Effects of Application of Controlled Release Nitrogen Fertilizer on N_2O Emission in Slope Cultivated Land with Purple Soil

In order to study effects of application of contmllE=d release fertilizer on ni- trous oxide （N2O） emission in slope cultivated land with purple soil, four treatments including the control group （CK）, urea （UR）, controlled release nitrogen fertilizer （CR）, and controlled release nitrogen fertilizer＋urea （25%CR, 75%UR） were set up, and their impacts on maize yield, surface runoff and nitrogen loss in the growth pe- riod of maize and N2O emission were studied. The results show that maize yield, surface runoff, nitrogen loss from subsurface flow, and N2O emission in the control group was far lower than that in the fertilization treatments, revealing that fertilization was the main reason for nitrogen loss and N2O emission. Among the four treat- ments, nitrogen loss from subsurface flow in the treatment CR was the highest, up to 31.7 kg/hm^2, but N2O emission was 0.35 kg/hm^2, which was 37% less than that in the treatment UR. Nitrogen loss from subsurface flow in the treatment 25% CR was the lowest, only 20.9 kg/hm^2, and N2O emission was 15% less than that in the treatment UR. Nitrogen was slowly released from controlled release nitrogen fertilizer in the growth period, and controlled release nitrogen fertilizer could reduce N2O emis- .sion from slope cultivated land due to low content of soil inorganic nitrogen, but it could increase the nitrogen loss from subsurface flow. Therefore, the combination of controlled release fertilizer and urea can not only reduce N2O emission but also de- crease nitrogen loss from subsurface flow.

N_2O emissions from agricultural soils in the North China Plain: the effect of chemical nitrogen fertilizer and organic manure

An enclosed chamber technique was used to measure N 2O emissions from intensively agricultural soils of the North China Plain during the periods of 1995—1996 and 1997—1998, to reflect distinct components of winter wheat and summer maize growing seasons. The results showed that the continuous application of fertilizer in agricultural soils increased N\-2O emissions by a factor of 24.1—28.1, the calculated annual chemical N fertilizer\|transformed N\-2O\|N emissions was 0.67%. Our results indicated that the application of organic manure also had a significant influence on soil N 2O emissions, which combined with the use of chemical N increased about 20% in a year. It was calculated that there were about 0.11% N of organic manure transformed as N 2O N. Annual mean N 2O emission from our study area of fertilized soils was estimated to be 57.1 μgN 2O/(m 2·h). A weak correlation was also found between N 2O emissions and soil available nitrogen content NH + 4.

Regulatory potential of soil available carbon,nitrogen,and functional genes on N_(2)O emissions in two upland plantation systems

Dynamic nitrification and denitrification processes are affected by changes in soil redox conditions,and they play a vital role in regulating soil N_(2)O emissions in rice-based cultivation.It is imperative to understand the influences of different upland crop planting systems on soil N_(2)O emissions.In this study,we focused on two representative rotation systems in Central China:rapeseed–rice(RR)and wheat–rice(WR).We examined the biotic and abiotic processes underlying the impacts of these upland plantings on soil N_(2)O emissions.The results revealed that during the rapeseed-cultivated seasons in the RR rotation system,the average N_(2)O emissions were 1.24±0.20 and 0.81±0.11 kg N ha^(–1)for the first and second seasons,respectively.These values were comparable to the N_(2)O emissions observed during the first and second wheat-cultivated seasons in the WR rotation system(0.98±0.25 and 0.70±0.04 kg N ha^(–1),respectively).This suggests that upland cultivation has minimal impacts on soil N_(2)O emissions in the two rotation systems.Strong positive correlations were found between N_(2)O fluxes and soil ammonium(NH_(4)^(+)),nitrate(NO_(3)^(–)),microbial biomass nitrogen(MBN),and the ratio of soil dissolved organic carbon(DOC)to NO_(3)^(–)in both RR and WR rotation systems.Moreover,the presence of the AOA-amoA and nirK genes were positively associated with soil N_(2)O fluxes in the RR and WR systems,respectively.This implies that these genes may have different potential roles in facilitating microbial N_(2)O production in various upland plantation models.By using a structural equation model,we found that soil moisture,mineral N,MBN,and the AOA-amoA gene accounted for over 50%of the effects on N_(2)O emissions in the RR rotation system.In the WR rotation system,soil moisture,mineral N,MBN,and the AOA-amoA and nirK genes had a combined impact of over 70%on N_(2)O emissions.These findings demonstrate the interactive effects of functional genes and soil factors,including soil physical characteristics,available carbon and nitrogen,and their ratio,on soil N_(2)O emissions during upland cultivation seasons under rice-upland rotations.

