MANAGING WHITE CLOVER IN MIXED SWARDS PRINCIPLES AND PRACTICE

Resumen

The key to sustainable productivity from grass/white clover swards is the maintenance of a satisfactory clover content. This is not always easy given the dynamics of the grass/white clover association and the interaction of the components, particularly in light of the N fluxes. Nevertheless, considerable advances by researchers have been made, especially over the last 10-15 years, and management guidelines increasingly elucidated. The research findings leading up to these are examined and discussed below for both grazing and conservation forms of utilization. Emphasis is given to the vital role of the perennating stolon network and its reaction to the different interacting components (defoliation, trampling, excretal return) of the grazing process; the effeets of cutting intensity (severity and frequeney) are also considered, as is the advantage of a conservation cut in rejuvenating severely grazed swards. While as yet limited in number in Europe, systems studies exploiting the high nutritive valué of clover have proved practicable and economically viable for sheep, dairy and beef cattle production. Clover varietal types and companion grasses are also discussed in relation to their influence on clover persistence as are the effeets of different fertilizer nutrients. Environmental concerns are briefly touched upon, particularly in relation to minimising N losses, still a challenging topic for researchers. It is concluded that a flexible approach to management is necessary, i.e. applying specifíc management techniques or factors at specific times in response to seasonal effeets or to the effeets of previous management. Arguably farmers aecustomed to the straightforward use of N-fertilized grass swards require decisión support from advisory services; they in turn need support from researchers who have validated practical systems of animal production primarily based upon grass/white clover swards. It is predicted that their use will increase in the near future for various reasons including the political moves towards extensification, the requirement for increasingly environmentally-friendly farming systems and consumer demand for production systems perceived as being 'natural'