It’s more economical to interseed conventional than Roundup Ready alfalfa into existing bermudagrass pastures, according to a one-year Mississippi State University (MSU) study. The practice of interseeding the legume into bermudagrass for haying and grazing has been gaining notice across the South.

This study was to see if Roundup Ready alfalfa could improve forage quality with minimum fertility input.

In the fall of 2011, one main plot was minimum-tilled using a disk slightly lowered to scratch the soil; the other plot was no-tilled. Subplots of two Roundup Ready alfalfas were planted at 15, 20, 25 and 35 lbs/acre, with potassium the only nutrient added. Subplots of those subplots received glyphosate treatments.

“We didn’t see any differences in the tillage method. If you have a no-till drill, I would just use that,” says Joshua White, an MSU forage variety testing manager conducting the research with Rocky Lemus, Extension forage specialist.

The two highest seeding rates had a 6% seasonal yield increase, but not significantly more than the lower rates, probably due to bermudagrass making up the yield difference in the lower seeding rates. But higher seeding rates led to increased alfalfa composition and subsequently higher nutritional quality throughout the season.

A ½-pint/acre rate of glyphosate was applied over the top of the transgenic alfalfa in spring, while bermudagrass was dormant, to clean up weeds. A second application was made on half the plots later in spring to suppress bermudagrass.

“But one of the things we found was that alfalfa is so aggressive early on that we don’t really need to suppress bermudagrass with the second application,” he says. And, by suppressing bermudagrass competition, crabgrass and other weeds fought the alfalfa.