Refining the Factors Affecting N_(2)O Emissions from Upland Soils with and without Nitrogen Fertilizer Application at a Global Scale

Nitrous oxide(N_(2)O)is a long-lived greenhouse gas that mainly originates from agricultural soils.More and more studies have explored the sources,influencing factors and effective mitigation measures of N_(2)O in recent decades.However,the hierarchy of factors influencing N_(2)O emissions from agricultural soils at the global scale remains unclear.In this study,we carry out correlation and structural equation modeling analysis on a global N_(2)O emission dataset to explore the hierarchy of influencing factors affecting N_(2)O emissions from the nitrogen(N)and non-N fertilized upland farming systems,in terms of climatic factors,soil properties,and agricultural practices.Our results show that the average N_(2)O emission intensity in the N fertilized soils(17.83 g N ha^(-1)d^(-1))was significantly greater than that in the non-N fertilized soils(5.34 g N ha^(−1) d^(−1))(p<0.001).Climate factors and agricultural practices are the most important influencing factors on N_(2)O emission in non-N and N fertilized upland soils,respectively.For different climatic zones,without fertilizer,the primary influence factors on soil N_(2)O emissions are soil physical properties in subtropical monsoon zone,whereas climatic factors are key in the temperate zones.With fertilizer,the primary influence factors for subtropical monsoon and temperate continental zones are soil physical properties,while agricultural measures are the main factors in the temperate monsoon zone.Deploying enhanced agricultural practices,such as reduced N fertilizer rate combined with the addition of nitrification and urease inhibitors can potentially mitigate N_(2)O emissions by more than 60%in upland farming systems.

A combination of straw incorporation and polymer-coated urea offsets soil ammonia and nitrous oxide emissions in winter wheat fields

The combined effects of straw incorporation(SI)and polymer-coated urea(PCU)application on soil ammonia(NH_(3))and nitrous oxide(N_(2)O)emissions from agricultural fields have not been comprehensively evaluated in Northwest China.We conducted a two-year field experiment to assess the effects of combining SI with either uncoated urea(U)or PCU on soil NH_(3)emissions,N_(2)O emissions,winter wheat yields,yield-scaled NH_(3)(/NH_(3)),and yield-scaled N_(2)O(/N_(2)O).Five treatments were investigated,no nitrogen(N)fertilizer(N_(0)),U application at 150 kg N ha-1 with and without SI(SI+U and S_(0)+U),and PCU application at 150 kg N ha^(-1) with and without SI(SI+PCU and S_(0)+PCU).The results showed that the NH_(3);emissions increased by 20.98-34.35%following Sl compared to straw removal,mainly due to increases in soil ammonium(NH_(4)^(+)-N)content and water-flled pore space(WFPS).SI resulted in higher N_(2)O emissions than under the So scenario by 13.31-49.23%due to increases in soil inorganic N(SIN)contents,WFPS,and soil microbial biomass.In contrast,the PCU application reduced the SIN contents compared to the U application,reducing the NH_(3)and N_(2)O emissions by 45.99-58.07 and 18.08-53.04%,respectively.Moreover,no significant positive effects of the SI or PCU applications on the winter wheat yield were observed.The lowest /NH_(3) and /N_(2)O values were observed under the S_(0)+PCU and SI+PCU treatments.Our results suggest that single PCU applications and their combination with straw are the optimal agricultural strategies for mitigating gaseous N emissions and maintaining optimal winter wheat yields in Northwest China.

