Evaluating Fall Horse Pastures: Green is Good, Brown is Bad

If your cool-season grass pastures are green during the fall, chances are they’re healthy and productive.
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Evaluating Fall Horse Pastures
If your cool-season grass pastures are green during the fall, chances are they’re healthy and productive. | Photo: iStock

Changes in foliage color tell us that fall is here and winter’s on its way. Some of these changes are beautiful, such as the maple leaves turning vibrant red and orange. Others aren’t so breathtaking—the pine needles turning brown and piling up under the tree, for instance.

But for cool-season grasses, color changes can tell us much more, about the pasture’s makeup and health, for example, and give a brief snapshot of the pasture’s composition of a pasture. In short, if your cool-season grass pastures are green now, that’s good. If they’re brown, that’s bad.

Cool-season grass species dominate pastures in the transition zone and northern tier of the United States (which extends north from Tennessee). These species include Kentucky bluegrass, orchardgrass, tall fescue, ryegrass, and smooth bromegrass. Cool-season grasses thrive best in the spring and fall, when daytime temperatures are between 60-75oF. During the spring, plants are emerging from dormancy and growing rapidly. In fall, these plants are busy preparing for winter by storing energy in their roots and producing new tillers. Fall nitrogen applications help this process along, further boosting root development, enabling plants to better survive winter and green up earlier in spring. It isn’t too late to apply fall nitrogen in most areas. For more information about fall nitrogen applications, see Soil Sampling and Nutrient Management.

In contrast to cool-season grasses, warm-season grasses should now be on their way out. These forages, such as crabgrass, foxtail, nimblewill (which isn’t grazed by horses and considered undesirable), and bermudagrass grow best when temperatures are over 80oF. Except in the deep south where these grasses dominate, cooler temperatures cause these grasses to begin dying (or going dormant in the case of nimblewill and bermudagrass). Some warm-season grasses, such as foxtail and nimblewill, generally aren’t good-quality forages or aren’t palatable and, therefore, are not ideal in pastures. Species such as crabgrass can be high-yielding and nutritious, but still might not be ideal in northern regions because of their short growing season. Bermudagrass is a perennial that will survive winter, if located far enough south; it rarely thrives north of the Ohio River and unless managed carefully and exclusively.

For horse owners or managers with cool-season grass pastures, fall (especially after a frost) is an excellent time to quickly evaluate pasture health and productivity. If green grasses dominate the pasture, it’s likely that your cool-season grasses are growing with ideal temperatures and rainfall and good soil fertility. Brown pastures, on the other hand, are probably either dominated by warm-season grasses, or your cool-season grasses are being starved of soil fertility and acceptable growing conditions. While managers can’t make up for warm temperatures or poor rainfall, they can take steps to determine if pastures are deficient in soil nutrients or overrun by warm-season grasses. Your local county extension agent or farm consultant can assist in identifying cool- and warm-season grasses, as well as collecting soil samples.

Measuring Green Cover: There’s an App for That

Most horsemen should be able to look at a pasture and gauge the overall health by color. But for those who want a more objective measurement, there’s an app for that. Oklahoma State University developed Canapeo, a multipurpose green canopy cover measurement tool which allows users to photograph a pasture and analyze the photograph for green and brown pixels. Green pixels show as white and are healthy, living, productive material (but remember that green weeds will also be included). Brown pixels are shown as black and represent bare soil, dead or dying material, or dormant plants.

Ideally, the app developers say, pastures should be more than 60% green when being grazed. Pastures with less than 60% should be monitored closely, and those with less than 40% green should not be grazed. While this app cannot replace a visual inspection by horse farm managers, it does provide a more objective measure of pasture health. Canapeo is available for free in both the iTunes and Google Play stores.

Figure 1A and 1B
Left: Figure 1A, Right: Figure 1B

In this Central Kentucky pasture (Figure 1A), horses grazed the cool-season grasses on the top and upper slope all summer while allowing warm-season grasses to grow. However, they were reluctant to graze in the valley below. This, along with good soil moisture from a leaking water tank, means the valley area is still covered in cool-season grasses and makes for a dramatic difference for fall grazing availability.

Figure 2A and 2B
Left: Figure 2A, Right: Figure 2B

While designed for close-up pasture photos, Canapeo detected green in 29% of this picture, with green areas (the valley) in white and brown areas (the hill top) in black (Figure 1B). A close up of the hill top area (Figure 2A) shows it is heavily dominated by crabgrass, which takes on a dull green/brown color in Kentucky in mid-October. Canapeo detected only 8% green in this photo (Figure 2B). In the same pasture, the valley area is still dominated by cool-season grasses (Figure 3A); lush orchardgrass, tall fescue, and white clover growth is abundant, with green tissues detected in 98% of the photo (Figure 3B).

Figure 3A and 3B
Left: Figure 3A, Right: Figure 3B

What can you do when fall pastures are struggling?

Cool-season pastures overrun with warm-season grasses likely were heavily grazed over the spring and summer. Apply fall nitrogen on these pastures to stimulate the remaining cool-season plants. Other soil fertility requirements, such as phosphorous, potassium, and lime, can be determined by a soil test, but these products can be applied anytime the weather allows. Any fertilizer should be applied when leaves are dry to the touch, but not during periods of drought. Spring (or ideally next fall) seeding might be needed to boost pasture production.

Take-Home Message

Late fall, after a frost, is an ideal time to visually evaluate your cool-season pastures’ health and productivity. With cool-season grasses and legumes active and warm-season grasses dying or going dormant, color is a simple way to observe the overall composition of your pasture. Remember the phrase originally coined by A.J. Powell, Jr., PhD, a former turf specialist at the University of Kentucky (UK): “Green is good; brown is bad.”

Krista Lea, MS, UK Horse Pasture Evaluation Program coordinator, and Tom Keene, MS, hay extension specialist, both within UK’s department of plant and soil sciences, provided this information.


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More information on Gluck Equine Research Center and UK Ag Equine Programs.

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