October signals the coming end to our pasture-growing season. In some cases the growing season equals the grazing season. When pasture growth ends, so does the grazing.
However, for those graziers who have managed their pastures and watched over pasture health, the grazing season extends beyond the growing season.
Stockpiled grass continues to grow in preparation for late fall and winter grazing, brassica and cool season cereal crops planted in August are accumulating growth which will be grazed after the growing season ends.
Meanwhile, the rest of our cool season pastures continue to be grazed in this fall period. The grazier must continue to practice good management on these pastures.
While we tend to think of fall as bringing an end to pasture growth, it turns out this is a critical time for the grass plant.
In fact, for our perennial grass plants, fall is not so much an end as it is a beginning, or at least laying a foundation for a beginning.
Explanation
Let me explain. Fall is the time when the grass plant develops buds which will provide tiller growth next spring. Fall is the time when the grass plant strengthens its root system, rebuilding and regenerating roots.
Fall is the time when carbohydrate reserves are built up. All of this is necessary to insure the plant survives from one year to the next. It is the difference between an annual and a perennial plant.
All these things take place provided the grass plant has not been overgrazed and adequate leaf area has been maintained on the plant.
From a plant health standpoint, overgrazing during the fall is more detrimental to the plant compared to overgrazing followed by rest in the early part of the growing season.
Reason why
Here is the reason why. Early in the growing season environmental conditions are generally favorable for rapid growth.
Rapid growth means regenerating leaf area.
This allows the plant to quickly get to the point where photosynthesis replaces any storage carbohydrates that were used to start growth following defoliation and to then put excess carbohydrates toward further growth.
In the fall of the year, environmental conditions are not as favorable for rapid growth. We can’t count upon an overgrazed plant being able to generate a lot of leaf growth.
Physiologically, the plant growth response, the ability to put out new leaf material, is more sensitive to low temperature than photosynthesis.
In other words, even when plant growth might be very slow, if there is leaf area present, photosynthesis is taking place.
On a practical level this means since the plant growth rate is slowed the carbohydrates produced by photosynthesis during this time period accumulate in plant storage organs.
Carbohydrate reserves
This is exactly what the plant needs to survive the winter and produce new growth next spring. We sometimes use the term carbohydrate root reserves to make a distinction between carbohydrates used for growth and those used for storage.
Technically, our cool season grasses store the majority of carbohydrate reserves in stem and tiller bases, some in rhizomes and only a little in roots.
Regardless of the technicality, root vigor and volume is linked to leaf growth and vice versa.
However, this technicality does help us understand some management aspects of pasture grass and fall carbohydrate storage.
For example, orchardgrass stores carbohydrates in the lower three to four inches of stem bases and tillers.
Tall fescue and bluegrass both maintain carbohydrate storage at the base of tillers as well as rhizomes. Tall fescue and bluegrass can both tolerate lower grazing/clipping heights than orchardgrass.
Once we reach the fall period, it is critical grass plants be managed to insure adequate leaf area is left after a grazing pass.
Photosynthesis will provide the carbohydrates needed for winter storage, provided there is adequate leaf area.
Since leaf growth will be slow, this means leaving a typical grazing residual plus some extra. For orchardgrass this probably means 4 to 5 inches at minimum.
Tall fescue and bluegrass should probably be managed to leave a 3- to 4-inch residual.
The consequence
What is the consequence of not maintaining enough leaf area in the fall and overgrazing the plant? Last year’s drought provided us with the perfect example.
In Athens County, I saw pastures that were overgrazed in the fall very slow to green up and start growth in the spring.
I saw overgrazed pastures exhibit lower growth rates. Some pastures never got back to pre-drought productivity.
The next time you are tempted to pat yourself on the back when fall rolls around because you have successfully managed your pastures for yet another season, hold off a while longer. There is still important work to be done in the fall.
It’s not the end; it’s the beginning of next year’s grazing season.
