The Effect Of Co-application Of Biogas Slurry And Hydrothermal Carbonization Aqueous Phase Substitutes As The Nitrogen Fertilizer On Ammonia Volatilization From Paddy Soil

Biogas slurry(BS)and hydrothermal carbonization aqueous phase(HCAP)are nutrient-rich wastewater derived from anaerobic fermentation and hydrothermal carbonization process,respectively.In order to prevent environmental pollution,it is great potential to convert biogas slurry and hydrothermal carbon liquid into organic fertilizer in agricultural field This study hypothesized that acidic hydrothermal carbon solution could neutralize alkaline BS,adjust pH of soil-water system to mitigate ammonia volatilization from paddy soil.In this experiment,pH,NH4+W-N concentration and soil urease activity in the soil-water system were measured to evaluate the effects of two liquid fertilizers on ammonia volatilization,rice yield,growth status,grain nitrogen content and amino acid content via soil column experiment during the whole rice-growth period.The treatments were set as follows:BSCM10 and BSCM20:the co-application of biogas slurry and cattle manure HCAP in a total nitrogen ratio of 9:1 and 4:1,respectively;BSV10 and BSV20:the co-application of biogas slurry and veggies HCAP in a total nitrogen ratio of 9:1 and 4:1,respectively.All the alternative treatments were conducted to substitute 50%,75%and 100%urea,respectively.The main conclusions of this study are as follows:(1)Biogas slurry and hydrothermal carbonization aqueous phase contain a large amount of nutrients(>700.0 mg·L-1)such as nitrogen and phosphorus(>5.0 mg·L-1),which can be provided for rice;No heavy metal elements were detected in BS and HCAP.Three-dimensional fluorescence(3D-EEM)analysis showed that the two liquid fertilizers contained a large number of fulvic acids(about 50.0%)and soluble microbial byproducts(about 69.9%),which could promote the abundance and activity of soil microorganisms.(2)The effects of biogas slurry and hydrothermal carbonization aqueous phase on ammonia volatilization in paddy fields were boiled down to pH and NH4+-N concentration of floodwater.For instance,reducing pH of floodwater could mitigate ammonia volatilization from paddy fields.BSCM treatments could mitigate ammonia volatilization up to 65.5%and a significant correlation was observed in pH and daily NH3 volatilization flux(P<0.05).At the same time,the daily ammonia volatilization emission flux gradually decreased with the reduction of the concentration of NH4W-N in the floodwater,which had the significant correlation between these two factors.(3)However,transforming biogas slurry and hydrothermal carbon aqueous phase into the paddy field reduced grain yield(by 20.0-40%)and nitrogen content of rice(by 5.2-7.8%),which affected the amino acid content of rice grains lower than that of control group.The results showed that the excessive substitution of urea by organic fertilizer could mitigate ammonia emission,but the plant could not directly absorb and utilize nitrogen in organic fertilizer,leading to the decrease of grain yield and nitrogen content.This study shows that the co-application of biogas slurry and hydrothermal carbon aqueous phase can substitute urea as a valuable nitrogen fertilizer provider and mitigate NH3 volatilization from paddy soil.This study will provide a new idea for the utilization of biogas slury and hydrothermal carbonization aqueous solution resources in the context of ammonia mitigation.Figures[12]Tables[5]References[150]...