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.     

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.     

N2O emissions from an irrigated and non‐irrigated organic soil in eastern Canada as influenced by N fertilizer addition

Drainage and cultivation of organic soils often result in large nitrous oxide (N₂O) emissions. The objective of this study was to assess the impacts of nitrogen (N) fertilizer on N₂O emissions from a cultivated organic soil located south of Montréal, QC, Canada, drained in 1930 and used since then for vegetable production. Fluxes of N₂O were measured weekly from May 2004 to November 2005 when snow cover was absent in irrigated and non‐irrigated plots receiving 0, 100 or 150 kg N ha⁻¹ as NH₄NO₃. Soil mineral N content, gas concentrations, temperature, water table height and water content were also measured to help explain variations in N₂O emissions. Annual emissions during the experiment were large, ranging from 3.6 to 40.2 kg N₂O‐N ha⁻¹ year⁻¹. The N₂O emissions were decreased by N fertilizer addition in the non‐irrigated site but not in the irrigated site. The absence of a positive influence of soil mineral N content on N₂O emissions was probably in part because up to 571 kg N ha⁻¹ were mineralized during the snow‐free season. Emissions of N₂O were positively correlated to soil CO₂ emissions and to variables associated with the extent of soil aeration such as soil oxygen concentration, precipitation and soil water table height, thereby indicating that soil moisture/aeration and carbon bioavailability were the main controls of N₂O emission. The large N₂O emissions observed in this study indicate that drained cultivated organic soils in eastern Canada have a potential for N₂O‐N losses similar to, or greater than, organic soils located in northern Europe.     

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.     

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.     

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.     

N2O fluxes from a Haplic Luvisol under intensive production of lettuce and cauliflower as affected by different N‐fertilization strategies

Vegetable‐production systems often show high soil mineral‐N contents and, thus, are potential sources for the release of the climate‐relevant trace gas N₂O from soils. Despite numerous investigations on N₂O fluxes, information on the impact of vegetable‐production systems on N₂O emissions in regions with winter frost is still rare. This present study aimed at measuring the annual N₂O emissions and the total yield of a lettuce–cauliflower rotation at different fertilization rates on a Haplic Luvisol in a region exposed to winter frost (S Germany). We measured N₂O emissions from plots fertilized with 0, 319, 401, and 528 kg N ha^–1 (where the latter three amounts represented a strongly reduced N‐fertilization strategy, a target value system [TVS] in Germany, and the N amount fertilized under good agricultural practices). The N₂O release from the treatments was 2.3, 5.7, 8.8, and 10.6 kg N₂O‐N ha^–1 y^–1, respectively. The corresponding emission factors calculated on the basis of the total N input ranged between 1.3% and 1.6%. Winter emission accounted for 45% of the annual emissions, and a major part occurred after the incorporation of cauliflower residues. The annual N₂O emission was positively correlated with the nitrate content of the top soil (0–25 cm) and with the N surpluses of the N balance. Reducing the amount of N fertilizer applied significantly reduced N₂O fluxes. Since there was no significant effect on yields if fertilization was reduced from 528 kg N ha^–1 according to “good agricultural practice” to 401 kg N ha^–1 determined by the TVS, we recommend this optimized fertilization strategy.     

Effect of mineral nitrogen fertilizer forms on N2O emissions from arable soils in winter wheat production

