Effects of Heterodera trifolii on the growth of clover in a yellow‐grey earth under greenhouse conditions

Five pot trials were carried out using sterilised soil, Heterodera trifolii cysts being added to half the pots in each triaL The response of white clover to added superphosphate (0, 100, 300, 1000 kg/ha) without lime, with 2500 kg/ha lime, and in a mixed sward with ryegrass indicated a reduction of 13–55% in dry‐matter production by white clover in the presence of H. trifolii . In the presence of H. trifolii substantial additions of superphosphate were required to give the same yield of white clover obtained with no added superphosphate in the absence of nematodes. The highest yield of ryegrass plus clover with H. trifolii was 50–60% of the yield of white clover grown alone. Reduction in dry‐matter production of white clover by H. trifolii at moisture tensions of 0.2, 1.0, 3.0, and 10.0 atmospheres was 39, 29, 40, and 16%, respectively, whereas production of subterranean clover was not significantly affected by H. trifolii , which cannot reproduce on it.