Reducing NH3, N2O and {\text{NO}}_3^ - –N losses from a pasture soil with urease or nitrification inhibitors and elemental S-amended nitrogenous fertilizers

A 3-month field experiment comparing nitrogen (N) losses from and the agronomic efficiency of various N fertilizers was conducted on a sandy loam (Typic Hapludand) soil at Ruakura AgResearch farm, Hamilton, New Zealand during October to December 2003. Three replicates of seven treatments: urea, urea + the urease inhibitor N-(n-butyl) thiophosphoric triamide (trade name Agrotain), urea + Agrotain + elemental sulphur (S), urea + double inhibitor [DI; i.e., Agrotain + dicyandiamide (DCD)], diammonium phosphate (DAP), DAP + S, each applied at 150 kg N ha⁻¹, and control (no N). After fertilizer application, soil ammonium () and nitrate () concentrations (7.5-cm soil depth), ammonia (NH₃) volatilization, nitrate () leaching, nitrous oxide (N₂O) emission, pasture dry matter, and N uptake were monitored at different timings. Urea applied with Agrotain or Agrotain + S delayed urea hydrolysis and released soil at a slower rate than urea alone or urea + DI. Urea applied with DI increased NH₃ volatilization by 29% over urea alone, while urea + Agrotain and urea + Agrotain + S reduced NH₃ volatilization by 45 and 48%, respectively. Ammonia volatilization losses from DAP were lower than those from urea with or without inhibitors. Total reduction in leaching losses for urea + DI and urea + Agrotain compared to urea alone were 89% and 47%, respectively. Application of S with urea + Agrotain reduced leaching losses by an additional 6%. Nitrous oxide emissions were higher from the DAP and urea alone treatments. Urea applied with DI and urea + Agrotain reduced N₂O emissions by 37 and 5%, respectively, over urea alone. Compared to urea alone, total pasture production increased by 20, 17, and 15% for urea + Agrotain + S, urea + Agrotain, and urea + DI treatments, respectively, representing 86, 71, and 64% increases in N response efficiency. Total N uptake in urea + Agrotain, urea + Agrotain + S, and urea + DI increased by 29, 22, and 20%, respectively, compared to urea alone. These results suggest that the combination of both urease and nitrification inhibitors may have the most potential to reduce N losses and improve pasture production in intensively grazed systems.     

双氰胺和表面活性剂添加对沼液氮素形态变化的影响

为探究双氰胺和表面活性剂添加到沼液中对其氮素形态和含量的影响,通过室内模拟试验,设置单施沼液（对照）、沼液+8%双氰胺（DCD）、沼液+16% DCD、沼液+表面活性剂、沼液+8% DCD+表面活性剂、沼液+16% DCD+表面活性剂,共6个处理,在静置10、30 min和1、3、10、24、48 h时测定沼液中总氮（TN）、总凯氏氮（TKN）、铵态氮（NH₄⁺-N）、硝态氮（NO₃^--N）含量。结果表明：与对照单施沼液相比,沼液中添加8% DCD和16% DCD后,NH₄⁺-N浓度增加了0.74%~8.96%,TKN浓度增加了24.67~59.70 mg·L^-1,NO₃^--N浓度增加了13.42~145.88倍,且NH₄⁺-N、TKN、NO₃^--N浓度与DCD添加量呈正相关。表面活性剂添加对沼液氮素形态和浓度没有显著影响。研究结果可为提高抑制剂抑制效果和科学施用抑制剂提供数据支撑。     

黄土高原南部旱地冬小麦生长期N2O排放特征与基于优化施氮的减排方法研究

为了解陕西黄土高原南部旱地冬小麦季N2O排放规律,探索旱地N2O减排方法,采用密闭式静态箱法,以不同施氮处理[CK:对照,不施氮;CON:当地农民习惯施氮,施氮量220 kg·hm-2;OPT:优化施氮加秸秆还田,施氮量150 kg·hm-2;OPT+DCD:优化施氮加秸秆还田,同时施用施氮量5%的硝化抑制剂DCD;OPT(SR):优化施氮(所用肥料为包膜型缓控释肥)加秸秆还田]为基础,研究黄土高原南部旱地冬小麦农田N2O季节排放特征和减排措施。结果表明:黄土高原南部旱地冬小麦季N2O排放具有首月持续、大量排放,末月雨后瞬间排放,中期低排放的特点。各处理中,OPT+DCD和OPT(SR)在播种—返青期能显著减少N2O排放水平,而返青—成熟期,各优化处理差异不显著。从整个小麦季N2O排放总量来看,各优化处理能够减少N2O排放量,提高作物产量,降低单位产量N2O排放量。具体表现为:1与CON处理的N2O排放量相比,OPT、OPT+DCD和OPT(SR)处理分别减排29.2%(P0.01)、38.7%(P0.01)和39.3%(P0.01),但3个优化处理间差异不显著;2与CON处理的产量相比,OPT、OPT+DCD和OPT(SR)处理分别增产3.8%(P0.05)、15.2%(P0.05)和9.5%(P0.05);3与CON处理的单位产量N2O排放量相比,OPT处理单位产量N2O排放量减少31.7%(P0.05);而相对于OPT处理,OPT+DCD处理和OPT(SR)处理分别减少了单位产量排放量的22.1%(P0.05)和18.9%(P0.05)。本研究表明,减少施氮量至150 kg·hm-2,并施用秸秆是减少N2O排放的重要手段,而施用缓控释肥或一定量的DCD可提升作物产量。     

