Effects Of Biochar Application And AM Fungi Inoculation On Dryland Maize Productivity And Soil Quality And Its Mechanism

In the semi-arid rainfed agricultural area of the Loess Plateau,the low soil organic carbon content and long-term application of chemical fertilizer under the background of RF film mulching has brought serious challenges to the sustainable management of farmland ecosystems.It is an important mission in the field of agroecology to explore the basic problems of soil carbonization and fertilizer reduction.In recent years,biochar materials have demonstrated good potential in the field of soil improvement due to their special physical and chemical properties,it has been proved that biochar can improve soil fertility,water condition and plant growth.At the same time,arbuscular mycorrhizal fungi?AMF?play an active role in the growth of host plants and adaptability to drought,and the resulting microbial growth has a certain function of improving soil quality.However,the simultaneous application of biochar and AMF under furrow mulching has been rarely studied.The single and overall effects of both on soil fertility and crop productivity are unclear.Exploring their effects and mechanisms is a leading scientific issue in the field of agricultural ecology.Dry-land summer maize was used as experimental material in this study,two main treatment groups were set up:RF film mulching and no mulching,each treatment group contains two key variables:biochar and AM fungi.Eight treatments were set up,including:the RF film mulching treatment group:1)No biochar C input nor AM fungi inoculation treatment RF,2)AM fungal inoculation RFA,3)biochar C input treatment RFC,4)biochar C input and AM fungal inoculation treatment RFAC.Under plots without mulching,the following treatments were carried out:5)No biochar nor AM fungi inoculation treatment R,6)AM fungus inoculation treatment RA,7)biochar C input treatment RC,8)biochar C input and AM fungi inoculation treatment RAC.The main results were as follows:1.Under the condition of furrow mulching,biochar returning to the field significantly increased the aboveground biomass and root biomass of maize.AM fungal inoculation treatment had no significant effect on the aboveground biomass of maize but significantly increased the root biomass.In 2018,RFA,RFC,and RFAC treatments increased 0.63%,11.93%,and 16.61%of aboveground biomass,respectively,and root biomass increased by 13.46%,18.15%,and 14.74%,respectively.The trend was the same in 2019.The application of biochar in 2019 increased the ear length,ear thickness,number of grains and 100-grain weight of corn.RFC treatment increased by 7.76%,13.36%,11.89%,and 10.89%respectively compared with the control RF treatment.Both AM fungal inoculation treatment and biochar application significantly increased corn grain yield,and the interaction between AM fungal inoculation treatment and biochar application on maize grain yield was significant.RFA,RFC,and RFAC treatments in 2019 compared to control RF treatments Increased by 4.24%,16.13%,and 25.81%respectively.2.In this experiment,the application of biochar and AM fungi inoculation was beneficial to increase the soil water content,but the difference was not significant compared with RF treatment.The effect of RF film mulching measures on maintaining surface soil moisture was superior to biochar and AM fungi treatments.The soil moisture content of the 0-20 cm soil layer in the maturity period in 2018 was 61.42%and 75.21%higher than the RC in ridge and furrow film treatment and the RA with the non-film treatment,respectively.The soil water content of the RFC treatment in2018 was significantly lower than that of RF,and the soil water content of RFC in the mature stage in 2019 was higher than RF,which shows that the impact of biochar returning to the soil on soil moisture requires a longer time to reflect,and the longer time dimension to accurately reflect the impact of biochar on soil water holding capacity.3.The application of biochar significantly reduced the soil bulk density.Under the conditions of this experiment,in the 0-20 cm soil layer,the addition of biochar reduced the soil bulk density by 13.54%,11.78%,5.41%and 7.69%in RFC,RFAC,RC and RAC,respectively.The ridge and furrow film mulching measures also helped to reduce the magnitude of soil bulk density increment.The mechanical compaction of the soil surface layer by rainfall and other external forces led to a larger increase in bulk density in plots without mulching as compared with mulched plots.In addition to the advantages of the film mulching measures,bulk density reduction helps to integrate the dilution effect of biochar blending.4.When there is a significant difference between the pH of the biochar and the soil,the soil pH will change after the biochar application due to physical blending and dilution effects.In this experiment,biochar with a pH of 7.91 was used to decrease the pH of the topsoil with a pH of 8.15by 0.14-0.16.The return of biochar to the field with a lower pH lowers the pH of the soil with