Nitrogen fertilizers are supposed to be a major source of nitrous oxide (N₂O) emissions from arable soils. The objective of this study was to compare the effect of N forms on N₂O emissions from arable fields cropped with winter wheat (Triticum aestivum L.). In three field trials in North‐West Germany (two trials in 2011/2012, one trial in 2012/2013), direct N₂O emissions during a one‐year measurement period, starting after application of either urea, ammonium sulfate (AS) or calcium ammonium nitrate (CAN), were compared at an application rate of 220 kg N ha^?1. During the growth season (March to August) of winter wheat, N₂O emission rates were significantly higher in all three field experiments and in all treatments receiving N fertilizer than from the non‐fertilized treatments (control). At two of the three sites, cumulative N₂O emissions from N fertilizer decreased in the order of urea > AS > CAN, with emissions ranging from 522–617 g N ha^?1 (0.24–0.28% of applied fertilizer) for urea, 368–554 g N ha^?1 (0.17–0.25%) for AS, and 242–264 g N ha^?1 (0.11–0.12%) for CAN during March to August. These results suggest that mineral nitrogen forms can differ in N₂O emissions during the growth period of winter wheat. Strong variations in the seasonal dynamics of N₂O emissions between sites were observed which could partly be related to weather events (e.g., precipitation). Between harvest and the following spring (post‐harvest period) no significant differences in N₂O emissions between fertilized and non‐fertilized treatments were detected on two of three fields. Only on one site post‐harvest emissions from the AS treatment were significantly higher than all other fertilizer forms as well as compared to the control treatment. The cumulative one‐year emissions varied depending on fertilizer form across the three field sites from 0.05% to 0.51% with one exception at one field site (AS: 0.94%). The calculated overall fertilizer induced emission averaged for the three fields was 0.38% which was only about 1/3 of the IPCC default value of 1.0%.     

菜地土壤中氮肥的反硝化损失和N2O排放

A field experiment was conducted on Chinese cabbage （Brassica campestris L. ssp. pekinensis （Lour.） Olsson） in a Nanjing suburb in 2003. The experiment included 4 treatments in a randomized complete block design with 3 replicates： zero chemical fertilizer N （CK）; urea at rates of 300 kg N ha^-1 （U300） and 600 kg N ha^-1 （U600）, both as basal and two topdressings; and polymer-coated urea at a rate of 180 kg N ha^-1 （PCU180） as a basal application. The acetylene inhibition technique was used to measure denitrification （N2 ＋ N2O） from intact soil cores and N2O emissions in the absence of acetylene. Results showed that compared to （3K total denitrification losses were significantly greater （P ≤ 0.05） in the PCU180, U300, and U600 treatments,while N2O emissions in the U300 and U600 treatments were significantly higher （P ≤ 0.05） than （3K. In the U300 and U600 treatments peaks of denitrification and N2O emission were usually observed after N application. In the polymer-coated urea treatment （PCU180） during the period 20 to 40 days after transplanting, higher denitrification rates and N2O fluxes occurred. Compared with urea, polymer-coated urea did not show any effect on reducing denitrification losses and N2O emissions in terms of percentage of applied N. As temperature gradually decreased from transplanting to harvest, denitrification rates and N2O emissions tended to decrease. A significant （P ≤0.01） positive correlation occurred between denitrification （r = 0.872） or N2O emission （r = 0.781） flux densities and soil temperature in the CK treatment with a stable nitrate content during the whole growing season.     

The effect of nitrogen fertilization and no‐till duration on soil nitrogen supply power and post–spring thaw greenhouse‐gas emissions

