Studies On The Fermentation Conditions And Feasibility For CO₂ Enrichment In Greenhouse By Using Of Organic Wastes From Agriculture

With t he development and growth of economy in China, agriculture has been growing up rapidly on a nationwide scale. Associated with the drastic growing in crop yield and animal production are huge quantities of agricultural wastes, primarily swine manure and crop straw. Lack of proper techniques in disposal of these wastes results in many public concerns about the environmental problems, such as water eutrophication brought about by runoff of nutrients, air pollution caused by burning of the crop straw. However, these "wastes" are a sort of natural resources that may be turned back into agro-ecosystem when it is properly treated. Another problem in agriculture is the CO: deficiency and soil degradation in green house. Greenhouse culture has also developed rapidly in recent decades in China because of its high profits. The fact that agricultural wastes contains mainly organic carbon that can be partially turned into CO2 by microbes leads us to the idea of attempting to enrich CO2 in green house by fermenting the a gricultural w astes. The o bjectives o fp resent r esearch w ere t o b e look for t he optimum fermentation conditions for the fermentation, to screen efficient microbes for CO2 evolution and to study the effects of the CO: enrichment on CO: concentration in the greenhouse and increase of vegetable yield as well as improvement of quality so that to establish a technological system for CO2 enrichment in greenhouse by biodegradation of agro-organic wastes and to inaugurate a new way for the benign cycling of carbon from agro-organic wastes in the ecological system of greenhouse. The results obtained from experiments are as follows:On the basis of a preliminary experiment by orthogonal design, in which the primary parameters suitable for CO2 evolution by bio-degradation of organic wastes from agriculture had been obtained, four single factor experiments were carried out to seek the optimal parameters for CO2 evolution which is used as CO2 fertilizer in greenhouse. The results showed that the impacts of all the six parameters are remarkable on CO2 evolution including initial C/N ratio of substrate, temperature, water content, initial pH and the kinds of organic wastes, and there are remarkableinteractions between initial C/N ratio, temperature and humidity. The order of impacts of six parameters on CO2 evolution are as follows: N sources > temperature > C/N ratio and water content > Straw type >pH. the optimal parameters for CO2 evolution by bio-degradation of mixture of rice straw and pig manure are 50C, 70% and 6.0-7.0 for temperature, water content and initial pH, respectively. Depending on the purpose of fermentation, 40/1 was the optimal initial C/N ratio of substrate for cumulative CO2 evolution, but 30/1 was better for compost.Three strains of thermophilic cellulose-decomposing microorganisms, named as strain A, strain B and strain C, respectively, were isolated from composting. All three strains showed a remarkable effect on CO2 evolution of bio-degradation of organic wastes in both laboratory and greenhouse conditions, especially inoculating with the mixture of three strains. Inoculating with the mixture of those three strains not only largely increase the quantity of CO2 evolution, but also prolong the duration of CO2 evolving fastigium. Therefore, inoculating with definite strains of cellulose-decomposing microorganisms is an effective measure for evolving more CO2 from bio-degradation of organic wastes in greenhouse, and the three strains of thermophilic cellulose-decomposing microorganisms isolated from our experiment should be valuable for this purpose.Under greenhouse conditions, crops generally suffer from CO2 deficiency. According field survey carried out in the greenhouse, it was found that the CO2 concentration is usually below SOOjil ?L"1 after 10:00am and about 150uL ?L"1 during 12:00am to 15:00pm, while it could be maintained higher than 500L L-1 in the whole day by the way of CO2 enrichment with bio-degradation of organic wastes. It indicated that it was very effective...