上海城郊不同农业用地类型土壤硝化和反硝化作用

采用气压过程分离(BaPS)技术对上海城郊不同农业用地类型土壤总硝化速率和反硝化速率进行了测定.结果表明:不同农业用地类型土壤总硝化速率和反硝化速率差异显著(p<0.05).其中大棚蔬菜总硝化速率和反硝化速率最高;在土壤含水量15%～30%范围内.土壤总硝化作用和反硝化作用对氮损失的贡献率分别为46.8%,53.2%.土壤含水量和土壤通气孔隙度的适度增加均有利于土壤硝化作用和反硝化作用的进行;总硝化速率与土壤含水量、土壤通气孔隙度、全氮含量呈显著性相关(p<0.05),与土壤N_3~--N呈极显著性相关(p<0.01);反硝化速率与土壤含水量、N_3~--N、全氮呈显著性相关(p<0.05),与土壤通气孔隙度呈极显著性相关(p<0.01);中等土壤含水量范围内,影响土壤硝化作用、反硝化作用的环境因子趋于多样和复杂化,各种土壤环境因子共同影响和决定土壤硝化和反硝化过程.     

土壤硝化-反硝化作用研究进展

硝化－反硝化作用是氮素循环的重要环节，涉及到气态氮的损失和污染生态环境的影响，是当今氮素研究的热点之一。本文综述了近年来土壤硝化－反硝化作用损失量，机理研究方法及控制对策等方面的研究进展和展望。     

田间土壤反硝化作用动态初探

通过不同供水水平条件下对田间土壤反硝化作用进行动态研究。利用Ｃ２Ｈ２能抑制反硝化作用的Ｎ２Ｏ→Ｎ２的转化过程，用气相色谱检测出土壤中释放出的Ｎ２Ｏ的量。结果表明，田间土壤含水量较大时的土壤反硝化作用强度比其它时期明显增加，不仅增强了田间Ｎ素的气态损失，而且给大气环境造成一定程度的潜在危害。     

湿地土壤的硝化-反硝化作用及影响因素

硝化-反硝化作用与土壤的供氮能力及氮气态损失密切相关,其对于湿地氮循环的生态意义重大。综述了湿地土壤硝化-反硝化作用的研究方法、影响因素及模型表征的研究动态。当前湿地土壤硝化-反硝化作用的研究主要集中在净硝化/反硝化能力方面,而模型研究仅停留在一般概念模型和动力学模型的表征上。影响湿地土壤硝化-反硝化作用的因素主要包括温度条件、水分条件、土壤理化性质及生物区系等。鉴于当前湿地土壤硝化-反硝化作用研究内容的不均衡性和不深入性,其在今后研究中应亟需加强的领域包括:(1)硝化-反硝化作用驱动机制;(2)概念模型与应用模型表征;(3)全球变暖、降水改变及碳、氮输入等对硝化-反硝化作用的影响;(4)人类活动对硝化-反硝化作用的影响。     

土壤熏蒸剂对土壤硝化、反硝化作用的影响

采用化学分析和变性梯度凝胶电泳(DGGE)技术,以大田威百亩、棉隆、溴甲烷、硫酰氟熏蒸100 d土壤为研究对象,探究土壤熏蒸对土壤硝化活性、反硝化活性及amoA基因型硝化型细菌、nirS基因型反硝化细菌群落结构影响。研究表明,威百亩、棉隆、硫酰氟熏蒸剂处理下,土壤硝化活性与对照无显著差异;而溴甲烷处理的硝化活性比对照降低13.19%,差异显著(P0.05);熏蒸剂之间土壤硝化活性无显著差异。4种熏蒸剂之间以及与对照之间土壤反硝化活性无显著差异。4种熏蒸剂中溴甲烷处理土样amoA型硝化细菌多样性指数、均匀度显著低于对照土样和其他3种熏蒸剂处理土样;而丰富度指数无显著差异。威百亩、棉隆和硫酰氟熏蒸土样之间及与对照之间amoA型硝化细菌3种生态指数无明显差异。4种熏蒸剂处理土壤nirS型反硝化细菌多样性指数、均匀度与对照无显著差异(P0.05);熏蒸剂之间存在显著差异(P0.05)。研究表明,溴甲烷对土壤硝化活性的抑制是通过抑制amoA型硝化细菌的多样性而实现,其他3种熏蒸剂对土壤硝化活性无显著影响。4种熏蒸剂对土壤反硝化活性无显著影响。     

