| In recent years,Liaoning Province has actively strived to become a national forest city,vigorously promoted the construction of forest city,and achieved a 0.5 percentage increase in forest coverage and 34 million cubic meters of forest stock during the "14th Five-Year Plan" period compared with 2020.However,with the increase of urban forest coverage,plant wastes such as dead leaves,branches,harvesting residues and wood processing and utilization residues produced by forestry in the natural and felling process have also increased greatly,which has become a major problem in urban construction and environmental management.At present,the treatment of forestry waste is mainly based on traditional disposal methods such as incineration,landfill,and composting,and some waste is also mixed into municipal solid waste.These unreasonable disposal methods have a serious impact on the overall ecological environment,air quality,and city appearance of the city.If forestry waste is fully utilized,making biochar will be an effective way to solve environmental problems and realize the resource utilization of waste.In addition,biochar can also be used to load fertilizer and play a slow release role because of its strong adsorption capacity,which will help improve fertilizer utilization rate and reduce fertilizer loss.Therefore,the preparation of biochar-based fertilizer by using forestry waste biochar as a slow-release carrier of fertilizer is one of the very effective ways to solve forestry waste.In this paper,fruit wood and miscellaneous wood biochar were selected as the carrier of nitrogen fertilizer,the effects of different control factors(biochar amount,p H,initial nitrogen concentration,loading time)on biochar-loaded nitrogen fertilizer were analyzed,the optimal conditions of biochar-loaded nitrogen fertilizer were explored,and the slow-release effect of biochar-loaded nitrogen fertilizer was evaluated.The main findings are as follows:(1)Studies of different control factors showed that the nitrogen loading rate of fruit wood biochar and miscellaneous wood biochar was 49.74%～64.44% when the amount of biochar was 0.01 g～1 g,and the nitrogen loading of both types of biochar was the largest when the amount of biochar was 0.01 g.When the amount of biochar was 0.01 g,the nitrogen loading amount and nitrogen loading rate were the largest when the p H of fruit wood biochar and miscellaneous wood biochar were 7 and 9,respectively.When the initial nitrogen concentration is 50 mg/L,the maximum nitrogen loading rate of fruit wood biochar can reach 77.35%,and the maximum nitrogen loading rate of mixed wood biochar can reach 78.99%;the two biochar isothermal adsorption processes are well fitted with the Langmuir-Freundlich model,and when the loading time is more than 2 h,the loading of fruit wood biochar and miscellaneous wood biochar basically reaches the saturated state.Both biochar kinetic adsorption processes fit well with the Second-order model.(2)The optimal nitrogen loading rate of fruit biochar and miscellaneous wood biochar was determined by orthogonal test,that is,the biochar amount was 0.05 g,the initial p H value was 7,the initial nitrogen concentration was 350 mg/L and the loading time was 2 h.(3)The results of the soil column leaching simulation study showed that compared with the urea group,the total nitrogen release of fruit wood and miscellaneous wood biochar-based nitrogen fertilizer was lower than that of urea group,and the slowing effect was obvious after 1～3 days of leaching,and the cumulative nitrogen release rate was reduced by 9% and 11% compared with the urea group,respectively.The nitrogen release characteristics of fruit wood and mixed wood biochar-based nitrogen fertilizer conform to the variation law of Sugihara model,and have the nutrient release characteristics of slow-release fertilizer.In summary,the research results can provide scientific basis and theoretical guidance for the preparation of biochar based nitrogen fertilizer from forestry waste,as well as a way to reduce fertilizer application and increase efficiency for agricultural fertilization. |
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