Carbon limitations to nitrous oxide emissions in a humid tropical forest of the Brazilian Amazon

The availability of labile organic C for microbial metabolic processes could be an important factor regulating N₂O emissions from tropical soils. We explored the effects of labile C on the emissions of N₂O from a forest soil in the State of Rondônia in the southwestern quadrant of the Brazilian Amazon. We measured emissions of N₂O from a forest soil after amendments with solutions containing glucose, water only or NO₃^–. Addition of glucose to the forest soil resulted in very large increases in N₂O emissions whereas the water only and NO₃^– additions did not. These results suggest a strong C limitation on N₂O production in this forest soil in the southwestern Amazon.     

菜地土壤中氮肥的反硝化损失和N2O排放

A field experiment was conducted on Chinese cabbage （Brassica campestris L. ssp. pekinensis （Lour.） Olsson） in a Nanjing suburb in 2003. The experiment included 4 treatments in a randomized complete block design with 3 replicates： zero chemical fertilizer N （CK）; urea at rates of 300 kg N ha^-1 （U300） and 600 kg N ha^-1 （U600）, both as basal and two topdressings; and polymer-coated urea at a rate of 180 kg N ha^-1 （PCU180） as a basal application. The acetylene inhibition technique was used to measure denitrification （N2 ＋ N2O） from intact soil cores and N2O emissions in the absence of acetylene. Results showed that compared to （3K total denitrification losses were significantly greater （P ≤ 0.05） in the PCU180, U300, and U600 treatments,while N2O emissions in the U300 and U600 treatments were significantly higher （P ≤ 0.05） than （3K. In the U300 and U600 treatments peaks of denitrification and N2O emission were usually observed after N application. In the polymer-coated urea treatment （PCU180） during the period 20 to 40 days after transplanting, higher denitrification rates and N2O fluxes occurred. Compared with urea, polymer-coated urea did not show any effect on reducing denitrification losses and N2O emissions in terms of percentage of applied N. As temperature gradually decreased from transplanting to harvest, denitrification rates and N2O emissions tended to decrease. A significant （P ≤0.01） positive correlation occurred between denitrification （r = 0.872） or N2O emission （r = 0.781） flux densities and soil temperature in the CK treatment with a stable nitrate content during the whole growing season.     

农业废弃物再燃脱硝特性试验

为了缓解化石能源的不足,开发生物质清洁高效燃烧的利用方式,采用农业废弃物(稻壳、秸秆)和R90煤粉作为再燃燃料在恒温沉降炉上进行再燃脱硝试验。针对燃料种类、化学计量比(stoichiometric ratio)、停留时间、燃料粒度、再燃比等因素对再燃脱硝效率的影响进行了研究。结果表明:农业废弃物(秸秆、稻壳)的再燃脱硝能力明显高于煤粉,其中秸秆再燃脱硝效率最高,稻壳再燃脱硝效率中等,煤粉最低,不同的挥发分含量是造成农业废弃物(秸秆、稻壳)与煤粉再燃脱硝率差别的最主要原因。再燃脱硝率随再燃区化学计量比(SR2)的提高逐渐降低。SR2增加,燃料热解析出的还原组分被氧竞争性地消耗,导致NO还原反应弱化,再燃脱硝率降低。SR2对农业废弃物秸秆和稻壳再燃脱硝率影响明显强于煤粉,再燃比20%工况,SR2从0.8增加到0.9,秸秆再燃脱硝率减少了20.12%,稻壳减少20.07%,煤粉减少了8.38%。燃料粒度的改变将影响颗粒的升温过程,在相同条件下,较细的燃料颗粒能更快速释放出更多的挥发分,可以提供再燃还原NO所需的更多的还原物质,对提高再燃脱硝率是有利的。再燃停留时间增加,在富燃料条件下再燃燃料与NO的反应时间延长,有利于NO消减。采用农业废弃物秸秆、稻壳作为作为再燃燃料,合理的再燃停留时间在600 ms以内,明显低于煤粉。通过调整再燃比可以获得适合的再燃脱硝率,农业废弃物秸秆、稻壳的合理再燃比在15%~20%之间。     

Effect of mineral nitrogen fertilizer forms on N2O emissions from arable soils in winter wheat production

Nitrogen fertilizers are supposed to be a major source of nitrous oxide (N₂O) emissions from arable soils. The objective of this study was to compare the effect of N forms on N₂O emissions from arable fields cropped with winter wheat (Triticum aestivum L.). In three field trials in North‐West Germany (two trials in 2011/2012, one trial in 2012/2013), direct N₂O emissions during a one‐year measurement period, starting after application of either urea, ammonium sulfate (AS) or calcium ammonium nitrate (CAN), were compared at an application rate of 220 kg N ha^?1. During the growth season (March to August) of winter wheat, N₂O emission rates were significantly higher in all three field experiments and in all treatments receiving N fertilizer than from the non‐fertilized treatments (control). At two of the three sites, cumulative N₂O emissions from N fertilizer decreased in the order of urea > AS > CAN, with emissions ranging from 522–617 g N ha^?1 (0.24–0.28% of applied fertilizer) for urea, 368–554 g N ha^?1 (0.17–0.25%) for AS, and 242–264 g N ha^?1 (0.11–0.12%) for CAN during March to August. These results suggest that mineral nitrogen forms can differ in N₂O emissions during the growth period of winter wheat. Strong variations in the seasonal dynamics of N₂O emissions between sites were observed which could partly be related to weather events (e.g., precipitation). Between harvest and the following spring (post‐harvest period) no significant differences in N₂O emissions between fertilized and non‐fertilized treatments were detected on two of three fields. Only on one site post‐harvest emissions from the AS treatment were significantly higher than all other fertilizer forms as well as compared to the control treatment. The cumulative one‐year emissions varied depending on fertilizer form across the three field sites from 0.05% to 0.51% with one exception at one field site (AS: 0.94%). The calculated overall fertilizer induced emission averaged for the three fields was 0.38% which was only about 1/3 of the IPCC default value of 1.0%.     

