Sustainable Landscaping and Gardening (cont)
By: Susan Littlefield
Grow a Sustainable Lawn
Conventional lawn care practices contribute an inordinate amount to the negative environmental impact of many landscapes. I've already mentioned the size of a lawn's carbon footprint, but energy use isn't the only downside. Water runoff that carries the nutrient phosphorus from lawn fertilizers reaches lakes, streams, and rivers, where it is a big contributor to algal blooms and the fish-harming depletion of oxygen they cause. Research has shown that a pound of phosphorus can fuel the growth of 300 to 500 pounds of algae in a body of water! Many lawn chemicals have also been linked to health risks to people, especially children, as well as pets and wildlife, and can pollute waterways. Irrigating lawns uses water resources that are becoming increasingly scarce in many areas.
Lawns are not all bad, of course. They, too, take up and store carbon, and allow rainwater to soak into the soil, rather than running off. And there is really no type of plant other than lawn grass that can take foot traffic and provide a spot for kids and pets to play. But in many landscapes, large swaths of lawn serve no practical purpose and might be replaced with more environmentally friendly plantings.
Where you do choose to grow a lawn, care for it sustainably. Mow the grass high to encourage deep rooting and shade out weeds. The best height depends on the kind of grass you're growing. Cut the cool-season grasses grown in the northern half of the country 3 inches high. The best mowing height for southern warm-season grasses depends on the particular grass you are growing. Check with your local Cooperative Extension Service for advice. Let the clippings remain on the lawn when you mow to recycle their nutrients back to the soil.
To make sure the fertilizer you put down helps your lawn, rather than running off to cause problems in the watershed, use one that has at least 50 percent of its nitrogen in organic or slow release (water-insoluble) form. Sweep up any fertilizer that lands on driveways and sidewalks as you spread it, and avoid fertilizing right before heavy rain is predicted.
Research has shown that, on established lawns growing on soils that did not test deficient in phosphorus, adding this potentially watershed-harmful nutrient in fertilizer did nothing to benefit the growth of the turf. So, for established lawns, test your soil every 3 to 5 years and, if the soil test does not show a phosphorus deficiency, use a fertilizer that does not include this nutrient. Look for one with a zero for the middle number in the analysis, for example 5-0-10 or 10-0-10. (That middle number indicates the percentage of phosphate in the fertilizer.) Even if the soil test shows a need for additional phosphorus, adding it in late fall does not benefit the grass and increases phosphorus in the runoff. So apply any phosphorus-containing fertilizers in spring or early fall. Phosphorus is helpful in the establishment of a new lawn the first year after sodding or seeding and does not contribute to runoff when it is applied to new lawns according to recommended rates.
Time your lawn fertilizing right to benefit your lawn the most and reduce the likelihood of polluted runoff. Cool-season grasses benefit the most from a main feeding in early fall, while warm season grasses are best given their main feeding in late spring.
Conserve water by irrigating only when needed. Water in the morning to reduce losses to evaporation and put down enough to soak the depth of the lawn's root system, but not so much that puddles form. Then wait until you see your footprints in the grass when you walk across it to rewater. This will encourage the roots of the grass plants to grow deep, and they'll be better able to withstand periods of heat and drought.