Study On The Factors Affecting CO₂ Emission From The Vermicomposting Of Agricultural Waste

In recent years, the cultivation of greenhouse and plastic-covered greenhouse is developed very quickly in our country. However, CO2 deficiency problem has become an important limiting factor for the improvement of yield and quality in the cultivation. On the basis of a technique successfully developed for CO2 enrichment in plastic-covered greenhouse by fermentation of agricultural organic wastes, our research group put forward a new method for CO2 enrichment in the greenhouse, in which earthworm is used to degrade agricultural organic wastes.C/N ratio and water content of the medium and the density of earthworm were selected as three main factors affecting the vermicomposting of agricultural organic wastes in this study. A preliminary orthogonal design test and single factor experiments were carried out to screen the primary suitable conditions and the optimal parameters for the CO2 emission from the vermicomposting of agricultural wastes, respectively. The objective of this study is to lay the foundation for the development of a new technique for CO2 enrichment in greenhouse. The main results obtained from experiments are as follows:(1) The approximate conditions for generating CO2 with the vermicomposting of agricultural waste (straw+manure) obtained from the preliminary orthogonal design experiment were 30/1 of the initial C/N ration,65% of the water content and 50 of the earthworms density.(2) The optimal conditions for generating CO2 with the vermicomposting of agricultural waste (straw+manure) screened by single factor tests were 40/1 of the initial C/N ratio,75% of the water content and 60 of the earthworms density.(3) It was showed by experiments that the total organic carbon and the C/N ratio of the medium were significantly decreased while the contents of total nitrogen, total phosphorus and total potassium were obviously increased by vermicomposting. Above trends could be significantly enhanced by adding earthworm.(4) Verification tests showed that the quantity of cumulative CO2 emission by the vermicomposting of agricultural organic wastes under the optimum condition for 35 days was 9.44g, which is significantly higher than the release under the single factor conditions.(5) It was shown by estimation that the concentration of CO2 in the greenhouse could be increased from 300μl/L to 800μl/L two times a day by this CO2 enrichment method and each standard greenhouse can dispose 7.8 tons of fresh animal manure and 0.5 tons dry crop straw annually.