Managing Roundup Ready® Alfalfa Interseeded Into a Bermudagrass Stand in Mississippi.

Alfalfa is well adapted in many hay systems across the United States and has persisted in grazing situations under adequate rainfall and well-drained soils. In high precipitation regions like the southeastern U.S., lack of moisture is usually not a limitation in forage systems which coupled with mild winters can prolong the grazing season.  In Mississippi, fertility issues often decrease profits of forage systems because of the high input needed to maintain quality hay and pastures of warm-season perennial grasses such as bermudagrass. Roundup Ready^® alfalfa can possibly be interseeded into existing pastures and consequently prolong the growing season and improve forage quality with minimum fertility input. The study was a split-split plot design replicated 4 times.  Main plots were two tillage systems (minimum tillage and no-tillage), subplots were variety x seeding rate and sub-subplots were herbicide treatments (glyphosate or no herbicide). Two Roundup Ready^® alfalfa varieties DKA41-18RR and DKA65-10RR were planted at a rate of 17, 22, 28 and 39 kg ha^-1 in the fall of 2011. Sup-subplots receiving the herbicide treatment were sprayed with glyphosate at a rate of 0.6 L ha^-1. Potash was applied according to the soil with no other fertility adjustments or nitrogen applications. The April harvest was significantly affected by seeding rates with 39 and 28 Kg ha^-1 producing the greatest forage yields; however the May and August harvests were not affected. The two higher seeding rates had a 6% increase in seasonal yield but not significant that the other rates.  Alfalfa composition in the stand was greatest at the 39 kg ha^-1 seeding rate and lower at the 17 kg ha^-1.  Percent alfalfa in the stand decreased up to 41% between the May and August harvest.  After April, bermudagrass contributed to more uniform forage yields in the lower alfalfa seeding rates.