| Currently, energy and environment problem has become the mainfactor in constraining social and economic development. In order to obtain acomfortable circumstance in the vast rural, development of ecological agriculture as alink digester is an effective measure to alleviate the energy and environmentalpressures. The key to promote the biogas construction is to utilize efficiently andrationally the methane fermentation products. For the sake of promoting a betterdevelopment of the biogas, it is necessary to study the effect of biogas manure on cropcultivation. It is also important to obtain a good utilization system of biogas manure.This paper was supported by commonweal industry-specific(agriculture) researchprojects “The research of combination unit and technology that Biogas fully replacespeasant households’ commercial energy”(NO.201303099).In the circumstance of fourkinds of light and temperature and six levels of fertilization, celery and lettuce werefertilized with biogas in flowerpot. An orthogonal experiment method was used toanalyze the effect of different light, temperature, fertilization levels, and growthcycles on celery and lettuce cultivation. A better cultivation condition and biogasmanure condition would be obtained from the above analysis. In addition, this papercombined with the ADB loan Henan rural ecological energy projects implementation,more than five years of application of biogas soil nutrients and heavy metals testingwere selected to know the effect of a long-term application of the biogas on the soilquality conditions. This research aims to achieve a theory support for the rationalutilization of biogas manure and for the promotion of the biogas project.The main results of this study are as follows:(1) The emergy for celery and lettuce cultivation was obtained from thecultivation experiment of celery lettuce using biogas manure. Different growingconditions and fertilization, celery and raw cabbages, stems and leaves caused adifferent emergy. But the differences were not obvious. The emergy of celery root wasbetween12.57and15.66MJ/kg. The celery stems emergy was between11.12and13.73MJ/kg. The celery leaf emergy was between11.23and15.74MJ/kg. The emergyof lettuce root was between11.78and13.36MJ/kg. The emergy of lettuce leaves was between12.55and14.18MJ/kg.(2) This study analyzed different light and temperature environments, differentlevels of fertilization and celery energy levels in different growth cycles, biogasutilization, and the energy efficiency. It shows an appropriate celery plantingconditions were greenhouses, fertilizer level, the growth cycle of100days, indoorbalcony environment, fertilization Ⅲ andⅣ, and the growth cycle of120days. If thesunlight intensity for celery cultivation was lower than122w/m2, the energy level andutilization rate of energy would be low.(3) This study also analyzed the different environments of light and temperatureand different fertilizer levels lettuce energy levels, biogas utilization, and energyefficiency. It could be concluded that a higher energy level and the energy efficiencyof lettuce growing conditions were shed and greenhouse fertilization ⅣandⅤ, andindoor balcony environmental fertilization Ⅳ. Climate chamber lettuce cultivationenvironment would generate a low energy level and energy efficiency.(4) A different light and temperature and different growth cycles and differentfertilizer levels would result in some differences in the effective utilization ofpotassium, organic matter and other nutrients for celery cultivation. The analysis ofthe effect of light and temperature on nutrient utilization showed that greenhouse forcelery cultivation had the highest utilization of nutrients, followed by indoor balconyenvironment, and low-light environments of climate chamber. The longer growthcycle of nutrient utilization, the higher nutrient utilization had. Effects of fertilizationon nutrient utilization levels showed the higher overall fertilization level, the lowerthe nutrient utilization. It suggested that a low level of fertilizer could not meet theneeds for a normal celery growth. Lower celery energy levels with a higher fertilizerlevels would cause a less biogas utilization by celery. Part of the biogas was storagedinto the soil.(5) The level of light and temperature environments and fertilizer suitable lettucegrown has been obtained through the analysis of the utilization of total nitrogen,phosphorus, available potassium, and organic matter in biogas for lettuce cultivation.In the four kinds of light and temperature environments, greenhouse environment wasthe most suitable for lettuce growing, followed by indoor balcony environment.Regarding the fertilization levels, the fertilization level Ⅰ, Ⅱ and Ⅲ could not meetthe demand for lettuce normal growth, fertilization Ⅳ and Ⅴ relatively more suitablefor lettuce growing. But there were also differences in light and temperature environments. This was consistent with the results obtained from the energy levelsand energy use efficiency for lettuce cultivation.(6)The article quantitatively analyzes the long-term impacts on the situation ofnutrients and heavy metals in soils which are often feed by biogas fertilizers. To someextent, the contents of organic matter, nitrogen, phosphorus and potassium in soilshave positive correlation with that in mixed biogas slurry. But there is no significantcorrelation between the contents of iron, manganese, copper, zinc, lead, arsenic insoils and that in mixed biogas slurry. Meanwhile, the content of mercury in soil hasnegative correlation with that in mixed biogas slurry.(7)Compared with the wastewater discharge standard, the concentration of heavymetals in mixed biogas slurry in certain areas, except copper and lead, does notexceed the standard. This fact demonstrates that biogas fertilizers feed in the farmlandare safe. But compared with the standards of irrigation water quality, theconcentration of heavy metals, except copper and lead in mixed biogas slurry in rareregions, already exceeds the standard limit. It means the long-term, frequentapplication of biogas fertilizers has a certain risk to improve the content of heavymetals in soils. The heavy metals in soils form the9regions where there arehousehold biogas ponds shows that comprehensive pollution index is less than0.7,which means the soils are still in a clean state.(8)The contents of organic matter, total nitrogen, available phosphorus, availablepotassium in soils can be reordered as followings:“the quaternary ecological model”>“the trinity ecological model”>“non-household biogas users”, especially “thequaternary ecological model” is much higher than the two others. Compared with theclassification standard of soil nutrients, the content of organic matter, total nitrogen,available potassium and available phosphorus in non-household biogas users’ soilsreaches individually5level,6level,3level and2level, and the overall level of soilnutrient is low. In the opposite, the content of organic matter, total nitrogen, availablepotassium and available phosphorus in non-household biogas users’ soils reachesindividually3level,5level,1level and1level, and the overall level of soil nutrient ishigh. So it demonstrates that the level of soil nutrient is increased by biogas fertilizer.(9) The content of micro-elements including iron, manganese, soil copper andzinc in the quaternary ecological model’s soils is the highest. Meanwhile the contentin the trinity of ecological patterns and non-household biogas users is mutual, but thedifference is not very obvious. The content of3kinds of toxic and harmful heavy metals including mercury, lead, arsenic in the quaternary ecological model’s soils, thetrinity of ecological pattern’s soils and non-biogas households users’ soils does notshow too much obvious differences. Biogas Fertilizer have little effect on the contentof less toxic and harmful heavy metals such as mercury, lead, arsenic in soil. |
PDF Full Text Request