Nitrification and Denitrification Activities and N_2O Emission of Orchard Soils Cultivated for Different Periods of Time

[Objective] The aim was to investigate the differences in nitrification and denitrification activities and the N20 emission of orchard soils cultivated for different periods of time. [Method] Incubation experiment was conducted to determine the ni- trification and denitrification activities and N20 emission of three types of orchard soil samples that had been cultivated for 5, 12 and 20 years, respectively, by using the virgin soil sample as control. [Result] After 26 d of incubation, the nitrification rates of nitrogen fertilizer in the virgin soil sample and the orchard soil samples cultivated for 5, 12 and 20 years were 6.85%, 10.26%, 13.29% and 12.90%, respectively, which were positively correlated with content of soil organic matter, ammonium nitro- gen and total nitrogen （P〈0.05）, and negatively correlated with soil carbon-nitrogen ratio and pH value （P〈0.05）. The denitrification activities of these soil samples in- creased with the increase of cultivation years. The amount of nitrogen loss by deni- trification accounted for 0.01%-3.11% of the amount of fertilizer nitrogen, and had a positive correlation with the content of soil organic matter （P〈0.05）. The N20 emis- sions of orchard soil samples were higher than that of the virgin soil samples （P〈 0.05）. [Conclusion] In South China, the nitrification activity of orchard soil is relatively low, but it has a tendency to increase as the cultivation years increases; the denitri- fication activity is relatively high, and increases significantly with the increase of culti- vation years.

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.

Comparison of Urea-Derived N_2O Emission from Soil and Soil-Plant System

A pot experiment with a sandy loam soil and spring wheat as test crop was conducted to compare the N2O emission from soil system with plant cut off and from soil-plant system with plant kept. The results showed that after urea fertilizer applied, the N2O emission from soil and soil-wheat system decreased exponentially with time, and its total amount was 0.34%~0.63% and 0.33%~0.58% of applied urea-N respectively, no significant difference being found between these two systems. The N2O emission had a very significant negative relationship (P = 0.01) with the biomass of wheat plant. A combined application of urease inhibitor hydroquinone and nitrification inhibitor dicyandiamide could reduce the N2O emission by 50%~83% and 46%~74%, respectivelyl from soil and soil-wheat system. The N2O was mainly produced and emitted from soil, and the soil biochemical regulation, i.e., applying related inhibitors into soil could effectively diminish the urea derived N2O emission.

N_2O emissions from a cultivated Andisol after application of nitrogen fertilizers with or without nitrification inhibitor under soil moisture regime

The aim of this work was to examine the emission of N 2O from soils following addition of nitrogen fertilizer with a nitrification inhibitor(+inh) or without the nitrification inhibitor(-inh) at different soil water regime. Higher soil moisture contents increased the total N 2O emissions in all treatments with total emissions being 7 times larger for the CK and >20 times larger for the fertilizer treatments at 85% WFPS(soil water filled pore space) than at 40% WFPS. The rates of N 2O emissions at 40% WFPS under all treatments were small. The maximum emission rate at 55% WFPS without the nitrification inhibitor(-inh) occurred later (day 11) than those of 70% WFPS (-inh) samples (day 8). The inhibition period was 4—22 d for 55% WFPS and 1—15 d for 70% WFPS comparing the rates of N 2O emissions treated (+inh) with (-inh). The maximum emission rates at 85% WFPS were higher than those at the other levels of soil water content for all treatments. The samples(+inh) released less N 2O than (-inh) samples at the early stage. Nevertheless, N 2O emissions from (+inh) samples lasted longer than in the (-inh) treatment. Changes in mineral N at 55%, 70% and 85% WFPS followed the same pattern. NH + 4-N concentrations decreased while NO - 3-N concentrations increased from the beginning of incubation. NH + 4-N concentrations from 40% WFPS treatment declined more slowly than those of the other three levels of soil water content. Nitrification was faster in the (-inh) samples with 100% NH + 4-N nitrified after 22 d(50% WFPS) and 15 d(70% and 85% WFPS). N 2O emissions increased with soil water content. Adding N-fertilizer increased emissions of N 2O. The application of the nitrification inhibitor significantly reduced total N 2O emissions from 30.5%(at 85%WFPS) to 43.6%(at 55% WFPS).

