Effects Of Different Tillage Treatments On Arbuscular Mycorrhizal Fungi And Corn Growth

Various tillage methods have great impacts on agricultural production in varying degrees.Conventional tillage methods used in the northwest of China are more likely to result in further soil degradation,which exacerbates the problems during crop growth.In recent years,conservation tillage has attracted more and more attention in the northwest of China due to its unique ecological advantages.In order to explore the effects of different tillage methods on soil physical and chemical properties,growth of arbuscular mycorrhizal fungi,and nitrogen accumulation in maize,also to reveal the inherent mechanism,a series of experiments were conducted with maize under winter wheat-summer corn rotation.The experiments included three tillage treatments,namely zero tillage,chisel plow tillage,and plow tillage.The main results are given as follows:（1）Different tillage treatments affect the physical and chemical properties of the soil.This experiment was conducted to determine the soil physical and chemical at the silking period,which is vital for the colonization of AM fungi and the reproduction of maize.Among the above-mentioned three treatments,zero tillage treatment had the strongest soil water storage capacity,and its soil moisture content was increased by an average of 8.93%compared with plow tillage.Chisel plow tillage significantly increased the soil organic carbon content by an average of 32.5%in contrast with plow tillage.Under plow tillage,the soil p H and available phosphorus content were increased by 1.85%and 34.35%compared with zero tillage.（2）The growth of AM fungi and the differences during infection are the foci of this study,and tillage methods make a difference to them.In this experiment,the AM fungal biomass（spore number,hyphae density）and infection effect（infection rate,infection density,cluster abundance）were measured at the jointing stage,big trumpet stage,and spinning stage of corn.The spores number under zero tillage in the soil was the highest,respectively reaching 39,65,and 116 per 20g soil in the three periods mentioned above,with the mycelial density corresponding to 8.42 m·g^-1,11.92 m·g^-1,and 15.09 m·g^-1.As expected,AM fungal under zero tillage treatment had the strongest ability to infect maize roots,with infection rates reaching up to 17.10%,42.73%,and 72.08%respectively,followed by chisel plow tillage.Plow tillage caused the greatest damage to AM fungi,whose biomass and ability of infection were largely reduced,and it slowed the recovery and infection of AM fungi during Vegetative Stages.（3）To explore the effect of tillage treatment on the structure of AM fungal community,this experiment was carried out to extract the total DNA in the soil during the silk spinning stage for high-throughput sequencing.The sequencing result showed that four kinds of AM fungi,namely Glomus,Acaulospora,Diversispora,and Gigaspora,were found in the soil.Among them,the abundance of Glomus was the highest.At the OTU level,the AM fungus Sobs index,Shannon index,and Chao1 index in the soil under chisel plow tillage were significantly higher than that of plow tillage.（4）Based on the above studies,correlation analysis between the biomass as well as the infection effect of AM fungi and the physicochemical properties of soil was carried out,and the results showed that the physicochemical properties of soil affected the growth and reproduction of AM fungi.Among these properties,water content,p H,organic carbon content,and available phosphorus content were significantly correlated with the growth and reproduction of AM fungi.After high-throughput sequencing,redundancy analysis between sequencing results and soil factors showed that the organic carbon content and available phosphorus were the main soil factors affecting the community structure of AM fungi,with the explanation rate of organic carbon reaching 38.2%（P=0.002）and that of available phosphorus reaching 17.7%（P=0.006）.（5）In order to investigate the contribution of AM fungi to nitrogen accumulation in maize,we observed the dynamic changes of maize dry matter quality and nitrogen accumulation in this experiment,and further analyzed the gray correlation between them and the dynamic changes of AM fungi.Under chisel plow tillage,the dry matter quality of corn during maturity reached 230.51 g·plant^-1,followed by plow tillage was 217.93 g·plant^-1,and the minimum was 212.61 g·plant^-1under zero tillage.Nitrogen accumulation under chisel plow tillage reached 229.50 kg·hm^-2,and the lowest was 190.81 kg·hm^-2under zero tillage.There was no significant difference between plow tillage and the above two treatments.The gray correlation analysis showed that the correlation between the infection density and corn dry matter quality as well as nitrogen accumulation was the highest.This indicates that the dynamic change of the infection density has the highest consistency with the growth of corn,making the greatest contribution.In summary,long-term different tillage treatments made significant differences to some physical and chemical properties of the soil,changed the biomass of AM fungi in the soil as well as the infection effect on corn,also affected the growth and nitrogen absorption of maize.Under chisel plow tillage and zero tillage treatments,the biomass of AM fungi in the soil and the infection effect on corn were better than plow tillage,indicating that these two tillage treatments have a significant protective effect on AM fungi.In addition,the research results showed that chisel plow tillage protected the living environment of AM fungi,promoted its growth and infection,and could also ensure the normal growth and nitrogen absorption of corn.This conclusion has positive reference value for exerting the ecological advantages of conservation tillage.