生活垃圾微生物强化堆肥对放线菌群落的影响

为了探讨微生物强化堆肥对生活垃圾好氧堆肥过程及堆肥过程中放线菌群落的影响,在堆肥过程中接种高效细菌复合菌剂和真菌复合菌剂,并以不接种的堆体为对照,对堆肥过程的温度变化和木质纤维素的降解效率进行了测定,并借助于PCR-DGGE方法对堆肥过程中放线菌群落的动态变化和种群多样性进行研究。结果表明：微生物强化堆肥能缩短堆体起爆时间,并能有效提高堆体降温期和二次发酵期的温度;和自然堆肥相比微生物强化堆肥使半纤维素、纤维素和木质素的降解率分别提高8.95%、12.72%和10.13%。DGGE图谱显示：2种堆肥方式的放线菌多样性指数表现出极显著差异,微生物强化堆肥能增加堆体中优势菌群的种类和数量,能有效提高腐熟期的放线菌群落多样性,有利于堆肥腐熟。优势条带测序结果表明：在接种堆肥过程中检测到了放线菌门的棒杆菌属、分支杆菌属、链霉菌属、热孢菌属、迪茨菌属、糖丝菌属和放线菌属。     

嗜热复合菌对堆肥品质及微生物群落演替的影响

  【目的】  研究嗜热复合菌对畜禽粪污堆肥理化特性和腐熟度的影响,探讨嗜热菌影响堆肥过程的微生物机制。  【方法】  堆料由75%羊粪和25%养鸡发酵床垫料构成,初始原料C/N为28,堆料量1.2 t,高度70～90 cm,开放条垛式堆沤。处理组为堆肥添加0.1%嗜热菌B. fordii FJAT-51578和U. thermosphaericus FJAT-51579等比混合的发酵液,对照组为添加1%市售枯草芽孢杆菌堆肥菌剂(Bacillus subtilis)。堆肥时间为2021年9月18日—10月14日,每两天检测1次温度。堆肥前15天,每两天进行一次翻抛,后期每5天进行一次翻抛,保持堆肥含水量50%～60%,直至高温期结束。在堆肥开始后第1、9和26天取堆肥样品,分析氮磷含量、硝化指数和种子发芽指数。结合扩增子测序,分析堆肥细菌群落结构变化,并揭示其主要环境影响因子。采用PICRUSt分析堆肥有效氮和有效磷代谢的微生物机制。  【结果】  嗜热复合菌添加促进堆肥硝化指数的降低和种子发芽指数的升高,促进堆肥腐熟;堆肥产物碱解氮和有效磷的含量分别比市售菌剂组高11.8%和7.7%。同时,嗜热复合菌的添加改变了细菌群落的分布,降低了堆肥细菌的多样性和丰富度,提高了糖单胞菌、链霉菌和嗜热葡萄孢菌等降解菌的丰度。RDA分析表明,pH和C/N是影响堆肥微生物群落多样性的主要因素,碱解氮与芽孢杆菌和糖单胞菌属丰度正相关,有效磷与嗜热裂孢菌、直丝菌属和马杜拉放线菌属丰度正相关。氮、磷代谢相关京都基因和基因组百科全书同源基因(KO)的PICRUSt分析显示,微生物氮磷循环相关KO的丰度随着堆肥进程均有所增加。添加嗜热菌剂提高了氨化、铵同化、硝酸盐同化、同化/异化硝酸盐还原等氮循环相关KO,及无机磷溶解、酸性磷酸酶和碱性磷酸酶等磷循环相关KO。  【结论】  在畜禽粪污堆肥中添加嗜热复合菌剂加快并延长了高温期,降低了C/N,提高了堆肥中碱解氮和有效磷含量,其中C/N、硝化指数和GI指数等指标在堆肥中期达腐熟程度标准,促进堆肥腐熟。堆肥中添加嗜热复合菌剂增加了细菌氮磷代谢相关KO的表达,提高了腐熟中期堆肥中嗜热菌的丰度和种类,碱解氮与芽孢杆菌和糖单胞菌属丰度呈正相关,有效磷与嗜热裂孢菌、直丝菌属和马杜拉放线菌属丰度正相关。因此,添加嗜热复合菌促进了堆肥有效氮磷的含量。     

