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。     

南京郊区番茄地中氮肥的气态氮损失

采用田间试验研究了番茄地施用化学氮肥后的氨挥发、反硝化损失和N2O排放及其影响因素。氨挥发采用通气密闭室法测定，反硝化损失（N2＋N2O）采用乙炔抑制-土柱培养法测定，不加乙炔测定N2O排放。结果表明，番茄生长期间全部处理均未检测到氨挥发，其原因是土表氨分压低于检测灵敏度，较低的氨分压是由于表层土壤的铵态氮浓度和pH都不高所致。在番茄生长期间，对照区即来自有机肥和土壤本身的反硝化损失和N2O℃排放量相当高，反硝化损失总量高达N29．6kghm^-2，N2O排放量为N7．76kghm^-2。施用化学氮肥显著增加了反硝化损失和N2O排放，3个施用化学氮肥处理的反硝化损失变化在N40．8～46．1kghm^-2之间，占施入化肥氮量的5．50％～6．01％；N2O排放量为N13．6～17．6kghm^-2，占施入化肥氮量的2．62％～4．92％；与尿素相比，包衣尿素未能显著减低反硝化损失和N2O排放。施用尿素的处理在每次追肥后，耕层土壤均会出现NO3^--N高峰，继之的反硝化和N2O排放高峰。反硝化速率与土壤含水量呈极显著正相关。总的看来，番茄生长期间没有氨挥发，而硝化反硝化是氮素损失的重要途径之一。     

利用膜进样质谱法测定不同氮肥用量下反硝化氮素损失

利用膜进样质谱仪(MIMS)测定了太湖流域典型稻田不同氮肥施用梯度下,土壤反硝化氮素损失量,同时也对氨挥发通量进行了观测。根据两年的田间试验结果得到:在常规施氮处理(N300)下,每年平均有54.8 kg/hm~2 N通过反硝化损失,有约54.0 kg/hm~2 N通过氨挥发损失,分别占肥料施用量的18.3%和18.0%,两者损失量相当。通过反硝化和氨挥发损失的氮素量随着氮肥用量增加而增加,田面水的NH_4~+-N、NO_3~–-N、DOC和pH浓度影响稻田土壤反硝化速率。在保产增效施氮处理(N_270)下,氮肥施用量比常规减少10%,水稻产量增加了5.5%,而通过反硝化和氨挥发损失的氮素量分别下降了1.1%和3.1%,氮肥利用率提高了约5.5%。在增施氮肥处理(N375)下,因作物产量增加使得氮肥利用率比N300增加,但通过氨挥发和反硝化的氮素损失量也最大。因此,通过综合集约优化田间管理措施,降低氮肥用量,可实现增产增效的目的。     

控释氮肥在淹水稻田土壤上的去向及利用率

通过土壤渗漏装置、微区和田间小区试验,研究了15N标记控释氮肥在淹水稻田土壤上氮素的去向和利用率。结果表明,施用控释氮肥能明显地降低氨挥发、淋失和硝化—反硝化的损失。控释氮肥处理的氨挥发量比尿素降低54.0%,氮淋失量降低32.5%。尿素的硝化—反硝化损失量占施入氮量的34.5%,而控释氮肥的只占2.0%;控释肥料与尿素氮在0—80cm土层中的残留率相近。控释氮肥一次性全量作基肥施入土壤,水稻的氮肥利用率平均为65.6%,比尿素(基肥+追肥)高出32.2个百分点。控释氮肥的农学效率显著地高于尿素。     

太行山前平原农田生态系统氮素循环与平衡研究

在中国科学院栾城生态农业试验站1公顷小麦玉米轮作农田,运用乙炔抑制原状土柱培育法、微气象学法和陶土头多孔杯水量平衡法分别定量测定了氮素硝化反硝化损失、氨挥发、NO3--N淋溶损失等氮素循环转化途径。研究结果表明,每年因氨挥发而造成的肥料氮损失量为N.60.kg/hm2,占施入肥料氮的15%;NO3--N淋溶损失量为N.68～4.kg/hm2,占肥料施用量的1.4%2～0.3%;每年因硝化反硝化过程造成的肥料损失量为N.2.021～0.49.kg/hm2,占肥料施入量的0.51%1～.37%。氨挥发、NO3--N淋溶和硝化反硝化损失主要发生在施肥灌溉/降雨之后,玉米季肥料损失明显高于小麦生长季节。氨挥发和NO3--N淋溶损失是本区域农田氮素损失的主要途径,是氮肥利用率低的重要原因。在当地农民所采用的常规农业管理措施下,小麦玉米轮作农田氮素平衡处于盈余状态,小麦季盈余N+115.5～+124.5.kg/hm2,明显高于玉米季;由于玉米季氮素损失严重,氮素盈余较少,甚至出现亏缺,玉米季氮素平衡状况为-54.6～+14.3.kg/hm2。     

