Earthworm impact on the global warming potential of a no-tillage arable soil.

We studied the effect of the deep-burrowing earthworm Lumbricus terrestris on the greenhouse gas (GHG) fluxes and global warming potential (GWP) of arable no-till soil using both field measurements and a controlled 15 week laboratory experiment. In the field, the emissions of nitrous oxide (N₂O) and carbon dioxide (CO₂) were on average 43 and 32% higher in areas occupied by L. terrestris (the presence judged by the surface midden) than in adjacent, unoccupied areas (with no midden). The fluxes of methane (CH₄) were variable and had no consistent difference between the midden and non-midden areas. Removing the midden did not affect soil N₂O and CO₂ emissions. The laboratory results were consistent with the field observations in that the emissions of N₂O and CO₂ were on average 27 and 13% higher in mesocosms with than without L. terrestris. Higher emissions of N₂O were most likely due to the higher content of mineral nitrogen and soil moisture under the middens, whereas L. terrestris respiration fully explained the observed increase in CO₂ emissions. The activity of L. terrestris increased the GWP of field and laboratory soil by 50 and 18%, but only 6 and 2% of this increase was due to the enhanced N₂O emission. Our results suggest that high N₂O emissions commonly observed in no-tillage soils can partly be explained by the abundance of L. terrestris under no-till management and that L. terrestris can markedly regulate the climatic effects of different cultivation practises. [ABSTRACT FROM AUTHOR]