优化施氮下稻-麦轮作体系土壤N_2O排放研究

采用了静态箱法研究优化施氮下湖北稻-麦轮作体系农田N2O排放特征。结果表明,农田N2O排放量随施氮量增加而增加。N2O排放通量峰值大约发生在施氮后的第37~d。小麦季土壤N2O排放量范围为N2O 2.43~4.84kg/hm2,肥料氮通过N2O排放的损失率为0.54%0~.74%。水稻季土壤N2O排放量为N2O 0.892~.45 kg/hm2,肥料氮通过N2O排放的损失率为0.39%0~.47%。小麦季和水稻季施氮后01~5 d N2O排放量占当季总排放量的百分比分别为62.79%6~6.72%和87.97%9~3.14%。与习惯施氮相比,基于作物阶段氮素吸收增加追肥比例和施氮次数的优化施氮能有效减少土壤N2O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。     

优化施氮下稻-麦轮作体系氮肥氨挥发损失研究

采用密闭室连续通气法研究了优化施氮下湖北稻-麦轮作体系农田氨挥发损失。结果表明,肥料氮素氨挥发损失量随施肥量增加而增加。施肥处理小麦季氨挥发损失量为N 11.37~17.05 kg/hm2,肥料氮氨挥发损失率为4.75%5~.43%,氨挥发峰值大约发生在施肥后的第35~d,肥料氨挥发过程持续71~0 d;水稻季氨挥发损失量为N32.506~2.82 kg/hm2,肥料氮氨挥发损失率为8.24%1~9.38%,氨挥发峰值大约发生在施肥后的第23~d,氨挥发过程持续57~d。水稻季和小麦季氨挥发之间差异显著,整个稻-麦轮作体系氨挥发主要发生在水稻季,约占整个轮作体系的74.08%7~8.65%。同习惯施氮相比,基于作物阶段氮素吸收增加追肥比例和施肥次数的优化施氮能有效减少肥料氮的氨挥发损失。     

适宜施氮量降低京郊小麦-玉米农田N2O排放系数增加产量

为明确京郊地区小麦-玉米轮作农田的N_2O排放特征,寻求既能减少N_2O排放又保证粮食产量的切实有效措施,以京郊地区冬小麦-夏玉米轮作农田为研究对象,运用静态箱法对8个施氮水平的农田N_2O交换通量进行了连续一年对比研究,每季作物施肥量分别为N0(0 kg/hm~2),N1(50 kg/hm~2),N2(100 kg/hm~2),N3(150 kg/hm~2),N4(200 kg/hm~2),N5(250 kg/hm~2),N6(300 kg/hm~2),和N7(400 kg/hm~2)。在N0-N7施氮量条件下冬小麦季N_2O排放量为0.08~0.52 kg/hm~2;夏玉米季0.26~3.70 kg/hm~2。整个轮作周期,小麦季各处理N_2O排放损失率为0.05%~0.13%;玉米季0.78%~1.02%。在京郊地区冬小麦-夏玉米轮作体系中夏玉米季氮肥施入农田土壤后,土壤N_2O排放通量高于小麦季。京郊农田土壤N_2O排放通量表现出明显的季节性和日变化规律。综合考虑本试验条件下施肥量、N_2O排放量和京郊地区潮土农田小麦-玉米产量,研究认为该轮作体系中每季作物的施肥量为N4(200 kg/hm~2)比较合理,可为合理施肥及估算中国农田温室气体排放量提供参考。     

不同施氮量对冬小麦田氮去向和气态损失的影响

该文研究氮肥对冬小麦田肥料氮素去向和气态损失的影响。通过布置田间微区试验,采用15N微区示踪技术和密闭室间歇通气法、密闭式静态箱法田间原位监测冬小麦氮肥的去向和气态损失。随着施氮量的增加,冬小麦产量和地上部吸氮量增加,但当施氮量高于150 kg/hm2时,产量出现降低的趋势,地上部吸氮比例也以土壤氮为主转变为肥料氮为主。4个施氮处理N75、N150、N225和N300的0-100 cm的土壤氮残留分别为32.6,26.8,34.7,40.6 kg/hm2。冬小麦田间土壤氨挥发排放总量随着施氮量的增加而增加,排放量在6.03～13.26kg/hm2之间,占施N量的5.4%～11.4%。N2O排放造成的氮素损失比例为0.08%～0.28%,苗期是冬小麦季N2O排放的主要时期。化肥氮在冬小麦当季作物吸收、土壤残留及损失量分别为37.2%～50.2%,26.7%～40.6%,17.4%～22.2%,且随着施氮量的增加而升高。在本试验条件下,150 kg/hm2是适宜的氮肥用量,产量最高,土壤氮残留最低,气态损失占肥料氮总损失的比例高于75 kg/hm2处理,但差异不显著(p0.05)。因此控制氮肥用量是提高氮肥利用率的一项关键措施。     

