Preparation Of Selenium-rich Organic And Inorganic Compound Fertilizer From Lobster Waste

With the continuous improvement of China’s economic level,the total demand for food products is on a continuous rise,and the consumption of protein will continue to increase in the long term,which has led to the rapid development of the farming industry,resulting in a large amount of agricultural organic solid waste.As a major lobster-consuming country,China produces a large amount of lobster waste each year due to the crude processing of lobster,which is not efficiently utilized and is discarded at will,polluting the environment.In this study,lobster waste was used as the main raw material,and lobster waste organic fertilizer was obtained by adding fermenters and chicken manure for fermentation,and then inorganic fertilizer and selenium ore were added in proportion to prepare a lobster waste selenium-rich organic-inorganic compound fertilizer.Finally,the lobster waste selenium-rich organic-inorganic compound fertilizer was used to grow cabbage for experiments,and the growth indexes of cabbage were analyzed and discussed to test the fertilization efficiency of the compound fertilizer.In this study,the optimal fermenters and nitrogen sources were determined by controlling a single variable.Among all the fermentant types discussed in this paper,the mixed fermenters showed the optimal results.Similarly,the maximum total nutrient content was obtained when chicken manure was used as the nitrogen source.This is because the pile had the longest fermentation temperature and duration,the highest total nutrient content,and the most adequate fermentation during the thermophilic period with chicken manure as the nitrogen source and in the presence of mixed fermenters.Subsequently,Box-Behnken response surface experiments were designed using Design-Expert 12 with the proportion of mixed fermenters and chicken manure nitrogen source as the two influencing factors and total nutrient content as the response value.A 2-factor,3-level experiment was used to determine the optimal composting conditions.The results showed that the maximum total nutrient content of 6.59% was predicted to be obtained when the mixed fermentant ratio was 4(organic fertilizer fermentant: selenium-rich-Bacillus subtilis)and the nitrogen source of chicken manure was added at 220 g.The total nutrient content was measured experimentally to be 6.56%,indicating that the method was more accurate.Three formulations of organic-inorganic compound fertilizer with lobster shells were designed by theoretical calculation,and their physicochemical properties and nutrient elements were tested and analyzed,and the organic-inorganic compound fertilizer with selenium source was optimized for selenium enrichment,and finally,two better formulations,formulation 1 and formulation 2,were selected.The total nutrients were tested to be 18.61% and 27.45%,respectively,and the organic matter was 23.42% and 17.97%,respectively.It was shown that the standard of GB/T18877-2020 "Organic Inorganic Compound Fertilizer" was met.Finally,the two optimized formulations were experimentally verified by cabbage pot experiments to investigate the effects of lobster waste selenium-rich organic-inorganic compound fertilizer on the growth condition,quality,soil physicochemical properties,and selenium content of cabbage,and to compare them with blank and organic fertilizers.The results showed that the lobster waste selenium-rich organic-inorganic compound fertilizer had significant effects on the growth of chard and the increase of selenium content.The height of cabbage plants grown with COI-2 fertilizer was 45.8% higher than CK,Vc content increased by31.89%,soluble sugar content increased by 69.58%,and selenium content increased more than 2 times.It indicates that the best results for chard grown with fertilizer were obtained by adding 15.7% urea,16.9% diammonium phosphate,17.2% potassium chloride,and 4% selenium ore to the organic fertilizer of 46.2%.