high pH,providing good conditions for the growth and development of crops and AM fungi.At the same time,the pH of the treatments with biochar was higher in 2019 than in 2018,but compared with the treatment without biochar,the pH did not increase significantly,which had a certain inhibitory effect on the secondary salinization of the soil.5.In this experiment,the application of biochar significantly increased the soil organic carbon content of the surface soil.In 2018,RFC and RFAC treatments increased by 28.12%and 27.30%as compared with RF.RC and RAC increased by 10.43%and 9.59%as compared with R.In the 0-20cm soil layer in 2019,RFC and RFAC increased by 17.26%and 18.62%compared with the RF,whereas RC and RAC increased by 6.69%and 7.98%compared with R.Under the condition of furrow mulching,AM fungal inoculation treatment increased the soil organic carbon content of the0-20 cm soil layer.In 2018,the RFA increased the SOC content by 19.25%compared to the control RF treatment.The SOC content of the inoculation treatment increased without mulching,but the SOC content of RA treatment increased by 1.16%compared with the R.The interaction between biochar application and AM fungal inoculation treatment on SOC content was significant at P<0.05.In 2019,the SOC content of RFAC treatment increased by 18.93%as compared to RFA,and the SOC content of RFA increased by 12.48%compared to RA treatment.6.The application of biochar tends to increase soil total nitrogen and nitrate nitrogen content.In 2018,the TN content of the biochar treatment was not significantly different from the control treatment.In 2019,the TN content of the RFC treatment was significantly higher than the control treatment RF,and the RC treatment was significantly higher than the control treatment R.The application of biochar has a long-term effect on soil physical and chemical factors.In the maturity stage,the soil in the 0-20 cm soil layer in 2018,had a significantly higher NO₃^--N content in RFC and RC treatment compared with RF and R.At the same time,the content of nitrate nitrogen in RFAC was significantly less than that of RFC,whereasand the content of nitrate nitrogen in RAC was less than that of RC.It may be that the presence of AM fungi makes the soil inorganic nitrogen transfer more to plants and AM fungi,helping the host plant absorb more inorganic nitrogen.This leads to a reduction in soil inorganic nitrogen content.7.The inoculation treatment of AM fungi and the application of biochar can increase the soil total phosphorus content,but the interaction between the two on soil total phosphorus content is not significant.In 2019,the total phosphorus content of RFC and RFA treatments increased by 18.47%and 18.36%compared with the control treatment.The total phosphorus content of RC and RA treatments increased by 19.35%and 23.58%compared with the control treatment.Biochar application can significantly increase the soil available phosphorus content.In 2018,the content of AP in RFC treatment increased by 29.21%compared with the control RF treatment.In 2019,the content of AP in RFC treatment increased by 16.04%compared with the control RF treatment.In2018 and 2019,the impact of biochar on the soil available phosphorus content is the same but there are differences.Therefore,the impact of biochar on soil physical and chemical factors has a long-term effect,which needs to be evaluated on a longer time scale.8.Under the conditions of mulching and non-mulching,the treatment with added biochar has significant effects on the soil microbial carbon and microbial nitrogen content and the interaction between the treatments is significant.In 2018,the MBC content of RFA,RFC,and RFAC treatments increased by 24.85%,21.94%,and 43.21%,respectively,compared with the control RF treatment.The trend is the same in 2019.In 2018,the MBA content of RFA,RFC,and RFAC treatments increased by 42.61%,45.75%,and 69.18%respectively compared with the control RF treatment.The trend in 2019 is the same as in 2018.In 2019,AM fungal inoculation treatment and biochar return to the field both significantly increased soil spore density and the content of easy-to-extract globinin in the soil.Biochar return to the field increased the infection rate of AM fungus roots but was not significant.In summary,under the field conditions in the semi-arid area of the Loess Plateau,biochar application can improve soil structure and retain soil nutrients,thereby promoting crop growth and helping to increase crop yields.The inoculation treatment of AM fungi and the application of biochar have a synergistic effect in maintaining soil moisture and maintaining and improving soil quality,which verifies the feasibility of the biochar and AM fungus coupling system to increase crop yields.It is worth noting that the effect of co-application of biochar and AM fungi on soil quality is not completely consistent,and the conclusions between different years are different.Therefore,it is necessary to carry out multi-year,multi-point series experiments.The aftereffects need to be further evaluated.