Mulch to Build Topsoil
Spread a thin layer of organic material such as chopped leaves or Canadian spaghnum peat moss on your lawn every year or two to add organic matter to the soil in which your grass grows. This mulching routine is one of those “extra” things that pays big dividends. It builds healthy soil by improving its structure and ability to retain water.
Organic mulches also add billions of beneficial disease-fighting fungi to your lawn’s soil. These friendly microbes effectively control many common lawn diseases, such as dollar spot, brown patch, and Pythium blight. There are also some naturally occurring substances in organic mulching materials that suppress disease organisms.
Mulching reinforces the natural defense system that is already in place in a healthy lawn. A truly healthy soil is composed of 3% to 5% organic matter. By maintaining this level you provide optimum growing conditions for your grass. The result? Less plant stress and fewer problems with weeds, diseases, and pests.
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The way you water the lawn contributes to the control of fungal disease:
Water deeply and infrequently to encourage deep root growth. Light daily sprinkling encourages grass roots to linger near the soil surface to obtain moisture. Here they collect and dry out, gradually building a matted layer of thatch which fosters fungal disease.
Water in the morning—grass plants start the day with moisture, yet have time to dry off before nightfall to avoid encouraging fungal disease.
Water only when the lawn needs it. Constantly moist grass is susceptible to disease. Thirsty grass shows a drab bluish tinge or fails to rebound quickly when you walk on it.
Water so that the soil is moist down 6 to 8 inches. To reach this depth deliver a half inch of water to sandy soil, 1 inch to loam soil and 1½ inches to clay soil. Adjust your watering time to your soil type.
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Regardless of how healthy their soil is, turfgrasses still need additional nutrients from fertilizer over the growing season. However, too much or too little may trigger various fungal diseases.
Choose a slow acting granular lawn fertilizer that offers a large percentage of nitrogen in slow-acting or water insoluble (WIN) form to deliver nitrogen to grass plants slowly and consistently over several weeks.
Carefully follow product label directions for amounts to use.
Avoid fertilizers that are combined with herbicides or insecticides; address weed and insect pest problems separately.
Correct mowing reduces stress on grass and improves its disease resistance:
Mow lightly and frequently. Studies show that this stresses grass plants less than heavy, infrequent cuttings.
Cut no more than 1/3 of the grass blade at any one time. Otherwise the grass loses too much of its energy-storing foliage and has to rapidly replace it while shortchanging root development.
Mow tall. Grass maintained at 2½ to 3 inches grows deeper roots so it has more staying power during drought. Tall grass also helps shade the soil, cooling the crowns of the grass plants and reducing soil drying.
Mow dry. Damp grass causes uneven mowing and messy clumps of clippings which may mat, block sunlight and promote fungal growth. If there is some fungal disease in parts of the lawn it will be tracked over the whole lawn.
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Aerate to Relieve Soil Compaction
Grass roots growing in compacted soil are forced to stay near the surface which stunts and stresses the plants. They are more vulnerable to fungal infection. The most direct way to reduce soil compaction is to admit air into the soil. To break up compacted soil and introduce air into it, rent a power-driven lawn core aerator or buy a hand lawn aerator tool. These tools remove plugs of turf and deposit them on the grass, leaving holes that admit air down 3 or 4 inches into the soil.
Aeration, alone or in combination with topdressing, provides organic matter, revitalizing the soil organisms that make soil fertile. If the soil under your turfgrass is very compacted, aerate at least once a year for 2 or 3 years to restore the soil. If you routinely topdress, eventually aerating will be necessary only every 4 or 5 years to maintain fertile lawn soil.
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Thatch develops naturally in lawns over time. When this ruglike mass of surface roots and accumulated dead plant parts builds up on the soil surface at the base of grass plants to over ¼ inch thick it fosters problems. Thatch harbors diseases such as Fusarium blight, dollar spot, brown patch, snow mold, and necrotic ring spot. It also intercepts moisture that would otherwise go down into the soil and the root zone, and it inhibits grass root development.
Causes of thatch include compacted soil, in which the thatch layer may be ½ inch or more thick, and overuse of quick-acting nitrogen fertilizers, which tend to acidify the soil making it less hospitable to earthworms and other beneficial decomposer organisms. Ironically, thatch buildup can also occur in a perfectly healthy, densely planted turf. Remove excessive thatch with a dethatching rake or a motorized dethatching machine to reduce problems with fungal diseases.
Plant Disease-Resistant Grasses
Most popular lawn grasses have been bred to resist fungus diseases. In order to get the benefit of this feature be sure to buy premium grade mixtures or blends of grass seed to assure that you are getting the most recent technology in turfgrass breeding.
These resistant grasses can be overseeded into existing turf or spread on newly prepared ground.
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