With a world population now > 7 billion, it is imperative to conserve the arable land base, which is increasingly being leveraged by global demands for producing food, feed, fiber, fuel, and facilities (i.e., infra‐structure needs). The objective of this study was to determine the effect of varying fertilizer‐N rates on soil N availability, mineralization, and CO₂ and N₂O emissions of soils collected at adjacent locations with contrasting management histories: native prairie, short‐term (10 y), and long‐term (32 y) no‐till continuous‐cropping systems receiving five fertilizer‐N rates (0, 30, 60, 90, and 120 kg N ha^–1) for the previous 9 y on the same plots. Intact soil cores were collected from each site after snowmelt, maintained at field capacity, and incubated at 20°C for 6 weeks. Weekly assessments of soil nutrient availability along with CO₂ and N₂O emissions were completed. There was no difference in cumulative soil N supply between the unfertilized long‐term no‐till and native prairie soils, while annual fertilizer‐N additions of 120 kg N ha^–1 were required to restore the N‐supplying power of the short‐term no‐till soil to that of the undisturbed native prairie soil. The estimated cumulative CO₂‐C and N₂O‐N emissions among soils ranged from 231.8–474.7 g m^–2 to 183.9–862.5 mg m^–2, respectively. Highest CO₂ fluxes from the native prairie soil are consistent with its high organic matter content, elevated microbial activity, and contributions from root respiration. Repeated applications of ≥ 60 kg N ha^–1 resulted in greater residual inorganic‐N levels in the long‐term no‐till soil, which supported larger N₂O fluxes compared to the unfertilized control. The native prairie soil N₂O emissions were equal to those from both short‐ and long‐term no‐till soils receiving repeated fertilizer‐N applications at typical agronomic rates (e.g., 90 kg N ha^–1). Eighty‐eight percent of the native soil N₂O flux was emitted during the first 2 weeks and is probably characteristic of rapid denitrification rates during the dormant vegetative period after snowmelt within temperate native grasslands. There was a strong correlation (R² 0.64; p < 0.03) between measured soil Fe‐supply rate and N₂O flux, presumably due to anoxic microsites within soil aggregates resulting from increased microbial activity. The use of modern no‐till continuous diversified cropping systems, along with application of fertilizer N, enhances the soil N‐supplying power over the long‐term through the build‐up of mineralizable N and appears to be an effective management strategy for improving degraded soils, thus enhancing the productive capacity of agricultural ecosystems. However, accounting for N₂O emissions concomitant with repeated fertilizer‐N applications is imperative for properly assessing the net global warming potential of any land‐management system.     

Nitrous oxide emissions from artificial urine patches applied to different N-fertilized swards and estimated annual N2O emissions for differently fertilized pastures in an upland location in Germany

Abstract. Artificial urine containing 20.2 g N per patch of 0.2 m² was applied in May and September to permanent grassland swards of a long‐term experiment in the western uplands of Germany (location Rengen/Eifel), which were fertilized with 0, 120, 240, 360 kg N ha^?1 yr^?1 given as calcium ammonium nitrate. The effect on N₂O fluxes measured regularly during a 357‐day period with the closed‐chamber technique were as follows. (1) N₂O emission varied widely among the fertilized control areas without urine, and when a threshold water‐filled pore space >60% was exceeded, the greater the topsoil nitrate content the greater the flux from the individual urine patches on the fertilized swards. (2) After urine application in May, 1.4–4.2% of the applied urine‐N was lost as N₂O from the fertilized swards; and after urine application in September, 0.3–0.9% of the applied urine‐N was lost. The primary influence on N₂O flux from urine patches was the date of simulated grazing, N‐fertilization rate being a secondary influence. (3) The large differences in N₂O emissions between unfertilized and fertilized swards after May‐applied urine contrasted with only small differences after urine applied in September, indicating an interaction between time of urine application and N‐fertilizer rate. (4) The estimated annual N₂O emissions were in the range 0.6–1.6 kg N₂O‐N per livestock unit, or 1.4, 3.6, 4.1 and 5.1 kg N₂O‐N ha^?1 from the 0–360 kg ha^?1 of fertilizer‐N. The study demonstrated that date of grazing and N‐fertilizer application could influence the N₂O emission from urine patches to such an extent that both factors should be considered in detailed large‐scale estimations of N₂O fluxes from grazed grassland.     

