Objective   Effects of earthworms of different ecological classifications on water infiltration of the soil in which they inhabited were studied.

  Method  Epigeic Eisenia fetida and endo-anecic Amynthas aspergillum were separately placed in soil containers to compare with one without earthworms. In a vertical one-dimensional stable water potential infiltration experimentation, the wetting front movement, accumulated infiltration, infiltration rate, and moisture content of the soil in the containers were monitored to analyze the correlation between soil properties and presence of the different types of earthworms in low-density at 4 g·kg⁻¹ or high-density at 8 g·kg⁻¹. The Philip and Kostiakov models were applied to mathematically describe the water infiltration function.

  Result  ① The existence of earthworms simultaneously reduced the advancing distance, advancing rate, cumulative infiltration amount, and infiltration rate of the water wetting front in the soil, especially in the case of low-density A. aspergillum (P＜0.01). The effect was more significant under low-density than high-density of the earthworms. ② Water retention of soil changed with the earthworm-induced water infiltration pattern which increased significantly by the low-density A. aspergillum treatment (P＜0.01). ③ The major driving factors on soil that affected water infiltration attributed by the earthworms were electricity conductivity, available phosphorus, and sand. ④ Kostiakov model fitted the correlation between the soil water infiltration and the earthworm treatments more than Philip model did. A high fitting accuracy on R_MSE≤4.80 mm was observed on the treatment by A. aspergillum. Moreover, A. aspergillum also significantly decreased the attenuation of cumulative water infiltration (P＜0.01).

  Conclusion  The water infiltration could be significantly lowered and moisture retention raised in a loamy sandy soil by the presence of E. fetida or A. aspergillum. It was conceivable that, at the density of 4 g·kg⁻¹ of A. aspergillum, land of similar kind of soil could benefit from the improved water holding capacity as a result.