黄土地区冬小麦田土壤理化性状、磷酸酶活性与氧化亚氮的排放

通过大田试验研究了黄土地区种植作物对旱作农田土壤理化性状、磷酸酶活性以及土壤N2O排放的影响。结果表明:无论是否施氮肥,是否覆膜,种植冬小麦对黄土地区土壤N2O的排放均具有促进作用;管理措施不同,作物对土壤N2O排放通量的影响效应亦不同,麦田小区土壤N2O排放通量高于休耕小区N2O,且覆膜处理>常规处理>单施磷肥处理;在常规施氮和覆膜施氮条件下,小麦田的水分含量均低于休耕地的含水量,但其NH4 -N含量却高于休耕地。多重回归分析表明:麦田小区与休耕小区土壤N2O排放通量差值仅与土壤有机质增量呈显著负相关,能量物质的丰缺是决定土壤N2O变化的主要因素;磷酸酶活性与N2O排放通量之间呈极显著负线性相关,即在磷素相对缺乏的黄土地区,如何提高磷酸酶活性对于土壤N2O的减排有重要意义。     

三种控释肥在赤红壤中的氧化亚氮排放

采用静态箱收集和对比法,研究了无作物种植条件下包膜与否对高氮、均衡及高钾3种氮磷钾配比复合肥在华南赤红壤发育的菜园土中氧化亚氮(N2O)排放情况.结果表明:肥料氮磷钾配比不同,N2O排放量差异显著,3种类型复合肥N2O累积排放量表现为均衡型≥高氮型＞高钾型;同一类型复合肥,包膜控释能显著降低N2O排放量,包膜控释高氮、均衡及高钾型复合肥N2O排放总量分别为不包膜复合肥N2O排放量的34.4％、30.5％和89.3％;与不包膜相比,复合肥包膜能降低肥料在土壤中的N2O日排放通量,滞后和削减N2O排放高峰,减少土壤氮素损失以及由N2O排放造成的全球增温潜势.     

地表UV-B辐射增强对土壤-大豆系统N2O排放的影响

通过大田试验和室外盆栽试验,采用人工增加紫外辐射的方法模拟UV-B辐射增强,用静态箱-气相色谱法测定N_2O排放通量,研究地表UV-B辐射增强对土壤-大豆系统N_2O排放的影响.结果表明:在相同的气象条件和田间管理措施下,UV-B辐射增强没有改变土壤-大豆系统N_2O排放通量的季节性变化规律.但从植株结荚到成熟,UV-B辐射增强降低了土壤-大豆系统N_2O排放通量,进而降低了N_2O的累积排放量.收割实验发现,在分枝开花期,UV-B辐射增强对土壤N_2O排放影响明显,降低了土壤N_2O排放通量;从结荚至鼓粒期,UV-B辐射增强主要通过降低植株地上部分N_2O排放通量来降低土壤-大豆系统的N_2O排放.UV-B辐射增强显著降低了植株的生物量,并影响到植株的氮代谢和土壤NH_4~+-N与微生物氮.UV-B辐射增强可能会导致农田生态系统N_2O排放量降低.     

不同种植年限人工苜蓿地土壤N_2O排放通量

以半干旱区不同种植年限人工苜蓿地(1、3、4、5和8年)为研究对象,利用静态箱-气相色谱法研究不同种植年限人工苜蓿地土壤系统、土壤-植被系统的N2O排放通量规律,探讨影响土壤N2O排放通量的主要因素。结果表明:(1)苜蓿种植年限影响苜蓿地土壤-植被系统、土壤系统的N2O排放通量,不同种植年限苜蓿地N2O排放通量规律为:4年5年3年8年1年。不同种植年限苜蓿地土壤-植被系统、土壤系统的N2O排放通量季节趋势均呈"春夏季高、秋季低",在5月和8月中旬各出现了N2O排放峰值,表现出N2O的源效应。土壤-植被系统的N2O排放通量大于土壤系统的N2O排放通量。(2)苜蓿地土壤系统N2O排放通量与土壤有机碳、C∶N、铵态氮、全氮、硝态氮含量及0~5 cm土层的土壤温度呈显著正相关,与0~10 cm土壤含水量呈极显著二次负相关。土壤-植被系统N2O排放通量与地上生物量呈极显著正相关。因此,土壤全氮、硝态氮含量、0~10 cm土壤含水量及地上生物量是制约N2O排放通量的关键因子。     