赤水河流域典型植被类型的土壤微生物群落结构与多样性

土壤微生物是反映土壤环境质量的重要指标,为明确赤水河流域典型植被类型土壤微生物群落特征及优势菌属,为生态系统的恢复与管理提供理论依据,采用高通量测序技术研究了赤水河流域的5种典型植被类型(灌丛、针阔混交林、常绿阔叶林、杉木林和竹林)土壤的微生物群落结构及多样性,并探讨了其主要影响因子。结果表明:(1)不同植被类型的细菌和真菌丰富度Chao1指数差异均不显著,说明二者所观测到的物种总数没有差异。Shannon指数显示各植被类型微生物多样性存在一定差异,细菌多样性以竹林最低,显著性低于灌丛和针阔混交林(p<0.05); 真菌多样性以灌丛和杉木林显著性高于其他3种植被类型(p<0.05)。(2)5种植被类型土壤细菌优势门(相对丰度>10%)主要有变形菌门(Proteobacteria)、放线菌门(Actinobacteriota)和酸杆菌门(Acidobacteriota)。其中变形菌门(Proteobacteria)在灌丛、针阔混交林和常绿阔叶林中占绝对优势(相对丰度为29.70%～33.62%),而放线菌门(Actinobacteriota)则在杉木林和竹林中最为丰富,相对丰度占比分别为32.88%,29.88%。各植被类型土壤真菌门以子囊菌门(Ascomycota)为绝对优势菌群(相对丰度>49%)。(3)5种植被类型土壤细菌和真菌中优势菌属差异较大。在细菌属水平上,针阔混交林和竹林分别以未定名的Vicinamibacterales和芽孢杆菌属(Bacillus)为优势,而其他3种植被类型则以节杆菌属(Arthrobacter)最丰富。在真菌属水平上,灌丛和常绿阔叶林中优势关键属为子囊菌门(Ascomycota)未分类真菌属(unclassified_p_Ascomycota),杉木林以被孢霉属(Mortierella)最丰富,而针阔混交林和竹林中均以沙蜥属(Saitozyma)相对丰度最高。(4)NMDS分析表明,土壤细菌与真菌群落空间分布差异显著。(5)冗余分析表明,土壤含水量、pH值和TN(总氮)对土壤细菌群落结构具有显著性的影响,而pH值、容重、TOC(总有机碳)、TN和TP(总磷)对真菌群落结构影响显著。综合分析可知,针阔混交林土壤细菌群落较丰富,杉木林土壤真菌生长较旺盛,而灌丛土壤细菌和真菌多样性均较高,应采取有效措施提高主要林分土壤养分,从而激发微生物的生长,改善土壤环境。     

秸秆还田与施肥方式对稻麦轮作土壤细菌和真菌群落结构与多样性的影响

为探索秸秆还田与施肥方式2种农田措施对水稻-小麦(稻麦)轮作土壤微生物群落的影响,阐释其对土壤细菌和真菌群落结构和多样性的影响机制,本研究通过7年稻麦轮作长期定位监测试验,设置无肥空白(CK)、常规施肥(RT)、秸秆还田+常规施肥(RS)和秸秆还田+缓释肥(SS) 4个处理,采用Illumina Miseq高通量测序技术,分析土壤细菌和真菌群落结构和多样性,探索影响微生物群落的主控环境因子。结果表明, SS作物产量在2016年和2017年分别比RT显著提高11.6%和8.2%(水稻)、4.8%和3.6%(小麦),与RS无显著差异。相比RT,秸秆还田处理显著降低了土壤pH,提升了土壤有机碳和铵态氮含量;与RS相比,SS处理提高了铵态氮含量。秸秆还田处理提升了真菌群落多样性,但对细菌群落多样性无显著影响。SS与RS在细菌真菌群落多样性方面均无显著差异。相关性分析表明,细菌群落多样性与土壤pH呈负相关,与总氮含量呈正相关;真菌群落多样性则与土壤有机碳含量显著正相关。NMDS分析表明,施肥对于细菌群落结构影响较大(55.61%),真菌群落结构则对秸秆还田响应更明显(26.94%)。与RT相比,秸秆还田显著提升了细菌放线菌门、绿弯菌门、厚壁菌门的相对丰度,同时显著提升了真菌中子囊菌门的相对丰度,降低了担子菌门和接合菌门的相对丰度,加强了土壤碳氮循环能力并抑制了病原菌。SS与RS相比,仅提升了真菌中子囊菌门的相对丰度。综上,秸秆还田配施缓释肥有助于维持或者提高土壤养分有效性、作物产量及细菌真菌群落多样性,可以促进土壤碳氮循环。     

