Tall fescue: Pasture renovations

by Tamara Scully

If the benefits of Kentucky 31 tall fescue don’t outweigh the risk of toxicity, or its propensity to out-compete other forages, it is possible to renovate and remove this controversial forage from your pastures.

Before renovating, though, a cost-benefit analysis is needed. The benefits can include increased productivity of your herd, with increased weaning weights, increased milk production, higher average daily gain and better breeding weights. Costs include the time, labor and expense needed to undertake the renovation, Dr. Amanda Grev, University of Maryland Extension forage specialist, said. She recommended renovating one-quarter of your pasture acreage at a time, selecting pastures which are thinning, weedy or those which are dedicated to breeding animals in order to capture the most value from the renovation.

But don’t expect to follow a standard renovation protocol. There are three systems for completing a successful K31 pasture renovation, and all rely on proper timing to prevent this aggressive grower from re-establishing itself in your new forage.

“You really want to be doing this cool season establishment planting in the fall,” Grev said, so each method involves advanced preparation for that final autumn sowing of the new forage.

The first option is to use herbicide to kill the stand and the weeds in late spring, allowing for early season grazing. The kill step should be done prior to the seed heads forming. K31 tall fescue can be clipped to prevent seed head formation if the stand cannot be eliminated prior to seed head formation.

Following the kill step, a summer smother crop is planted. This will add soil fertility and organic matter and provide forages for grazing. Any warm season annual forage, such as sudangrass or pearl millet, works well. The seeding rate should be slightly lower than normal, to allow any K31 that survived the herbicide treatment to grow back now. If K31 is still viable, having it grow now will be the best shot at eliminating it with the final kill step.

A second herbicide spray in autumn is used to eliminate any regrowth of the K31 tall fescue. This should occur in mid-August to mid-September, allowing time to plant the new forage species of cool season perennials at the optimal time, allowing it to establish prior to winter.

The second strategy is to plant a smother crop in winter, using a small grain such as wheat or barley. Grev cautioned not to plant annual ryegrass, which establishes quickly and is hard to eliminate. Before planting the winter smother, spray herbicide in autumn, killing the existing stand of K31, along with any weeds. The winter smother crop should provide forage in autumn, then grow back and provide spring forage as well.

In the spring or summer, depending on the timing of the harvest of the smother crop, an herbicide is applied to terminate the smother crop, any remaining K31 and any weeds. Next, either plant a summer annual forage or leave the ground fallow. In autumn, the new cool season perennial forage will be planted as in the first strategy.

The final method does not involve a smother crop, but consists of clipping the K31 tall fescue in spring to prevent seed heads, applying a herbicide in late July as the forage begins its summer slump and then waiting four to six weeks prior to planting the new crop in autumn. This waiting period allows time for any K31 tall fescue to regenerate, so it can be eliminated before the new forage crop is sown and gets new seeds in the ground at the optimal planting time. A final spray prior to seeding the new perennial forage is then applied. This method does not involve as much seed cost, since there is no smother crop.

The smother crop methods have the added benefit of providing forage for grazing or harvest and the opportunity for improving soil health. Failure of the new forage stand can occur if soil pH or phosphorous levels are not optimal, and increasing organic matter and improving compaction and fertility with a smother crop can help establish proper growing conditions for the new pasture forage.

“You can use these annual crops to help with some of those health components while you’re going through this renovation process as well,” Grev said.

Other reasons for failure of a new forage stand include planting at the wrong time or in adverse weather, improperly prepared seed beds, excessive competition from weeds or from the existing stand or bad seed. Planting seed too deep is also a concern, and equipment should be properly calibrated.

Once your new stand is planted, it is important to manage it carefully. Do not overgraze or graze when wet. It may work best to hay the field the first year, rather than graze it (if possible). Do not feed K31 tall fescue hay in the new pasture, as it could seed there again and overtake the new forage. Likewise, do not introduce K31 seeds into the new stand via equipment, clothing or livestock. If there are seed heads in any K31 fields, they can be transferred by livestock and remain viable for two full days, so do not graze animals in K31 tall fescue when seed heads are present and then immediately move them to a newly renovated stand.

“Tall fescue is very persistent. It’s very hard to eliminate,” Grev explained. “Take the time to do the renovation process properly,” with the goal to achieve “a good stand of your new forage that’s pure and free of that toxic fescue.”

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