EARTHWORM POSITIVELY INFLUENCES LARGE MACROPORES UNDER EXTREME DROUGHT CONDITIONS AND CONSERVATION TILLAGE IN A CHINESE MOLLISOL

It is often claimed that earthworms exert a huge influence on soil macroporosity. Nevertheless, gaps still exist in our knowledge of rangeability in soil macroporosity caused by earthworm activity. Earthworms are generally recognized as ecosystem engineers vital for soil ecosystem function and services, but the potential mechanism of earthworm response to the combination of extreme drought and conservation tillage has not yet been identified. To improve understanding of the effect of the earthworm on soil macroporosity and how earthworms, through soil macroporosity, respond to extreme drought and conservation tillage, a study was conducted to compare soil macroporosity under different tillage treatments with the same number of earthworms in incubation conditions and soil structural properties (soil penetration resistance, infiltration rate, saturated hydraulic conductivity) associated with macroporosity, together with crop yields under different tillage systems and drought stress in field conditions. The results show that earthworms only increase the volume of large macropores (> 100 mu m) rather than small macropores (30-100 mu m) under different tillage systems. Earthworms played a positive role in the development of large macropores, as evidenced by the formation of paths of least resistance under high penetration resistance, higher infiltration rate and saturated hydraulic conductivity and no obvious yield loss under extreme drought and conservation tillage in a Chinese Mollisol.