轮作制度对水稻生长季节稻田氧化亚氮排放的影响

通过盆栽试验(3次重复),研究了3种主要轮作制度对稻田水稻生长季节N₂O排放的影响。结果表明,在水稻-小麦轮作中,水稻生长季节稻田N₂O-N的排放量为4．2kg·hm^-2,显著大于双季稻-小麦轮作中早稻的排放量2．2kg·hm^-2;但两者的季节平均排放通量无明显差异,分别为117和118μg·m^-2·h^-1。同时,两者都显著大于双季稻-小麦中的晚稻和持续淹水体系中的水稻生长季节稻田N20的平均排放通量,分别为67．0和42．1μg·m^-2·h^-1,在前作为旱作小麦的2种水稻生长季节中,大于91％的稻田N2O排放量都集中在水稻生长前半期;在前作为水稻的晚稻生长季节中,稻田N₂O排放量的91％集中在中期烤田及收获前水分落干阶段,轮作制度和前作水分状况极大地影响稻田N2O的排放。     

稻麦轮作系统冬小麦农田耕作措施对氧化亚氮排放的影响

2008—2011年,采用静态箱-气相色谱法对长江下游稻麦轮作系统冬小麦农田N2O排放进行了为期3a的田间原位观测,研究不同耕作措施(免耕、旋耕和翻耕)对冬小麦生长季N2O排放的影响。结果表明:不同耕作措施下冬小麦农田N2O排放高峰出现在施用基肥后的1个月内以及施用孕穗肥后的4月中旬至小麦成熟期,其余时间N2O排放通量均较小。年度和耕作措施对冬小麦农田N2O季节排放总量均有极显著影响(P<0.01),不同处理N2O季节排放总量表现为免耕>翻耕>旋耕,2008—2011年3年平均分别为2.50 kg/hm2、2.05 kg/hm2和1.66 kg/hm2,免耕比翻耕增加N2O排放22.0%(P<0.05),旋耕比翻耕减排19.0%(P<0.05)。冬小麦生长期内施用孕穗肥后1个月内N2O排放通量与农田土壤充水孔隙率(WFPS)及10 cm地温呈显著(P<0.05)或极显著(P<0.01)正相关,2009—2010年施用基肥后1个月内N2O排放通量与WFPS呈显著负相关(P<0.05)。结果说明旋耕是减少长江下游稻麦轮作系统冬小麦农田N2O排放的最佳耕作措施。     

黄淮海平原河北省范围内农田土壤二氧化碳和氧化亚氮排放量的估算

以黄淮海平原河北省范围内的农田土壤为研究对象,通过与田间实际观测数据进行比较发现,DNDC模型能够较好地反映农田土壤温室气体CO2和N2O的排放通量,可以用来模拟估算农田土壤CO2和N2O的排放通量.根据模型估算,2003年河北省111个县市农业土壤CO2排放量约3.758×106tC,各县市总的N2O排放量40.345×106kgN.全省释放的CO2和N2O中有40%左右来自冬小麦/夏玉米地.因此,减少该地区农业土壤CO2和N2O排放量的措施,应集中用于排放量高的县市和这些地区的冬小麦/夏玉米地,进行大范围的普遍减排可能收效甚微,并且没有必要.     

