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Be Careful to Manage Interseeded Winter Annual Grasses for Warm Season Grass Growth

February 21, 2013

By: Paul Beck, Professor – Animal Science


Over the past few years of drought, short hay supplies, and high feed prices; we have been recommending that producers interseed cool-season annual grasses (such as wheat, rye, and ryegrass) into warm-season grass pastures. By doing this producers are able to graze these pastures for 9 or 10 months instead of the 4 to 5 months of grazing we normally expect from pastures containing only warm-season grasses. For example, last fall we were able to interseed rye and ryegrass into pastures containing a mix of bermudagrass and crabgrass in mid to late October (when the Bermuda and crabgrasses regrowth slowed down). We then were able to graze stocker steers from mid-November to mid-February at a 1 steer per acre stocking rate. These steers gained 218 pounds or about 2.6 lbs per day! The steers were removed and replaced with a different set of calves in late February at a stocking rate of 2 steers per acre, the stocking rate was doubled because of extremely rapid spring forage growth that occurs from late February to May each spring. There are, however, several issues with this production system that can cause big problems if they are not controlled.


Everybody that has ever grown a garden knows that bermudagrass and crabgrass are very hardy plants and difficult to kill. One of the sure fire ways to kill bermudagrass is to smother it out. We can easily do this in pastures or hay meadows with our cool-season annuals if we are not careful. If allowed to grow uncontrolled late into the spring when warm-season grasses are breaking dormancy the cool-season grasses will out-compete the warm-season grasses for sunlight and nutrients. This will delay the growth of the warm-season grass or in severe cases reduce stand vigor or thin out warm-season pastures. Last year we had an early spring with warm conditions conducive for bermudagrass growth in April. The annual ryegrass was growing very rapidly at this time and where we were not able to graze it down or cut it for hay or silage in a timely fashion growth of the bermudagrass was delayed. In June it turned off hot and dry for 2 months and there was virtually no growth in these pastures (and hay meadows) until we started getting rain in August and September!


Because our cool-season forage crops have the slow growth in the fall and winter and rapid growth in the spring we are required to have a lower stocking rate in the fall than in the spring (as described above). So, if we are trying to graze a set number of cows or calves, we will need to plant more acres for fall use than we can possibly use during the spring. One way to reduce this problem is to only plant the number of acres we can graze during the spring, but that would require limit grazing or limiting the use of the cool-season forages in some way until spring growth occurs.


If we plant enough winter annuals to stock with our cattle in the fall and winter, then we may be able to adjust fertilizer levels to drive forage production for the times when we need more (fall) and put out less when we have more forage than we can use. Fertilizer is a good investment if we need or can use the additional forage it will produce; it is not worth its cost if the forage will not be used.


The best alternative may be to harvest the additional forage for hay or silage. If we have the equipment and are ready to roll when the time comes, wheat, rye, and ryegrass all make good hay and can be a valuable resource for wintering cattle later in the year. At the Southwest Research & Extension Center, the only way we were able to make it through the last couple of winters was because we were able to cut the additional cool-season grass growth for hay and silage. In one year the cool-season forages we preserved was the only crop we were able to bale.


Cool-season grasses can be a detriment to our warm-season pastures and hay meadows, delaying our first warm-season hay cutting or delaying summer grazing. But, with proper management these effects can be lessened and total forage production will be greater than if we managed for warm-season grasses alone.



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