Effects of soil moisture and temperature on CH_4 oxidation and N_2O emission of forest soil

Soil samples were taken from depth of 0-12cm in the virgin broad- leaved/Korean pine mixed forest in Changbai Mountain in April, 2000. 20 μL·L-1 and 200 μL·L-1 CH4 and N2O concentration were supplied for analysis. Laboratory study on CH4 oxidation and N2O emission in forest soil showed that fresh soil sample could oxidize atmospheric methane and product N2O. Air-dried soil sample could not oxidize atmospheric methane, but could produCt N2O. However, it could oxidize the supplied methane quickly when its concentration was higher than 20 μL·L-1. The oxidation rate of methane was increased with its initial concentration. An addition of water to dry soil caused large pulse of N2O emissions within 2 hours. There were curvilinear correlations between N2O emission and temperature (r2=0.706, p <0.05), and between N2O emission andtwater content (r2=0.2968. p <0.05). These suggested temperature and water content were important factors controlling N2O emission. The correlation between CH4 oxidization and temperature was also found while CH4 was supplied 200 μL·L-1 (r2 =0.3573, p<0.05). Temperature was an important f8Ctor controlling CH4 oxidation. However, when 20 μL·L-1 CH4 was supplied, there was no correlation among CH4 oxidization, N2O emission, temperature and water content.

Effects of cultivation on N_2O emission and seasonal quantitative variations of related microbes in a temperate grassland soil

Laboratory and in situ experiments were done to investigate the influences of cultivation on temperate semi arid grassland (for 17 years spring wheat planted once every two years without fertilization) on soil N 2O emission and quantitative variations of related soil microbes. In the laboratory (25℃ and soil moisture 18%), cultivation increased soil transformations of fertilizer nitrogen (100 μg N/g as NaNO 3, urea, or as urea with dicyandiamide 1 μg N/g). The N 2O emissions from the cultivated and uncultivated soils with or without nitrogen additions were relatively low, and mainly originated from the nitrification. The soil N 2O emission due to cultivation decreased somewhat upon no fertilization or NaNO 3 addition, but significantly upon urea addition. The role of dicyandiamide as nitrification inhibitor was only considerable in the cultivated soil, and had small influence on decreasing N 2O emission in the two soils. The influence of cultivation on soil N 2O emission was also reflected by the number variations of microbes related with soil nitrogen transformation in the two soils. Compared to the uncultivated grassland, in situ ammonifiers and denitrifiers in the cultivated grassland quantitatively averagely increased, and aerobic no symbiotic azotobacters were quantitatively similar, leading to the continued decrease of organic matter content and the decrease of N 2O emission from the cultivated grassland soil.

Effect of Replacement of Headspace Gas on N_2O and CO_2Emissions in Anaerobic Incubation of Soil

To study effect of C2H2 and change of headspace gas on N2O emission, denitrification, as well as CO2emission, slumes of an agricultural soil were anaerobically incubated for 7 da3’s at 25 ℃. Both N2O reduction and CO2 emissions were inhibited by the addition of 100 mL L-1 of C2H2. However, the inhibition to CO2 emission was alleviated by the replacement of headspace gas, and the N2O emission was enhanced by the replacement. Acetylene disappeared evidently from the soil slumes during the incubation. Consequently results obtained from the traditional C2H2 blocking technique for determination of denitrification rate, especially in a long-time incubation, should be explained with care because of its side effect existing in the incubation environments without change of headspace gas. To reduce the possible side effect on the processes other than denitrification, it is suggested that headspace gas should be replaced several times during a long-time incubation.

Simulation of temporal and spatial change of N_2O emissions in the Yangtze River Delta

A biogeochemical model(DNDC) is combined with a plant ecological model to estimate N_2O emission from rice paddy fields in the Yangtze River Delta region. The model is driven by local meteorological, soil, and physiological data and is validated for 1999 and 2000 at a site in the region, which showed that the simulated N_2O emissions agree fairly well with the observed data. This adds some confidence in the estimated N_2O emissions during 1950 and 2000 in the Hangzhou Region. A significant correlation between the N_2O emissions and the population for the Hangzhou Region is found, which is due to a combination of increased application of fertilizers and cultivated area. Such a correlation can not be established for the whole Yangtze River Delta region when the data of both urban and rural areas are included. However, when the data from the heavily urbanized areas are excluded, a significant correlation between population and N_2O emissions emerges. The results show clearly that both the temporal and the spatial N_2O emissions have significant positive relationship with population under traditional farming practice. These results have implications for suitable mitigation options towards a sustainable agriculture and environment in this region.

