| Citrus as one of the main cultivated fruit trees in China,plays an important role in rural revitalization and rural economic development,however,at present,the soil in China’s citrus industry production area is mostly acidic soil,coupled with short citrus root system and sparse root hair,difficult to absorb nutrients,and abuse of chemical fertilizers in cultivation management,so that soil compaction,fertility decline,rhizosphere soil microbial decline,seriously affecting the yield and quality of citrus.It is imperative to improve the soil,reduce the application of chemical fertilizers,increase the absorption of nutrients by citrus roots,and improve citrus yield and quality.Arbuscular Mycorrhiza fungi(AMF)is a fungus that exists in nature and is symbiotic with citrus roots,which can improve soil conditions,promote the absorption of mineral nutrients by citrus,and improve stress resistance.Biochar and humic acid are widely used in agricultural production as a new type of green organic fertilizer,which can improve the soil environment and promote the growth and development of plants.With the application of biochar and humic acid in agricultural production,it has a certain impact on rhizosphere soil microorganisms,and studies have shown that biochar and humic acid have a certain impact on AMF,and the combined application can promote the growth and development of plants and improve the soil environment.However,the current research is limited to the effects of single inoculation of AMF and biochar humic acid on plant growth and soil,and there are few studies on the co-benefits between citrus.The effects of the combined benefits of biochar,humic acid and AMF on citrus were studied,which provided a theoretical basis for promoting nutrient absorption,improving fertilizer utilization and ecological development in the actual production and cultivation of citrus.In this study,the annual seedlings of Orah(Citrus reticulata Blanco)/Citrus junos Sieb.Ex Tanaka)was used as the test material,the AMF fungal dominant strain Glomus etunicatum was used as the test agent,and biochar(Biochar,BC)and Humic Acid(HA)were used as the test reagents.The design was based on unvaccinated AMF and CK without BC and HA treatment,uninoculated treatment(BC,HA and BC+HA alone),inoculation treatment(AMF,BC+AMF,HA+AMF,BC+HA+AMF),this trial adopted a random distribution method,and three repeated tests were carried out to study the growth and development of citrus seedlings,mineral nutrition,physiological metabolism,endogenous hormones,rhizosphere soil,etc.The main conclusions are as follows:1.Vaccination with AMF can effectively infect the root system of citrus seedlings,and the addition of BC and HA under the treatment of AMF can increase the infection rate of mycorrhizae,among which the infection rate of M+BC+HA treatment is the highest.2.Vaccination with AMF significantly improved the root growth,root-to-head ratio,biomass accumulation,root viability,number of first-class new roots,plant height and mycorrhizal dependence of citrus seedlings.Under the inoculation AMF treatment,and then adding BC and HA treatment,the growth level of citrus seedlings was significantly improved,and the photosynthetic gas exchange parameters and chlorophyll content were also significantly improved.The contents of nutrients(organic matter,total nitrogen,total potassium,total phosphorus,nitrate nitrogen)in the leaves and roots of citrus seedlings were better than those of single application,and the effect of M+BC+HA treatment was better.3.Under AMF inoculation,the physiological metabolism of leaves and roots of citrus seedlings was significantly improved,the accumulation of soluble sugars,soluble proteins and proline was also promoted,the concentration of MDA(malondialdehyde)was also reduced,and the antioxidant enzyme activity of citrus seedlings was improved,so that the antioxidant power of citrus seedlings was significantly improved.The treatment of adding BC and HA(M+HA,M+BC,M+BC+HA)was better than that of AMF alone,and could improve the antioxidant capacity of citrus seedlings,among which M+BC+HA was better.4.Under the treatment of AMF inoculation,the content of endogenous hormones(IAA,GAs)and ABA content of citrus seedlings can be significantly increased,and the content of strigolactone hormone(SLS)of citrus seedlings can be promoted,and the treatment of BC and HA(M+HA,M+BC,M+BC+HA)is better than that of unvaccinated treatment and single inoculation AMF treatment,among which M+BC+HA treatment is better.5.Under the treatment of AMF inoculation,the p H of rhizosphere soil can be reduced,the content of mineral nutrients in rhizosphere soil,the activity of urease,catalase and polyphenol oxidase in rhizosphere soil can be significantly increased,and the microbial community in rhizosphere soil can be changed,which is conducive to the growth and development of citrus seedlings.6.Comprehensive analysis found that there were certain differences in citrus seedlings and rhizosphere soil between different treatments,and the treatment effect of BC+HA combined with BC+HA had a better effect on the growth and development of citrus seedlings,and could improve the antioxidant capacity and endogenous hormone synthesis of citrus seedlings.The nutrients,enzyme activities and microbial communities of rhizosphere soil are more conducive to changing the soil environment,stabilizing the soil,and more conducive to the growth and development of citrus seedlings.It can also promote the formation of a good symbiotic structure between AMF and citrus seedling roots.Therefore,the combination of M+BC+HA is the best treatment in this experiment,and has certain application potential in the actual production and cultivation of citrus. |
