露地种植大白菜的氮肥效应与氮素损失研究

采用田间小区和微区试验,研究了施用化学氮肥在露地大白菜上的氮肥效应和氮素损失。氮素总损失用15N示踪法测定,氨挥发用通气密闭室法测定,反硝化损失用乙炔抑制原状土柱培养法测定,不加乙炔测定N2O排放。结果表明,施用化学氮肥增产显著,用差值法计算得到的氮肥利用率在25.3%4～7.2%之间,相应的示踪法氮肥利用率为18.1%2～4.6%。化学氮肥显著增加了氨挥发、反硝化和N2O排放等气态氮损失;其中氨挥发占施氮量的0.97%1～7.1%,反硝化占4.33%8～.55%,N2O排放在1.09%1～.63%之间变化。大白菜收获时9.2%～10.9%的标记尿素被淋洗到40.cm以下土层。试验期间尿素的氮素总损失达41.1%4～8.1%,以表观淋洗损失最为严重,其次是氨挥发,而反硝化损失最低。与普通尿素相比,包衣尿素明显降低了氨挥发。     

低量施氮对小青菜生长和氮素损失的影响

采用田间试验和微区试验相结合,研究了低量施氮对小青菜(Brassica.chinensis)产量、氮肥利用率和氮素损失的影响,其中氮素总损失用15N示踪法测定,氨挥发用通气密闭室法测定,反硝化损失用乙炔抑制-原状土柱培养法测定,不加乙炔测定N2O排放。结果表明,施用氮肥显著增加了小青菜的产量和吸氮量,在75和150kg/hm2氮肥水平下,氮肥利用率分别为46.8%和39.4%。由于试验地土壤pH低(5.38),各处理的氨挥发均很低且差异不大,施用氮肥没有增加氨挥发。试验地土壤反硝化损失和N2O排放量较高,分别为N4.34kg/hm2/sup和N2.65kg/hm2,施用氮肥没有增加反硝化损失和N2O排放,表明氮源不是反硝化作用的限制因子。在N75和150kg/hm2两个施氮水平下,氮素回收率分别为103%和91.3%,并且土壤残留氮主要累积在020cm土层,表明肥料氮损失很少,这与氨挥发、反硝化损失较低的结果相吻合。     

施肥对夏玉米季紫色土N2O排放及反硝化作用的影响

采用原状土柱-乙炔抑制培养法研究了施肥对紫色土玉米生长季土壤N2O排放通量和反硝化作用的影响.结果表明:玉米季施肥显著增加土壤N2O排放和反硝化损失,同时,各施肥处理间N2O排放与反硝化损失量差异显著.猪厩肥、猪厩肥配施氮磷钾肥、氮肥、氮磷钾肥和秸秆配施氮磷钾肥等处理的土壤N,O排放量分别为3.01、2.86、2.51、2.19和1.88 kg hm-2,分别占当季氮肥施用量的1.63％、1.53％、1.30％、1.09％和0.88％,反硝化损失量分别为6.74、6.11、5.23、4.69和4.12 kg hm-2,分别占当季氮肥施用量的3.97％、3.55％、2.97％、2.61％和2.23％,不施肥土壤的N2O排放量和反硝化损失量仅为0.56和0.78 kg hm-2.施肥是紫色土玉米生长前期(2周内)土壤N2O排放和反硝化速率出现高峰的主要驱动因子,土壤铵态氮和硝态氮含量是影响土壤N2O排放、土壤硝化和反硝化作用的限制因子,土壤含水量是重要影响因子,降雨是主要促发因素.土壤N2O排放量与反硝化损失量的比值介于0.45 ～0.72之间,土壤反硝化损失量极显著高于土壤N2O排放量,说明土壤反硝化作用是紫色土玉米生长季氮肥损失的重要途径.     

