Effects Of Biochar On Greenhouse Gas Emissions And Grain Yield From Rice Fields

Biochar is an aromatic substance with high carbon content generated by pyrolysis of biomass materials under the condition of limited oxygen or no oxygen.It is stable in nature,contains nutrients needed by a variety of plants,and is characterized by porosity and strong adsorption.Because of these special properties,biochar is widely used in agricultural production as a material to mitigate greenhouse gas emissions and improve the use of nitrogen fertilizers.In this study,the effects of biochar combined with inorganic nitrogen fertilizer on greenhouse gas emission,nitrogen fertilizer utilization rate and yield in rice field were studied through two years of field experiment,so as to provide practical basis for the application of biochar in rice production.This experiment was designed as a completely random block group,there are six treatments:?1?no nitrogen fertilizer?CK?;?2?conventional fertilization?IF?;?3?conventional nitrogen+low biochar?IF+B1?;?4?conventional nitrogen+high biochar?IF+B2?;?5?nitrogen reduction by 30%+low biochar?RIF+B1?;?6?nitrogen reduction by 30%+high biochar?RIF+B2?.The main research results are as follows:1 Biochar significantly affects soil physical and chemical properties.Compared with IF,the soil bulk density of conventional nitrogen+biochar treatment?IF+B1,IF+B2?decreased by 8.67%on average.Biochar significantly affected soil p H at seedling stage and tillering stage.Compared with IF,the p H of IF+B2 treatment increased by 0.41 on average.There was no significant increase in soil bulk density and soil p H between nitrogen reduction treatment?RIF+B1,RIF+B2?and conventional nitrogen+biochar treatment?IF+B1,IF+B2?,and between high and low biochar treatment.2 Biochar significantly increased soil nutrient content.Compared with IF treatment,the nitrate nitrogen content of conventional nitrogen+biochar treatment?IF+B1,IF+B2?increased by 53.07%on average,the ammonium nitrogen content increased by 26.07%on average,the soil DOC content increased by 131.10%on average,the soil organic matter increased by 17.52%on average,and the total soil N increased by 30.73%on average.Compared with the conventional nitrogen+biochar treatment?IF+B1,IF+B2?,the nitrate nitrogen content in the nitrogen reduction treatment?RIF+B1,RIF+B2?decreased by62.19%on average,and the ammonium nitrogen content decreased by 27.90%on average.There was no significant difference in soil nutrient content between high biochar and low biochar treatments.3 Biochar had no significant effect on CH₄emission in rice field.Compared with IF treatment,biochar combined with inorganic nitrogen significantly reduced N₂O emission in rice field by 33.55-43.05%.There was no significant difference in CH₄and N₂O emissions between nitrogen reduction+biochar treatment and conventional nitrogen+biochar treatment?IF+B1,IF+B2?,and between high biochar and low biochar treatments.4 Biochar significantly increased rice yield and nitrogen use efficiency.Compared with IF treatment,the yield of conventional nitrogen+biochar treatment?IF+B1,IF+B2?increased by 11.66%on average.There was no significant difference in yield between nitrogen reduction treatment?RIF+B1,RIF+B2?and conventional nitrogen+biochar treatment?IF+B1,IF+B2?,and between high-volume and low-volume biochar treatment.Compared with IF treatment,the nitrogen use efficiency of conventional n+biochar treatment?IF+B1,IF+B2?increased by 8.51%on average.Compared with IF+B1treatment,RIF+B1 treatment increased the nitrogen use efficiency by 11.64%on average.Compared with RIF+B1 treatment,RIF+B2 treatment reduced the nitrogen use efficiency by 11.42%on average.In summary,biochar significantly improved soil bulk density and porosity,significantly increased soil nutrient content,significantly reduced N₂O emissions from rice fields,promoted crop growth,improved nitrogen use efficiency of crops,and improved rice yield,among which RIF+B1 treatment had the best effect.