Effects Of Long-term Biochar Application On The Community Structure And Colonization Of Mycorrhizal Fungi In Brown Soils

Arbuscular mycorrhizal fungi（AMF）can form mycorrhizal symbiotes with most terrestrial plants to assist host plants in nutrient uptake,stabilize soil structure,enhance the resistance of host plants to stress and diseases and pests.The formation of mycorrhizal symbiotes and the growth and development of AMF in farmland ecosystems are affected by the soil ecological environment of farmland,and different soil types,host crops,fertilizer types and application amounts will change the community structure of AMF.Biochar as a soil conditioner can improve soil nutrient conditions and soil structure,and the application of biochar is bound to cause AMF response to changes in the soil environment.At present,there are few studies at home and abroad on the community structure change of brown soil AMF under the condition of long-term biochar application,and 6 experimental treatments were selected based on the application of biochar in brown soil for 8 consecutive years:CK（no fertilization）,NPK（chemical nitrogen,phosphorus and potassium fertilizer）,C₁（1.5 t/hm² biochar）,C₃（6 t/hm²biochar）,C₁NPK（1.5 t/hm² biochar with chemical nitrogen,phosphorus and potassium fertilizer）,C₃NPK（6 t/hm² biochar with chemical nitrogen,phosphorus and potassium fertilizer）,By analyzing the community structure of AMF in different treatments by high-throughput sequencing technology,combining the characteristics of soil nutrients,maize nutrient uptake,soil AMF spore density,and maize root AMF inf infection rate of different treatments,exploring the changes in the AMF community structure of brown soil under long-term biochar application and identifying key influencing factors can regulate the AMF community structure,thereby providing a theoretical basis for promoting efficient nutrient utilization and rational fertilization.The test results show that:1.Long-term application of biochar has a significant impact on the changes in soil quick-available nutrient and total nutrient content,and improves soil fertilizer retention capacity,water retention capacity and soil p H.The nutrient content of the soil treated without chemical fertilizer is low,and the role of biochar as an exogenous nutrient is more significant.2.The effect of long-term application of biochar on changes in soil nutrient content was related to the adsorption and desorption of nutrients by biochar.The soil nutrient content levels are different,resulting in differences in the effect of long-term application of biochar on the change of soil nutrient content,and the change of seasonal nutrient content in the soil with long-term application of chemical fertilizer is related to the cumulative application of biochar and the amount of seasonal application,and long-term application of biochar is conducive to improving fertilizer utilization rate.3.Long-term application of biochar promotes the nutrient absorption of maize and improves maize yield.In the medium and long-term application of biochar in the treatment of no chemical fertilizer,the long-term application of biochar promoted the nutrient absorption of maize to a certain extent,and did not significantly promote the yield of maize,the amount dry matter of maize was mainly affected by the accumulation of phosphorus and potassium nutrients,while the yield was mainly affected by the nitrogen nutrient accumulation;the long-term application of biochar in the medium and long term of chemical fertilizer treatment had a significant role in promoting the yield of maize,and the amount and yield of maize dry matter were mainly affected by the accumulation of nitrogen nutrients.4.Long-term application of biochar increased the diversity of AMF communities in maize cropland ecosystems,and Glomus is the genera-level strain with the largest relative abundance of AMF communities in soil and roots.Chemical fertilizer application significantly reduced AMF diversity,while long-term combined biochar significantly increased AMF community diversity compared with chemical fertilizer alone.As maize grows and develops,the relative abundance of Glomus in soil and maize roots can reach 90%and above.5.Long-term application of biochar promotes soil AMF spore propagation and maize root AMF colonization by regulating soil nutrient content,while inhibiting soil AMF spore reproduction and maize root AMF colonization by increasing soil p H and water content.Under the combined effect,long-term biochar application significantly increased soil AMF spore density,and had no significant effect on the colonization of maize root AMF.6.The AMF genus level species that contributes the most to the nutrient uptake of maize in maize crop ecosystems is Glomus,and other AM strains have no significant correlation with maize nutrient uptake.Long-term application of biochar had a certain degree of promotion effect on the relative abundance of Glomus by influencing the soil nutrient content,while the relative abundance of Glomus was inhibited by influencing other physical and chemical properties of the soil（especially increasing the soil p H）,and the relative abundance of root Glomus was significantly higher in the C₃NPK treatment during the growth and development of maize.Long-term biochar application had a certain degree of promoting nutrient uptake in maize treated with chemical fertilizers by regulating root AMF community diversity and relative abundance of Glomus,while by regulating AMF community diversity inhibited nutrient uptake in maize treated without chemical fertilizer to a certain degree.In summary,long-term biochar application has a certain degree of impact on the AMF community structure,soil AMF spore density,and root AMF colonization and infestation status of maize cropland ecosystems by influencing soil physicochemical properties,and Glomus is the dominant species of AMF.AMF community diversity,soil AMF spore density and root AMF colonization infestation rate can be improved by screening biochar that is more suitable for AMF growth and development and adjusting the amount of biochar application,which can help weight loss and efficiency and sustainable agricultural development.