丛枝菌根真菌调控土壤氧化亚氮排放的机制

氮素是陆地生态系统初级生产力的主要限制因子,自Haber-Bosch反应以来,氮肥的生产和施用极大地提高了粮食产量.然而过量施用氮肥导致氮肥利用率低,并造成了严重的环境污染,包括氮沉降、硝态氮淋洗以及N2O排放等.微生物直接参与土壤氮素循环,固氮微生物、氨氧化和反硝化微生物分别在土壤固氮、铵态氮转化和硝态氮转化过程中起...     

不同供氮水平下幼龄苹果园氮素去向初探

以2年生红富士/平邑甜茶为试材,采用田间小区和15N微区相结合,研究了不同供氮水平下幼龄苹果园氮素去向。结果表明,施用氮肥显著增加了植株生物量和吸氮量,而氮肥利用率随施氮量的增加显著降低;N75、N150和N225的氮肥利用率分别为31.28%、22.95%和19.38%。土壤残留氮量随施氮量的增加而显著增大,且残留氮素主要分布于060 cm土层,深层渗漏量很小。整个作物土壤体系氮素回收率随施肥量的增加显著降低,损失率显著增高。N75处理的氮素回收率为60.41%,显著高于N150（46.41%）和N225处理（40.88%）;且损失率最低（39.59%）,显著低于其它两个处理。氨挥发损失随施氮量的增加显著升高,N2O损失量各处理间无明显差异;氮素损失中氨挥发和N2O损失所占比例较低,较多的氮素通过反硝化和径流等途径损失。     

传统和优化施氮对春玉米产量、氨挥发及氮平衡的影响

【目的】本文通过在陕西省长武县(CW)和吉林省梨树县(LS)的春玉米田间试验,研究了传统和优化施氮对春玉米产量、土壤氨挥发及氮平衡的影响,以探讨春玉米氮肥优化的潜力及其对农田氨减排的效果。【方法】试验设对照、传统施氮(长武N 250 kg/hm2,梨树N 300 kg/hm2)及优化施氮(N 200 kg/hm2)3个处理,分别以N0、Ncon、Nopt表示。氨挥发采用德尔格氨管法(简称DTM法)进行原位测定,通过田间气象因素的校正计算氨挥发累积量。【结果】长武和梨树点不同施氮处理下春玉米的产量结果表明,除对照(长武7.9 t/hm2、梨树3.8 t/hm2)外,传统和优化施氮处理间均无显著差异(长武10.6 10.8 t/hm2,梨树9.5 9.6 t/hm2)。玉米氮肥利用率表现为优化施氮(44.3%44.5%)显著高于传统施氮(33.6%36.4%),其中长武点氮肥利用率提高了8.1个百分点,梨树点氮肥利用率增加了10.7个百分点。氨挥发田间监测结果显示,基肥翻耕入土后,伴随降雨的产生,长武和梨树点均未产生氨挥发。喇叭口追肥期表施氮肥后,长武和梨树点均产生大量氨挥发(占追施尿素氮量的16%22%),减少追肥用量N 30 kg/hm2(长武点)和N 100 kg/hm2(梨树点)能显著减少氨挥发损失N 8和15 kg/hm2。土壤-春玉米系统氮平衡估算的结果显示,与长武点氮素表观矿化N 97 kg/hm2相比,梨树点仅为N 16 kg/hm2。优化施氮比传统施氮处理显著降低表观氮素盈余N 48 88 kg/hm2。长武点各施氮处理的表观氮素盈余中,约46%的氮素残留在0—1 m的土壤中,54%损失到环境中,氨挥发占总损失的15%30%;梨树点表观氮素盈余中,35%损失到环境中,其中氨挥发占总损失的54%75%,约有65%残留在0—1m的土壤中。梨树点传统施氮处理0—1 m土层的氮素残留达N 140 kg/hm2,部分残留在土壤中的氮素也将面临淋洗、硝化和反硝化等损失的风险。与优化施氮相比传统施氮氮素表观损失增加了约N 30 40 kg/hm2,除氨挥发损失外,淋洗和硝化/反硝化等也是土壤-春玉米系统中不可忽视的氮素损失途径。【结论】我国春玉米主产区农民传统的氮肥用量偏高,增产效应不明显,氮肥损失风险加剧,尤其是氨挥发损失较大,氮肥的优化潜力高达20%33%,相当于可减少施氮N 50 100kg/hm2。     

