If this were a normal Minnesota April, we would just now be emerging from winter hibernation, still living in fear of one last spring snowstorm. This year, however, we may as well be in South Carolina. To look at our lawns, you would think it was June, and most people in my neighborhood have already mowed at least once. When it comes to lawns, most people fall into one of two categories. There are the folks who spend beaucoup bucks and countless hours in their quest for a lush, green and weed-free lawn. Then there are the folks who mostly ignore their lawns, mowing just often enough to keep the weed inspector at bay. While each set of people think they are doing the right thing, we might want to consider a Goldilocks approach.
Turfgrass is the largest irrigated crop in the United States, covering about 49,000 square miles of land. If you put all of these lawns, golf courses and sports fields side by side, they would cover more than half of the state of Minnesota. For this reason, lawns have a bigger impact than you might think on the health of our local lakes and rivers, bird, fish and insect populations, and even our own families and pets. At the same time, maintaining a healthy lawn with attractive landscaping is a surefire way to increase your property value, whereas letting your lawn go to pot will quickly turn your neighbors into enemies.
New research from the Minnesota Pollution Control Agency (MPCA) indicates that good-looking lawns are often better for water quality, which may come as surprise to those of us who thought that we were doing our part by growing a chemical and fertilizer-free lawn. While a toxic mixture of herbicides, insecticides and artificial fertilizers, combined with a daily dose of irrigation, can mean bad news for both our lawns and our local lakes, it turns out that a no-care approach to lawn care can generate quite a bit of water pollution too.
In their study, the MPCA tested four plots of turf grass over the course of five years. Their goal was to determine what kind of impact Minnesota’s phosphorus fertilizer ban, passed in 2005, might have on local lawns and lakes. The law was designed to reduce the amount of phosphorus that runs off of lawns during rain, snow melt and lawn-watering and keep this phosphorus out of our waterways where it can cause algal blooms and aquatic weed growth. MPCA researchers found that in the second year of the study, runoff from the lawn grass given no fertilizer actually generated the most phosphorus, and that in subsequent years it created as much phosphorus runoff as the lawns treated with phosphorus fertilizer. A plot given fertilizer with nitrogen and potassium, but no phosphorus, had the best looking grass and the least runoff. Their conclusion? By applying fertilizer with nitrogen and potassium (but no phosphorus) people can grow lawns that are dense and healthy, have deeper roots, and allow less runoff from rain and melting snow.
Over the five years of the turf management study, researchers made another shocking discovery. A full 86% of the phosphorus came from runoff in the winter when the ground was frozen. In fact, 81% of the phosphorus that ran off of the turf plots during 2007 ran off during a single rainy winter day while the soil was frozen! As a result, they recommend that people apply fertilizer only once during the year, and preferably early in the fall so that it has plenty of time to be absorbed before the ground freezes.
Conducting a soil test every three to four years is the best way to determine if your lawn needs additional fertilizer. In addition, there are a few simple ways to keep your lawn looking tidy without poisoning your dog or the fish in your neighborhood pond. Dense healthy grass is a much better weapon against dandelions and other weeds than a chemical herbicide. Mowing your lawn regularly so that you never remove more than 1/3 of the grass’s leaf surface and letting the grass stand about three inches tall are two ways to encourage deeper roots and healthier grass. When you do mow, be sure to turn the mower around as you pass by the street so that grass clippings are blown back into the lawn. The nutrient-rich clippings will help your lawn to grow, instead of washing into the storm drain and greening a local lake.
Wise watering can also help to conserve groundwater resources and maintain healthier grass. If you water too frequently, your grass eventually gets lazy and stops growing deep roots. A better strategy is give your lawn one inch of water per week during the dry summer months and let rain do the job for you during the rest of the year.
To learn more about caring for your lawn, as well as tips for maintaining gardens and other types of landscaping, email firstname.lastname@example.org to request a free copy of the Blue Thumb Year-Round Guide to Yard Care.