Weed Management Is Important for Maintaining Healthy Pastures28 January 2014
A University of Arkansas Professor says that canopy cover is the best prevention against encroaching weeds.
Dr. Dirk Philipp, Assistant Professor at the University of Arkansas believes that weed control in pastures is one of the most important aspects of forage management.
Pastures with a high degree of weed infestation are not just unsightly, they also point to incorrect decisions related to soil fertilization and grazing management, he writes.
Taking care of weeds as part of a continuous effort to improve pasture productivity will pay off in the long term with improved animal productivity.
Weed control does not necessarily mean maintaining forage monocultures. During certain years, some grass and broadleaf species find just the right conditions to thrive. In 2013, crabgrass was a problem in many pastures along with johnsongrass. Both species benefitted from droughty conditions during previous years. Both species are actually very palatable forage species by themselves, but depending on specific pasture management goals, these plants might be undesired in pastures managed primarily for perennial cool-season forage stands.
"Among the many things that constitute good weed control, proper timing of grazing ensures good forage utilization and plant regrowth during rest periods"
Research has shown that there is no such thing as a 100 percent fescue or bermudagrass stand. In fescue fields, for example, about 60 to 75 percent of the forage base may be fescue while the remainder could be comprised of other cool- and warm-season forages such bermudagrass, orchardgrass, crabgrass or native grass species and broadleaf plants. In naturalized grasslands, which are basically the grasslands present in the eastern U.S., pushing pasture plant composition towards certain species and maintaining those long term can be a daunting task. This is because weeds are vastly more aggressive in their growth habit than specially bred and selected forage species, which only thrive within a relatively narrow window of soil fertility, pH and grazing management. To keep these factors as close to optimum as possible is the job of the farm manager.
The best defense against encroaching weeds is canopy cover throughout the year with forage species that fit the longterm grazing management plan. This will require maintaining proper soil pH and fertility. Both can be checked for free by turning in soil samples to the Cooperative Extension Service on a regular basis. Among the many things that constitute good weed control, proper timing of grazing ensures good forage utilization and plant regrowth during rest periods, which will result in good canopy cover. Newly renovated pastures should be allowed to become established well before use while following the recommendations for firstyear management.
Although some broadleaf weeds can have a high nutritive value early during their life cycle, effort should be made to limit their presence in pastures, as these weeds can become unmanageable if forage species are stressed above normal such as prolonged drought periods. It should also be noted that today’s herbicides are so effective they can be used almost yearround. In Arkansas, a few warmer days can always be found during the colder months for herbicide application. Herbicides are cheap compared with other farm inputs.
Spraying dormant pastures a few times is cost-effective in the long run.
Complete elimination of certain weed species may not be possible, but populations can be kept below a certain threshold to avoid infestation during drought years. Pigweed – one of the most persistent weeds – can hardly be controlled once it reaches a plant height of 4 to 5 inches or higher. At that height, pigweed may not be visible among forage plants, so efforts should be made to scout it and control it early on. Always follow the recommendations on the herbicide label, and use the required application rates.
If clovers are present in pastures, herbicide options may be limited. In this case, it has to be evaluated whether or not the benefits of the clovers outweigh the disadvantages of having the hands tied when it comes to weed control. The utilization of annual legumes in perennial grass pastures may be less challenging than trying to keep perennial legumes in pastures year-round. Weeds can get out of control quickly in complex grassland ecosystems, so staying ahead of the game is important.