Fall is one of the most crucial time periods for our cool season pastures. The most important activity a livestock producer should be doing to help the pastures survive winter and remain productive next year is to avoid overgrazing.
Why is fall a critical time for our cool season perennial forages? The grass plants in your pasture are perennial plants. They survive from year to year.
One way perennial plants survive is to develop buds located at the crown of the plant and store energy in the form of carbohydrates to be used by those buds when they start growing next spring.
Leaf tissue that grows in the fall will die over winter. Next year’s growth comes from the buds developed the previous fall. The buds and roots of the plant are the parts that remain as living tissues over the winter.
While not growing they are respiring and burning energy. If carbohydrate reserves are not adequate then the plant can die before spring. If the plant survives but carbohydrate reserves are low, then initial spring growth is slow and the overall vigor of the plant is reduced.
In the fall, we have short day, long night periods with temperatures above freezing to about 70 degrees Fahrenheit. It is that combination that triggers buds to be initiated and formed on the crown of the plant.
In the cooler temperatures leaf growth is slower while photosynthesis does not slow down. This increases the reserve carbohydrates in the plant, which is then used for bud and root development.
In the spring, new growth comes from these buds. Initial spring growth draws upon carbohydrate reserves stored in the roots and or crowns of the plants. Those buds and stored carbohydrates are next year’s growth.
Healthy leaf tissue is needed for this to happen. Overgrazing removes too much leaf tissue. A grass plant with too little leaf area after grazing has to use carbohydrate reserves from the roots to re-grow.
If the plant does not grow enough leaf tissue to gain carbohydrates before it is grazed again then the plant will continue to deplete its carbohydrate reserves.
In fall, the growing season will eventually come to an end and the plant will not have a chance to recover. Plants struggling to grow leaves will not develop buds.
Overgrazed pastures that go into the winter with low carbohydrate reserves are very slow to green up in the spring and exhibit slow growth rates once they do green up.
Overgrazing is not caused by having too many animals in a field. It occurs when you keep animals in a field too long or bring the animals back before the forages have recovered.
The length of time is determined by plant growth and how much is there at the start of grazing. The animals should be removed before plants they initially grazed start to re-grow. They also should be removed before they eat all of the leaves.
Viable leaves need to remain after the plants are grazed. Plants should also be given enough rest between grazing events. This will allow enough leaf area to be re-grown before the animals are allowed to graze that field again.
Overgrazing can be avoided by paying attention to forage residual, grazing time and rest. You should leave at least 1,200-1,500 pounds of DM per acre or 2-3_ of green forage when you pull animals from a field. You should remove the animals before the forage starts to re-grow.
The pasture should recover to above 2,400 pounds of DM acre or 6-8_ before turning the animals into a field.
Another fall activity for pasture management is fertilizing. You can help your pastures by fertilizing. If you only fertilize your pastures once a year you should be doing it in the fall.
You have a fairly large window to accomplish this with the months of September through November. Fall is an excellent time to apply fertilizer to our pastures. Fall is the time when most of our forage plants are growing roots, developing tillers and storing energy for winter.
Proper soil pH and adequate soil nutrients will enhance forage competitiveness. Take a soil test and follow the recommendations.
Nitrogen can be applied in fall. Late fall applications of nitrogen, from October through November, will increase grass tillering, root growth and energy storage. This will help with spring green-up and improve competition against weeds.
Apply after grass growth has slowed, but before the plant has gone dormant. Use a low rate of 30 to 40 pounds of N per acre.
A pasture with good grazing management and with good soil fertility should out-compete weeds. This is the main reason I don’t spend a lot of time talking weed control.
Occasionally we still have problems. For some of our biennial and perennial weeds fall can be an excellent time to apply herbicide. A few weeds that come to mind include wild turnip/birdsrape mustard, Canada thistle, wild carrot and poison hemlock.
A few cautions: all of the broadleaf herbicides that can be used will also remove the legumes and there can be grazing restrictions depending on the herbicide and type of livestock. Check the 2009 Weed Control Guide or call your local Extension Office for specific recommendations.
Legume removal is the other reason I don’t usually mention herbicides. Legumes in pastures are desirable. Having 30-40 percent clover, on a dry weight basis, in your pastures will help reduce you nitrogen needs, fill in growth during summer and provide a higher quality feed for your livestock.
Avoiding overgrazing, applying needed fertilizer and controlling problem weeds are the three main pasture management activities producers should practice. These fall activities should make your pastures more productive next spring.