Effects Of Nitrogen Application Rate On Growth And Development Of Peanut And Bacterial Diversity In Rhizosphere Soil

In recent years,in order to ensure crop yield,the application amount of nitrogen fertilizer is increasing in agricultural production,while the utilization rate of nitrogen fertilizer is at a low level.Excessive application of nitrogen fertilizer will lead to a variety of environmental problems,and will have a profound impact on the soil itself.In particular,soil microorganisms will change in structure with the increase of nitrogen fertilizer application years.In this study,the high oleic acid peanut“Jihua 16”was used as the research material.The randomized block test was used to set LN(0 kg/hm~2,CK),MN(120 kg/hm~2)and HN(240 kg/hm~2)three nitrogen levels to determine the growth and development indexes at different growth stages,yield and quality.The high-throughput sequencing technology was used to analyze the composition and diversity of rhizosphere bacterial community at different growth stages,in order to provide theoretical basis for efficient production of peanut.The main research results are as follows:(1)The main stem height and the first lateral branch length of peanut increased to varying degrees with the increase of nitrogen application rate.The chlorophyll content of leaves was significantly positively correlated with nitrogen application rate at seedling stage,and there was no significant difference at other growth stages.Leaf GS activity was higher than other treatments in the whole growth period under MN treatment;The GDH activity of HN treatment was significantly lower than that of other treatments at seedling stage,flower needle stage and pod setting stage.The activities of GS,GDH and GOGAT were MN>HN>LN in mature stage,and leaf SP content in HN treatment was lower than other treatments during the whole growth period.The total accumulation of total nitrogen,potassium and calcium in seedling stage increased significantly with the increase of nitrogen application rate,and there was no significant difference in total phosphorus accumulation in various organs.The total accumulation of total nitrogen,total phosphorus,potassium and calcium in mature stage was positively correlated with nitrogen application rate,and seed kernels played a major role in the accumulation of total nitrogen and total phosphorus.The accumulation of total calcium in plants was leaf>stem>root>pod during the whole growth period.The full fruit number,full fruit weight and full kernel weight of HN treatment were significantly higher than those of MN and LN treatment.The pod yield of MN and HN treatment was 13.58%and 50.89%higher than that of LN treatment,respectively.The content of oleic acid and linoleic acid in kernel was 6.46%,49.67%and 6.00%,43.46%higher than that of LN treatment.(2)The dominant bacterial phyla in all rhizosphere soil samples were Proteobacteria,Acidobacteria,Chloroflexi,Actinobacteria,Gemmatimonadetes,Bacteroidetes and Verrucomicrobia.Nitrogen application rate had a great influence on the rhizosphere bacterial community structure of peanut at seedling stage.The increase of nitrogen application rate at seedling stage reduced the abundance of Acidobacteria,Bacteroidetes and Planctomycetes,and increased the abundance of Actinobacteria and Gemmatimonadetes.Theαdiversity under HN treatment was significantly reduced,and pH value and AN had a significant influence on the community structure.The abundance of Acidobacteria and Chloroflexi was higher at pod setting stage.TP,AP and ECa had significant effects on community structure.The explanation rates of nitrogen application rate and growth period to rhizosphere bacterial community structure in the whole growth period were 7.51%and 10.17%,respectively,and the samples were more inclined to cluster according to growth stages.At seedling stage and mature stage,only the abundance of Nitrosomonadaceae and its subordinate Nitrosospira genus and Pseudolabrys under HN treatment significantly increased,which could be used as Biomarker under different nitrogen rates to explain the effect of nitrogen application on the rhizosphere bacterial community structure of peanut to some extent.