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Can Legumes and Perennial Grasses Be Grown Together?

Posted Jan. 1, 2008

With the increasing cost of inputs (fuel, feed, fertilizer, etc.), many producers are looking for ways to cut costs while still maintaining yield (net return, forage biomass and forage quality). The most economical forage system will have a diverse set of species to provide high quality forage throughout the entire year (warm-season and cool-season perennial forages) to reduce the need for hay and feed (Figure 1). Traditional grass systems (bermudagrass and tall fescue) will be the most important components of any forage system, but, if legumes could be incorporated, then these systems could be more sustainable and economical.

Within the Agricultural and Forage Improvement divisions at the Noble Research Institute, sustainable forage systems are being evaluated over a wide geographic area (20- to 50-inch rainfall zones). Legumes are typically site-specific and not adapted over a wide geographic region, therefore many different legumes are being evaluated as a means to maintain high nutritive value, improve seasonal distribution and reduce the need for nitrogen fertilizer. For example, annual cool-season legumes like hairy vetch, medics and clovers are being evaluated in annual rye/ryegrass as well as perennial warm-season (switchgrass and bermudagrass) and perennial cool-season (tall fescue) systems. Perennial legumes like white clover and alfalfa are also being evaluated in perennial grass systems.

It would be nice if the environment in southern Oklahoma and north Texas would allow rich species diversity and cool-season and warm-season annuals, and perennials all to be grown together to provide year-round grazing with no forage deficits (Figure 1), but this has been impossible. Therefore, several experiments are being conducted to look at the compatibility between annual and perennial legumes in grass systems. Even after establishment of grass-legume mixtures with the same seasonal production, it is extremely difficult to manage these mixtures because cattle typically graze the higher quality legume and not the grass, especially in bermudagrass. However, utilizing legumes with different seasonality (e.g., vetch in bermudagrass or alfalfa in tall fescue), it may be easier to manage since cattle would not be grazing the grass in the off-season when forage quality is lower.

One study in particular seems to have potential (alfalfa-tall fescue row orientation). Tall fescue and alfalfa mixtures are difficult to establish; however, by planting alternating rows or even alternating drill passes, both species were successfully established (Photo 1) and may persist over time (Photo 2), but it is still unclear how long these might persist together under grazing. This research is being repeated in three geographic regions (25-, 30- and 35-inch rainfall zones - from Vernon, Texas, to Ardmore, Okla.) and will continually be monitored to see if these two important forages can be managed together under grazing to provide better seasonal production, improved forage quality and increased yield.