Modeling N_2O Emissions from Agricultural Fields in Southeast China

DNDC, a rainfall-driven and process-oriented model of soil carbon and nitrogenbiogeochemistry, is applied t0 simulate the nitrous oxide emissions from agricultural ecosystem inSoutheast China. We simulated the soil N2O emission during a whole rice-wheat rotation cycle(from Nov. 1, 1996 to Oct. 31, 1997) under three different conditions, which are A) no fertilizer, B)both chemical fertilizer and manure and, C) chemical fertiliser only. The processes ofN2O emission were discussed in detail by comparing the model outputs with the results from fieldmeasurement. The comparison shows that the model is good at simulating most of theNzO emission pulses and trends. Although the simulated N2O emission fluxes are generally lessthan the measured ones, the model outputs during the dryland period, especially during the wheatreviving and maturing stages in spring, are much better than those during the paddy field period.Some sensitive experiments were made by simulating the N2O emissions in spring, when there is asmallest gap between the simulated fluxes and the measured ones. Meanwhile, the effects of someimportant regulating factors, such as the rainfall N deposition by rainfall, temperature, tillage, nitrogen fertilizer and manure application on N2O emission during this period were analyzed. Fromthe analysis, we draw a conclusion that soil moisture and fertilization are the most important regulating factors while the N2O emission is sensitive to some other factors, such as temperature, manure, tillage and the wet deposition of atmospheric nitrate.

Ammonia Volatilization and Deriitrification Losses from an Irrigated Maize-Wheat Rotation Field in the North China Plain

Ammonia (NH3) volatilization, denitrification loss, and nitrous oxide (N2O) emission were investigated from an irrigated wheat-maize rotation field on the North China Plain, and the magnitude of gaseous N loss from denitrification and NH3 volatilization was assessed. The micrometeorological gradient diffusion method in conjunction with a Bowen Ratio system was utilized to measure actual NH3 fluxes over a large area, while the acetylene inhibition technique (intact soil cores) was employed for measurement of denitrification losses and N2O emissions. Ammonia volatilization loss was 26.62% of the applied fertilizer nitrogen (N) under maize, while 0.90% and 15.55% were lost from the wheat field at sowing and topdressing, respectively. The differences in NH3 volatilization between different measurement events may be due to differences between the fertilization methods, and to differences in climatic conditions such as soil temperature.Denitrification losses in the fertilized plots were 0.67%-2.87% and 0.31%-0.49% of the applied fertilizer N under maize and wheat after subtracting those of the controls, respectively. Nitrous oxide emissions in the fertilized plots were approximately 0.08%-0.41% and 0.26%-0.34% of the applied fertilizer N over the maize and wheat seasons after subtracting those of the controls, correspondingly. The fertilizer N losses due to NH3 volatilization were markedly higher than those through denitrification and nitrous oxide emissions. These results indicated that NH3 volatilization was an important N transformation in the crop-soil system and was likely to be the major cause of low efficiencies with N fertilizer in the study area. Denitrification was not a very important pathway of N fertilizer loss, but did result in important evolution of the greenhouse gas N2O and the effect of N2O emitted from agricultural fields on environment should not be overlooked.

Quantifying soil nitrous oxide emissions in spring freezing-thawing period over different vegetation types in Northeast China