运用乙炔抑制-静态土柱培养法测定旱地土壤氮素反硝化损失

介绍了测定土壤反硝化作用的乙炔抑制 -静态土柱培养法 ,并就其应用中的一些条件进行了说明 ,内容包括土柱的取样深度、土柱取样量、土柱培养方式及基本操作程序等。最后阐述了这一方法在北京郊区土壤上的使用情况。     

旱地土壤中的硝化-反硝化作用

本文综述了国内外旱地土壤硝化 -反硝化作用的过程及其影响因数和硝化 -反硝化作用产生的N2 O量及其影响因素以及旱地土壤上氮肥硝化 -反硝化损失量等方面的研究进展     

江苏句容水库农业流域农田土壤反硝化作用的研究

2008年6月、8月、12月和2009年3月,在江苏句容水库农业流域采集农田原状土壤样品,使用乙炔抑制实验室培养法测定土壤的反硝化速率,同时测定土壤的含水率、铵态氮（NH2-N）和硝态氮（NO_3-N）的含量,研究农田土壤反硝化速率变化、影响因素及其对流域氮损失的贡献。结果显示,旱地土壤反硝化速率范围在0．13-51．96kgN·hm^-2a^-1之间,水田土壤的反硝化速率范围在3．16-12．29kgN·hm^-2a^-1之间。相关分析表明,反硝化速率与土壤硝态氮（NO_3-N）浓度、铵态氮（NH2-N）浓度之间不具有显著相关关系;在12月和3月,反硝化速率与土壤含水率之间有显著相关关系,其他月份无显著相关关系。流域内农田土壤反硝化损失的总氮量为31．93tN·a^-1低于流域施氮总量的3．19％,可见,反硝化作用不是该流域氮损失的主要途径。     

土壤中反硝化田间原位测定方法的研究进展

土壤中的反硝化作用由于直接影响到氮肥氮的利用率和环境问题，仍然是氮素研究领域的热点和难点之一，而反硝化作用研究的进展在很大程度上依赖与土壤反硝化的田间测定方法的建立。文章就目前反硝化研究领域常用的^15N平衡差值法、^15示踪气体通量法、乙炔抑制气室法、乙炔抑制土柱法的原理、气体样的采集、测定和计算作了综述，以期为土壤反硝化的研究提供依据。     

不同菜地土壤硝化与反硝化活性

硝化作用和反硝化作用是氮素气态损失的主要途径,在实验室培养条件下,研究了3种菜地土壤之间硝化反硝化活性的差异,反硝化作用利用乙炔抑制培养法对其进行测定。结果表明,培养33d后红泥土、灰沙土和灰泥土的氮素硝化率均很高,分别为96．1％、88.3％和70．4％,其中红泥土与灰泥土的硝化率差异达到了极显著水平（P〈0．01）,而灰沙土与红泥土、灰泥土之间的差异不显著（P〉0．05）。pH值最高和最低的菜地土壤其硝化率分别表现出最高和最低,值得注意的是,在pI-14．61条件下灰泥土的硝化率可达70．4％。氮肥的施用显著或极显著增加了3种土壤硝化过程的N2O排放量,占施氮量的0．59％-0．70％。3种菜地土壤之间氮肥的反硝化活性表现为灰泥土〉红泥土〉灰沙土,其差异也极显著（P〈0．01）,氮肥的反硝化损失量占施氮量的-0．02％-0．20％。土壤硝化和反硝化氮素损失累积量随时间t的变化均符合修正的Elovich方程：y=bln（t）＋a。     

Effects of soil type and nitrate concentration on denitrification products (N2O and N2) under flooded conditions in laboratory microcosms