Effect of water stress on N_2O emission rate of 5 tree species

The N2O emission rates, photosynthesis, respiration and stomatal conductance of the dominant tree species from broadleaf/Korean pine forest in Changbai Mountain were measured by simulated water stress with the closed bag-gas chromatography. A total of five species seedlings were involved in this study, i.e.,Pinus koraiensis Sieb. et Zucc,Fraxinus mandshurica Rupr,Juglans mandshurica Maxim,Tilia amurensis Rupr, andQuercus mongolica Fisch. ex Turcz.. The results showed that the stomatal conductance, net photosynthetic rate and N2O emission of leaves were significantly reduced under the water stress. The stoma in the leaves of trees is the main pathway of N2O emission. N2O emission in the trees mainly occurred during daytime. N2O emission rates were different in various tree specie seedlings at the same water status. In the same tree species, N2O emission rates decreased as the reduction of soil water contents. At different soil water contents (MW, LW) the N2O emission rates ofPinus koraiensis decreased by 34.43% and 100.6% of those in normal water condition, respectively. In broadleaf arbor decreased by 31.93% and 86.35%, respectively. Under different water stresses N2O emission rates in five tree species such asPinus koraiensis, Fraxinus mandshurica, Juglans mandshurica, Tilia amurensis, andQuercus mongolica were 38.22, 14.44, 33.02, 16.48 and 32.33 ngN2O·g?1DW·h?1, respectively. Keywords Trees - N2O emission rate - Soil water stress - broadleaf/Korean pine forest - Changbai Mountain CLC number S718.55 Document code A Foundation item: This project was supported by the National Natural Science Foundation of China (No. 30271068), the grant of the Knowledge Innovation Program of Chinese Academy of Sciences (KZ-CX-SW-01-01B-10), and the Special Funds for Major State Basic Research Program of China (No. G1999043407)Biography: Wang Miao (1964-), male, associate professor in Institute of Applied Ecology, Chinese Academy of Science, Shenyang 110016, P. R. China.Responsible editor: Song Funan

Fertilizer nitrogen loss via N_2 emission from calcareous soil following basal urea application of winter wheat

The ratio of nitrous oxide(N2O)to N2O plus nitrogen gas(N2)emitted from soils(N2O/(N2O+N2))is regarded as a key parameter for estimating fertilizer nitrogen(N)loss via N2emission at local,regional or global scales.However,reliable measurement of soil N2emissions is still difficult in fertilized soil-crop systems.In this study,the N loss via N2emission following basal urea application(with a dose of 150 kg N ha-1)to a calcareous soil cultivated with winter wheat was quantified using the helium-based gas-flow-soil-core technique.Emissions of N2and N2O from sampled fresh soils were measured under simulated field soil temperature and oxygen conditions.Our observation performed on the first day after irrigation and rainfall events showed the highest N2and N2O emissions,which amounted to approximately 11.8 and 3.8μg N h-1kg-1dry soil,corresponding to 3304 and 1064μg N m-2h-1,respectively.The N2O/(N2O+N2)molar ratios within about 10 days following fertilization ranged from 0.07 to 0.25,which were much larger than those at the other time.During the one-month experimental period,the urea-N loss via emissions of N2,N2O,and N2+N2O was 1.6%,0.6%,and 2.2%,respectively.Our study confirms that the widely applied acetylene-inhibition method substantially underestimates fertilizer N losses via N2emissions from calcareous soils cultivated with winter wheat.

Effect of Vertical Distribution of Soil Water on N₂O Emission under Drip Irrigation

N2O emission has obvious water effect, but the current research is not deep enough. The soil wetting mode of drip irrigation technology is obviously different from that of conventional irrigation. Using the method of soil box indoor simulation, the N2O emission under different soil vertical water content was analyzed. Hydrus Software was used to simulate the soil wetting body under different drip irrigation technical parameters, the relationship between the combination of drip irrigation technical parameters and soil vertical water content was studied, and then the relationship between the N2O emission and the combination of drip irrigation technical parameters was proposed. The results showed that soil N2O emission flux increased with the increase of soil moisture, and the maximum emission flux was three times as much as the minimum emission flux. Under the condition of uniform distribution of soil moisture, soil N2O emission flux was smaller than that under non-uniform distribution of soil moisture. Hydrus software simulation results show that drip flow rate is 2.0 L/h, the irrigation period is 5 days, the irrigation quota is 12 mm, and the soil N2O emission flux is the largest. Adjusting the combination of technical parameters of drip irrigation can reduce soil N2O emission flux.

