中国东北苹果园中土壤总硝化作用和氧化亚氮排放状况

A better understanding of nitrogen (N) transformation in agricultural soils is crucial for the development of sustainable and environmental-friendly N fertilizer management and the proposal of effective N₂O mitigation strategies. This study aimed: i) to elucidate the seasonal dynamic of gross nitrification rate and N2O emission, ii) to determine the influence of soil conditions on the gross nitrification, and iii) to confirm the relationship between gross nitrification and N₂O emissions in the soil of an apple orchard in Yantai, Northeast China. The gross nitrification rates and N₂O fluxes were examined from March to October in 2009, 2010, and 2011 using the barometric process separation (BaPS) technique and the static chamber method. During the wet seasons gross nitrification rates were 1.64 times higher than those under dry season conditions. Multiple regression analysis revealed that gross nitrification rates were significantly correlated with soil temperature and soil water-filled pore space (WFPS). The relationship between gross nitrification rates and soil WFPS followed an optimum curve peaking at 60% WFPS. Nitrous oxide fluxes varied widely from March to October and were stimulated by N fertilizer application. Statistically significant positive correlations were found between gross nitrification rates and soil N₂O emissions. Further evaluation indicated that gross nitrification contributed significantly to N₂O formation during the dry season (about 86%) but to a lesser degree during the wet season (about 51%). Therefore, gross nitrification is a key process for the formation of N₂O in soils of apple orchard ecosystems of the geographical region.     

黄土高原苹果园间作油菜对土壤水分与苹果品质的影响

[目的]间作生草是黄土高原苹果优势产区有机肥替代化肥模式之一.由于黄土高原地区年际干旱少雨且降水在季节上分配不均,可能产生果园生草与果树争水的问题.因此,本研究采用不同耗水模式的油菜品种探究其对土壤水分及苹果品质的影响.[方法]试验于2018和2019年在陕西省延安市安塞区南沟流域进行.设置4个生草处理,分别为甘蓝型油...     

中国亚热带丘陵区马尾松林氧化亚氮排放

The forest ecosystem plays a pivotal role in contributing greenhouse gases to the atmosphere.In order to characterize the temporal pattern of nitrous oxide(N_2O) emissions and identify the key factors affecting N_2O emissions from a Masson pine forest in a hilly red-soil region in subtropical central China,we measured the N_2O emissions in Jinjing of Hunan Province using the static chambergas chromatographic method for 3 years(2010-2012) and analyzed the relationships between the N_2O fluxes and the environmental variables.Our results revealed that the N_2O fluxes over the 3 years varied from-36.0 to 296.7 μg N m~(-2) h~(-1),averaging 18.4±5.6 μg N m~(-2) h~(-1)(n=3).The average annual N_2O emissions were estimated to be 1.6±0.3 kg N ha~(-1) year~(-1).The N_2O fluxes exhibited clear intra-annual(seasonal) variations as they were higher in summers and lower in winters.Compared with other forest observations in the subtropics,N_2O emissions at our site were relatively high,possibly due to the high local dry/wet N deposition,and were mostly sensitive to variations in precipitation and soil ammonium N content.In this work,a multiple linear regression model was developed to determine the influence of environmental factors on N_2O emissions,in which a category predictor of "Season" was intentionally used to account for the seasonal variation of the N_2O fluxes.Such a model explained almost 40%of the total variation in daily N_2O emissions from the Masson pine forest soil studied(P0.001).     

黄土高原果园土壤pH变化分析

<正>以往的研究表明,生态系统演替进程中,任何层次土壤的pH都减少,随深度增加,减少量降低;演替初期pH减少较快,之后逐渐减慢[1-2]。土壤pH对土壤元素转换、微生物区系、营养元素的有效性以及水土保持等方面有重要影响,并因此对植物生长产生一定影响。     

