Lolium perenne populations effects on nitrogen concentration, use and uptake efficiency when grown on peat

Grass nitrogen (N) concentrations of dairy grasslands are higher on peat soil than on mineral soils. This can lead to increased N losses from dairy farming systems on peat soils. Our objective was to determine whether perennial ryegrass (Lolium perenne L.) populations with different shoot tissue N concentrations, recorded on a sandy soil, would show different shoot tissue N concentrations and N use efficiencies (NUE) or N uptake efficiencies (NUptE) when grown on a peat soil. A pot experiment lasting 62 days was carried out with nine diploid and seven tetraploid populations, followed by a field experiment with two diploid and two tetraploid populations and a control lasting 30 months. In the pot experiment, shoot tissue N concentrations differed among tetraploid populations, the NUE differed among diploid and tetraploid populations and the NUptE differed among diploid populations. In the field experiment, two populations had a 1.4 g kg^–1 lower shoot tissue N concentration compared to a commercial control, after ten harvests and at a N fertilisation level of 25 g m^–2 year^–1. We conclude that it is possible to alter shoot tissue N concentrations of perennial ryegrass grown on peat soil via the selection of low-N populations.