Preparation And Application Of Nitrogen-rich Organic Liquid Fertilizer On Chinese Cabbage

Nitrogen is one of the three elements of plant nutrition and plays an important role in the growth and development of plants.Nitrogen application is an important measure to increase crop yield.Organic fertilizer is one of the important sources of nitrogen.Rational use of organic fertilizer can improve soil physical and chemical properties,enrich soil beneficial microbial population,protect ecological environment and so on.It is a trend of agricultural development to replace chemical fertilizer with organic fertilizer.Most of the leaves and straw left in the field after harvest are discarded.leaving them to rot or burn,causing pollution to soil,water and atmosphere.Vegetable waste contains a variety of nutrients,and it is used as the main raw material to prepare nitrogen-rich organic liquid fertilizer by solid-state aerobic fermentation.It is of great significance to realize clean production of vegetables and meet the demand of ecological circular agriculture for liquid fertilizer.In this experiment,cabbage tail vegetable was used as the main material to explore the technology of preparing nitrogen-rich organic liquid fertilizer based on aerobic fermentation.The quality of nitrogen raw materials(soybean meal:fish meal)(A),the inoculation amount of fermentation microorganisms(Bacillus subtilis,Aspergillus oryzae,yeast)(B)and the quality of cabbage tails(C)were used as three experimental factors.Three levels were set according to the initial quality of the fermentation materials.The L9(3 × 3)orthogonal test design was used to carry out the solid aerobic fermentation test,and the total nitrogen and nitrate nitrogen content were used as the key indicators to screen the best fermentation material formula.In order to obtain the best extraction parameters for the preparation of nitrogen-rich organic liquid fertilizer,the extraction test was carried out with the best fermentation material formula.Finally,the application effect of nitrogen-rich organic liquid fertilizer on Chinese cabbage was comprehensively evaluated under hydroponic and substrate cultivation conditions.The main results are as follows:(1)In the aerobic fermentation experiment of cabbage tail vegetables,the best fermentation formula was obtained:nitrogen material 15%.fermentation microbial inoculation 1.2%,cabbage tail vegetables quality 80%;the total nitrogen content reached 12.02%and the nitrate nitrogen content reached 2639.3 mg/kg on the 10 th day of fermentation,which was significantly higher than other treatments.The order of the three factors affecting the total nitrogen content was A>B>C,that is,the effect of nitrogen materials was the most obvious.During the fermentation process,the total nitrogen content {x)in the fermentation material was closely related to the pH value(y1} and urease(y2).The pH value was in accordance with the formula:y1=938.57x3.309(R2=0.585**),and the urease activity was in accordance with the formula:y2=0.3924x2-0.8143x + 1.8746(R2=0.4476**).(2)In the experiment of using solid organic fertilizer to prepare nitrogen-rich organic liquid fertilizer by water soaking and extraction,the treatment with the highest total nitrogen content in the extract was consistent with the theoretical optimal treatment.The optimal treatment was the ratio of water to material 7.5:1,the number of extractions 3 times,and the soaking time 12 h.The total nitrogen content of the treatment was 4965 mg/L,and the nitrate nitrogen content was 362.76 mg/L,which was significantly higher than other treatments.The primary and secondary order of the three factors affecting the total nitrogen content in the extract was the number of extractions>the ratio of water to material>soaking time,that is,the number of extractions was the most significant.(3)Under hydroponic conditions,the quality of Chinese cabbage was significantly improved by replacing nitrogen in chemical fertilizer with nitrogen-rich organic liquid fertilizer,but the fresh weight of whole plant was significantly lower than that of the latter.The contents of soluble protein,soluble sugar.Vc and chlorophyll in Chinese cabbage cultivated by T1 treatment(nutrient solution organic nitrogen concentration 4205.2 mg/L)increased by 16.3%.104.9%,190.6%and 42.3%respectively compared with CK(nutrient solution chemical nitrogen concentration 4205.2 mg/L),and the nitrate content decreased by 38%.In terms of whole plant fresh weight,T1 treatment and T2 treatment(nutrient solution organic nitrogen concentration 3574.4 mg/L)were 28.5%and 10.1%lower than CK treatment,respectively.(4)Under the condition of substrate cultivation,nitrogen-rich organic liquid fertilizer can significantly improve the morphology and quality of Chinese cabbage,and can significantly increase the fresh weight of Chinese cabbage under the condition of equal chemical nitrogen application.The plant height,plant width,root length and leaf area of Chinese cabbage cultivated in treatment A(1.213 g/plant of organic liquid fertilizer)were 18.9%,12.4%,14.4%and 32%higher than those in treatment D(1.213 g/plant of chemical fertilizer),respectively.The content of soluble sugar and anthocyanin increased by 48.9%and 30%,while the nitrate content decreased by 19.3%,and the fresh weight of the whole plant increased by 40.1%.The morphological index and fresh weight of the whole plant of Chinese cabbage cultivated by B treatment(1.032 g/plant of organic liquid fertilizer)reached the same effect as D treatment,and the quality was better than the latter.(5)Under the condition of substrate cultivation,the application of organic liquid fertilizer can significantly increase the richness of soil microbial community.At the phylum level,the number of dominant bacteria such as Actinobacteria,Firmicutes and Bacteroidetes was increased.Among them,the three types of flora under treatment A(nitrogen application of organic liquid fertilizer 1.213 g/plant)were increased by 127.3%,6.3%and 50%respectively compared with treatment D(nitrogen application of chemical fertilizer 1.213 g/plant).The number of glutamic acid bacteria and lysine Bacillus was increased at the genus level,and the two types of bacteria under A treatment were 196.1%and 31.4%higher than those under D treatment.