September 13, 2000

Attention to pastures in fall can mean more feed, better winter survival

Giving some attention to your pastures this fall can mean more feed for your grazing animals in the spring. Better forage plant survival through the winter is one of the main benefits of good fall pasture management, says Maribel Fernandez, Wright County educator with the University of Minnesota Extension Service.

"Photosynthesis in green leaves is the main mechanism plants use to produce nutrients," says Fernandez. "But in the spring, there are no leaves. Plants use the energy stored during the fall in the root crowns and the base of the stems to start re-growth."

Avoiding over-grazing and over-cutting in the fall helps plants store the energy they need, says Fernandez. Fertilization also enhances energy storage. Another fall pasture management job is controlling perennial weeds from the root. Weeds follow the same biological clock as pasture forage plants and move nutrients into their roots during the fall to get ready for winter. Chemical control can be very efficient at this time.

Fernandez has the following recommendations for fall pasture management:

--Fertilize. Apply nitrogen in the fall right after the last grazing or cutting. This will help plants get ready for winter. Inorganic fertilizers will be used most efficiently when the soil is wet. Applying manure is also an excellent way to provide nutrients. However, dry weather right after manure or fertilizer application will result in nitrogen loss through evaporation. Excessive rain, on the other hand, can cause nitrogen leaching to groundwater or phosphorus runoff. Leaching and runoff are likely to be more severe when there is little pasture cover. Compost can act as a "slow-release" fertilizer that prevents nutrient leaching and improves soil structure.

--Avoid over-grazing. Leave at least a four-inch stubble at the end of the grazing season. It is also good to stop grazing at least 30 days before the first hard freeze. This gives plants a chance to grow and store energy. After the plants and the ground are frozen, you can put the animals back on the pasture.

--Control weeds. The three broad categories of weeds are annuals, biennials, and perennials. Perennials are very hard to control because they grow back from the same root every year. The way to eliminate perennials is to attack the root. Cutting or applying herbicides in the spring or summer will get rid of the part of the plant that is above the ground, but a new plant will start growing from the root.

Herbicides applied in the fall will be transported to the roots and kill weeds from the roots. This has to be done while the leaves and stems are still active, so the best time is late summer or early fall. Grazing and haying restrictions apply, depending on the kind of herbicide and the kind of animals grazing the pasture. The publication "Cultural and Chemical Weed Control in Field Crops 2000," BU-3157, has a current list of approved herbicides and their restrictions. The publication is available for purchase from county offices of the U of M Extension Service or by calling (800) 876-8636.

While waiting for the right time to apply herbicides, avoid getting new weed seeds on the ground. Cut off flower heads before they develop into ripe seed heads. Depending on the severity of weed infestations, some people use scissors, a weed whacker, or a mower. If you cut the weed close to the ground, plan in advance so that a new plant will develop by early fall. This will provide some active leaves that will transport the herbicide to the root.

Unfortunately, you can be sure there are old seeds on the ground that will start a new generation of weeds. The good news is new perennial plants can be treated as annuals because their roots are just developing. You can control the new perennials by mowing or applying herbicides when they are in the flower stage in the spring.

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Source:  Maribel Fernandez, (612) 682-7394
Editor:   Joseph Kurtz, (612) 625-3168, jk@umn.edu

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URL: http:// www.extension.umn.edu/extensionnews/2000/AttentionToPasuresInFall.html  This page was updated May 21, 2002 .
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