烟株生长过程中土壤微生物的变化特征

为有效防治烟草青枯病等土传病害,探究了烟株生长过程中土壤微生物的变化特征。分别在烟株不同生长期采集根部土壤进行可培养微生物数量测定和16S/18S rDNA基因测序,以分析烟株生长过程中微生物数量、多样性以及群落结构的变化。结果表明,可培养细菌、放线菌数量随烟株生长先增多后减少,其中旺长期数量最多;真菌数量先减少后增多,以旺长期数量最少。细菌群落多样性无明显变化,真菌群落多样性在旺长期最低。微生物群落结构在旺长期变化较大,细菌优势菌群Acidobacteria(酸杆菌门)丰度较团棵期减少30%±12%,Actinobacteria(放线菌门)丰度增加116%±19%,真菌优势菌群Ascomycota(子囊菌门)丰度增加57%±36%,norankk-Fungi丰度减少83%±17%。烟株生长发育改变了土壤微生物的数量和群落结构,旺长期微生物群落结构的改变与青枯病发生存在一定联系,特别是真菌优势菌的变化可能会影响青枯病的发生。     

不同处理方式食用菌菌渣微生物多样性鉴定及其环境因子关联分析

为明确不同状态菌渣化学特性与生物学特性,利用宏基因组16S rDNA测序技术,通过Alpha多样性分析、费舍尔精确检验和Spearman相关性热图,对废弃菌渣、堆肥后菌渣及轻简化处理菌渣3种不同处理状态的菌渣开展微生物多样性、养分特性研究及其环境因子的关联分析。结果表明:废弃菌渣(M1)、堆肥后菌渣(M2)及轻简化处理菌渣(M3)的微生物多样性丰度存在较大差异,3种物料微生物属水平上物种相对丰度达到了差异显著性水平(P<0.001),其中以M3的微生物(细菌、真菌)丰度最高,表现为M1相似文献   

不同年龄段银杏树雌株根系土壤细菌群落演替特征分析

以幼年期(10年以下)、挂果期(20年)和盛年期(40年以上)的银杏树根系土壤为研究对象,探讨银杏雌株树龄与土壤中细菌菌群结构的关系。运用Illumina Mi Seq平台测序分析幼年期、挂果期以及盛年期银杏树根系土壤细菌的16S r RNA V3～V4区变异序列,对不同年龄阶段银杏树雌株根系土壤细菌的菌群多样性和结构进行研究。银杏树雌株根系土壤共获得612219条微生物的16S r RNA有效基因序列,在97%的相似水平下共得到OTU个数为23294。热图分析表明,各个年龄段银杏树雌株的土壤细菌群落差异较大,不同年龄段优势属不同。据9个土壤样品的多样性指数分析得出,在3组年龄段银杏雌株的土壤样本中,幼年期Shannon指数、Simpson指数、Chao1指数以及ACE指数都是最大,而挂果期皆最小,表明幼年期银杏雌株土壤的细菌菌群丰富度和多样性最高,挂果期银杏土壤的细菌菌群丰富度和多样性最低。变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)在土壤细菌群落中占绝对优势。挂果期和盛果期银杏雌株土壤中浮霉菌门(Planctomycetes)及变形菌门(Proteobacteria)和相对丰度普遍低于幼年期,挂果期银杏树的土壤与盛果期银杏树的土壤中的放线菌门(Actinobacteria)与绿弯菌门(Chloroflexi)的相对丰度明显高于幼年期银杏树的土壤。WS3在盛果期银杏土壤中的相对丰度最低。银杏树雌株树龄可对土壤细菌菌群的多样性及菌群结构产生影响。伴随着育种年限的增加,银杏雌株表层土壤中细菌多样性呈现先降低后增加的变化趋势,且银杏雌株树龄对其土壤细菌的多样性和结构有显著影响。     

