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 and dynamics of soil nitrogen under 15N‐labeled cow urine and dung patches on a sandy grassland soil

Grazing animals highly influence the nutrient cycle by a direct return of 80% of the consumed N in form of dung and urine. In the autumn‐winter period, N uptake by the sward is low and rates of seepage water in sandy soils are high, hence high mineral‐N contents in soil and in seepage water as well as large losses of N₂O are expected after cattle grazing in autumn. The objective of this study was the quanitfication of N loss deriving from urine and dung leaching and by N₂O emission. Therefore the deposition of urine and dung patches was simulated in maximum rates excreted by cows by application of ¹⁵N‐labeled cow urine and dung (equivalent to 1030 kg N ha^–1 and 1052 kg N ha^–1, respectively) on a sandy pasture soil in N Germany. Leachate was collected in weekly intervals from free‐draining lysimeters, and ¹⁵N‐NO , ¹⁵N‐NH , and ¹⁵N‐DON (dissolved organic N) were monitored over 171 d. Furthermore, the ¹⁵N‐N₂O emission rates and the dynamics of inorganic ¹⁵N in the upper soil layer were monitored in a field trial, adjacent to the lysimeters. After 10 d following the urine application, the urea was completely hydrolyzed, shown by a 100% recovery of urine‐N in the soil NH . The following decrease of ¹⁵N‐NH in the soil was higher than the increase of ¹⁵N‐NO , and some N loss was explained by leaching. Amounts of 51% and 2.5% of the applied ¹⁵N were found in leachate as inorganic N, 2.4% and 0.7% as DON derived from urine and dung, respectively. Release of N₂O from urine and dung patches applied to the pasture was low, with losses of 0.05% and 0.33% of the applied ¹⁵N, respectively. Overall loss of dung‐derived N was very low, but as the bulk dung N remained in the soil, N loss after mineralization of the dung needs to be investigated.     

Nitrous oxide and carbon dioxide emissions from grassland amended with sewage sludge

Abstract. Land disposal of sewage sludge in the UK is set to increase markedly in the next few years and much of this will be applied to grassland. Here we applied high rates of digested sludge cake (1–1.5×10³ kg total N ha⁻¹) to grassland and incorporated it prior to reseeding. Using automated chambers, nitrous oxide (N₂O) and carbon dioxide (CO₂) fluxes from the soil were monitored 2–4 times per day, for 6 months after sludge incorporation. Peaks of N₂O emission were up to 1.4 kg N ha⁻¹ d⁻¹ soon after incorporation, and thereafter were regularly detected following significant rainfalls. Gas emissions reflected diurnal temperature variations, though N₂O emissions were also strongly affected by rainfall. Although emissions decreased in the winter, temperatures below 4 °C stimulated short, sharp fluxes of both CO₂ and N₂O as temperature increased. The aggregate loss of nitrogen and carbon over the measurement period was up to 23 kg N ha⁻¹ and 5.1 t C ha⁻¹. Losses of N₂O in the sludge-amended soil were associated with good microbial conditions for N mineralization, and with high carbon and water contents. Since grassland is an important source of greenhouse gases, application of sewage sludge can be at least as significant as fertilizer in enhancing these emissions.     

Mitigation of N2O emissions from grassland by nitrification inhibitor and Actilith F2 applied with fertilizer and cattle slurry

Abstract. Nitrous oxide (N₂O) is involved in both ozone destruction and global warming. In agricultural soils it is produced by nitrification and denitrification mainly after fertilization. Nitrification inhibitors have been proposed as one of the management tools for the reduction of the potential hazards of fertilizer-derived N₂O. Addition of nitrification inhibitors to fertilizers maintains soil N in ammonium form, thereby gaseous N losses by nitrification and denitrification are less likely to occur and there is increased N utilization by the sward. We present a study aimed to evaluate the effectiveness of the nitrification inhibitor dicyandiamide (DCD) and of the slurry additive Actilith F2 on N₂O emissions following application of calcium ammonium nitrate or cattle slurry to a mixed clover/ryegrass sward in the Basque Country. The results indicate that large differences in N₂O emission occur depending on fertilizer type and the presence or absence of a nitrification inhibitor. There is considerable scope for immediate reduction of emissions by applying DCD with calcium ammonium nitrate or cattle slurry. DCD, applied at 25 kg ha^–1, reduced the amount of N lost as N₂O by 60% and 42% when applied with cattle slurry and calcium ammonium nitrate, respectively. Actilith F2 did not reduce N₂O emissions and it produced a long lasting mineralization of previously immobilized added N.     