保护地土壤N2O排放通量特征研究

为研究保护地土壤N2O排放通量特征,于2009年8～12月,在河北辛集不施氮（N0）、当地习惯施氮（N900）及减量施氮（N675）处理下的秋冬季番茄保护地土壤上使用静态箱采集、气相色谱仪检测的方法测定了土壤N2O排放通量。得到以下研究结果:灌溉施肥后,各处理N2O平均排放通量与表层土壤硝态氮含量呈极显著正相关关系。灌溉施肥后7 d内是施氮处理土壤N2O主要排放期,其排放量占当季总排放量的55.9%~59.8%;高峰值一般出现在第3～5 d,此时的土壤含水量对硝化、反硝化作用都较适宜。8～10月份由于温度较高,N2O排放通量明显高于较冷的11～12月。8～10月份施氮是影响保护地土壤N2O排放的主导因素,减少施氮量显著降低了N2O排放量;之后温度是主导因素,此时N2O排放量受追施氮量的影响较小。经估算,保护地秋冬季番茄不同施氮处理N2O总排放量的大小顺序为:N900（N 5.304 kg/hm2）N675（N 3.616 kg/hm2） N0（N 0.563 kg/hm2）,差异显著,减量施氮比习惯施氮处理降低了31.8%的N2O排放量;N675和N900处理的N2O排放系数分别为0.45和0.53。     

有机无机肥料配合施用对设施菜田土壤N2O排放的影响

采用静态箱气相色谱法研究了有机无机肥料配合施用对设施菜田土壤N2O排放的影响。结果表明: 1）设施芹菜和番茄施基肥后57 d（灌溉后13 d）出现土壤N2O排放通量峰值,追肥后（施肥与灌溉同步）1 d出现土壤N2O排放通量峰值; 芹菜季和番茄季施用基肥后20 d内N2O排放量分别占当季总排放量的40%65%左右,是土壤N2O主要排放期。2）施用基肥后至定植灌水前各处理土壤N2O排放量逐渐降低,灌水后N2O排放通量迅速上升。各处理土壤N2O排放通量与土壤含水量之间呈显著相关,相关系数在0.43~0.72之间。3）土壤N2O排放主要发生在番茄季,番茄生育期各处理土壤N2O总排放量是芹菜生育期的3.1倍; 各处理土壤N2O排放通量与5 cm土层温度之间总体上呈显著相关,相关系数在0.40~0.58之间。4）设施菜田大幅减施化肥的有机无机肥配合施用模式可显著降低土壤N2O排放量和肥料损失率,芹菜季和番茄季土壤N2O排放量较习惯施肥处理分别降低66.3%和85.1%,肥料损失率分别降低45.2%和74.9%。5）等氮量投入时,施用秸秆较施用猪粪可有效降低土壤N2O排放,芹菜季和番茄季分别降低43.4%和74.2%。     

