三种硝化抑制剂抑制土壤硝化作用比较及用量研究

【目的】硝化抑制剂是调控土壤氮素转化与硝化作用微生物群落结构的有效途径。本文通过室内模拟试验对3种硝化抑制剂在不同剂量下的硝化抑制效果进行研究,旨在筛选出效果最佳的剂型与剂量,为石灰性土壤硝化抑制剂的合理应用提供依据。 【方法】培养试验在生长箱内进行,25℃黑暗条件培养;盆栽试验在温室内进行。供试硝化抑制剂为双氰胺（DCD）、3,4-二甲基吡唑磷酸盐（DMPP）和2-氯-6-三氯甲基吡啶（Nitrapyrin）,DCD和DMPP用量均设定为纯氮（N）量的0（CK）、1.0%、2.0%、3.0%、3.5%、4.0%、4.5%、5.0%、6.0%和7.0%;Nitrapyrin用量分别为纯氮量的0、0.1%、0.125%、0.2%、0.25%、0.3%、0.35%、0.4%、0.45%和0.5%,三种硝化抑制剂均设10个水平,每个水平3次重复。盆栽试验氮加入量为每公斤风干土0.50 g,三种硝化抑制剂用量分别为纯氮用量的5%、1%、0.648%。调查比较了三者的硝化抑制效果及对土壤氮素转化的影响及其对小青菜鲜重的生物学效应;采用变性梯度凝胶电泳（DGGE）法分析了不同硝化抑制剂对土壤AOA、AOB群落结构的影响。 【结果】DCD、DMPP、Nitrapyrin均可显著抑制土壤硝化作用（P＜0.05）,各硝化抑制剂处理土壤的NH₄+-N含量分别较对照提高了46.2~256.1 mg/kg、291.8~376.7 mg/kg、3.68~372.9 mg/kg。DCD与DMPP处理的硝化抑制率分别为49.3%~79.4%和96.4%~99.4%,DCD表现出明显的剂量效应,但DMPP在1%~7%浓度范围内的剂量效应不明显。Nitrapyrin在0.1%~0.2%浓度范围内有明显的剂量效应。0.25%~0.5% Nitrapyrin的硝化抑制率为98.9%~99.9%,其硝化抑制效果与DMPP处理相同。DCD、DMPP、Nitrapyrin处理的小青菜地上部分鲜重分别比氮肥处理（ASN）提高了12.7%、11.1%、17.6%。施用硝化抑制剂可改变土壤AOA和AOB群落结构,且对AOA群落结构的影响大于AOB,不同硝化抑制剂之间对AOA和AOB群落结构的影响无差异。 【结论】3种硝化抑制剂的硝化抑制效果表现为Nitrapyrin≥DMPP>DCD,均对AOA与AOB群落结构产生明显影响。各硝化抑制剂处理均可提高小青菜地上部鲜重、叶片Vc含量及可显著提高小青菜叶片氨基酸含量（P＜0.05）。综合比较,Nitrapyrin硝化抑制效果好于DMPP,DCD效果最差,推荐用量为基于纯氮0.25%的Nitrapyrin添加量。     

DCD 在不同质地土壤上的硝化抑制效果和剂量效应研究

通过硝化抑制剂抑制土壤硝化作用是实现作物铵硝混合营养和提高氮肥利用率的重要途径之一。本试验采用室内模拟的方法, 在人工气候室(25 ℃)黑暗培养条件下, 应用新疆石灰性土壤研究了不同剂量的双氰胺(dicyandiamide, DCD)在砂土、壤土、黏土3 种不同质地土壤中对土壤硝态氮、铵态氮转化的影响及DCD 的剂量效应和硝化抑制效果。处理30 d 内, 各剂量DCD 处理对砂土的硝化抑制率为96.5%~99.4%(平均值为98.3%), 在黏土上为66.9%~85.6%(平均值为77.6%), 在壤土上为49.3%~79.4%(平均值为67.7%), 总体硝化抑制率表现为砂土>黏土>壤土。在砂土上DCD 的剂量效应不明显, DCD 用量从纯氮的1.0%增加到7.0%时, 土壤中硝态氮含量仅增加1.9~10.7 mg·kg^-1(培养30 d 时); 而在壤土和黏土中, 土壤硝态氮含量随DCD 浓度的增加而显著下降, 存在明显剂量效应。这说明施用DCD 可显著抑制新疆石灰性土壤的硝化作用过程, 在砂土、壤土、黏土中DCD 的最佳浓度分别为纯氮用量的6.0%、7.0%和7.0%, 并在培养30 d 内发挥显著作用。     