Correlations between Mineral Nitrogen Contents and Vertical Distribution of N20 Emission Potentials in Tropical Peat Soils Transformed into Oil Palm Plantations in Sarawak, Malaysia

Tropical peat swamp forest beds that have been reclaimed for agricultural use are generally an active source of nitrous oxide （N2O） efflux, however, the mechanism by which reclaimed tropical peat soils promote the emergence of N2O emitters in soil microbial communities remains unclear. The purpose of this study was to reveal the vertical distribution of N2O emission potential and its correlation with mineral nitrogen contents in reclaimed soils. Using a culture-based N2O emission assay, the N2O emission potentials of soil at various depths （0-450 cm） were investigated in two oil palm plantations in Sarawak, Malaysia, which had elapsed times of two years （E2Y） and 10 years （El 0Y） after deforestation, respectively. On the basis of the relationship between the vertical profiles of N2O emission potentials and the contents of mineralized nitrogen in the peat soils at various depths, the impact of land management on soil microbial communities was discussed. The peat soil at plantation site E2Y showed a trend of high N2O production in deep layers （200-400 cm）, whereas the older plantation site E10Y showed considerably more active N2O emission in shallow soil （10-50 cm）. N2O emission potentials among the soil microbial communities at different soil depths at the E10Y site showed positive correlations with NO3- and NH4＋ contents, whereas, soils obtained from the E2Y site had N2O emission potentials that were inversely proportional to the contents of NO3-. This contrasting vertical correlation between N2O-emitting potentials and mineralized nitrogen contents in bulk soils suggests that active N2O emission in deep soil at the E2Y site has maintained the original carbon-nitrogen （C/N） ratio of the peat soil, whereas at EIOY, such a regulatory system has been lost due to advanced soil degradation, leading to dynamic changes in the nitrogen cycle in shallow soil.

N_2O emissions from forest and grassland soils in northern China

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Major factors controlling nitrous oxide emission and methane uptake from forest soil

Soil samples were taken from depth of 0-12 cm in virgin broad-leaved Korean pine mixed forest in Changbai Moun-tain in July 2000. The effects of temperature, soil water content, pH, NH4+ and NO3- on N2O emission and CH4 uptake of a for-est soil were studied in laboratory by the method of orthogonal design. It was observed under laboratory conditions in this study that there were significant correlations between N2O emission rate, CH4 oxidation rate, soil pH and temperature. Nevertheless, N2O emission rate also showed a significant positive correlation with CH4 oxidation rate. The results suggested that pH and temperature were important factors controlling N2O emission and CH4 oxidation under this experiment conditions.

追氮方式对夏玉米土壤N_2O和NH_3排放的影响

【目的】研究氮肥与硝化抑制剂撒施及条施覆土三种追施氮肥方式下土壤N2O和NH3排放规律、O2浓度及土壤NH+4-N、NO-2-N和NO-3-N的时空动态,揭示追氮方式对两种重要环境气体排放的影响及机制。【方法】试验设置3个处理:1)农民习惯追氮方式—撒施(BC);2)撒施添加10%的硝化抑制剂(BC+DCD);3)条施后覆土(Band)。3个处理均在施肥后均匀灌水20 mm。在夏玉米十叶期追施氮肥后的15天(2014年7月23日至8月8日)进行田间原位连续动态观测,并在玉米成熟期测定产量及吸氮量。采用静态箱-气相色谱法测定土壤N2O排放量,土壤气体平衡管-气相色谱法测定土壤N2O浓度,PVC管-通气法测定土壤NH3挥发,土壤气体平衡管-泵吸式O2浓度测定仪测定土壤O2浓度。【结果】农民习惯追氮方式N2O排放量为N 395 g/hm2,NH3挥发损失为N22.9 kg/hm2,同时还导致土壤在一定程度上积累了NO-2-N。与习惯追氮方式相比,添加硝化抑制剂显著减少N2O排放89.4%,使NH3挥发略有增加,未造成土壤NO-2-N的累积。条施覆土使土壤N2O排放量显著增加将近1倍,但使NH3挥发显著减少69.4%,同时造成施肥后土壤局部高NO-2-N累积。条施覆土的施肥条带上土壤NO-2-N含量与N2O排放通量呈显著正相关。土壤气体的O2和N2O浓度受土壤含水量控制,当土壤WFPS大于60%时,0—20 cm土层中的O2浓度明显降低,而N2O浓度增加,土壤N2O浓度和土壤O2浓度间呈极显著负相关。各处理地上部产量及总吸氮量差异不显著。【结论】土壤NO-2-N的累积与铵态氮肥施肥方式密切相关,NO-2-N的累积能够促进土壤N2O的排放,且在条施覆土时达到显著水平(P<0.05)。追氮方式对N2O和NH3两种气体的排放存在某种程度的此消彼长,添加硝化抑制剂在减少N2O排放的同时会增加NH3挥发,条施覆土在显著减少NH3挥发的同时会显著增加土壤N2O排放。在条施覆土基础上添加硝化抑制剂,有可能同时降低N2O排放和NH3挥发损失,此推论值得进一步研究。

