Effect of carbon rate and type amended with ammonium or nitrate on nitrous oxide emissions in a strong ammonia oxidation soil

Journal of Soils and Sediments - The work aimed to (1) better understand how C rate and type affecting N2O emissions when combined application with different N forms in a strong ammonia oxidation...     

Distinct effect of nitrogen fertilisation and soil depth on nitrous oxide emissions and nitrifiers and denitrifiers abundance

The nitrous oxide and molecular N emissions from 5-cm length subsamples taken from 20-cm length sample corers containing eutric Cambisol soil fertilised either with urea, ammonium or nitrate for 1 year have been examined using gas chromatography. At the beginning of the incubation, the same N rate (260 kg N/ha) was added to the soil and kept constant during the experiment. The total abundance of the soil Bacteria and Archaea and that of nitrifiers and denitrifiers was estimated by quantitative PCR of the corresponding biotic variables 16S rRNA, amoA and napA, narG, nirK, nirS, norB, nosZI and nosZII genes. The abiotic variables dissolved oxygen, pH, exchangeable NH₄⁺-N and NO₃^?-N contents and total C and total N were also analysed. None of the three fertilisers affected the total abundance of Bacteria and Archaea and nitrification was the main driver of nitrous oxide production in the 0- to 5-cm and 5- to 10-cm soil layers while denitrification was in the 10- to 15-cm and 15- to 20-cm soil horizons. Parallel to the reduction in the content of dissolved oxygen along the soil profile, there was a decrease in the total and relative abundance of the bacterial and archaeal amoA gene and an increase in the abundances of the denitrification genes, mainly in the 10- to 15-cm and 15- to 20-cm soil layers. A non-metric multidimensional scaling plot comparing the biotic and abiotic variables examined in each of the four 5-cm soil subsamples and the whole 20-cm sample showed a disparate effect of N fertilisation on N gas emissions and abundance of nitrifiers and denitrifiers bacterial and archaeal communities.     

Nitrifier dominance of Arctic soil nitrous oxide emissions arises due to fungal competition with denitrifiers for nitrate

Arctic soils emit nitrous oxide, which is a potent greenhouse gas and also represents an important loss of nitrogen to oligotrophic Arctic ecosystems. However, little is known about the temperature sensitivity of nitrous oxide release in Arctic soils or the organisms mainly responsible for it. We investigated controls on nitrous oxide emissions in an Arctic soil across a typical temperature range (between 4 and 13 °C) on Truelove Lowland, Devon Island, Canada (75°40′N 84°35′W) at two different moisture contents. When fertilized with ammonia or nitrate, nitrous oxide emissions and temperature dependence of nitrous oxide emissions were insensitive to soil moisture content but linked to nitrification rates. Stable isotope analysis revealed that nitrous oxide was predominantly released by nitrifiers. However, nitrous oxide emissions were not linked to nitrifier prevalence with an insignificant (P < 0.219) increase in amoA genes and a (P < 0.01) decrease in archaeal nitrifiers. In contrast, denitrifier nosZ prevalence was 10,000 times greater than that of nitrifiers and was related to nitrous oxide emission potential when soils were fertilized with nitrate. Manipulating water-filled pore space should have changed the pattern of N₂O emissions. We used selective inhibitors to further explore why denitrification did not occur under field conditions when we manipulated water-filled pore space or when we used ¹⁵N analysis. When fungi were inhibited in the soil, nitrous oxide emissions from denitrifiers increased with no change in nitrous oxide released by nitrifiers. When fungi were active in the soil, there was little available nitrate but when fungi were inhibited, available soil nitrate increased over the incubation period. The dominance of nitrifiers in nitrous oxide emissions from Arctic soils under field conditions is linked to the competition for nitrate between fungi and denitrifiers.     

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.     

Effect of plantain on nitrous oxide emissions and soil nitrification rate in pasture soil under a simulated urine patch in Canterbury,New Zealand

Purpose

The aim of this research was to quantify the effect of plantain (Plantago lanceolata L.) on soil nitrification rate, functional gene abundance of soil ammonia oxidisers, and the concomitant effect on nitrous oxide emissions from urine patches in a shallow, free-draining soil in Canterbury during late autumn/winter season.

Materials and methods

Urine was collected from dairy cows grazing either ryegrass/white clover (RGWC), 30% plantain (P30) mixed in with RGWC or 100% plantain (P100) pasture, and applied at two rates (700 or 450 kg N ha^?1) to intact soil blocks growing either RGWC, P30 or P100 pasture.