农田土壤N2O排放和减排措施的研究进展

氧化亚氮(N2O)是一种受人类活动影响的重要温室气体。农业土壤是其主要的排放源之一,土壤中硝化和反硝化作用是N2O产生的主要过程。N2O的排放受多种因素的影响,农业活动尤其是施用化学氮肥是农田N2O排放量增加的主要因素。提高氮肥利用率,使用硝化抑制剂等措施将有助于减少N2O的排放量,更有效的减排措施还有待进一步的研究与应用。     

华北露地茄田氮肥减施综合方案的增效减排成效分析

2018年6-11月在华北露地茄田设置不施肥处理（CK）、常规施氮处理（N1）、减氮20%处理（N2）、减氮50%处理（N3）、减氮20%并施用抑制剂包膜尿素处理（N2I）及减氮20%并增施生物炭（N2B）6个处理。测定并分析不同氮肥减施综合方案对作物氮肥利用率、土壤氨挥发及N2O排放的影响。结果表明：（1）与常规施氮处理（N1）相比,减氮20%（N2）对茄子产量无显著影响,减氮50%处理（N3）茄子显著减产。施用抑制剂包膜尿素（N2I）或添加生物炭（N2B）可提高作物氮肥利用率。（2）土壤氨挥发、N2O排放与施肥关系密切,各施肥处理的氨挥发、N2O排放量均高于不施肥处理（CK）,两种气体的排放系数分别为9.6%～14.8% （氨）和0.9%～1.1%（ N2O）,排放通量峰值均出现于施肥之后。（3）与常规施氮（N1）相比,N2、N3、N2I和N2B的土壤氨挥发累积量分别降低20.3%、48.6%、41.7%和30.7%。在不影响产量的前提下,减氮20%并施用抑制剂包膜尿素处理（N2I）减排效果最好。（4）与常规施氮（N1）相比,N2、N3、N2I和N2B的N2O累积排放量分别降低21.5%、41.7%、44.2%和31.6%。N2I处理的累积排放量远低于常规施氮（N1）处理,与减氮50%处理（N3）的N2O累积水平相当。综上,减氮20%并施用抑制剂包膜尿素处理对蔬菜产量无显著影响,氮肥利用率有一定程度提高,且对环境风险小,主要体现为氨挥发和N2O减排效果显著,成本适中,是华北地区露地茄田增效减排的优选推荐方案。     

农田土壤硝化—反硝化作用与N2O的排放

在北京潮土上研究了冬小麦夏玉米轮作体系下土壤硝化反硝化作用以及N2O排放情况。结果表明，小麦生育期土壤温度及含水量降低，无论是反硝化损失氮量还是土壤的N2O生成排放量均不高。土壤的N2O生成排放量与反硝化氮量相当或低于反硝化氮量。玉米生育期土壤温度升高以及孔隙含水量的较大的改善，反硝化损失氮量、N2O生成排放量有明显上升。通常情况下土壤反硝损失氮量与N2O排放氮量基本处于同一水平。在玉米十叶期追肥后的较短时间内，N2O总排放量明显高于反硝化损失氮量，说明至少在这一阶段中，硝化作用在北方旱地土壤N2O的排放中发挥了主要作用。在评价北方旱地农田土壤氮素硝化反硝化损失中，硝化作用的氮素损失是不可忽视的重要方面。     

优化施肥下华北冬小麦/夏玉米轮作体系农田反硝化损失与N2O排放特征

在田间条件下,应用乙炔抑制-原状土柱培养法测定优化施肥下华北冬小麦/夏玉米轮作体系土壤反硝化和N2O的排放特征。研究表明:冬小麦和夏玉米整个生育期反硝化速率和N2O排放通量均表现出明显的季节性变化,且均与土壤水分和无机氮浓度呈显著正相关。小麦季和玉米季的反硝化损失量及N2O排放量均表现出随施肥量的降低而降低,夏玉米季的反硝化损失量和N2O排放量均高于小麦季。小麦季的反硝化损失量和N2O排放量习惯施肥处理是氮肥减量后移处理的1.62和1.67倍,玉米季分别为2.01和2.00倍。氮肥减量后移可能是通过改变土壤无机氮浓度而降低反硝化损失量和N2O排放量。     