施氮量对砂姜黑土小麦-玉米轮作体系N_2O排放的影响

砂姜黑土是黄淮海平原重要的中低产土壤,由于其剖面含有砂姜层,易产生裂隙,影响了氮素在土壤剖面的迁移分布,可能导致砂姜黑土的N_2O排放存在一定的独特性。基于此,本研究以砂姜黑土小麦-玉米轮作体系为研究对象,设置4个处理,分别为不施肥(CK)、传统施肥(TR)、优化施肥(OPT)和再优化施肥(ZOPT),通过静态箱-气相色谱法结合常规土壤参数的监测与分析,探究砂姜黑土不同施氮条件下N_2O排放特征、累积排放量及关键驱动因素。结果显示,砂姜黑土小麦季的N_2O平均排放通量为14.2～21.6μg·m~(-2)·h~(-1),累积排放量为0.82～1.24kg(N)·hm~(-2);玉米季的N_2O平均排放通量为14.4～24.5μg·m~(-2)·h~(-1),累积排放量为0.42～0.71 kg(N)·hm~(-2);不同处理小麦季的N_2O累积排放量均高于玉米季。小麦季追肥期与基肥期的N_2O累积排放量分别为0.27～0.41 kg(N)·hm~(-2)和0.55～0.83 kg(N)·hm~(-2),玉米季分别为0.18～0.30 kg(N)·hm~(-2)和0.24～0.41 kg(N)·hm~(-2),追肥期N_2O累积排放量均高于基肥期。相关性分析结果显示, CK处理的N_2O排放量与土壤温度、含水量和硝酸盐含量均表现出明显的多元线性相关(P0.05), TR、OPT和ZOPT仅与土壤硝酸盐含量呈极显著多元线性相关(P0.01),而与土壤温度和土壤含水量未表现明显的相关性,说明施肥条件下,土壤硝酸盐含量的高低成为影响砂姜黑土农田土壤N_2O排放最关键的影响因素。除此之外,不同施氮量的N_2O累积排放量差别明显(P0.05), TR处理的N_2O排放量最高,小麦玉米季分别为1.24 kg(N)·hm~(-2)和0.71 kg(N)·hm~(-2),显著高于OPT处理[0.99 kg(N)·hm~(-2)和0.51 kg(N)·hm~(-2)]和ZOPT处理[0.82kg(N)·hm~(-2)和0.42 kg(N)·hm~(-2)]。无论小麦季还是玉米季N_2O的累积排放量均随施氮量的增加而呈指数增加趋势,相关性系数分别达0.997和0.977 (P0.05),说明砂姜黑土传统施氮N_2O存在过量排放问题。总而言之,尽管与其他土壤相比,砂姜黑土不属于N_2O高排土壤,但传统施氮量导致的N_2O排放量仍不可忽视。     

不同轮作体系不同施氮量甲烷排放比较研究

【目的】本研究通过在重庆市江津区进行单季稻转换为不同轮作体系的田间试验,测量CH4排放通量,探讨不同轮作体系CH4的排放规律。【方法】试验以玉米-小麦(MW)、 水稻-小麦(RW)、 水稻-冬水休闲(RF)三种轮作体系为主处理,每种轮作体系设不施氮对照(N0)、 优化施氮(Nopt,即小麦季N 96 kg/hm2、 玉米季或水稻季N 150 kg/hm2)、 传统施氮(Ncon,即小麦季N 180 kg/hm2、 玉米季或水稻季N 225 kg/hm2)3个副处理。温室气体采用静态箱-气相色谱法进行田间原位测量,每周1~3次,周年监测。【结果】 MW、 RW、 RF体系第一年甲烷排放量分别为CH4-C 13.5、 26.7和89.8 kg/hm2,第二年为第一年相应体系的6.2%、 85.1%和263.1%。第一年MW、 RW、 RF系统N0处理甲烷排放量分别为CH4-C 17.7、 30.5、 85.7 kg/hm2,Nopt处理分别为其对照的87.5%、 111.3%、 111.9%,Ncon处理为对照的41.5%、 51.1%、 94.8%; 第二年MW、 RW、 RF系统N0处理甲烷排放量分别为CH4-C 0.4、 26.0、 227.4 kg/hm2, Nopt为其对照的240.4%、 103.9%、 104.9%,Ncon为其对照的229.6%、 58.6%、 100.1%。MW、 RW、 RF三个轮作体系两年均为甲烷净排放,MW体系以玉米季为主, N0、 Nopt、 Ncon处理分别占总体系的87.4%、 87.2%、 76.2%; RW体系以水稻季为主, N0、 Nopt、 Ncon处理分别占总体系的91.4%、 95.7、 94.9%; RF体系中以水稻季为主,N0、 Nopt、 Ncon处理分别占总体系的84.2%、 84.9%、 84.8%。MW第一年玉米季施肥期甲烷排放累积量占该季总排放量的6%~11%,第二年占30%~45%; RW水稻季施肥期甲烷排放量占该季总排放量的37%~50%,RF水稻季施肥期甲烷排放量占该季总排放量的21%~28%,淹水休闲季约占总体系16%,也不可忽略。【结论】水稻-冬水休闲系统甲烷排放最高,水稻-小麦轮作次之,玉米-小麦轮作最低。单季稻改小麦-玉米轮作后第一年,玉米季有明显甲烷排放,第二年则未出现,两年甲烷排放总量无差异; 水稻-冬水田轮作,甲烷排放在第二年明显增加。玉米-小麦轮作、 水稻-小麦轮作和水稻-冬水休闲系统两年平均值均表现出甲烷的净排放,并以水稻或玉米季为主。大量施氮后,抑制水稻-小麦轮作和玉米-小麦轮作系统甲烷排放,对水稻-冬水休闲系统无影响。     