Nitrous oxide and methane emissions from grassland treated with bark- or sawdust-containing manure at different rates

On the main Japanese island of Honshu, bark or sawdust is often added to cattle excreta as part of the composting process. Dairy farmers sometimes need to dispose of manure that is excess to their requirements by spreading it on their grasslands. We assessed the effect of application of bark- or sawdust-containing manure at different rates on annual nitrous oxide (N₂O) and methane (CH₄) emissions from a grassland soil. Nitrous oxide and CH₄ fluxes from an orchardgrass (Dactylis glomerata L.) grassland that received this manure at 0, 50, 100, 200, or 300?Mg?ha^?1?yr^?1 were measured over a two-year period by using closed chambers. Two-way analysis of variance (ANOVA) was employed to examine the effect of annual manure application rates and years on annual N₂O and CH₄ emissions. Annual N₂O emissions ranged from 0.47 to 3.03?kg?N?ha^?1?yr^?1 and increased with increasing manure application rate. Nitrous oxide emissions during the 140-day period following manure application increased with increasing manure application rate, with the total nitrogen concentration in the manure, and with cumulative precipitation during the 140-day period. However, manure application rate did not affect the N₂O emission factors of the manure. The overall average N₂O emission factor was 0.068%. Annual CH₄ emissions ranged from ?1.12 to 0.01?kg?C?ha^?1?yr^?1. The annual manure application rate did not affect annual CH₄ emissions.     

Nitrous oxide emissions from potato cropping under drip-fertigation in eastern Germany

In this article, a drip-fertigation system was compared to a control without irrigation concerning the amount of nitrous oxide (N₂O) emissions under the climatic conditions of north-east Germany. The investigation was carried out at a field research station in the federal state of Brandenburg. The mean N₂O emissions under drip-fertigation were significantly higher than under non-irrigation. The higher N₂O emissions under drip-fertigation can be explained by a constantly higher water-filled pore space (WFPS). These higher values in WFPS were caused by the necessary nutrient supply in combination with additional water application in periods with frequent rainfall.     

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 and nitrogen cycling in managed grassland in Southern Hokkaido,Japan

Abstract

Nitrous oxide (N₂O) emissions were measured and nitrogen (N) budgets were estimated for 2?years in the fertilizer, manure, control and bare plots established in a reed canary grass (Phalaris arundinacea L.) grassland in Southern Hokkaido, Japan. In the manure plot, beef cattle manure with bark was applied at a rate of 43–44?Mg fresh matter (236–310?kg?N)?ha^?1?year^?1, and a supplement of chemical fertilizer was also added to equalize the application rate of mineral N to that in the fertilizer plots (164–184?kg?N?ha^?1?year^?1). Grass was harvested twice per year. The total mineral N supply was estimated as the sum of the N deposition, chemical fertilizer application and gross mineralization of manure (GMm), soil (GMs), and root-litter (GMl). GMm, GMs and GMl were estimated by dividing the carbon dioxide production derived from the decomposition of soil organic matter, root-litter and manure by each C?:?N ratio (11.1 for soil, 15.5 for root-litter and 23.5 for manure). The N uptake in aboveground biomass for each growing season was equivalent to or greater than the external mineral N supply, which is composed of N deposition, chemical fertilizer application and GMm. However, there was a positive correlation between the N uptake in aboveground biomass and the total mineral N supply. It was assumed that 58% of the total mineral N supply was taken up by the grass. The N supply rates from soil and root-litter were estimated to be 331–384?kg?N?ha^?1?year^?1 and 94–165?kg?N?ha^?1?year^?1, respectively. These results indicated that the GMs and GMl also were significant inputs in the grassland N budget. The cumulative N₂O flux for each season showed a significant positive correlation with mineral N surplus, which was calculated as the difference between the total mineral N supply and N uptake in aboveground biomass. The emission factor of N₂O to mineral N surplus was estimated to be 1.2%. Furthermore, multiple regression analysis suggested that the N₂O emission factor increased with an increase in precipitation. Consequently, soil and root-litter as well as chemical fertilizer and manure were found to be major sources of mineral N supply in the grassland, and an optimum balance between mineral N supply and N uptake is required for reducing N₂O emission.     