硝化抑制剂施用对水稻产量与氨挥发的影响

通过田间微区试验,应用~(15)N标记技术研究两个施氮水平下硝化抑制剂CP施用对水稻产量、氮素利用率、氮素土壤残留和氨挥发的影响。结果表明:与推荐施氮处理(240 kg/hm~2)相比,减氮处理(180 kg/hm~2)水稻产量明显降低,但是减氮处理下施用硝化抑制剂CP后增产15.2%,差异显著,并且达到了推荐施氮处理下的产量水平。而推荐施氮处理下施用硝化抑制剂对水稻产量反而没有显著影响。施用硝化抑制剂可显著提高11.1%~25.0%的~(15)N吸收与利用效率,同时~(15)N平衡计算结果表明稻田施用硝化抑制剂减少了21.7%~28.1%的硝化?反硝化、径流等途径~(15)N损失,这可能是CP施用增加水稻产量的机理之一。然而,施用硝化抑制剂会增加54.7%~110.6%的氨挥发排放。因此,在水稻生产过程中施用硝化抑制剂CP时要进一步减施氮肥才有明显的增产效果,同时还需要采取一定的措施来控制氨挥发。     

脲酶/硝化抑制剂减少农田土壤氮素损失的作用特征

氮肥过量施用加剧了农田土壤氮素损失,如增加NH_3挥发、N_2O排放及硝酸盐淋洗等,这将降低空气和水体质量并对全球气候产生负面影响。脲酶抑制剂和硝化抑制剂可延缓土壤氮素转化,降低土壤活性氮对环境的负面效应,因此在农业生产中被广泛应用,如N-丁基硫代磷酰三胺(NBPT)、3,4-二甲基吡唑磷酸盐(DMPP)和双氰胺(DCD)。本文重点阐述了脲酶抑制剂NBPT和硝化抑制剂DMPP、DCD在农田土壤中的作用机制及其对环境和农学效应的影响,并揭示影响其施用有效性的主要因素。大多数研究结果表明,NBPT与尿素或有机肥配合施用后能够减少土壤NH_3挥发、N_2O排放和NO_3~-淋洗,并提高作物产量、品质及氮肥利用率;与NBPT类似,两种典型硝化抑制剂DCD和DMPP均能降低土壤N_2O排放和NO_3~-淋洗并提高作物产量,但某些环境条件下也会增加土壤NH_3挥发损失。不同农田生态系统中脲酶/硝化抑制剂的作用效果与抑制剂种类、降雨或灌溉量、土壤p H值和黏粒含量等因素有关。在未来的生产实践中,应根据抑制剂在不同土壤环境下的作用特征来更加科学合理地施用抑制剂。     

露地蔬菜的氮肥效应与氮素去向

采用田间小区和微区试验相结合,研究了小青菜、大白菜和番茄3种露地蔬菜的氮肥利用率及其氮素去向的差异。结果表明,在小青菜和大白菜上施氮增产显著(p<0.05),而在番茄上未表现出增产效应;施氮使3种蔬菜的吸氮量显著增加。用差值法和15N-示踪法测得的3种蔬菜氮肥利用率相当,且利用率随氮肥用量增加而降低。小青菜生长期间土壤氮素总损失低于10%,而大白菜和番茄生长期间土壤氮素损失分别为41.9%~48.6%和34.2%~46.0%。试验中未发现小青菜生长期间有氮素淋溶,大白菜和番茄分别有9.2%~10.9%和10%~10.2%的标记尿素被淋溶到40cm以下土层。     