秸秆还田对灌溉玉米田土壤反硝化及N2O排放的影响

运用乙炔抑制技术研究了不同施氮水平下秸秆还田对灌溉玉米田土壤反硝化反应和氧化亚氮(N2O)排放的影响。结果表明,土壤反硝化速率及N2O的排放受氮肥施用、秸秆处理方式及其交互作用的显著影响。与秸秆燃烧相比,不施氮或低施氮水平时,秸秆还田可刺激培养初期反硝化反应速率及N2O排放,增加培养期间N2O平均排放通量;高施氮水平时,秸秆还田可降低反硝化反应速率及反硝化过程中的N2O排放。秸秆还田可降低反硝化中N2O/N2的比例。     

玉米地土壤反硝化速率与N2O排放通量的动态变化

应用乙炔抑制原状土柱培育法测定了4种施肥处理的玉米地N素反硝化损失速率和氧化亚氮（N2O）排放通量，并分析了它们与土壤湿度、土壤温度以及硝态氮（NO3^-－N）含量之间的关系，计算了因反硝化和N2O排放造成的N肥损失率。结果表明，玉米生育期内土壤N素的反硝化损失量为0．67－3．85kg/hm^2，N肥的反硝化损失率为0．5％－1．5％；土壤N2O排放总量为0．55－1．42kg/hm^2，N肥的N2O排放系数为0．2％－0．5％。     

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。     

水氮调控对设施土壤氨挥发特征的影响

基于连续6年设施番茄水氮调控定位试验,采用高分辨激光光谱法观测分析灌水下限(土壤水吸力为W_1:25 kPa、W_2:35 kPa、W_3:45 kPa)和施氮量(N_1:75 kg N/hm~2、N_2:300 kg N/hm~2、N_3:525 kg N/hm~2)对设施土壤氨挥发通量、累积挥发量、番茄产量及单产累积排放量的影响。结果表明:灌水下限、施氮量及两者交互作用极显著的影响设施土壤氨挥发通量峰值、累积挥发量、单产氨挥发累积量、氨挥发损失率和番茄产量。氨挥发通量表现为施氮后6～8天氨挥发达到峰值。经验S模型可以较好地表征基肥和追肥2个时期氨挥发累积量随时间的变化,氨挥发特征参数表现为基肥期以灌水下限和水氮交互影响为主,追肥期以施氮量和水氮交互影响为主。与基肥相比,采用滴灌追肥可显著的降低氨挥发累积量94.78%～96.30%。受土壤pH和土壤NH_4~+-N含量及施肥带比例影响,氨挥发的氮损失率在0～2%。施氮量为300 kg N/hm~2和灌水下限25 kPa组合的水氮处理(W_1N_2)是协调氨挥发量和设施番茄产量的最佳水氮管理模式。     

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.     

稻季施肥管理措施对后续麦季N2O排放的影响

2003─2004年选用江苏省宜兴市稻-麦轮作试验田,研究了水稻生长季秸杆(0和3.75×103kg/hm2两个水平)和N肥施用(N0、200和270kg/hm23个水平)对后续麦季N2O排放的影响。结果表明:稻季秸杆施用显著减少了后续麦季N2O的排放,这些减少量主要体现在小麦播种-返青期,方差分析达显著水平(P<0.05)。稻季施用N肥,后续麦季N2O排放减少,但N200和270kg/hm2N肥施用水平的处理间无显著差异。麦季土壤水分情况与N2O排放通量存在显著正相关(P<0.05)。     

