Pasture & Range: October 2001

Bermudagrass Blues — there ought to be a country-western song with that title. The sorry state of bermudagrass in southern Oklahoma is enough to inspire one. Right or wrong, most cattle producers in these parts spring calve. Bermudagrass is most often the forage that they depend on to carry calves until fall weaning. If bermudagrass stands produce poorly, things such as milk production, average daily gain, weaning weights and potential earnings can decline.

Bermudagrass is highly drought tolerant. Because of its many growth points and low-growing leaves, it also tolerates grazing pressure, but everything has its limits. Ongoing drought and heavy grazing pressure have weakened many of the region's bermudagrass stands. A plant's leaf area largely determines its growth potential. If you graze a plant low enough to remove most of its leaves, you severely handicap its regrowth ability. If you do it continually, you reduce seasonal production potential, but bermudagrass's ability to temporarily tolerate these conditions often fools people. If the bermudagrass for your cattle is one to two inches tall, you probably don't have enough to maintain your livestock, so you're hurting not only the grass but also your cattle by overgrazing.

First, manage for proper stubble height. Leaving a few extra inches of bermudagrass on pastures going into the winter is not a waste: within several years it can improve your pasture. Leaving three to four inches of stubble can protect bermudagrass crowns in winter and improve spring production, depending on variety. Added stubble inhibits cool-season grass establishment and competition for resources, and it means you're taking care of the aboveground portion of the plant, which in turn maintains the roots. Adequate stubble maintained before frost can make a big difference in the spring when the plant temporarily draws from root carbohydrate reserves for early production.

Figure 1            Photo: Matt Mattox

Competition for sunlight and moisture can severely hamper bermudagrass production and is often from cool-season forages such as ryegrass, rye, wheat, triticale and oats overseeded on bermudagrass pasture to annual bromes, Texas wintergrass and others that encroached on the pasture because of heavy grazing pressure. All of these grasses can be managed to produce high-quality forage for cattle, but if they are left on a pasture too long, they can reduce production and vigor of bermudagrass. For example, cool-season grasses, such as ryegrass and wheat, use different chemical pathways during photosynthesis than warm-season grasses, such as bermudagrass. This difference enables most warm-season grasses to more efficiently convert sunlight into groceries for livestock. One notable difference is that production of warm-season grasses increases as sunlight intensity increases, while production of cool-season grasses peaks at 30 to 50 percent of full sunlight. So if you allow ryegrass to grow into late May or early June, it can't convert sunlight as efficiently as bermudagrass could if it weren't being shaded by the ryegrass. Note the lush, productive ryegrass behind the fence (figure 1). This amount is fine in April, but should be managed through grazing or haying to look like the grass in front of the fence by early May to reduce competition with bermudagrass for sunlight. Staying on top of cool-season grasses is hard because of spring growth, but if you start by overseeding just enough grass to meet your needs, conditions should be more manageable through grazing in the spring. Overseed no more than one-third of your bermudagrass, unless you're sure you have enough cattle to use it by early May. Getting the grass off in early May is often difficult if you rely on standard haying procedures, and often the hay quality declines because of extended drying times and rain. Think twice before overseeding any bermudagrass hay field.

Competition for water with cool-season grasses or weeds is another cause of low production or decline. You should consider that bermudagrass has a six-month growing season, mid-April to mid-October. The Carter County Soil Survey lists an average rainfall of 20.64 inches during that period. Research shows that it can take 15 to 20 inches of water to make a ton of bermudagrass with no added fertility. If ryegrass is overseeded on bermudagrass and is not grazed out until the beginning of June, you could forfeit about 6.5 inches of rain (or 30 percent of the rainfall in the growing season) that could have been used for bermudagrass growth. Using 20 inches of water per ton of forage and our remaining potential of 14 inches, we could reduce potential yield to 1,400 pounds per acre.

Figure 2            Photo: Matt Mattox

A proper fertility program keeps bermudagrass stands productive. Proper fertility inputs with the right timing also limits weed and native grass competition. Note the encroachment of native grass in this bermudagrass hayfield (figure 2). As applied nitrogen increases, crude protein and yield increase, while water required per ton of forage production decreases (Stichler, 2001). Therefore, a good stand of bermudagrass with 100 pounds of applied nitrogen will require only about 10 inches of water to produce a ton of forage. If you remove ryegrass competition by late April, you could grow 4,000 pounds of forage per acre with average rainfall. Lately, however, most of our rain has fallen during the winter and early spring, more justification for removing cool-season forage competition from over seeded bermudagrass by early May.

Timing of fertility is essential. If you have cool-season competition, postpone fertilization until early to mid-May, or you'll end up helping cool-season forage reduce bermudagrass production.

Weed control is especially important on a new stand. Use Diuron if you plan to sprig bermudagrass next year. Apply this herbicide immediately after sprigging but before new growth for control of broad-leaves and some grasses. You may also need postemergence herbicides. Always follow label directions.

Soil pH should be corrected if it's 5.0 or lower. Since bermudagrass will shortly be dormant, it is a good time to test the soil for nutrient deficiencies and begin correcting soil pH.

If you manage your bermudagrass properly and we receive some needed rain this fall, maybe we can take the Bermudagrass Blues off the charts next year.

See also:
Stichler, Charles. Forage bermudagrass: Selection, establishment, and management. Texas Agricultural Extension Service.