Timing key to turfgrass nutrient management

Successful turfgrass nutrient management depends on application timing and fertilizer rates, whether it’s a home lawn, athletic field, golf course or commercial landscape site.

Amount of fertilizer, especially nitrogen but phosphorus and potassium as well, depends to some extent on the site—soil type, turfgrass type, and use—says James McAfee, associate professor and turfgrass specialist, Texas AgriLife Extension at the Dallas Center.

Athletic fields and golf courses, for instance, typically need more fertilizer than a home lawn. For aesthetic reasons, a commercial landscape may require more fertilization than a home lawn.

McAfee says fall is a crucial time for turf fertility in warm-season grasses. “In the fall, grasses are storing food for winter,” he says. “In spring and summer, nutrients go to leaf growth.”

Fall fertility recommendation for bermuda, zoysia, and buffalo grasses in home lawns is 1pound of nitrogen for every 1,000 square feet of turf. For centipede and St. Augustine, one-half to three-fourths pound per 1,000 square feet should be adequate.”

He says areas that have been fertilized throughout the summer may need less.

Yearly application rates would be 2 to 4 pounds per 1,000 square feet for common bermudagrass, McAfee says. Typically, application would be 1 pound in the spring and 1 pound in the fall. For higher quality turf, home owners or turf managers might make several 1-pound applications per year.

Hybrid bermudagrass requires a bit more nitrogen, 3 to 5 pounds per 1,000 square feet per year. Annual rate for St. Augustine would be 2 to 4 pounds in sunny areas, 1 to 2 pounds in shade. For zoysia, 2 to 4 pounds annually for 1,000 square feet should be adequate.

Centipede annual fertility recommendation is 1 to 3 pounds. Buffalo grass nutrient needs are 1 to 2 pounds.

McAfee recommends splitting the total amount into two applications, one in spring and one in fall. “We try to keep it simple for homeowners,” he says. “But with higher maintenance hybrid grasses, managers or homeowners might consider early spring, late spring, maybe midsummer and early and late fall applications.”

He also recommends a source with 30 percent to 50 percent slow release nitrogen. “Most people over fertilize,” he explains. “A slow release product prevents too much soluble nitrogen being available and promoting too much top growth.”

Other nutrients may be important as well, depending on the site and soil analyses. “We recommended a 3-1-2 or a 4-1-2 ratio for years, but a lot of Texas soils are heavy clay and many are high in phosphorus and potassium. In some cases, that means managers are okay with straight nitrogen.”

But if soil tests show a deficiency, he recommends a fertilizer with the proper nutrient ratio. “See what the soil needs,” he says. “If we don’t know what it needs, we recommend putting a balanced fertilizer on until we get an analysis.”

He says the other nutrients will do little if any harm in a 4-1-2 ratio, although these products may be more difficult to find. “We need to work with fertilizer suppliers so they will have some of these ratios available.”

McAfee says some East and Southeast Texas soils are sandier and may be low in potassium. “Turf will need potassium in these areas. A 2-0-1 or a 2-1-1 may be needed.”

He says misinformation about higher analysis fertilizers also may confuse some homeowners. “Some reports indicate that something like a 45 percent nitrogen analysis will burn the grass,” he says. “That’s not so. It’s the amount applied, not the analysis that makes a difference. With a higher analysis, we just need to apply less.”

McAfee says homeowners need to pay attention to how much fertilizer they need. The first step is to measure the area. “A lot have no clue how many square feet they have to fertilize,” he says.

“Golf and sports field managers typically have a better idea of how much area they have to treat.”

Those high-use turf sites also need a bit more attention to fertility. “We typically increase recommended fertilization rates for sports fields and some areas of a golf course,” McAfee says. “We would probably increase nitrogen fertility on a native soil sports field by one and a half what we would recommend for a home lawn. On sand-based fields, we’d increase rates even more.”

He said fertility rates for golf course tee boxes and greens would be even higher. Fairway fertilization would be about the same as for a home lawn. Roughs would require less fertility.

Fertilization timing for golf courses and sports facilities may depend on season as well as schedule of events. Recovery following heavy use may require more maintenance.

He says a recent fall rainy season over much of Texas prevented timely fertilizer application for a lot of golf courses and parks. “Managers could not get equipment into the fields,” he says.

He says a lot of turf managers start fertility too early in the spring. “We want to wait until the grass begins to green up to fertilize. There is no reason to fertilize dormant grass.”

One exception to that would be commercial landscape/lawncare companies that have to start in February to get to all customers on time.

“It’s simply a time factor,” McAfee says. “They may put only a half-pound of nitrogen down early so it will be available when the grass breaks dormancy. But for those who do it themselves it’s best to wait.”

McAfee says stressed turf—golf course greens, tees, and sports fields—may need more potassium than lawns and commercial landscapes. “Turfgrass needs an adequate amount of potassium for drought and stress tolerance.”

He recommends both a soil test and tissue analysis to evaluate potassium needs on high-use turf areas. “We need to make certain potassium is available and getting to the plant. A lot of golf course superintendents are using both soil tests and tissue analyses.”

He says with sand-based athletic fields, potassium is the most difficult nutrient to keep in balance.

McAfee says fertilizer application timing is crucial for sports field fertility and spring and fall are the critical application windows. “We don’t want to force a lot of growth in the summer. Also, during hot, dry weather, don’t push grasses, especially St. Augustine and centipede.”

And he recommends adequate water following fertilizer application. “For nutrients to work they have to get into the soil solution so they can be taken up by the root system. That takes water.”

He recommends that homeowners and turf managers look at more than the price on a bag of fertilizer when selecting a product. Cheaper products, he says, may have more prills and dust. “You get what you pay for.”

TAGS: Management
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