太湖地区不同轮作模式下的稻田氮素平衡研究

采用田间微区15N示踪,研究了太湖地区稻田不同轮作模式(紫云英-水稻轮作、休闲-水稻轮作、小麦-水稻轮作)和施氮水平(0、120 kg·hm?2、240 kg·hm?2、300 kg·hm?2)下水稻对氮肥的吸收利用效率及土壤氮素残留特征。结果表明,水稻吸收的氮素来自肥料的比例为20.9%~49.6%,休闲-水稻轮作模式下水稻产量的获得更加依赖无机氮肥的大量投入。当季水稻对肥料氮的利用率为25.0%~41.5%,肥料氮的土壤残留率为13.4%~24.6%,其中90%以上的土壤残留肥料氮集中在0~20 cm土层,在土壤剖面中的残留率随土层深度增加而迅速降低,30~40 cm土层的肥料残留量仅占氮肥施用量的0.2%~0.7%。紫云英?水稻轮作和休闲?水稻轮作模式下氮肥利用率和土壤残留率均在施氮240 kg·hm?2时达到最大值,其氮肥利用率显著高于小麦?水稻轮作55.6%和66.0%。稻季施氮240 kg·hm?2时,小麦-水稻轮作模式下的氮肥利用率、土壤残留率以及总回收率显著最低,损失率显著最大;紫云英?水稻轮作模式下的氮肥损失率最小,分别小于休闲?水稻轮作和小麦-水稻轮作13.9%、39.2%。不同轮作模式下,水稻籽粒产量随施氮量的增加而增加,稻季施氮240 kg·hm?2时,紫云英?水稻轮作下水稻籽粒产量显著高于休闲?水稻轮作和小麦?水稻轮作,小麦?水稻轮作籽粒产量虽略高于休闲?水稻轮作,但没有达到显著水平。本研究认为,选择紫云英还田配施氮肥240 kg·hm?2,既可以保证水稻氮肥利用率而获得高产,又能减少氮肥损失而带来的环境风险,是一种值得在当地大力推广的耕作制度。     

Nitrous oxide emissions in a winter wheat – summer maize double cropping system under different tillage and fertilizer management

An accurate estimation of nitrous oxide (N₂O) emission from 110 million ha of upland in China is essential for the adoption of effective mitigation strategies. In this study, the effects of different tillage practices combined with nitrogen (N) fertilizer applications on N₂O emission in soils were considered for a winter wheat (Triticum aestivum L.) – summer maize (Zea mays L.) double cropping system. Treatments included conventional tillage plus urea in split application (CTF1), conventional tillage with urea in a single application (CTF2), no‐tillage with straw retained plus reduced urea in a split application (NTSF1) and no‐tillage with manure plus reduced urea in a split application (NTMF1). The amounts of N input in each treatment were 285 and 225 kg N/ha for wheat and maize, respectively. Both NTSF1 and NTMF1 were found to reduce chemical N fertilizer rates by 33.3% (wheat) and 20% (maize), respectively, compared to CTF1 and CTF2. N₂O emissions varied between 3.2 (NTSF1) and 9.9 (CTF2) kg N₂O‐N/ha during the wheat season and between 7.6 (NTFS1) and 14.0 (NTMF1) kg N₂O‐N/ha during the maize season. The yield‐based emission factors ranged from 21.9 (NTSF1) to 60.9 (CTF2) g N₂O‐N/kg N for wheat and 92.5 (NTSF1) to 157.4 (NTMF1) g N₂O‐N/kg N for maize. No significant effect of the treatments on crop yield was found. In addition to reducing production costs involved in land preparation, NTSF1 was shown to decrease chemical fertilizer input and mitigate N₂O emissions while sustaining crop yield.     

