Review of factors determining legumes sod-seeding outcome during pasture renovation in North America

Pasture renovation entails introduction of desirable forage species, usually legumes such as red clover (Trifolium pratense L.), white clover (Trifolium repens L.) or birdsfoot trefoil (Lotus corniculatus L.), into a grass dominated pasture. A commonly used method of pasture renovation consists in drilling seeds into the grass sod (sod-seeding). Introduced legumes benefit the pasture in three ways. – They eliminate the need for application of costly nitrogen fertilizers, due to N2 fixation by the legumes and transfer of this fixed N to spatially associated grasses, resulting in increased production (Kunelius, 1982; Taylor, Allinson, 1983; Kunelius, Campbell, 1984; Koch et al., 1987; George et al., 1995; Vough et al., 1995) – They permit the stabilization of forage dry matter production throughout the year, due to differences in seasonal yield distribution between grass and legume species (Robinson, Winch, 1985). – They increase the quality of forage available to grazing animals (Taylor, Allinson, 1983; Kunelius, Campbell, 1984; Koch et al., 1987; Ocumpaugh, 1990). Although pasture renovation by sod-seeding is a method increasing in popularity, results reported are characterized by their great variability (Rioux, 1994a). As a consequence, factors affecting legume sod-seeding outcome warrant further discussion and investigation.