The effect of nitrification inhibitors on the nitrous oxide (N2O) release from agricultural soils—a review

The use of nitrification inhibitors (NI) is a technique which is able to improve N fertilizer use efficiency, to reduce nitrate leaching and to decrease the emission of the climate‐relevant gas N₂O simultaneously, particularly in moderately fertilized agricultural systems adapted to plant N demand. The ammonia monooxygenase (AMO) is the first enzyme which is involved in the oxidation of NH$ _4^+ $ to NO$ _3^ - $ in soils. The inhibition of the AMO by NIs directly decreases the nitrification rate and it reduces the NO$ _3^- $ concentration which serves as substrate for denitrification. Hence, the two main pathways of N₂O production in soils are blocked or their source strength is at least decreased. Although it has been shown that archaea are also able to oxidize NH₃, results from literature suggest that the enzymatic activity of NH₃ oxidizing bacteria is the most important target for NIs because it was much stronger affected. The application of NIs to reduce N₂O emissions is most effective under conditions in which the NI remains close to the N ‐ fertilizer. This is the case when the NI was sprayed on mineral ‐ N fertilizer granules or thoroughly mixed with liquid fertilizers. Most serious problems of spatial separation of NI and substrate emerge on pasture soils, where N₂O hotspots occur under urine and to a lesser extent under manure patches. From the few studies on the effect of different NI quantities it seems that the amount of NI necessary to reduce N₂O emissions is below the recommendations for NI amounts in practice. NIs can improve the fertilizer value of liquid manure. For instance, the addition of NIs to slurry can increase N uptake and yield of crops when NO$ _3^ - $ ‐ N leaching losses are reduced. It has clearly been demonstrated that NIs added to cattle slurry are very effective in reducing N₂O as well as NO emissions after surface application and injection of slurry into grassland soils. In flooded rice systems NIs can reduce CH₄ emission significantly, whereas the effect on CO₂ emission is varying. On the other hand, as an effect of the delay of nitrification by NIs, NH₃ emission might increase when N fertilizers are not incorporated into the soil. As compared to other measures NIs have a high potential to reduce N₂O emissions from agricultural soils. Further, no other measure has so consistently been proofed according its efficiency to reduce N₂O emissions. From the published data [Akiyama et al. ( 2010 ) and more recent data from the years 2010–2013; 140 data sets in total] a reduction potential of approx. 35% seems realistic; however, further measurements in different management systems, particularly in regions with intense frost/thaw cycles seem necessary to confirm this reduction potential. These measurements generally should cover a whole annual cycle.     

Effects of urease and nitrification inhibitors on the efficient use of urea for pastoral systems

Abstract

The humic substances contained in an animal organic waste were extracted and the total extract separated into three humic fractions with different molecular weights (low, F₁ <10³; medium, F₂, with molecular weights ranging from 10³ to 10⁴; and high, F₃ >10⁴). The C content was highest in F₂, the same fraction also showing the lowest N content. The molecular weight of the humic fractions influenced the electrical conductivity, the highest molecular weight resulting in the lowest degree of electrical conductivity. Membrane-controlled ultrafiltra-tion (the method used to separate the various fractions from the whole extract) was also suitable for purifying such enzymes as phosphatase and β-glucosidase: the total activity obtained from the three fractions was considerably greater than that determined in the whole extract, Pyrolysis-gas chromatography (Py-GC) applied to the whole extract and humic fractions showed that in the F₃ fraction (highest molecular weight) benzene was the major fragment while furfural was the major fragment of F₁ (lowest molecular weight). For this reason, the humification index benzene/toluene indicates that the fraction with the highest molecular weight was the most humified while the furfural/pyrrole ratio indicates that the fraction with the lowest molecular weight was the most degradable. The whole extract and the fraction F₁ had a negative effect on seed germination when the concentration was equivalent to 100 mg kg^?1 of C, while the germination index was higher than that of the control when only 10 mg kg^?1 were used. The F₂ fraction had a positive effect on germination regardless of the concentration used. When 10 mg kg^?1 of C of the humic substances studied were added to the nutrient solution for growth experiments with maize plants, F₃ led to increases in root weight and F₂ led to increases in shoot weight. An inhibitor effect was observed for fraction F₁.     

