Monday, August 30, 2010

Pasture Management in the Fall

Rory Lewandowski, Extension Educator Athens County and Buckeye Hills EERA

The fall period, particularly the months of September and October, is an important time to manage pastures. Specifically, pastures must be managed to insure that the desirable grass and legume plants are able to build up and store carbohydrate reserves for the winter period. It is this ability to store carbohydrate reserves and thus keep a root system living over the winter months that distinguishes a perennial plant from an annual plant. It is during the short day, long night periods in the fall of the year that flower buds are formed/initiated on the crown of the plant. While the leaf tissue dies during the winter, the buds and roots of the plant remain as living tissues over the winter and continue to respire and burn energy. If root reserves are insufficient the plant may die over the winter. If the plant survives but root reserves are low, spring re-growth and vigor of the plant is reduced.

So, what is necessary for plants to build up these carbohydrate reserves? Simply put, there must be adequate leaf area so that the plant can maximize the photosynthetic process. Pastures must continue to be managed in the fall of the year so that they are not over grazed. We know that regrowth is slower in the fall of the year. Plant growth is more temperature sensitive than photosynthesis. This means that even if plant growth is very slow because of cool temperatures in the fall, if leaf area is present, photosynthesis is still taking place at a good rate. Therefore, the mistake of overgrazing is amplified in the fall of the year. Depending upon the severity of overgrazing, the plant may not regrow enough and develop enough leaf area to take advantage of sunshine and produce carbohydrates.

We often hear the term carbohydrate root reserves used when talking about winter storage. The root is the storage area of carbohydrates for plants with a taproot, including legumes like alfalfa and red clover. For white clover, the carbohydrate storage area is the stolen. 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. However, this technicality does help us to understand some management aspects of pasture grass and fall carbohydrate storage. For example, orchardgrass stores carbohydrates in the lower 3 to 4 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 that grass plants be managed to insure that 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 a minimum. Tall fescue and bluegrass should probably be managed to leave a 3 to 4 inch residual.

Pasture management in the fall of the year that insures there is adequate leaf area to allow plants to maximize photosynthesis and build carbohydrate reserves will pay off in quicker spring green up and more vigorous spring plant growth.