不同氮源及秸秆添加对菜地土壤N_2O排放影响

在饱和田间持水量WFPS(water-filled pore space)为75%、温度为25℃的条件下,用室内培养研究设施菜地土壤在不同氮肥种类(硝酸钙CN,碳酸氢铵AB,硫酸铵AS,尿素U,对照CK)和有无秸秆添加情况下N2O的排放特征。培养17天的结果表明,各种肥料类型中,对照和硝态氮肥处理最先出现N2O排放高峰,铵态氮肥处理出现较晚。无论有无秸秆,碳酸氢铵(AB)处理的累积排放量都最高,分别为4.206±0.899和2.159±0.256μg g-1干土,铵态氮肥处理N2O排放量明显高于硝态氮肥。添加秸秆后各处理N2O排放明显增加,比未施秸秆增加1倍多(CN处理除外)。不同处理(CK除外)的N2O累积排放量与时间的关系都可用y=aLn(x)+b表示(P<0.001)。实验还发现,施用氮肥会导致土壤酸化,添加秸秆可改善土壤酸化现象。     

氮肥施用对西南地区紫色土冬小麦N_2O释放和反硝化作用的影响

N2O是重要的温室气体之一,由此引起的全球变暖和臭氧层破坏是当今重要的环境问题。采用遮光密闭箱和气相色谱法研究了氮肥施用对小麦地N2O释放和反硝化作用的影响。结果表明,小麦生长季节里,高氮、中氮以及不施氮处理N2O平均排放通量分别为2.71、2.42、1.97 gN.hm-.2d-1;尿素、硫酸铵、硝酸钾3种氮肥品种处理下,平均N2O排放通量分别为2.42、2.14、3.13 gN.hm-2.d-1。小麦生长季节里,高氮、中氮以及不施氮处理平均反硝化速率分别为4.91、4.50、1.67 gN.hm-.2d-1;尿素、硫酸铵、硝酸钾3种氮肥品种处理下,平均反硝化速率分别为4.50、3.68、5.29 gN.hm-.2d-1。氮肥施用明显促进了土壤-植物系统中N2O排放通量和反硝化作用,氮肥施用量水平和N2O排放通量、反硝化作用呈正相关。硝酸钾对N2O排放通量和反硝化作用贡献最大,硫酸铵最小。研究还表明,小麦地N2O释放和反硝化作用与季节有一定相关性,温度较高季节排放量及反硝化作用明显,反之则较弱。     

除草剂对不同种植年限柑橘园土壤氮转化过程及温室气体排放的影响

为探讨除草剂施用对柑橘园土壤氮转化及温室气体排放的影响,在实验室培养条件下,研究了0年(林地)、种植10年和30年的柑橘园土壤中分别添加除草剂草甘膦和丁草胺后,尿素态氮含量、硝化和反硝化作用以及温室气体排放的变化。研究结果表明,橘园土壤中尿素第1 d的水解率、氮肥硝化率、反硝化作用损失总量以及N_2O和CO_2排放量显著高于林地土壤(P0.05)。与10年橘园土壤相比,30年橘园土壤显著增加了尿素的水解速率、氮肥硝化率和CO_2排放量(P0.05),但二者的反硝化损失量没有显著差异。施用草甘膦和丁草胺都显著促进了林地土壤的尿素水解(P0.05),第1 d尿素态氮含量分别降低11.20%和12.43%;但对3种土壤氮肥的硝化率均没有明显影响。施用丁草胺显著降低了林地土壤的CO_2排放量(P0.05),对两种橘园土壤的CO_2排放没有明显影响,但明显增加了两种橘园土壤的N_2O排放总量(P0.05),分别比不施除草剂增加56.27%和85.41%;施用草甘膦对3种土壤的N_2O和CO_2排放均没有明显影响。可见,草甘膦和丁草胺的施用不会对柑橘园土壤的氮转化过程产生影响,但丁草胺显著增加了柑橘园土壤的N_2O排放。     

