Research On Application Of Active Ventilation Fermentation Heating And Supplemental Gas System In Insulated Plastic Greenhouses

Recently,the development of facility horticulture in China is rapidly,facility vegetable residue yield is large and is difficult to deal in production,resulting in waste accumulation and environment affected.In addition,in the process of facility cultivation,low temperature and CO2 deficit usually occurs.Atmospheric CO2 concentration cannot reach the optimal concentration required for the growth and development of most crops,which affects photosynthesis.At present,aerobic fermentation treatment of vegetable straw is a method to solve the problem of vegetable residue accumulation in facilities and make vegetable straw resource utilization.Aerobic fermentation produces a lot of heat,which can increase the temperature of greenhouse;the CO2 released during composting can be used by crops;composing mature products can also be used as substrate cultivation materials to participate in vegetable growth,which is of great significance to efficient utilization of straw resources and promote sustainable development of vegetable industry in facilities.However,most of the current aerobic fermentation methods of a large number of agricultural wastes in facilities are static composting with natural ventilation,which cannot provide sufficient oxygen for the interior of the reactor and affects the fermentation rate.At the same time,harmful gases produced in the fermentation directly escape in the room,easy to cause environmental pollution;and it is a waste of resources to fail to maximize the use of CO2 gas generated according to crop growth needs.There are few reports on the aerobic fermentation system that combines active ventilation with active utilization of CO2 in facilities.In this study,an active ventilation fermentation heating and supplemental gas system（AVFHSGS）was built in a plastic greenhouse.The system absorbs indoor hot air through the intake fan to provide O2 for the interior of the reactor from bottom to top,and then the air above the reactor is discharged to the interior through the filter device to supplement CO2 for crops through the exhaust fan.The following studies were conducted on AVFHSGS in this experiment:Firstly,the feasibility of applying AVFHSGS in thermal insulation plastic greenhouses in the facility was discussed.Secondly,the application effect of the system using CO2 produced by fermentation to supplement gas fertilizer for crops and the applicability of fermentation products were studied.The main conclusions are as follows:（1）The feasibility of operation AVFHSGS in the insulated plastic greenhouse was verified from the following four aspects:the temperature of fermentation reactor,the warming effect of AVFHSGS,the concentration of NH3,N2O and CH4 harmful gases released,and the availability of fermentation products.The maximum daily average temperature of AVFHSGS was 53.5℃,11.0℃ higher than that of the natural ventilation fermentation system,and the time of the bulk temperature above 50℃ reached 7 days,which met the requirements of the national code for harmless composting.Compared with the control,the average air temperature at night in the test was 1.8℃ higher.The concentrations of NH3,N2O and CH4 irritant toxic gases released by AVFHSGS filtration were 5.23～14.00μmol/mol,0.56～0.86μmol/mol and 2.8～14.10 μmol/mol in the test respectively,much lower than those affected by humans and crops.The fermentation product extract of AVFHSGS can be used for seed germination of green vegetables,and the germination rate can reach 90%.（2）The range of CO2 concentration in the test area is 880～2100 μmol/mol.The chlorophyll content of tomato in the test area（T）was 16.98%significantly higher than that in the control area（CK）.The photosynthetic characteristics（net photosynthetic rate Pn,stomatal conductance Gs,intercellular CO2 concentration Ci,and transpiration rate Tr）of T were respectively 30.14%,120%,85.12%,51.48%significantly higher than those of CK.The average yield per plant was 2.79 kg/plant of T was 49.29%,higher than CK.AVFHSGS supplemented sufficient CO2 fertilizer for the crops in the insulated plastic greenhouse,promoted the photosynthesis of tomato,and significantly increased the yield of tomato.（3）Research on matriculation application of mature products,the tomato plants cultivate in substrate which mixed with 100%fermentation products of AVFHSGS（T1）compared with the substrate which mixed with AVFHSGS and garden soil at a volume ratio of 1:3 as substrate（T2）tomato plants and cultivate in garden soil（CK）.There was no significant difference in leaf chlorophyll content among the three.Pn,Gs and Tr of T2 and CK were significantly higher than those of T1,while T2 was significantly higher than CK.There was no significant difference in the average yield per plant between T1 and T2.The average yield per plant of T1 and T2 were 2.29 kg,2.19 kg,and T1 was significantly higher than that of CK by 27.33%,and there are no difference between T2 and CK.The fermentation product of AVFHSGS was used as the raw material and the garden soil was mixed into the form of compound matrix with the volume ratio of 1:3.It was more efficient and economical to use in the crop cultivation of insulated plastic greenhouses.In conclusion,AVFHSGS is feasible as indoor fermentation system,which can be used as heat source and CO2 source for crop growth in insulated plastic greenhouses and provide fertile cultivation substrate materials for vegetable cultivation.