Results and discussion

Results showed that increased plantain content reduced N-concentration in urine from 7.2 in RGWC urine to 4.5 and 3.7 g N L^?1 in P30 and P100 urine, respectively. Total N₂O emissions and emission factors (EF₃) from urine-treated pastures were low, <?2 kg N ha^?1 and <?0.22%, respectively. Urine application at the lower urine N-loading rate of 450 kg N ha^?1 (i.e. representative of that in a P30 urine patch) resulted in 30% lower N₂O emissions (P?<?0.01) and 35% lower soil nitrate concentrations (P?<?0.001) compared to those at the higher urine loading rate of 700 kg N ha^?1 (i.e. representative of that in a RGWC urine patch). Increasing plantain content in the pasture sward from 0 to 30% and 100% with urine N applied at the same loading rate did not reduce N₂O emissions or nitrification compared to the standard ryegrass-white clover pasture. Cow urine derived from the different pasture diets had no effect on N₂O emissions, N transformation or ammonia-oxidiser abundance in soil compared to the RGWC urine applied at the same rate.

Conclusions

The main effect of plantain in this study appears to be related to the reduction in urine N-loading rate, rather than factors related to urine properties or plantain-soil interactions.

     

追氮方式对夏玉米土壤N2O和NH3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NH4+-N、 NO2--N和NO3--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N 22.9 kg/hm2,同时还导致土壤在一定程度上积累了NO2--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NO2--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NO2--N累积。条施覆土的施肥条带上土壤NO2--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,020 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NO2--N的累积与铵态氮肥施肥方式密切相关,NO2--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(P0.05)。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。     

The effect of soil texture and soil drainage on emissions of nitric oxide and nitrous oxide

Abstract. Agricultural soils are important sources of the tropospheric ozone precursor NO and the greenhouse gas N₂O. Emissions are controlled primarily by parameters that vary the soil mineral N supply, temperature and soil aeration. In this field experiment, the importance of soil physical properties on emissions of NO and N₂O are identified. Fluxes were measured from 13 soils which belonged to 11 different soil series, ranging from poorly drained silty clay loams to freely drained sandy loams. All soils were under the same soil management regime and crop type (winter barley) and in the same maritime climate zone. Despite this, emissions of NO and N₂O ranged over two orders of magnitude on all three measurement occasions, in spring before and after fertilizer application, and in autumn after harvest. NO emissions ranged from 0.3 to 215 μg NO-N m^–2 h^–1, with maximum emissions always from the most sandy, freely drained soil. Nitrous oxide emissions ranged from 0 to 193 μg N₂O-N m^–2 h^–1. Seasonal shifts in soil aeration caused maximum N₂O emissions to switch from freely drained sandy soils in spring to imperfectly drained soils with high clay contents in autumn. Although effects of soil type on emissions were not consistent, N₂O emission was best related to a combination of bulk density and clay content and the NO/N₂O ratio decreased logarithmically with increasing water filled pore space.     

Modelling soil compaction impacts on nitrous oxide emissions in arable fields

Nitrous oxide (N₂O) emissions comprise the major share of agriculture's contribution to greenhouse gases; however, our understanding of what is actually happening in the field remains incomplete, especially concerning the multiple interactions between agricultural practices and N₂O emissions. Soil compaction induces major changes in the soil structure and the key variables controlling N₂O emissions. Our objective was to analyse the ability of a process‐based model (Nitrous Oxide Emissions (NOE)) to simulate the impact of soil compaction on N₂O emission kinetics obtained from field experiments. We used automatic chambers to continuously monitor N₂O and CO₂ emissions on uncompacted and compacted areas in sugar beet fields during 2 years. Soil compaction led to smaller CO₂ emissions and larger N₂O emissions by inducing anoxic conditions favourable for denitrification. Cumulative N₂O emissions during the crop cycles were 944 and 977 g N ha⁻¹ in uncompacted plots and 1448 and 1382 g N ha⁻¹ in compacted plots in 2007 and 2008, respectively. The NOE model ( Hénault et al., 2005 ) simulated 106 and 138 g N₂O‐N ha⁻¹ in uncompacted plots and 1550 and 650 g N₂O‐N ha⁻¹ in compacted plots in 2007 and 2008, respectively, markedly under‐estimating the nitrification rates and associated N₂O emissions. We modified the model on the basis of published results in order to better simulate nitrification and account for varying N₂O fractions of total end‐products in response to varying soil water and nitrate contents. The modified model (NOE2) better predicted nitrification rates and N₂O emissions following fertilizer addition. Using a fine vertical separation of soil layers of configurable, but constant, thickness (1 cm) also improved the simulations. NOE2 predicted 428 and 416 g N‐N₂O ha⁻¹ in uncompacted plots and 1559 and 1032 g N‐ N₂O ha⁻¹ in compacted plots in 2007 and 2008, respectively. These results show that a simple process‐based model can be used to predict successfully the post‐fertilizer addition kinetics of N₂O emissions and the impact of soil compaction on these emissions. However, large emissions later on during the cropping cycle were not captured by the model, emphasizing the need for further research.     

