WARSAW, Mo. – Weed and brush control in pastures and hayfields always generates a lot of discussion among forage producers. Before control recommendations can be made however, some relevant information is necessary, such as what are the weedy species, how prevalent are they in the field, and what is the soil fertility of the field. Plant composition and soil fertility are key components in the decision making process of how to deal with weedy or thin forage stands.

Plant counts are easy to take. One method is to stretch a 100’ tape measure across the field. At every six inch or one foot mark, identify what is touching the tape – bare ground, weed, grass, or legume. Write this information on a piece of paper along with other pertinent information such as the name of the weed, grass or legume. Take several counts around the pasture and sum up the results. Soil samples can also be collected at the same time plant counts are being taken.

After plant composition and soil fertility are known, decisions can be made on how to correct problems. Weed infestations are generally the biggest issue in thin pasture stands, but most producers are reluctant to spray weeds because broadleaf weed herbicides kill existing legumes. However, if legumes are only a small part of the pasture and are outnumbered by weeds, it may be best to control the weeds and then thicken up the pasture by interseeding additional legumes or grasses at a later date. Additionally, MU research has shown that cattle prefer grazing in areas that have been sprayed to remove broadleaf weeds.

If complete pasture renovation seems to be the best option, correct weed pressure and soil fertility issues before progressing further. In addition to weed pressure and soil fertility, many other factors impact the decision about pasture renovation including when forage is needed, the quality of forage needed, and how much can be spent in the renovation process.

In some cases, renovating a portion of the pasture may make the most economic sense. The University of Arkansas conducted research in which they converted 25 percent of a tall fescue pasture to a novel endophyte tall fescue variety. Spring calving cows grazing tall fescue with the novel endophyte for 60 days, beginning 30 days before the start of the breeding season had a 21 percent improvement in pregnancy rate compared to cows grazing unrenovated tall fescue pastures.

Killing out an existing KY-31 tall fescue stand and re-establishing one of the novel endophyte fescue varieties may take from one to two growing seasons, depending on the smother crop used and pressure from undesired plants after the initial spray application. Assessing stands and starting the renovation process needs to start soon, if producers want to establish one of the novel endophyte varieties.

Improving pastures and hay fields is a complex issue, but there are viable options for addressing the problem of thin or weedy fields. If you desire more information on this topic, contact me by e-mail at schmitze@missouri.edu or call the Extension Center in Warsaw at (660) 438-5012.