石灰性紫色土硝化作用及硝化微生物对不同氮源的响应

土壤中发生的硝化作用是对p H高度敏感的典型过程。本文采用室内恒温培养法,结合定量PCR和高通量测序,研究石灰性紫色土硝化作用以及氨氧化细菌(Ammonia-oxidizing bacteria,AOB)、氨氧化古菌(Ammonia-oxidizing archaea,AOA)、亚硝酸盐氧化细菌(Nitrite-oxidizing bacteria,NOB)的丰度与群落结构对不同氮源的响应。结果表明:不同氮源均刺激土壤硝化作用的发生,CO(NH2)2处理下的净硝化速率最大,约是CK处理的4.76倍,(NH_4)2SO4和NH_4Cl处理下的净硝化速率分别为N 3.88和3.34 mg kg-1d-1。相比于(NH_4)2SO4和CO(NH2)2处理,NH_4Cl处理降低了硝态氮的累积量,抑制了铵态氮的减少量。AOB amo A基因拷贝数在28 d培养过程中变化显著(p0.05),在(NH_4)2SO4和CO(NH2)2处理中呈先增长后降低趋势,在NH_4Cl处理中呈持续增长趋势;而AOA amo A基因拷贝数无显著变化(p0.05)。说明石灰性紫色土硝化作用的主要推动者是AOB,而不是AOA。在28 d培养过程中,亚硝酸盐氧化细菌占总微生物的比例高于氨氧化细菌和古菌,意味着石灰性紫色土中可能存在全程氨氧化微生物(Comammox)。高通量测序的结果表明:石灰性紫色土中AOB的优势种群为亚硝化螺菌Nitrosospira Cluster 3,AOA的优势种群是土壤古菌Group 1.1b,NOB的优势种群是硝化螺菌Nitrospira。     

硝化抑制剂对毛竹林土壤N_2O排放和氨氧化微生物的影响

为了探索硝化抑制剂在毛竹生产中的施用技术,通过培养试验研究3,4-二甲基吡唑磷酸盐(DMPP)和双氰胺(DCD)两种硝化抑制剂对毛竹林施用尿素后土壤N2O排放、氮素转化和相关氨氧化细菌(AOB)、氨氧化古菌(AOA)群落结构和丰度的影响。试验设(1)对照(CK)、(2)单施尿素(Urea)、(3)尿素+1%DMPP(DMPP占总N的1%,下同);(4)尿素+1.5%DMPP;(5)尿素+10%DCD;(6)尿素+15%DCD等6个处理,测定N2O的排放动态以及气体排放转折点时的土壤特征指标。结果表明:与单施尿素相比,160 d的时间内两种DMPP用量处理的土壤N2O累积排放减排幅度均为54%,而10%DCD和15%DCD处理的土壤分别减少28%和41%。DMPP和DCD处理50 d和90 d时土壤的NH4+-N含量均显著高于(p0.05)单施尿素处理,而NO3--N含量和表观硝化率则恰好相反,但两种抑制剂间无差异。DMPP处理的AOB群落结构的变化从10 d开始显现,至50 d和90 d时仍保持明显的抑制状态,而DCD处理则至90 d时抑制作用基本消失。单施尿素AOB功能基因(amo A)的丰度均显著高于硝化抑制剂处理(90 d时尿素+10%DCD处理除外);在整个培养期内,尿素和对照土壤的AOA群落结构相似,硝化抑制剂反而增加了AOA功能基因的丰度,表明硝化抑制剂对AOA丰度无明显抑制作用。即两种硝化抑制剂主要通过抑制AOB起作用;调节土壤p H至中性范围,并在1%DMPP施用条件下,硝化抑制剂的抑制效果最显著。     

改性尿素施用对氨挥发量及无机氮变化的影响

采用室内土壤培养和玉米幼苗盆栽试验的方法,研究了改性尿素施用后的氨挥发量及其对土壤无机氮和pH值的影响。结果表明:(1)表施改性尿素比表施普通尿素的氨挥发量显著减少,从而降低氮素的损失;在一定范围内,土壤含水量越大,氨挥发量越低。(2)硝化抑制剂双氰胺(DCD)能够抑制土壤硝化作用,使NH+4-N能较长时间存在土壤中,从而减少NO-3-N的损失;在一定范围内,DCD施用浓度越大,抑制效果越好。(3)土壤pH值与铵态氮呈极显著指数正相关,与硝态氮呈极显著线性负相关,与无机氮呈多项式相关。因此,改性尿素能够显著减少氨挥发量,抑制土壤硝化作用,从而降低尿素的氮素损失。     

