These data were collected during a laboratory incubation in order to study the specific contribution of roots and other below ground plant residues to N2O emissions after ploughing of temporary grassland (see article "Low N2O emissions induced by root-derived residues compared to aboveground residues of red clover or grass mixed into soil" in related publications). This incubation study is a supplement to the field study presented in the research article "Roots and other residues from leys with or without red clover: quality and effects on N2O Emission Factor after ploughing" and the dataset "Replicate data on Biomass and quality of ley roots and other plant residues - and associated N2O, CO2 and CH4 emissions and soil air composition after ploughing (see related publications) and a previous dataset (see related datasets). The dataset contains replicate data of nitrous oxide and carbon dioxide emissions from below ground (roots +crown) (BGR) and above ground (stubble or herbage) (AGR) plant residues of red clover and of a mixture of forage grasses mixed in the soil. Also replicate data of N2O-N and CO2-N emissions factors (EF: Additional N2O-N caused by a residue divided by the amount of N in the residue) over the incubation period are provided for below ground and above ground residues separately. Oxygen and methane consumption data are also provided, along with soil mineral N. The specific purpose of this experiment was to isolate the effect of BGR from that of AGR, in particularly from the effect of stubble left below cutting height (typically around 5 cm) after harvest. The data are well suited for further use, as for example refinement of models of plant litter decomposition and N cycling in the soil, including modelling of N2O emissions from plant residues and movement of mineral N in the soil.