Brookings Register

By: Sara Bauder, South Dakota Extension forage field specialist

Updated: 22 hours ago / Posted Aug 30, 2023

Fall range management is easily overlooked as the pressure of cutting silage and harvesting grain add to the load on many farms. Fall pasture growth is often a great way to extend the grazing season, but careful management is required to ensure that fall grazing isn’t harmful to the following spring’s forage crop.

During the fall, perennial cool-season range plants start developing new shoots and regenerate roots. Carbohydrates are stored in the plant in order to help rebuild roots and provide stores for winter survival. Most of these carbohydrates are stored within the crown root which sits in the lower 3-4 inches of the plant in many perennial grasses.

This means, it’s important to avoid overgrazing, and make sure you are leaving at least 3-4 inches of stubble height in the fall (or anytime during the year). Best management practices would actually suggest moving livestock as soon as grasses reach 6 inch or less to keep rangeland healthy and soils well covered.

Early fall/late summer is also a great time to apply fertilizer to rangeland (especially cool-season grasses). Best practice is to take soil samples from each respective pasture (for a guide on how to take samples visit https://extension.sdstate.edu/recommended-soil-sampling-methods-and-instructions) and send them to your lab of choice for macronutrient testing. Once results are received, application rates can be determined using the SDSU Fertilizer Recommendations Guide found at https://extension.sdstate.edu/fertilizer-recommendation-guide.

Grasses typically respond well to N application, but adequate P and K levels should be met to ensure overall plant health. The SDSU Fertilizer Recommendations Guide suggests 25 pounds of Nitrogen per 1 ton of grass yield goal. If you are unsure of your pasture production, you can attempt to measure it for future seasons by taking grass clippings in a known, ungrazed area (where all other management takes place as it normally would). Specific recommendations on P, K and other nutrients can be found in the SDSU “Fertilizer Recommendations Guide” located at our website, extension.sdstate.edu. Should drought conditions become an issue after application or into the spring, it’s always important to watch grasses for nitrate accumulation and possible toxicity- tissue testing is recommended if concerns arise.

While we’re talking about forage, late alfalfa cuttings come to mind. Each corner of the state has experienced some unique weather patterns this year, mostly independent of one another. This means alfalfa cutting timings and yields are all over the board! Yet, every year many growers find themselves struggling to determine when to take that last cutting of hay. Fall harvest should be determined by a few factors.

• The first thing to consider is that alfalfa needs 500 alfalfa growing degree days (GDDs) after cutting and before a hard freeze to get enough root reserves to survive most Midwest winters (calculate your GDDs at https://climate.sdstate.edu/tools/degreedays/). This equates to about six weeks in the Upper Midwest. By determining your long-term average hard frost (24°F) date (see https://climate.sdstate.edu/tools/et/) and working backwards 6 weeks, you should have a pretty good idea of last suggested cutting date.

• If you have a newly established stand of spring seeded alfalfa that experienced favorable weather conditions and looks well established, an October cutting may be appropriate as long as ~500 GDDs have accumulated since your last cutting. Remember that late fall cuttings can result in a lower first spring cutting yield. If your young alfalfa stand did not experience a favorable growing season or was not established until late summer, avoid the last, late cutting.

• On the opposite side of the issue, keep in mind that it’s not ideal to let more than 200 alfalfa growing degree days accumulate AFTER you make the last cutting. After this much growth occurs, root reserves are fairly depleted and plants become more susceptible to winterkill.

• If you plan to terminate your stand in the spring, a later harvest is fine; however, terminating alfalfa with herbicides is best at 4+ inches of regrowth.

• If it gets late and you’re concerned about forage supply, consider harvesting after the winterization period; technically, it should be safe to take a cutting at this time. This correlates to cutting after a killing freeze (23-24°F for several hours) after the plant is dormant. This is not as stressful to the plants as cutting during winterization, and can be a viable option for those who need feed and do not want to risk next year’s stand.

Remember in any scenario, it’s ideal to leave 5-inches plus of stubble, which leaves some plant tissue and helps to reduce erosion. Leaving soils bare over winter is a recipe for erosion and will likely result in less snow cover with little plant residue on the soil surface.

The more stress an alfalfa stand sees during the growing season, the more apt it is to experience winter-kill after a late cutting. If a field was cut multiple times (4-plus), it is more likely to have winter-kill issues than those that were cut fewer times. Younger, well-established, winter hardy/disease-resistant varieties may tolerate a late season cutting better than older stands or those that experienced heavy pest pressure over the growing season.