The influence of soluble carbon and fertilizer nitrogen on nitric oxide and nitrous oxide emissions from two contrasting agricultural soils

Contradictory effects of simultaneous available organic C and N sources on nitrous oxide (N₂O), carbon dioxide (CO₂) and nitric oxide (NO) fluxes are reported in the literature. In order to clarify this controversy, laboratory experiments were conduced on two different soils, a semiarid arable soil from Spain (soil I, pH=7.5, 0.8%C) and a grassland soil from Scotland (soil II, pH=5.5, 4.1%C). Soils were incubated at two different moisture contents, at a water filled pore space (WFPS) of 90% and 40%. Ammonium sulphate, added at rates equivalent to 200 and 50 kg N ha^?1, stimulated N₂O and NO emissions in both soils. Under wet conditions (90% WFPS), at high and low rates of N additions, cumulative N₂O emissions increased by 250.7 and 8.1 ng N₂O–N g^?1 in comparison to the control, respectively, in soil I and by 472.2 and 2.1 ng N₂O–N g^?1, respectively, in soil II. NO emissions only significantly increased in soil I at the high N application rate with and without glucose addition and at both 40% and 90% WFPS. In both soils additions of glucose together with the high N application rate (200 kg N ha^?1) reduced cumulative N₂O and NO emissions by 94% and 55% in soil I, and by 46% and 66% in soil II, respectively. These differences can be explained by differences in soil properties, including pH, soil mineral N and total and dissolved organic carbon content. It is speculated that nitrifier denitrification was the main source of NO and N₂O in the C-poor Spanish soil, and coupled nitrification–denitrification in the C-rich Scottish soil.     

Nitrogen fertilization of wheat residue affecting nitrous oxide and methane emission from a central Ohio Luvisol

Fertilization of wheat (Triticum aestivum, L.) residue applied to degraded soils has shown promise as an option to restoring soil organic C (SOC) stocks, but the impact of the practice on N2O and CH4 emissions is not clear. It was hypothesized that, in addition to the mulch-induced soil wetness conditions favorable for N2O and CH4 formation, emission of these gases will be stimulated due to increased availability of mineral N and interference of NH4⁺ with CH4 oxidation in soils. During the period February–November 2000, fluxes of N2O and CH4 were monitored in a plant-free central Ohio Crosby soil (fine, mixed, mesic Aeric Ochraqualf) amended for 4 years with wheat straw (bare, 0; low, 8 Mg ha^–1 year^–1; and high, 16 Mg ha^–1 year^–1) without and with N fertilization (244 kg N ha^–1). The average annual N2O fluxes were 1.1 kg N2O-N ha^–1 in the unfertilized and 4.1 kg N2O-N ha^–1 in the fertilized treatments. Annual N2O emission (Y, mg N2O-N m^–2) was strongly correlated to the maximum daily flux (X, mg N2O-N m^–2 day^–1; Y=48.3X−58.1, R²=0.85, P<0.001) recorded on experimental plots. These flux maxima occurred at spring thaw in the unfertilized, and 6–30 days after fertilization in the fertilized treatments. Net CH4 uptakes were measured on some occasions; overall, however, all the treatments were net CH4 emitters with annual rates of 3.6, 4.9 and 5.1 kg CH4-C ha^–1 in the bare, low and high residue treatments, respectively. No significant effect of fertilization and mulch rate on CH4 fluxes was found, but temperature and landscape position appeared as strong controllers. Regardless of treatments, the highest CH4-emitting plots were located in a minor depressional area at the experimental site. A comparison of SOC gain and N2O and CH4 emission expressed as CO2-equivalents indicates that the residue treatments have a net CO2-mitigating effect, but since C sequestration rates are expected to decrease with time, that positive effect will likely vanish after 7 and 12 more years in the fertilized and unfertilized residue treatments, respectively.     