施用石灰与钙蒙脱石对酸性土壤硝化动力学过程的影响

土壤酸化是粘土矿物缓慢风化的自然过程,但近年来随着人类高强度的农业利用,土壤酸化现象逐渐加剧,而铵态氮肥的硝化作用是土壤酸化的主要贡献者之一。传统的施用石灰改良酸性土壤,常常会有反酸现象,并可能导致土壤板结。蒙脱石是碱性或中性土壤的主要粘土矿物组分,而在土壤酸化的过程中,蒙脱石被进一步风化掉。本文通过室内模拟实验,采用硝化动力学拟合及对净硝化速率的计算,分别研究了蒙脱石(Ca-M)和石灰(Ca-OH)对酸性黄壤硝化作用的影响。结果表明:酸性黄壤添加石灰或蒙脱石后,土壤均发生了显著的硝化作用,且硝化过程符合一级动力学模型N_(NO3)=N_0+N_p(1-exp(-k_1t))(P0.001)。Ca-OH处理土壤样品的净硝化速率(3.429 mg·kg~(-1)·d~(-1))显著大于Ca-M处理(2.381 mg·kg~(-1)·d~(-1));Ca-OH处理土壤样品的潜在硝化速率(V_p)和平均硝化速率(V_a)在pH值5.7和6.2时分别为6.42、8.58 mg N·kg~(-1)·d~(-1)和2.71、3.87 mg N·kg~(-1)·d~(-1),均显著大于钙基蒙脱石处理(pH值5.7和6.2时分别为3.40、4.56 mg N·kg~(-1)·d~(-1)和2.36、3.04 mg N·kg~(-1)·day~(-1))。结果表明采用石灰改良酸性土壤发生复酸化现象的可能性及程度大于钙基蒙脱石,本研究为酸性土壤改良提供了新的参考。     

种植水稻和长期施用无机肥对红壤氨氧化细菌多样性和硝化作用的影响

以中国科学院红壤生态试验站发育于第四纪红黏土的植稻红壤为研究对象,研究了长期种植水稻和施用无机肥对土壤β-变形杆菌纲中氨氧化细菌多样性和硝化作用的影响。原始红壤改种水稻13年后,氨氧化细菌16SrDNA的DGGE条带数量增加,条带谱与原始红壤的差异较大,相似性为61%,说明种植水稻后土壤氨氧化细菌群落结构发生了变化。PCR-DGGE方法研究结果也显示,长期施用无机氮肥的处理(NP、NPK和NK),DGGE带谱相似性较高,达到73%,硝化率和硝化势均高于未施用氮肥的处理。逐步回归分析显示硝化率和硝化势均随着土壤脲酶活性的提高而显著增加。推测尿素可提高土壤水解氮含量,使土壤脲酶活性提高,促进硝化细菌的生长,进而提高硝化率和硝化势。     

1-羟甲基-3,5-二甲基吡唑(DMHMP)的硝化抑制效应初探

采用室内好气培养方法,以DCD为参比对象研究了新型硝化抑制剂1-羟甲基-3,5-二甲基吡唑(DMHMP)对土壤硝化作用的影响。研究结果表明,DMHMP同DCD一样对土壤硝化作用有明显的抑制效应,主要表现在三个方面:(1)可使土壤NH4+-N含量在整个培养期内显著高于不添加抑制剂的对照处理(P<0.01);(2)使土壤NO3--N含量显著低于对照处理(P<0.01);(3)添加硝化抑制剂处理土壤的pH下降幅度和速度均较对照处理有所降低.当添加DMHMP的量与DCD相等时,其硝化抑制作用不如DCD,而当其添加量为DCD的2倍时,其硝化抑制效果明显优于DCD.在培养的第7天至第21天之间,DMHMP具有最优的硝化抑制效应。     