Nitrous oxide emissions from vegetables grown in a polytunnel treated with high rates of applied nitrogen fertilizers in Southern China

Soils under intensive agricultural practices such as those for growing vegetables in plastic greenhouses are an important anthropogenic source of nitrous oxide (N₂O). Nitrous oxide emissions and measures to mitigate them through fertilizer N management have been less frequently studied than open field systems. The objectives of this study were to measure N₂O emissions from vegetables under greenhouse conditions in Southern China and to investigate the effect of reducing the amount of applied synthetic N fertilizer compared with local practice. Results indicate that the average N₂O‐N flux during the growth of four vegetables (tomato, cucumber, celery and a second tomato crop) was 117.4 ± 9 μg N/m²/h, and the annual emission rate was 8.1 ± 0.6 kg/N/ha for local farms. Temperature was important with much lower emissions during the celery‐growing season when soil and air temperatures were frequently <10 °C. Nitrous oxide emissions from the greenhouse vegetables were seven times greater than from the rice–wheat system in the same area and soils. Reducing the amount of applied synthetic N fertilizer by 40% relative to local farmers’ normal usage could reduce annual cumulative N₂O emissions by 33% without any impact on crop yields.     

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)。     

不同施氮水平对稻麦轮作农田氧化亚氮排放的影响

利用江苏常熟田间随机区组试验,以密闭箱法采集气样,气相色谱分析N2O浓度,对稻麦轮作制下不同施氮水平的土壤N2O排放进行了观测,探讨了不同施氮水平对稻麦轮作农田氧化亚氮排放的影响。结果表明,土壤N2O排放量受施氮量的影响,稻季和麦季N2O排放量都随旌氮量的增加而增加;稻季N2O排放量最大峰值出现在烤田复水期间,其排放量大小主要受基肥和分蘖肥施用量的影响,并随施氮量的增加而增大;麦季最大峰值出现在气温回暖的第二次追肥后,排放量的最大峰值也随施氮量的增加而增大;稻麦轮作土壤N2O排放以麦季的排放为主,麦季N2O累积排放量在轮作周期中占三分之二。     

施肥方式对冬小麦—夏玉米轮作土壤N_2O排放的影响

氧化亚氮(N_2O)是一种重要的农田温室气体,本研究利用紫色土长期施肥试验平台,采用静态箱/气相色谱法对紫色土旱作农田冬小麦—夏玉米轮作系统的N_2O排放进行了定位观测(2012年11月至2013年9月),研究单施氮肥(N)、常规氮磷钾肥(NPK)、猪厩肥(OM)、猪厩肥配施氮磷钾肥(OMNPK)和秸秆还田配施氮磷钾肥(ICRNPK)等施肥方式对紫色土N_2O排放特征的影响;不施肥(NF)作为对照计算排放系数,以探寻紫色土地区可操作性强、环境友好的施肥方式。结果表明,所有施肥方式的N_2O排放均呈现双峰排放,峰值出现在施肥初期;玉米季N_2O排放峰值显著高于小麦季(p0.05)。在相同的施氮水平(小麦季130 kg hm~(~(-2)),玉米季150 kg hm~(~(-2)))下,施肥方式对N_2O排放和作物产量均有显著影响(p0.05)。N、OM、NPK、OMNPK和ICRNPK处理的土壤N_2O周年累积排放量分别为1.93、1.96、1.12、1.50和0.79 kg hm~(~(-2)),排放系数分别为0.62%、0.63%、0.33%、0.47%和0.21%,全年作物产量分别为4.35、11.95、8.39、9.77、10.93 t hm~(~(-2))。施用猪厩肥显著增加N_2O排放量,而秸秆还田在保证作物产量的同时显著降低N_2O排放量,可作为紫色土地区环境友好的施肥方式。土壤无机氮(NO_3~--N和NH_4~+-N)是N_2O排放的主要限制因子。因此,在施氮水平相同时,施肥方式对紫色土活性氮含量的影响导致N_2O排放差异显著,是土壤N_2O排放差异的根本原因。土壤孔隙充水率也是影响N_2O排放的重要环境因子,并且其对N_2O排放的影响存在阈值效应。     

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.     