Abstract

Denitrification products nitrous oxide ((N₂O) and nitrogen (N₂)) were measured in three flooded soils (paddy soil from Vietnam, PV; mangrove soil from Vietnam, MV; paddy soil from Japan, PJ) with different nitrate (NO₃^–) concentrations. Closed incubation experiments were conducted in 100-mL bottles for 7 d at 25°C. Each bottle contained 2 g of air-dried soil and 25 mL solution with NO₃^– (concentration 0, 5 or 10 mg N L^?1) with or without acetylene (C₂H₂). The N₂O + N₂ emissions were estimated by the C₂H₂ inhibition method. Results showed that N₂O + N₂ emissions for 7 d were positively correlated with those of NO₃^– removal from solution with C₂H₂ (R² = 0.9872), indicating that most removed NO₃^– was transformed to N₂O and N₂ by denitrification. In PJ soil, N₂O and N₂ emissions were increased significantly (P < 0.05) by the addition of greater NO₃^– concentrations. However, N₂O and N₂ emissions from PV and MV soils were increased by the addition of 0 to 5 mg N L^?1, but not by 5 to 10 mg N L^?1. At 10 mg N L^?1, N₂ emissions for 7 d were greater in PJ soil (pH 7.0) than in PV (pH 5.8) or MV (pH 4.3) soils, while N₂O emissions were higher in PV and MV soils than in PJ soil. In MV soil, N₂O was the main product throughout the experiment. In conclusion, NO₃^– concentration and soil pH affected N₂O and N₂ emissions from three flooded soils.     

Nitrous oxide fluxes and denitrification sensitivity to temperature in Irish pasture soils

Nitrous oxide (N₂O) emissions from grazed pastures constitute approximately 28% of total global anthropogenic N₂O emissions. The aims of this study were to investigate the effect of inorganic N fertilizer application on fluxes of N₂O, quantify the emission factors (EFs) for a sandy loam soil which is typical of large areas in Ireland and to investigate denitrification sensitivity to temperature. Nitrous oxide flux measurements from a cut and grazed pasture field for 1 year and denitrification laboratory incubation were carried out. The soil pH was 7.3 and had a mean organic C and N content at 0–20 cm of 44.1 and 4.4 g/kg dry weight, respectively. The highest observed peaks of N₂O fluxes of 67 and 38.7 g N₂O‐N per hectare per day were associated with times of application of inorganic N fertilizer. Annual fluxes of N₂O from control and fertilized treatments were 1 and 2.4 kg N₂O‐N per hectare, respectively. Approximately 63% of the annual flux was associated with N fertilizer application. Multiple regression analysis revealed that soil nitrate and the interaction between soil nitrate and soil water content were the main factors controlling N₂O flux from the soil. The derived EF of 0.83% was approximately 66% of the IPCC default EF value of 1.25% as used by the Irish EPA to estimate greenhouse gases (GHGs) in Ireland. The IPCC‐revised EF value is 0.9%. A highly significant exponential regression (r² = 0.98) was found between denitrification and incubation temperature. The calculated Q₁₀ ranged from 4.4 to 6.2 for a temperature range of 10–25 °C and the activation energy was 47 kJ/mol. Our results show that denitrification is very sensitive to increasing temperature, suggesting that future global warming could lead to a significant increase in soil denitrification and consequently N₂O fluxes from soils.     

Denitrification characteristics of pond sediments in a Chinese agricultural watershed

Ponds are widely distributed in rice-based agricultural watersheds, particularly in southern China, and may play an important role in nitrate (     ) removal. However, the denitrification rate of pond sediment, measured using the acetylene (C₂H₂) inhibition technique, indicated that the amount of nitrogen removed by denitrification accounted for <1% of the total nitrogen applied. The present study was undertaken to determine the effects of sediment depth and temperature on denitrification of pond sediment using the C₂H₂ inhibition technique. The highest denitrification potential was found in the upper 5 cm of sediment, but this only accounted for approximately 34% of the total denitrification of the upper 0–30 cm of sediment, suggesting that sediment denitrification potential would be underestimated if only the upper 5 cm of sediment was measured. The denitrification potential was low and showed a weak response over a temperature range of 6–18°C, whereas denitrification increased significantly from 18 to 30°C, indicating that denitrification may play an important role in the removal of     in warm seasons. A comparison of the     disappearance and C₂H₂ inhibition methods showed that they were significantly ( P  < 0.01) and positively correlated. However, the C₂H₂ inhibition method gave only approximately 25% of the values determined by the     disappearance method.     