长期施用含氯化肥对棕壤硝化作用及氨氧化微生物的影响

【目的】氨氧化微生物是氨氧化过程的主要驱动者,氨氧化过程作为硝化作用的限速步骤对氮循环具有重要作用。本研究以沈阳农业大学棕壤含氯化肥长期定位试验的土壤为研究对象,探讨了连续34年施用高氯和低氯化肥对棕壤硝化作用及氨氧化微生物的影响。【方法】该长期试验在等量氮、磷、钾条件下,设置高氯和低氯处理,共8个处理:T1(不施肥);T2(单施尿素);T3(尿素+氯化钾);T4(尿素+过磷酸钙);T5(尿素+过磷酸钙+氯化钾);T6(尿素+磷酸一铵+氯化钾);T7(尿素+氯磷铵+氯化钾);T8(硝酸磷肥+过磷酸钙+氯化钾),T7为高氯处理。采集0—20cm土壤样品,利用荧光定量PCR技术测定氨氧化细菌(AOB)和古菌(AOA)丰度,并结合土壤硝化潜势和基本化学性质,分析长期施用含氯化肥对棕壤硝化作用及氨氧化微生物丰度的影响及影响氨氧化微生物丰度的主要环境因素。【结果】长期施肥降低了土壤pH值,高氯处理降低得最多,显著低于其他处理;高氯处理的土壤硝化潜势也显著低于其他处理,且除高氯处理外,配施磷肥的处理土壤硝化潜势显著高于不施磷处理。各处理土壤中AOA丰度均显著高于AOB,高氯处理土壤中AOA、AOB丰度均显著低于其他处理,土壤硝化潜势与AOA和AOB均呈显著正相关关系。【结论】连续施用高氯化肥34年显著降低了棕壤AOA和AOB丰度,抑制了硝化潜势。该结果可为通过含氯化肥的合理施用来调节土壤AOA和AOB,进而调控土壤氮素循环提供参考。     

碳源和氧对设施菜田土壤N_2O排放的影响

利用在线自动监测培养系统(Robot系统),研究不同氧分压、碳源投入以及不同氧分压和碳源投入组合下,添加硝化抑制剂双氰胺(DCD)对设施菜田土壤N_2O排放的影响。结果表明:随着土壤氧分压的升高,N_2O排放量呈指数下降(P0.001),土壤氧分压大于等于3%O_2后,N_2O排放量不足于无氧和微量氧(1%氧)处理的30%。添加碳源降低了有氧条件下土壤N_2O和N_2产生量,显著增加了微量氧下异养反硝化途径对N_2O的贡献量(P0.01)。在微量氧和3%O_2下,与未添加DCD的处理相比,无碳源添加且施用DCD后,N_2O的排放分别降低了64.4%和88.8%,同时N_2排放分别降低了23.4%和18.6%。从微量氧至3%O_2,虽然无碳源添加的处理硝化细菌反硝化作用对N_2O排放的贡献从17.2%增加至42.6%,但由于排放总量的急剧下降,硝化细菌反硝化作用对设施菜田土壤N_2O排放的贡献较小。本研究所用土壤pH较高,且添加DCD的处理培养前后硝酸盐基本平衡,异养的同步硝化-反硝化过程可能很弱。总之,设施菜田土壤N_2O排放主要发生在无氧和微量氧条件下。异养反硝化菌对土壤N_2O排放的直接贡献最大,尤其是在碳源较为充足的条件下。     

冬种绿肥对水稻土硝化作用的影响

冬闲田种植绿肥是传统的水稻土培肥增产措施,但绿肥-水稻种植系统中,不同绿肥种类对硝化作用的影响规律及调控机制尚不明确.采用盆栽试验,研究了冬种紫云英、油菜、黑麦草对土壤性状及硝化作用的影响,并通过特异性细菌抑制剂(卡那霉素和大观霉素)研究了氨氧化细菌(AOB)和氨氧化古菌(AOA)对硝化作用的相对贡献.结果表明,冬种三...     

pH regulates key players of nitrification in paddy soils

Increasing lines of evidence have suggested the functional importance of ammonia-oxidizing archaea (AOA) rather than bacteria (AOB) for nitrification in upland soils with low pH. However, it remains unclear whether niche specialization of AOA and AOB occurs in rice paddy wetlands constrained by oxygen availability. Using DNA-based stable isotope probing, we conclude that AOA dominated nitrification activity in acidic paddy soils (pH 5.6) while AOB dominated in alkaline soils (pH 8.2). Nitrification activity was stimulated by urea fertilization and accompanied by a significant increase of AOA in acid soils and AOB in alkaline soils. DNA-based stable isotope probing indicated significant assimilation of ¹³CO₂ for AOA only in acidic paddy soil, while AOB was the solely responsible for ammonia oxidation in the alkaline paddy soil. Phylogenetic analysis further indicated that AOA members within the soil group 1.1b lineage dominated nitrification in acid soils. Ammonia oxidation in the alkaline soil was catalyzed by Nitrosospira cluster 3-like AOB, suggesting that the physiological diversity of AOA is more complicated than previously thought, and soil pH plays important roles in shaping the community structures of ammonia oxidizers in paddy field.     