Effects of trampling of a wet dairy pasture soil on soil porosity and on mitigation of nitrous oxide emissions by a nitrification inhibitor,dicyandiamide

Urine patches in dairy pastures are major sources of nitrous oxide (N₂O). Wet winters result in compaction damage to pastures because of animal trampling. The nitrification inhibitor, dicyandiamide (DCD), is effective at reducing N₂O emissions from urine patches. Here, we assessed the extent of damage to the physical quality of the soil by trampling and whether this influenced the ability of DCD to mitigate N₂O emissions. A field experiment was conducted where a sandy loam soil was trampled by a mechanical hoof just before urine and DCD application. Trampling reduced air permeability and pore continuity, but this had no effect on bulk density. Urine appeared to have contributed to pore collapse and blockage. Trampling increased average cumulative N₂O emissions from 1.74 to 4.66% of urine‐N applied. This effect was attributed to increased water‐filled pore space, aggregate destruction and suppression of grass growth. DCD was highly effective in reducing N₂O emissions, with the N₂O emission factor of the urine‐N being decreased by 58–63%. Trampling did not significantly affect the effectiveness of DCD in reducing N₂O emissions.     

Linkage of N2O emissions to the abundance of soil ammonia oxidizers and denitrifiers in purple soil under long-term fertilization

Abstract

Microbial nitrification and denitrification are responsible for the majority of soil nitrous (N₂O) emissions. In this study, N₂O emissions were measured and the abundance of ammonium oxidizers and denitrifiers were quantified in purple soil in a long-term fertilization experiment to explore their relationships. The average N₂O fluxes and abundance of the amoAgene in ammonia-oxidizing bacteria during the observed dry season were highest when treated with mixed nitrogen, phosphorus and potassium fertilizer (NPK) and a single N treatment (N) using NH₄HCO₃as the sole N source; lower values were obtained using organic manure with pig slurry and added NPK at a ratio of 40%:60% (OMNPK),organic manure with pig slurry (OM) and returning crop straw residue plus synthetic NH₄HCO₃fertilizer at a ratio of 15%:85% (SRNPK). The lowest N₂O fluxes were observed in the treatment that used crop straw residue(SR) and in the control with no fertilizer (CK). Soil NH₄⁺provides the substrate for nitrification generating N₂O as a byproduct. The N₂O flux was significantly correlated with the abundance of the amoA gene in ammonia-oxidizing bacteria (r = 0.984, p < 0.001), which was the main driver of nitrification. During the wet season, soil nitrate (NO₃^?) and soil organic matter (SOC) were found positively correlated with N₂O emissions (r = 0.774, p = 0.041 and r = 0.827, p = 0.015, respectively). The nirS gene showed a similar trend with N₂O fluxes. These results show the relationship between the abundance of soil microbes and N₂O emissions and suggest that N₂O emissions during the dry season were due to nitrification, whereas in wet season, denitrification might dominate N₂O emission.     

Effect of dairy manure type and supplemental synthetic fertilizer on methane and nitrous oxide emissions from a grassland in Nasu,Japan

Abstract

It is well known that some fungal species are remarkably tolerant of high copper concentration, although copper is toxic to most fungi (Garraway and Evans 1984). Bedford (1936) and Jurkowska (1952) reported that Penicillium and Aspergillus species can grow in liquid media saturated or nearly saturated with copper sulfate. Okamoto and Fuwa (1974) isolated Penicillium ochro-chloron from the laboratory air, and found that the fungus was able to grow in a medium saturated with copper sulfate.     

Nitrogen and carbon addition changed nitrous oxide emissions from soil aggregates in straw-incorporated soil

Journal of Soils and Sediments - The effects of straw incorporation on soil nitrous oxide (N2O) emission at the soil aggregate scale have yet to be elucidated, especially with supplemental nitrogen...     

