Changes in biochemical properties of cow manure during processing by earthworms (Eisenia andrei, Bouche) and the effects on seedling growth

The biochemical changes in fresh cow manure caused by the earthworm Eisenia andrei (Bouche) were measured over a period of four months, under controll ed laboratory conditions. Earthworms were introduced into each of four plas tic containers (0.4 x 0.27 x 0.15 m) containing fresh cow manure (2500 g), and four containers containing manure but without earthworms served as cont rols. Earthworms reduced the pH and decreased the moisture content in the m anure. The C:N ratio of the manure with or without earthworms decreased pro gressively from 36 to 21. The ash and total nitrogen contents increased gre atly for a few weeks after the introduction of earthworms, reflecting a rap id breakdown of carbon compounds and mineralization of nitrogen by the eart hworms. CO2 evolution decreased rapidly (44 %) one week after the introduct ion of earthworms, and continued at a lower rate throughout the 17 weeks (5 1 % reduction as compared to 22 % without earthworms), indicating increasin g stability of the organic matter. Earthworms reduced microbial biomass ear ly in the process, but enhanced nitrogen mineralization and increased the r ates of conversion of ammonium-nitrogen into nitrate. The major general eff ect of earthworms on the organic wastes was to accelerate the maturation of the organic wastes as demonstrated by enhanced growth of lettuce and tomat o seedlings.