Forage yield and crude protein of interseeded legume-bermudagrass mixturesas affected by phosphorus fertilizer

Bermudagrass (Cynodon dactylon L.) is a warm season perennial that is well adapted in the southern Great Plains. It is one of the region's most import ant forage crops used for livestock production, and is commonly grown witho ut legume interseeding. Recent research has investigated ways of improving the quality and quantity of this forage. The objectives of this study were to determine the effect of interseeded legumes and phosphorus (P) fertilize r on bermudagrass pasture forage yield and crude protein content. One exper iment was initiated in 1993 in eastern Oklahoma in an established bermudagr ass pasture. Red clover (Trifolium pratense L.), ladino clover (Trifolium r epens L.), and two varieties of alfalfa (Medicago sativa L.), 'alfagraze' a nd 'common', were interseeded by hand into an established stand of bermudag rass. The effect of P on forage yield and crude protein was evaluated using a 30-kg P ha(-1) rate applied at establishment versus no applied P. Forage yield was collected three times throughout the growing season each year fr om 1994 through 1997. When both alfalfa varieties were interseeded into a b ermudagrass pasture without applying additional P fertilizer, forage yields for the legume-grass mixtures decreased below those obtained from the mono culture bermudagrass in the first year of the stand. The alfalfa variety 'a lfagraze' interseeded into established bermudagrass decreased total forage yield over the entire 4-yr study. Interseeded red clover and ladino clover increased crude protein of the forage compared with monoculture bermudagras s the first two years of the study, with red clover continuing to increase crude protein in the fourth year. However, when 30 kg P ha(-1) was applied to the bermudagrass prior to establishment of the legumes, no change in yie ld or protein was observed for both alfalfa varieties' interseeding treatme nts versus the unfertilized mixtures. Although forage yield may not be incr eased, interseeding legumes into established bermudagrass could provide an efficient way to improve pasture crude protein without the use of inorganic fertilizers. However, if alfalfa ('common' or 'alfagraze') is interseeded, additional P may need to be applied at legume establishment to prevent pos sible yield decreases.