Effects of various nitrogen fertilizers on emission of nitrous oxide from soils

Summary Field studies of the effects of different N fertilizers on emission of nitrous oxide (N20) from three Iowa soils showed that the N₂O emissions induced by application of 180 kg ha^–1 fertilizer N as anhydrous ammonia greatly exceeded those induced by application of the same amount of fertilizer N as aqueous ammonia or urea. On average, the emission of N₂O-N induced by anhydrous ammonia was more than 13 times that induced by aqueous ammonia or urea and represented 1.2% of the anhydrous ammonia N applied. Experiments with one soil showed that the N₂O emission induced by anhydrous ammonia was more than 17 times that induced by the same amount of N as calcium nitrate. These findings confirm indications from previous work that anhydrous ammonia has a much greater effect on emission of N₂O from soils than do other commonly used N fertilizers and merits special attention in research relating to the potential adverse climatic effect of N fertilization of soils.Laboratory studies of the effect of different amounts of NH₄OH on emission of N₂O from Webster soil showed that the emission of N₂O-N induced by addition of 100 g NH₄OH-N g^–1 soil represented only 0.18% of the N applied, whereas the emissions induced by additions of 500 and 1 000 g NH4OH-N g^–1 soil represented 1.15% and 1.19%, respectively, of the N applied. This suggests that the exceptionally large emissions of N₂O induced by anhydrous ammonia fertilization are due, at least in part, to the fact that the customary method of applying this fertilizer by injection into soil produces highly alkaline soil zones of high ammonium-N concentration that do not occur when urea or aqueous ammonia fertilizers are broadcast and incorporated into soil.     

Impact of nitrogen fertilization and tillage practices on nitrous oxide emission from a summer rice ecosystem

ABSTRACT

Identification of the combination of tillage and N fertilization practices that reduce agricultural Nitrous oxide (N₂O) emissions while maintaining productivity is strongly required in the Indian subcontinent. This study investigated the effects of tillage in combination with different levels of nitrogen fertilizer on N₂O emissions from a rice paddy for two consecutive seasons (2013–2014 and 2014–2015). The experiment consisted of two tillage practices, i.e., conventional (CT) and reduced tillage (RT), and four levels of nitrogen fertilizer, i.e., 0 kg N ha^–1 (F1), 45 kg N ha^–1 (F2), 60 kg N ha^–1 (F3) and 75 kg N ha^–1 (F4). Both tillage and fertilizer rate significantly affected cumulative N₂O emissions (p < 0.05). Fertilizer at 45 and 60 kg N ha^–1 in RT resulted in higher N₂O emissions over than did the CT. Compared with the recommended level of 60 kg N ha^?1, a 25% reduction in the fertilizer to 45 kg N ha^?1 in both CT and RT increased nitrogen use efficiency (NUE) and maintained grain yield, resulting in the lowest yield-scaled N₂O-N emission. The application of 45 kg N ha^?1 reduced the cumulative emission by 6.08% and 6% in CT and RT practices, respectively, without compromising productivity.     

Transformation of nitrogen and nitrous oxide emission from grassland soils as affected by compaction

Animal trampling is one of the main factors responsible for soil compaction under grazed pastures. Soil compaction is known to change the physical properties of the soil thereby affecting the transformation of nitrogen (N) and the subsequent of release of N as nitrous oxide (N₂O). The form of N source added to these compacted soils further affects N emissions. Here we determine the interactive effects of soil compaction and form of N sources (cattle urine and ammonium, nitrate and urea fertilizers) on the loss of N through N₂O emission from grassland soil. Overall, soil compaction caused a seven-fold increase in the N₂O flux, the total N₂O fluxes for the entire experimental period ranged from 2.62 to 61.74 kg N₂O-N ha⁻¹ for the compacted soil and 1.12 to 4.37 kg N₂O-N ha⁻¹ for the uncompacted soil. Among the N sources, the highest emissions were measured with nitrate application, emissions being 10 times more than those from other N sources for compacted soil, suggesting that the choice of N fertilizer can go a long way in mitigating N₂O emissions in compacted grasslands.     