不同水稻、小麦品种对N2O排放的影响

Plant species of cropping systems may affect nitrous oxide (N2O) emissions. A field experiment was conducted to investigate dynamics of N2O emissions from rice-wheat fields from December 2006 to June 2007 and the relationship between soil and plant parameters with N2O emissions. The results indicated that N2O emissions from different wheat varieties ranged from 12 to 291 μg N2O-N m-2 h-1 and seasonal N2O emissions ranged from 312 to 385 mg N2O-N m-2. In the rice season, it was from 11 to 154 μg N2O-N m-2 h-1 with seasonal N2O emission of 190--216 mg N2O-N m-2. The seasonal integrated flux of N2O differed significantly among wheat and rice varieties. The wheat variety HUW 234 and rice variety Joymoti showed higher seasonal N2O emissions. In the wheat season, N2O emissions correlated with soil organic carbon (SOC), soil NO3--N, soil temperature, shoot dry weight, and root dry weight. Among the variables assessed, soil temperature followed by SOC and soil NO3--N were considered as the important variables influencing N2O emission. N2O emission in the rice season was significantly correlated with SOC, soil NO3--N, soil temperature, leaf area, shoot dry weight, and root dry weight. The main driving forces influencing N2O emission in the rice season were soil NO3--N, leaf area, and SOC.     

3, 4-Dimethylpyrazole phosphate reduces nitrous oxide emissions from grassland after slurry application

Abstract. A field study was conducted to assess the effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP), applied at a rate of 1 kg ha⁻¹, on nitrous oxide (N₂O) emissions, forage production and N extraction from a grassland soil after cattle slurry applications in autumn and spring. Nitrous oxide emissions were measured daily or weekly using the closed chamber technique. DMPP efficiency after slurry application was lower in spring (16.7 °C mean soil temperature) than in autumn (11.4 °C mean soil temperature). Thus, DMPP was able to maintain soil mineral N in the ammonium form for 22 days and reduce cumulative N₂O emissions by 69% in autumn, while in spring its effect on soil mineral N lasted for 7–14 days, reducing cumulative N₂O losses by 48%. Furthermore, application of DMPP after slurry did not decrease biomass yield or N uptake.     

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.     

A test of a winter farm management option for mitigating nitrous oxide emissions from a dairy farm

A trial was conducted in 2004 and 2005 to evaluate the effect of a stand‐off winter stock management system on nitrous oxide (N₂O) emissions from a dairy farm in New Zealand. The management system consisted of removing cows from pasture after grazing for 6 h per day and keeping them on a stand‐off pad for the rest of the day during the late autumn/winter seasons in order to reduce soil physical damage because of grazing on wet soils. The N₂O emissions were measured on pasture that was grazed either for all day or for 6 h. The N₂O emissions from the stand‐off pad were also measured. A closed chamber technique was used for measuring N₂O fluxes. The New Zealand International Panel for Climate Change inventory methodology was used to calculate annual N₂O emissions from land application of farm effluent, leached and volatilized N. Significantly lower (P < 0.05) N₂O emission rates were found when the stand‐off grazed pasture was compared to the control in the winter seasons when soil was wet. Total N₂O emission rates measured over one grazing interval in the late autumn/winter (May–August) in 2004 were 2.72 and 1.21 kg N₂O‐N/ha for the control and the stand‐off grazed pastures, respectively. The respective emissions in 2005 were 0.97 and 0.22 kg N₂O‐N/ha. When all possible sources contributing to emissions of N₂O (both measured and calculated from the non‐measured sources) were included, total annual emissions of 7.7 and 7.0 kg N₂O‐N per hectare of grazed pasture in the control and stand‐off treatments, respectively, were estimated. These results suggest that the use of stand‐off pads as a management practice during the wet seasons can be effective at reducing N₂O emissions from dairy farm systems.     

