The nitrogen fixing and nutritional benefits of including white clover in a pasture are well documented. However, where attempts have been made to increase herbage yield by the application of fertilizer nitrogen, only the grass component of the mixture is stimulated. The white clover is placed at a competitive disadvantage for other aspects of the environment, especially light, and is adversely affected.

In many practical grazing systems, where defoliation is continuous rather than intermittent, it might be possible to maintain the crop canopy at a level where shading is unimportant. Similarly, if modest amounts of fertilizer nitrogen are applied when clover is least likely to be affected, the adverse effects may be minimized. Thus, the objectives of this study are to examine the extent to which fertilizer nitrogen can be used to improve animal production from a grass/clover sward by increasing herbage production whilst maintaining an effective clover population.