紫色土菜地生态系统土壤N2O排放及其主要影响因素

应用静态箱/气相色谱法对种菜历史超过20a的紫色土菜地进行了一年N2O排放的定位观测, 分析了菜地N2O排放特征及施氮、土壤温度、土壤湿度和蔬菜参与对N2O排放的影响. 结果表明, 紫色土菜地生态系统在不施氮和施氮（N150kg?hm-2）情况下N2O平均排放通量为50.713.3和168.437.3g?m-2?h-1, N2O排放系数为1.86%. 菜地生态系统N2O排放强度高于当地粮食作物农田,其主要原因在于菜地较高的养分水平和频繁的施肥、浇水等田间管理措施. 从菜地N2O排放总量的季节分配来看, 有64%的N2O排放量来自于土壤水热条件较好的夏秋季蔬菜生长期, 冬春季蔬菜生长期N2O排放量较少, 仅占34%. 因此, 土壤水热条件不同是造成菜地N2O排放量季节分配差异的重要原因. 氮肥对增加N2O排放的效应因蔬菜生育期内单位时间施肥强度不同而异, 蔬菜生育期越短, 施氮对增加N2O排放的效应越明显.不施氮和常规施氮菜地N2O排放通量与地下5cm处土壤温度呈显著的正相关, 但不种蔬菜的空地两者之间的关系不显著, 并且常规施氮菜地土壤温度（T）对N2O排放通量（F）的影响可用指数方程F＝11.465e0.032T（R＝0.26, p<0.01）表示. 土壤湿度对菜地N2O排放的影响存在阈值效应, 当土壤含水空隙率（WFPS）介于60%-75％时更易引发N2O高排放. 因此, 依据蔬菜生育期特点, 结合土壤水分状况调节施肥量与施肥时间可能会减少菜地N2O排放.     

黄绵土N2O排放的温度效应及其动力学特征

以室内试验为手段,以黄绵土为供试土壤,研究了不同水热条件下农田土壤中N2O的排放特征,并借助于化学反应动力学理论对N2O排放的热效应机理进行了探讨.结果表明:在适宜的温度范围内,表现为土壤N2O排放量随温度升高而增大.14.50%水分时,20～25℃温区N2O排放呈现"跃增"现象,即温度效应较强,而18.70%和22%水分时,N2O排放的"跃增区"分别出现在15～20℃温区和25～30℃温区,即水分条件影响着N2O排放的温度效应.土壤N2O累积排放量随时间t的变化均符合修正的Elovich方程y=a+blnt,并应用表观排放速率b从动力学角度验证了N2O排放"跃增"现象的存在.在一定的水分条件下,随着温度的增加,土壤N2O排放出现最大值(此时温度为T0),在T1～T0温区内,随温度升高土壤N2O排放量增加,在T0～T2温区内,随温度升高土壤N2O排放量降低,对于黄土性土壤而言,这一转折点(T0)在30℃左右.7.86%水分时干燥土壤存在吸收N2O的现象.     

土壤溶解性有机物对CO_2和N_2O排放的影响

农田土壤是温室气体的重要排放源,溶解性有机物作为土壤微生物容易利用的基质,其含量变化与温室气体的产生和排放密切相关。基于室内培养试验,对溶解性有机物影响土壤CO2、N2O的排放过程进行了分析。设置空白(CK)、单施秸秆(S)、单施氮肥(N)、秸秆和氮肥(S+N)4个不同的处理,对添加不同物质条件下土壤溶解性有机碳(DOC)、溶解性有机氮(DON)和CO2、N2O的排放动态进行了研究,对DOC和DON影响CO2、N2O的排放过程进行了探讨。结果表明:不同处理的温室气体排放通量和土壤DOC、DON含量差异显著;各处理的CO2排放通量和DOC动态随培养时间的延长呈现逐渐减小的趋势,S和S+N处理的N2O排放和DON动态呈现先增大后减小的趋势;S+N处理的CO2排放量最高,DON含量也显著高于其他处理,单施秸秆(S)处理的N2O排放量和DOC含量显著高于其它处理,单施氮肥(N)对土壤CO2的排放量和DOC含量的影响较小;土壤CO2和N2O的排放通量与土壤DOC和DON含量呈显著的相关性,相关系数(R2)达0.6以上,说明溶解性有机物的含量和动态对CO2、N2O的排放过程产生显著影响。     

