盐渍化对农田氮素转化过程的影响机制和增效调控途径

本文在回顾我国盐渍化农田氮肥利用现状的基础上,总结了盐渍化对农田土壤氮素转化关键过程的影响规律,剖析了其对参与氮素转化的微生物的作用机制,归纳了盐渍化农田氮素养分增效调控的主要途径。盐渍化对农田土壤氮素矿化、硝化和反硝化过程存在阈值效应,不同范围内影响差别较大。盐分以及次生障碍对相关微生物也具有不同的影响,且同样存在阈值效应。目前盐渍化农田氮素增效调控的途径主要包括土壤改良剂改良、生物质材料改良、种植耐盐植物、优化氮素形态配比和生物抑制剂改良,最后提出盐渍化农田氮素循环过程研究目前存在的不足以及未来的研究方向。本文对盐渍化农田氮素减损增效、化肥养分高效利用与农业面源污染阻控具有重要指导意义。     

2-氯-6(三氯甲基)吡啶对紫云英、苕子的影响

Goring首先报导了美国道化学公司研制的2—氯—6(三氯甲基)吡啶(简称CP)对亚硝化细菌(Nitrosomonas)具有很强的抑制能力,因而被称为硝化抑制剂(国内称为氮肥增效剂)。硝化抑制剂是减少氮肥从土壤中损失,提高作物对氮素吸收利用的一种化肥辅助剂。以后,日本、苏联、英国、西德、印度等都相继进行研究,品种剧增至五十余种;但到目前为止,仅GP一种作为世界上第一个氮肥增效剂在美国投入工业化生产,并在农业上开始广泛使用。我国于1969年开始氮肥增效剂的研究,1975年“全国氮     

硝化抑制剂的施用效果、影响因素及其评价

硝化抑制剂施用后其显著的农学效应、环境效应和生态效应已得到许多研究的证实,但其施用效果受多种因素的影响.本文从硝化抑制剂施用对土壤氮素转化、硝酸盐淋溶损失和温室气体排放、作物氮素利用、农产品产量和品质以及其他养分有效性的影响等几个方面进行综述,并分析影响其施用效果的因素和评价标准.     

高效稳定性硫酸铵氮肥在黑土中的施用效果

为筛选高效稳定性氮肥,采用盆栽试验,通过监测施用不同处理的稳定性硫酸铵对黑土铵态氮和硝态氮含量、表观硝化率、硝化抑制率、玉米生长指标、产量和氮素效率等指标的影响,研究添加不同生化抑制剂配方的稳定性硫酸铵态氮肥在吉林黑土玉米栽培中的施用效果。本试验以不施氮肥(CK)和施硫酸铵(N)为对照,在硫酸铵中分别添加硝化抑制剂3,4-二甲基吡唑磷酸盐(DMPP)、2-氯-6-三甲基吡啶(CP),氮保护剂(N-GD)和肥料增效剂(HFJ)及其组合,制成9种稳定性硫酸铵氮肥。结果表明: 与单施硫酸铵氮肥处理相比,在黑土中添加DMPP和DMPP组合显著影响土壤中铵态氮和硝态氮含量及土壤表观硝化率,铵态氮含量提高1.4～2.0倍,硝态氮含量降低13.6%～17.9%,土壤表观硝化率降低55.3%～59.8%;添加DMPP、DMPP+HFJ和DMPP+N-GD组合硝化抑制率最高,达到16.5%以上;添加DMPP+HFJ+N-GD和HFJ的硫酸铵处理玉米叶片叶绿素含量增加最显著,增加4.5～5.3倍;硫酸铵添加硝化抑制剂和肥料增效剂对株高无显著影响;添加HFJ的硫酸铵处理玉米生物量、籽粒产量、经济系数、收获指数、氮肥农学利用率、氮素吸收利用率、肥料贡献率和氮肥偏生产力增加最显著,分别增加1.2、2.5、0.7、0.6、2.7、2.1、1.3和2.5倍。添加HFJ和DMPP、DMPP+HFJ、DMPP+N-GD处理的硫酸铵处理在黑土中施用效果最好,但是DMPP成本较高,因此,兼顾成本和氮肥利用率,建议稳定性硫酸铵态氮肥生化抑制剂首选氮肥增效剂HFJ,其次选择DMPP+HFJ或者DMPP+N-GD。     

