Robyn Stewart
An excessive amount of weeds in a pasture or hayfield can be unsightly and unattractive at best, and may also significantly decrease the quality and stand life of desirable forage species at worst. A weed is defined as any plant growing where you don’t want it to. For example, crabgrass growing in a bermudagrass hay field could be a weed, the same way bahiagrass growing in that same hay field would be considered a weed. Many weeds are more aggressive than existing desired forage species. By aggressive, we mean that weeds will often outcompete the desired species for resources like light, water, and nutrients. As weeds mature, they can reduce the palatability (willingness of the animal to graze that pasture) and nutritional quality of that pasture. Some weeds can be poisonous to livestock as well. It is important to note that some plants considered to be weeds, such as crabgrass, are actually fairly nutritious to livestock and may not be as big of a concern as a more problematic weed, such as the buttercup we are seeing this spring.
As with any pest management concern (and weeds are considered to be pests), landowners are encouraged to use an Integrated Pest Management (IPM) approach that contains multiple control methods. The first thing to consider is the nutrient and pH status of your fields- if the pH or nutrient balance is not ideal for your desired species, you may wind up with soil conditions that favor and promote weed growth. Correcting pH and fertility should be the first step in pasture management to promote a vigorous, healthy stand of grass. The second thing to consider is grazing management and stocking rate- the number of animals on the field. If pastures get overgrazed, the existing desired forage species often become stressed, which allows weeds to get established. Livestock will often graze weeds when they are young and small, but as the weeds mature, they become less palatable and nutritious and will get left behind in favor of the desired grass species. Be careful to consider the actual forage production of your fields when you are determining the number of livestock it can sustain- and remember that more intensive management can increase stocking rate, while a lack of management will decrease stocking rate. Mowing is another effective method of mechanically reducing the broadleaf weeds in a pasture by reducing the amount of seed they can produce. The mower should cut as close to the ground as possible, and typically will not completely eliminate weed seed production. In other words, even if you mow, expect some weeds to reappear. It is important to note that mowing will not control perennial weeds that spread via underground rootstock. A final method to help control weeds is the use of an herbicide to provide broad-spectrum weed control. The first step in choosing an appropriate herbicide is to identify which weeds you are trying to manage, and to select a product that will control as many as those types of weeds as possible. Using a broad spectrum herbicide will provide the best weed control while reducing cost and labor. Consider whether you are interested in a pre-emergent or post-emergent herbicide. Pre-emergent need to be applied early in the season before the weed seeds can germinate, while post-emergent are used to kill seeds after they germinate. With any herbicide product, be careful to use proper herbicide safety standards to protect surrounding crops, forests, and other plantings from things like spray drift and runoff. Also keep in mind the grazing and feeding restrictions for any herbicides and adhere to any restrictions that are specified. Herbicides can be very effective and combined with other grazing management and mowing can significantly improve weed burden on pastures in a cost effective manner, however, they will not solve existing pasture management issues. Using an herbicide without any other management changes such as stocking, mowing, and soil fertility changes will often result in the same recurring weed problems over time. If you need help developing a pasture management plan, reach out to us at uge3181@uga.edu or 706-359-3233.