土壤温度对北京旱地农田N_2O排放的影响

在作物生长期内,通过田间自动采样系统的测定和室内温湿模拟实验,对北京地区麦豆轮作生态系统的N2O排放进行了初步研究.结果表明:在10～30℃范围内,随着土壤表层温度的升高,麦豆轮作生态系统的N2O排放通量在不同程度上有一定的增加,但不呈明显的线性相关关系.

旱耕人为土N_2O排放动力学特征及其影响因素

以黄土高原南部典型旱耕地—休闲地土壤为对象 ,研究了中等水分条件下 (6 5 %的田间持水量 )土壤 N2 O排放的动力学特征 ,以及土壤深度和氮磷营养因子对 N2 O排放量的影响。结果表明 ,施肥和未施肥处理 ,土壤 N2 O排放累积量随时间 t的变化均符合修正的 Elovich方程 y=bln(t) +a。反应初始浓度 (a)和表观反应速率(dy/ dt)大多数随土壤深度增加而递增 ,但 15℃时以 10 cm深处反应初始浓度最大 ;2 5℃时 ,表观反应速率以 15cm深处最高 ,即在中等水分条件下 ,随温度升高 ,试验土壤 10～ 15 cm深处为 N2 O产生的活跃场所。磷素对土壤N2 O的减排效应不仅表现在排放总量上 ,也存在于动力学参数初始浓度和表观反应速率之中。

内蒙古河套灌区盐碱土壤N_2O排放特征

选择内蒙古河套灌区强度盐碱土壤S_1[电导率(EC)2.60dS/m]和轻度盐碱土壤S_2[电导率(EC)0.74dS/m]为研究对象,2014～2016年,利用静态箱法3年野外原位观测试验,研究盐碱土壤氧化亚氮(N_2O)排放通量.结果表明:2种不同盐碱程度土壤N_2O排放每年均存在显著差异,轻度盐碱土壤N_2O累积排放量低;随EC升高,土壤盐碱程度加重,土壤N_2O累积排放量升高.2014～2016年作物生长季(4～11月)轻度盐碱土壤N_2O累积排放量分别为180.6,167.6,118.2mg/m^2;强度盐碱土壤N_2O累积排放量比轻度盐碱土壤分别增加19%、26%和45%,修复盐碱土壤成为减缓盐碱土壤N_2O累积排放的重要农艺措施.

Nitrogen cycling and environmental impacts in upland agricultural soils in North China： A review