黄土山地苹果园土壤水分最大利用深度分析

有效利用果园土壤调蓄作用,是进行果园高效水肥管理的基础。该文采用中子仪与烘干法相结合,对黄土山地苹果园土壤水分进行连续9a监测,以达西定律为基础,通过实测果园土壤水分特征参数,分析了黄土山地苹果园土壤水分最大利用深度。结果表明:在有效含水率范围内,根据达西定律,理论山地苹果园土壤水分最大利用深度为3.0～5.17m。黄土山地果园不同坡向间土壤含水率差异明显,阳坡含水率较低,阴坡较高,半阴坡和半阳坡介于两者之间;根据多年实测土壤含水率变化规律,山地苹果园土壤水分最大利用深度分别为:阳坡3.0m,阴坡4.5m,半阳坡3.5m,半阴坡4.0m;在有效含水率范围内,随土壤含水率提高,土壤水分最大利用深度加大。     

Nitrous oxide emissions from kharif and rabi legumes grown on an alluvial soil

Nitrous oxide (N₂O) emissions were monitored for a period of 60 days in a pot culture study, from two kharif (June-September) and two rabi (October-March) season legumes, which were grown on a Typic Ustochrept, alluvial sandy loam soil. Black gram (Vigna mungo L. Hepper), var. T-9, and soybean (Glycine max L. Merril), var. Punjab 1, were taken up in kharif season whereas lentil (Lens esculenta Moench), var. JLS-1, and Bengal gram (Cicer arietinum L.), var. BGD-86, were grown in rabi season. All the crops were grown with and without urea and one pot (containing soil but with no fertilizer or crop) was used as a control. Nitrous oxide emissions were significantly higher in unfertilized cropped soil than in the control, while the addition of urea to the crops further increased the emissions. Significant emissions occurred during third and seventh week after sowing for all the treatments in both kharif and rabi seasons. In kharif, soil cropped with soybean had higher total N₂O-N emission than soil sown with black gram both under fertilized and unfertilized conditions; while in rabi, lentil had a higher total N₂O-N emission than Bengal gram under both fertilized and unfertilized conditions. In kharif, total N₂O-N emissions ranged from 0.53 (control) to 3.84 kg ha^-1 (soybean+urea), while in rabi it ranged from 0.45 (control) to 3.06 kg ha^-1 (lentil+urea). Higher N₂O-N emissions in kharif than in rabi was probably due to the favorable effect of temperature on nitrification and denitrification in the former season. The results of the study indicated that legume crops may lead to an increase in N₂O formation and emission from soils, the extent of which varies from crop to crop.     

Nitrous oxide emissions from boreal organic soil under different land-use

Nitrous oxide emissions were studied with a static chamber technique during 2 years from a drained organic soil in eastern Finland. After drainage, the soil was forested with birch (Betula pendula Roth) and 22 years later, part of the forest was felled and then used for cultivation of barley (Hordeum vulgare L.) and grass. The annual N₂O emissions from the cultivated soil (from 8.3 to 11.0 kg N₂O-N ha⁻¹ year⁻¹) were ca. twice the annual emission from the adjacent forest site (4.2 kg N₂O-N ha⁻¹ year⁻¹). The N₂O emissions from the soils without plants (kept bare by regular cutting or tilling) were also lower (from 6.5 to 7.1 kg N₂O-N ha⁻¹ year⁻¹) than those from the cultivated soil. There was a high seasonal variation in the fluxes with a maximum in spring and early summer. The N₂O fluxes during the winter period accounted for 15-60% of the total annual emissions. N₂O fluxes during the snow-free periods were related to the water table (WT) level, water-filled pore space, carbon mineralisation and the soil temperature. A linear regression model with CO₂ production, WT and soil temperature at the depth of 5 cm as independent variables explained 54% of the variation in the weekly mean N₂O fluxes during the snow-free periods. N₂O fluxes were associated with in situ net nitrification, which alone explained 58% of the variation in the mean N₂O fluxes during the snow-free period. The N₂O-N emissions were from 1.5 to 5% of net nitrification. The acetylene blockage technique indicated that most of the N₂O emitted in the snow-free period originated from denitrification.     