不同氮水平下黄瓜-番茄日光温室栽培土壤N_2O排放特征

为探讨日光温室黄瓜—番茄种植体系内N2O排放动态变化及其对不同氮水平的响应规律,采用密闭静态箱法,研究了常规氮量(黄瓜季1 200 kg/hm2,番茄季900 kg/hm2)、比常规氮量减25%(黄瓜季900 kg/hm2,番茄季675 kg/hm2)、减50%(黄瓜季600 kg/hm2,番茄季450 kg/hm2)以及不施氮对日光温室土壤N2O排放的影响。结果表明,温度是影响日光温室土壤N2O排放强度的重要因素,4-10月(平均气温为27.4℃)的N2O排放通量最高达818.4μg/(m2·h);而2-3月(平均气温15.1℃)以及11-12月(平均气温14.7℃)期间的N2O排放通量最高仅为464.5μg/(m2·h),比4-10月的N2O排放峰值降低了43.2%。N2O排放峰值在氮肥追施后5 d内出现,N2O排放量集中在氮肥施用后7 d内,可占整个监测期(271 d)排放量的64.7%~67.8%。施氮因增加了土壤硝态氮含量而引起N2O排放爆发式增长,0~10 cm土壤硝态氮含量与N2O排放量呈指数函数关系(P0.01)。日光温室黄瓜—番茄种植体系内的N2O排放量为0.99~9.92 kg/hm2,其中75.6%~90.0%由施氮造成。与常规氮用量相比,氮减量25%和50%处理的N2O排放量分别降低了40.4%和59.3%,总产量却增加4.9%和7.4%。综上所述,合理减少氮用量不仅可显著降低日光温室土壤N2O排放,而且不会引起产量的降低。该研究为日光温室蔬菜生产构建科学合理的施氮技术及估算中国设施农田温室气体排放量提供参考。     

黄土旱塬旱作覆膜春玉米农田N2O排放通量及影响因素研究

采用密闭式静态箱法研究黄土高原旱作玉米不同栽培模式下氧化亚氮（N2O）的排放通量及主要影响因素。结果表明,施氮是影响N2O排放的主要因素,高氮处理〉中氮＋有机肥处理〉不施氮肥处理,且排放高峰出现在施肥后的4～10d,施氮处理N2O排放通量呈季节动态变化,共出现3次排放高峰,均出现在施氮及降雨后。等量施肥条件下,覆膜处理并没有显著影响NzO排放量,N：O排放通量与硝态氮含量呈极显著正相关（P〈0．01）。在黄土高原旱作玉米农田,土壤硝化过程是导致N2O排放的主要因素,反硝化作用对N2O排放的贡献相对较低。     

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.     

缓释氮肥与尿素掺混对玉米生理特性和氮素吸收的影响

【目的】 研究不同施氮量下尿素与缓释氮肥掺混对大田玉米生理特性、氮素吸收和土壤硝态氮残留的影响，以期探索减少土壤硝态氮淋失、提高氮肥利用效率的高效施氮管理模式。 【方法】 试验在西北农林科技大学节水灌溉试验站进行，供试土壤质地为壤土，玉米品种为郑单958。设置了3种氮肥类型为尿素 (U)、缓释氮肥 (S)、尿素和缓释氮肥以 3∶7比例掺混 (SU)； 4 个施氮 (N)水平为 90 kg/hm2 (N1)、120 kg/hm2 (N2)、180 kg/hm2 (N3)、240 kg/hm2 (N4)，以不施氮肥 (N0) 为对照，共13个处理。在生育期内对玉米的产量和生理指标进行观测，并测定玉米主要生育期植株养分和土壤硝态氮含量。 【结果】 尿素掺混缓释氮肥 (SU) 处理的玉米生长后期叶绿素总量最大值分别比尿素 (U) 处理和缓释氮肥 (S) 处理最大值提高7.7%和1.3%。各生育期尿素掺混缓释氮肥 (SU) N3处理的净光合速率和蒸腾速率最高，分别高于其他处理6.9%～88.6%和3.4%～90.3%。尿素掺混缓释氮肥 (SU) 处理能够更好地促进玉米对氮素的吸收利用，其中尿素掺混缓释氮肥 (SU) N3处理氮素吸收量和籽粒的氮素分配量达最大，分别为156.0 kg/hm2和79.7 kg/hm2，高于其他处理8.1%～67.3%和6.2%～54.1%。尿素 (U) N3处理与缓释氮肥 (S) N2处理的氮素吸收量和籽粒的氮素分配量无显著差异；尿素掺混缓释氮肥 (SU) 在N3施氮量下，产量达到最高为 6200.4 kg/hm2，比尿素 (U) N3处理和缓释氮肥 (S) N2处理的产量分别增加了20.7%和19.8%。与单施尿素 (U) 和缓释氮肥 (S) 处理相比，尿素掺混缓释氮肥 (SU) 处理能充分利用0—40 cm土层养分，减少土壤氮素向更深土层淋失，提高氮肥利用率，降低土壤环境污染的风险。 【结论】 尿素与缓释氮肥掺混条件下，施氮量180 kg/hm2是提高试验区玉米叶绿素含量和光合作用，促进氮素吸收，减少硝态氮向土壤深层淋失的最佳施肥管理模式。      