包膜尿素对芹菜产量、品质及氮素平衡的影响

通过盆栽试验研究了包膜尿素(自制)和尿素等肥料在两种质地灰潮土上对芹菜产量、品质、氮素吸收和氮平衡的影响。结果表明,施用包膜尿素较尿素使当季芹菜增产11.5％-15.2％,氮素吸收增加5.9％-9.5％,氨挥发损失N减少14.2％-14.9％,淋失和反硝化氮损失减少25.5％-28.3％,氮素利用率提高19.2％-27.1％,土壤持留氮增加32.0％-37.3％。芹菜植株硝态氮含量降低44.2％-58.9％,维生素C含量显著提高,品质改善;后茬作物生菜增产14.4％-35.2％。     

The interdependence of ammonia volatilization and denitrification as nitrogen loss processes in flooded rice fields in the Philippines

Summary The relative importance of ammonia volatilization and denitrification as loss processes following the application of urea to flooded rice by the traditional method was assessed at four sites with different characteristics in the Philippines. The effect of reducing ammonia loss on denitrification and total N loss was also studied. The total N loss was determined by a ¹⁵N-balance method and ammonia volatilization was assessed by a bulk aerodynamic method following the application of urea to small plots (4.8×5.2 m). As run-off was prevented and leaching losses were negligible, the denitrification loss was assessed as the difference between total N loss and ammonia loss. When urea was broadcast into the floodwater at transplanting, the ammonia loss varied from 10% to 56% of the applied N. Loss was smallest at Aguilar where wind speeds were low and the greatest at Mabitac where floodwater pH values and temperatures were high and the winds were strong. The ammonia loss was reduced at all sites by incorporating the urea into the soil by harrowing. However, the reduction achieved varied markedly between sites, with the largest reduction (from 56% to 7% loss of the applied N) being observed at Mabitac. The total N lost from the basal application into the floodwater ranged from 59% to 71% of the applied N. Incorporating the urea by harrowing reduced the total N loss at two sites, increased the total N loss at the third site, and had no effect at the fourth site. The denitrification losses ranged widely (from 3% to 50% of the applied N) when urea was broadcast into the floodwater at the four sites. The denitrification loss was low when the ammonia loss was high (Mabitac) and high when the ammonia loss was low (Aguilar). Reducing ammonia losses by incorporating the urea into the flooded soil resulted in increased denitrification losses at three of the sites and appeared to have no effect on denitrification at the fourth site. The results show that reducing the ammonia loss by incorporating urea into the soil does not necessarily result in reduced total N loss, and suggest that the efficiency of fertilizer N will be improved only when both N-loss processes are controlled simultaneously.     

南京两种菜地土壤氨挥发的研究

在南京雨花区武警农场和栖霞区东阳科技站先后进行了秋季小青菜和秋冬季大白菜田间试验,研究菜地土壤施用氮肥后的氨挥发及其影响因素,氨挥发采用密闭室间歇密闭通气法测定。结果表明,小青菜试验地的pH为5 .4 ,施肥后土壤pH值也未高于6 .0 ,故氨挥发损失低(<0 .4 % ) ;而在pH为7.7的大白菜试验地上,控释尿素、低氮和高氮3个处理(施氮量分别为N 180、30 0和6 0 0kghm-2 )氨挥发率分别为0 .97%、12 .1%和17 1%。以上结果表明,土壤pH是影响菜地土壤氨挥发的主要因素,降低氮肥用量能明显减少氨挥发,而施用控释尿素是一种有效控制氨挥发损失的措施。大白菜不同施肥期的结果还表明,施尿素后降雨通过降低表层土壤氮的浓度而影响氨挥发,降雨离施肥期越近,雨量越大,氨挥发越小     

镉、铅、锌对红壤微生物生物量的影响

Nitrogen(N)losses from ammonium bicarbonate or urea applied to wheat and then followed immediately by irrigation were investigated.Ammonia volatilization was determined by a micrometeorological method (ammonia sampler),total N loss was estimated by the ^15N mass balance method ,and denitrification loss was measured by the diference method(calculated from the difference between the total N loss and ammonia loss) and a direct method (measuring the emission of (N2 N2O)-^15N).Total ammonia losses from ammonium bicarbonate and urea in 33 days were 8.7% and 0.9% of the applied nitrogen ,respectively.The corresponding total N losses were 21.6% and 29.5%,Apparent denitrification losses(by the difference method) were rather high,being 12.9% from ammonium bicarbonate and 28.6% from urea .However,no emission of (N2 N2O)-^15N was detected using the direct method.     

