Effects of the nitrification inhibitor nitrapyrin and tillage practices on yield-scaled nitrous oxide emission from a maize field in Iran

Nitrification inhibitors can effectively decrease nitrification rates and nitrous oxide(N₂O)emission while increasing crop yield under certain conditions.However,there is no information available on the effects of nitrification inhibitors and tillage practices on N₂O emissions from maize cropping in Iran.To study how tillage practices and nitrapyrin(a nitrification inhibitor)affect N₂O emission,a split factorial experiment using a completely randomized block design with three replications was carried out in Northeast Iran,which has a cold semiarid climate.Two main plots were created with conventional tillage and minimum tillage levels,and two nitrogen(N)fertilizer(urea)management systems(with and without nitrapyrin application)were created as subplots.Tillage level did not have any significant effect on soil ammonium(NH₄⁺)and nitrate(NO₃^-)concentrations,cumulative amount and yield-scaled N₂O emission,and aboveground biomass of maize,whereas nitrapyrin application showed significant effect.Nitrapyrin application significantly reduced the cumulative amount of N₂O emission by 41%and 32%in conventional tillage and minimum tillage practices,respectively.A reduction in soil NO₃^-concentration by nitrapyrin was also observed.The average yield-scaled N₂O emission was 13.6 g N₂O-N kg^-1N uptake in both tillage systems without nitrapyrin application and was significantly reduced to 7.9 and 8.2 g N₂O-N kg^-1N uptake upon the application of nitrapyrin in minimum tillage and conventional tillage practices,respectively.Additionally,nitrapyrin application increased maize biomass yield by 4%and 13%in the minimum tillage and conventional tillage systems,respectively.Our results indicate that nitrapyrin has a potential role in reducing N₂O emission from agricultural systems where urea fertilizers are broadcasted,which is common in Iran due to the practice of traditional farming.     

施氮水平对杂交晚粳“浙优12”产量及氮素利用效率的影响

为探讨杂交粳稻"浙优12"最佳施氮量,采用田间试验研究了不同施氮水平对浙北平原黄松田水稻产量和氮素利用率的影响。结果表明,水稻产量、氮肥生理效率(PEN)、氮肥回收率(REN)均以施氮量210 kg/hm2处理最高,分别比无氮肥区提高了54.4%、34.1 kg/kg和58.6%;与无氮肥区相比,在施N 150 kg/hm2基础上,配施适量有机肥有助于提高氮素利用率和产量,其PEN和REN分别提高33.1 g/g和50.6%,水稻增产61.2%。本试验条件下,综合稻谷产量、生态效应和经济效益三项因素,合理的水稻施氮量为N 234.8～241.0 kg/hm2,相应的经济生态产量为9796.4～9801.9 kg/hm2。     

Transformation of nitrogen and nitrous oxide emission from grassland soils as affected by compaction

Animal trampling is one of the main factors responsible for soil compaction under grazed pastures. Soil compaction is known to change the physical properties of the soil thereby affecting the transformation of nitrogen (N) and the subsequent of release of N as nitrous oxide (N₂O). The form of N source added to these compacted soils further affects N emissions. Here we determine the interactive effects of soil compaction and form of N sources (cattle urine and ammonium, nitrate and urea fertilizers) on the loss of N through N₂O emission from grassland soil. Overall, soil compaction caused a seven-fold increase in the N₂O flux, the total N₂O fluxes for the entire experimental period ranged from 2.62 to 61.74 kg N₂O-N ha⁻¹ for the compacted soil and 1.12 to 4.37 kg N₂O-N ha⁻¹ for the uncompacted soil. Among the N sources, the highest emissions were measured with nitrate application, emissions being 10 times more than those from other N sources for compacted soil, suggesting that the choice of N fertilizer can go a long way in mitigating N₂O emissions in compacted grasslands.     

