Effect Of Different Initial Carbon To Nitrogen Ratio On Dairy Mannure Composting

The experiment was conducted to study the effect of different carbon to nitrogen ratio on thedairy manure composting with corn straw. The difference in manure/corn straw ratio among thethree treatments was reflected in C/N ratio. The experiment is managed with the aim of studyingthe change of each parameter during dairy manure composting, discussing the effect of the lowercarbon to nitrogen ratio on the composting, and optimizing the composting efficiency.Initial water contents were 68% for three treatments. Three different carbon to nitrogen ratioused for the composting experiment were 27:1,24:1 and 21:1 respectively at the beginning ofexperiment. Dairy manure/corn straw ratio (by weight) were 2.9:1,5.4:1 and 15.1:1, respectively.The change of temperature, pile color, odor and volume were recorded during composting. Thetreatments were sampled on days 0, 3, 7, 14, 21, 28 and 35d and analyzed for the water content,pHvalue,electrical conductivity,organic matter content,volatilis solid,total nitrogen content,manurecoliform value,ascarid egg and germination index.The results showed that the different carbon to nitrogen ratio treatments all could becomposted successfully. Temperature in the treatment of C/N 27:1 increased immediately aidermixing, reaching 50℃within 13 hours and the duration of thermophilic phase (＞55℃) is 6 days.The duration of thermophilic phase (＞55℃) was 7 days in the treatment of C/N 24:1 and 15 days inthe treatment of 21:1.The water content increased gradually at the beginning of experiment, subsequently declinedover time in all treatments. At the end of the composting, the water content both decreased to about61% in the treatment of C/N 27:1 and C/N 24:1. In contrast, compared to the initial water content,the final water content increased 4.5% in the treatment of C/N 21:1, which reached 73.2%.The total carbon content and organic matter content decreased and the total nitrogen contentincreased during the composting. The carbon to nitrogen ratio decreased over time in all treatments.The T value was less than 0.6 within 21 days of composting in all treatments, which showedcomposts were already mature. But the carbon to nitrogen ratio was 7.1 in the treatment of C/N21:1 at the end of composting.At the end of the composting, the color was brown or dark brown in all treatments. The odorwas disappeared completely. There was white or off-white myceliums in all piles and the cattlemanure were mixed uniformly with amendments. All ascarid eggs were killed in all treatments and coliform value was above 0.01. All treatments met the required criteria for composting set by theChina GB7959-87 regulations. The Germination Index of the three treatments was more than 80%.By preliminary studying on different initial carbon to nitrogen ratio, the main studying resultsand corresponding conclusiones have been attained as follow:Most parameter was essentially similar in the treatment of C/N 27:1 and C/N 24:1. The resultssuggested that a slight decrease of carbon to nitrogen ratio did not affect the dairy manurecomposting, and more quantity of dairy manure was composted. But when the carbon to nitrogenratio was lowered to 21 : 1, the higher ratio of dairy manure in the mixture resulted in a higher bulkdensity, and that would be unfavorable for the ventilation of pile and leaded to a excessive hightemperatures during the thermophilic stage and a longer duration of high temperature, a rapid lossof organic matter, a lower agricultural value of compost.