影响阔叶红松林土壤CO2排放的主要因素

采用静态封闭箱式技术对长白山阔叶红松林土壤CO2 的排放通量进行 1年的观测 ,并通过多元回归分析了土壤CO2 排放速率与 5个环境因子间的关系。结果表明 ,阔叶红松林土壤CO2 排放与表层无凋落物的土壤CO2 排放速率在测定年度内具有相同的季节变化趋势。在不同的月份中 ,以 7月份最高 ,2月份最低 ;在夏季 18∶0 0为土壤日CO2 排放的最高峰 ;土壤CO2 排放速率与 5个环境因子进行多元回归的结果显示 :林地土壤CO2 排放速率与地表温度和地下 2 0cm土壤湿度呈显著正相关。根据气象资料推算 ,阔叶红松林的年凋落物和土壤CO2排放通量分别为 2 80 4 gCO2 ·m-2 ·a-1和 3911gCO2 ·m-2 ·a-1。阔叶红松林凋落物排放CO2年通量占土壤林地CO2 排放总量的 2 8%。     

Denitrification and N2O emission from urine-affected grassland soil

Denitrification and N₂O emission rates were measured following two applications of artificial urine (40 g urine-N m^–2) to a perennial rye-grass sward on sandy soil. To distinguish between N₂O emission from denitrification or nitrification, urine was also applied with a nitrification inhibitor (dicyandiamide, DCD). During a 14 day period following each application, the soil was frequently sampled, and incubated with and without acetylene to measure denitrification and N₂O emission rates, respectively.Urine application significantly increased denitrification and N₂O emission rates up to 14 days after application, with rates amounting to 0.9 and 0.6 g N m^–2 day^–1 (9 and 6 kg N ha^–1 day^–1), respectively. When DCD was added to the urine, N₂O emission rates were significantly lower from 3 to 7 days after urine application onwards. Denitrification was the main source of N₂O immediately following each urine application. 14 days after the first application, when soil water contents dropped to 15% (v/v) N₂O mainly derived from nitrification.Total denitrification losses during the 14 day periods were 7 g N m^–2, or 18% of the urine-N applied. Total N₂O emission losses were 6.5 and 3 g N m^–2, or 16% and 8% of the urine-N applied for the two periods. The minimum estimations of denitrification and N₂O emission losses from urine-affected soil were 45 to 55 kg N ha^–1 year^–1, and 20 to 50 kg N ha^–1 year^–1, respectively.     

Enhanced CH4 emission from a wetland soil exposed to Elevated CO2

Methane emissions from wetland soils are generally a positive function ofplant size and primary productivity, and may be expected to increase dueto enhanced rates of plant growth in a future atmosphere of elevatedCO₂. We performed two experiments with Orontium aquaticum, acommon emergent aquatic macrophyte in temperate and sub-tropical wetlands, todetermine if enhanced rates of photosynthesis in elevated CO₂atmospheres would increase CH₄ emissions from wetland soils.O. aquaticum was grown from seed in soil cores under ambient and elevated(ca. 2-times ambient) concentrations of CO₂ in an initialglasshouse study lasting 3 months and then a growth chamber study lasting 6months. Photosynthetic rates were 54 to 71% higher underelevated CO₂ than ambient CO₂, but plantbiomass was not significantly different at the end of the experiment. Ineach case, CH₄ emissions were higher under elevated thanambient CO₂ levels after 2 to 4 months of treatment, suggestinga close coupling between photosynthesis and methanogenesis in our plant-soilsystem. Methane emissions in the growth chamber study increased by 136%. We observed a significant decrease in transpirationrates under elevated CO₂ in the growth chamber study, andspeculate that elevated CO₂ may also stimulate CH₄ emissions by increasing the extent and duration offlooding in some wetland ecosystems. Elevated CO₂ maydramatically increase CH₄ emissions from wetlands, a sourcethat currently accounts for 40% of global emissions.     