Environmental changes significantly alter the structure,diversity and activity of soil microbial communities during spring freezing-thawing period,leading to changes in the soil microbial nitrogen cycle.Changes in N_(2)O fluxes after land use conversion from primary forest to secondary forest,Korean pine plantation and cropland in northeast China have not been quantified.Field experiments were conducted to measure soil N_(2)O fluxes in a primary forest,two secondary forests,a Korean pine plantation,and one maize field in a temperate region in northeast China from 2017-03-06 to 2017-05-28.During the experimental period,the soil was exclusively a nitrogen source for all land uses.We found that N_(2)O emissions ranged from 15.63 to 68.74μg m^(-2) h^(-1),and cumulative N_(2)O emissions ranged from 0.33 to 2.10 kg ha^(-1) during the period.Cumulative N_(2)O emissions from the maize field were significantly higher than that from primary forest,Korean pine plantation,hardwood forest,and Betula platyphylla forest by 262.1% to 536.4%.Compared with other ecosystems in similar studies,the N_(2)O emission rates of all ecosystem types in this study were low during the spring thaw period.Stepwise multiple linear regression indicated that there were significant correlations between N_(2)O emissions and environmental factors(air temperature and soil temperature,soil water content,soil p H,NH_(4)^(+)-N,NO_(3)^(-)-N,and soil organic carbon).The results showed that conversion of land use from primary forest to hardwood forest,Korean pine plantation or maize field greatly increased soil N_(2)O emissions during spring freezing-thawing period,and N_(2)O emissions from primary forest were almost the same as those from Betula platyphylla forest.

丛枝菌根真菌对褐土玉米氮素吸收和土壤N_(2)O排放的影响

探究不同氮肥水平下丛枝菌根(AM)真菌对褐土玉米土壤N_(2)O排放和氮转化功能基因的影响,为阐明AM真菌在褐土N_(2)O排放中的作用和效应提供理论依据。设置氮肥用量(NⅠ:105 mg/kg;NⅡ:210 mg/kg)、AM真菌(M0:不接种AM真菌;M1:接种根内根孢囊霉(Rhizophagus intraradices);M2:接种摩西斗管囊霉(Funneliformis mosseae);M3:接种Rhizophagus intraradices+Funneliformis mosseae等比例混合)双因素盆栽试验。测定植株地上部全氮含量、土壤铵态氮、硝态氮含量和N_(2)O排放量,采用实时荧光定量聚合酶链式反应(PCR)法分析土壤硝化功能基因(amoA-AOA和amoA-AOB)和反硝化功能基因(nirS、nirK和nosZ)的丰度。结果表明,两种施氮水平下,接种AM真菌均可显著降低土壤N_(2)O排放通量和累积排放量,不同AM真菌处理下N_(2)O累积排放量表现为:M0>M2>M1>M3。相同AM真菌处理的土壤N_(2)O排放通量和累积排放量在NⅡ施氮水平高于NⅠ施氮水平;相同AM真菌处理的玉米菌根侵染率在NⅡ施氮水平低于NⅠ施氮水平。与M0相比,NⅠ条件下M1、M2和M3处理土壤铵态氮含量分别降低24.5%、20.8%和45.3%,硝态氮含量分别降低19.7%、14.9%和30.2%,植株地上部全氮含量分别增加16.3%、35.2%和59.6%;与M0相比,NⅡ条件下M1、M2和M3处理土壤铵态氮含量分别降低20.9%、24.8%和40.0%,硝态氮含量分别降低36.3%、25.6%和45.2%,植株地上部全氮含量分别增加33.2%、43.9%和95.4%。两种施氮水平下,AM真菌可显著降低土壤硝化功能基因(amoA-AOA和amoA-AOB)丰度,增加反硝化功能基因(nirS、nirK和nosZ)丰度。AM真菌与N_(2)O排放通量呈极显著负相关。本盆栽试验条件下,接种AM真菌均可增强两种氮肥用量玉米植株氮素吸收能力,调节硝化、反硝化相关功能基因的丰度,减少土壤N_(2)O气体的排放,且两种AM真菌混合处理的N_(2)O减排效应强于单一AM真菌接种。