有机无机肥长期定位试验土壤小麦季氨挥发损失及其影响因素研究

氨挥发是肥料氮素损失的重要途径之一,损失率因土壤类型、气候条件、肥料用量、施肥时间和方式等不同而存在很大差异。为了筛选提高氮肥利用率的肥料运筹方式,本文利用长期定位试验平台,采用间歇密闭通气法,研究了有机无机肥长期施用条件下小麦季土壤氨挥发损失及其影响因素。结果表明,不同肥料种类和配施强烈地影响着土壤氨挥发,在150kgN·hm^-2用量下小麦季氨挥发损失量以NK和有机肥处理为最高,分别达到17．89和15．70kgN·hm^-2,占氮肥用量的10．47％-11．93％,显著高于NPK、NP和有机无机肥配施（1／20M）处理。土壤氨挥发速率与气温呈显著正相关,基肥施用后灌水可以有效地降低氨挥发损失。NPK肥料平衡施用或者有机无机肥配施可以减少氨挥发损失。     

太湖地区水稻追肥的氨挥发损失和氮素平衡

采用密闭室通气法和¹⁵N 微区试验, 对太湖地区水稻不同生育期追施氮肥的氨挥发损失、水稻对氮肥的吸收利用和土壤氮素残留情况进行了研究。结果表明, 氨挥发损失主要发生在施肥后1 周内, 峰值出现在施肥后1~2 d, 氨挥发速率变化与田面水NH₄⁺-N 浓度变化规律一致, 分蘖肥和穗肥氨挥发损失率分别为16.7%和6.3%; 水稻分蘖肥的作物氮素利用率低于穗肥, 分别为36.7%和49.6%, 主要原因是穗肥的氨挥发损失较少,并且更易于向籽粒转移; 2 次追施氮肥的表观损失率分别为52.8%和40.7%; 在土壤中残留肥料氮为10.6%, 大都集中在0~20 cm 土壤中, 耕层以下较少。本结果表明, 在水稻孕穗时期施氮肥有利于提高氮肥利用效率、减少氮肥损失, 主要体现在穗肥拥有较低的氨挥发损失率和较高的籽粒利用率。     

控/缓释肥料减少氨挥发和氮淋溶的效果研究

采用“静态吸收法”和“土柱淋溶法”室内模拟实验，分别研究了6种控／缓释肥料施入土壤中的氨挥发和氮淋溶情况。结果表明：6种控／缓释肥料处理都不同程度的降低了氨挥发量和N素淋溶量。与尿素比较，6种控／缓释肥料氨挥发量分别较普通尿素减少16．62％，23．78％，32．15％，0．11％，16．59％和37、78％，氮淋溶量分别较普通尿素减少15．84％，38．27％，68．87％，46．17％，52．51%和62．01％。试验还表明控／缓释氮肥氨挥发量与不同氮肥引起的土壤脲酶活性、pH值有密切关系。     

Gaseous Loss of Nitrogen from Fertilizers Applied to a Paddy Soil in Southeastern China

Total nitrogen(N) loss and ammonia volatilization from urea applied to flooded rice grown on a paddy soil in Zhejiang Province were measured by ^15N balance and micro-meteorological methods,respectively.Floodwater properties and ammonia loss from the circular plot were compared with those from the microplots.And the effectiveness of urease inhibitor,NBPT [N-(n-butyl) thiophosphoric triamide],was also tested Results showed that the total losses from urea broadcast and incorporated at transplanting (basal dressing) were similar with those from urea broadcast 12 days after transplanting (top-dressing)(51.5% and 48%,respectively,of applied N),and ammonia losses were low,the corresponding figures were 10.8% and 7.0% of applied N,respectively.Thus,denitrification was a much more important pathway of nitrogen loss than ammonia volatilization under the particular conditions.Addition of NBPT retarded urea hydrolysis,reduced pHs and ammoniacal nitrogen concentrations of floodwater for either the application of urea as basal or as top-dressing,but these effects were not translated into the reduction of total nitrogen loss.Floodwater pHs and ammonia loss in the microplots were apparently lower than those in the circular plot from urea applied as basal dressing;however,such differences were not found when urea was top-dressed.The frequently raining days occurred after top-dressing may be responsible for the insignificant effect of plot size on floodwater pHs and ammonia volatilization.It seems that the effects of phot size on ploodwater properties and ammonia loss mainly depend on weather conditions,in addition to the height and leaf area index of the crop.