Joint effects of ferrous sulfate and biochar on aerobic composting of cow manure and spent mushroom residue and the performance of compost on soil improvement
To investigate the effects of ferrous sulfate and biochar application on composting process and product properties,and the effect of product application on soil fertilizer.Composting experiments were carried out in a self-designed forced ventilation aerobic composting reactor using cow manure and bacterial residue as raw materials.Different proportions of ferrous sulfate(Fe),biochar(BC)and ferrous sulfate+biochar mixture(FeBC)were added,respectively.After composting,the compost samples were mixed with soil for pot tests to study the effects of compost products on soil and plant growth.The results showed that the combined application of exogenous additives could prolong the high temperature period of compost,accelerate the composting process,and all the products met the application standards at the end of composting(NY/T 525-2021).The humus content of each treatment decreased first and then increased.FeBC treatment could promote the conversion of more organic matter into humic acid(HS),and the humic acid content was up to 115.0 g·kg-1 at the end of composting.The content of humic acid(HA)increased continuously with the composting time,while the content of fulvic acid(FA)decreased gradually.At the end of composting,the HA content in FeBC treatment was the highest(71.90 g·kg-1),while the FA content was the lowest(24.65 g·kg-1).The application of compost products significantly increased the soil organic matter content(44.2% )and NPK content(56.7% ),and the growth index of small green vegetables was also significantly increased.In addition,the addition of compost products increased the proportion of soil large aggregates,and the mean weight diameter(MWD)and geometric mean diameter(GMD)of mechanical aggregates were also significantly increased after the addition of compost products.The addition of FeBC compost products significantly increased the stability of soil mechanical aggregates compared with other compost products.The results show that the combined addition of ferrous sulfate and biochar can promote the composting process and improve the humification of compost better than the single use of additives.In terms of soil improvement,the compost products combined with ferrous sulfate and biochar can better improve the physical and chemical properties of soil to improve soil fertility.
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