Effect of biochar and nitrapyrin on nitrous oxide and nitric oxide emissions from a sandy loam soil cropped to maize

A field experiment was conducted to evaluate the combined or individual effects of biochar and nitrapyrin (a nitrification inhibitor) on N₂O and NO emissions from a sandy loam soil cropped to maize. The study included nine treatments: addition of urea alone or combined with nitrapyrin to soils that had been amended with biochar at 0, 3, 6, and 12 t ha^?1 in the preceding year, and a control without the addition of N fertilizer. Peaks in N₂O and NO flux occurred simultaneously following fertilizer application and intense rainfall events, and the peak of NO flux was much higher than that of N₂O following application of basal fertilizer. Mean emission ratios of NO/N₂O ranged from 1.11 to 1.72, suggesting that N₂O was primarily derived from nitrification. Cumulative N₂O and NO emissions were 1.00 kg N₂O-N ha^?1 and 1.39 kg NO-N ha^?1 in the N treatment, respectively, decreasing to 0.81–0.85 kg N₂O-N ha^?1 and 1.31–1.35 kg NO-N ha^?1 in the biochar amended soils, respectively, while there was no significant difference among the treatments. NO emissions were significantly lower in the nitrapyrin treatments than in the N fertilization-alone treatments (P?<?0.05), but there was no effect on N₂O emissions. Neither biochar nor nitrapyrin amendment affected maize yield or N uptake. Overall, our results showed that biochar amendment in the preceding year had little effect on N₂O and NO emissions in the following year, while the nitrapyrin decreased NO, but not N₂O emissions, probably due to suppression of denitrification caused by the low soil moisture content.     

The influence of winter soil cover on spring nitrous oxide emissions from an agricultural soil

In temperate regions, a majority of N₂O is emitted during spring soil thawing. We examined the influence of two winter field covers, snow and winter rye, on soil temperature and subsequent spring N₂O emissions from a New York corn field over two years. The first season (2006-07) was a cold winter (2309 h below 0 °C at 8 cm soil depth), historically typical for the region. The snow removal treatment resulted in colder soils and higher N₂O fluxes (73.3 vs. 57.9 ng N₂O-N cm⁻² h⁻¹). The rye cover had no effect on N₂O emissions. The second season (2007-08) was a much milder winter (1271 h below freezing at 8 cm soil depth), with lower N₂O fluxes overall. The winter rye cover resulted in lower N₂O fluxes (5.9 vs. 33.7 ng N₂O-N cm⁻² h⁻¹), but snow removal had no effect. Climate scenarios predict warmer temperature and less snow cover in the region. Under these conditions, spring N₂O emissions can be expected to decrease and could be further reduced by winter rye crops.     

Simulated animal trampling of a free‐draining stony soil stimulated denitrifier growth and increased nitrous oxide emissions

Winter forage grazing systems in New Zealand cause compaction of soil by grazing animals, especially when the soil is wet. However, there is little information on the effects of animal trampling on denitrifiers in soil, despite their importance for N₂O production. Here, we report a field study of the abundance of the denitrifying genes nirS, nirK, and nosZ and N₂O emissions following the application of dairy cow urine in a free‐draining stony soil. Importantly, we found that simulated animal trampling altered some of the denitrifying microbial communities, thus leading to increased N₂O emissions. Over the 111 day measurement period, the abundance of nitrite (NO₂^?)‐reducing nirS gene copy numbers increased significantly by 87% in the trampled soil with urine (P < 0.01) and increased by 40% in the trampled soil without urine (P < 0.05), but the nirS gene abundance did not change significantly in the nontrampled soil. The abundance of NO₂^? reducing nirK gene copy numbers was not affected by trampling, but increased significantly following urine application. The abundance of N₂O‐reducing nosZ clade I and nosZ clade II gene copy numbers increased significantly in the trampled soil, but did not change significantly in the nontrampled soil. N₂O emissions from the trampled soil were about twice that from the nontrampled soil without urine (1.20 and 0.62 kg N₂O‐N per ha, respectively) and about eight times greater (6.24 kg N₂O‐N per ha) than from nontrampled soil (0.80 kg N₂O‐N per ha) when urine was applied. These results strongly suggest that animal trampling during winter forage grazing can have a major impact on denitrifying communities in soil, which in turn stimulate greater denitrification with increased N₂O emissions.     

Mitigation of nitrous oxide emissions in spray-irrigated grazed grassland by treating the soil with dicyandiamide, a nitrification inhibitor

Abstract. Nitrous oxide (N₂O) from animal excreta in grazed pasture systems makes up a significant component (c. 10%) of New Zealand's total greenhouse gas inventory. We report an effective method to decrease N₂O emissions from animal urine patches by treating the soil with the nitrification inhibitor dicyandiamide (DCD), in a simulated grazed dairy pasture system under spray 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 ). By treating the soil with DCD, N₂O emissions were decreased by 76% following urine application in the autumn, from 26.7 kg N₂O-N ha⁻¹ without DCD to an average of 6.4 kg N₂O-N ha⁻¹ with DCD over the 6-month experimental period. N₂O flux was decreased by 78% following urine application in the spring, from 18 kg N₂O-N ha⁻¹ without DCD to 3.9 kg N₂O-N ha⁻¹ with the application of DCD over the 3-month period. A single application of DCD immediately after urine was sufficient to effectively mitigate N₂O emissions from the urine. The results showed that repeated applications of DCD after urine application, or mixing DCD with urine, offered no advantage over a single application of DCD immediately after urine deposition.     

