Temporal dynamics of earthworm-related macroporosity in tilled and non-tilled cropping systems

- Before ploughing, burrow continuity was at the same level in tilled and non-tilled systems.
- Earthworm burrow continuity was stable in the unploughed system.
- Burrow continuity decreased by 56% after ploughing.
- Five months post-ploughing, burrow continuity was 3 times lower than in the unploughed system.

Tillage influences first soil structure and then soil organisms such as earthworms, which are highly involved in the creation of soil macroporosity. This study assessed the temporal dynamics of earthworm-related macroporosity in two ploughed and one unploughed cropping systems. Three sampling dates were chosen: one month before ploughing, and one and five months after the event. Earthworm communities, able to rebuild the macroporosity, were sampled one and five months after ploughing. Before ploughing, the burrow continuity, i.e., the number of burrows with a vertical length greater than 5 cm, was not significantly different in the three systems. It was stable between the three sampling dates in the unploughed system but it decreased by 65% and 46% after ploughing (i.e., in two months) in the organic and the conventional systems, respectively. Five months after ploughing, the burrow continuity remained between two and four times lower than in the unploughed living mulch cropping system. Earthworm biomass was higher and burrow system characteristics (i.e. burrow volume and continuity) were more stable over time in the non-tilled with a living mulch cropping system than in the tilled systems. Earthworm-produced macroporosity was thus substantially decreased after ploughing in conventional and organic systems and had still not totally recovered 5 months later. This can lead to large functional consequences on soil structure and thus on air and water fluxes in the soil.