菜地土壤施用铵态氮肥后 N2O 排放来源及其动态

氧化亚氮(N2O)是重要的农业源温室气体,菜地土壤施肥量高、施肥次数多,且肥水同期,是重要的N2O排放源。采用室内培养实验,测定在70%田间持水量条件下菜地土壤施用铵态氮肥后3周内N2O排放动态,利用不同气体抑制剂(低浓度乙炔、纯氧、纯氦、纯氧+乙炔)对N2O排放过程抑制效果各不相同的特点,经合理组合计算得出自养硝化、硝化细菌的反硝化、生物反硝化等主要过程对土壤N2O排放的相对贡献及其动态,以探索菜地土壤施用铵态氮肥后土壤N2O排放的来源及动态。结果表明,(1)在70%田间持水量条件下,菜地土壤施用铵态氮肥后2d内(48h内)的N2O排放通量最高,为314.4ng·g-1·d-1,到第4天时N2O排放通量已迅速降至前两天的1/6,且随培养时间的延长其排放通量不断降低。(2)自养硝化作用是菜地施用铵态氮肥后N2O排放的主要来源,施肥培养后2周内的贡献率在50%以上,2周后其贡献率降至40%左右。(3)硝化细菌的反硝化作用对N2O排放的贡献主要在施铵氮后2d内,其贡献率达44%,之后其贡献率一直保持在14%~27%。反硝化作用对N2O排放的贡献随着土壤中铵态氮含量的下降和硝态氮含量的升高而逐渐从开始时不到1%增至30%,但由于施肥培养2周后N2O的排放通量绝对数值很低(仅为施肥后2d内排放高峰的1/20),故其对N2O排放的贡献有限。土壤N2O排放通量及其来源与土壤中铵态氮和硝态氮含量的动态变化密切相关,施用铵态氮肥后土壤短期内呈现酸化趋势。因此,合理控制硝化作用是有效控制菜地土壤N2O排放的关键措施。     

炭输入及生化调控对设施菜田土壤N_2O排放的影响

本研究以河北永清蔬菜基地设施菜田土壤为研究对象,控制温度(25±1)℃和土壤含水量(70%WFPS),采用静态培养方法,通过监测培养期间土壤N_2O排放通量、无机氮含量及土壤中酶活性的变化情况,研究炭输入及生化调控对设施菜田N_2O排放及氮素转化的影响。结果表明,土壤添加尿素后,N_2O排放峰值达到644.11μg N·kg~(-1)·d~(-1),添加双氰胺(DCD)和石灰氮(CaCN_2)的土壤N_2O排放峰值分别为101.47μg N·kg~(-1)·d~(-1)和36.74μg N·kg~(-1)·d~(-1),对于N_2O减排效果好,且能有效抑制亚硝态氮的产生;施用控释尿素、添加黑炭或有机肥能减少N_2O排放,而添加石灰氮闷棚显著增加了N_2O排放。控释尿素、秸秆、黑炭、DCD和CaCN_2均对铵态氮向硝态氮的转化有一定抑制作用,施加石灰氮或有机肥有助于减少硝态氮向亚硝态氮的转化。相关分析表明,土壤中硝态氮和亚硝态氮含量增加,有助于反硝化过程的进行,增加了N_2O排放的风险。     