不同种类氮肥对土壤释放N2O的影响

用培养试验模拟研究了在正常水分 ( 2 2 % )、干旱 ( 1 2 % )和高含水量 ( 32 % )条件下 ,普通碳酸氢铵 (普碳 )、尿素及新型肥料长效碳酸氢铵 (长碳 )对土壤释放N2 O的影响 ;同时考察了土壤NO-3 的形成时间和形成量 .结果表明 ,农田中施加的无机氮肥是大气中N2 O的重要来源 ,而长碳与普碳和尿素相比 ,不但可以明显延后N2 O释放高峰期出现时间 ,而且大多数情况下可以显著减少其释放量 (P <0 .0 1 ) .在 5个月的监测期内 ,与普碳和尿素相比其减少N2 O释放的比例分别为 80 .2 3和 88.41 % ( 1 2 %含水量 ) ,40 .0 0和2 7.59% ( 2 2 %含水量 ) ,无减少作用和 45.88% ( 32 %含水量 ) .本研究结果提示长碳具有作为农田生态系统N2 O减排措施的巨大潜力 ,同时暗示在农业中用长碳代替目前普遍应用的普碳 ,可以减少地下水中NO-3 引起的污染 .     

西安黄土区土壤碳释放的初步研究

1999年 9月～ 2 0 0 1年 9月的观测资料显示 ,西安黄土区土壤CO2 释放表现为白昼释放量低于夜间。土壤CO2 释放量日变化从当日清晨至次日晨 ,呈现由高变低再变高的规律。土壤CO2 释放量的变化趋势大体与温度的变化在时间上有一定的滞后性。西安黄土区土壤CO2 释放量有明显的季节变化 ,夏季日释放量最多 ,秋季次之 ,冬季最少。不同覆被条件下 ,土壤CO2 释放量有差异 ,一般说来 ,裸地有较高的释放量。实验表明 ,CO2 释放量对土质变化敏感 ,致密的土壤 ,释放量小。     

Airborne bacterial emission fluxes from manure-fertilized agricultural soil

This is the first study to quantify the dependence on wind velocity of airborne bacterial emission fluxes from soil. It demonstrates that manure bacteria get aerosolized from fertilized soil more easily than soil bacteria, and it applies bacterial genomic sequencing for the first time to trace environmental faecal contamination back to its source in the chicken barn. We report quantitative, airborne emission fluxes of bacteria during and following the fertilization of agricultural soil with manure from broiler chickens. During the fertilization process, the concentration of airborne bacteria culturable on blood agar medium increased more than 600 000-fold, and 1 m³ of air carried 2.9 × 10⁵ viable enterococci, i.e. indicators of faecal contamination which had been undetectable in background air samples. Trajectory modelling suggested that atmospheric residence times and dispersion pathways were dependent on the time of day at which fertilization was performed. Measurements in a wind tunnel indicated that airborne bacterial emission fluxes from freshly fertilized soil under local climatic conditions on average were 100-fold higher than a previous estimate of average emissions from land. Faecal bacteria collected from soil and dust up to seven weeks after fertilization could be traced to their origins in the poultry barn by genomic sequencing. Comparative analyses of 16S rRNA gene sequences from manure, soil and dust showed that manure bacteria got aerosolized preferably, likely due to their attachment to low-density manure particles. Our data show that fertilization with manure may cause substantial increases of bacterial emissions from agricultural land. After mechanical incorporation of manure into soil, however, the associated risk of airborne infection is low.     

不同种类氮肥对土壤释放N2O的影响

用培养试验模拟研究了在正常水分(22%)、干旱(12%)和高含水量(32%)条件下,普通碳酸氢铵(普碳)、尿素及新型肥料长效碳酸氢铵(长碳)对土壤释放N₂O的影响;同时考察了土壤NO₃^-的形成时间和形成量.结果表明,农田中施加的无机氮肥是大气中N₂O的重要来源,而长碳与普碳和尿素相比,不但可以明显延后N₂O释放高峰期出现时间,而且大多数情况下可以显著减少其释放量(P<0.01).在5个月的监测期内,与普碳和尿素相比其减少N₂O释放的比例分别为80.23和88.41%(12%含水量),40.00和27.59%(22%含水量),无减少作用和45.88%(32%含水量).本研究结果提示长碳具有作为农田生态系统N₂O减排措施的巨大潜力,同时暗示在农业中用长碳代替目前普遍应用的普碳,可以减少地下水中NO₃^-引起的污染.     

