Mixing garden wastes and spent mushroom compost of different ratios for vermicomposting

To explore the best ratio of garden waste (GW) and spent mushroom compost (SMC), so as to provide a fundamental basis for resource utilization, Eisenia fetida 'Daping 2' (earthworms) were used for mixed composting. Five treatments (GW + SMC, dry weight ratio) were set, namely:A1(100% + 0%), A2(75% + 25%), A3(50% + 50%), A4(25% + 75%), and A5(0% + 100%) and 3 replications. The quantity and quality of mature earthworms as well as the quantity of juvenile earthworms and earthworm cocoons of Eisenia fetida 'Daping 2' for the different treatments were measured during the entire vermicomposting period of 11 weeks. Chemical properties of initial materials and final vermicomposts were also analyzed. Moreover, a germination experiment was conducted to estimate the maturity of the vermicompost. Results showed that growth and reproductive performance of earthworms treated by A2 and A3 were much higher than those of the other treatments(P < 0.05). The nutrient increasing rates (for K, Cu, and Zn) in the compost for A3 and A4 treatments were much higher than those of other treatments(P < 0.05), and vermicomposts reached maturity. The K content for A3 was (28.05 ±6.13) g·kg-1 and for A4 was (28.32 ±5.66) g·kg-1, Cu content for A3 was (21.91 ±2.78) mg·kg-1 and for A4 was (34.08 ±3.34) mg·kg-1, and Zn content for A3 was (27.22 ±1.51) mg·kg-1 and for A4 was (32.76 ±2.97) mg·kg-1. Also, when 50% or more SMC was added, a high electrical conductivity(EC) value occurred, but with 75% or more SMC, growth of earthworm cocoons was limited. Thus, comprehensive factors indicated that, the quality of compost was best with A3 meaning it application of cultivated substrates for low sensitivity plants was recommended or water leaching should be adopted to reduce the EC value of A3 compost in actual production.