不同年限玉米秸秆还田对土壤微生物多样性的影响

秸秆还田是培肥地力、改良土壤的重要措施。内蒙古高原向松辽平原过渡地带春玉米区,玉米长期连作导致了耕层变薄、土壤次生盐渍化等土壤退化问题。采用田间定位试验的方法,研究连续多年(8、5、2年)秸秆旋耕还田条件下对土壤微生物的影响。结果表明,秸秆还田土壤中最丰富的细菌类型为变形菌门(Proteobac-teria),其次为放线菌门(Actinobacteria)、芽单胞菌门(Gemmatimonadetes)、拟杆菌门(Bacteroidetes);真菌类型为子囊菌门(Ascomycota)和担子菌门(Basidiomycota)。随着秸秆还田年限的增加,变形菌门和酸杆菌门(Acidobacteria)相对丰度增加、放线菌门相对丰度下降,拟杆菌门相对丰度较稳定;子囊菌门、担子菌门、接合菌门(Zygomycota)相对丰度先下降后上升,而球囊菌门(Glomeromycota)和壶菌门(Chytridiomycota)相对丰度变化规律相反;属水平上Sphingomonas、Lysobacter、Hannaella相对丰度先上升后下降,而Leptosphaeria和Mono-dictys相对丰度变化规律相反;Pseudarthrobacter、Fusarium相对丰度下降,Gaiella相对丰度较稳定;Guehomyces相对丰度增加;并且细菌和真菌相对丰度拐点均出现在秸秆还田5年后。随着秸秆还田年限的增加,土壤细菌和真菌多样性均有所降低;秸秆还田与秸秆不还田土壤的差异物种有Aquicella、Fusicolla和Spizellomyces;由此可推测,秸秆还田增加土壤氮和钾含量,减少病害;试验区连续多年的玉米秸秆还田改变了土壤微生物群落组成,玉米秸秆连续还田5年后土壤微生物多样性有下降趋势。     

连作年限对设施百合土壤微生物多样性的影响

为探究不同年限连续栽培百合的设施土壤细菌和真菌群落组成变化及其与环境因子间的关系,采用Mi Seq高通量测序技术,对连作4年(C4)、连作5年(C5)和连作7年(C7)设施百合红壤中细菌和真菌群落组成和多样性的变化进行了研究。结果显示,所有样品测序后获得细菌和真菌有效序列分别是249003和451044个,细菌和真菌OTUs总数分别是906和298个。Alpha多样性分析显示,随连作年限延长设施百合红壤中细菌香农指数和辛普森指数显著升高,真菌香农指数和辛普森指数显著下降。在物种组成分析中,属于细菌优势菌种的有变形菌门(Proteobacteria)、放线菌门(Actinomycetes)、酸杆菌门(Acidobacteria)、绿弯菌门(Chloroflexi),且C4、C5和C7处理土壤中优势菌种占细菌总数比例分别是85.17%、81.04%和81.64%;而真菌菌门中,只有子囊菌门(Ascomycota)一个优势菌种,并且C4、C5和C7处理土壤中优势菌种占真菌总数比例分别93.69%、92.20%、84.31%。不同连作年限土壤中,子囊菌门镰刀菌属(Fusarium)丰度比例达44.02%～58.83%。相关性分析显示,p H值、有机碳、总氮与变形菌门、放线菌门、酸杆菌门丰度显著相关;p H与青霉属(Penicillium)显著正相关,与镰刀菌属显著负相关。由此可以认为,连作后土壤细菌微生物群落多样性指数显著上升,真菌微生物多样性显著下降,同时土壤中细菌的优势菌种有变形菌门、放线菌门、酸杆菌门、绿弯菌门,在真菌群落组成中子囊菌门占主导,连作后子囊菌门中占主导地位的镰刀菌属数量的增长可能是引起设施百合红壤连作障碍的主要原因之一。     