固化土集流面无侧限抗压强度影响因素研究

该文采用无侧限抗压强度作为反映指标,对影响固化土强度的剂量、龄期、密度、含水率、凝结时间和养护环境等主要因素进行研究,提出增强土壤固化剂集流面强度的措施。研究结果表明：固化剂集流面的剂量选择12％左右,养护龄期需要7 d以上,压实度控制在0.94以上。在同一密度下含水率为最优含水率的(80±5)%范围内时,固化土的强度达到最大。在混合料拌和好12 h内尽快完成施工。施工结束后,应立刻进行覆盖防蒸发处理,24 h后方可进行洒水或浸水养护。温度和湿度越高越有利于固化剂集流面强度的增长和外观的平整。     

闽南农业流域土壤氮矿化作用初步研究

用原位培养法对五川流域内的香蕉地、菜地、香蕉地与菜地间作地、林地、甘蔗地土壤的氮矿化作用进行了研究,结果发现不同土地利用方式下土壤氮矿化速率平均为N0.11mgkg-1d-1,其中香蕉地土壤氮矿化最高可达N1.47mgkg-1d-1;土壤硝化速率平均为N0.27mgkg-1d-1,其中菜地下土壤硝化作用强度最高可达N0.69mgkg-1d-1。土壤矿化作用同土壤湿度、温度、C/N、土壤肥力存在明显的相关关系。不同土地利用方式下温度是土壤氮矿化最主要的影响因子。闽南流域土壤年矿化量平均为N240kghm-2,部分样地最高可达N850kghm-2,而年施肥量平均N650kghm-2。相比较而言,说明了土壤矿化是我国南方流域农业土壤氮素的重要来源。     

安徽省大别山区上舍小流域植被根系与土壤抗冲性研究

 采用标准地调查方法,对大别山区上舍小流域不同植被类型根系,在040 cm土壤深度范围内按照10cm间隔分层采样,室内测定不同径级（<0.5,0.5～1.0,1.0～2.0和2.0～5.0mm）根系生物量和根系长度,同时在各标准地根系相似地段内,采用C.C.索波列抗冲仪,在0～40 cm深度范围内按照10cm间隔分层测定土壤的抗冲性。结果表明:植被根系主要分布在0～40 cm土层内,表土层根量最大,根径<1.0mm的细根在根长上占有绝对优势;同一植被类型表土层土壤抗冲能力大于心土层;植物根系,尤其是根径<1.0mm的细根具有较强的固持土壤功能,细根长、根质量、根密度与土壤抗冲指数之间的相关系数分别为0.817 3、0.715 9和0.6434,可知,细根长是影响土壤抗冲性的关键因子;不同植被类型土壤的抗冲性与土壤非毛管孔隙度具有很高的相关性,表明森林植被的固土功能是通过根系改善土壤的物理性质,创造具有抗冲能力的生物土壤复合体结构实现的。     

设施菜田土壤剖面中的反硝化特征

利用田间原位硅胶管法和自动连续在线培养监测体系（Robot 系统）,分别监测了设施菜田不同施肥处理土壤剖面N2O浓度以及不同土层土壤反硝化潜势、NO和N2O产生潜势。结果表明:灌溉施肥后,传统施肥处理（CN）土壤剖面50 cm和90 cm处的N2O浓度都会出现峰值,50 cm处的N2O浓度峰值都高于90 cm处; 50 cm处的N2O变幅在2.15～50.77 l/L 之间,90cm处的变幅在2.57～14.05 l/L 之间;空白处理（CK）剖面N2O浓度几乎不受灌水的影响,50 cm和90 cm处的N2O浓度变幅较小,在1.43～2.75 l/L 之间。反硝化潜势、NO和N2O产生潜势的监测结果显示,040 cm土层反硝化较为强烈;40100 cm土层中由于受碳源限制,反硝化发生及强度明显滞后,添加碳源,经过48 h培养后,能够达到与表层反硝化潜势相当的程度;厌氧条件下,上层040 cm土壤的N2O和NO产生量远高于底层40100 cm的。由此推测,原位监测的高N2O浓度,可能来源自上层的扩散,因而田间表层通量观测数据可能会低估N2O产生量。底层土壤有一定反硝化潜势,当施用有机肥后,底层土壤氮素反硝化损失不容忽视。     

