Establishment and Persistence of Legumes Interseeded into Switchgrass

Abstract

AbstractLittle information is available for renovation of established switch‐grass (Panicum virgatum L.) with cool‐season forage legumes. Field experiments were conducted to determine seeding success, persistence, and impact on grass when 10 forage legumes and a legume mixture were no‐till interseeded into established ‘Cave‐in‐Rock’ switchgrass near Ames, IA. Legumes interseeded in early April 1991 and 1992 were biennial ‘Polara’ white‐flowered sweetclover (Melilotus alba Medik.) and ‘Madrid’ yellow‐flowered sweetclover (‘Melilotus officinalis’ Lam.), ‘Norcen’ and ‘Fergus’ birdsfoot trefoil (Lotus corniculatus L.), ‘Apollo Supreme’ and ‘Alfagraze’ alfalfa (‘Medicago saliva’ 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 mixture of Norcen trefoil and medium red clover. Legume renovation was compared with grass fertilized with N at 0, 60, 120, and 240 kg ha−1. Excellent legume establishment was observed in June, about 2.5 mo after interseedings, with mean legume plant density of 195 and 163 plants m−2 for 1991 and 1992 seedings, respectively. Both alfalfa cultivars and hairy vetch had highest percentage establishment. Average legume persistence to June of the second year was nearly 50% for 1991 and 30% for 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 year was greatest for trefoil and the trefoil‐red clover mixture, and intermediate for alfalfa and red clover, with minimal to no effect for the sweetclovers, crownvetch, and hairy vetch. Hence, legumes can be successfully established into switchgrass and can be maintained into the second year