土壤氮素转化的关键微生物过程及机制

微生物是驱动土壤元素生物地球化学循环的引擎.氮循环是土壤生态系统元素循环的核心之一,其四个主要过程,即生物固氮作用、氨化作用、硝化作用、反硝化作用,均由微生物所驱动.近10年来,随着免培养的分子生态学技术和高通量测序技术等的发展,在硝化微生物多样性及其作用机理、厌氧氨氧化过程和机理等研究方面取得了突破性进展.本文重点阐述了我国有关土壤硝化微生物方面的研究进展,在此基础上,简要介绍了反硝化微生物和厌氧氨氧化及硝酸盐异化还原成铵作用的研究进展,并对今后的研究工作提出了展望.今后土壤氮素转化微生物生态学的研究,应瞄准国际微生生态学发展的前沿,加强新技术新方法的应用,结合我国农业可持续发展、资源环境保护和全球变化研究的重大需求,重点开展以下几方面的工作:(1)开展大尺度上土壤硝化作用及氨氧化微生物分布的时空演变特征及驱动因子的研究;(2)加强氮素转化关键微生物过程与机理的研究,并与相关过程的通量(如氨挥发、N2O释放)和反应速率(如矿化速率、硝化速率)关联起来;(3)在特定生态系统中系统研究各个氮转化过程的耦合关系,构建相关氮素转化和氮素平衡模型,为定向调控土壤氮素转化过程,提高氮素利用效率并减少其负面效应提供科学依据.     

氮素调控剂对不同类型土壤氮素转化的影响

采用室内培养试验方法,比较了硝化抑制剂双氰胺（DCD）和3,5-二甲基吡唑（DMP）对华北平原两种主要土壤类型潮褐土和潮土中氮素转化的调控效果,并进一步研究了DMP与脲酶抑制剂氢醌（HQ）的配合施用对潮土中氮素转化的影响.结果表明： 在两种供试类型土壤上DMP对尿素氮的硝化抑制作用均强于DCD.与单施尿素相比,在氮素转化高峰时,DMP可使土壤中NH₄⁺-N含量显著提高149.5%～387.2%,NO₃^--N含量降低22.3%～55.3%;同一抑制剂对潮土中氮素转化的调控效应较潮褐土更为明显;与DMP单施相比,DMP和HQ配施表现出明显的对氮素转化的协同抑制效果.
     

森林土壤氮素的转化与循环

森林土壤氮素转化与循环在森林生态系统功能中占有极其重要的意义。本文综述了森林土壤氮素转化与循环的研究历程和现状 ;介绍了凋落物的归还、施肥、大气沉降、自生固氮、氨化、硝化、反硝化、植物吸收、NH3 的挥发、NO3 -淋溶等土壤氮素输入、转化和输出的途径和过程 ;最后从研究目标、研究方法、研究对象和研究内容 4个方面归纳了森林土壤氮素转化与循环的发展趋势。     

放牧对草地土壤氮素循环关键过程的影响与机制研究进展

放牧是人类管理利用草地生态系统的最主要途径之一.食草动物的采食、践踏、卧息和排泄物归还等干扰不仅会改变草地地上植物群落,也会对土壤养分循环产生显著的影响.随着人类活动的加剧,放牧强度和频率也在逐渐增加,从而对草地土壤氮素循环关键过程产生重要影响.放牧主要通过改变土壤的物理性质、土壤氮库以及微生物的组成和结构,进而影响氮素在土壤中的迁移与转化.适度放牧会促进土壤氮素的矿化过程和硝化过程,加快氮素的周转,有利于植物吸收可利用氮素,而对于反硝化的影响与草地的水热条件和土壤类型等密切相关.目前,关于放牧强度对土壤氮素循环关键过程影响的研究结果不一致,其影响机制尚不明晰,尤其对于不同类型的草原仍存在较大的差异.本研究在大量查阅国内外已有研究结果的基础上,论述了放牧对土壤氮素循环关键过程的影响效应,总结了放牧对土壤氮素循环的影响机制,指出了目前研究过程中存在的不足,并对未来研究中值得重点关注和深入研究的科学问题进行了探讨与展望,为进一步理解放牧对草地土壤氮素循环的影响提供参考.     