Residual Effects of Novel versus Traditional Organic Amendments for Rain-fed No-till Barley: Yield,Nutrient Uptake,and N2O Emissions

Organic amendments recycle nutrients, but N₂O emissions are both environmental and agronomic concerns. We conducted a 4-year field experiment to determine no-till barley (Hordeum vulgare L.) yield and nutrient uptake and soil N₂O emissions following a single application of six amendment treatments: (1) no amendment (Check); (2) synthetic N fertilizer (Fert); (3) fresh beef cattle feedlot manure (ManureF); (4) beef cattle feedlot manure compost (CompostR); (5) beef cattle feedlot manure composted with cattle mortalities (CompostM); and (6) separated solids from anaerobically digested cattle feedlot manure (ADM). Barley grown in Year 1 (2006), Year 2 (2007), and Year 4 (2009) (with Year 3 (2008) under fallow) had higher grain yields from ManureF (4.73 Mg ha^?1) in Year 2 and ADM (6.30 Mg ha^?1) in Year 4 (p < 0.05) than other treatments. The grain N and P contents were not affected (p > 0.05), but N uptake over 3 years (112.8 kg N ha^?1 yr^?1), and P uptake in Year 1 (19.1 kg ha^?1 yr^?1) and Year 2 (14.3 kg ha^?1 yr^?1) from ManureF, were higher (p < 0.05×) than other treatments. The cumulative N₂O emissions from ManureF in Year 1 (1.488 kg N ha^?1) and from ADM in Year 2 (1.072 kg N ha^?1) were higher (p < 0.05) than other treatments while the fraction of applied N emitted as N₂O was small (0.00 to 0.79%) and not affected by treatment. However, the percentages of applied N emitted as N₂O from compost and ADM were similar to synthetic fertilizer and livestock manure.     

Nursery‐Box Total Fertilization Technology (NBTF) Application for Increasing Nitrogen Use Efficiency in Chinese Irrigated Riceland: N–Soil Interactions

High N fertilizer and flooding irrigation applied to rice in anthropogenic‐alluvial soil often result in N leaching and low use efficiency of applied fertilizer N from the rice field in Ningxia irrigation region in the upper reaches of the Yellow River. Sound N management practices need to be established to improve N use efficiency while sustaining high grain yield levels and minimize fertilizer N loss to the environment. We investigated the effects of Nursery Box Total Fertilization technology (NBTF) on N leaching at different rice growing stages, N use efficiency and rice yield in 2010 and 2011. The four fertilizer N treatments were 300 kg N ha⁻¹ (CU, Conventional treatment of urea at 300 kg N ha⁻¹), 120 kg N ha⁻¹ (NBTF120, NBTF treatment of controlled‐release N fertilizer at 120 kg N ha⁻¹), 80 kgN ha⁻¹ (NBTF80, NBTF treatment of controlled‐release N fertilizer at 80 kg N ha⁻¹) and no N fertilizer application treatment (CK). The results showed that the NBTF120 treatment increased N use efficiency, maintained crop yields and substantially reduced N losses to the environment. Under the CU treatment, the rice yield was 9634 and 7098 kg ha⁻¹, the N use efficiency was 31·6% and 34·8% and the leaching losses of TN were 44·51 and 39·89 kg ha⁻¹; NH₄⁺‐N was 5·26 and 5·49 kg ha⁻¹, and NO₃⁻‐N was 27·94 and 26·22 kg ha⁻¹ during the rice whole growing period in 2010 and 2011, respectively. Compared with CU, NBTF120 significantly increased the N use efficiency and decreased the N losses from the paddy field. Under NBTF120, the N use efficiency was 56·3% and 51·4%, which was 24·7% and 16·6% higher than that of CU, and the conventional fertilizer application rate could be reduced by 60% without lowering the rice yield while decreasing the leaching losses of TN by 16·27 and 14·36 kg ha⁻¹, NH₄⁺‐N by 0·90 and 1·84 kg ha⁻¹, NO₃⁻‐N by 110·6 and 10·14 kg ha⁻¹ in 2010 and 2011, respectively. Our results indicate that the CU treatment resulted in relatively high N leaching losses, and that alternative practice of NBTF which synchronized fertilizer application with crop demand substantially reduced these losses. We therefore suggest the NBTF120 be a fertilizer application alternative which leads to high food production but low environmental impact. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of Maize-Soybean Intercropping on Nitrous Oxide Emissions from a Silt Loam Soil in the North China Plain