畜禽养殖废水脱氮除磷研究进展

笔者介绍了SBR、上流式活性污泥床、fiehl prototype工艺等几种目前国内外较典型的集约化养殖场废水处理方法,比较了它们在脱氮除磷方面的优缺点及其应用和研究情况,简述了畜禽养殖废水脱氮除磷现状.最后对畜禽养殖废水脱氮除磷存在的问题进行了探讨,同时对其发展趋势进行了展望.     

适用于猪场沼液处理的好氧反硝化菌筛选及其脱氮特性评价

试验旨在筛选适合于猪场沼液处理的好氧反硝化菌。从活性污泥中分离获得 16 株好氧反硝化菌,其中菌株 ZH-14 的总氮(TN)和硝酸盐氮的去除效果最好,分别达到 50.73%和 99.99%。该菌株经过平板形态观察、功能基因和 16S rDNA 基因分析,鉴定为施氏假单胞菌(Pseudomonas stutzeri)。结果表明:菌株 ZH-14 在硝酸钾为唯一氮源培养基中生长时,48 h 后硝酸盐氮与 TN 的降解率分别为 100%和41.76%;以亚硝酸钠为唯一氮源培养时,亚硝酸盐氮降解率为 99.24%;以氨氮为唯一氮源培养时,氨氮的降解率达 94.1%;使用菌株 ZH-14 处理畜禽沼液,当其接种终浓度为 107 CFU/mL 时,经过 48 h 处理,氨氮、硝酸盐氮和化学需氧量的去除率分别为 54.4%、97.7%和 77.9%。综上表明,菌株 ZH-14 具有较强的反硝化和处理猪场沼液的能力,具有良好的应用开发前景。     

草坪土壤的N2O产生途径及其对施氮肥的响应

硝化作用、反硝化作用和硝化细菌反硝化作用是土壤中产生N2O的主要途径.以常用的冷季型草坪草早熟禾为对象,采用气体抑制剂培养法研究了不同施氮量对草坪土壤N2O排放及其产生途径的影响.结果表明,对照草坪土壤的N2O日排放量为7.2 ～ 8.2 g· m-2.d-1,年施氮量10 g.m-2未改变草坪土壤N2O排放强度,年施氮量25、35 g·m-2处理则分别比对照增加1.52倍和1.88倍,但二者之间没有显著差异.对照草坪土壤N2O产生途径主要以异养硝化作用为主,其贡献率达65.7％,反硝化作用贡献率为34％,自养硝化和硝化细菌反硝化过程几乎不发生.年施氮量25 g.m-2时,N2O排放以硝化细菌反硝化、异养硝化和反硝化途径为主,贡献率分别为35％、35％和29％.年施氮量35 g.m2时,N2O排放来自于4个途径,其中反硝化途径占41％,自养硝化途径贡献率增加至20％.     

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.     

Long-Term Effects of Nitrogen Management Practices on Grain Yield,Nitrogen Uptake,and Efficiency in Irrigated Corn

ABSTRACT

Crop management strategies that improve Nitrogen Use Efficiency (NUE) increase profits while reducing the detrimental effects on the environment associated with fertilizer nitrogen (N) loss. Effective N management should include several critical factors that are very interrelated. A study was conducted at the Panhandle Research and Extension Center, Goodwell, OK to evaluate the effects of multiple nitrogen management practices including N rate, source, time of application, methods of fertilizer and residue incorporation over a long period of time on grain yield, N uptake and NUE in irrigated corn. Fourteen treatments were evaluated in a randomized complete block design with three replicates. Results of data analyzed on the individual year and averages of all years showed that grain yield and N uptake were improved with N rates and N management practices compared to checks. Both N recovery and efficiency of use were high for the 118 kg N ha^{? 1} rate.     

脱氮功能菌去除市政废水中氮素的研究

为了探讨实验室筛选获得的氨氧化细菌CM-NR014和反硝化细菌CM-NRD3联合去除市政废水中氮素的应用价值,采用了两级A／O工艺进行菌株去除废水中氮素的小试实验,最后将菌株用于废水脱氮工程中。结果表明,脱氮功能菌实现了短程硝化-反硝化,氨氮去除率在98％以上,总氮去除率在75％以上,COD（化学需氧量）去除率大于90％,出水各项指标均低于城镇污水处理厂污染物排放一级（A）标准。脱氮功能菌在去除市政废水中氮素方面有很高的应用价值,可用于城镇污水处理厂提标改造等。