Characteristics Of Co-composting Chicken Manure With Maize Straw As Organic Substrate

This paper was funded by Chongqing Natural Science Foundation (CSTC,2008BB7048), aiming at investigating the effects of different initial C/N ratios of14(pile1),18(pile2), and30(pile3) throughout the co-composting process of chickenmanure and maize straw as well as that of outdoor composting (pile4) and reactorcomposting (pile5), by way of regulating the piles’ initial moisture content (MC),oxygen supply, C/N ratios, etc. Also, the germination index (GI) was determined toevaluate the phytotoxicity of compost. The results shown that temperature of pile2,3,and5can meet the provisions of GB7959-87, while that of pile1and4failed to satisfythem. The pH values of all piles, with a range of7to9, increased markedly in the earlycomposting stage, and decreased subsequently to the neutral level.Furthermore, the ultimate electrical conductivity of pile3was lower than pile1and2, while cation exchange capacity of pile3was higher, betraying the highercompost quality than pile1and2. Meanwhile, the total organic carbon contents of threepiles were evidently degraded, while total nitrogen and total phosphorus contents didnot show a steep fluctuation.As to outdoor composting (pile4) and reactor composting (pile5), the MC valuesreduced during co-composting process. Granted that the MC loss of pile4is less in thefirst7days, the total MC loss (26.5%) was higher than that of pile5(20.6%). Moreover,the organic matter (OM) was considerably degraded in the first21days, reaching81.4and84.5%of total OM degradation for pile4and5, respectively. Nonetheless, the netTN increase of both piles had shown no significant difference. The C/N ratios decreasedas the composting proceeded, signifying the great maturity and quality of compost.As far as phytotoxicity was concerned, the ultimate GI values ranged from61.3to82.4%. Pile3, with the initial C/N ratio30, revealed lower level of phytotoxicity thanpile1and2; and reactor composting (pile5) demonstrated lower level of phytotoxicitythan outdoor composting (pile4). In general, pile1,2,4, and5were at the low level ofphytotoxicity, and pile3was almost phytotoxin-free.In the final analysis, the initial C/N ratio30was superior to co-composting ofchicken manure and maize straw; and the reactor composting of chicken manure andmaize straw was better than outdoor composting.