The Effect Of Exogenous Glucose On Soil Organic Carbon Content And Nitrogen Metabolism In Root Of Malus Baccata Borkh.

SOC plays an important role in soil fertility.Apple orchards are built on mountains and hills with poor soils quality in China.And long-term excessive nitrogen application results in decreasing of nitrogen absorption of plant in soil.Exogenous carbon source is a beneficial method to enhance soil fertility,promote absorption of nitrogen in plant,and improve the efficiency of nitrogen fertilizer.Therefore,in this study,the typical low carbon gravel soil and clay soil in Liaoning Province were selected as substrate.Malus Baccata Borkh.serve as materials.The glucose-C equal to soil original microbial biomass carbon(MBC)(G1)and 5 times(G2)were used to study the effect of exogenous carbon source on soil organic carbon turnover,plant growth and nitrogen metabolisn in root of Malus Baccata Borkh..The main results are as follows: 1.The effects of exogenous glucose on soil organic carbon turnover.The SOM,MBC,ROC,DOC and POC contents in gravel and clay soil were significantly increased by the glucose.And exhibit a time trend: first increased and then decreased.G1 exhibited most positive effcts on gravel soil,while in clay soil was G2 treatment.The activity of soil enzyme was promoted by exogenous glucose in both gravel and clay soil.β-glucase,invertase and amylase activity were increased higher by G1 treatment than either G2 treatment or CK,in gravel soil.in clay soil,β-glucase,invertase and amylase activity were increased more significant by G2 treatment than G1 treatment.2.The effects of exogenous glucose on functional diversity of soil microbialAverage well color development(AWCD)of soil microbial was increased significantly by exogenous glucose in both gravel and clay soil.In the gravel soil,Shannon,Simpson,Mclntosh index and the utilization of six kinds of carbon source of soil microorganisms were significantly improved by G1 treatment in gravel soil.Which means soil microbial community structure was mostly induced by G1 than G2 in gravelsoil.In clay soil,Shannon index was significantly enhanced by glucose treatments,while no significant difference between G2 and G1.The Simpson and Mclntosh index,and the utilization of six kinds of carbon source were improved significantly higher by G2 than G1 treatment.All these indicated that microbial functional diversity was easily improved by G2 in clay soil.3.The effects of exogenous glucose on plant growth and nitrogen metabolism of Malus baccataThe growth of Malus Baccata Borkh in graveland clay soil were significantly promoted by glucose treatment.Total root length,root volume,root surface area were increased,biomass accumulation were promoted and photosynthetic capacity were enhanced by G1 treatment more significantly than G2 in gravel soil,while in clay soil is G2 prsented higher positive effects than G1.The nitrate nitrogen,nitrite nitrogen and ammonium nitrogen content were significantly changed,and nitrogen metabolism enzyme activity were improved by glucose treatment in root of Malus Baccata Borkh.in two kinds of soil.NR,GS,GOGAT,GDH,GPT and GOT activities were promoted more effective by G1 than G2 in gravel soil,which means the absorption and assimilation of nitrogen were effectively promoted by G1,and promots the transformation from inorganic nitrogen to organic nitrogen,however,G2 treatment showed mostly effective effects in clay soil.