Effects Of Arbuscular Mycorrhizal Fungi And Organic Materials On Plant Growth And Nutrient Leaching Loss In Legume-Grass Mixed Grassland

Excessive and unreasonable application of chemical fertilizers has caused a series of serious environmental problems.Therefore,there is an urgent need to improve fertilization methods,reduce unnecessary inputs,and promote sustainable agricultural development.At present,organic materials such as straw and manure are used to replace chemical fertilizers to increase plant yields and improve soil structure.Arbuscular mycorrhizal fungi（AMF）can form a symbiotic relationship with most terrestrial plants.On the one hand,AMF can promote the absorption and utilization of nutrients such as nitrogen（N）and phosphorus（P）by plants,on the other hand,it can improves the degradation of organic matter by affecting the activities of other microorganisms in the soil,which affects the content of effective nitrogen and available phosphorus.This study explored the effects of AMF and organic materials on plant growth and nutrient loss through leaching in legume-grass mixed grassland under different leaching levels and nitrogen application levels through two greenhouse soil column experiments.1.Effects of arbuscular mycorrhizal fungi and organic fertilizer on plant growth and nutrient leaching loss in legume-grass mixed grassland at different leaching levelsThis experiment set three factors:AMF,organic fertilizer（OF）and leaching amount.Among them,AMF includes two treatments（un-inoculated AMF（-AMF）and inoculated AMF（+AMF））,organic fertilizer includes two treatments（without organic fertilizer（-OF）or with organic fertilizer（+OF））,leaching amount includes two treatments（low water leaching amount（L,720 mL/each time）and high water leaching amount（H:1440 mL/each time））.The main results are as follows:（1）Compared to the treatment without organic fertilizer,the treatment with organic fertilizer significantly reduced mycorrhizal colonization rate under low water leaching amount or high water leaching amount treatment.（2）The addition of OF significantly increased the aboveground biomass of each species,total aboveground biomass,underground biomass and total biomass,and reduced the proportion of root biomass.The total biomass showed the highest value in the L+AMF+OF treatment.（3）Compared to the treatment without organic fertilizer,the treatment with organic fertilizer significantly increased the ammonium nitrogen（NH4+-N）,nitrate nitrogen（NO3--N）and total dissolved nitrogen（TDN）concentrations in soil in the low water leaching amount treatments.（4）Compared with high water leaching amount treatment,low water leaching amount treatment significantly reduced the NH4+-N,available phosphorus,dissolved organic carbon（DOC）and TDN amount of leachate.When organic fertilizer was applied,AMF significantly reduced the available phosphorus amount of leachate in the low water leaching amount treatment.2.Effects of arbuscular mycorrhizal fungi and biochar on plant growth and nutrient leaching loss in legume-grass mixed grassland at different nitrogen application levelsThis experiment set three factors:AMF,biochar（BC）and nitrogen fertilizer.Among them,AMF includes two treatments（un-inoculated AMF（-AMF）and inoculated AMF（+AMF））,biochar includes two treatments（without biochar（-BC）or with biochar（+BC））,nitrogen fertilizer includes three levels(5 mg N kg-1（L）,30 mg N kg-1（M）and 60 mg N kg-1（H）.The main results are as follows:（1）Nitrogen fertilizer and biochar have a significant interaction effect on mycorrhizal colonization.In 5 mg N kg-1 and 60 mg N kg-1 treatments,BC had no significant effect on the AMF colonization rate.In 30 mg N kg-1 treatment,biochar significantly reduced AMF colonizotion rate.（2）BC had no significant effect on total biomass in the low N and high N application treatments.In the moderate N application treatment,BC significantly increased total biomass.There was no significant difference between moderate and high N application treatments.（3）Compared with the uninoculated treatment,those inoculated with AMF showed increases of the proportion of legumes in the total biomass.（4）Compared with low and moderate N application treatments,high N application treatment significantly increased the NO3--N and TDN amount of leachate.In summary,（1）In legume-grass mixed grassland,the addition of organic fertilizer significantly increased plant biomass and nitrogen leaching loss.When organic fertilizerwas applied,AMF inoculation promoted the growth and reduced the available phosphorus leaching loss in the low water leaching amount treatment.Compared with low water leaching amount treatment,high water leaching amount treatment caused a large leaching loss of dissolved organic carbon,tatal dissolved nitrogen and available phosphorus.（2）In the presence of AMF and biochar,the appropriate reduction of the amount of nitrogen fertilizer did not reduce plant yield.