【作者】 李颖；

【导师】 李淑敏；

【作者基本信息】 东北农业大学 ， 土壤学， 2021， 硕士

【摘要】 间作种植模式是我国农业可持续发展的重要组成部分。研究豆科/非豆科间作体系中豆科的固氮效率,对进一步提升间作体系氮肥利用率有重要意义。但是关于不同供氮水平调控玉米/大豆间作体系中的大豆固氮效率与根际土壤固氮微生物多样性以及nifH基因拷贝数量关系的研究还不够深入。因此,本次试验以玉米/大豆间作体系为研究对象,设置四个施氮水平,采用田间裂区设计,通过¹⁵N自然丰度法,探究在不同供氮水平下,玉米/大豆间作体系中大豆固氮效率和固氮量的变化,同时利用高通量测序和q PCR方法揭示作物种间互作驱动根际土壤固氮菌多样性、群落结构和nifH基因拷贝数量的变化规律,从根际固氮菌角度阐述了供氮水平调控玉米/大豆间作体系固氮效率变化规律以及与根际固氮微生物多样性关系。研究结果为优化间作体系氮肥管理和减施氮肥提供理论依据。主要结果如下:供氮水平显著影响了玉米和大豆生物量,随施氮水平的增加而显著增加,均在N2处理达到最大;间作显著影响了玉米和大豆的生物量,在N0(0kg N ha^-1)、N1(120kg N ha^-1)、N2(240kg N ha^-1)和N3(300kg N ha^-1)处理下,间作玉米生物量分别比相应的单作增加了45.4%、16.6%、7.1%和7.4%,间作大豆生物量在N0(0kg N ha^-1)、N1(40kg N ha^-1)、N2(80kg N ha^-1)和N3(120kg N ha^-1)处理下,分别比相应单作降低了25.3%、26.1%、26.5%和20.2%。玉米和大豆含氮量随供氮水平的增加而显著增加,在N2处理达到最大;间作使玉米各器官含氮量显著高于单作,在N0、N1、N2和N3处理下,间作玉米茎中的含氮量是相应单作的1.05、1.06、1.05和1.06倍,叶片含氮量是单作的1.07、1.02、1.04和1.08倍,籽粒含氮量是单作的1.03、1.04、1.04和1.04倍;间作显著降低了大豆茎的含氮量,对叶片和籽粒没有显著影响。供氮水平显著增加了玉米和大豆各器官的吸氮量,均在N2处理最大;间作显著影响了玉米和大豆的吸氮量,其中间作玉米各器官的吸氮量在N0、N1、N2和N3处理下显著高于单作,然而间作使大豆叶片和茎秆吸氮量显著低于相应的单作,在N0、N1、N2和N3处理下,间作大豆叶片吸氮量比单作低30.7%、43.8%、39.6%和32.7%,籽粒吸氮量比单作降低了28.8%、22.5%、6.1%、21.1%。玉米和大豆植株总吸氮量受供氮水平影响显著,随供氮水平的增加而显著增加,在N2处理达到最大;在N0、N1、N2和N3处理下,间作玉米总吸氮量比相应单作增加了56.6%、22.7%、13.9%和15.9%,而间作大豆植株总吸氮量比单作降低了27.2%、22.7%、26.5%和21.1%。系统总吸氮量随着供氮水平的增加而显著增加,在N2施氮处理最高,间作降低了系统总吸氮量,在N0、N1、N2和N3施氮处理下,间作比相应的单作降低了3.6%、1.3%、6.2%和2.2%。大豆固氮效率受供氮水平和种植模式影响。供氮水平的增加显著抑制了大豆固氮效率,在N3处理最低,间作显著增加了大豆固氮效率,N0、N1、N2和N3处理下大豆固氮效率比相应单作增加了26.2%、26.1%、10.0%、10.3%。固氮量受施氮量影响显著,在N1处理最高,N3处理最低。随着施氮水平的增加大豆根瘤数量与干重显著下降,在N3处理最低,在N0、N1、N2和N3处理下,间作大豆根瘤数量分别比相应单作增加了11.2%、27.4%、26.8%和16.3%。玉米根际固氮菌Alpha多样性指数随供氮水平的增加而显著增加,在N3处理最高,但是大豆根际固氮菌多样性指数随供氮水平的增加而显著降低;间作对玉米根际固氮菌多样性无显著影响,但显著增加了大豆根际固氮菌多样性指数。在属水平下,慢生根瘤菌属（Bradyrhizobium）为玉米和大豆根际固氮菌的主要优势菌属,所占相对丰度最高,其次是斯科曼氏菌属（Skermanella）、unclassified＿p＿Proteobacteria、产碱菌属（Azohydromonas）、unclassified＿k＿＿norank＿d＿＿Bacteria,这些菌属在玉米和大豆根际土壤中所占丰度之和达到85%以上。在玉米根际土壤中,慢生根瘤菌属（Bradyrhizobium）受供氮水平影响显著,随供氮水平的增加而下降。RDA结果表明,玉米根际土壤固氮菌群落结构与土壤p H（p=0.002）、AN（p=0.024）含量有显著相关性,大豆根际土壤固氮菌群落结构与土壤各理化因子含量相关性不显著。供氮水平显著影响了玉米和大豆的固氮基因（nifH）拷贝数,其中玉米固氮基因（nifH）拷贝数量随供氮水平的增加而下降,在N3处理最低;大豆固氮基因（nifH）数量在N1处理达到最大值,为6.25×10⁷copies·g^-1。间作种植模式对玉米和大豆固氮基因（nifH）拷贝数量没有显著影响。相关分析结果表明固氮基因（nifH）拷贝数与土壤速效氮呈显著负相关,与大豆固氮量呈正相关关系。更多还原

【Abstract】 Intercropping is an important part of sustainable agricultural development in China.Study legumes nitrogen fixation efficiency have great significance to further improve nitrogen utilization in the legumes/nonlegumes intercropping system.However,about study relationship between soybean nitrogen fixation efficiency and rhizosphere soil nitrogen fixation microorganism diversity and nifH gene copies have not been indepth enough in the maize/soybean intercropping system with different nitrogen levels.Therefore,maize/soybean intercropping system was taken as the research object in this experiment,set four nitrogen application levels,adopt the design of field split area,by ¹⁵N natural abundance method,explore the changes of nitrogen fixation efficiency and nitrogen fixation amount of soybean in maize/soybean intercropping system with different