Nitrous oxide emissions from grazed grassland

Abstract. Grazing animals on managed pastures and rangelands have been identified recently as significant contributors to the global N₂O budget. This paper summarizes relevant literature data on N₂O emissions from dung, urine and grazed grassland, and provides an estimate of the contribution of grazing animals to the global N₂O budget.
The effects of grazing animals on N₂O emission are brought about by the concentration of herbage N in urine and dung patches, and by the compaction of the soil due to treading and trampling. The limited amount of experimental data indicates that 0.1 to 0.7% of the N in dung and 0.1 to 3.8% of the N in urine is emitted to the atmosphere as N₂O. There are no pertinent data about the effects of compaction by treading cattle on N₂O emission yet. Integral effects of grazing animals have been obtained by comparing grazed pastures with mown-only grassland. Grazing derived emissions, expressed as per cent of the amount of N excreted by grazing animals in dung and urine, range from 0.2 to 9.9%, with an overall mean of 2%. Using this emission factor and data statistics from FAO for numbers of animals, the global contribution of grazing animals was estimated at 1.55 Tg N₂O-N per year. This is slightly more than 10% of the global budget.     

Nitrous oxide emissions from wetland soil amended with inorganic and organic fertilizers

Agricultural soils are a primary source of anthropogenic trace gas emissions, and the subtropics contribute greatly, particularly since 51% of world soils are in these climate zones. A field experiment was carried out in an ephemeral wetland in central Zimbabwe in order to determine the effect of cattle manure (1.36% N) and mineral N fertilizer (ammonium nitrate, 34.5% N) application on N₂O fluxes from soil. Combined applications of 0 kg N fertilizer + 0 Mg cattle manure ha^?1 (control), 100 kg N fertilizer + 15 Mg manure ha^?1 and 200 kg N fertilizer + 30 Mg manure ha^?1 constituted the three treatments arranged in a randomized complete block design with four replications. Tomato and rape crops were grown in rotation over a period of two seasons. Emissions of N₂O were sampled using the static chamber technique. Increasing N fertilizer and manure application rates from low to high rates increased the N₂O fluxes by 37–106%. When low and high rates were applied to the tomato and rape crops, 0.51%, 0.40%, and 0.93%, 0.64% of applied N was lost as N₂O, respectively. This implies that rape production has a greater N₂O emitting potential than the production of tomatoes in wetlands.     

Nitrous oxide emission from an irrigated cotton field under semiarid subtropical conditions

In a 1-year study, quantification of nitrous oxide (N₂O) emission was made from a flood-irrigated cotton field fertilized with urea at 100kg N ha⁻¹ a⁻¹. Measurements were made during the cotton-growing season (May–November) and the fallow period (December–April). Of the total 95 sampling dates, 77 showed positive N₂O fluxes (range, 0.1 to 33.3g N ha⁻¹ d⁻¹), whereas negative fluxes (i.e., N₂O sink activity) were recorded on 18 occasions (range, −0.1 to −2.2g N ha⁻¹ d⁻¹). Nitrous oxide sink activity was more frequently observed during the growing season (15 out of 57 sampling dates) as compared to the fallow period (3 out of 38 sampling dates). During the growing season, contribution of N₂O to the denitrification gaseous N products was much less (average, 4%) as compared to that during the fallow period (average, 21%). Nitrous oxide emission integrated over the 6-month growing period amounted 324g N ha⁻¹, whereas the corresponding figure for the 6-month fallow period was 648g N ha⁻¹. Subtracting the N₂O sink activity (30.3g N ha⁻¹ and 3.8g N ha⁻¹ during the growing season and fallow period, respectively), the net N₂O emission amounted 938g N ha⁻¹ a⁻¹. Results suggested that high soil moisture and temperature prevailing under flood-irrigated cotton in the Central Punjab region of Pakistan though favor high denitrification rates, but are also conducive to N₂O reduction thus leading to relatively low N₂O emission.     

Nitrous oxide emissions from cattle-impacted pasture soil amended with nitrate and glucose