添加剂H_(2)对SNCR脱硝特性的影响

在管式炉上探讨了选择性非催化还原的脱硝特性,分析了有无气体添加剂H_(2)在不同氨氮比(normalized stoichiometric ratio,NSR)下的N_(2)O、NO、NH_(3)、SO_(2)的排放特性及其随温度的变化规律。分析结果表明:无添加剂的情况下,在温度870℃、NSR为2.0时,NO最大还原效率为90%;N_(2)O生成浓度和NO还原效率的变化趋势接近,NSR越大,NO还原效率越高,N_(2)O排放浓度越大;NO还原温度窗口与N_(2)O生成的温度窗口基本上吻合。氨逃逸量在低于750℃时,明显增大,在高于850℃时,趋于0;SO_(2)浓度随温度的升高呈现与氨逃逸相反的变化趋势;随着H_(2)添加量的增大,NO还原温度窗口显著拓宽,且向低温移动,添加后最大NO还原效率超过90%,对应温度为820℃左右;N_(2)O浓度随温度呈先上升后下降的趋势,随H_(2)添加量的增加,低温区的N_(2)O浓度升高,且峰值向低温区移动,温度窗口变宽;氨逃逸量随温度升高先增大后降低,且这种趋势在低温区更明显,反应温度超过850℃,不同添加比下的氨逃逸量趋于0;添加比对SO_(2)浓度的影响在低温和高温段都不明显,SO_(2)浓度与氨逃逸量呈现相反的变化趋势。所述H_(2)添加后的污染物排放规律可为同类研究提供参考。

生物炭及其老化对农田NH_(3)挥发及N_(2)O排放的影响

生物炭具有减缓农田NH_(3)挥发和N_(2)O排放的重要潜力,但在施入环境后常常存在“老化”现象,这为其缓解全球变暖的长期有效性带来了不确定性。为了探明生物炭的长期效应,人工加速模拟了自然界中水分、温度、氧气、土壤矿物质及微生物多种老化因素,结合多元表征手段对比不同老化方式对生物炭性质的影响,利用主成分分析法建立新的生物炭性质综合指标来反映老化强度。再通过大田控制试验,采用原位通气法和静态箱-气相色谱法监测夏玉米生长周期内老化前后生物炭施用对农田NH_(3)挥发和N_(2)O排放的影响,为生物炭的可持续应用提供科学依据。结果表明,老化过程增加了原生物炭(BC)的氧含量、比表面积(SBET)、总孔容(Vt)及含氧官能团数量,降低了灰分、碱性、碳含量、平均孔径及其芳香性,各老化作用强度排序为:氧化老化生物炭(OBC)>矿化老化生物炭(KBC)>微生物老化生物炭(MBC)>干湿循环老化生物炭(WBC)>冻融循环老化生物炭(FBC)>BC。生物炭的添加减少了13.57%-29.50%的NH_(3)挥发量。与BC相比,OBC和KBC分别显著降低了14.71%和9.38%的NH_(3)挥发(P<0.05),MBC降低了3.38%的NH_(3)挥发(P>0.05)。相反,WBC和FBC分别增加了4.55%和2.72%的NH_(3)挥发(P>0.05)。同时,生物炭的添加降低了22.36%-40.43%的N_(2)O排放量。其中,BC减排效果最优,老化作用均削弱了原生物炭对N_(2)O的减排效应。与BC相比,OBC和KBC显著增加了30.34%和26.36%的N_(2)O排放量(P<0.05),MBC、FBC和WBC分别增加了19.96%、18.29%和10.92%的N_(2)O排放量(P>0.05)。综上,不同老化方式会对生物炭的理化性质造成不同改变,进而影响土壤气态氮释放。通过对比不同的老化方式,OBC影响最为显著,其次为KBC,MBC居中,WBC和FBC的影响最弱。

环戊酮对农田土壤N_(2)O排放的影响及作用机理研究

旨在明确新型植物源抑制剂环戊酮(CCO)在不同土壤条件下对氧化亚氮(N_(2)O)排放的影响及作用机理。以江西红壤和甘肃漠灌土为研究对象,试验共设3个处理:(1)空白对照(CK);(2)尿素处理(U);(3)CCO处理(U+CCO)。研究发现,施用CCO与单施尿素相比能够延长红壤和漠灌土中铵态氮在土壤中的留存时间,降低土壤硝化作用潜势;与尿素处理相比,CCO处理的N_(2)O累积排放量分别减少74.12%(红壤)和63.19%(漠灌土);荧光定量PCR结果表明,施用尿素能够增加土壤中氨氧化微生物的活性,配施CCO对氨氧化细菌的抑制效果在漠灌土中(85.81%)优于红壤(19.63%),而对氨氧化古菌无明显抑制作用;氮素输入同样能提高反硝化功能基因nirK与nirS的活性,且CCO对两种土壤中nirK与nirS基因均具有显著抑制作用;在不同土壤中,施用CCO抑制反硝化功能基因nirK与nirS活性的持续时间不同,在红壤上对反硝化功能基因nirK与nirS的抑制效果出现在培养的第7 d,而漠灌土出现在第25 d。新型植物源抑制剂CCO主要通过抑制氨氧化细菌和反硝化功能基因nirK与nirS来延缓硝化和反硝化过程,从而减少N_(2)O的排放。