nitrogen levels,use High-throughput sequencing and q PCR were used to reveal the variation patterns of nitrogen-fixing bacteria diversity,community structure and nifH gene copies in rhizosphere soil driven by interspecific interactions,according to nitrogen fixing microorganisms discussed nitrogen fixation efficiency and its relationship with the diversity of nitrogen fixation microorganisms in the rhizosphere by maize/soybean intercropping system with nitrogen supply levels.The results provided a theoretical basis for optimizing nitrogen management and reducing nitrogen application in intercropping system.The results as follows:The biomass of maize and soybean was significantly affected by nitrogen levels,which increased with nitrogen application levels,and reached the maximum in N2 treatment;intercropping have significant effects to maize and soybean biomass,at N0(0kg N ha^-1),N1(120kg N ha^-1),N2(240kg N ha^-1)and N3(300kg N ha^-1)treatments,maize intercropped biomass increased by 45.4%,16.6%,7.1%and 7.4%,respectively,compared with the corresponding monocropped maize;soybean intercropped biomass increased by 25.3%,26.1%,26.5%and 20.2%in N0(0kg N ha^-1),N1(40kg N ha^-1),N2(80kg N ha^-1)and N3(120kg N ha^-1)treatments.The nitrogen content of maize and soybean increased significantly with the nitrogen supply levels,and reached the maximum in N2 treatment;intercropping made maize organsnitrogen content significantly higher than in monoculture,under the N0,N1,N2 and N3 treatments,intercropping maize stem nitrogen content was 1.05,1.06,1.05 and 1.06 times of that of corresponding monoculture;intercropping maize leaf nitrogen content was 1.07,1.02,1.04 and1.08 times of that of corresponding monoculture;intercropping maize grain nitrogen content was1.03,1.04,1.04 and 1.04 times of that of corresponding monoculture.Intercropping significantly reduced the nitrogen content of soybean stem,but had no significant effect on leaf and grain.The nitrogen supply levels significantly increased the nitrogen uptake in each organ of maize and soybean,and the maximum nitrogen uptake was observed in N2 treatment;The nitrogen uptake of maize and soybean was significantly affected by intercropping.The nitrogen uptake of maize organs under N0,N1,N2 and N3 treatments was significantly higher than monocropping treatments.However,nitrogen uptakeleaves and stems of intercropping soybean was significantly lower than monocropping treatments.Intercropping soybean leaf nitrogen uptake was 30.7%,3.8%,39.6%and 32.7%lower than that of monocropping soybean,and the grain nitrogen uptake was28.8%,22.5%,6.1%and 21.1%lower than that of monocropping soybean.The total nitrogen uptake by maize and soybean plants was significantly affected by nitrogen supply levels,and increased with the nitrogen supply levels,and reached the maximum in N2 treatment.Under N0,N1,N2 and N3 treatments,maize total nitrogen uptake increased by 56.6%,22.7%,13.9%and15.9%,while soybean total nitrogen uptake decreased by 27.2%,22.7%,26.5%and 21.1%compared with