麦茬长秧龄条件下氮肥对机插水稻氮素利用效率及产量影响的研究

为弥补秧苗超龄对长秧龄机插稻生长产生的负效应,以杂交中稻品种冈优906为材料,设置施氮量和氮肥基、追配比两因素试验,研究了氮肥运筹对机插水稻产量及氮素利用率的影响。结果表明:长秧龄机插稻植株氮素积累动态符合logistic曲线增长规律。随施氮量增加,植株氮素积累总量增加,稻谷生产效率、氮素收获指数、氮素农学效率和氮素生理利用率均减小,氮素当季利用率呈先增后减的趋势。同一施氮水平下提高穗肥比例,氮素运转效率、收获指数、农学效率、生理利用率和氮素当季利用率增加,稻谷生产效率降低。长秧龄机插稻产量随施氮量的增加而增加,施氮量对有效穗和每穗实粒数有显著影响,成穗率、每穗实粒数、充实率、充实度随后期施氮比例的增加而增加,施氮量为225 kg/hm2,基:蘖:穗肥比为4:3:3的氮肥运筹方式下长秧龄机插稻产量最高。     

菜地氮肥用量与N2O排放的关系及硝化抑制剂效果

通过连续种植四季蔬菜近一年的大田试验,探究高施氮水平和低氮肥利用率的蔬菜生产系统中,N2O排放量与氮肥施用量之间的定量关系及其机理,并研究硝化抑制剂减少菜地N2O排放的效果.结果表明,在氮肥施用水平为N 0～1 733 kg hm-2a-1间,无论氮肥中是否添加硝化抑制剂,N2O总排放量与氮肥施用量均呈指数函数关系,即氮肥施用量高时,N2O排放率也高.在各氮肥水平处理下,硝化抑制剂均能降低N2O排放,抑制率为8.75％ ～ 25.28％,且这种减排效果随着施氮量增加而增加.在氮肥施用量为N 300或400 kg hm-2季-1时,施用硝化抑制剂减少N2O排放所带来的效益略高于其成本,因此,即使不考虑氮肥利用率的提高等因素,施用硝化抑制剂仍是一种有利的选择.     

前期不同水分状况对土壤氧化亚氮排放的影响

田间采集的新鲜土壤样品分别在室温下风干(土样D)和淹水(土样S)保存110d后,将二者的含水量分别调至20%、40%、60%、80%、100%持水量(WHC,Water Holding Capacity),在25℃下培育138h,设置不通和通入10%(v/v)乙炔的处理。结果显示,在20%～80%WHC下培育时,土样S的氧化亚氮(N2O)排放量为土样D的2.48倍～6.36倍(p<0.01),而在100%WHC水分含量下培育时,土样S的N2O排放量仅为土样D的19%(p<0.01),通入乙炔不但未使土样D的N2O排放量增加,反而显著减少。通入乙炔的处理,培养结束后硝态氮的含量增加。随培育水分含量的升高,土样S和土样D的二氧化碳排放量增大。供试土样可能存在异养硝化作用。前期水分的差异显著影响土壤N2O排放量,故在田间测定土壤N2O排放量时,要考虑土壤前期水分的差异。     

Seasonal variations of nitrous oxide emission in relation to nitrogen fertilization and energy crop types in sandy soil

Nitrous oxide (N₂O) is a greenhouse gas and agricultural soils are major sources of atmospheric N₂O. Its emissions from soils make up the largest part in the global N₂O budget. Research was carried out at the experimental fields of the Leibniz-Institute of Agricultural Engineering Potsdam-Bornim (ATB). Different types (mineral and wood ash) and levels (0, 75 and 150 kg N ha⁻¹) of fertilization were applied to annual (rape, rye, triticale and hemp) and perennial (poplar and willow) plants every year. N₂O flux measurements were performed 4 times a week by means of gas flux chambers and an automated gas chromatograph between 2003 and 2005. Soil samples were also taken close to the corresponding measuring rings. Soil nitrate and ammonium were measured in soil extracts.N₂O emissions had a peak after N fertilization in spring, after plant harvest in summer and during the freezing–thawing periods in winter. Both fertilization and plant types significantly altered N₂O emission. The maximum N₂O emission rate detected was 1081 μg N₂O m⁻² h⁻¹ in 2004. The mean annual N₂O emissions from the annual plants were more than twofold greater than those of perennial plants (4.3 kg ha⁻¹ vs. 1.9 kg ha⁻¹). During January, N₂O fluxes considerably increased in all treatments due to freezing–thawing cycles. Fertilization together with annual cropping doubled the N₂O emissions compared to perennial crops indicating that N use efficiency was greater for perennial plants. Fertilizer-derived N₂O fluxes constituted about 32% (willow) to 67% (rape/rye) of total soil N₂O flux. Concurrent measurements of soil water content, NO₃ and NH₄ support the conclusion that nitrification is main source of N₂O loss from the study soils. The mean soil NO₃-N values of soils during the study for fertilized soils were 1.6 and 0.9 mg NO₃-N kg⁻¹ for 150 and 75 kg N ha⁻¹ fertilization, respectively. This value reduced to 0.5 mg NO₃-N kg⁻¹ for non-fertilized soils.     

