Vermicomposting of Duckweed (lemna Minor L.) Biomass by Eisenia Fetida (sav.) Earthworm

This work presents the dynamics of E. fetida (Sav.) earthworm populations during vermicomposting of duckweed (Lemna minor L.) biomass in small containers, and provides properties of the vermicomposts produced. An experiment was conducted under laboratory conditions (in darkness, at an average temperature 25±5oC, with substrate moisture 70-75%). Test pots (3 replications for each duckweed treatment) were filled with one litre of garden soil, into which 100 individuals of E.fetida, of known biomass, were introduced per pot. Duckweed was fed to earthworms regularly, in two treatments: (1) duckweed + + cattle manure (1:1), and (2) duckweed only. Earthworm number and biomass of tested populations were determined after 4 months of vermicomposting, and it was found that an average number of E.fetida in containers with duckweed and manure was 121±5 ind./container with a total biomass of 25.8±1.1 g. Populations in pure duckweed were significantly smaller (p<0.05), with 57±6 ind./container and a total biomass of 9.8±1 g. Cocoon production was also different across treatments. Populations in duckweed alone produced 55±13 cocoons /per container, significantly less (p<0.05) than the 231±37 cocoones when manure was added. Duckweed vermicomposts were odourless and had good granular structure. Chemical characteristics of both vermicompost types (with or without a manure supplement) were desirable. Content of macroelements in duckweed vermicomposts was high, whereas microelements, cadmium and lead were within the permitted levels, making these vermicomposts extremely useful in environmental reclamation, including agriculture. The manure addition was important for characteristics and chemical content of duckweed vermicomposts. The vermicomposts produced from duckweed and manure contained more ash, N, P, K, Mg, Zn, Cu, Ni, Cr, Cd and Pb.