Additive effects of earthworms, nitrogen-rich litter and elevated soil temperature on N2O emission and nitrate leaching from an arable soil

• Earthworms and soil elevated temperature additively increased N leaching from soil.
• Highest N2O emissions were found at elevated temperature with litter and earthworms.
• Litter, earthworms and elevated temperature differentially affected denitrification.

The future nicrease of soil temperatures will affect the activity of decomposer organisms, potentially enhancing element cycling and greenhouse gas (i.e. CO2 and N2O) emissions. In a three-factorial microcosm experiment, we investigated the effects of the incorporation of N-rich green manure litter (Phacelia tanacetifolia Benth.) into an arable soil, of the presence of endogeic earthworms and of elevated soil temperatures (+3.5 °C) on C and N cycling over a period of 42 days. Effects of litter addition were most pronounced. Litter strongly increased amounts of mineral and organic N in the leachate, soil extractable mineral and organic N and organic C, denitrification activity, CO2 and N2O emissions as well as earthworm biomass. Elevated soil temperatures also increased CO2 emissions, but this effect was more pronounced in treatments without litter. Furthermore, elevated soil temperature reduced the amounts of extractable organic C and NH4+, but increased amounts of NO3−, indicating enhanced nitrification activity in warmed soils. Earthworm presence increased NO3− leaching and this was more pronounced under elevated soil temperatures. N2O emissions were strongly increased by 70–90% by earthworm activity, with the highest emissions in the treatment with litter incorporation under elevated temperatures. This treatment also had the largest amount of NO3− leaching and the highest denitrification activities. Our results indicate an increasing risk for N losses in the form of nitrate leaching and/or N2O emissions from earthworm populated arable soils with a warmer climate in the future.