综合产量和土壤N2O排放的马铃薯施氮量分析

施氮可提高作物产量,但同时也增加温室气体N_2O的土壤排放量。研究施氮量与产量和土壤N_2O排放的关系,对保障作物产量并兼顾环境效应的农业生产实践具有重要指导意义。该研究设置N0(0)、N1(67.5 kg/hm~2)、N2(125 kg/hm~2)、N3(187.5 kg/hm~2)4个施氮水平,采用静态箱-气相色谱法对土壤N_2O排放进行田间原位测定,研究施氮量对马铃薯产量、土壤N_2O排放的影响,分析综合产量与土壤N_2O排放的合理施氮量。结果表明:施氮显著增加马铃薯产量和土壤N_2O累积排放量,较不施氮(N0)处理,N1、N2和N3处理马铃薯产量增加78.5%、93.1%和95.6%;生育期N1、N2和N3处理马铃薯土壤N_2O累积排放量分别是N0处理的2.3、4.4和6.7倍。同时,随施氮量增加,N_2O排放系数、硝态氮强度和单产N_2O排放量均显著增加。在低氮处理(N0、N1)时,土壤N_2O排放通量与土壤温度、湿度显著正相关,而在高氮水平时,土壤N_2O排放通量与土壤硝态氮含量显著正相关。施氮67.5 kg/hm~2可确保研究区马铃薯产量并有效降低土壤N_2O排放。     

Absorption and transport of Na and Cl in rice cultivars differing in their tolerance to salinity: An examination of the effects of ammonium and potassium salts

The absorption and transport of Na and Cl from 0.1 mM and 10 mM ²²Na labelled NaCl or ³⁶Cl labelled KCl were examined in 15 days old seedlings of 3 cultivars of rice differing in their tolerance to salinity. Furthermore, the effects of 10, 100 and 1000 ppm (N)₂S on their uptake were studied. It was found that in general, the salt‐tolerant cultivars BR and PNL‐1 absorbed more Na and translocated a lesser proportion of it to the shoot, compared to the salt‐sensitive IR‐8, from 0.1 mM NaCl. The presence of (N)₂S reduced the uptake of Na in all the cultivars. It was also found that the presence of 100 ppm K, KN or NNreduced Na absorption from 0.1 mM NaCl significantly in all the cultivars, and the translocation to shoot in BR‐ Chloride transport from 0.1 mM NaCl was reduced by (N)₂S in all the cultivars. The 3 cultivars differed significantly in the rates of absorption and transport of Na and Cl. The results indicate that PNL‐1 which is a cross of IR‐8 X BR, has inherited the salt tolerance trait from BR. Lower rates of Na translocation to the shoot can be used as an index of salt tolerance in rice.     

An examination of the total analysis of major elements in soil samples

Recently conventional chemical analyses were mostly replaced by instrumental analysis. Although results from both methods were examined in details after the samples had been solubilized or extracted by appropriate techniques, the solubilization method was considerably altered so as to be convenient for the following analysis. In atomic absorption spectrophotometry (AAS), for example, fusion technique was mostly inadequate because of the higher salts concentration in the obtained solution. The use of H₂SO₄ must also be avoided in acid digestion for SO₄ ^2- precipitates with Sr²⁺ or La³⁺ which must be added to eliminate interferences in the succeeding procedure. Therefore, it is essential to consider the whole scheme including sample treatments to evaluate the suitability of instrumental analysis. In this experiment, the suitability of the methods which have been employed in our laboratory was examined by analyzing 9 rock standards.     