Maize(Zea mays L.), a staple crop in the North China Plain, contributing substantially to agricultural nitrous oxide(N_2O)emissions in this region. Many studies have focused on various agricultural management measures to reduce N_2O emissions. However, few have investigated soil N_2O emissions in intercropping systems. In the current study, we investigate whether maize-soybean intercropping treatments could reduce N_2O emission rates. Two differently configured maize-soybean intercropping treatments, 2:2 intercropping(two rows of maize and two rows of soybean, 2M2S) and 2:1 intercropping(two rows of maize and one row of soybean,2M1S), and monocultured maize(M) and soybean(S) treatments were performed using a static chamber method. The results showed no distinct yield advantage for the intercropping systems. The total N_2O production from the various treatments was 0.15 ± 0.04–113.85 ± 12.75 μg m~(-2) min~(-1). The cumulative N_2O emission from the M treatment was 16.9 ± 2.3 kg ha~(-1) over the entire growing season(three and a half months), which was significantly higher(P 0.05) than that of the 2M2S and 2M1S treatments by 36.6% and 32.2%, respectively. Two applications of nitrogen(N) fertilizer(as urea) at 240 kg N ha~(-1) each induced considerable soil N_2O fluxes. Short-term N_2O emissions(within one week after each of the two N applications) accounted for 74.4%–83.3% of the total emissions. Soil moisture, temperature, and inorganic N were significantly correlated with soil N_2O emissions(R~2= 0.246–0.365, n =192, P 0.001). Soil nitrate(NO_3~-) and moisture decreased in the intercropping treatments during the growing season. These results indicate that maize-soybean intercropping can reduce soil N_2O emissions relative to monocultured maize.     

Effect of cattle slurry application techniques on N2O and NH3 emissions from a loamy soil

We determined N₂O fluxes from an unfertilized control (CON), from a treatment with mineral N‐fertilizer (MIN), from cattle slurry with banded surface application and subsequent incorporation (INC), and from slurry injection (INJ) to silage maize (Zea mays, L.) on a Haplic Luvisol in southwest Germany. In both years, amount of available N (total N fertilized + N_min content before N application) was 210 kg N ha^?1. In the slurry treatment of the 1^st year, 140 kg N ha^?1 were either injected or incorporated, whereas 30 kg N ha^?1 were surface applied to avoid destruction of the maize plants. In the 2^nd year, all fertilizers were applied with one single application. We calculated greenhouse gas emissions (GHG) on field level including direct N₂O emissions (calculated from the measured flux rates), indirect N₂O emissions (NH₃ and ${\mathrm{NO}}_3^{-}$ induced N₂O emission), net CH₄ fluxes, fuel consumption and pre‐chain emissions from mineral fertilizer. NH₃ losses were measured in the 2^nd year using the Dräger‐Tube Method and estimated for both years. NH₃ emission was highest in the treatment without incorporation. It generally contributed less than 5% of the greenhouse gas (GHG) emission from silage maize cultivation. The mean area‐related N₂O emission, determined with the closed chamber method was 2.8, 4.7, 4.4 and 13.8 kg N₂O‐N ha^?1 y^?1 for CON, MIN, INC, and INJ, respectively. Yield‐related N₂O emission showed the same trend. Across all treatments, direct N₂O emission was the major contributor to GHG with an average of 79%. Trail hose application with immediate incorporation was found to be the optimum management practice for livestock farmers in our study region.     

