ESTABLISHMENT AND PERSISTENCE OF LEGUMES INTERSEEDED INTO SWITCHGRASS

Little information is available for renovation of established switchgr ass (Panicum virgatum L.) with cool-season forage legumes. Field exper iments were conducted to determine seeding success, persistence, and i mpact on grass when 10 forage legumes and a legume mixture were no-til l interseeded into established 'Cave-in-Rock' switchgrass near Ames, I A. Legumes interseeded in early April 1991 and 1992 were biennial 'Pol ara' white-flowered sweetclover (Melilotus alba Medik.) and 'B Madrid' yellow-flowered sweetclover (Melilotus officinalis Lam.), 'Norcen' an d 'Fergus' birdsfoot trefoil (Lotus corniculatus L.), 'Apollo Supreme' and 'Alfagraze' alfalfa (Medicago sativa L.), Mammoth and 'Redland II ' red clover (Trifolium pratense L.), 'Emerald' crownvetch (Coronilla varia L.), common hairy vetch (Vicia villosa Roth.), and a 50:50 mixtu re of Norcen trefoil and medium red clover. Legume renovation was comp ared with grass fertilized with N at 0, 60, 120 and 240 kg ha(-1). Exc ellent legume establishment was observed in June, about 2.5 mo after i nterseedings, with mean legume plant density of 195 and 163 plants m(- 2) for 1991 and 1992 seedings, respectively. Both alfalfa cultivars an d hairy vetch had highest percentage establishment. Average legume per sistence to June of the second year was nearly 50% for 1991 and 30% fo r 1992 seedings (less in 1992 because of greater winter losses). Grass stem density during the establishment year was not affected by legume renovation. Decline in grass stems during the second gear was greates t for trefoil and the trefoil-red clover mixture, and intermediate for alfalfa and red clover, with minimal to no effect for the sweetclover s, crownvetch, and hairy vetch. Hence, legumes can be successfully est ablished into switchgrass and can be maintained into the second year.