Everything You Need to Know About Lawn Fertilizer

Learn the most sustainable methods for fertilizing your yard.

Warning: Chemical application in progress' sign in a lawn
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Fertilizer is defined as anything that increases the fertility of the soil. For a lawn, there are many ways to increase the soil's fertility to help your grass thrive — but some ways are far more environmentally sustainable than others. How you achieve a great lawn depends on the trade-offs you're willing to make between a beautiful lawn and environmental sustainability.

The Rise of Lawns

Lawns are a recent invention in history. Tour the cities of Europe or neighborhoods in America's oldest cities, and you'll find the front doors of houses opening directly onto the sidewalk. Back lots were for disposing of refuse — not a place where you'd want to play croquet or host a barbecue. Beyond the city lived farmers who would not waste open land that might otherwise grow crops. Grass was for livestock, and livestock mowed the lawn. 

By the second half of the 19th century, however, suburbs began to appear after trains (and later, automobiles) made travel to and from urban areas a daily occurrence. Detached housing surrounded by gardens and ornamental lawns “became the mark of suburban respectability.” The lawn mower, first patented in 1830, became a commercial success in the 1860s. The first gas-powered lawn mowers in the United States went on the market in 1914.

Consequences

Grass is the most irrigated crop in the United States. According to the Environmental Protection Agency (EPA), landscape irrigation consumes an estimated nine billion gallons of water per day. The EPA also estimates that gas-powered lawn and garden equipment emits 242 million tons of pollutants each year — approximately 4% of greenhouse gas emissions. In response, the need to reduce our carbon footprint and use of natural resources has given rise to the “No-Mow” movement — the belief that the most sustainable lawn is no lawn at all.

Reducing the size of your lawn or replacing it with a perennial or vegetable garden is not only more environmentally friendly; it can be cost-effective, as well. However, if you want to keep your lawn and keep it green, or if your homeowner's association requires the upkeep of a lawn, you can do so in ways that are more sustainable than others.

Chemical Fertilizer

Since the middle of the 20th century, petroleum-based fertilizers have become commonplace. The manufacture of chemical lawn fertilizers is highly energy intensive, emitting significant amounts of carbon dioxide and methane in the process. The over-use of chemical fertilizers has led to runoff into watersheds and waterways, damaging ecosystems by depleting oxygen levels and leading to algal blooms, which can be harmful to plants and animals alike. Even applied correctly, nitrogen-based fertilizers convert to nitrous oxide, which is 310 times a more powerful greenhouse gas than carbon dioxide.

Organic Fertilizer

Made of biological material rather than simpler chemical compounds, organic fertilizers need to be broken down by microorganisms in order to be made available to plants. The main benefit of organic fertilizers is that they work slowly, which means less runoff of excess nutrients into waterways. Organic matter also improves the structure of the soil, increases water retention, and promotes the diversity of life underneath your feet.

The best organic fertilizer may already be growing in your yard. During spring and summer, leave your grass clippings where they fall. Let them act as a mulch and they will supply about a quarter of all the nutrients your grass will need. In the fall, chop up your leaves with your lawn mower. Worms and microorganisms will return the leaves' essential nutrients to the soil. 

Pet Safety

Many fertilizers contain additives like organophosphates or pesticides that can be harmful to pets. Don't assume that store-bought organic fertilizers are safer than chemical fertilizers; they often contain bone meal or blood meal (leftovers from meatpacking plants) that can cause gastrointestinal problems in dogs.

Sustainable Lawn Maintenance Tips

Property Exterior
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If you do need to supplement your soil with store-bought fertilizers, here are some other tips for reducing the environmental impact of your lawn.

  • Apply fertilizers once or twice a year. Fertilize once in late spring for warm-season grass, once in the fall for cool-season grass. Any more than that and you are sending pennies down the driveway — and into our waterways.
  • Skip the weed killer. The best way to keep away unwelcome plants (“weeds”) is to create a thriving lawn. Grasses create a thick mat that makes it hard for competitors to grow. Over-seed your lawn with grass seed, water it in (responsibly), and your grass will act as its own weed suppressant.
  • One species' weed is another species' food. Look at dandelions from a bee's perspective: Dandelions are part of a bee's breakfast, among the first flowers to bloom in areas where winter sends most plants (and bees) into dormancy. 
  • Grow the grass that suits your soil. If your soil is rich in nutrients, you may not need to add any fertilizers at all. Have your soil tested for its mineral content at the cooperative extension at your state university. A simple pH test, available at garden centers, can also tell you what grass will do best in your soil. Fescues, Kentucky bluegrass, ryegrass, and other cool-season grasses prefer alkaline (or “sweet”) soil. Centipede, carpet, bahia, and bermuda grasses prefer acidic soils.
  • Grow easy grass. The less mowing, the better on your environment and the better on your back. Some low-maintenance grasses include Kentucky bluegrass, tall fescue, fine fescue, bahiagrass, zoysia, fleur de lawn (a mix of grasses and low-growing plants), and UC Verde buffalograss.
  • Mow less, mow higher. Let your grass grow to at least a three-inch height and you'll reduce the mount of gasoline you'll burn, help cool the soil to avoid scorching your lawn, and allow your grass to out-compete competitors like crabgrass.
  • Water less. Over-watering “spoils” grass, discouraging it from growing deeper roots, which leaves it more susceptible to scorching during droughts.
  • Use a rain barrel and drip irrigation. Attach a low-pressure soaker hose to a 40-60 gallon rain barrel to slowly water your lawn rather than blasting it with water from a sprinkler. If you live in a colder climate, be sure to drain your rain barrel after the growing season so that the barrel doesn't freeze and crack in the winter.
  • Get a battery-powered mower or a push mower. The only carbon dioxide emitted when using a push mower is the exhaling you'll do while getting a good workout mowing your lawn. While a battery-powered mower uses electricity that may come from fossil-fuel sources, electricity is always cleaner than directly burning gasoline. Unlike lawn mower manufacturers, power companies have every incentive to get every ounce of electricity out of the fossil fuels they burn. 
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