The Effects of Land-Use Change from Grassland to <i>Miscanthus x giganteus </i>on Soil N₂O Emissions

A one year field trial was carried out on three adjacent unfertilised plots; an 18 year old grassland, a 14 year old established <i>Miscanthus</i> crop, and a 7 month old newly planted <i>Miscanthus</i> crop. Measurements of N₂O, soil temperature, water filled pore space (WFPS), and inorganic nitrogen concentrations, were made every one to two weeks. Soil temperature, WFPS and NO₃⁻ and NH₄⁺ concentrations were all found to be significantly affected by land use. Temporal crop effects were also observed in soil inorganic nitrogen dynamics, due in part to C₄ litter incorporation into the soil under <i>Miscanthus</i>. Nonetheless, soil N₂O fluxes were not significantly affected by land use. Cumulative yearly N₂O fluxes were relatively low, 216 ± 163, 613 ± 294, and 377 ± 132 g·N·ha⁻¹·yr⁻¹ from the grassland, newly planted <i>Miscanthus</i>, and established <i>Miscanthus</i> plots respectively, and fell within the range commonly observed for unfertilised grasslands dominated by perennial ryegrass (<i>Lolium perenne</i>). Higher mean cumulative fluxes were measured in the newly planted <i>Miscanthus</i>, which may be linked to a possible unobserved increase immediately after establishment. However, these differences were not statistically significant. Based on the results of this experiment, land-use change from grassland to <i>Miscanthus</i> will have a neutral impact on medium to long-term N₂O emissions.