Organic Manures and Crop Residues as Fertilizer Substitutes: Impact on Nitrous Oxide Emission, Plant Growth and Grain Yield in Pre-Monsoon Rice Cropping System

It has been previously argued that application of organic residues added in soils has a great impact on soil quality, grain productivity as well as greenhouse gas emissions. Substitution of chemical fertilizers has become a common practice in agricultural systems which consequently affect the greenhouse gas emissions from agricultural fields. To observe the effects of organic manures and crop residues amendments, five fertilizer treatments including conventional inorganic nitrogen fertilizer—NPK, cow manure, rice straw, poultry manure and sugarcane bagasse were applied in the field for two consecutive pre-monsoon rice seasons. Addition of rice straw, poultry manure and sugarcane bagasse decreased the cumulative N2O emissions by 14% and 31%, and by 1% and 7% and 5% and 3% in 2012 and 2013 respectively when compared with conventional fertilizer treatment (NPK) in both the seasons. Yield differences were not significant (p > 0.005) amongst the treatments, however, a slight increase was observed due to rice straw amendment over control. Soil organic carbon decreased by 11% - 17% under the application of organic residues which might have contributed to lower N2O emissions from the plots. Results of carbon equivalent emission (CEE) and carbon efficiency ratio (CER) indicated that incorporation of rice straw during pre-monsoon rice season had the potential to reduce the N2O emissions and yield scaled emissions of rice production at lower level than the conventional farmers’ practice of using chemical fertilizers (NPK).

A Process-based Model of N_2O Emission from a Rice-Winter Wheat Rotation Agro-Ecosystem:Structure,Validation and Sensitivity

In order to numerically simulate daily nitrous oxide （N2O） emission from a rice-winter wheat rotation cropping system, a process-based site model was developed （referred to as IAP-N-GAS） to track the movement and transformation of several forms of nitrogen in the agro-eeosystem, which is affected by climate, soil, crop growth and management practices. The simulation of daily N2O fluxes, along with key daily environmental variables, was validated with three-year observations conducted in East China. The validation demonstrated that the model simulated well daily solar radiation, soil temperature and moisture, and also captured the dynamics and magnitude of accumulated rice aboveground biomass and mineral nitrogen in the soil. The simulated daily N2O emissions over all three years investigated were generally in good agreement with field observations. Particularly well simulated were the peak N2O emissions induced by fertilizations, rainfall events or mid-season drainages. The model simulation also represented closely the inter-annuM variation in N2O emission. These validations imply that the model has the capability to capture the general characteristics of N2O emission from a typical rice-wheat rotation agro-ecosystem. Sensitivity analyses revealed that the simulated N2O emission is most sensitive to the fertilizer application rate and the soil organic matter content, but it is much less sensitive to variations in soil pH and texture, temperature, precipitation and crop residue incorporation rate under local conditions.

Effect of Substitution Degree and the Calcination Temperature on the N₂O Decomposition over Zinc Cobaltite Catalysts

In this paper, a series of zinc cobaltite catalysts with the general formula Znx-Co1-xCo2O4 (x = 0.25, 0.50, 0.75 and 1.0) has been prepared using the co-precipitation method. Thermal analyzes (TGA and DTA) were used to follow up the thermal events accompanying the heat treatment of the parent mixture. Based on these results, the various parent mixtures were calcined at 500℃. The obtained solid catalysts were characterized by using XRD, FT-IR and N2-adsorption. The catalytic decomposition of N2O to N2 and O2 was carried out on the zinc-cobaltite catalysts. It was found that partial replacement of Co2+ by Zn2+ in Co3O4 spinel oxide led to a significant improvement in their N2O decomposition activity. Moreover, the catalytic activity was found to be depended on the calcination temperature utilized.