Effect of rice plant growth on denitrification in rhizosphere soil

The effect of rice plant growth on the loss of basal nitrogen (N) through denitrification in the rhizosphere of subsurface soil was investigated by the ¹⁵N balance method. Labeled ¹⁵N was applied to the deep soil layer to distinguish between the N losses in the surface and subsurface soils. Denitrification in pots with whole plants (Control) was compared with that in pots with plants cut off at the base of the culm (Pcut) to evaluate the effect of plant growth on denitrification. The upward movement of the applied ¹⁵N from the deep soil was negligible. Thus, the amount of unrecovered ¹⁵N was equal to the amount of N lost through denitrification in the rhizosphere of the subsurface soil (20–150 mm soil depth). In the Control treatment, values of redox potential at 50 and 90 mm soil depths were negative throughout the experimental period. Therefore, it was assumed that the redox potential could not have been the limiting factor for the N loss through denitrification in this experiment. The α-naphthylamine-oxidizing activity of roots decreased drastically after the cutting treatment. The estimated amount of de nitrified ¹⁵N in the rhizosphere of the subsurface soil was significantly higher in the Pcut treatment than in the Control one at 30 and 40 d after transplanting (DAT), while it was comparable in the two treatments at 52 and 64 DAT. Since a greater amount of ¹⁵N loss was found to occur when there was no absorption of ¹⁵N by the plants, the absorption of ¹⁵N by plants may have contributed to the suppression of denitrification. The amount of immobilized ¹⁵N in the Control treatment was larger than that of the Pcut treatment throughout the experiment. N immobilization might have also contributed to the suppression of denitrification in the rhizosphere of the subsurface soil.     

小流域农业面源污染阻力评价及"源-汇"风险空间格局

识别评价影响农业面源污染的"源-汇"风险格局,对小流域的农业面源污染防治规划有着重要的现实意义,为此,该文以三峡库区典型农业区王家沟小流域为研究区,借助最小累计阻力模型评价小流域农业面源污染阻力和识别"源-汇"风险。首先,通过土地利用解译数据确定"源"地的分级,在获取地形、距离、土地利用和氮磷等自然影响因子的基础上,构建氮和磷的阻力基面评价指标体系,并测算氮、磷和总阻力面,以此判定影响小流域农业面源污染的阻力空间分布趋势;同时借助阻力阈值,对阻力面进行等级划分,以此识别影响库区小流域农业面源污染的"源-汇"风险格局。结果表明:1)影响农业面源污染的不同阻力因子,其空间分布存在明显差异,由此奠定了阻力基面的空间异质性;阻力基面反映了影响三峡库区小流域农业面源污染的"源-汇"景观空间差异,表现为"源"景观类型的阻力基面小于"汇"景观类型;氮和磷的阻力面总体上围绕"源"地向外呈现不断增大的空间变化特征;2)划定了影响王家沟小流域农业面源污染的"源-汇"风险区:极高风险区(0.297 7 km~2)高风险区(0.154 4 km~2)中风险区(0.147 5 km~2)低风险区(0.147 4 km~2)极低风险区(0.016 0 km~2);影响整个小流域农业面源污染的"源-汇"风险偏高,但小流域内仍有一定范围的低风险区,能确保流域内的氮磷流失得到有效拦截。研究结果有助于从影响农业面源污染的"源-汇"景观和空间阻力角度识别评价"源-汇"风险格局,为科学防范和治理农业面源污染提供决策依据。