我国酸性硫酸盐土壤中铁锰形态转化及迁移

酸性硫酸盐土壤酸性很强，有机质含量高，造成了这种土壤所特有的铁锰淋洗、转化和迁移规律。研究结果表明：在酸性硫酸盐土壤中全铁含量较低，一般在３５－５０ｇ／ｋｇ（以Ｆｅ２Ｏ３计），全锰含量也低，一般在０．２５－０．５５ｇ／ｋｇ（以ＭｎＯ计），一般滩涂中全铁大于６０ｇ／ｋｇ，全锰大于１ｇ／ｋｇ。酸性硫酸盐土壤中，铁的游离度较小，一般在３７－７０％，铁的活化度较大，一般在８－２０％，而滩涂中铁的游离度一般     

CO2, CH4 and N2O fluxes of upland black spruce (Picea mariana) forest soils after forest fires of different intensity in interior Alaska

Abstract

Forest fires can change the greenhouse gase (GHG) flux of borea forest soils. We measured carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) fluxes with different burn histories in black spruce (Picea mariana) stands in interior Alaska. The control forest (CF) burned in 1920; partially burned (PB) in 1999; and severely burned (SB1 and SB2) in 2004. The thickness of the organic layer was 22 ± 6 cm at CF, 28 ± 10 cm at PB, 12 ± 6 cm at SB1 and 4 ± 2 cm at SB2. The mean soil temperature during CO₂ flux measurement was 8.9 ± 3.1, 6.4 ± 2.1, 5.9 ± 3.4 and 5.0 ± 2.4°C at SB2, SB1, PB and CF, respectively, and differed significantly among the sites (P < 0.01). The mean CO₂ flux was highest at PB (128 ± 85 mg CO₂-C m^?2 h^?1) and lowest at SB1 (47 ± 19 mg CO₂-C m^?2 h^?1) (P < 0.01), and within each site it was positively correlated with soil temperature (P < 0.01). The CO₂ flux at SB2 was lower than that at CF when the soil temperature was high. We attributed the low CO₂ flux at SB1 and SB2 to low root respiration and organic matter decomposition rates due to the 2004 fire. The CH₄ uptake rate was highest at SB1 [–91 ± 21 μg CH₄-C m^?2 h^?1] (P < 0.01) and positively correlated with soil temperature (P < 0.01) but not soil moisture. The CH₄ uptake rate increased with increasing soil temperature because methanotroph activity increased. The N₂O flux was highest [3.6 ± 4.7 μg N₂O-N m^?2 h^?1] at PB (P < 0.01). Our findings suggest that the soil temperature and moisture are important factors of GHG dynamics in forest soils with different fire history.     

Denitrification potential in a grassland subsoil: effect of carbon substrates

We examined the potential of a subsoil to denitrify nitrate under optimal anaerobic conditions in a laboratory-based incubation when supplied with a range of C substrates of increasing recalcitrance. Both topsoil and its associated subsoil were supplied with nitrate and either glucose, starch or cellulose. Microbial respiration and the evolution of N₂O and N₂ were measured. The subsoil supported low amounts of microbial activity and responded only to the glucose treatment; with less than one-fifth of the N₂O production measured in the top soil. Overall, our findings demonstrated that the denitrification potential of this particular subsoil is relatively low and that only simple carbohydrates could be utilised readily by the resident microorganisms.     

Availability and extractability of soil manganese in a liming experiment

Abstract

The availability of soil Mn to corn in relation to extractability of soil Mn by EDTA, Mg(NO₃)₂, CH₃COONH₄, hydroquinone, H₃PO₄, and NH₄H₂PO₄ as affected by liming was evaluated under field conditions on a single soil type. EDTA, Mg(NO₃)₂ and CH₃COONH₄‐extractable Mn were related inversely to available Mn. No useful relationships were found between hydroquinone, H₃PO₄, and NH₄H₂PO₄‐extractable soil Mn and Mn uptake by sweet corn.     