Effects of rate and depth of fertilizer application on emission of nitrous oxide from soil fertilized with anhydrous ammonia

Summary Field studies to determine the effect of different rates of fertilization on emission of nitrous oxide (N₂O) from soil fertilized with anhydrous ammonia showed that the fertilizer-induced emission of N₂O-N in 116 days increased from 1.22 to 4.09 kg ha^–1 as the rate of anhydrous ammonia N application was increased from 75 to 450 kg ha^–1. When expressed as a percentage of the N applied, the fertilizer-induced emission of N₂O-N in 116 days decreased from 1.6% to 0.9% as the rate of fertilizer N application was increased from 75 to 450 kg N ha^–1. The data obtained showed that a 100% increase in the rate of application of anhydrous ammonia led to about a 60% increase in the fertilizer-induced emission of N₂O.Field studies to determine the effect of depth of fertilizer injection on emission of N₂O from soil fertilized with anhydrous ammonia showed that the emission of N₂O-N in 156 days induced by injection of 112 kg anhydrous ammonia N ha^–1 at a depth of 30 cm was 107% and 21 % greater than those induced by injection of the same amount of N at depths of 10 cm and 20 cm, respectively. The effect of depth of application of anhydrous ammonia on emission of N₂O was less when this fertilizer was applied at a rate of 225 kg N ha^–1.     

控释肥施用对小麦生长期N2O排放的影响

通过田间试验,采用静态箱法研究不同施氮水平下控释肥和尿素(N 0、100、200、270 kg hm-2)对麦季N2O排放的影响。结果表明,与对照相比,整个小麦生长季N2O排放量均随尿素和控释肥施用量的增加呈指数增加(32%～164%,p<0.05),但控释肥处理增加程度则较尿素处理缓和;施用控释肥可以有效抑制小麦生长季N2O排放(p<0.05),控释肥对N2O的减排量随着施氮量的增加而增加。小麦产量随尿素施用量的增加呈抛物线增加(24%～43%,p<0.05),随控释肥施用量的增加亦呈抛物线增加(30%～45%,p<0.05);与施用相同水平尿素相比,施用控释肥的小麦产量略有增加,但无显著差异(p>0.05)。单位产量N2O排放量随尿素施用量的增加而呈指数增加(31%～114%,p<0.05),随控释肥施用量的增加而呈抛物线增加(2%～50%,p<0.05);施用控释肥可以有效抑制小麦生长季单位产量N2O排放(p<0.05),控释肥对单位产量N2O的减排量随着施氮量的增加而增加。各处理N2O排放量与土壤水分存在显著正相关(p<0.05),与土壤NH4+-N、NO3--N浓度和土温不呈明显线性关系(p>0.05)。     

Interactive effects from combining fertilizer and organic residue inputs on nitrogen transformations

Concerns about sustainability of agroecosystems management options in developed and developing countries warrant improved understanding of N cycling. The Integrated Soil Fertility Management paradigm recognizes the possible interactive benefits of combining organic residues with mineral fertilizer inputs on agroecosystem functioning. However, these beneficial effects may be controlled by residue quality. This study examines the controls of inputs on N cycling across a gradient of (1) input, (2) residue quality, and (3) texture. We hypothesized that combining organic residue and mineral fertilizers would enhance potential N availability relative to either input alone. Residue and fertilizer inputs labeled with ¹⁵N (40–60 atom% ¹⁵N) were incubated with 200 g soil for 545 d in a microcosm experiment. Input treatments consisted of a no-input control, organic residues (3.65 g C kg⁻¹ soil, equivalent to 4 Mg C ha⁻¹), mineral N fertilizer (100 mg N kg⁻¹ soil, equivalent to 120 kg N ha⁻¹), and a combination of both with either the residue or fertilizer ¹⁵N-labeled. Zea mays stover inputs were added to four differently textured soils (sand, sandy loam, clay loam, and clay). Additionally, inputs of three residue quality classes (class I: Tithonia diversifolia, class II: Calliandra calothyrsus, class III: Z. mays stover) were applied to the clay soil. Available N and N₂O emissions were measured as indicators for potential plant N uptake and N losses. Combining residue and fertilizer inputs resulted in a significant (P < 0.05) negative interactive effect on total extractable mineral N in all soils. This interactive effect decreased the mineral N pool, due to an immobilization of fertilizer-derived N and was observed up to 181 d, but generally became non-significant after 545 d. The initial reduction in mineral N might lead to less N₂O losses. However, a texture effect on N₂O fluxes was observed, with a significant interactive effect of combining residue and fertilizer inputs decreasing N₂O losses in the coarse textured soils, but increasing N₂O losses in the fine textured soils. The interactive effect on mineral N of combining fertilizer with residue changed from negative to positive with increasing residue quality. Our results indicate that combining fertilizer with medium quality residue has the potential to change N transformations through a negative interactive effect on mineral N. We conclude that capitalizing on interactions between fertilizer and organic residues allows for the development of sustainable nutrient management practices.     