异养硝化-好氧反硝化菌脱氮相关酶系及其编码基因的研究进展

水体氮素污染日益严重,如何经济、高效地去除水体氮素已成为研究热点。近年来,研究人员已从不同环境中分离到许多同时具有异养硝化和好氧反硝化功能的菌株,此类菌生长迅速,可在好氧条件下同时实现硝化和反硝化的过程,并可用于脱除有机污染物,是一类应用潜力巨大的脱氮菌。目前,异养硝化-好氧反硝化菌的脱氮途径和机制主要是通过测定氮循环中间产物或终产物、测定相关酶活性、注释部分氮循环相关基因及参考自养硝化菌和缺氧反硝化菌的氮循环途径等进行研究,其完整的氮素转化途径和氮代谢机制还需要进一步明确。总结了目前异养硝化-好养反硝化菌的脱氮相关酶系及其编码基因的研究进展,以期为异养硝化-好氧反硝化菌的理论研究及其在污水脱氮处理上的应用提供参考。     

稻田生态系统氮素转化经济价值研究

根据2002年上海奉贤县五四农场田间实验数据,结合相关研究结果对稻田氮素输入和输出进行研究,并运用生态经济学和环境经济学方法计算稻田生态系统氮素转化的经济价值.结果表明,当季不施氮肥的处理小区氮素收支出现赤字;而施加氮肥的处理小区氮素收支都出现盈余.不施氮处理小区单位面积稻田提供的氮素转化综合价值为正;而施加氮肥的小区其氮素转化的综合价值都为负.施氮处理小区氮素转化的负价值主要是由于过量氮肥导致田间氮素以氨挥发、渗漏和径流方式损失造成.     

A comparison of two nitrification inhibitors used to measure nitrification rates in estuarine sediments

Abstract: Nitrification rates were measured using intact sediment cores from South San Francisco Bay and two different nitrification inhibitors: acetylene and methyl fluoride. Sediment oxygen consumption and ammonium and nitrate fluxes were also measured in these cores. Four experiments were conducted in the spring, and one in the fall of 1993. There was no significant difference in nitrification rates measured using the two inhibitors, which suggests that methyl fluoride can be used as an effective inhibitor of nitrification. Nitrification was positively correlated with sediment oxygen consumption and numbers of macrofauna. This suggests that bioturbation by macrofauna is an important control of nitrification rates. Irrigation by the tube-dwelling polychaete, Asychis elongata , which dominates the benthic biomass at this location, appears particularly important. Ammonium fluxes out of the sediment were greatest about one week after the spring bloom, while nitrification peaked about one month later.     

Measurement of nitrification rates in lake sediments: Comparison of the nitrification inhibitors nitrapyrin and allylthiourea

A method for measuring rates of nitrification in intact marine sediment cores has been modified and adapted for use in freshwater sediments. The technique involves subsampling a sediment core into minicores. Half of these cores are treated with an inhibitor of chemolithotrophic nitrification and, after incubation, differences in ammonia and nitrate concentration between inhibited and uninhibited systems are calculated. The within-treatment variability of ammonia and nitrate concentrations could be reduced by storing the cores overnight prior to subsampling. Estimates of the nitrification rate using the difference in ammonia concentrations between the inhibited and uninhibited mini-cores were always greater than the rate estimate using the difference in nitrate concentrations. Comparison between the results using the nitrification inhibitors allylthiourea (ATU) and nitrapyrin (N-Serve) indicated that the former appeared to give larger values for the nitrification rate than did the latter. Differences in the efficiency of these inhibitors in the control of nitrification under the conditions used partly explain these results. Data are also presented on the effect of N-Serve and ATU on some other nitrogen transformations affecting ammonia and nitrate concentrations.     