西辽河平原区免耕秸秆还田方式对土壤微生物群落组成的影响

  目的  针对干旱半干旱西辽河平原区农田耕层存在的土壤质量问题,揭示不同免耕秸秆还田方式对土壤微生物类群分布特征的影响。  方法  设置浅旋秸秆不还田农户模式（CK）、免耕秸秆秋覆还田（MG）、免耕秸秆秋覆春二次粉碎还田（ME）、免耕秸秆秋覆春配施秸秆腐熟剂还田（MF）、免耕秸秆秋覆春二次粉碎配施秸秆腐熟剂还田（EF）5个处理,用田间小区试验的方法,研究免耕和不同秸秆还田方式对土壤微生物群落组成的影响。  结果  0 ~ 15 cm土层中4种免耕秸秆还田方式降低细菌操作分类单元数;15 ~ 30 cm土层中MF和EF细菌操作分类单元数较高,MF中增加节杆菌属（Arthrobacter）、芽单胞菌属（Gemmatimonas）和假平胞菌属（Sphingomonas）相对丰度,EF中增加Haliangium、溶杆菌属（Lysobacter）、Subgroup_10、Alistipes和拟杆菌属（Bacteroides）相对丰度;30 ~ 45 cm土层中4种秸秆还田方式均增加细菌操作分类单元数,增加了节杆菌属、拟杆菌属、Gaiella、硝化螺旋菌属 (Nitrospira) 相对丰度,但减少了Alistipes、Escherichia-shigella相对丰度。4种免耕秸秆还田方式降低0 ~ 15 cm土层真菌操作分类单元数,但增加15 ~ 45 cm土层真菌操作分类单元数;4种免耕秸秆还田方式降低了外瓶霉属（Exophiala）和被孢霉属（Mortierella）相对丰度,秸秆还田中新出现丝状真菌柄孢霉（Podospora）、角菌根菌属(Ceratobasidium)、Archaeorhizomyces,配施秸秆腐熟剂的2个处理新出现了粉褶蕈属（Entoloma）,并增加了裂壳菌属(Schizothecium)的相对丰度。试验区能对生长环境产生较大影响的细菌比真菌多。从细菌多样性看,免耕秸秆秋覆春配施秸秆腐熟剂还田后增加了产黄菌属（Flavobacterium）、Ruminococcus__gnavus_group、Methylophilaceae相对丰度,ME和EF对产黄菌属和Methylophilaceae相对丰度增加幅度较大;从真菌多样性看,CK中Mrakia和Myceliophthora物种相对丰度较高,MF中Peristomialis和Powellomyces 物种相对丰度较高,EF中Cercophora和Scytalidium物种相对丰度较高。  结论  免耕秸秆秋覆春二次粉碎还田及其施用腐熟剂措施可增加降解纤维素功能菌及菌根真菌多样性及相对丰度,对于西辽河平原雨养区春玉米田土壤微生物多样性、丰富度的提升具有积极作用。     

氮肥减量配施微生物菌剂对灌淤土花椰菜产量及土壤微生物的影响

采用biolog微生物鉴定系统和平板稀释法探讨了氮肥减量配施自制微生物菌剂对花椰菜产量及根际土壤微生物的影响研究。结果表明:T₄（2/3倍N肥用量+微生物菌剂）、T₅（3/4倍N肥用量+微生物菌剂）和T₆（常规N肥用量+微生物菌剂）处理土壤细菌、放线菌和微生物总数数量分别增加了57.6%~321.54%,66.81%~83.62%和135.40%~232.07%,而土壤真菌数量降低34.08%~41.80%。与对照相比各施肥处理增加了土壤细菌占微生物总数的比例,降低了真菌和放线菌的比例,T₅和T₄处理效果最显著。与对照相比T₄,T₅和T₆处理显著提高了土壤微生物群总落碳源利用能力。T₄,T₅和T₆处理显著增加了土壤微生物群落对碳水化合物、羧酸类、聚合物类和氨基酸类碳源的代谢水平,T₃（单施微生物菌剂）处理显著增加了土壤微生物群落对羧酸类和聚合物类碳源的代谢水平。T₅和T₆处理对增加花椰菜产量、生物量效果接近,花椰菜产量分别增加了12.35%和10.75%,地下干生物量增加了57%左右,T₂（单施氮肥）和T₄处理增加花椰菜产量5%左右。     

Substrate inputs and pH as factors controlling microbial biomass, activity and community structure in an arable soil

