SUMMARYResidual nitrogen from white clover/ryegrass swards and ryegrass monocultures was quantified in terms of the barley yield obtained after ploughing the swards. Clover/ryegrass swards based on small and medium-leaved cultivars of white clover and ryegrass monocultures were grazed continuously by sheep for 3 years (1984–87) at the Welsh Plant Breeding Station, Aberystwyth, ploughed in the following spring (1988) and then sown with the spring barley cultivar Doublet. Yield of barley obtained after clover/ryegrass mixtures was 50% greater than barley harvested after ryegrass monocultures. Barley yield was 1·6 t/ha more following the white clover cultivars Gwenda and SI84 with ryegrass than following ryegrass monocultures.
N2-fixation and residual N effect of four legume species and four companion grass species