Friday, February 4, 2011

Grass 101

Stemless hymenoxis, a native perennial forb in High Plains rangeland, provides a splash of color on this shortgrass prairie in the southwest Panhandle. Grass species in the photo include green needlegrass, buffalograss and blue grama, and scattered crested wheatgrass.
Though we're mired in the depths of winter today, spring is just around the corner. As air and soil temperatures begin to creep up, the praire, pastures and rangeland of the High Plains will begin to wake up. Grass is more important than you might think, so let's talk grass. If you got here looking for information on hippy lettuce and left-handed cigarettes, you're on the wrong blog.

Whether a herd numbers thousands of head or comprises a single 4-H goat, grass is one of the two most vital requirements for the livestock producer. Without good forage and water, livestock production is simply impossible. Leaving water aside, it follows that grass is so vital to producers that each operation must arm itself with graduate level knowledge of grass in general and an intimate and comprehensive understanding of their owned or leased rangelands.

Nearly all producers possess such knowledge and understanding. They simply wouldn’t survive otherwise. But often their knowledge exists as scattered bits of formal and informal information, institutional memory and habit, and the kind of sixth sense developed over years of experience.

Cows and calves on a native shortgrass prairie south of Kimball, Neb. Grass and grass-like species providing forage on this pasture include threadleaf and needleleaf sedge, green needlegrass, western wheatgrass and crested wheatgrass, buffalograss, blue grama and hairy grama.
In the twenty-first century, and especially here on the semi-arid Wyo-Braska high plains, savvy operators have learned that combining knowledge and experience can pay dividends when it comes to making decisions on grazing and range management. Today’s operator can take advantage of a wide range of information and research in the quest to combine knowledge and understanding into an integrated operational management scheme. Land Grant Colleges like the Universities of Wyoming and Nebraska provide a wide range of Extension services and products. Private ag sector businesses provide many services and products as well. And cooperative ventures such as the High Plains Ranch Practicum allow the free exchange of information and experience between public and private sectors and the operators themselves.

Let’s take a look at the basics of the High Plains rangeland ecosystem, and in particular, grass.

A semi-arid vegetative zone generally has annual precipitation between 10 and 20 inches and an overnight temperature falloff during the summer months. Another characteristic is the wide annual variation in the timing of precipitation, as well as the quantity of precip delivered during the events. The possibility of drought is never far away on the High Plains.

With grass such an important part of livestock production, it pays to know as much as possible about the rangeland used for the operation. Whether owned or leased, the operator needs to know what’s available for grazing, what shape it’s in and what its growth characteristics are to make the best short- and long-term use of this vital asset.

This curious 13-lined ground squirrel stands amid the bounty of the shortgrass prairie, surrounded by cool and warm-season grasses and native perennial wildflowers.
This knowledge starts with a basic understanding of what grass is and what it does. Simply put, grass is the major energy source for all terrestrial (land) animals. Grass photosynthesizes carbohydrate from sunlight, atmospheric carbon dioxide and water, storing the energy-dense nutrient in above ground foliage and below ground roots. Grass makes up the base of the terrestrial food pyramid and constitutes the main (or a significant part of) food source of terrestrial herbivores, which are in turn consumed by omnivores and carnivores. It’s no exaggeration to say that all terrestrial life is grass fed.

Rangeland is a discreet ecosystem, easily as complex as the most pristine rain forest. Rangeland grasses are unique in the plant world in that their root systems are more extensive than their above ground herbage. In shortgrass rangeland root systems can be five or more feet deep; some tallgrass stands root to a depth of better than 30 feet.

These extensive root systems allow grasses to find and use water and nutrients throughout the soil profile, which helps them survive in dry years and explode with herbage production in wet years. They also anchor soils and provide a rich environment where symbiotic microorganisms thrive and boost soil fertility. Many rangeland grasses reproduce through their root systems as well, pushing rhizomatous stems out beneath the soil from which new plants arise.

Here on the Wyo-Braska High Plains, native and reintroduced rangeland grass species include cool and warm season grasses and grass-like plants (sedges). Native range is shortgrass prairie, and reintroduced grasslands shortgrass species with a scattering of mid-height grasses.

Sedges are usually the first to green up in the spring, followed by cool-season and then warm-season grasses. There is considerable variation between species and even within species according to location, but most grass growth occurs during 30-60 day rapid growth periods corresponding to the onset of particular air temperatures. In general, maximum growth in cool-season grasses occurs when air temperatures are 65 to 75 degrees, while max growth of warm-season grasses occurs with 90-95 degree air temps.

Such growth characteristics allow range grasses to produce the bulk of their above ground herbage during a relatively short period each year. The staggered peak growth periods between types and species generally provide a three to four month annual period of lush, palatable and preferred forage for selective grazers, likely as a result of rangeland ecosystem evolution. Peak growth occurs relatively early in the season, and once past this heavy herbage production period, above ground growth slows markedly, with the plants essentially in maintenance mode until hard freeze.

Herbage production and plant growth during peak growth is highly correlated to soil moisture and air temperature. Both are required. Under severe drought conditions grass may remain essentially dormant. If moisture is available, however, peak growth will occur when air temperatures are appropriate and will be limited by moisture availability. In wet years herbage production will be abundant, in dry years production will be sparse.

Aside from herbage production, which is so essential as forage to livestock producers, root growth and development is at its highest level during peak growth. With root systems making up the bulk of grass plants, root development is obviously vital to the range ecosystem. Carbohydrates derived from photosynthesis provide the plant with the energy needed for both above and below ground growth. When carbohydrate production is reduced by grazing, the plant diverts energy from root development to herbage production in an effort to maintain photosynthetic carbohydrate production. This shift from below to above ground growth has been called root mining. Depending on factors like grazing pressure, soil moisture, and air temperature, root mining can be detrimental to the long and short term health of the plant, and by extension, the range ecosystem. Heavy grazing during drought can debilitate an entire pasture, which may take years to recover. Even modest grazing during peak growth results in some level of root mining. The operator’s challenge is to understand his rangeland and livestock as a discrete system and introduce management practices which enhance both profitability and sustainability.

In general, most recommended range management schemes include dividing range into a number of pastures and rotating grazing dates and periods between them from year to year. In a four-year rotation, a particular pasture might be heavily grazed during peak growth one year, rested the next year, then lightly and moderately grazed in the next two years.

Range management plans will necessarily be different for different operations. No two rangeland parcels are alike, weather varies from year to year, and grazing requirements change according to economic and other variables. Designing and implementing a range management plan can be a complex and daunting task, but armed with knowledge and experience, operators can employ powerful strategies to maximize both profitability and sustainability.

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