Abstract: Taking the pig manure-rice straw mixtures with different C/N ratios (20, 25, 30, and 35) as the feed of earthworm
(Eisenia fetida), a 90-day incubation test was conducted to study the growth and reproduction of  E. fetida, with the average body mass, daily body mass increase, daily cocoon production, and accumulated cocoon production as the indicators. In the meantime, a 35-day composting experiment was arranged to assess the maturity of the same mixtures with C/N 25, 30, and 35, using pH, dissolved organic carbon (DOC), and C/N as the indicators. In the 90-day incubation test, the mixture with a C/N ratio 30 was most suitable for the growth and reproduction of E. fetida. In the 35-day composting experiment, the mixtures’ pH and DOC decreased in the first 21 days and increased thereafter, while the C/N decreased persistently during the 35 days. With the comprehensive consideration of the three indicators, the mixtures were still not fully matured by the end of the experiment. For the mixture with a C/N ratio 25, its C/N ratio was < 20 in the 7-35 days. Traditionally, the mixture was considered as composted matured when the C/N ratio was below 20, but based on the assessment of pH and DOC, the mixture was still under immature condition. Therefore, C/N＜20 alone was not a proper indicator for the maturity assessment on the composting of pig manure-rice straw mixture.

Key words: pig manure, rice straw, earthworm, C/N ratio, growth and reproduction, maturity index