Some effects of added phosphorus on perennial ryegrass—white clover swards

Abstract The effect of applying 100kg P ha‐1 per year in the form of triple superphosphate to mixed swards of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) was examined on a soil of low P status. The dry matter yield of total herbage was increased by 10′/i by added P. In the year of sowing the ryegrass benefited more than the clover from added P: in the subsequent four years the two species benefited equally. Both species responded 10 added P to a similar extent in terms of leaf size; the clover responded less well than the ryegrass in terms of rate of leaf emergence. However, clover responded positively to added P in terms of stolon internode length, length of stolon per m2 and number of growing points per m2. It is suggested that the application of P may promote the spread of white clover within an open sward, but that its application may not enhance the competitive power of white clover when growing with vigorous grasses.