Effect of urease and nitrification inhibitors on N transformation, gaseous emissions of ammonia and nitrous oxide, pasture yield and N uptake in grazed pasture system

Nitrogen (N) losses via nitrate (NO₃⁻) leaching, ammonia (NH₃) volatilization and nitrous oxide (N₂O) emissions from grazed pastures in New Zealand are one of the major contributors to environmental degradation. The use of N inhibitors (urease and nitrification inhibitors) may have a role in mitigating these N losses. A one-year field experiment was conducted on a permanent dairy-grazed pasture site at Massey University, Palmerston North, New Zealand to quantify these N losses and to assess the effect of N inhibitors in reducing such losses during May 2005-2006. Cow urine at 600 kg N ha⁻¹ rate with or without urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) or (trade name “Agrotain”) (3 L ha⁻¹), nitrification inhibitor dicyandiamide (DCD) (7 kg ha⁻¹) and the use of double inhibitor (DI) containing a combination of both Agrotain and DCD (3:7) were applied to field plots in autumn, spring and summer. Pasture production, NH₃ and N₂O fluxes, soil mineral N concentrations, microbial biomass C and N, and soil pH were measured following the application of treatments during each season. All measured parameters, except soil microbial biomass C and N, were influenced by the added inhibitors during the three seasons. Agrotain reduced NH₃ emissions over urine alone by 29%, 93% and 31% in autumn, spring and summer respectively but had little effect on N₂O emission. DCD reduced N₂O emission over urine alone by 52%, 39% and 16% in autumn, spring and summer respectively but increased NH₃ emission by 56%, 9% and 17% over urine alone during those three seasons. The double inhibitor reduced NH₃ by 14%, 78% and 9% and N₂O emissions by 37%, 67% and 28% over urine alone in autumn, spring and summer respectively. The double inhibitor also increased pasture dry matter by 10%, 11% and 8% and N uptake by the 17%, 28% and 10% over urine alone during autumn, spring and summer respectively. Changes in soil mineral N and pH suggested a delay in urine-N hydrolysis with Agrotain, and reduced nitrification with DCD. The combination of Agrotain and DCD was more effective in reducing both NH₃ and N₂O emissions, improving pasture production, controlling urea hydrolysis and retaining N in NH₄⁺ form. These results suggest that the combination of both urease and nitrification inhibitors may have the most potential to reduce N losses if losses are associated with urine and improve pasture production in intensively grazed systems.     

Nitrous oxide emissions from grassland in an intensive dairy farm in the Basque Country of Spain

Abstract. Intensively managed grasslands are potentially a large source of N₂O in the North Coast of Spain because of the large N input, the wet soil conditions and mild temperatures. To quantify the effect of fertilizer type and management practices carried out by farmers in this area, field N₂O losses were measured over a year using the closed chamber technique. Plots received two types of fertilizer: cattle slurry (536 kg N ha^–1) and calcium ammonium nitrate (140 kg N ha^–1). N₂O losses were less in the slurry treatment than after mineral fertilizer. This was probably due to high, short‐lived peaks of N₂O encountered immediately following mineral N addition. In contrast, the seasonal distribution of N₂O losses from the slurry amended plot was more uniform over the year. The greater N₂O losses in the mineral treatment might have been enhanced by the combined effect of mineral fertilizer and past organic residues present from previous organic amendments. Weak relationships were found between N₂O emission rates and soil nitrate, soil ammonium, soil water content and temperature. Better relationships were obtained in the mineral treatment than in the slurry plots, because of the wider range in soil mineral N. Water filled pore space (WFPS) was a key factor controlling N₂O emissions. In the > 90% WFPS range no relationships were found. The best regressions were found for the mineral treatment in the 40–65% WFPS range, 49% of the variance being explained by soil nitrate and ammonium content. In the 65–90% WFPS range, 43% of the variance was explained by nitrate only, but the inclusion of soil ammonium did not improve the model as it did in the 40–65% WFPS range. This fact indicates that nitrification is likely to be an important process involved in N₂O emissions at the 40–65% WFPS.