By Rory Lewandowski, Extension Educator, Athens County, Buckeye Hills EERA
I’ve gotten some questions recently about pasture management during dry fall conditions. Specifically, how will future pasture production be affected by grazing off pasture leaf area now, in the fall? The short answer to that question is that pasture production will be harmed by grazing off leaf area at this time. Now, let’s examine the reasons behind the answer and some management options.
Fall is the time when the perennial plant prepares for winter. As a perennial plant, the root system remains alive over the winter and depends upon stored carbohydrate reserves to survive and to regenerate new growth the following spring. Manufacture of those carbohydrate reserves depends upon photosynthesis. Photosynthesis depends upon leaves capturing sunlight. More leaf area equals more sunlight captured, higher photosynthetic rates and higher levels of carbohydrates produced for winter storage. As we go farther into the fall, grass growth rate slows down considerably, but photosynthesis can still occur at productive rates, provided there is adequate leaf area.
Graziers should avoid the situation where a grass plant is grazed off low with little or no residual leaf area in the fall of the year. In this situation there may be enough growing season left for the plant to pull out root reserves to start growing new leaves, but not enough growing season left to get enough leaf area to replenish the reserves.
The plant ends up in a weakened state to go through the winter and can be slow to green up the following spring. In some cases, the plant may loose root volume over the winter and plant productivity can be decreased well into the next growing season. Weakened grass plants open the stand up to invasion by weeds and pasture quality suffers.
The grazing goal in the fall period is to manage pastures to leave at least a 4-inch leaf residual growth so that plants continue to stay in positive carbohydrate balance and continue to photosynthesize. If pastures can’t be managed in this way, then an option is to utilize a sacrifice lot, a pasture paddock that gets overgrazed, and feed hay in this lot rather than letting all pasture paddocks become overgrazed.
I’ve been asked if there is ever a time when pasture leaf area can be grazed off. Yes, once the plant is truly dormant and leaf growth has ceased for the year. This generally occurs when daytime temperatures average around 40 degrees F and after several nights of temperatures around 25 degrees F. At this point, leaf tissue is not going to re-grow. New growth will come from new shoots arising from the roots in the spring of the year. At this point, that leaf tissue can be completely grazed off. This is basically the idea behind stockpiling and what makes that system work.
Well-managed pastures are an important financial resource and they must be protected in the fall of the year. This is the time to use some of the abundant hay that was produced earlier this year.