The upland agricultural soils in North China are distributed north of a line between the Kunlun Mountains, the Qinling Mountains and the Huaihe River. They occur in arid, semi-arid and semi-humid regions and crop production often depends on rain-fed or irrigation to supplement rainfall. This paper summarizes the characteristics of gross nitrogen（N） transformation, the fate of N fertilizer and soil N as well as the N loss pathway, and makes suggestions for proper N management in the region. The soils of the region are characterized by strong N mineralization and nitrification, and weak immobilization and denitrification ability, which lead to the production and accumulation of nitrate in the soil profile. Large amounts of accumulated nitrate have been observed in the vadose-zone in soils due to excess N fertilization in the past three decades, and this nitrate is subject to occasional leaching which leads to groundwater nitrate contamination. Under farmer＇s conventional high N fertilization practice in the winter wheat-summer maize rotation system（N application rate was approximately 600 kg ha–1 yr–1）, crop N uptake, soil residual N, NH_3 volatilization, NO_3~– leaching, and denitrification loss accounted for around 27, 30, 23, 18 and 2% of the applied fertilizer N, respectively. NH_3 volatilization and NO_3~– leaching were the most important N loss pathways while soil residual N was an important fate of N fertilizer for replenishing soil N depletion from crop production. The upland agricultural soils in North China are a large source of N_2O and total emissions in this region make up a large proportion（approximately 54%） of Chinese cropland N_2O emissions. The “non-coupled strong ammonia oxidation” process is an important mechanism of N_2O production. Slowing down ammonia oxidation after ammonium-N fertilizer or urea application and avoiding transient high soil NH4＋ concentrations are key measures for reducing N_2O emissions in this region. Further N management should aim to minimize N losses from crop and livestock production, and increase the recycling of manure and straw back to cropland. We also recommend adoption of the 4 R（Right soure, Right rate, Right time, Right place） fertilization techniques to realize proper N fertilizer management, and improving application methods or modifying fertilizer types to reduce NH_3 volatilization, improving water management to reduce NO_3~– leaching, and controlling the strong ammonia oxidation process to abate N_2O emission. Future research should focus on the study of the trade-off effects among different N loss pathways under different N application methods or fertilizer products.

Effect of calcium silicate on nutrient use of lowland rice and greenhouse gas emission from a paddy soil under alternating wetting and drying

In intensively irrigated rice cultivation,plant-available silicon(Si)is a crucial nutrient for improving rice productivity.As a source of Si,calcium silicate(CaSiO3)was amended to evaluate the effect of silicate fertilizer on rice production,nitrogen(N)use efficiency,and greenhouse gas(GHG)emission under alternating wetting and drying in a pot experiment using a tropical soil from a paddy field of the International Rice Research Institute(IRRI)in the Philippines.Four levels of CaSiO3 amendment,0,112.7,224.5,and 445.8 kg ha^-1,with the recommended N rate were tested.The results showed that although CaSiO3amendment of 112.7 kg ha^-1resulted in higher rice straw,improved N use efficiency,and reduced N2O emission,there was no difference in grain yield among the four levels of CaSiO3 amendment owing to relatively lower harvest index.Moreover,CaSiO3 amendment showed a reverse trend between CH4 and N2O emissions as it reduced N2O emission while led to significantly increased CH4 emission and global warming potential.Thus,CaSiO3 amendment was a possible alternative to improve N use efficiency and increase rice straw biomass,but it needs to be reviewed in line with grain yield production and GHG emission.It is also imperative to test an optimal method of silicate fertilizer amendment in future research in order to compromise a negative impact in tropical soils.

Nitrous oxide emissions from black soils with different pH

N2O fluxes as a function of incubation time from soil with different available N contents and pH were determined. Cumulative carbon dioxide （CO2） emissions were measured to indicate soil respiration. A 144-hr incubation experiment was conducted in a slightly acidic agricultural soil （PHH2o 5.33） after the pH was adjusted to four different values （3.65, 5.00, 6.90 and 8.55）. The experiments consisted of a control without added N, and with NH^-N and NO^-N fertilization. The results showed that soil pH contributed significantly to N20 flux from the soils. There were higher N20 emissions in the period 0-12 hr in the four pH treatments, especially those enhanced with N- fertilization. The cumulative NEO-N emission reached a maximum at pH 8.55 and was stimulated by NO3-N fertilization （70.4 μg/kg）. The minimum emissions appeared at pH 3.65 and were not stimulated by NO3^--N or NH4^＋-N fertilization. Soil respiration increased significantly due to N-fertilization. Soil respiration increased positively with soil pH （R2 = 0.98, P 〈 0.01）. The lowest CO2-C emission （30.2 mg/kg） was presented in pH 3.65 soils without N-fertilization. The highest CO2-C emissions appeared in the pH 8.55 soils for NH4^＋-N fertilization （199 mg/kg）. These findings suggested that N20 emissions and soil respiration were significantly influenced by low pH, which strongly inhibits soil microbial nitrification and denitrification activities. The content of NO3^--N in soil significantly and positively affected the N2O emissions through denitrification.

