Evaluation Of The Nutrients And Safety Of Vermicompost And Research On The Production Process Of Vermicompost Tea

The utilization of earthworms to treat organic waste to produce organic fertilizer is an effective way to realize the recycling of solid waste and promote the green development of agriculture.However,the nutrient and safety status of vermicompost are not clarified due to the different raw materials for the production of vermicompost.At the same time,the in-depth development and utilization of vermicompost are not deep enough,so it is necessary to develop relevant research.In this study,based on the evaluation of the nutrient and safety status of 60commercially available vermicomposts,samples of vermicomposts with higher nutrient content and safety were selected to explore different fertilizer-to-water ratios,aeration rates,and fermentation through orthogonal experiments.It is expected to provide reference for clarifying the nutrient and safety status of vermicompost in the market,finding out the production process of vermicompost tea,and scientific and rational utilization of vermicompost.The main research conclusions obtained are as follows:1.The pH range of vermicompost is 5.33～9.08,with an average value of 7.05.96.7%of vermicompost samples meet the requirement of pH 5.5～8.5 in the national standard for organic fertilizer（NY525-2012）.The organic matter content ranges from 84.70 g/kg to777.47 g/kg,with an average content of 322.47 g/kg.25.0%of the vermicompost samples met the 450g/kg requirement in the standard.2.Vermicompost is rich in nutrients and the nutrient status is good.The contents of N,P₂O₅,and K₂O in vermicompost ranged from 3.43 g/kg to 60.21 g/kg,0.64 g/kg to 24.47 g/kg,8.35 g/kg to 108.24 g/kg,and the average content was 12.26 g/kg,5.37 g/kg and 11.15 g/kg,respectively.The total nutrient content of 8.3%of vermicompost samples met the required5.0%.From the average content,the concequence of trace elements is Ca>Fe>Mg>Mn>Zn>B>Cu>Ni>Mo.3.The content ranges of Cr,Cd,As,Pb,and Hg in vermicompost are 9.26～65.61 mg/kg,0.01～3.55 mg/kg,3.59～24.40 mg/kg,5.67～139.05 mg/kg and 0.01～16.91,respectively mg/kg;the average content is 27.52 mg/kg,0.54 mg/kg,7.01 mg/kg,25.08 mg/kg and 0.68mg/kg respectively.Fifty-one samples were qualified and met the standard,with a pass rate of85.0%;the safety of vermicompost was determined by the source of raw materials.4.Different fermentation conditions have different effects on vermicompost tea.The ratio of fertilizer to water,aeration rate and fermentation time all have significant effects on the nutrient extraction of vermicompost tea（p<0.05）.The nutrient extraction of vermicompost tea showed an upward trend with the continuous increase of fertilizer-water ratio and the continuous increase of aeration;as the fermentation time prolonged,the nutrient extraction of vermicompost tea increased first and then decreased.Comprehensive analysis shows that earthworm manure is rich in nutrients,and the optimal combination of extraction process parameters for earthworm manure tea is a fertilizer-water ratio of 1∶2,an aeration rate of 2.4 L/h,and a fermentation time of 3 days.