Overseeding Warm-Season Perennial Grasses with Cool-Season Forages1
Bermudagrass and bahiagrass make up the greatest portion of perennial warm-season pastures in Florida. They do not grow in cool weather and often furnish no forage for 4–6 months of the year.
Many livestock producers in North Florida overseed (or "interseed") cool-season forages in the warm-season pastures. Small grains (rye, oats, wheat, triticale) generally do not perform as well when overseeded as when planted into a prepared seedbed, but overseeded ryegrass and clovers can perform quite well.
Reducing vegetative cover is absolutely necessary for successful overseeding. Reducing competition makes it easier to get good seed-to-soil contact, which is necessary for germination and establishment. The most desirable way to reduce vegetation is through grazing, thus using the forage present. Other practices include burning, baling, herbicide application, or some combination.
The kind of grass present, plant being seeded, kind and number of livestock, and general experience of the operator all determine the planting methods used. Many types of drills are available that can penetrate the sod and place the seed at a desired depth. Often a light disking, followed by broadcasting the seed, and then use of a "drag," roller, or cultipacker gives good results. Seeds should preferably be covered, with the planting depth being determined by the species planted, but at least good seed-to-soil contact is necessary for good germination. The least amount of disturbance conserves the most soil moisture. Moisture is often the limiting factor in the fall period when overseeding is done; thus soil moisture conditions may determine planting date. As a general rule, overseeding should occur from October 15 to December 15 in northern peninsular Florida and November 15 to December 15 in South Florida. Cool-season forages are much less likely to be used in South Florida because of a shorter growing season and competition for moisture by the perennial grass. Overseeding could also open up sod for weed invasion in South Florida.
Soil-test results should be used to guide liming and fertilization decisions. Nitrogen rates are reduced when legumes are added to the mixture, and no nitrogen should be applied if legumes are seeded alone. After the cool-season legume matures, it furnishes some residual nitrogen to the warm-season perennial grass—often enough that no additional nitrogen fertilizer application is necessary on grazed pastures.
Quality of the cool-season forages is high, and the forages can be managed for most efficient use in a number of ways. Creep grazing, limit grazing, and rotational grazing are some ways to achieve greater efficiency. In addition to higher quality of both cool-season legumes and grasses, overseeding generally results in more total forage production per land unit. Because the overseeded species are growing when the warm-season grasses are dormant, the grazing season is longer. Also see the EDIS documents SS-AGR-84 Cool-Season Forage Variety Recommendations for Florida (https://edis.ifas.ufl.edu/aa266) and SS-AGR-43 Tillage and Overseeding Pastures for Winter Forage Production in North Florida (https://edis.ifas.ufl.edu/ag146).