Denitrification and nitrous oxide to nitrous oxide plus dinitrogen ratios in the soil profile under three tillage systems

There is a growing interest in the adoption of conservation tillage systems [no-till (NT) and reduced tillage (RT)] as alternatives to conventional tillage (CT) systems. A 2-year study was conducted to investigate possible environmental consequences of three tillage systems on a 2.4-ha field located at Macdonald Research Farm, McGill University, Montreal. The soil was a sandy loam (0.5 m depth) underlain by a clay layer. Treatments consisted of a factorial combination of CT, RT, and NT with the presence or absence of crop residue. Soil NO₃^--N concentrations tended to be lower in RT than NT and CT tillage treatments. Denitrification and N₂O emissions were similar among tillage systems. Contrary to the popular assumption that denitrification is limited to the uppermost soil layer (0–0.15 m), large rates of N₂O production were measured in the subsurface (0.15–0.45 m) soil, suggesting that a significant portion of produced N₂O may be missed if only soil surface gas flux measurements are made. The N₂O mole fraction (N₂O:N₂O+N₂) was higher in the drier season of 1999 under CT than in 2000, with the ratio occasionally exceeding 1.0 in some soil layers. Dissolved organic C concentrations remained high in all soil depths sampled, but were not affected by tillage system.     

改进施氮运筹对水稻产量和氮素吸收利用的影响

【目的】秸秆还田不仅可改良土壤和增加土壤有机质,还能提高作物产量和品质。但秸秆还田后,土壤有机酸积累和微生物固氮,抑制水稻前期生长。在长江流域稻麦两熟地区,当地农户往往通过增加施氮量来解决秸秆还田的负效应,造成肥料浪费和氮污染。因此,探索研究秸秆还田条件下水稻优化的氮肥运筹措施,阐明水稻产量形成和氮素吸收与利用对氮素响应特征,对于提高水稻产量和氮素利用效率具有重要意义。【方法】2012 2013年,以超级粳稻武运粳24号和宁粳3号为材料,在江苏省兴化市进行大田试验,在秸秆全量还田条件下,设置常规施氮300 kg/hm2(N1)、增加施氮量345 kg/hm2(N2)和常规施氮运筹(CFP,基肥∶分蘖肥∶穗肥=3∶3∶4)、改进施氮运筹(MFP,基肥∶分蘖肥∶穗肥=4∶3∶3),以无氮处理为对照,研究施氮量和氮肥运筹措施对水稻产量及其产量构成、干物质积累、氮素积累、氮素吸收速率和氮肥利用效率的影响。【结果】随着氮肥水平提高,水稻穗数显著增加,每穗粒数、结实率和千粒重下降,最终增产不显著。与常规施氮运筹比较,改进氮肥运筹显著增加穗数,显著提高群体颖花量并增产,在N1水平下,改进施氮运筹增产幅度为5.18%7.10%,高于N2水平的2.70%4.29%。随着施氮量增加,水稻分蘖中期、拔节期、移栽期至分蘖中期、分蘖中期至拔节期干物质积累量、氮素积累量显著增加,最终成熟期干物质积累量和氮素积累量有所增加,但差异不显著,而氮肥农学利用率、氮肥吸收利用率和氮偏肥生产力显著下降。与常规氮运筹处理相比,改进氮运筹显著增加水稻移栽期至分蘖中期干物质积累量、氮素积累量和氮素吸收速率,增加成熟期干物质积累量和氮素积累量,提高氮肥农学利用率、氮肥吸收利用率、氮肥生理利用率和氮偏肥生产力,在N1水平下成熟期干物质积累量和氮素积累量分别增加6.52%和5.55%,氮肥农学利用率、氮肥吸收利用率、氮肥生理利用率和氮偏肥生产力分别提高13.36%、8.55%、4.44%和5.29%,差异均达显著水平。【结论】秸秆全量还田条件下,增加氮肥用量水稻增产不显著,且氮肥利用效率低。不增加氮肥用量,通过适当提高基肥比例(基肥∶分蘖肥∶穗肥=4∶3∶3),可实现提高水稻产量、干物质积累量、氮素积累量和氮肥利用效率。     