Nitrous Oxide Emissions from a Coal Mine Land Reclaimed with Stabilized Manure

Mine‐soil treatment using stabilized manure rapidly sequesters large quantities of organic carbon and nutrients. However, the nutrient‐rich soil conditions may become highly conducive for production and emission of N₂O. We examined this possibility in a Pennsylvania coal mine restored using poultry manure stabilized in two forms: composted (Comp) or mixed with paper mill sludge (Man + PMS) at C/N ratios of 14, 21, and 28 and compared those with the emissions from conventionally treated soil. The mine soil was extremely well drained with 59% coarse fragments. Soil–atmosphere exchange of N₂O and CO₂ was determined using a sampling campaign of ten measurements between 16 June and 14 September 2009 (90 days) and 13 measurements between 28 June and 9 November 2010 (134 days) using static vented chambers at ambient and increased moisture (water added) content. Potential denitrification was determined in a laboratory incubation experiment. While non‐amended mine soil did not have a measurable potential for denitrifying activity, the manure‐based amendments introduced the potential. Soil water filled pore space was less than 60% on most sampling days in both ambient and water‐added plots. Daily N₂O‐N emissions ranged between 40 and 70 g N ha⁻¹ with cumulative emissions of 2–4 kg N ha⁻¹ from non‐amended, lime and fertilizer (L + F) and Comp, and 3–10 kg N ha⁻¹ from Man + PMS treatments. The maximum emission obtained from Man + PMS represented <1% loss of applied N. Although stabilized manure‐treated soil exhibits the potential for N₂O production, the emission is limited when soils are excessively well drained and reducing conditions rarely develop. Copyright © 2015 John Wiley & Sons, Ltd.     

华北平原玉米季优化管理的密集型农业系统下一氧化二氮和甲烷通量研究

Addressing concerns about mitigating greenhouse gas （GHG） emissions while maintaining high grain yield requires improved management practices that achieve sustainable intensification of cereal production systems. In the North China Plain, a field experiment was conducted to measure nitrous oxide （N2O） and methane （CH4） fluxes during the maize （Zea mays L.） season under various agricultural management regimes including conventional treatment （CONT） with high N fertilizer application at a rate of 300 kg N ha-1 and overuse of groundwater by flood irrigation, optimal fertilization 1 treatment （OPTIT）, optimal fertilization 2 treatment （OPT2T）, and controlled-release urea treatment （CRUT） with reduced N fertilizer application and irrigation, and a control （CK） with no N fertilizer. In contrast to CONT, balanced N fertilization treatments （OPT1T, OPT2T, and CRUT） and CK demonstrated a significant drop in cumulative N20 emission （1.70 v.s. 0.43-1.07 kg N ha-l）, indicating that balanced N fertilization substantially reduced N20 emission. The vMues of the N20 emission factor were 0.42%, 0.29%, 0.32%, and 0.27% for CONT, OPTIT, OPT2T, and CRUT, respectively. Global warming potentials, which were predominantly determined by N20 emission, were estimated to be 188 kg CO2-eq ha-1 for CK and 419-765 kg CO2-eq ha-1 for the N fertilization treatments. Global warming potential intensity calculated by considering maize yield was significantly lower for OPT1T, OPT2T, CRUT, and CK than for CONT. Therefore, OPTIT, OPT2T, and CRUT were recommended as promising management practices for sustaining maize yield and reducing GHG emissions in the North China Plain.     

Nitrous oxide emissions in a winter wheat – summer maize double cropping system under different tillage and fertilizer management

An accurate estimation of nitrous oxide (N₂O) emission from 110 million ha of upland in China is essential for the adoption of effective mitigation strategies. In this study, the effects of different tillage practices combined with nitrogen (N) fertilizer applications on N₂O emission in soils were considered for a winter wheat (Triticum aestivum L.) – summer maize (Zea mays L.) double cropping system. Treatments included conventional tillage plus urea in split application (CTF1), conventional tillage with urea in a single application (CTF2), no‐tillage with straw retained plus reduced urea in a split application (NTSF1) and no‐tillage with manure plus reduced urea in a split application (NTMF1). The amounts of N input in each treatment were 285 and 225 kg N/ha for wheat and maize, respectively. Both NTSF1 and NTMF1 were found to reduce chemical N fertilizer rates by 33.3% (wheat) and 20% (maize), respectively, compared to CTF1 and CTF2. N₂O emissions varied between 3.2 (NTSF1) and 9.9 (CTF2) kg N₂O‐N/ha during the wheat season and between 7.6 (NTFS1) and 14.0 (NTMF1) kg N₂O‐N/ha during the maize season. The yield‐based emission factors ranged from 21.9 (NTSF1) to 60.9 (CTF2) g N₂O‐N/kg N for wheat and 92.5 (NTSF1) to 157.4 (NTMF1) g N₂O‐N/kg N for maize. No significant effect of the treatments on crop yield was found. In addition to reducing production costs involved in land preparation, NTSF1 was shown to decrease chemical fertilizer input and mitigate N₂O emissions while sustaining crop yield.     

