THE EFFECT OF CUTTING AND INTENSIVE GRAZING MANAGEMENTS ON SWARD COMPONENTS OF CONTRASTING RYEGRASS AND WHITE CLOVER TYPES WHEN GROWN IN MIXTURES

A field experiment was established at the Institute of Grassland and E nvironmental Research (IGER), Aberystwyth, to compare the seasonal gro wth and annual yields of two white clovers when grown with each of fiv e perennial ryegrasses. Swards were subjected to two contrasting defol iation managements, namely cutting only and continuous grazing with sh eep. In addition to data recorded on dry matter yields of the swards, the effect of management on growth and development of white clover sto lons and tillering of ryegrasses was also studied in the third harvest year. The management of the swards had a significant effect on ryegra ss tiller number and on the ingress of weed grasses. Differences in pe rsistency and tillering among the ryegrasses were significantly greate r when continuously grazed by sheep than when swards were cut. It is a rgued that ingress of weed grasses under grazing could be used as an i ndicator of ryegrass persistency. Among those studied, only two of the ryegrasses were able to provide dense persistent swards under continu ous sheep grazing. The white clovers included in this experiment diffe red in leaf size with Gwenda smaller than Ac 3785. Greater differences existed between white clover components when grazed than when under c utting management. Under continuous sheep grazing there were large dif ferences between the clover varieties in stolen length, stolen weight, number of growing points and root weight. The data indicate the impor tance of the persistence of mixture components under continuous sheep grazing and, since ryegrass is the main component of a clover/grass se ed mixture, greater emphasis in breeding and evaluation programmes sho uld be given to persistence, especially under grazing.