Nitrous oxide emission as affected by changes in soil water content and nitrogen fertilization

Nitrous oxide emission was measured in laboratory incubations of an alluvial soil (58% clay, pH 7.4). The soil was amended with 40 mg N kg⁻¹ as NaNO₃ or NH₄Cl, or with NaCl as a control. Each fertilization treatment was adjusted to three different water contents: constant 60% WHC (water-holding capacity), constant 120% WHC, and water content alternating between 60 and 120% WHC. During an 8-day incubation period N₂O emission rates and inorganic nitrogen concentrations in soil (NH₄⁺, NO₂⁻, NO₃⁻) were determined at regular intervals. In the control and after nitrate application small N₂O emission rates occurred with only minor variations over time, and no differences between the water treatments. In contrast, with ammonium application N₂O emission rates were much higher during the first two days of incubation, with peaks in the constant 60% WHC and 120% WHC at day 1 and in the changing-water treatment at day 2, when the first wet period (120% WHC) was completed. This N₂O peak in the changing-water treatment was 4 to 9 times higher than with constant WHC and occurred when both, NH₄⁺ and NO₂⁻ concentrations declined sharply. Thus, this N₂O emission flush can be attributed to nitrifier denitrification. After the second rewetting of the NH₄⁺-amended soil no further N₂O emission peak was observed, being in accordance with small NH₄⁺ and NO₂⁻ concentrations in soil at that time. The unexpectedly small N₂O fluxes in the constant 120% WHC treatment after nitrate application were probably caused by the reduction of N₂O to N₂ under the prevailing conditions. It can be concluded that continuous wetting or flooding of a soil is an effective measure to reduce N₂O emissions immediately after the application of NH₄⁺ fertilizers.     

森林土壤氧化亚氮排放对大气氮沉降增加的响应研究进展

森林土壤N2O来源于土壤氮素的氧化还原反应,硝化、反硝化、硝化细菌反硝化以及化学反硝化是其产生的四个关键过程。当前,氮素富集条件下森林土壤N2O排放存在硝化和反硝化主导作用之争,对大气氮沉降增加的响应模式以及微生物驱动机制尚不清楚。综述了森林土壤N2O来源的稳定性同位素拆分,森林土壤总氮转化和N2O排放对增氮的响应规律,增氮对N2O产生菌群落活性和组成的影响,并指出研究的薄弱环节与未来的研究重点。总体而言,森林土壤N2O排放对大气氮沉降增加的响应呈现非线性,包括初期无明显响应、中期缓慢增加和后期急剧增加三个阶段,取决于森林生态系统"氮饱和"程度。施氮会引起森林土壤有效氮由贫氮向富氮的转变,相应地改变了土壤硝化细菌和反硝化细菌群落丰度与组成,进而影响土壤N2O排放。由于森林土壤N2O排放监测、土壤总氮转化和N2O产生菌群落动态研究多为独立进行的,难以阐明微生物功能群与N2O排放之间的耦合关系。未来研究应该有机结合15N-18O标记和分子生物学技术,准确量化森林土壤N2O的来源,揭示森林土壤N2O排放对增氮的非线性响应机理。     

Nitrous oxide emission from different fertilizers and its mitigation by nitrification inhibitors in irrigated rice

