ABSTRACT
Forage legumes are playing an expanded and invaluable role in the nitrogen economy, in animal productivity and in sustainability of temperate grasslands, and advances in their technology are foreseen. The large pool of genetic variability among the genera and their species is being exploited further by the development of cultivars adapted to different edaphic, climatic and biotic conditions, though not forgetting the value of already adapted landraces. Some lesser species have shown promise as pioneer swards for difficult soils, degraded land and extreme climes, though sufficiency of certified seed supplies can be a problem. The N2-fixing capacity of forage legumes is discussed in terms of rhizobial efficiency, N transference to associated companion grasses, provision of on-farm protein, and N supply to subsequent arable crops. Individual animal performance is enhanced by high intake and nutritive value characteristics of legume-rich diets. Condensed tannins, present in certain legumes, e.g. birdsfoot trefoil (Lotus corniculatus), have benefited ruminant animal nutrition through protein protection and bloat prevention and reduction of internal parasites. Anti-quality factors associated with some legumes, e.g. oestrogens in red clover (Trifolium pratense), are also noted, together with preventative and control measures. Macro- and micro-economic aspects of forage legume use in grassland are dealt with briefly. Environmental issues, especially concerning nitrate leaching and emissions of ammonia and nitrous oxide, which are featuring more strongly in grassland farming, are addressed, as is the influence on legumes of global warming and accompanying elevated carbon dioxide in the atmosphere. Finally some alternative uses of legumes are noted.
