As stored forage supplies start to run low, more and more producers are turning their livestock out on pastures earlier than they would like. With this advanced start to the grazing season, it is crucial that pastures are allowed to rest and recover to maintain adequate forage production.
So, how much rest does a pasture need?
Victor Shelton, an Ohio NRCS (Natural Resources Conservation Service) agronomist and grazing specialist, provides answers to this question in a recent article published in the Ohio Beef Cattle Letter.
If a pasture is continuously grazed, it never gets a chance to rest. But if it’s divided into four paddocks with one paddock grazed at a time, 75 percent of the pasture is resting at any point in time; a 12-paddock system elevates the resting percentage to 94.
Shelton notes that the ideal amount of rest time depends on the time of year and growing conditions. Early in the growing season, when growth is rapid, resting time should be around 14 days. As growth starts to slow, resting time needs to extend to 30 days. Cool-season grasses benefit more from 45 to 60 day resting periods once summer heat and drier conditions set in.
Shelton offered this as a general rule of thumb: “Just remember when forages are growing fast, move animals fast, and when forages are growing slower, move animals slower.”
Once grazing has started, Shelton recommends continuing to graze around the system until the first paddock is ready. Any paddocks you chose to skip can be stockpiled for grazing later in the summer or made into hay. If a lack of rain causes growth to slow, those skipped paddocks can then be used for grazing when needed.
If you have tracked grazing over the past couple of years and know which paddocks are slower to recover, these can be skipped during the first rotation to provide some extra rest.
Shelton also advises against starting the grazing season in the same field each year. That first field is often grazed before conditions are ideal, which induces stress. This can lead to weed problems as well as reduced diversity of desired forages over time.
When it comes to residual grazing heights, Shelton aptly states, “It takes grass to grow grass!” Cattle need to be moved in a timely fashion to ensure an effective “solar panel” or leaf area is left in the paddock. Most tall, cool-season forages need at least 4 inches of height to effectively take advantage of photosynthesis for regrowth.
The amount of forage removed also impacts root health. Up to 50 percent of the plant can be removed with little to no impact on root growth. Beyond 50 percent, root growth slows drastically. Removing 70 percent forage or more stops root growth completely, which results in the need for a longer rest period.
Shelton explains that there is approximately the equivalent amount of live growth below ground as there is above ground. When we remove the leaf matter, the roots respond in a similar fashion since they rely on those leaves to supply sugar from photosynthesis. This is where the old rule of thumb of “take half, leave half” comes into play.
Live, healthy roots that result from a higher stop-grazing height can extend deeper in the soil to transport moisture and nutrients to the plant, which also makes it more drought tolerant.
To really drive the point home, Shelton concludes by stating, “How productive would you be if you worked 24/7 with no rest?”
Kassidy Buse was the 2018 Hay & Forage Grower summer editorial intern. She is from Bridgewater, S.D., and graduated from Iowa State University with a degree in animal science. Buse is currently attending the University of Nebraska-Lincoln pursuing a master’s degree in ruminant nutrition.