Estimation of nitrification rates in flooded soils

Three techniques for estimating nitrification rates in flooded soils were evaluated in short-term incubation experiments using three soils. The techniques were based on inhibition of either ammonium or nitrite oxidation and ¹³N isotope dilution. Of four inhibitors of ammonium oxidation evaluated, one (allylthiourea) was ineffective and two (2-ethynylpyridine or phenyl acetylene dissolved in ethanol) promoted immobilization of ammonium. Emulsified 2-ethynylpyridine and acetylene were equally effective inhibitors of ammonium oxidation and had little or no effect on gross rates of N mineralization and immobilization. Four inhibitors of nitrite oxidation were evaluated, but this approach was compromised by the nonspecificity of three of the compounds—potassium cyanide, 2-ethylamino-4-isopropylamino-6-methylthio-s-triazine (ametryne) and 3-(3,4-dichlorophenyl)-1-methylurea (DMU)—and by the partial effectiveness of another (potassium chlorate). Two methods based on isotope dilution gave similar estimates of nitrification rates. These rates were similar to those estimated by inhibition of ammonium oxidation in one soil but were lower in the other two soils. In the latter two soils, nitrification of labeled ammonium derived from dissimilatory nitrate reduction resulted in underestimation of nitrification rates by isotope dilution.     

硝化抑制剂DCD、 DMPP对褐土氮总矿化速率和硝化速率的影响

采用15N库稀释-原位培养法研究了硝化抑制剂DCD、DMPP对华北盐碱性褐土氮总矿化速率和硝化速率的影响.试验在山西省运城市种植玉米的盐碱性土壤上进行,设单施尿素、尿素+DCD、尿素+DMPP 3个处理.结果表明:施肥后2周,DCD、DMPP分别使氮总矿化速率和氮总硝化速率减少了25.5％、7.3％和60.3％、59.1％,DCD对氮总矿化速率的影响显著高于DMPP,两者对氮总硝化速率的影响无显著差异;而在施肥后7周,不同硝化抑制剂对氮总硝化速率的影响存在差异.施肥后2周,3个处理的土壤氮总矿化速率和硝化速率分别是施肥前的7.2 ～10.0倍和5.5 ～21.5倍;NH4+和NO3-消耗速率分别是施肥前的9.1 ～12.2倍和5.1 ～8.4倍,这是由氮肥对土壤的激发效应所致.硝化抑制剂使氮肥更多地以NH4+形式保持在土壤中,减少了NO3-的积累.土壤氮总矿化速率和总硝化速率受硝化抑制剂的抑制是N2O减排的主要原因.     

Plant influence on nitrification

Modern agriculture has promoted the development of high-nitrification systems that are susceptible to major losses of nitrogen through leaching of nitrate and gaseous emissions of nitrogen oxide (NO and N2O), contributing to global warming and depletion of the ozone layer. Leakage of nitrogen from agricultural systems forces increased use of nitrogen fertilizers and causes water pollution and elevated costs of food production. Possible strategies for prevention of these processes involve various agricultural management approaches and use of synthetic inhibitors. Growing plants capable of producing nitrification suppressors could become a potentially superior method of controlling nitrification in the soil. There is a need to investigate the phenomenon of biological nitrification inhibition in arable crop species.     

Comparison of Karanjin with other nitrification inhibitors for retardation of nitrification of urea N in soil

Summary Comparative evaluation of Kranjin and three patented nitrification inhibitors for retardation of nitrification of urea in a sandy clay loam showed that the effectiveness of the compounds tested decreased in the order: Nitrapyrin>Karanjin>A.M.>dicyandiamide.     