稻麦复种模式下氮肥与稻秸互作对小麦产量和N_(2)O排放影响及推荐施肥研究

优化氮肥施用和秸秆还田技术为途径的农业管理措施被认为是提升农业可持续性的有效手段,然而当前关于氮肥和秸秆还田对小麦产量和N_(2)O排放影响的研究仍十分有限。为此,本研究基于2000—2022年发表的关于长江中下游流域氮肥和秸秆投入下小麦产量和N_(2)O排放变化的文献,运用随机森林建模,定量分析氮肥和秸秆还田对小麦产量和N_(2)O排放的影响,并结合情景设置进行了特定地点的小麦产量和N_(2)O排放模拟,同时评估了碳排放强度(CEE)和净生态系统经济效益(NEEB)。结果表明,建立的区域尺度小麦产量与N_(2)O排放对氮秸互作响应的随机森林模型,验证结果R^(2)分别为0.66和0.65,RMSE分别为0.70和1.11。结果表明施氮量和土壤有机质是影响小麦产量和N_(2)O排放的重要因素。综合来看,达到最大产量所需的氮肥量为208~212 kg hm^(-2),达到最小CEE所需的氮肥量为113~130 kg hm^(-2),达到最高的NEEB所需的氮肥量为202~205 kg hm^(-2),其中在6.75 t hm^(-2)的秸秆投入下施用202 kg hm^(-2)的氮肥可以获得最高的生态收益1.37万元。优化氮肥和秸秆投入具备减少作物碳排放强度并获得最大净生态环境效益的潜力。

节水灌溉下秸秆还田形式对黑土区稻田N_(2)O排放与产量的影响

为探寻不同灌溉模式下秸秆还田形式对黑土区稻田N_(2)O排放与产量的影响,于2023年进行大田试验,设置常规灌溉(F)与控制灌溉(C)两种灌溉模式,同时设置秸秆还田(S)、秸秆炭化为生物炭还田(B)、秸秆过牛腹为有机肥还田(O)3种还田形式,以及秸秆不还田(N)作为对照组,共计8个处理。分析不同灌溉模式下秸秆还田形式对稻田N_(2)O排放通量与水稻产量的影响,测定了水稻各生育期稻田土壤铵态氮含量、硝态氮含量、微生物氮含量、pH值,并分析了N_(2)O排放总量和水稻产量与土壤环境因子之间的关系。结果表明:除返青期外,与秸秆不还田处理相比,秸秆还田与有机肥还田处理土壤铵态氮含量、硝态氮含量、微生物氮含量均表现为增加。相同秸秆还田形式下,控制灌溉模式下各处理生育期内土壤平均铵态氮含量、硝态氮含量较常规灌溉模式高36.23%~60.82%、14.16%~19.61%。同时,秸秆还田与生物炭还田能提高稻田土壤pH值。相同灌溉模式下,与秸秆不还田处理相比较,秸秆还田与有机肥还田处理N_(2)O排放总量分别增加14.44%~24.09%、8.22%~14.44%,生物炭还田处理N_(2)O排放总量降低14.31%~23.90%。生物炭还田与有机肥还田各处理水稻产量提高3.28%~13.07%,其中控制灌溉模式下生物炭还田处理产量最高。综上所述,控制灌溉下生物炭还田可以实现节水、增产、减排的目的。

