The earthworm species Eisenia fetida modulates greenhouse gas release and carbon stabilization after rice straw amendment to a paddy soil

We performed a mesocosm experiment with rice paddy soils of three different soil types which were collected in the three major regions of rice production in Russia: Krasnodarsky Krai, the Republic of Kalmykia and Primorsky Krai. We used the earthworm species Eisenia fetida (Savigny 1826), introduced at different densities (0, 2, 4 and 6 individuals per mesocosm with an area of 69.4 cm2 and a soil column height of approximately 10 cm) to assess rice straw decomposition and carbon stabilization in the three soil types. After 20 days of the experiment, straw amendment consistently increased CO2 release from all three soil types. The effect was highest in the soil of Krasnodarsky Krai after a straw amendment was combined with 4 earthworms per mesocosm. The effect of earthworms on CH4 release remained soil type specific but did not demonstrate any synergy with the straw amendment. We also recorded the highest enrichment of soil with carbon from the rice straw when compared with the control