秸秆和DCD对冬小麦不同生育期施入尿素的土壤行为的影响Ⅱ：硝态氮的动态变化

[目的]通过田间试验研究秸秆和DCD对冬小麦不同生育期施入尿素土壤行为的影响。[方法]试验设5个处理：对照（不施秸秆、DCD和尿素,CK）;单施尿素（U）;尿素＋秸秆（U＋S）;尿素＋DCD（U＋DCD）;尿素＋秸秆＋DCD（U＋S＋DCD）。[结果]在田间条件下,在尿素配施DCD的处理中,在一定时间内土壤NO3-N数量明显低于未加DCD处理;在配施秸秆处理中,秸秆加入后,延缓了硝化作用的发生以及土壤NO3-N的积累速率。[结论]该研究为揭示尿素在土壤中的行为特征及合理施用尿素提供理论依据。     

秸秆和DCD对冬小麦不同生育期施入尿素的土壤行为影响Ⅰ：——铵态氮的动态变化

[目的]通过田间试验研究秸秆和DCD对冬小麦不同生育期施入尿素后土壤铵态氮的动态变化。[方法]试验设5个处理：对照（不施秸秆和尿素,CK）;单施尿素（U）;尿素＋秸秆（U＋S）;尿素＋DCD（U＋DCD）;尿素＋秸秆＋DCD（U＋S＋DCD）。[结果]在田间条件下,在尿素配施DCD的处理中,在一定时间内土壤NH4-N含量明显高于未加DCD处理;在尿素配施秸秆处理中,土壤NH4＋-N含量均低于未加秸秆处理;在不同的温度和湿度条件下,尿素的水解速率亦有较大的差别。[结论]秸秆和DCD对通过不同时期施入尿素的土壤行为均产生影响。     

硝化抑制剂阻控养殖肥液灌溉土壤氮素淋失

为考察硝化抑制剂伴施养殖肥液灌溉条件下土壤氮素的淋溶特征和阻控效果,采用土柱模拟淋溶试验,设置尿素溶液单施、养殖肥液单施、以及养殖肥液分别伴施双氰胺(DCD,5%、10%和15%)和氯甲基吡啶(Nitrapyrin,0.25%、0.5%和1%)处理,连续监测了5个灌溉周期土壤淋溶液中铵态氮(NH_4~+-N)、硝态氮(NO_3~--N)、总氮(TN)和溶解性有机碳(DOC)淋失特征。养殖肥液单施比尿素溶液单施显著减少碳氮的淋失浓度和淋失量。养殖肥液伴施DCD和Nitrapyrin淋溶液中TN、NH_4~+-N、NO_3~--N、DOC浓度分别比单施养殖肥液降低27.19%、35.69%、45.89%、53.69%和24.86%、30.87%、21.10%、64%,处理间均达到5%显著水平。从抑制效果及经济节约角度,推荐5%DCD伴施养殖肥液是优化的养分淋溶阻控模式。此外,发现养殖肥液连续饱和灌溉条件下土壤淋溶液硝态氮浓度与氧化还原电位间存在显著的相关性(R2=0.602 8*,n=34)。养殖肥液伴施硝化抑制剂是抑制养分淋失、提高养分利用效率和控制硝态氮淋溶污染的有效措施,但抑制剂的作用效果、抑制时间与施用方式之间的关系还需要进一步研究。     

pH变化对中性土壤硝化过程N2O释放的影响

通过人为调节获得pH5．82、pH6．95和pH7．55的3种pH土壤,采用室内培养方法,研究了pH变化对土壤硝化过程N2O产生以及双氰胺（OCD）对硝化过程抑制作用的影响。结果表明,在好气培养2d内,土壤硝化速率与pH呈正相关关系;在12d的培养期间,土壤N2O释放总量随pH增大而增大,最大N2O释放量占施氮量的0．363％;pH变化影响土壤硝化作用的强弱以及硝化过程中N2O／N2的比例;pH变化对DCD的抑制作用影响显著,DCD对N2O释放总量的抑制率为34．4％-72．2％,当pH5．82时抑制作用最强。     

The effect of dicyandiamide and neem cake on the nitrification of urea-derived ammonium under field conditions

Summary Dicyandiamide (DCD) and neem cake were evaluated for their efficiency in inhibiting nitrification of prilled urea-derived NH ₄ ⁺ –N in a wheat field. Prilled urea was blended with 10% and 20% DCD-N or 10% and 20% neem cake and incorporated into the soil just before the wheat was sown. Both DCD and neem cake partially inhibited nitrification of prilled urea-derived NH ₄ ⁺ ; DCD was better than neem cake. The nitrification-inhibiting effects of DCD lasted for 45 days, while that of neem cake lasted for only 30 days. Blending the prilled urea with DCD (20% on N basis) was most effective in inhibiting the nitrification of urea-derived NH ₄ ⁺ , both in terms of intensity and duration, and maintained substantially more NH ₄ ⁺ –N than the prilled urea alone and 20% neem-cake-blended urea for a period of 60 days.