Underground transfer of nitrogen between pasture plants infected with vesicular‐arbuscular mycorrhizal fungi

SUMMARY Experiments were carried out to investigate the possibility that vesicular‐arbuscular (VA) mycorrhizal infection of grass ( Lolium perenne L.) and clover ( Trifolium repens L.) roots can enhance the exchange of nitrogen between the root systems of nitrogen‐fixing pasture legumes and associated grasses. The results showed higher rates of transfer of 15 N applied as ( 15 NH 4 ) 2 SO 4 to the clover plants to companion grass plants when the roots were mycorrhizal. In some cases but not all the grass grew better in the mycorrhizal treatments. An experiment in which the clover and grass roots were separated by a 60 μm (mean pore size) nylon mesh screen showed that translocation of the nitrogen was probably along the mycorrhizal hyphae. It was not clear from the data whether transfer was mediated by a common hyphal net or some other less direct means.