不同施肥处理稻田甲烷和氧化亚氮排放特征

采用静态箱－气相色谱法对长期不同施肥处理(NPKS、CK、NPK和NKM)的稻田CH₄和N₂O排放进行了观测。结果表明,稻田CH₄和N₂O排放季节变化规律明显不同,二者排放通量季节变化呈显著负相关(p<0.01)。与单施化肥和CK相比,施用有机肥显著促进CH₄排放,排放量最高的NPKS处理早晚稻田排放量分别是：526.68 kg/hm²和1072.92 kg/hm²。对于N₂O排放,早稻田各处理间差异不显著,NPK处理排放量最大,为1.48 kg/hm²;晚稻田各处理差异极显著(p<0.01),NPKS处理排放量最大,为1.40 kg/hm²。晚稻田CH₄排放通量和10 cm土层温度及土壤pH值相关极显著(p<0.01),并与二者存在显著的指数关系。没发现N₂O排放通量与温度及pH值间存在显著相关。稻田CH₄和N₂O排放受多种因素影响,但对全球变暖的贡献率CH₄远大于N₂O。NPKS处理的增温潜势最大,NPK处理的最小。     

Effect of nitrite accumulation on nitrous oxide emission and total nitrogen loss during swine manure composting

Abstract

The present study investigated the nitrogen balance in swine manure composting to evaluate the effect of nitrite (NO^? ₂) accumulation, which induces nitrogenous emissions, such as N₂O, during compost maturation. During active composting, most N losses result from NH₃ emission, which was 9.5% of the initial total nitrogen (TN_initial), after which, NO^? ₂ began to accumulate as only ammonia-oxidizing bacteria proliferated. After active composting, the addition of mature swine compost (MSC), including nitrite-oxidizing bacteria (NOB), could prevent NO^? ₂ accumulation and reduce N₂O emission by 70% compared with the control in which NO^? ₂ accumulated as a result of delayed growth of indigenous NOB. Total N₂O emissions in the control and in the treatment of MSC addition (MA) were 9.3% and 3.0% of TN_initial, respectively, whereas N losses as the sum total of NH₃ and N₂O over the whole period were 19.0% (control) and 12.8% (MA) of TN_initial, respectively. However, the difference in total N losses was markedly greater than that measured as NH₃ and N₂O, which were 27.8% (control) and 13.3% (MA) of TN_initial, respectively. These results demonstrated that the magnitude of nitrogen losses induced by NO^? ₂ accumulation is too large to ignore in the composting of swine manure.     