 N₂O emissions from a transplanted irrigated rice grown on a Typic Ustochrept soil at New Delhi, India, were studied to evaluate the effect of N fertilizers, i.e. urea and (NH₄)₂SO₄, alone and in combination with the nitrification inhibitors dicyandiamide (DCD) and thiosulphate. The addition of urea and (NH₄)₂SO₄ increased N₂O emissions considerably when compared to no fertilizer N application (control). N₂O measurement in the field was done by a closed-chamber method for a period of 98 days. The application of urea with DCD and thiosulphate reduced N₂O fluxes considerably. The highest total N₂O-N emission (235 g N₂O-N ha^–1) was from the (NH₄)₂SO₄ treatment, which was significantly higher than the total N₂O-N emission from the urea treatment (160 g N₂O-N ha^–1). DCD reduced N₂O-N emissions by 11% and 26% when applied with urea and(NH₄)₂SO₄, respectively, whereas thiosulphate in combination with urea reduced N₂O-N emissions by 9%. Total N₂O-N emissions were found to range from 0.08% to 0.14% of applied N. N₂O emissions were low during submergence and increased substantially during drainage of standing water. Received: 20 October 1999     

秸秆还田下氮肥管理对低中产田水稻产量和氮素吸收利用影响的研究

探究氮肥运筹管理对湖北中低产田水稻产量及氮素利用率的影响,为中低产田水稻生产提供合理的施肥技术措施。本研究在秸秆还田和总氮（180 kg/hm2）控制的条件下,以水稻两优培九为材料,研究不同基、 蘖、 穗氮肥配比对中低产田水稻产量及其构成因子、不同时期叶片SPAD值、 氮含量、 地上部氮素累积量及其氮利用效率的影响。结果表明, 在2011年和2012年两年大田试验的4个基、 蘖、 穗氮肥配比处理中,各试验点水稻产量均以40-30-30的处理最高, 其中在田块A与田块C中比80-0-20处理增产15.9%和8.6%,在田块B与田块D中比60-20-20处理增产6.7%和5.5%。同时40-30-30处理的氮素收获指数（NHI）和氮肥偏生产力（PFPN）也最高,优化基、 蘖、 穗肥比可以提高氮素收获指数（NHI）和氮肥偏生产力（PFPN）。综上研究结果,各中低产田中不同基、 蘖、 穗氮肥配比处理的水稻产量依次为40-30-3050-20-3060-20-2080-0-20,结合产量构成因子、SPAD值、氮肥利用率等因素综合考虑,40-30-30是湖北中低产水稻田氮肥配比的合理运筹模式。     

不同氮肥管理措施对华北地区夏玉米田增产减排的效果分析

减少因氮肥施用而产生的N_2O对于全球N_2O的减排具有重要作用。本研究利用静态暗箱-气相色谱法,对农民习惯施肥(FP)、氮肥条施(ND)、缓控释氮肥(CRF)和一次性分层施肥(LD)4个氮肥管理措施下的华北地区夏玉米农田生态系统N_2O排放进行了观测,并分析不同处理下的N_2O减排效果和减排成本。结果表明,玉米季农田土壤N_2O排放峰值主要出现在施肥并灌溉后,峰值持续时间一般为3~5 d。与FP相比,ND、CRF和LD可以显著降低土壤N_2O的排放峰值,N_2O排放总量减少12.6%~18.9%,三者的减排效果依次为LDCRFND。ND、CRF和LD均有N_2O减排和玉米增产的作用,但由于劳动力成本的提高,仅CRF和LD处理略有增收。与FP相比,三者的单位产量N排放强度和单位净收益N排放强度均有所降低。本试验条件下,每减排1 kg CO_2-eq,CRF可减少成本0.97元,而ND和LD的减排成本分别增加4.83和3.23元。如果生产中使用施肥机械,一次性分层施肥的减排成本可节省2元。综合来看,若无配套施肥机械,施用缓控释肥可被选为夏玉米保产减排且效益最优的氮肥管理措施;反之,也可选用一次性分层施肥。     