Acidifying emissions in The Netherlands

The emission of acidifying compounds to air in the Netherlands, expressed as acidifying equivalents, consisted in 1992 mainly of NO_X (45%), NH₃ (35%) and SO₂ (20%). Transportation, agriculture and large combustion plants each contributed about 30% to the national total emission of acidifying compounds. The emissions from transportation activities mainly consisted of NO_X, while in agriculture NH₃ emission strongly dominated. Combustion processes in large combustion plants resulted both in SO₂ emissions (especially from refineries) and NO_X emissions (especially from public power plants). The total emission of acidifying substances decreases steadily in the Netherlands. The emission in 1992 was 24% lower than in 1985. It is expected to decrease further in future. The emission levels in 1992 and 1993 still are more than twice as high as the emission objective for the year 2000, set by Dutch environmental policy.     

Factors regulating acetylene reduction assay for measuring heterotrophic nitrogen fixation in water-logged soils

In the C₂H₂-C₂H₄ assay for measurement of heterotrophic N₂ fixation in water-logged soils, the diffusion of C₂H₂ into the soil and the recovery of C₂H₄ from it are critical factors regulating the assay result. To establish an C₂H₂-C₂H₄ assay technique suitable for waterlogged soils, the C₂H₂-reducing activities (ARA), assayed by varying the method of assay gas filling, the pC₂H₂ of the assay gas, the duration of assay incubation and of soil vibration before the gas sampling, were compared.

A maximum ARA was measured when the following set of procedures were applied to the soil sample in assay flasks: 1) a 4-fold repetition of I-min evacuation under 0.01 atmospheric pressure and the subsequent I-min filling under 1 atmospheric pressure with assay gas at pC₂H₂ of 0.1 atm, 2) an assay incubation for 3 hr, and 3) a sampling of an aliquot of the headspace gas after strongly vibrating the flask for 1 min.

The ARA measured by this technique was several times larger than those measured by the techniques hitherto applied, and corresponded to an almost 80% of the V _max of the sample. This technique was, therefore, proposed for the assay of heterotrophic N₂ fixation in waterlogged soils.

A striking depression of ARA in the soil sample prepared with agitation indicated that a microbial ecosystem established in the soil should be kept as undisturbed as possible throughout the C₂H₂-C₂H₄ assay.     

Sulfur dioxide inhibition of photosynthesis at different CO2 and O2 concentrations in relation to photorespiration

The mechanism of SO₂ inhibition of photosynthesis in intact leaves of tomato and maze was studied to evaluate SO₂ inhibition of photorespiration. Leaf tissues were fumigated with SO₂ under photorespiratory (low CO, and/or high O, concentrations) and non-photo-respiratory conditions. When tomato leaf disks were fumigated with 10 ppm SO₂ at 2, 21 and 100° o O., SO₂ inhibited photosynthesis at 2% O₂ in the same degrees as at 21% O₂. SO₂ inhibition of photosynthesis was depressed at higher CO₂ concentrations when the disks were fumigated with SO₂ at different CO₂ concentrations. High CO₂ concentrations also reduced the photosynthesis inhibition of maize leaf disks. These results suggest that SO₂ inhibits photosynthesis through other mechanisms than photorespiration inhibition and confirm the view that SO₂ competes with CO₂ for the carboxylating enzymes in photosynthesis     

土壤有机矿质复合体研究Ⅵ.胶散复合体的化学组成及其结合特征

本文研究水热条件渐变的地带性土壤中Ｇ１、Ｇ２组胶散复合体有机、无机物的化学组成及其结合特点。结果表明：Ｇ２组中铁有积累现象，游离态铁、铝氧化物含量为Ｇ２＞Ｇ１，但均随土壤类型变化。松结态腐殖质（Ｈ１）为Ｇ１＞Ｇ２，紧结态腐殖质（Ｈ３）则为Ｇ１＜Ｇ２。可提取腐殖质中，松、稳结态腐殖质之比值Ｈ１／Ｈ２和胡敏酸、富里酸之比值ＨＡ／ＦＡ，除个别土壤之外，都相关不大。Ｇ１、Ｇ２两组复合体中都含有一定数量的络