Variation and driving factors of nitrous oxide emissions from irrigated paddy field in the arid and semiarid region

Agricultural pollution source as Nitrous oxide (N2O) emission from irrigated paddy field as affected by overuse of chemical fertilizer application and flooding irrigation is the primary anthropogenic source of nitrogen (N) losses in the Ningxia irrigation district. The emissions variation and driving factors of N2O emission in the large irrigation districts needs much more investigation. A static chamber-gas chromatograph method was conducted to quantify N losses from a paddy field in Lingwu Farm during 2009– 2010. Three nitrogen (N) treatments were conducted, including the conventional N application rate of 300 kg ha-1 (N300), the reducing N application rate of 240 kg ha-1 (N240) and control plot (N0). The N2O emissions due to combined effects of the fertilizer application and flood irrigation after winter dry follow was 2.86–3.27 kg ha-1 in N300. The flood irrigation at the beginning of the rice transplanting promotes N2O emissions due to nitrification–denitrification of a richer N source provided by the N fertilizer accumulation of soil NH4 + and NO3 -. During the rice growth stage when the paddy field was submerged, N2O emission was very low while intermittent irrigation before tillering and the maturation stages, frequent alteration of dry and wet soil condition enhance N2O emission. The reducing N fertilizer application improved the recovery rate in rice and resulted in a less N2O emission from irrigated paddy field in the arid and semiarid region while keeping the rice yield.

农田土壤活性氮损失现状和生物炭调控途径研究进展

农田N^( 2) O排放与NO^(-)_(3)-N淋失是土壤活性氮损失的主要途径,是全球活性氮污染的重要来源,对全球气候变化和水质安全构成严重威胁。农田活性氮的产生途径与土壤硝化和反硝化作用密切相关,不同种植体系下土壤硝化和反硝化过程存在很大差异,尤其是我国甘蔗等经济作物连作农田长期大量施肥导致大面积土壤加速酸化、土壤硝化程度不断加强,直接影响到农业源活性氮库的变化趋势和控制策略。近年来,生物炭作为一种被广泛关注的多功能化炭基土壤调理剂,在农田活性氮转化调控、土壤改良、农作物稳产增产中具有重要的应用潜力。综述了农田活性氮的损失现状、主要影响因素及其关键微生物过程,指出了生物炭在农田活性氮转化和氮素循环利用中的潜在调控途径,并展望其未来研究发展方向,为我国农田活性氮污染控制、氮肥高效利用以及农业高效绿色与可持续发展研究提供新思路。

灌溉水盐分和灌水量对温室气体排放与玉米生长的影响

为揭示地下水与微咸水灌溉条件下灌水量对土壤CO_(2)、N_(2)O排放和春玉米生长的影响,设置2种灌溉水含盐量(1.1、5.0 g/L)和3种灌水量(210、255、300 mm),于2019年4—9月在内蒙古自治区河套灌区进行了春玉米田间试验。结果表明,不同灌水量下,微咸水(含盐量5.0 g/L)灌溉比地下水(含盐量1.1 g/L)灌溉土壤N_(2)O累积排放量提高了19.86%~44.21%,但利用微咸水灌溉并不会影响土壤CO_(2)累积排放量与全球增温潜势。在相同的灌溉水盐分条件下,灌水量为300 mm时土壤CO_(2)、N_(2)O累积排放量和全球增温潜势均最大,灌水量为210 mm和255 mm时并不会对土壤CO_(2)、N_(2)O的累积排放量和全球增温潜势产生显著影响。相关性分析表明,土壤含水率和无机氮含量是影响土壤CO_(2)、N_(2)O排放的重要因素,灌溉水盐分通过促进土壤的硝化作用促进土壤N_(2)O排放。在微咸水灌溉条件下,春玉米产量较地下水灌溉减少了30.88%~37.32%。随着灌水量的增大,春玉米产量呈增加趋势,但255 mm和300 mm灌水量条件下的春玉米产量差异不显著。在地下水与微咸水灌溉条件下,灌水量为255 mm时,土壤盐分累积较小,春玉米产量较高,土壤CO_(2)、N_(2)O累积排放量和全球增温潜势相对较小,是灌区适宜采用的灌溉定额。