Effect of the number of tillages in fallow season and fertilizer type on greenhouse gas emission from a rice (Oryza sativa L.) paddy field in Ehime,southwestern Japan

Agricultural fields, including rice (Oryza sativa L.) paddy fields, constitute one of the major sources of atmospheric methane (CH₄) and nitrous oxide (N₂O). Organic matter application, such as straw and organic fertilizer, enhances CH₄ emission from paddy fields. In addition, rice straw management after harvest regulates CH₄ emissions in the growing season. The interaction of tillage times and organic fertilizer application on CH₄ and N₂O emissions is largely unknown. Therefore, we studied the effects of fallow-season tillage times and fertilizer types on CH₄ and N₂O emissions in paddy fields in Ehime, southwestern Japan. From November 2011 to October 2013, four treatments, two (autumn and spring) or one (spring) in the first year, or two (autumn and spring) or three (autumn, winter, and spring) in the second year times of tillage with chemical or organic fertilizer application, were established. Gas fluxes were measured by the closed-chamber method. Increasing the number of tillage times from one to two decreased succeeding CH₄ emission and the emission factor for CH₄ (EF_CH4) in the rice-growing season, suggesting that the substrate for CH₄ production was reduced by autumn and spring tillage in the fallow season. Higher EF_CH4 [1.8–2.0 kg carbon (C) ha^?1 d^?1] was observed when more straw was applied (6.9–7.2 Mg ha^?1) in the second year. Organic fertilizer application induced higher CH₄ emission just after the application as basal and supplemental fertilizers, especially at a lower straw application rate. This indicated that EF_CH4 in the organically managed fields should be determined individually. Organic fertilizer application with two tillage times induced N₂O efflux during the rice-growing season in the second year, but N₂O emissions were not affected by winter tillage. Although paddy fields can act as an N₂O sink because of reduced soil conditions when straw application was high, application of organic C and nitrogen as fertilizer can enhance N₂O production by the denitrification process during the growing season, especially in the ripening stage when soil anaerobic conditions became moderate. These results suggest that negative emission factors for N₂O (EF_N2O) can be applied, and EF_N2O of organic fertilizer should be considered during the estimation of N₂O emission in the paddy field.     

Mushroom residue application affects CH4 and N2O emissions from fields under rice–wheat rotation

A field experiment involving rice–wheat rotation was performed to investigate the effect of mushroom residue (MR) in comparison with chemical fertilizer (CF) and crop straw return on methane (CH₄) and nitrous oxide (N₂O) emissions in 2012–2013. Five treatments in quadruplicate were included in this study: (1) CF only, (2) CFS (straw + CF), (3) MR-1 (50% amount of N in CF was replaced with MR), (4) MR-2 (100% amount of N in CF was replaced with MR) and (5) MR-3 (150% amount of N in CF was replaced with MR). Results showed that the effects of CFS and MR-1 treatments on CH₄ and N₂O emissions did not significantly differ. By contrast, CH₄ emissions decreased as the amount of applied MR increased. Crop straw and MR stimulated CH₄ emissions (from 48.8% to 119%) in rice season in 2012. In 2013, the applied crop straw and MR decreased CH₄ emissions (from 21.3% to 37.3%). This contrasting effect might be explained by the difference in soil moisture content between the two seasons. N₂O emission in wheat season could be efficiently decreased (from 25.2% to 29.7%) by applying MR. Our results suggesting that MR could be used as a soil organic amendment under the premise of proper water management.     

不同施氮量和施氮方式对稻田氨挥发损失的影响

采用密闭室法研究苏南地区稻麦轮作体系中,不同施N量和施N方式对水稻和小麦生育期氨挥发损失的影响。结果表明,优化施肥能明显降低稻-麦轮作系统中的氨挥发损失,在整个稻麦轮作体系中,优化和习惯的氨挥发损失占N肥施用量的百分比分别为7．05％±1.37％和9．81％±0．38％。稻季与麦季的氨挥发损失差异显著。稻季氨挥发损失量与N肥施用量呈乘幂关系上升,麦季则呈正的线性关系。水稻施肥后氨挥发持续的时间短,主要发生在施肥后1周以内,麦季持续时间较长,在施肥后10天左右。稻季和麦季的基肥阶段是主要的氨挥发时期,占各自氨挥发损失N的50％左右。