There is little information concerning N₂O fluxes in the pasture soil that has received large amounts of nutrients, such as urine and dung, for several years. The aims of this study were to (1) experimentally quantify the relationship between mineral N input and N₂O emissions from denitrification, (2) describe the time course of N₂O fluxes resulting in N inputs, and (3) find whether there exists an upper limit of the amount of nitrogen escaping the soil in the form of N₂O. The study site was a grassland used as a cattle overwintering area. It was amended with KNO₃ and glucose corresponding to 10–1,500 kg N and C per hectare, covering the range of nutrient inputs occurring in real field conditions. Using manual permanent chambers, N₂O fluxes from the soil were monitored for several days after the amendments. The peak N₂O emissions were up to 94 mg N₂O–N m⁻² h⁻¹, 5–8 h after amendment. No upper limit of N₂O emissions was detected as the emissions were directly related to the dose of nutrients in the whole range of amendments used, but the fluxes reflected the soil and environmental conditions, too. Thus, in three different experiments performed during the season, the total cumulative losses of N₂O–N ranged from 0.2 to 5.6% of the applied 500kg ha⁻¹. Splitting of high nutrient doses lowered the rate of N₂O fluxes after the first amendment, but the effect of splitting on the total amount of N₂O–N released from the soil was insignificant, as the initial lower values of emissions in the split variants were compensated for by a longer duration of gas fluxes. The results suggest that the cattle-impacted soil has the potential to metabolize large inputs of mineral nitrogen over short periods (∼days). Also, the emission factors for did not exceed values reported in literature.     

Nitrous oxide and methane emissions from different soil suspensions: effect of soil redox status

Four soil samples from fields of different land use [US (paddy field), China (paddy field) and Belgium (maize and wheat fields)] were incubated as soil suspension (soil:water ratio 1:4) to study the N₂O and CH₄ emission under different soil redox potential conditions. The results show that the N₂O emission was regulated within a narrow redox potential range of +120 to +250 mV, due to the balance of N₂O production and its further reduction to N₂. Methane emission occurred below a soil specific redox potential point, and the emission rates were inversely related to soil redox potentials. Both linear and exponential relationships between CH₄ emission and the soil redox potential were significant. By extrapolating the linear relationship of CH₄ emission against soil redox potential, the critical redox potentials for CH₄ production were estimated at about -170 (US paddy soil), -150 (Chinese paddy soil), -215 (Belgian maize soil), and -195 mV (Belgian wheat soil), respectively. In addition, the results indicate that a soil with a lower critical redox potential for CH₄ production had a higher CH₄ production potential. In this study, N₂O and CH₄ emissions were found to occur at a distinctly different soil redox potential condition. The range of soil redox potential values where both N₂O and CH₄ emissions were low was different for different soils, but it was situated between +120 and -170 mV. This is a wide redox potential range enabling field management practices to minimize both N₂O and CH₄ emissions from wetland ecosystems.     

Nitrous oxide emissions from a rainfed-cultivated black soil in Northeast China: effect of fertilization and maize crop

Nitrous oxide emission (N₂O) from applied fertilizer across the different agricultural landscapes especially those of rainfed area is extremely variable (both spatially and temporally), thus posing the greatest challenge to researchers, modelers, and policy makers to accurately predict N₂O emissions. Nitrous oxide emissions from a rainfed, maize-planted, black soil (Udic Mollisols) were monitored in the Harbin State Key Agroecological Experimental Station (Harbin, Heilongjiang Province, China). The four treatments were: a bare soil amended with no N (C0) or with 225?kg?N ha^?1 (CN), and maize (Zea mays L.)-planted soils fertilized with no N (P0) or with 225?kg?N ha^?1 (PN). Nitrous oxide emissions significantly (P?<?0.05) increased from 141?±?5?g N₂O-N?ha^?1 (C0) to 570?±?33?g N₂O-N?ha^?1 (CN) in unplanted soil, and from 209?±?29?g N₂O-N?ha^?1 (P0) to 884?±?45?g N₂O-N?ha^?1 (PN) in planted soil. Approximately 75?% of N₂O emissions were from fertilizer N applied and the emission factor (EF) of applied fertilizer N as N₂O in unplanted and planted soils was 0.19 and 0.30?%, respectively. The presence of maize crop significantly (P?<?0.05) increased the N₂O emission by 55?% in the N-fertilized soil but not in the N-unfertilized soil. There was a significant (P?<?0.05) interaction effect of fertilization?×?maize on N₂O emissions. Nitrous oxide fluxes were significantly affected by soil moisture and soil temperature (P?<?0.05), with the temperature sensitivity of 1.73–2.24, which together explained 62–76?% of seasonal variation in N₂O fluxes. Our results demonstrated that N₂O emissions from rainfed arable black soils in Northeast China primarily depended on the application of fertilizer N; however, the EF of fertilizer N as N₂O was low, probably due to low precipitation and soil moisture.     

