Home & Garden: Nitrogen is necessary for lawn health in Colorado’s Grand Valley
Free Press Gardening Columnist
One would expect the rains we have had would make our lawns lush and healthy. While that is true when rains are accompanied with a lot of lighting, our lawns are currently fairly thin and weak. Nitrogen is the key to a thick lawn. Unless you have had your lawn cared for by professionals, it is most likely lacking adequate nitrogen.
Another way you can tell your lawn is in need of nitrogen is the presence of clover. Nitrogen, a major component of the chlorophyll responsible for a lawn’s green color, is necessary for vegetative growth, root depth and root mass. Without adequate nitrogen our lawns are thin and more open to invasion by weedy plants like clover.
Nitrogen and oxygen make up the majority of the air we breathe (78 percent and 21 percent respectively), but this nitrogen is not in a form plants can use. Lighting breaks nitrogen molecules apart and enables these atoms to combine with oxygen, creating a puff of nitrogen oxides that dissolve in the rain and are carried to earth. This NOx is further converted into plant-available nitrate nitrogen by soil bacteria. The amount of NOx created in part by lightning has not been enough to keep our lawns thick and lush. The nitrate resulting from lighting was most likely washed by the rain below the root zone of our lawns.
Our lawns need nitrogen whether applied in an organic or inorganic form. Our plants don’t know the difference. The amount of nitrogen applied needs to be based on the growth stage of the turf and weather conditions. Now that our hot season is beginning, we need to fertilize our lawns with less than we use during cool weather.
Most of the local lawns are cool-season grasses such as Kentucky bluegrass, tall fescue, and perennial ryegrass. These grasses tend to shut down during the heat to reduce stress. Fertilizing with the normal one pound of Nitrogen per thousand square feet, which is the amount lawn fertilizers recommend, results in additional stress of cool-season grasses. Stress results in loss of roots and more susceptibility to disease, insect, and weed problems. Setting your fertilizer spreader to apply only one-half the rate recommended on the fertilizer’s label is recommended during the hot summer months. Several small applications spaced four to six weeks apart is much better than one large application. Later in the fall, especially after the last mowing of the season, doubling the rate of nitrogen is recommended.
If your lawn is a warm-season grass such as buffalo, Bermuda, or zoysiagrass, these grasses need most of their nitrogen in the hot summer months and not in the late fall when temperature are cool.
Free Press columnist Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866 or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.
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