Our aim was to determine whether the smaller biomasses generally found in low pH compared to high pH arable soils under similar management are due principally to the decreased inputs of substrate or whether some factor(s) associated with pH are also important. This was tested in a soil incubation experiment using wheat straw as substrate and soils of different pHs (8.09, 6.61, 4.65 and 4.17). Microbial biomass ninhydrin-N, and microbial community structure evaluated by phospholipid fatty acids (PLFAs), were measured at 0 (control soil only), 5, 25 and 50 days and CO₂ evolution up to 100 days. Straw addition increased biomass ninhydrin-N, CO₂ evolution and total PLFA concentrations at all soil pH values. The positive effect of straw addition on biomass ninhydrin-N was less in soils of pH 4.17 and 4.65. Similarly total PLFA concentrations were smallest at the lowest pH. This indicated that there is a direct pH effect as well as effects related to different substrate availabilities on microbial biomass and community structure. In the control soils, the fatty acids 16:1ω5, 16:1ω7c, 18:1ω7c&9t and i17:0 had significant and positive linear relationships with soil pH. In contrast, the fatty acids i15:0, a15:0, i16:0 and br17:0, 16:02OH, 18:2ω6,9, 17:0, 19:0, 17:0c9,10 and 19:0c9,10 were greatest in control soils at the lowest pHs. In soils given straw, the fatty acids 16:1ω5, 16:1ω7c, 15:0 and 18:0 had significant and positive linear relationships with pH, but the concentration of the monounsaturated 18:1ω9 PLFA decreased at the highest pHs. The PLFA profiles indicative of Gram-positive bacteria were more abundant than Gram-negative ones at the lowest pH in control soils, but in soils given straw these trends were reversed. In contrast, straw addition changed the microbial community structures least at pH 6.61. The ratio: [fungal PLFA 18:2w6,9]/[total PLFAs indicative of bacteria] indicated that fungal PLFAs were more dominant in the microbial communities of the lowest pH soil. In summary, this work shows that soil pH has marked effects on microbial biomass, community structure, and response to substrate addition.     

Potential nitrogen immobilization as influenced by available carbon in Japanese arable and forest soils

Abstract

Iron oxide is the most important electron acceptor in paddy fields. We aimed to suppress the methane emission from paddy fields over the long term by single application of iron materials. A revolving furnace slag (RFS; 245 g Fe kg^-1) and a spent disposable portable body warmer (PBW; 550 g Fe kg_-1) were used as iron materials. Samples of a soil with a low iron level (18.5 g Fe kg^-1), hearafter referred to as “a low-iron soil” and of a soil with a high iron level (28.5 g Fe kg^-1), hearafter referred to as “an iron-rich soil,” were put into 3 L pots. At the beginning of the experiment, RFS was applied to the pots at the rate of 20 and 40 t ha^-1, while PBW was applied at the rate of 10 t ha^-1 only, and in the control both were not applied. Methane and nitrous oxide emissions from the potted soils with rice plants were measured by the closed chamber method in 2001 and 2002. When RFS was applied at the rates of 20 and 40 t ha^-1 to the low-iron soil, the total methane emission during the cultivation period significantly decreased by 25–50% without a loss of grain yield. Applied iron materials clearly acted as electron acceptors, based on the increase in the amount of ferrous iron in soil. However, the suppressive effect was not evident in the iron-rich soil treated with RFS or PBW. On the other hand, nitrous oxide emission increased by 30–95%. As a whole, when the total methane and nitrous oxide emissions in the low-iron soil were converted to total greenhouse gas emissions expressed as CO₂- C equivalents in line with the global warming potential, the total greenhouse gas emissions decreased by about 50% due to the application of RFS.     

Maßstabsabhängige räumliche Variabilität mikrobieller Bodenkenngrößen in einem Buchenwald

Scale-dependent spatial variability of microbiological characteristics in soil of a beech forest The spatial variability of the microbial biomass content (C_mic), the microbial respiration rate (basal respiration) and the metabolic quotient (qCO₂) was analyzed in sandy Cambisols and Luvisols in a beech forest in Northern Germany. Highest variability of microbiological features and, thus, the distance of independent samples was around 10 m that is discussed with reference to spatial hierarchy. Structural changes between the 10 m and 50 m grid were suggested for the Ah horizon due to the break of correlations of C_mic content and the contents of C_org and plant-available Ca, Mg, K and N_t. The C_mic content correlated with the C_org content close to tree trunks and ecotones like borders of the forest and clearings. The qCO₂ did not generally increase with declining pH value. High H⁺ concentrations and C_org content in the litter layer near to the tree trunk indicated retarded microbial mineralization rates. High proportion of microorganisms that are resistant to low pH value and adjusted ro readily-degradable substrates seems to dominate in the soil close to the tree.     