monocropping.In the system,total nitrogen uptake increased significantly with nitrogen supply levels,but in N0,N1,N2 and N3 treatments,total nitrogen uptake was decreased by 3.6%,1.3%,6.2%and 2.2%compared with the corresponding monocropping treatments.Soybean nitrogen fixation efficiency was significantly affected by nitrogen supply levels and planting pattern.The nitrogen fixation efficiency of soybean was significantly inhibited by the nitrogen levels increased,and the soybean nitrogen fixation efficiency was significantly increased by N0,N1,N2 and N3 treatments,which were 26.2%,26.1%,10.0%and 10.3%higher than that of the corresponding monocrops.Nitrogen fixation amounts was significantly affected by nitrogen application levels,the highest in N1 treatment and the lowest in N3 treatment.Soybean nodules and dry weight decreased significantly with the nitrogen application levels,and the lowest in N3 treatment.Compared with monocropping,under N0,N1,N2 and N3 treatments,intercropping nodules increased 11.2%,27.4%,26.8%and 16.3%,respectively.The nitrogen fixing bacteria Alpha diversity index in maize rhizosphere increased signi ficantly with the nitrogen supply levels,and reached the highest in N3 treatment.However,nitrogen fixing bacteria Alpha diversity index in soybean rhizosphere decreased significantly with the nitrogen supply levels.Intercropping had no significant effect on the nitrogen fix ing bacteria diversity in maize rhizosphere,but significantly increased the nitrogen fixing b acteria diversity index in soybean rhizosphere.At the genus levels,Bradyrhizobium was t he dominant genus of nitrogen fixing bacteria in maize and soybeanthe rhizosphere,and it had the highest relative abundance.It was followed by Skermanella,Unclassified＿P＿Proteo bacteria,Azohydromonas,Unclassified＿K＿＿norank＿d＿＿bacteria,These genera accounted for more than 85%of the total abundance in maize and soybean rhizosphere.In maize rhizosp here soil,Bradyrhizobium was significa-ntly affected by nitrogen application rate,and decr eased with nitrogen application levels increased.RDA results showed that the maize rhizos phere nitrogen fixing bacteria community structure was significantly correlated with soil p H（p=0.002）and soil AN（p=0.024）contents,while the soybean rhizosphere nitrogen fixing ba cteria community structure was not significantly correlated with soil physical and chemical factors.The nitrogen supply levels significantly affected the nitrogen fixing gene（nifH）copies in maize and soybean.Maize nitrogen fixing gene（nifH）copies decreased with the nitrogen application levels increased,and it was the lowest in N3 treatment.The soybean nitrogen fixing gene（nifH）copies reached the maximum value in N1 treatment,which was 6.25×10⁷copies·g^-1.Intercropping had no significantly affect to nifH gene copies in maize and soybean rhizosphere soil.Correlation analysis showed that nifH gene copies was significantly negatively correlated with soil available nitrogen,and positively correlated with soybean nitrogen fixation amounts..更多还原