Earthworms promote the transfer of 15N-urea to lettuce while limit appreciably increase 15N losing to environment

Abstract

Earthworm activities not only increase nitrogen (N) uptake by crops, but also lead to N losing to environment. Thus, the present study examined the transformation of ¹⁵N-labeled urea with and without earthworms (Metaphire guillelmi) in a soil-lettuce system. We evaluated lettuce ¹⁵N uptake, ¹⁵N losses including N₂O emission, NH₃ volatilization and leaching, as well as ¹⁵N remaining in soil. Results showed that ¹⁵N-urea uptakes by lettuce significantly increased from 33.07% to 42.72% with earthworm presence. However, little difference was found on the total amounts of leaching and gaseous losses (N₂O emission and NH₃ volatilization) from ¹⁵N-urea between the treatment with and without earthworms (4.04 and 5.38%, respectively). Most of the ¹⁵N-urea remained in the soil, accounting for 48.44% and 60.65% of the ¹⁵N-urea in soil with and without earthworm presence. We conclude that earthworms enhanced the transfer of ¹⁵N-urea to lettuce without appreciably increasing the ¹⁵N-urea loss from soil to the environment.

Keywords: (15)N-urea; Earthworms; N transformations; Pot experiment; Soil-plant system.