The Effects of Land-Use Change from Grassland to Miscanthus x giganteus 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 Miscanthus crop, and a 7 month old newly planted Miscanthus 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 Miscanthus. 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·yr from the grassland, newly planted Miscanthus, and established Miscanthus plots respectively, and fell within the range commonly observed for unfertilised grasslands dominated by perennial ryegrass (Lolium perenne). Higher mean cumulative fluxes were measured in the newly planted Miscanthus, 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 Miscanthus will have a neutral impact on medium to long-term N2O emissions.