I have received numerous questions regarding Prairie Threeawn control in Pottawatomie County. I generally begin to answer the question by "you're probably not going to like what I have to say." Prairie Threeawn is a very common grass growing in many of our pastures and range sites. It is also known by other unaffectionate names such as "old-field threeawn" "ticklegrass" or "wiregrass." In some fields, it appears to be the dominate species present. This annual shortgrass is named for its habit of establishing in old hay fields, abandoned crop fields or deserted oil well locations. It can become easily established under adverse conditions. It is what we refer to as an indicator grass, pointing to deteriorated range sites that are either heavily eroded, routinely overgrazed, or lacking in nutrients. Prairie threeawn is practically useless as a forage grass. It is unpalatable, difficult to chew, very low in quality and the seeds can get into in the eyes of both cattle and sheep and cause eye problems.
Chemical Control- Unfortunately, there are no good herbicide options labeled for the control of threeawn. About the only chemical that can be legally applied is glyphosate, and it is nonspecific, killing most species of green grass or forbs it contacts. In the 80's a product called atrazine was labeled on pastures that seemed to have some impact on threeawn, but it has been removed from the label. Glyphosate can be applied at 8oz/ac in a bermudagrass pastures but not in native pastures.
Prescribed fire- There is an older research article from Kansas State University that indicated producers could get reasonable effective control of threeawn by doing a prescribed fire in the fall of the year on native range. The best results were with a burn in November. The theory is to burn the seeds off the plant while they are attached to the stems. By waiting until December, it decreased the level of control because the seeds detached from the plant and fell to the soil surface.
Fertility- If the cause of the threeawn in the first place was low fertility, then it's likely to come right back unless a correction to fertility takes place. In most instances, the critical lacking nutrient in threeawn areas is phosphorus (P). 18-46-0 (DAP) is a good source of phosphorus fertilizer in deficient soils. In bermudagrass pastures, we recommend that you fertilize according to soil test recommendations to encourage the bermudagrass stand to thicken and cover. A 100 lbs per acre or more of DAP will meet the P needs of this year's crop and maybe start building back some residual (P) in the soil. Manures, chicken litter, stall cleanouts and similar products are another good source of phosphorus.
In native grass pastures, there are vigorous debates on the economics of applying fertilizer. Agronomically we know that we can improve the stand and reduce threeawn. If you have threeawn in native areas do you have any options? First, it did not get in the shape it is overnight and it will take some time to recover. If threeawn is encroaching strongly consider grazing instead of haying. Use a light stocking rate and allow a rest period for recovery during the latter part of the growing season. Feed hay or put feed troughs during the winter in the worst threeawn areas. The extra manure and organic matter will help over time. There is not a quick fix for Prairie Threeawn control in pastures. It will take time to recover and an integrated management approach must be practiced in order to manage this annual grass.
Threeawn in our pastures is showing us that something in the production system is not working properly. Drill down to the root reason that threeawn has the competitive advantage over your other more desirable plants. By fixing the root issue, we truly fix the problem instead of putting on a band-aid. This will eliminate many years of frustration. If you have additional questions about threeawn or other problem grasses please come by 14001 Acme Rd Shawnee, call (405) 273-7683 or email firstname.lastname@example.org<mailto:email@example.com>