Effect of nitrite accumulation on nitrous oxide emission and total nitrogen loss during swine manure composting

The present study investigated the nitrogen balance in swine manure composting to evaluate the effect of nitrite (     ) accumulation, which induces nitrogenous emissions, such as N₂O, during compost maturation. During active composting, most N losses result from NH₃ emission, which was 9.5% of the initial total nitrogen (TN_initial), after which,     began to accumulate as only ammonia-oxidizing bacteria proliferated. After active composting, the addition of mature swine compost (MSC), including nitrite-oxidizing bacteria (NOB), could prevent     accumulation and reduce N₂O emission by 70% compared with the control in which     accumulated as a result of delayed growth of indigenous NOB. Total N₂O emissions in the control and in the treatment of MSC addition (MA) were 9.3% and 3.0% of TN_initial, respectively, whereas N losses as the sum total of NH₃ and N₂O over the whole period were 19.0% (control) and 12.8% (MA) of TN_initial, respectively. However, the difference in total N losses was markedly greater than that measured as NH₃ and N₂O, which were 27.8% (control) and 13.3% (MA) of TN_initial, respectively. These results demonstrated that the magnitude of nitrogen losses induced by     accumulation is too large to ignore in the composting of swine manure.     

Rates of decomposition and phosphorus release from organic residues related to residue composition

The use of organic residues might be appropriate in maintaining long‐term P requirement of crops. Eight plant residues and two manures in a wide range of C : N ratios were incubated for 12 weeks at 25°C, during which the processes of decomposition and formation of acid‐extractable P (P release) were assessed. Residues were incubated moist in bags and inoculated with a soil suspension. The exponential model was found to be suitable to describe decomposition and P‐release rates from residues. There were two distinct parts of P release in each time curve, which gave two rate constants and were calculated as the slope of each part. The rates of P release of the residues were considerably higher during the first 4 weeks of incubation than during the second phase of incubation (weeks 5–12). Phosphorus release by residues was similar to the decomposition pattern. The residue P content was correlated with P release, but not with decomposition rate. Mass loss and release of P were greater from sunflower and wheat residues than from sheep manure, suggesting that a high C : N ratio does not necessarily retard decomposition. The model parameters of P release were derived which are suitable to estimate the P‐fertilizer effect of organic residues. Our results suggest that the use of organic residues as a source for short‐ and long‐term P supply for crops should be encouraged.     

Nitrous oxide emission from soils after incorporating crop residues

Abstract. Emissions of N₂O were measured from different agricultural systems in SE Scotland. N₂O emissions increased temporarily after fertilization of arable crops, cultivation of bare soil, ploughing up of grassland and incorporation of arable and horticultural crop residues, but the effect was short-lived. Most of the emission occurred during the first two weeks, returning to 'background' levels after 30–40 days. The highest flux was from N-rich lettuce residues, 1100 g N₂O-N ha⁻¹ being emitted over the first 14 days after incorporation by rotary tillage. The magnitude and pattern of emissions was strongly influenced by rainfall, soil mineral N, cultivation technique and C:N ratio of the residue. Comparatively large emissions were measured after incorporation of material with low C:N ratios. Management practices are recommended that would increase N-use efficiency and reduce N₂O emissions from agricultural soils.     

Relationship between nitrous oxide emission and winter wheat production

A 3-year field study in southeast China was performed to examine the relationship between N₂O emission and winter wheat production. Over the 2002–03, 2003–04 and 2004–05 wheat-cropping seasons, N₂O emissions depended on nitrogen addition, plowing practice, and preceding crop type treatments, and showed a pronounced inter-annual variation. N₂O–N emission factor, the proportion of fertilizer N released as N₂O–N from the wheat field, varied from 1.33% to 2.97%. The relationship between N₂O emission (y) and crop yield (x) was well explained by the function y = 3.773Ln(x) + 1.46. Similarly, the function y = 4.445Ln(x) − 3.52 can be employed to address the relationship between N₂O emission (y) and above ground biomass (x). About 84% and 87% of variation in seasonal N₂O emission were explained by the two functions, while only 66% of the variation was represented by the N input with a linear relationship. The results of this study suggest that seasonal N₂O emission of soil under winter wheat could be better predicted by crop yield and biomass than by N input. Submitted to Biology and Fertility of Soils.     