秸秆全量还田与氮肥用量对水稻产量、 氮肥利用率及氮素损失的影响

【目的】在我国水稻生产中探讨秸秆全量还田与氮肥配施的理论与技术,阐明秸秆还田对水稻产量、 氮素利用率及氮素损失的影响,对于提高水稻产量和氮素利用效率、 减少氮污染具有重要意义。【方法】2009~2011年,以水稻南粳46为材料,在江苏常熟农业生态实验站进行原状土柱模拟试验。试验采用裂区设计,主区为秸秆全量还田(S)和无秸秆还田(S0); 副区为氮肥用量(N),设置N 120、 180、 240和300 kg/hm2 4个氮水平,以不施氮肥(N0)为对照。分析了水稻基肥期、 分蘖期、 穗肥期的氨挥发量和土壤80 cm处渗漏水全氮含量,土壤0—15 cm全氮含量,水稻产量,以及水稻籽粒和秸秆氮含量,计算水稻生育期氮肥的氨挥发损失率、 淋溶损失率、 土壤残留率以及水稻的氮肥利用效率。【结果】水稻产量随氮肥适宜用量增加而增加,与单施氮肥相比,秸秆还田下水稻平均增产6.3%,其中N 240 kg/hm2 处理产量最高; 水稻的氮肥利用率随施氮量的增加呈下降趋势,秸秆还田能够提高水稻的氮肥利用率,氮肥农学效率和氮肥表观利用率较单施氮肥分别提高1.4~3.4 kg/kg和1.8%~4.2%; 水稻田氨挥发损失量、 氮肥淋溶损失量和土壤残留氮量均随施氮量的增加而增加,在N 240 kg/hm2水平下,秸秆还田氨挥发损失量增加18.2%、 土壤残留氮量增加10.1 kg/hm2,减少氮素淋溶损失量30.9%,氮肥总损失率降低6.0%。【结论】在秸秆全量还田下,配施适量的氮肥,可以提高水稻对氮肥的利用率,增加产量,同时减少氮肥损失。本试验中,以麦秸全量还田配施N 240 kg/hm2为最优组合。     

Nitrous oxide emission from wetland rice soil as affected by the application of controlled-availability fertilizers and mid-season aeration

 N₂O emission from a wetland rice soil as affected by the application of three controlled-availability fertilizers (CAFs) and urea was investigated through a pot experiment. N₂O fluxes from the N fertilized paddy soil averaged 44.8–69.3 μg N m^–2 h^–1 during the rice growing season, accounting for 0.28–0.51% of the applied N. The emission primarily occurred during the mid-season aeration (MSA) and the subsequent re-flooding period. Fluxes were highly correlated with the NO₃ ^– and N₂O concentrations in the soil water. As there were relatively large amounts of NH₄ ⁺-N present in the soil of the CAF treatments at the beginning of MSA, leading to large amounts of NO₃ ^–-N during the MSA and the subsequent re-flooding period, the tested CAFs were not effective in reducing N₂O emission from this paddy soil. The potential of applied CAFs to reduce N₂O emissions from paddy soil is discussed. Received: 25 May 1999     

Effects of split nitrogen fertilization on post-anthesis photoassimilates,nitrogen use efficiency and grain yield in malting barley

Abstract

Split nitrogen applications are widely adopted to improve grain yield and enhance nitrogen use effective in crops. In a two-year field experiment at two eco-sites, five fractions of topdressed nitrogen of 0%, 20%, 30%, 40% and 50% were implemented. Responses of radiation interception and leaf photosynthesis after anthesis, dry matter accumulation and assimilates remobilization, nitrogen use efficiency and grain yield to fraction of topdressed nitrogen treatments were investigated in malting barley. Net photosynthetic rate of the penultimate leaf, leaf area index and light extinction coefficient increased with increasing fraction topdressed nitrogen from 0% to 30%, and then decreased from 30% to 50%. The putative gross maximum canopy photosynthesis was the highest for fraction of topdressed nitrogen of 30%, which was concomitant with the highest amount of post-anthesis accumulated assimilates. The remobilization of pre-anthesis stored assimilates from vegetative organs into grains was hardly significantly affected by fractions of topdressed nitrogen. Grain yield was the highest for fraction of topdressed nitrogen of 30%, which coincided with the highest plant nitrogen uptake and physiological and agronomic nitrogen use efficiencies. The enhanced nitrogen use efficiency was corresponding to the improved photosynthetic nitrogen-use efficiency in the leaves at fraction of topdressed nitrogen of 30%. In conclusion, appropriate fraction of topdressed nitrogen application on malting barley improved assimilation rate and nitrogen use efficiency resulting in higher grain yields and proper grain protein content in malting barley.     