Nitrous oxide emissions after application of inorganic fertilizer and incorporation of green manure residues

Abstract. Emissions of N₂O were measured after application of NH₄NO₃ fertilizer and incorporation of winter wheat and rye green manures in two field experiments in southeast England. Incorporation of green manure alone resulted in temporary immobilization of soil N, small N₂O emissions and also low availability of N for the following crop. Emissions were increased after application of inorganic fertilizer, and were further increased from integrated management treatments whereby green manure residues were incorporated after fertilizer application. The highest emission was from the incorporated winter wheat green manure plus fertilizer treatment, with 1.5 kg N₂O-N ha⁻¹ (0.6% of N applied) being emitted over the first 55 days after incorporation. This high emission was attributed to the supply of C in the residues providing the energy for denitrification in the presence of large amounts of mineral N and the creation of anaerobic microsites during microbial respiration.     

Nitrous oxide and nitric oxide fluxes from cornfield,grassland, pasture and forest in a watershed in Southern Hokkaido,Japan

Abstract

To develop an advanced method for estimating nitrous oxide (N₂O) emission from an agricultural watershed, we used a closed-chamber technique to measure seasonal N₂O and nitric oxide (NO) fluxes in cornfields, grassland, pastures and forests at the Shizunai Experimental Livestock Farm (467 ha) in southern Hokkaido, Japan. From 2000 to 2004, N₂O and NO fluxes ranged from –137 to 8,920 µg N m^?2 h^?1 and from –12.1 to 185 µg N m^?2 h^?1, respectively. Most N₂O/NO ratios calculated on the basis of these N₂O and NO fluxes ranged between 1 and 100, and the log-normal N₂O/NO ratio was positively correlated with the log-normal N₂O fluxes (r ² = 0.346, P < 0.01). These high N₂O fluxes, therefore, resulted from increased denitrification activity. Annual N₂O emission rates ranged from –1.0 to 81 kg N ha^?1 year^?1 (average = 6.6 kg N ha^?1). As these emission values varied greatly and included extremely high values, we divided them into two groups: normal values (i.e. values lower than the overall average) and high values (i.e. values higher than average). The normal data were significantly positively correlated with N input (r ² = 0.61, P < 0.01) and the “higher” data from ungrazed fields were significantly positively correlated with N surplus (r ² = 0.96, P < 0.05). The calculated probability that a high N₂O flux would occur was weakly and positively correlated with precipitation from May to August. This probability can be used to represent annual variation in N₂O emission rates and to reduce the uncertainty in N₂O estimation.     

The use of a nitrification inhibitor, dicyandiamide (DCD), to decrease nitrate leaching and nitrous oxide emissions in a simulated grazed and irrigated grassland

Abstract. In grazed dairy pasture systems, a major source of NO₃^– leached and N₂O emitted is the N returned in the urine from the grazing animal. The objective of this study was to use lysimeters to measure directly the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in decreasing NO₃^– leaching and N₂O emissions from urine patches in a grazed dairy pasture under irrigation. The soil was a free‐draining Lismore stony silt loam (Udic Haplustept loamy skeletal) and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The use of DCD decreased NO₃^–‐N leaching by 76% for the urine N applied in the autumn, and by 42% for urine N applied in the spring, giving an annual average reduction of 59%. This would reduce the NO₃^–‐N leaching loss in a grazed paddock from 118 to 46 kg N ha^–1 yr^–1. The NO₃^–‐N concentration in the drainage water would be reduced accordingly from 19.7 to 7.7 mg N L^–1, with the latter being below the drinking water guideline of 11.3 mg N L^–1. Total N₂O emissions following two urine applications were reduced from 46 kg N₂O‐N ha^–1 without DCD to 8.5 kg N₂O‐N with DCD, representing an 82% reduction. In addition to the environmental benefits, the use of DCD also increased herbage production by more than 30%, from 11 to 15 t ha^–1 yr^–1. The use of DCD therefore has the potential to make dairy farming more environmentally sustainable by reducing NO₃^– leaching and N₂O emissions.     