Nitrous oxide production at different soil moisture contents in an arable soil in China

Abstract

Laboratory incubations were conducted to investigate nitrous oxide (N₂O) production from a subtropical arable soil (Typic Plinthodults) incubated at different soil moisture contents (SMC) and with different nitrogen sources using a 10% (v/v) acetylene (C₂H₂) inhibitory technique at 25°C. The production of N₂O and CO₂ was monitored during the incubations and changes in the contents of KCl-extractable NO^? ₃-N and NH⁺ ₄-N were determined. The production of N₂O increased slightly with an increase in SMC from 40% water-holding capacity (WHC) to 70% WHC, but increased dramatically at 100% WHC. After incubation the NO^? ₃-N content increased even at a SMC of 100% WHC. At a SMC of 100% WHC, the addition of NH⁺ ₄-N promoted the production of N₂O and CO₂, whereas the addition of NO^? ₃-N decreased N₂O production. Compared with the incubation without C₂H₂, the presence of C₂H₂ increased NH⁺ ₄-N content, but decreased NO^? ₃-N content, and there was no significant difference in N₂O production. These results indicate that heterotrophic nitrification contributes to N₂O production in the soil.     

Nitrous oxide emissions under different soil and land management conditions

Nitrous oxide (N₂O) emissions of three different soils – a rendzina on cryoturbed soil, a hydromorphic leached brown soil and a superficial soil on a calcareous plateau – were measured using the chamber method. Each site included four types of land management: bare soil, seeded unfertilized soil, a suboptimally fertilized rapeseed crop and an overfertilized rapeseed crop. Fluxes varied from –1g to 100g N₂O-nitrogen ha^–1 day^–1. The highest rates of N₂O emissions were measured during spring on the hydromorphic leached brown soil which had been fertilized with nitrogen (N); the total emissions during a 5-month period exceeded 3500gNha^–1. Significant fluxes were also observed during the summer. Very marked effects of soil type and management were observed. Two factors – the soil hydraulic behaviour and the ability of the microbial population to reduce N₂O – appear to be essential in determining emissions of N₂O by soils. In fact, the hydromorphic leached brown soil showed the highest emissions, despite having the lowest denitrification potential because of its water-filled pore space and low N₂O reductase activity. Soil management also appears to affect both soil nitrate content and N₂O emissions. Received: 4 April 1997     

Effects of grazing on soil physical properties and soil erodibility in semiarid grassland of the Northern Loess Plateau (China)

Grazing animals provide a livelihood for farmers, but they may also produce adverse environmental effects. We investigated whether grazing leads to deterioration of soil physical properties that subsequently increases topsoil erodibility. We sampled three sites (an ungrazed grassland, a continuously grazed grassland, and a track trampled by stock) on the northern Loess Plateau of China. The bulk density, water content, proportion of stable aggregates, infiltration rate, and resistance to scouring were determined for each soil sample. The results showed that the track had the highest soil bulk density and the lowest soil water content, proportion of stable aggregates, infiltration rate, and ability to resist scouring. The ungrazed plots had the best results for these parameters, in terms of reduced erosion. Soil bulk density and the proportion of stable aggregates differed significantly with depth beneath the track. However, the effect of depth on water content, infiltration rate, and the soil resistance to scouring was not significant at any sampling site. The ability of the soil to resist scouring was negatively correlated with the soil's bulk density and positively correlated with the soil's water content, infiltration rate, and proportion of stable aggregates. Thus, soil physical properties played an important role in determining soil erodibility. Grazing and trampling by livestock therefore appear to cause deterioration of soil physical properties and to increase soil erodibility.     