侧深施控释氮肥运筹方式对水稻产量、NH_(3)挥发和温室气体排放的影响

为建立机插稻高产低碳减排的控释氮肥施用技术,以迟熟中粳南粳9108、泰香粳1402为材料,选用控释期100 d、43%树脂包膜缓释氮肥与46%速效尿素为氮肥,分别设置基穗氮肥比例为100(NM1)∶、82(NM2)∶、73∶(NM3)与64(NM4)∶不同运筹方式处理,基肥采用侧深施肥方法,控释氮肥与速效尿素比例均为55,∶穗氮肥为尿素,并设置常规施肥(FFT)与不施氮肥(0N)对照处理,研究不同氮肥运筹方式对水稻产量、NH_(3)挥发和温室气体排放的影响。结果表明:与FFT处理相比,侧深施控释氮肥推迟NH_(3)挥发峰值出现,避免分蘖期NH_(3)挥发峰值产生,穗期追施尿素后的NH_(3)挥发通量和平均NH_(3)挥发通量显著降低,NH_(3)累积损失总量降低25.33%~48.76%,NH_(3)排放系数降低29.14%~60.81%,单位产量NH_(3)排放强度显著降低29.60%~56.01%。与FFT处理相比,侧深施控释氮肥分蘖期和抽穗后的CH_(4)排放通量显著降低,搁田期和穗期追施尿素后的N_(2)O排放通量显著降低,CH_(4)排放累积总量降低20.20%~55.04%,CH_(4)减排率随基穗氮肥比例变小而降低,N_(2)O排放累积总量降低25.56%~61.56%,N_(2)O减排率表现为NM1>NM3>NM2>NM4,GWP和GHGI分别降低20.96%~53.35%、25.91%~55.40%。品种间NH_(3)挥发和温室气体规律一致,减排效果均表现为NM1>NM3>NM2>NM4。综合考虑经济、生态效益,NM1处理氨挥发和温室气体减排效果最佳,且比NM3和FFT处理减少施肥次数1~2次,利于水稻绿色轻简规模化生产;NM3处理增产率最高且NH_(3)挥发和温室气体减排效果仅次NM1,实现丰产减排协同进行。综上,本文探索出一套适配迟熟中粳减排增产的控释氮肥施肥方式,重点发现“轻简+减排”型施肥方式NM1和“丰产+减排”型施肥方式NM3。

基于产量和N_(2)O排放的温室番茄灌溉模式

为了揭示设施菜地N_(2)O排放的变化规律,了解水肥气耦合对设施菜地土壤N_(2)O的影响,对不同水肥气处理进行综合评价,提出合理的减排措施。试验以番茄为供试作物,设置了灌水水平(I)、施肥水平(F)和加气水平(A)3个因素,以不加气(CK)充分灌溉条件下2个施肥水平为对照,设置I1和I2(分别为亏缺灌溉和充分灌溉,对应作物-皿系数(K_(cp))分别为0.8和1.0)2个灌水水平,F1和F2(分别为低肥和高肥,对应施氮量为180 kg·hm^(-2)和240 kg·hm^(-2))2个施肥水平,A1和A2(分别为1倍气和2倍气)2个加气水平,共10个处理。采用静态暗箱-气相色谱法对番茄全生育期N_(2)O排放进行监测分析,系统研究水肥气耦合对温室番茄土壤N_(2)O排放的影响及其影响因素。结果表明:灌水量和施肥量的增加均会增加土壤N_(2)O排放通量,I2处理的N_(2)O排放通量比I1处理平均增加14.79%(P>0.05),F2处理比F1处理平均增加34.90%(P<0.05)。加气灌溉对土壤N_(2)O排放通量有显著影响,与CK处理相比,A1和A2处理分别增加10.02%(P>0.05)和62.92%(P<0.05)。土壤N_(2)O排放通量与土壤充水孔隙度呈指数正相关关系,与NO_(3)^(-)-N含量呈指数正相关关系,当土壤温度小于等于26℃时,N_(2)O排放通量与土壤湿度呈指数正相关关系,土壤温度大于26℃时,呈线性负相关关系。综合考虑番茄产量、N_(2)O累积排放量、灌溉水分利用效率、氮肥偏生产力和单产N_(2)O累积排放量,推荐施肥量为180 kg·hm^(-2)的1倍气充分灌溉(K_(cp)=1.0)为温室番茄增产、节水、减排的较佳灌溉模式。