Nitrous oxide emissions from arable soils in Germany — An evaluation of six long‐term field experiments

In this study emissions of N₂O from arable soils are summarized using data from long‐term N₂O monitoring experiments. The field experiments were conducted at six sites in Germany between 1992 and 1997. The annual N‐application rate ranged from 0 to 350 kg N ha^—1. Mineral and organic N‐fertilizer applications were temporarily split adapted to the growth stage of each crop. N‐fertilizer input and N‐yield by the crops were used to calculate the In/Out‐balance. The closed chamber technique was applied to monitor the N₂O fluxes from soil into the atmosphere. If possible, plants were included in the covers. Annual N₂O emission values were based on flux rate measurements of an entire year. The annual N₂O losses ranged from 0.53 to 16.78 kg N₂O‐N ha^—1 with higher N₂O emissions from organically fertilized plots as compared to minerally fertilized plots. Approximately 50% of the total annual emissions occurred during winter. No significant relationship between annual N₂O emissions and the respective N‐fertilization rate was found. This was attributed to site‐ and crop‐specific effects on N₂O emission. The calculation of the N₂O emission per unit N‐yield from winter cereal plots indicates that the site effect on N₂O emission is more important than the effect of N‐fertilization. From unfertilized soils at the sites Braunschweig and Timmerlah a N‐yield of 60.0 kg N ha^—1 a^—1 and N₂O emissions of 2 kg N ha^—1 a^—1 were measured. This high background emission was assigned to the amount and turnover of soil organic matter. For a crop rotation at the sites Braunschweig and Timmerlah the N In/Out‐balance over a period of four years was identified as a suitable predictor of N₂O emissions. This parameter characterizes the efficiency of N‐fertilization for crop production and allows for N‐mineralization from the soil.     

土壤氧化亚氮排放时空变异性及其方法研究进展

茶园土壤是重要的N₂O排放源,了解茶园土壤N₂O排放因素,为减排措施提供一定的理论依据。基于全球田间原位监测和室内培养试验的茶园土壤文献数据进行荟萃分析（Meta analysis）,量化茶园土壤N₂O年排放量,分析主要影响因素。全球茶园土壤田间原位监测结果表明平均N₂O-N年排放量为16.82 kg hm⁻²（95%置信区间（CI）：12.99 ~ 21.27 kg hm⁻²）,而室内培养试验结果表明N₂O-N排放速度为0.04 mg kg⁻¹ d⁻¹（CI：0.02 ~ 0.07 mg kg⁻¹ d⁻¹）。茶园土壤N₂O平均直接排放系数（EF_d）为2.25%,高于IPCC的建议值（1%）。方差分解分析（VPA）发现施氮量对茶园土壤N₂O排放的总解释量最大,贡献值为49.71%。施缓控释肥、生物炭和石灰材料分别可以减少茶园土壤35%、52%和55%的N₂O排放。上述结果表明,茶园土壤N₂O排放量大,施肥量是主控因子,通过改良施肥措施可有效减少N₂O排放。     

Effects of application of lime nitrogen and dicyandiamide on nitrous oxide emissions from green tea fields

Abstract

The aim of this study was to assess the mitigating effects of lime nitrogen (calcium cyanamide) and dicyandiamide (DCD) application on nitrous oxide (N₂O) emissions from fields of green tea [Camellia sinensis (L.) Kuntze]. The study was conducted in experimental tea fields in which the fertilizer application rate was 544 kg nitrogen (N) ha^?1 yr^?1 for 2 years. The mean cumulative N₂O flux from the soil between the canopies of tea plants for 2 years was 7.1 ± 0.9 kg N ha^?1 yr^?1 in control plots. The cumulative N₂O flux in the plots supplemented with lime nitrogen was 3.5 ± 0.1 kgN ha^?1, approximately 51% lower than that in control plots. This reduction was due to the inhibition of nitrification by DCD, which was produced from the lime nitrogen. In addition, the increase in soil pH by lime in the lime nitrogen may also be another reason for the decreased N₂O emissions from soil in LN plots. Meanwhile, the cumulative N₂O flux in DCD plots was not significantly different from that in control plots. The seasonal variability in N₂O emissions in DCD plots differed from that in control plots and application of DCD sometimes increased N₂O emissions from tea field soil. The nitrification inhibition effect of lime nitrogen and DCD helped to delay nitrification of ammonium-nitrogen (NH₄⁺-N), leading to high NH₄⁺-N concentrations and a high ratio of NH₄⁺-N /nitrate-nitrogen (NO₃^–-N) in the soil. The inhibitors delayed the formation of NO₃^–-N in soil. N uptake by tea plants was almost the same among all three treatments.