Production And Application Of Biological Humic Acid

Humic acid is a kind of high molecular organic compounds formed by the decomposition and transformation of animal and plant residues.Humic acid exists widely in weathered coal and lignite and peat,also exists in soil,compost,waste liquor,alcohol wastewater,river mud and pond sludge.Humic acid is an important organic matter,which can improve the physical and chemical properties of soil.Research showed that the application of humic substances could improve the fertility of soil,and provide more comprehensive nutrition elements to plants.At the same time,humic acid can enhance the activity of microorganisms in the soil,increase the total amount of soil microorganisms and the number of beneficial microorganisms.In addition,humic acid plays an important role in remediation of heavy metals and toxic organic pollutants.Edible fungus residue refers to the remaining culture medium waste,which is used for the cultivation of edible fungi by the straw sawdust and other raw materials.The fungus residue is rich in bacterial proteins and metabolites,as well as many of the nutrients not being used,and contains a large number of species of microbial flora.A variety of sugars,enzymes,organic acids and bioactive substances are produced by the enzymatic hydrolysis of edible fungi.In addition,the content of trace elements such as calcium,iron,zinc and magnesium was also very rich(Dehan et al.,2007).With the rapid development of mushroom industry in China,a large number of mushroom bran are produced annually.The traditional method of treating the bran is burning or discarding,which not only causes a lot of waste of resources,but also causes environmental pollution.The biological humic acid can be produced by fermentation,which can turn organic waste into manageable materials.This treatment not only reduces the environmental pollution,but also creates a high value of biological humic acid products.In this study,the biological humic acid was produced by fermentation of edible fungus bran.The experiment was done with 2 kinds of compost treatment,which were treated by microbial inoculation and not inoculation(control),and each treatment was repeated for 3 repetition,and the composting duration was about 36 days.The maturity index and the change of humic acid content were determined.The experimental results showed that the microbial inoculation could accelerate the composting heating rate,improve the composting temperature and prolong the period of high temperature,pH value of the pile increased first and then decreased.The moisture content,total organic carbon content and carbon to nitrogen ratio of the pile were decreased,and the inoculum treatment decreased faster than CK.The total nitrogen content of the pile decreased first and then increased.And the seed germination index showed a rising trend.At the end of composting,the moisture content,total organic carbon content and carbon nitrogen ratio of the pile are significantly lower than that of control,the total nitrogen content and seed germination index were significantly higher than those of control.The content of total humic acid increased and then decreased,the content of free humic acid increased first and then decreased,the content of water-soluble humic acid has been increased until the end of composting,the content of fulvic acid increased firstly and then decreased.At the end of composting,the content of humic acid was significantly higher than that of control.The results showed that the microbial inoculants accelerated the composting process,which was beneficial to the decomposition of organic matter and the formation of humic acid.Biological humic acid was prepared from the compost samples by the method that humic acid can issolve in alkali and precipitate in acid.A pot experiments was conducted to study the effects of different concentrations of humic acid(1g/kg,2g/kg,4g/kg)on the growth,chlorophyll content and antioxidant enzyme system of rape under cadmium stress.The results showed that the 10mg/kg concentration of cadmium resulted in toxic effect on rape,adding the biological humic acid could increase the plant height and root length,and can improve the wet weight and dry weight,increase the chlorophyll content of rape leaves,and the leaf superoxide dismutase(SOD),catalase(CAT)peroxidase(POD)activity,reduce the cadmium stress on rape.When the concentration of biological humic acid was 2g/kg,it could effectively alleviate the harm of cadmium stress on rape,while the alleviation effect of high concentration of humic acid on cadmium stress was decreased.