亚硝化球菌属(Nitrososphaera)可能是酸性土壤硝化作用的重要驱动者

选择初始pH相近的两个酸性土壤(JX-3和JX-7)样品进行培养试验,探讨了氨氧化古菌(ammonia-oxidizing archaea,AOA)和氨氧化细菌(ammonia-oxidizing bacteria,AOB)在酸性土壤硝化过程中所发挥的作用。结果显示,经过50 d的培养,JX-7样品硝化速率显著高于JX-3,且明显降低土壤pH。培养后,两个土壤样品AOB丰度均增加,但样品间没有显著差异;JX-7土壤AOA丰度显著增加,而JX-3无显著变化。两个土壤样品AOA群落组成本身存在分异,但对于同一样品培养前后均无显著分异;AOB群落组成在两土壤间没有分异,但培养前后分别有分异。培养后,JX-7样品中AOA优势属Nitrososphaera和某些未知微生物的个别OTUs绝对丰度显著增加,而两样品AOB中Nitrosospira属的一些OTUs的绝对丰度均显著增加。因此,所研究的酸性土壤样品中AOA是硝化作用的主要贡献者,而且AOA主要通过提高Nitrososphaera属中个别OTUs的丰度,而不是整个群落来调控硝化作用。     

长期施肥对水稻土剖面氨氧化古菌和细菌丰度及组成的影响

长期施肥影响稻田土壤理化性质和硝化微生物群落,但长期施肥对稻田不同土层氨氧化古菌(AOA)和氨氧化细菌(AOB)群落结构的影响尚不明确.以湖南宁乡稻田不同施肥制度长期定位试验为平台,选取不施肥(CK)、施秸秆有机肥(ST)、有机-无机肥配施(OM)和施全量化肥(NPK)4个处理,采用实时荧光定量PCR和Illumina...     

Contributions of ammonia-oxidizing archaea and bacteria to nitrification in Oregon forest soils

Ammonia oxidation, the first step of nitrification, is mediated by both ammonia-oxidizing archaea (AOA) and bacteria (AOB); however, the relative contributions of AOA and AOB to soil nitrification are not well understood. In this study we used 1-octyne to discriminate between AOA- and AOB-supported nitrification determined both in soil-water slurries and in unsaturated whole soil at field moisture. Soils were collected from stands of red alder (Alnus rubra Bong.) and Douglas-fir (Pseudotsuga menziesii Mirb. Franco) at three sites (Cascade Head, the H.J. Andrews, and McDonald Forest) on acidic soils (pH 3.9–5.7) in Oregon, USA. The abundances of AOA and AOB were measured using quantitative PCR by targeting the amoA gene, which encodes subunit A of ammonia monooxygenase. Total and AOA-specific (octyne-resistant) nitrification activities in soil slurries were significantly higher at Cascade Head (the most acidic soils, pH < 5) than at either the H.J. Andrews or McDonald Forest, and greater in red alder compared with Douglas-fir soils. The fraction of octyne-resistant nitrification varied among sites (21–74%) and was highest at Cascade Head than at the other two locations. Net nitrification rates of whole soil without NH₄⁺ amendment ranged from 0.4 to 3.3 mg N kg⁻¹ soil d⁻¹. Overall, net nitrification rates of whole soil were stimulated 2- to 8-fold by addition of 140 mg NH₄⁺-N kg⁻¹ soil; this was significant for red alder at Cascade Head and the H.J. Andrews. Red alder at Cascade Head was unique in that the majority of NH₄⁺-stimulated nitrifying activity was octyne-resistant (73%). At all other sites, NH₄⁺-stimulated nitrification was octyne-sensitive (68–90%). The octyne-sensitive activity—presumably AOB—was affected more by soil pH whereas the octyne-resistant (AOA) activity was more strongly related to N availability.     

