involved soil tests and greenhouse studies assessing the levels of nitrogen, phosphorous and potassium that leached from the lawn into the groundwater. The lawns were also judged on the basis of their appearance.

The findings resulted in dramatic changes to both the quantity and types of fertilizer recommended. In the past, the Extension Service and the City recommended high-nitrogen fertilizers applied at a fairly heavy rate several times a year. They made no distinction between organic and chemical fertilizers.

A big surprise to the people who did the study (and no surprise to us!) was that certified organic and other natural fertilizers out-performed inorganics in the study. There was substantially less nitrogen leaching to groundwater in the organically-fertilized test plots. Also, after a slightly slower start, the grass was denser and more attractive in the organically fertilized lawns than in those treated with inorganic fertilizer. The study also tested inorganic urea-coated, slow-release fertilizers and found that these fertilizers did not, in fact, release nutrients slowly. Apparently in our warm weather, the inorganic urea-coated fertilizers just dump their nutrients on application, where most of them are washed away. These types of fertilizers had no advantage over other inorganic types although they are often touted as environmentally sensitive.

Tony Provin, the A&M soil scientists leading the study, originally expected the synthetic fertilizers to look better than the organic but described a "180 degree change" in his opinion. The organic treatments fared better across the board on color and density. They also proved to retain soil moisture and decrease runoff during heavy rainfall.

The test involved several different brands of organic and inorganic lawn fertilizer. Across the board, the organics, regardless of brand, proved the better choice.

The study also showed that in general people were fertilizing too often and using too much fertilizer. While in the past the recommendation was to add 1 lb of nitrogen per 1,000 square feet three to five times a year, the new recommendations are much lower. It is recommended that you fertilize only once a year or perhaps twice if a soil test shows that your soil is very low in nitrogen. The Grow Green Program suggests that everyone have a soil test before beginning a fertilization program. Soils high in nitrogen do not need fertilizing at all, and soils high in phosphorous and potassium should be fertilized with products showing low second and third numbers - 9-1-1 or 6-1-1, for example.

Another important recommendation for keeping a healthy and beautiful lawn is - Don't Bag It! Leave clippings on the lawn. This practice results in at least 60% of the clippings' nitrogen and 100% of the phosphorous and potassium being available to the grass within the growing season. Iron and other micronutrients are also returned to the soil, and it is protected from sunburn.

Don't fertilize before a rain. Although it seems like a good idea to soak the fertilizer into the soil, too often the rain can become heavy and simply wash the fertilizer away. The result is that the creeks are fertilized and your lawn is not - not a good thing.

These new recommendations can reduce fertilizer use by at least 75% and increase the efficiency of the fertilizer used. They also will keep the water cleaner, the soil more active and fertile, and help your battered pocketbook.

    • Test your soil (see Classifieds for a good soil test).
    • Don't Bag It! Think of mowing as fertilizing.
    • Choose organic fertilizer.
    • Use less fertilizer.
    • Fertilize only once a year (twice at most).
    • Keep fertilizer out of the drainage system by watching for rain, runoff, and        excessive watering.
    • Feel free to go barefoot!