Weeds can be a serious detriment to the nutritional value of forage crops unless proper management is practiced, says Todd Lorenz, horticulture/agronomy specialist. Most weeds are lower in protein and less palatable for livestock, and in some cases, weeds can be poisonous to livestock (for poisonous plant species, follow this link

“Every space occupied by a weed is a space where quality forage could be produced,” Lorenz says. “Weeds compete for sunlight, moisture and nutrition similarly to the way we think of row crops.” But rather than first turning to herbicides to rid pasture of weeds, remember that proper forage and grazing management promotes healthy stands that will give the beneficial species vigor and the competitive edge over weeds.

If the plants are allowed to rest through rotational grazing, says Ed Rayburn, forage agronomist with West Virginia University Extension service, the root system will stay healthy and the plants can build up energy reserves in the tiller base (grasses) and roots (legumes) for later growth. Under drought conditions when plants are rested and allowed to build up energy reserves, there will be compensatory growth by pasture plants when rainfall finally comes. Plants overgrazed during drought will grow slowly in comparison.

“By resting drought-stressed pastures until mid to late November, energy reserves will increase since plants will catch sunlight and make sugars even when it is too cold for the plants to grow,” Rayburn says. “Also during this time of year, grasses will develop new tiller buds necessary for next spring's forage production. With overgrazing in the fall, the pasture's growth potential next spring is jeopardized.”

Keeping cattle rotated through pastures and letting pastures rest following drought are just some things to boost beneficial forage production, helping keep weeds at bay. “Weeds are typically more competitive in thin, declining stands and in situations where soil fertility is below average,” Lorenz says. “Even in closed systems, soil pH can decline over time due to the nitrogen cycle and annual precipitation.”   Soil sampling and testing can help determine soil fertility.

If you have confidence in your management practices, there are still situations that require a look at herbicide applications, Lorenz notes. He recommends the University of Missouri Extension publication MP581, “Weed and Brush Control Guide for Forages, Pastures and Noncropland,” as a resource to improve management practices. It covers management practices, herbicide application timing, forages, grass pastures, brush and woody plant control, etc.

In addition, the publication includes a table of weed response to herbicides where a rating of poor to good can help determine the best herbicide for your weed problem. It lists herbicide management practices for cool season and warm season grasses, as well as forage legumes. It covers many of the common weedy species of perennials, biennials, summer-winter annuals and woody species.

The publication costs $8 through the Missouri Extension Web site. Your state’s Extension office might also have a similar publication that you can obtain specific to your region’s forage species.