添加脲酶抑制剂NBPT对麦秆还田稻田氨挥发的影响

氨挥发是稻田氮素损失的重要途径,为探明脲酶抑制剂NBPT对小麦秸秆还田稻田中氨挥发的影响,采用密闭室通气法,在太湖地区乌珊土上,研究了脲酶抑制剂n-丁基硫代磷酰三胺(NBPT)对小麦秸秆还田稻田中施肥后尿素水解和氨挥发动态变化的影响。结果表明:稻田氨挥发损失主要集中在基肥和分蘖肥时期。添加NBPT可明显延缓尿素水解,推迟田面水NH4+-N峰值出现的时间,并降低NH4+-N峰值,降低了田面水氨挥发速率和挥发量。NBPT的效果在基肥和分蘖肥施用后尤为明显,不加NBPT时施入的尿素在2~3 d内基本水解彻底,NH4+-N和氨挥发速率在第2 d即达到峰值,两次施肥后NH4+-N峰值分别为132.3 mg·L-1和66.3mg·L-1,氨挥发峰值为15.6 kg·hm-2·d-1和10.4 kg·hm-2·d-1;而添加NBPT后,NH4+-N峰值推迟至施肥后第4 d出现,NH4+-N峰值降至70.7 mg·L-1和51.6 mg·L-1,氨挥发峰值降至4.7 kg·hm-2·d-1和2.6 kg·hm-2·d-1。添加NBPT使稻田氨挥发损失总量从73.3 kg(N)·hm-2(占施氮量的24.4%)降低至34.5 kg(N)·hm-2(占施氮量的11.5%),降低53%。在添加小麦秸秆稻田中添加NBPT通过延缓尿素水解而显著降低了氨挥发损失。     

Nitrogen oxides emission from soils bearing a potato crop as influenced by fertilization with treated pig slurries and composts

Nitrous oxide, nitric oxide and denitrification losses from an irrigated soil amended with organic fertilizers with different soluble organic carbon fractions and ammonium contents were studied in a field study covering the growing season of potato (Solanum tuberosum). Untreated pig slurry (IPS) with and without the nitrification inhibitor dicyandiamide (DCD), digested thin fraction of pig slurry (DTP), composted solid fraction of pig slurry (CP) and composted municipal solid waste (MSW) mixed with urea were applied at a rate of 175 kg available N ha⁻¹, and emissions were compared with those from urea (U) and a control treatment without any added N fertilizer (Control). The cumulative denitrification losses correlated significantly with the soluble carbohydrates, dissolved N and total C added. Added dissolved organic C (DOC) and dissolved N affected the N₂O/N₂ ratio, and a lower ratio was observed for organic fertilizers than from urea or unfertilized controls. The proportion of N₂O produced from nitrification was higher from urea than from organic fertilizers. Accumulated N₂O losses during the crop season ranged from 3.69 to 7.31 kg N₂O-N ha⁻¹ for control and urea, respectively, whereas NO losses ranged from 0.005 to 0.24 kg NO-N ha⁻¹, respectively. Digested thin fraction of pig slurry compared to IPS mitigated the total N₂O emission by 48% and the denitrification rate by 33%, but did not influence NO emissions. Composted pig slurry compared to untreated pig slurry increased the N₂O emission by 40% and NO emission by 55%, but reduced the denitrification losses (34%). DCD partially inhibited nitrification rates and reduced N₂O and NO emissions from pig slurry by at least 83% and 77%, respectively. MSW+U, with a C:N ratio higher than that of the composted pig slurry, produced the largest denitrification losses (33.3 kg N ha⁻¹), although N₂O and NO emissions were lower than for the U and CP treatments.This work has shown that for an irrigated clay loam soil additions of treated organic fertilizers can mitigate the emissions of the atmospheric pollutants NO and N₂O in comparison with urea.     

施肥方式对冬小麦季紫色土N2O排放特征的影响

利用紫色土养分循环长期定位施肥试验平台,通过静态箱-气相色谱法,于2012年11月至2013年5月,研究了单施氮肥(N)、猪厩肥(OM)、常规氮磷钾肥(NPK)、猪厩肥配施氮磷钾肥(OMNPK)、秸秆还田配施氮磷钾肥(CRNPK)及对照不施肥(NF)6种施肥方式下,紫色土冬小麦季土壤N2O的排放特征。结果表明,在相同施氮水平[130 kg(N)·hm-2]下,施肥方式对N2O排放量有显著影响(P0.05)。N、OM、NPK、OMNPK和CRNPK处理下,土壤N2O排放量[kg(N)·hm-2]分别为0.38、0.36、0.29、0.33和0.19,N2O排放系数分别为0.25%、0.23%、0.18%、0.21%和0.10%。NF的土壤N2O排放量为0.06 kg(N)·hm-2。土壤无机氮含量(NO3--N和NH4+-N)是N2O排放的主要影响因子,降雨能有效激发N2O排放。基于小麦产量评价不同施肥方式下的N2O排放,结果表明,N、OM、NPK、OMNPK和CRNPK单位小麦产量N2O的GWP值[yield-scaled GWP,kg(CO2 eq)·t-1]分别为132.57、45.70、49.07、48.92和26.41。CRNPK的小麦产量与6种施肥方式中获得最大产量的OM间没有显著差异,但显著高于其他处理。而且,CRNPK的yield-scaled GWP比紫色土地区冬小麦种植中常规施肥方式(NPK)显著减少46%,并显著低于其他4种施肥方式。可见,秸秆还田配施氮磷钾肥在保证小麦产量的同时,能有效减少因施肥引发的N2O排放,可作为紫色土地区推荐的最佳施肥措施。     

