Effects Of Tea Residue Biochar Produced By Different Pyrolysis Temperatures On Retentionand Transformation Of Soil Nitrogen

As a carbon produced by high-temperature pyrolysis and carbonization in the case of complete or partial oxygen deficiency,biochar has an important role in soil improvement and has received extensive attention at home and abroad.Due to the difference in biomass raw materials and pyrolysis conditions,the basic physical and chemical properties of biomass carbon are different,and the effects on the soil environment are different after being applied to the soil.In recent years,the environmental impact of different raw materials and pyrolysis conditions on the environment has mainly focused on the application of crop straw carbonization to farmland,and the research on the application of tea residue biochar to tea garden soil is less involved.Therefore,this paper takes tea residue as biomass raw material and pyrolyzes it into tea residue biochar at 300°C,400°C,500°C and 600°C.On this basis,the effects of soil nitrogen adsorption and desorption characteristics,soil nitrogen transformation and soil nitrogen leaching were studied by laboratory culture experiments.The main conclusions are as follows:?1?The ash,pH and C content of tea residue biochar increased with the increase of pyrolysis temperature,and the yield,H,N,O content,CEC content,specific surface area and pore volume decreased continuously.?2?The input of tea residue biochar can enhance the adsorption capacity of NH₄⁺-N in soil,and the mixed tea garden soil with 2.8%BC400 has the largest adsorption capacity of NH₄⁺-N.The CEC content of biochar is the main factor affecting the ability of soil to adsorb NH4+-N,while the specific surface area and microporous structure are weak.After the tea residue biochar is input into the soil,it can effectively reduce the desorption of NH₄⁺-N by the soil.The tea residue biochar produced at the four temperatures did not have the ability to adsorb NO₃^--N in the solution.After being input into the soil,the adsorption of NO₃^--N by the soil was reduced.?3?After the tea residue biochar is input into the soil,the pH value and total nitrogen content of the soil can be increased within a certain time range,and increase with the increase of biomass carbon addition.The soil total nitrogen content decreased with the increase of pyrolysis temperature,and the soil total nitrogen content was the highest under BC300.After the biomass charcoal was applied to the soil,the soil adsorption capacity of NH₄⁺-N increased in the pre-culture period?D1-D40,culture days?,and the soil NH₄⁺-N content increased and then gradually decreased.In the different pyrolysis temperature biochar treatment,in the early stage of culture,the NH₄⁺-N content in the low temperature biomass carbon treatment soil was lower than the high temperature,while the lower temperature treatment in the later stage was lower than the low temperature treatment.The content of NO₃^--N in all biomass charcoal treatments in the early stage of culture?D1-D3?was higher than that in the control treatment.The NO3--N content in all biomass charcoal treated soils was lower than that in the control,and the soil nitrification rate was low.In CK,biochar has an inhibitory effect on soil nitrification.The higher the pyrolysis temperature,the higher the pyrolysis temperature,the stronger the inhibition of nitrification by biomass carbon.When biochar carbon was added,the soil nitrogen conversion rate decreased significantly after the release of inorganic nitrogen,and it was lower than CK treatment,which could inhibit soil nitrogen mineralization to some extent.?4?The input of tea residue biochar into the soil can enhance the water holding capacity of the soil and reduce the volume of the soil leaching solution.At the same time,the volume of the leaching solution decreases with the increase of the amount of biomass carbon added.During the different pyrolysis temperature biochar treatment,with the increase of pyrolysis temperature,the richer the pore structure of biomass carbon,the stronger the ability to absorb water.After the tea residue biochar is applied to the soil,it can effectively reduce the leaching of NH₄⁺-N and NO₃^--N in the soil.In summary,the physical and chemical properties and structural characterization of the carbon residue of the tea residue prepared at different pyrolysis temperatures are quite different,and the effect of soil nitrogen retention is different.Compared with the tea residue biochar produced by four pyrolysis temperatures,the tea residue biochar prepared at 400°C has the best adsorption effect on soil NH₄⁺-N,and can also inhibit soil nitrification and enhance soil water holding capacity and reduce Leaching of inorganic nitrogen in the soil.Therefore,400°C tea residue biochar can be used as a tea garden soil conditioner,the optimal dosage is 2.80%,which can effectively reduce nitrogen leaching and improve nitrogen utilization efficiency after being applied to the soil.