By Rory Lewandowski

“My biggest pasture weed problem is foxtails. What should I do to control them?” This was the comment and question of a recent phone call I received.

Foxtails — yellow, green and giant — are annual weeds. In a pasture situation, annual weeds such as foxtails, ragweed, pigweed, crabgrass and barnyardgrass are the result of pasture management.

These weeds require soil disturbance and bare soil to germinate and grow. Any practice that opens up or destroys the sod base allows these weeds to flourish.

My caller admitted that those foxtails were growing in an area where hay had been fed in bale rings. Since foxtail is not a desirable forage species, consider options to improve or renovate that pasture area.

Late summer provides a window of opportunity to renovate weedy or thin pasture areas, and there are a couple of good options to accomplish that task. The first step in any pasture improvement or renovation is a review of the soil pH and soil fertility levels.

Do you have a current (less than three years old) soil test for the pasture area you want to improve? If not, start with collecting a good soil sample. For pure grass stands, soil pH should be a minimum of 6.0, and preferably 6.3.

If legumes are in the mix, soil pH should be in the range of 6.5 to 6.8. Soil phosphorus levels are important to help a new seedling develop a root system. Minimum soil phosphorus levels requirements are 15 ppm Bray P1 (28 Mehlich 3) for pure grass stands, and 25 ppm Bray P1 (40 Mehlich 3) for legume or legume-mix stands.

Potassium is generally associated with winterhardiness, and it plays a role in disease resistance.

For most Ohio soils, a test level of 100 to 120 ppm is a minimum recommendation. Make any needed adjustments to soil pH or soil fertility before adding any forage seed.

An important consideration for my phone caller, and for most pasture renovation projects, is weed control.

Controlling weeds
Control weeds, especially perennial weeds, before planting any forages. Control options include mowing, tillage and herbicides, or a combination of these methods.

Mowing annual weeds after they have entered seed formation, but before seeds are viable, can provide some control. Mowing, unless done multiple times, is not as effective for perennial weeds, because they can draw upon root reserves to regrow.

Tillage provides good weed control, especially for annual weeds, and it generally sets back perennial weeds enough to reduce competition and allow new forage plants to establish. Tillage is also useful to level and smooth out a pasture area that has ruts and rough spots due to winter feeding and/or intense hoof action.

The downside is that tillage can also provide opportunity for other annual weeds to germinate, and perennial weeds may regrow. Additionally, tillage is not suitable for many pasture situations because of the risk of soil erosion.

Herbicides work well for no-till seeding or in combination with mowing and tillage. The two primary herbicide options in pasture renovation are burndown with paraquat (Gramoxone), a non-systemic contact herbicide; or use of a systemic glyphosate product, either alone or in combination with a 2,4-D product.

The paraquat option is attractive when there are desirable perennial forage plants in the stand because the chemical will not kill them, only burn the top growth off. Note that paraquat is a restricted-use pesticide requiring a pesticide license to buy and use.

The options with glyphosate or glyphosate plus 2,4-D should be used when the intent is to kill everything down to the roots and start over. Always read and follow label directions regarding rates, timing, planting restrictions after application, application volumes and personal protective equipment.

Forage options include planting either an annual or a perennial species. The Ohio Agronomy Guide recommends completing the planting of perennial legumes by the end of August. There is a little more leeway for perennial grasses, but even so, the recommendation is to complete planting by early September.

If you need to pull a soil test and then apply lime or fertilizer, there may not be time to get planting completed by these dates.

In some cases, if 2,4-D was used in an herbicide tankmix, there may be a wait period before planting, because 2,4-D can have some soil activity.

Check the label
What are options for September planting dates? You can take a chance and plant later. Depending upon the kind of fall we have, the planting could still be successful.

Another option is the use of annual small grains. Small grains like winter triticale, winter wheat and winter cereal rye can all be planted in September and even into October; they provide good cover to reduce soil erosion over the winter. When planted in late August to early September, small grains provide some late-fall grazing.

All these species will overwinter and start growth in early spring to provide some spring grazing as well. Late summer and early fall provide an opportunity to control problem weeds in pastures and renovate the pasture stand.

Lewandowski is an Ohio State University Extension educator for Wayne County.