Evaluation of chelating compounds and carbofuran for inhibiting nitrification in soils

Summary Studies to evaluate 5 chelating compounds NTA (nitrilotriacetic acid), EDTA (ethylene diaminetetra acetic acid), tartaric acid, citric acid, thiourea and an insecticide, carbofuran as inhibitors of nitrifucation in a sandy loam (pH 7.7) at 10 and 50 ppm concentrations showed that except thiourea and carbofuran they had no appreciable effect on nitrification. Even thiourea and carbofuran were moderately effective at higher concentrations in retarding nitrification in soil at the most upto 3 weeks. The results of the study suggest that all the chelating compounds may not necessarily be inhibitors of nitrification process in soils as commonly believed and that carbofuran may have little effect on nitrification in soils with pH in the alkaline range under normal application rates.     

不同硝化抑制剂对红壤氮素硝化作用及玉米产量和氮素利用率的影响

本研究分析添加不同种硝化抑制剂及其组合的高效稳定性氯化铵氮肥对红壤硝化作用、玉米产量和氮肥利用率的影响,旨在筛选出适合酸性红壤的高效稳定性氯化铵态氮肥。在氯化铵中分别添加硝化抑制剂2-氯-6-三甲基吡啶(CP)、3,4-二甲基吡唑磷酸盐(DMPP)和双氰胺(DCD)及其组合,制成6种高效稳定性氯化铵态氮肥,以不施氮肥(CK)和施氯化铵(N)为对照,进行等氮量玉米盆栽试验。结果表明: 与N处理相比,CP+DMPP和DMPP+DCD处理红壤中铵态氮含量提高56%～62%,显著高于CP、DMPP和DCD处理;土壤表观硝化率显著降低33%～34%。添加硝化抑制剂及其组合的6个处理均显著提高了玉米生物量和氮肥吸收利用率。与N处理相比,单独添加硝化抑制剂处理生物量均显著高于硝化抑制剂组合处理,平均提高1.3倍;添加DCD处理效果最显著,玉米籽粒产量、吸氮量和氮肥吸收利用率分别显著提高4.1、6.3和4.4倍。为了达到既能低成本又能提高产量和氮肥利用率的效果,在红壤上添加硝化抑制剂DCD是最佳选择。     

硝化抑制剂DCD、DMPP对褐土氮总矿化速率和硝化速率的影响

采用¹⁵N库稀释-原位培养法研究了硝化抑制剂DCD、DMPP对华北盐碱性褐土氮总矿化速率和硝化速率的影响.试验在山西省运城市种植玉米的盐碱性土壤上进行,设单施尿素、尿素+DCD、尿素+DMPP 3个处理.结果表明：施肥后2周,DCD、DMPP分别使氮总矿化速率和氮总硝化速率减少了25.5%、7.3%和60.3%、59.1%,DCD对氮总矿化速率的影响显著高于DMPP,两者对氮总硝化速率的影响无显著差异;而在施肥后7周,不同硝化抑制剂对氮总硝化速率的影响存在差异.施肥后2周,3个处理的土壤氮总矿化速率和硝化速率分别是施肥前的7.2～10.0倍和5.5～21.5倍;NH₄⁺和NO₃^-消耗速率分别是施肥前的9.1～12.2倍和5.1～8.4倍,这是由氮肥对土壤的激发效应所致.硝化抑制剂使氮肥更多地以NH₄⁺形式保持在土壤中,减少了NO₃^-的积累.土壤氮总矿化速率和总硝化速率受硝化抑制剂的抑制是N₂O减排的主要原因.     

Effect of chemicals used as nitrification inhibitors on the denitrification process.

Several chemicals used as nitrification inhibitors were tested to determine their effect on dentrification by a Pseudomonas sp. and in soil. Denitrification by the bacterium was suppressed by 2-chloro-6(-trichloromethyl)-pyridine (N-Serve) at a concentration of 50 ppm, while 2,5-dichloroaniline caused the accumulation of nitrite in the culture medium. The nitrification inhibitors had little effect on the denitrifying activity in soil under anaerobic conditions. 2-Sulfanilamidothiazole inhibited denitrification to some extent and samples supplied with potassium azide produced N2O rather than N2 as the predominant gas.