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

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.

Exploitation of a Half-Conjugate Polydentate Salamo-Salen Hybrid Ligand and Its Two Phenoxide-Bridged Heterohexanuclear 3d-s Double-Helical Cluster Complexes.

A half-conjugate polydentate Salamo-Salen hybrid ligand, H5L, containing two unique N2O2 pockets was first designed so that these metal ions in the complexes appear in different coordination modes. Two heterohexanuclear 3d-s double-helical cluster complexes, [Zn4Ca2L2(µ1-OAc)2(EtOH)2]·2EtOH (1; EtOH = ethanol) and [Zn4Sr2L2(µ2-OAc)2(MeOH)2]·2CH2Cl2 (2; MeOH = methanol), are reported that are formed through the reaction of H5L with zinc(II) and calcium(II) acetate or strontium(II) acetate, respectively. IR spectral analysis of the two complexes showed the existence of monodentate- and bidentate-coordinated acetate ions. The fluorescence properties of the ligand and its two heterohexanuclear complexes were explored in MeOH and water solutions, separately. In addition, theoretical calculations (density functional theory, interaction region indicator, and bond order) were performed to further understand the formation of a single-molecular double helix and the electron distribution characteristics of the two complexes.