PlSc 375 Turfgrass Management Dr. Ron Smith

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Grasslands make up about 1/4 of the earth's cover. Turfgrass protects the land from erosion, stabilizes the soil, moderates the temperatures, and provides low cost, safe surfacing for many sporting and leisure activities. Collectively, turfgrasses make the basis for a multibillion dollar industry.

Turfgrass culture differs from other forms of agriculture and horticulture in the deliberate creation of competition. In a one inch square, 4, 8, or 20 grass plants can be grown, depending on their mowing height. At 2", it is 4 plants, at 1" 8 plants, and ½ inch 20 plants. At ½ inch we consider a lawn a "carpet" of beauty, but at that height the Kentucky bluegrass plant is stressed, calling for additional management to control diseases, weeds, and other pests.

Two basic classes of grass exist: Cool-season and warm-season. In this breakdown, they are further divided into: Bunch-type, rhizomatous types, and stoloniferous types. In North Dakota, we can grow both cool-season and warm-season grasses. The primary types of cool-season grass species are: Kentucky bluegrass (Poa pratensis), perennial ryegrass (Lolium perenne), and fine leaf creeping red fescue (Festuca rubra). Tall fescue (Festuca arundinaceae) and creeping bentgrass (Agrostis palustris) are also considered cool-season grasses, but their use is more limited: bentgrass is mostly confined to golf course putting greens, while tall fescue is still considered a utility grass, although some cultivars are gaining popularity due to their finer texture, and ease of maintenance - like lower water requirements. In the south, warm season grasses like Bermuda, St. Augustine, centipede, and zoysia, are common grasses.

"Xeric grasses" like Buffalo grass, blue grama, crested wheatgrass, and sideoats grama are used in the water-short areas of the state, and where the soil salts may be too high to grow other turfgrasses. In extremely salty conditions, creeping alkali grass would have to be used.

Turfgrass may be established by seed, plugs, and by sodding. Properly laid sod provides an "instant lawn" while seeding has the lowest initial cost, but takes longest to establish. Sodded lawns and athletic fields are seldom sown with just one species of grass. They usually are mixtures, which means two or more species are used, like Kentucky bluegrass and perennial ryegrass. In high-quality, high maintenance lawns, a blend may be used. This is where 2 or more of the same species are used in seeding, like ‘Rambo and ‘Limousine' Kentucky bluegrass. These two grasses by the way, are popular in golf course fairways because of their tolerance to close mowing.

Problems in turfgrass management: weeds - crabgrass, quackgrass, chickweed, dandelions, broadleaf plantain, creeping Charlie; insects - sod webworm, scarab beetles, chinch bugs; diseases - snow molds, summer patch syndrome, and rust. Weeds cause the biggest visual problem with homeowners and turf managers alike. Annual weeds (like crabgrass) can be controlled with pre-emergent herbicides like Pendimethalin when applied in early spring; broadleaf perennial weeds like dandelions are best controlled in the fall with a post-emergent herbicide like Trimec. A curse weed for golf course superintendents is annual bluegrass (Poa annua). It competes with bentgrass by growing when the bent is weakest - in the early spring and fall - then goes to seed and dies out in between. It has the ability to form seed heads even when mowed at 3.2 mm (1/8" or 0.125") thus disrupting putting.

Seeding rates differ, due to seed size differences: for example, Kentucky bluegrass has an average of 2.2 million seeds per pound, and is spread at a rate of 1-1.5 lb/1000 sf, while perennial ryegrass has 0.23 million seeds per pound and is sown at 2-6 lb/1000 sf. Germination times differ as well, with perennial ryegrass emerging in 5-7 days, while Kentucky bluegrass can take 21 or more days. When buying seed, check two figures: % germination and purity. The higher the better. For example, if Kentucky bluegrass has a germination rate of 88% and a purity of 92%, then the PLS (Pure Live Seed) would be about 81%. Another bag could have the same germination, but a purity of 98.5% which would yield over 86% PLS. A difference worth quibbling over? Figure about 22,000 PLS for each 1% gain, and that turns out to be over 110,000 PLS increase! Certainly worth paying more for! The purity should be as high as possible to assure the lowest count of unwanted inert matter and weed seed.

Current Research Efforts in Turfgrass Include:

1. Endophyte enhancement of all turfgrass species
2. Use of growth regulator Primo (trinexapac-ethyl) to control annual bluegrass seedhead formation, improve turf quality.
3. Root-zone temperature adjustments for improved bentgrass green quality.
4. Controlling nutrient and pesticide leaching and runoff via various cultural methods
5. Cold temperature tolerance of perennial ryegrass and tall fescue.
6. Cultural practices to develop deeper root systems, for both drought tolerance and to lower stress in putting greens.
7. Testing bentgrass cultivars under stressed conditions to determine the best, using ‘Penncross' as a standard of comparison.