施用味精废液对西瓜根际土壤微生物量碳、氮含量的影响

通过大田试验,研究了N100(尿素提供100%的氮)、M10N90(味精废液和尿素分别提供10%和90%的氮)、M30N70(味精废液和尿素分别提供30%和70%的氮)和M50N50(味精废液和尿素各提供50%的氮)等处理对西瓜根际土壤微生物量碳(MBC)和微生物量氮(MBN)含量的影响。结果表明,施用味精废液使土壤生物过程活跃,有利于土壤有机物质的转化和西瓜正常生长所需的营养供应。在西瓜不同生育期,根际土壤MBC和MBN含量动态变化规律不同。与M30N70处理相比,M10N90和M50N50处理对西瓜根际土壤微生物量碳、氮的影响较小。分析可知,味精废液与化肥以3∶7比例配施对西瓜根际土壤微生态环境的作用效果最佳,更有利于平衡西瓜氮素营养。     

Substrate quality affects microbial‐ and enzyme activities in rooted soil

The rhizosphere reflects a sphere of high substrate input by means of rhizodeposits. Active microorganisms and extracellular enzymes are known to be responsible for substrate utilization in soil, especially in rooted soil. We tested for microbial‐ and enzyme activities in arable soil, in order to investigate the effects of continuous input of easily available organics (e.g., root‐exudates) to the microbial community. In a field experiment with maize, rooted and root‐free soil were analyzed and rhizosphere processes were linked to microbial activity indicators such as specific microbial growth rates and kinetics of six hydrolytic extracellular enzymes: β‐glucosidase, β‐cellobiohydrolase, β‐xylosidase, acid phosphatase, leucine‐ and tyrosine‐aminopeptidase. Higher potential activities of leucine‐aminopeptidase (2‐fold) for rooted vs. root‐free soil suggested increased costs of enzyme production, which retarded the specific microbial growth rates. Total microbial biomass determined by the substrate‐induced respiration technique and dsDNA extraction method was 23% and 42% higher in the rooted surface‐layer (0–10 cm) compared to the root‐free soil, respectively. For the rooted soil, potential enzyme activities of β‐glucosidase were reduced by 23% and acid phosphatase by 25%, and increased by 300% for β‐cellobiohydrolase at 10–20 cm depth compared to the surface‐layer. The actively growing microbial biomass increased by the 17‐fold in rooted soil in the 10–20 cm layer compared to the upper 10 cm. Despite the specific microbial growth rates showing no changes in the presence of roots, these rates decreased by 42% at 10–20 cm depth compared to the surface‐layer. This suggests the dominance in abundances of highly active but slower growing microbes with depth, reflecting also their slower turnover. Shifts in microbial growth strategy, upregulation of enzyme production and increased microbial respiration indicate strong root effects in maize planted soil.     

温室菜园土壤氮矿化和微生物群落对水分的响应

Soil drying and wetting impose significant influences on soil nitrogen (N) dynamics and microbial communities. However, effects of drying-wetting cycles, while common in vegetable soils, especially under greenhouse conditions, have not been well studied. In this study, two greenhouse vegetable soils, which were collected from Xinji (XJ) and Hangzhou (HZ), China, were maintained at 30% and 75% water-holding capacity (WHC), or five cycles of 75% WHC followed by a 7-day dry-down to 30% WHC (DW). Soil inorganic N content increased during incubation. Net N mineralization (Nmin), microbial activity, and microbial biomass were significantly higher in the DW treatment than in the 30% and 75% WHC treatments. The higher water content (75% WHC) treatment had higher Nmin, microbial activity, and microbial biomass than the lower water content treatment (30% WHC). Multivariate analyses of community-level physiological profile (CLPP) and phospholipid fatty acid (PLFA) data indicated that soil moisture regime had a significant effect on soil microbial community substrate utilization pattern and microbial community composition. The significant positive correlation between Nmin and microbial substrate utilization or PLFAs suggested that soil N mineralization had a close relationship with microbial community.     