Evaluation of CLIGEN for storm generation on the semiarid Loess Plateau in China

The Stochastic generation of storm patterns is often necessary for driving process-based hydrological and ecological models. CLIGEN is the only weather generator being able to generate internal storm patterns. Its goodness needs to be evaluated for its proper application. This paper aims to find the advantages and limitations of CLIGEN on semiarid areas and provide references for custom-built weather generators for the Loess Plateau. The daily rainfall time series (1957–2002) and breakpoint rainfall data (more than 20 years) on six stations on the Loess Plateau were used to estimate input parameters for CLIGEN and to compare with CLIGEN-generated 50 years of storm data. Precipitation occurrence (wet day and dry day sequence) is well-simulated without significant difference across months and sites. Errors of monthly average number of wet days range from − 0.67 to 1.08 days, standard deviations range from − 1.19 to 0.76 days, and the distributions of continuous number of wet and dry days on the semiarid Loess Plateau are adequately simulated. Daily rainfall amount is not simulated as well as precipitation occurrence. The relative errors of average daily rainfall range from − 12.93% to 8.64% and those of standard deviations range from − 21.35% to 27.46%. During the rain seasons (May–September), among 30 month–location combinations, all the Mann–Whitney tests for the means passed, 47% for squared ranks tests rejected the null hypothesis of equality of standard deviations, and 73% for K–S test suggested that the generated and measured distributions of daily rainfall were different at 0.01 level of significance Three variables to describe internal storm patterns in CLIGEN are storm duration, relative peak intensity, and time to peak. Storm duration was not well-reproduced because none of squared ranks tests and K–S test passed at the significance level of 0.01. The frequency of short duration storms (< 300 min) was over-predicted while frequency of long duration storms (400–1200 min) was significantly under-predicted. The distribution of maximum 5 min rainfall intensity (ip₅) was well-simulated for four sites out of the six because all tests passed. However, generated maximum ip₅ for all six sites are around 190 mm/h, which are much larger than the measured (70 to 150 mm/h). Ip₃₀ is simulated better than ip₅, suggesting that CLIGEN can reliably generate rainfall erosivity. Time to peak was well-simulated because all the tests passed with P values significantly greater than the significance level of P = 0.01. Improvement for CLIGEN has to be made in terms of the daily rainfall simulation in rainfall-concentrated seasons and storm pattern generation in order to generate reliable rainfall time series on the Loess plateau.     

Nitrous oxide emissions from soil amended with glucose,alfalfa, or corn residues

Abstract

Nitrous oxide (N₂O) emissions result from the nitrification and denitrification processes, the latter strongly affected by soil organic carbon (C) derived from plant residues. This study addressed two questions: (1) does plant residue C become less available to denitrifiers after a period of aerobic incubation, and (2) do plant residues with smaller particle sizes provide C for higher rates of N₂O production due to a faster decomposition rate? Nitrous oxide fluxes from soil amended with alfalfa or corn residues, or glucose were measured in the laboratory using a gas flow‐through chamber system. Soil amended with these C substrates was also subjected to a 5‐d aerobic preincubation treatment. The significance of particle size on C availability was studied by comparing N₂O released from soil amended with ground (particle size <1 mm) and large pieces (5‐cm lengths) of alfalfa residues. A 5‐d aerobic preincubation of soil amended with plant residues resulted in reduced N₂O production during a subsequent anaerobic period. Results suggested that, due to consumption of the most available substrate, remaining C in plant residues is less available to denitrifiers after a period of aerobic incubation. Higher N₂O losses were found with large alfalfa particles than with ground alfalfa.     

Nitrous oxide emissions from dairy farm effluent applied to a New Zealand pasture soil

A field experiment on permanent ryegrass–white clover pasture at AgResearch's Ruakura dairy farm near Hamilton, New Zealand quantified nitrous oxide (N₂O) emissions from different types of dairy effluent applied to soil at three seasons and evaluated the potential of dicyandiamide (DCD) (a nitrification inhibitor) to decrease gaseous N₂O emissions. Fresh or stored manure and farm dairy effluent (FDE; from dairy shed washings), with or without DCD (10 kg/ha), were applied at approximately 100 kg N/ha to plots on a well‐drained soil on volcanic parent material. A field chamber technique was used to measure N₂O emissions. Application of manure or FDE, both in fresh and stored forms, to pasture generally increased N₂O emissions. Overall N₂O emission factors (EF) varied between 0.01% and 1.87%, depending on application season and effluent type. EFs in spring and autumn were greater than those in summer (P < 0.05). Among the effluents, N₂O EFs were largest from fresh FDE (1.65%) during the spring measurement period, stored manure (1.87%) during the autumn and stored FDE (0.25%) during the summer. DCD was effective in decreasing N₂O EFs from fresh FDE, fresh manure, stored FDE and stored manure by 40–80%, 69–76%, 24–84% and 60–70%, respectively. DCD reduced N₂O emissions during the spring and autumn seasons more effectively than in the summer season.