Application of membrane inlet mass spectrometry to directly quantify denitrification in flooded rice paddy soil

Denitrification has long been considered a major mechanism of N loss when N fertilizer is applied to flooded rice paddies. However, the direct determination of denitrification in soils is almost impossible because of the high atmospheric background of dinitrogen (N₂). Dissolved N₂ in a small water sample can be rapidly and precisely measured through membrane inlet mass spectrometry (MIMS). This study is the first to directly measure N₂ flux through MIMS in flooded rice paddy plots that received different amounts of urea. Ammonia (NH₃) volatilization was measured simultaneously to verify whether NH₃ volatilization and denitrification are complementary loss mechanisms. The average cumulative N₂–N loss measured by MIMS 21 days after fertilization was 4.7?±?1.7 % of the applied N, which was within the range of the reported values obtained by cumulative recovery of (N₂ + N₂O)–¹⁵N and ¹⁵N-balance technique. Underestimation or overestimation of denitrification can be prevented in MIMS given that N₂ can be measured directly without ¹⁵N-labeled fertilizer. A good positive correlation was found between the dissolved in situ N₂ concentrations of floodwater and the denitrification rates of intact soil cores. Urea incorporation reduced NH₃ volatilization unlike surface broadcasting. However, urea incorporation significantly increased cumulative N₂–N loss during the 21 days after fertilization. Correlation analysis showed that nitrate (NO₃ ^?–N) concentration in floodwater could be the primary restricting factor for soil denitrification in the experimental field. Results suggest that MIMS is a promising technique for the measurement of denitrification in a flooded rice paddy.     

春秋季红壤旱地氨挥发对氮施用量、气象因子的响应

通过红壤旱地种植牧草马唐和蔬菜冬萝卜轮作试验,研究了在春秋二季红壤旱地氨挥发对不同施氮量和气象因子的响应。结果表明,红壤旱地春季牧草实验,氮肥处理N90、N160和N230,氨挥发持续10~17d,在施肥后6~8d达到峰值,峰值(扣除对照N0)分别为N0.11、0.57和1.84kghm-2d-1。秋季氮肥处理N70、N130、N190和N250以基肥和以水带肥追施(基/追比为7∶3)氨挥发持续时间均为10~11d,基肥氨挥发峰值(扣除对照N0)分别为N0.02、0.05、0.06kghm-2d-1和0.09kghm-2d-1;追肥氨挥发峰值(扣除对照N0)分别为N0.05、0.22、0.38kghm-2d-1和0.72kghm-2d-1。不同施氮处理,春季累计氨挥发量为N0.67~5.16kghm-2,占施入肥料N的0.74%~2.24%;秋季累计氨挥发量为N0.37~3.04kghm-2,占施入肥料N的1.31%~3.69%。红壤旱地春秋二季氨挥发量(y)均随施N量(x)的提高而指数递增,其关系式分别为:y=0.1576e0.0146x和y=0.1826e0.0112x。显著性检验表明,春秋两季不同施氮量处理之间,土壤氨挥发量及挥发通量差异均达到显著水平。春秋二季基肥氨挥发总量和通量均与气温、气压、蒸发量和土温等环境气象因子有较好的相关性(p<0.05)。