玉米地土壤微生物量碳、氮及微生物熵对不同物料还田的响应

在四川丘陵区紫色土上进行田间试验,以无物料还田为对照,对比分析了蚕豆秸秆、油菜秸秆、猪粪3种物料还田对夏玉米吐丝期和收获期0—20,20—40cm土层土壤有机碳、全氮、微生物量碳氮含量及微生物熵的影响,以期为农业废弃有机物料的综合利用及四川丘陵区土壤质量的提升提供理论参考。结果表明:(1)尽管有机物料还田于0—20cm土层中,0—20,20—40cm土层土壤有机碳(SOC)、全氮(TN)、微生物量碳(SMBC)、微生物量氮(SMBN)含量均受到有机物料的深刻影响。各处理0—20cm土层SOC、TN、SMBC、SMBN含量均显著高于20—40cm土层,且上下2层土壤SOC、TN、SMBC和SMBN含量在生育时期间均表现为吐丝期>收获期。(2)在2个生育时期,3种物料还田均能提高0—20,20—40cm土层SOC、TN、SMBC、SMBN含量。与对照相比,物料还田处理的SOC、TN、SMBC、SMBN含量分别提高2.6%~141.2%,1.9%~33.0%,5.1%~114.7%,41.5%~98.7%,其中收获期各处理0—20,20—40cm土层SOC、SMBC、SMBN均表现为油菜秸秆>蚕豆秸秆>猪粪>对照,TN表现为蚕豆秸秆>猪粪>油菜秸秆>对照。(3)各处理SMBC/SMBN、qMB、SMBN/TN分别为3.74~10.53,0.86%~2.19%,1.01%~3.41%,且物料还田降低SMBC/SMBN,提高土壤qMB和SMBN/TN值。相关分析表明,SMBC、SMBN与SOC、TN之间均存在极显著正相关关系。因此,农业生产中可通过物料还田提供给微生物足够的碳氮营养,提高土壤SMBC、SMBN、SOC、TN含量和qMB值,维持较高的农田生产力,提升土壤质量,但具体施用物料时还需寻求土壤肥力提升、玉米产量增加以及环境效益之间的平衡。     

土壤微生物对不同粒径、不同表面和孔隙性质生物炭的响应

Biochars are known for their heterogeneity, especially in pore and surface structure associated with pyrolysis processes and sources of feedstocks. The surface area of biochar is likely to be an important determinant of the extent of soil microbial attachment, whereas the porous structure of biochar is expected to provide protection for soil microorganisms. Potential interactions between biochars from different sources and with different particle sizes were investigated in relation to soil microbial properties in a short-term incubation study. Three particle size(sieved) fractions(0.5–1.0, 1.0–2.0 and 2.0–4.0 mm) from three woody biochars produced from jarrah wood,jarrah and wandoo wood and Australian wattle branches, respectively, were incubated in soil at 25?C for 56 d. Observation by scanning electron microscopy(SEM) and characterisation of pore and surface area showed that all three woody biochars provided potential habitats for soil microorganisms due to their high porosity and surface areas. The biochars were structurally heterogeneous,varying in porosity and surface structure both within and between the biochar sources. After the 56-d incubation, hyphal colonisation was observed on biochar surfaces and in larger biochar pores. Soil clumping occurred on biochar particles, cementing and covering exposed biochar pores. This may have altered surface area and pore availability for microbial colonisation. Transient changes in soil microbial biomass, without a consistent trend, were observed among biochars during the 56-d incubation.     

不同配方施肥对长期缺施钾肥的红壤性水稻土微生物特性的影响

为了验证平衡施肥对长期缺施钾肥的南方红壤性水稻土的修复效果,通过2年盆栽试验,以五种不同施肥处理（NPK、NPKSi、NPKOM、NPhK、NPhKOM）,研究了长期缺施钾肥的水稻土的微生物特性,结果发现,在对照（NPK）基础上增施硅肥（NPKSi）、钾肥（NPhK）能促进细菌和放线菌数量的增长,提高微生物活度,加速微生物量N、P的转化,同时也能提高微生物量C。相反,在淹水条件下配施有机肥（NPKOM）,由于降低了水稻根际环境的氧化还原电位,使根际微生物生长萎缩,微生物活度、微生物量C无显著提高;虽然土壤微生物量N、P随之增加,但有机N的矿化减弱,植株可吸收的有效态养分减少。增施钾肥的同时配施有机肥（NPhKOM）具有增施钾肥的优点,即可提高微生物活度、提高微生物量C,加速有机N、P的矿化,但同时也会减少微生物数量。因此在缺钾水稻土的修复实践中,常规施肥的基础上对水稻增施硅肥、钾肥应是有效举措,而配施有机肥则须谨慎:有机肥或须适量酌施,或须结合增施钾（硅）肥。