不同生态稻作区氮肥增产效应及其利用率

在4个典型生态粳稻区,以广适性的5个品种为材料,研究氮肥对不同稻区产量影响,并分析氮肥利用率及其不同稻区施氮效果的差异。结果表明:氮肥施用显著提高不同稻区产量,施氮增产率及其贡献率大小顺序为温暖粳稻区寒冷粳稻区籼粳交错区冷凉粳稻区,寒冷粳稻区产量提高主要是有效穗数和千粒重的增加,而其它3个稻区产量的提高主要是有效穗数和每穗粒数的增加所致。生产等量的稻谷氮肥需要量的大小顺序为寒冷粳稻区冷凉粳稻区籼粳交错区温暖粳稻区。不同稻区对氮肥的利用效率存在差异,氮肥农学利用率大小顺序为温暖粳稻区籼粳交错区冷凉粳稻区寒冷粳稻区,氮肥吸收利用率大小顺序为籼粳交错区温暖粳稻区冷凉粳稻区寒冷粳稻区,4个稻作区的土壤氮素贡献率在61.10%~66.09%之间,说明各稻作区吸收的氮肥主要来自土壤,通过培肥地力,维持较高的地力水平对稻谷的超高产、高效具有重要意义。     

Effect of soil water status and mulching on N<Subscript>2</Subscript>O and CH<Subscript>4</Subscript> emission from lowland rice field in China

Cultivation of rice in unsaturated soils covered with mulch is receiving more attention in China because of increasingly serious water shortage; however, greenhouse gas emission from this cultivation system is still poorly understood. A field experiment was conducted in 2001 to compare nitrous oxide (N₂O) and methane (CH₄) emission from rice cultivated in unsaturated soil covered with plastic or straw mulch and the traditional waterlogged production system. Trace gas fluxes from the soil were measured weekly throughout the entire growth period using a closed chamber method. Nitrous oxide emissions from unsaturated rice fields were large and varied considerably during the rice season. They were significantly affected by N fertilizer application rate. In contrast, N₂O emission from the waterlogged system was very low with a maximum of 0.28 mg N₂O m^–2 h^–1. However, CH₄ emission from the waterlogged system was significantly higher than from the unsaturated system, with a maximum emission rate of 5.01 mg CH₄ m^–2 h^–1. Our results suggested that unsaturated rice cultivation with straw mulch reduce greenhouse gas emissions.     

控释肥对水稻产量和氮肥利用效率的影响

氮肥施用量大,氮素利用效率低一直是困扰我国水稻生产的突出问题,如何提高氮肥利用效率,减少因施用氮肥而引起的环境污染问题,是目前肥料研究中共同关心的课题。通过田间试验研究了美国Scotts控释肥、自制控释肥(AgroBB)、未包膜复合肥(Com)和混合肥(NPK)在等氮、磷、钾养分下对水稻产量和氮肥利用效率的影响。结果表明,(1)美国控释肥、自制控释肥与未包膜的复合肥比较,早稻增产8.57%～12.45%,晚稻增产9.64%～11.49%,差异达极显著或显著水平,而AgroBB与Scotts间的差异不显著。NPK与Com比较,晚稻增产7.20%,早稻仅增产2.47%。(2)早稻各处理的氮肥农学效率明显高于晚稻。Scotts、AgroBB和NPK的氮肥农学效率分别比Com明显地提高了26.93%～29.82%、18.52%～25.06%和5.35%～18.69%,其中两种控释肥之间、AgroBB与NPK间差异未达显著水平。(3)Scotts、AgroBB一次施用,NPK分次施用的氮肥回收效率分别比Com一次施用明显地提高了25.72%～28.82%、3.75%～23.70%和8.46%～27.73%。本试验条件下,控释肥处理的氮肥回收效率虽然与分次施用混合肥处理无显著性差异,但是其农学效率和生理效率明显大于混合肥处理。