基于宏基因组学的酸性森林土壤氨氧化微生物群落特征研究

全球30%以上陆地面积是酸性土壤(pH5.5),而酸性土壤中氨氧化微生物群落特征研究是破译其硝化过程微生物学机理的基础。尤其随着完全硝化微生物(Complete ammonia oxidizer,comammox)的发现,亟需重新认知酸性土壤中氨氧化微生物类群。以酸性马尾松林为研究对象,综合利用荧光定量PCR(qPCR)、凝胶电泳半定量和宏基因组测序等技术研究土壤中氨氧化古菌(Ammonia-oxidizing archaea,AOA)、氨氧化细菌(Ammonia-oxidizing bacteria,AOB)和Comammox的相对丰度以及群落组成特征。研究发现AOA和AOB amoA基因丰度分别为2.61×106 copies·g~(-1)和1.45×106copies·g~(-1);而comammoxamoA基因qPCR结果存在显著的非特异性扩增,导致其丰度被高估,而经凝胶电泳半定量矫正后,约为(1.38～1.47)×106copies·g~(-1),该结果和土壤宏基因测序揭示的comammox相对丰度基本吻合。此外,宏基因组分析发现经典嗜酸group1.1a-associated仅占AOA总类群的12%,而group1.1b则占88%,尽管目前仍未有嗜酸group 1.1b AOA纯菌株的报道。AOB主要类群为Nitrosospira(约64%),而Nitrosomonas约占36%。Comammox主要类群为clade B(约64%),而clade A仅占36%且均隶属于clade A.1亚枝,这暗示clade B与已报道的嗜中性comammox clade A纯菌株有极大的生理代谢差异。总之,本研究提供了综合利用qPCR、半定量和宏基因组分析土壤氨氧化微生物群落的策略,并建议优化comammox的qPCR引物,同时本研究系统分析了酸性马尾松林土壤中氨氧化微生物的相对丰度和群落组成特征。     

Long-term fertilization effects on active ammonia oxidizers in an acidic upland soil in China

The effects of long-term fertilization of acidic soils on ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities and its ecological implications remain poorly understood. We chose an acidic upland soil site under long-term (27-year) fertilization to investigate ammonia oxidizer communities under four different regimes: mineral N fertilizer (N), mineral NPK fertilizer (NPK), organic manure (OM) and an unfertilized control (CK). Soil net nitrification rates were significantly higher in OM soils than in CK, N or NPK soils. Quantitative analysis of the distribution of amoA genes by DNA-based stable isotope probing revealed that AOA dominate in CK, N and NPK soils, while AOB dominate in OM soils. Denaturing gradient gel electrophoresis and clone library analyses of amoA genes revealed that Group 1.1a-associated AOA (also referred to as Nitrosotalea) were the most dominant active AOA population (>92%), while Nitrosospira Cluster 3 and Cluster 9 were predominant among active AOB communities. The functional diversity of active ammonia oxidizers in acidic soils is affected by long-term fertilization practices, and the responses of active ammonia oxidizers to mineral fertilizer and organic manure are clearly different. Our results provide strong evidence that AOA are more highly adapted to growth at low pH and low substrate availability than AOB, and they suggest that the niche differentiation and metabolic diversity of ammonia oxidizers in acidic soils are more complex than previously thought.     

两种农田土壤中的氨氧化细菌和氨氧化古菌对硝化抑制剂DCD和DMPP的响应-盆栽试验

Taking two important agricultural soils with different pH, brown soil （Hap-Udic Luvisol） and cinnamon soil （Hap-Ustic Luvisol）, from Northeast China, a pot culture experiment with spring maize （Zea mays L.） was conducted to study the dynamic changes in the abundance and diversity of soil ammonia-oxidizing bacteria （AOB） and ammonia-oxidizing archaea （AOA） populations during maize growth period in response to the additions of nitrification inhibitors dicyandiamide （DCD） and 3,4-dimethylpyrazole phosphate （DMPP） by the methods of real-time polymerase chain reaction （PCR） assay, PCR-denaturing gradient gel electrophoresis （DGGE）, and construction of clone library targeting the amoA gene. Four treatments were established, i.e., no urea （control）, urea, urea plus DCD, and urea plus DMPP. Both DCD and DMPP inhibited growth of AOB significantly, compared to applying urea alone. Soil bacterial amoA gene copies had a significant positive linear correlation with soil nitrate content, but soil archaeal amoA gene copies did not. In both soils, all AOB sequences fell within Nitrosospira or Nitrosospira-like groups, and all AOA sequences belonged to group 1.1b crenaxchaea. With the application of DCD or DMPP, community composition of AOB and AOA in the two soils had less change except that the AOB community composition in Hap-Udic Luvisol changed at the last two growth stages of maize under the application of DCD. AOB rather than AOA likely dominated soil ammonia oxidation in these two agricultural soils.