Carbon dioxide and gaseous nitrogen emissions from biochar‐amended soils under wastewater irrigated urban vegetable production of Burkina Faso and Ghana

To quantify carbon (C) and nitrogen (N) losses in soils of West African urban and peri‐urban agriculture (UPA) we measured fluxes of CO₂‐C, N₂O‐N, and NH₃‐N from irrigated fields in Ouagadougou, Burkina Faso, and Tamale, Ghana, under different fertilization and (waste‐)water regimes. Compared with the unamended control, application of fertilizers increased average cumulative CO₂‐C emissions during eight cropping cycles in Ouagadougou by 103% and during seven cropping cycles in Tamale by 42%. Calculated total emissions measured across all cropping cycles reached 14 t C ha^?1 in Ouagadougou, accounting for 73% of the C applied as organic fertilizer over a period of two years at this site, and 9 t C ha^?1 in Tamale. Compared with unamended control plots, fertilizer application increased N₂O‐N emissions in Ouagadougou during different cropping cycles, ranging from 37 to 360%, while average NH₃‐N losses increased by 670%. Fertilizer application had no significant effects on N₂O‐N losses in Tamale. While wastewater irrigation did not significantly enhance CO₂‐C emissions in Ouagadougou, average CO₂‐C emissions in Tamale were 71% (1.6 t C ha^?1) higher on wastewater plots compared with those of the control (0.9 t C ha^?1). However, no significant effects of wastewater on N₂O‐N and NH₃‐N emissions were observed at either location. Although biochar did not affect N₂O‐N and NH₃‐N losses, the addition of biochar could contribute to reducing CO₂‐C emissions from urban garden soils. When related to crop production, CO₂‐C emissions were higher on control than on fertilized plots, but this was not the case for absolute CO₂‐C emissions.     

Emissions of CO2, N2O,and NO in conventional and no-till management practices in Rondônia,Brazil

Efforts to restore productivity of pastures often employ agricultural management regimes involving either tillage or no-tillage options combined with various combinations of fertilizer application, herbicide use and the planting of a cash crop prior to the planting of forage grasses. Here we report on the emissions of CO₂, N₂O and NO from the initial phases (first 6 months) of three treatments in central Rondônia. The treatments were (1) control; (2) conventional tillage followed by planting of forage grass (Brachiaria brizantha) and fertilizer additions; (3) no-tillage/herbicide treatment followed by two plantings, the first being a cash crop of rice followed by forage grass. In treatment 3, the rice was fertilized. Relative to the control, tillage increased CO₂ emission by 37% over the first 2 months, while the no-tillage/herbicide regime decreased CO₂ emissions by 7% over the same period. The cumulative N₂O emissions over the first 2 months from the tillage regime (0.94 kg N ha^–1) were much higher than the N₂O releases from either the no-tillage/herbicide regime (0.64 kg N ha^–1) or the control treatment (0.04 kg N ha^–1). The highest levels of N₂O fluxes from both management regimes were observed following N fertilizations. The cumulative NO releases over the first 2 months were largest in the tillage treatment (0.98 kg N ha^–1), intermediate in the no-tillage treatment (0.72 kg N ha^–1), and smallest in the control treatment (0.12 kg N ha^–1). For the first week following fertilization the percentage of fertilizer N lost as N₂O plus NO was 1.0% for the tillage treatment and 3.0% for the no-tillage treatment.