Promoting Even Grazing
This concept goes along with removing the seed heads and resetting the forages back to vegetative growth, as doing so can also promote a more even grazing distribution by livestock. Particularly if livestock have already been grazing selectively, mowing or clipping can eliminate forages that are heading and lower in quality and prevent the underutilized areas from becoming overly mature. By evening out the pasture, promoting uniform regrowth, and keeping the forage in a vegetative growth state, you can help minimize selection by livestock.
This is especially true for continuously grazed pasture where livestock have the ability to be more selective. For rotational grazing systems with frequent rotations, you may find this less necessary. With smaller paddocks and more frequent moves, livestock will already be less selective about what they eat and paddocks are more likely to be grazed more evenly. Although this requires additional management, the return on this is less clipping, and less fuel and time spent doing so. So is the mowing worth it? In the long run, improving your management with rotation, adequate rest, and appropriate stocking rates will likely be more viable than continuously clipping underutilized areas.
Providing Weed Control
Mowing is often listed as a cheap, easy way to control weeds. Recognizing that there is a huge range in tolerance for weeds, particularly in pasture, most producers can probably still agree that certain weeds are more problematic than others and that some do have a negative impact on forage production and can lower the ability of the pasture to meet the nutritional needs of livestock. Mowing pastures is a form of mechanical weed control, and there are times when mowing or clipping can be useful, particularly if you have pastures with heavy weed pressure. In these cases, mowing can help eliminate competing vegetation and open up the canopy to favor the growth of desirable forages. Although mowing itself will not immediately control weeds or brush, it can prevent weeds from going to seed and help control their growth over time.
Of course the type of weeds present is an important consideration. Weed response to mowing will vary based on the time of clipping and the weed species present. Consider a pasture with an abundance of annual weeds. While mowing might help with their control in the short term, the presence of these weeds might be indicative of poor cover providing an opportunity for these species to fill in, in which case maintaining better cover would be a better focus for more success long term. For those harder-to-eliminate perennial weeds, although mowing may not be killing them outright, every time the plant is mowed it has to use additional energy for regrowth, draining its energy reserves and weakening the plant over time.
On the flip side, when considering mowing as a weed control strategy, be sure not to overlook the hidden costs. Factoring in time, along with fuel, maintenance, depreciation, and storage of equipment, most agricultural economists will place a minimum cost of $15 per acre on mowing. That’s really not all that cheap, especially when the results may be more temporary. It’s not that mowing can’t help control weeds, it’s that the number of mowings and the timeliness of each mowing are critical for long-term control. Effective control may require mowing two to three times each season over two or more years in order to fully prevent seed production and exhaust plant energy reserves. If we use the $15 per acre minimum, then we’ve spent $60 to $90 or more per acre for weed control.
In addition to the cost, recognize that mowing also removes some desired forage. Depending on the forage species and density, each inch of forage that is cut may remove 75 to 400 pounds of grazeable dry matter per acre. While mowing forage stands that have slowed or stopped growing can promote new, high-quality regrowth, mowing repeatedly over the season to suppress weeds will also reduce total available forage to some extent.
Controlling Pink Eye
Mowing or clipping can be a strategy to help control pink eye in cattle. While forage seed heads themselves do not necessarily cause pink eye, they can definitely be an irritant and aggravate the situation. However, you may have a hard time justifying mowing for this reason unless you have an active pink eye problem. If pink eye is presently an issue, keeping seed heads under control using clipping or mowing could be justified to reduce possible eye irritations. However, that is usually only the case with high amounts of seed heads present, and controlling flies should be the first priority.
If aesthetics is your primary reason for mowing or clipping, the reality is you might be better off leaving it alone. Taller forages produce more live roots, which can help provide some drought resilience. They can also help keep the canopy closed, shading out some weeds and keeping soil surface temperatures cooler and wetter, which can promote more growth from cool-season forages. They also have the added benefit of providing some wildlife habitat, especially for certain pollinator species. Pastures were never meant to look like mowed lawns, and keeping them as such is an added cost that has to be paid for by the enterprise.
All things considered, what is your primary reason for mowing? If your reason is to improve or maintain quality or to get on top of some persistent weed issues then you may find it useful. Mowing or clipping is one of the many tools we have for pasture management and it can have benefits so there is a time and a place for it. However, those benefits must be weighed against the costs that are associated with mowing pastures to determine if it is a practical expense economically. In some cases, mowing will have a low return on investment, and you may be better off focusing on other things and reducing the time and money spent mowing.
This article appears in the Maryland Milk Moo's June 2021 (Volume 2, Issue 2) and the Agronomy News June 2021 (Volume 12, Issue 3 ) newsletters.
Maryland Milk Moo's, June 2021, Vol.2, Issue 2
Maryland Milk Moos is a quarterly newsletter published by the University of Maryland Extension that focuses on dairy topics related to Nutrition and Production, Herd Management, and Forage Production. To subscribe to this newsletter, click the button below to enter your contact information.
Agronomy News, June 2021, Vol. 12, Issue 3
Agronomy News is a statewide newsletter for farmers, consultants, researchers and educators interested in grain and row crop forage production systems. This newsletter is published once a month during the growing season and will include topics pertinent to agronomic crop production. Subscribers will receive an email with the latest edition.