Effect of nitrogen fertilization, cropping and irrigation on soil air composition and nitrous oxide emission in a loamy clay

Most of the nitrous oxide (N₂O) in the atmosphere, thought to be involved in global warming, is emitted from soil. Although the main factors controlling the production of N₂O in soil are well known, we need more quantitative data on the interactions of soil and the environment in the soil that affect the emission. We therefore studied the effects of irrigation, cropping (fallow, barley with grass undersown) and N fertilization (unfertilized, 103 kg N ha^?1) on the composition of soil air and direct N₂O emission from soil (using the closed chamber method) in a factorial field experiment on a well‐structured loamy clay soil during 1 June?22 October 1993. The measurements were made weekly during the growing season and three times after harvesting. The composition of the soil air did not indicate severe anoxia in any treatment or combination of treatments, but the accumulation of N₂O in the soil air indicated that hypoxia was common. At the start of the irrigation the emissions were small, even though there was much ammonium and nitrate in the soil and therefore a potential for emission of N₂O produced by both nitrification and denitrification. Larger emissions occurred later. The largest emissions were found when 60–90% of the soil pore space was filled with water. Irrigation and fertilization with N both roughly doubled the cumulative N₂O emission. Growing a crop decreased it by a factor of 3–7. Most N₂O was lost from the irrigated fertilized soil under fallow (3.5 kg N ha^?1), and least from the unirrigated unfertilized soil under barley (0.1 kg N ha^?1).     

Combined nitrogen input from legume residues and fertilizer improves early nitrogen supply and uptake by wheat

Soil nitrogen (N) supply for wheat N uptake can be manipulated through legume and fertilizer N inputs to achieve yield potential in low‐rainfall sandy soil environments. Field experiments over 2 years (2015–2016) were conducted at 2 different sites in a low‐rainfall sandy soil to determine the soil N supply capacity relative to wheat N uptake at key growth stages, after a combination of crop residue (removed, wheat or lupin) and fertilizer N (nil, low or high N) treatments were manipulated to improve wheat yield. We measured the temporal patterns of the soil profile mineral N and PAW to 100 cm depth, wheat aerial biomass and N uptake in both years. In 2016 we also measured the disease incidence as a key environmental variable. There was 35 kg ha^?1 more soil mineral N to 100 cm depth following lupin than wheat residues at the end of the fallow on average in both years. In a below average rainfall season, wheat biomass produced on lupin residues was responsive to N input with soil profile mineral N depleted by increased crop N uptake early in the season. In an above average rainfall season, a higher soil mineral N supply increased actual and potential grain yield, total biomass, N uptake, harvest index and water use efficiency of wheat, regardless of the source of N. Our study showed that the combination of lupin residues with high N rate increased soil profile mineral N at early growth stages, providing a greater soil N supply at the time of high wheat N demand, and the inclusion of a legume in the rotation is critical for improving the N supply to wheat, with added disease break benefits in a low‐rainfall sandy soil environment.     

菜地氮肥用量与N2O排放的关系及硝化抑制剂效果

通过连续种植四季蔬菜近一年的大田试验,探究高施氮水平和低氮肥利用率的蔬菜生产系统中,N2O排放量与氮肥施用量之间的定量关系及其机理,并研究硝化抑制剂减少菜地N2O排放的效果.结果表明,在氮肥施用水平为N 0～1 733 kg hm-2a-1间,无论氮肥中是否添加硝化抑制剂,N2O总排放量与氮肥施用量均呈指数函数关系,即氮肥施用量高时,N2O排放率也高.在各氮肥水平处理下,硝化抑制剂均能降低N2O排放,抑制率为8.75％ ～ 25.28％,且这种减排效果随着施氮量增加而增加.在氮肥施用量为N 300或400 kg hm-2季-1时,施用硝化抑制剂减少N2O排放所带来的效益略高于其成本,因此,即使不考虑氮肥利用率的提高等因素,施用硝化抑制剂仍是一种有利的选择.