秸秆还田量对土壤CO2释放和土壤微生物量的影响

对玉米季、小麦季3种不同秸秆还田量的土壤生物学指标的测定结果表明,在秸秆倍量还田中,随着秸秆量的增加,CO2释放量增加,而且倍量处理的增加量显著大于全量处理;在玉米和小麦季节中,不同量秸秆还田对土壤0～10和10～20cm的土壤微生物量的影响不同,但均能增大土壤微生物量,全量和倍量处理间没有明显差异、在土壤表层及下层,微生物量的最大值均落后于土壤呼吸的最大值,且土壤微生物量达到最大值即其最活跃状态后,下降缓慢,但土壤呼吸减少较快,说明微生物活动存在明显的合成性呼吸与维持性呼吸;综合评价不同秸秆量还田的效应,应采用秸秆全量还田,既能调节土壤物理环境,促进微生物的代谢活动,利于养分的转化,又可以减少环境污染。     

N2O emission from soil following combined application of fertiliser-N and ground weed residues

Emissions of N₂O and CO₂ were measured following combined applications of ¹⁵N-labelled fertiliser (100 μg N g⁻¹; 10 atom % excess ¹⁵N) and organic olive crop weed residues (Avena sativa, Ononis viscosa, Ridolfia segetum and Olea europea; 100 μg N g⁻¹) to a silt loam soil under controlled environment conditions. The objective was to determine the effect of varying combinations of inorganic fertiliser and plant residues on these emissions and soil mineral N dynamics. Emissions were generally increased following application of residues alone, with 23 ng N₂O–N g⁻¹ soil (2 ng N₂O–N g⁻¹ soil mg⁻¹ biomass) and 389 μg CO₂–C g⁻¹ soil (39 μg CO₂–C g⁻¹ soil mg⁻¹ biomass) emitted over 28 days after addition of the Ridolfia residues in the absence of fertiliser-N. N₂O emissions from these residue-only treatments were strongly negatively correlated with residue lignin content (r = −0.91; P < 0.05), total carbon content (r = −0.90; P < 0.05) and (lignin + polyphenol)-to-N ratio (r = −0.70; P < 0.1). However, changes in the net input of these compounds through application of 25:75, 50:50 and 75:25 proportional mixtures of Avena and Ononis residues had no effect on emissions compared to their single (0:100 or 100:0) applications. Addition of fertiliser-N increased emissions (by up to 30 ng N₂O–N g⁻¹ 28 days⁻¹; 123%), particularly from the low residue-N treatments (Avena and Ridolfia) where a greater quantity of biomass was applied, resulting in emissions above that of the sum from the unfertilised residue and fertilised control treatments. In contrast, fertiliser application had no impact on emissions from the Olea treatment with the highest polyphenol (2%) and lignin (11%) contents due to strong immobilisation of soil N, and the ¹⁵N–N₂O data indicated that residue quality had no effect on the denitrification of applied fertiliser-N. Such apparent inconsistencies mean that before the potential for manipulating N input (organic + inorganic) to lower gaseous N losses can be realised, first the nature and extent of interactions between the different N sources and any interactions with other compounds released from the residues need to be better understood.     

中国农田土壤N2O排放通量分布格局研究

中国作为世界上一个重要农业大国,对全球大气中N2O浓度的影响正在引起人们的普遍关注。该研究采用针对农业土壤痕量气体排放估算建立的,基于N2O的产生、传输和消耗机理的反硝化分解（DNDC）模型,在建立了有关中国气候、农业土壤和农业生产的分县数据库基础上,估计了我国各县农业土壤N2O的排放通量,发现我国农田土壤N2O排放通量有较明显的地区差异,西北地区较低,东南地区较高。还发现无论温度升高,还是施肥量变化,对我国农田土壤N2O排放通量的影响,都存在区域差异,表现为东南地区的变化幅度较西北地区大,这可能与我国气候的干湿变化有较密切的关系。