Atmospheric N2O gas detection based on an inter-band cascade laser around 3.939 μm

N2O is a significant atmospheric greenhouse gas that contributes to global warming and climate change.In this work,the high sensitivity detection of atmospheric N2O is achieved using wavelength modulation spectroscopy(WMS)with an inter-band cascade laser operating around 3.939μm.A Lab VIEW-based software signal generator and software lock-in amplifiers are designed to simplify the system.In order to eliminate the interference from water vapor,the detection was performed at a pressure of 0.1 atm(1 atm=1.01325×10^5 Pa)and a drying tube was added to the system.To improve the system performance for long term detection,a novel frequency locking method and 2 f/1 f calibration-free method were employed to lock the laser frequency and calibrate the power fluctuations,respectively.The Allan deviation analysis of the results indicates a detection limit of^20 ppb(1 ppb=1.81205μg/m3)for a 1 s integration time,and the optimal detection limit is^5 ppb for a 40-s integration time.

Water regime-nitrogen fertilizer incorporation interaction：Field study on methane and nitrous oxide emissions from a rice agroecosystem in Harbin, China

Water regime and nitrogen（N） fertilizer are two important factors impacting greenhouse gases（GHG） emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we conducted a two-year field experiment to study the impacts of water regime and N fertilizer on rice yields and GHG emissions in Harbin, China, a cold region located in high latitudes. Our results showed that intermittent irrigation significantly decreased methane（CH4） emission compared with continuous flooding, however,the decrement was far lower than the global average level. The N2O emissions were very small when flooded but peaked at the beginning of the disappearance of floodwater. The N fertilizer treatments increased CH4 emissions at low level（75 kg N/ha）. But both CH4 and N2O emissions were uninfluenced at the levels of 150 kg N/ha and 225 kg N/ha. Rice yields increased under intermittent irrigation and were highest at the level of 150 kg N/ha. From our results, we recommended that the intermittent irrigation and 150 kg N/ha as the ideal water regime-nitrogen fertilizer incorporation for this area to achieve low GHG emissions without impacting rice yields.

不同生境下氮沉降对土壤N_(2)O通量影响的整合分析

基于在我国开展的66个野外氮沉降模拟试验的290组数据,采用整合分析方法,探究实验样地特征(气候因子、土壤性质)和施氮因素对施氮后土壤N_(2)O通量变化的影响。结果表明:样地的年均降水量、年均温、自然氮沉降量和土壤C/N与施氮后N_(2)O通量增幅呈显著正相关,土壤pH与施氮后N_(2)O通量增幅呈显著负相关。湿地生态系统土壤对施氮最敏感,森林生态系统次之,草原生态系统最小。所有的样地因子中,土壤pH和C/N对施氮后N_(2)O通量变化幅度的影响最大。施加硝态氮后土壤N_(2)O通量增幅最大,施加尿素与铵态氮后N_(2)O通量增幅相当,而施加硝酸铵后N_(2)O通量增幅最小。综上,在准确评估和预测土壤N_(2)O通量对氮沉降的响应时,应综合考虑样地特征及氮源种类的影响。

Nitrifiers activity and community characteristics under stress conditions in partial nitrification systems treating ammonium-rich wastewater

Long-term exposure of nitrifiers to high concentrations of free ammonia （FA） and free nitrous add （FNA） may affect nitrifiers activity and nitrous oxide （N2O） emission. Two sequencing batch reactors （SBRs） were operated at influent ammonium nitrogen （NH4-N） concentrations of 800 mg/L （SBRH） and 33S mg/L （SBRL）, respectively. The NH4-N removal rates in SBRH and SBRL were around 2.4 and 1.0 g/L/day with the nitritation efficiencies of 99.3% and 95.7%, respectively. In the simulated SBR cycle, the N20 emission factors were 1.61% in SBRH and 2.30% in SBRL. N2O emission was affected slightly by FA with the emission factor of 0.22%-0.65%, while N2O emission increased with increasing FNA concentrations with the emission factor of 0.22%～3.96%. The dominant ammonia oxidizing bacteria （AOB） were Nitrosomonas spp. in both reactors, and their relative proportions were 38.89% in SBRH and 13.36% in SBRL. Within the AOB genus, a species （i.e., operational taxonomic unit [OTU] 76） that was phylogenetically identical to Nitrosomonas europaea accounted for 99.07% and 82.04% in SBRH and SBRL, respectively. Additionally, OTU 215, which was related to Nitrosomonas stercoris, accounted for 16.77% of the AOB in SBRL.