Efficiency of using earthworms to assimilate and transform straw-sludge mixture.

In order to explore the effect of earthworms assimilating and transforming straw-sludge mixture, a simulated cultivation experiment was carried out in laboratory. Six treatments were designed in the experiment, different in ratio of rice straw and municipal sewage sludge, that was, 0/100, 10/90, 20/80, 30/70, 40/60 and 50/50. Inoculated with earthworms, the mixtures were incubated at normal temperature. The mixtures were maintained duly in volume and moisture by replenishing the material and water in light of their consumptions. After 6 weeks of incubation, unassimilated materials were removed, weight of earthworms, their cast and nutrient content were measured, and hence assimilation of the mixture was calculated. Results showed that assimilation rate in treatments 10/90, 20/80 and 30/70 were much higher than that in other treatments. Biomass of earthworm in treatments 10/90 and 30/70 were significantly higher than that in treatment 50/50. Obviously addition of straws significantly increased the transformation rate of the mixture into bio-manure. Besides, organic matter instead of total nitrogen and total potassium content of earthworm cast bio-manure was positively related to the ratio of straws, However, total P dropped significantly when the ratio of straws reached 40% and 50% as compared with CK and treatment 0/100.