| In nature,plants can respond to environmental stress and nutrient supplies with their physiological integration ability.Traditionally biogas slurry is a kind high quality organic fertilizer.However,with the development of large-scale pig farms and biogas projects in China,the amount of biogas slurry is huge and the composition become more complex.There is no enough land around the large pig farms for biogas slurry utilization.The surplus biogas slurry has caused a greater environmental load in various parts of China,which threatens food safety and human health.Traditional land reclamation and modern sewage treatment technology cannot solve this problem completely.As a new modern vegetable cultivation technology which can protect environment,hydroponics has effectively solved the problem that vegetable production was constrained by the shortage of land resources and natural conditions.The application of biogas slurry to hydroponics is beneficial for pig farming enterprises to combine large-scale pig-raising with biogas slurry facility utilization,to form a closed cycle green agriculture model without wastewater emission.Therefore,the study on the physiological response and growth characteristics of plants in biogas slurry hydroponic environment is helpful to explore the mechanism of plant stress-resistant physiological response and helpful to guide hydroponic production practice.Firstly,the environmental stress and physiological response of aquatic plants,such as rice(Oryza sativa),cress(Oenanthe javanica),water cress(Nasturtium officinale)and terrestrial plants,such as Gynura divaricata,Sedum aizoon,strawberry(Fragaria ananassa)and celery(Apium graveolens),cultivated with different source and dilution multiple of biogas slurry were studied.The results showed that the optimum dilution multiples of biogas slurry was the same when different plants,such as cress and watercress,or cress and celery,were cultured with the same kind of biogas slurry.But the optimum dilution ratio was different when the same plant,such as cress,was cultured with different kinds of biogas slurry.The optimum dilution multiples of biogas slurry from three pig farms were 45,20 and 30 times,respectively.The conductivity of the diluted slurry with optimum dilution multiples ranged from 0.54 to 0.61 ms/cm,the total nitrogen content ranged from 17.9 to 28.9 mg/L,the total phosphorus content ranged from 0.62 to 4.5 mg/L,and the total potassium content ranged from 17.8 to 26.7 mg/L.The optimum dilution multiple is the result of the plants,self-balance and selection to various advantages and disadvantages factors existed in the diluted biogas slurry.Under the optimum dilution multiple,aquatic and terrestrial plants show strong physiological adaptability and can survive and grow well.Rice has a whole growth cycle,it can bloom and produce rice;cress and watercress can also grow,bloom,produce seeds;strawberry can bloom and bear fruit;Gynura divaricata,Sedum aizoon.and celery have good biological growth.The nutrients of the biogas slurry diluted in optimum multiples can basically meet the needs of plants above-mentioned.However,growing in all kinds of different dilution of biogas slurry,all plant are subject to certain degree of environmental stress,knowing that from the change of the plants' biomass indicators,physiological indicators and morphological indicators.For example,the yield and quality of rice and strawberry were significantly different from CK,and the growth of each plant was also significantly lower than CK;Strawberry bloom and bear fruit earlier than that cultivated in soil,possibly due to impacts of the stress.Secondly,the inhibition factor existed in biogas slurry and dilute slurry were analyzed.On this analysis,a special adding formula for biogas slurry to plants is proposed.The principle is that the biogas slurry is diluted to the optimum multiple,and its element's content is compared with the plant nutrient solution formula.The missing element concentration is converted into the corresponding compound concentration to form an operable biogas slurry additive formula.The results showed that comparing with the common nutrient solution group,the indexes of the cress cultivated in the biogas slurry additive formula changed significantly:the fresh weight increasing rate,fresh weight ratio,netphotosynthetic rate,transpiration rate,chlorophyll,root enzyme activity,soluble sugar,soluble protein and vitamin C were increased.But the nitrate content and intercellular CO2 were decreased.There was no significant difference on the index of plant height,leaf area,root length,root surface area,total root number and stomatal conductance.The growth and quality of the cress have been greatly improved.The growth and quality indexes were also much better than those of cress cultivated in soil.The biogas slurry addictive formulation is effective in improving the quality and physiological indexes of cress.The research results can provide a theoretical reference for the new way of utilizing biogas slurry. |
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