Ammonia Volatilization Process Research Articles

Analysis of Ammonia Volatilization Loss from a Paddy Soil with Empirical and Mechanistic Models

AbstractAmmonia volatilization from agricultural land has a negative impact on the atmospheric, aqueous, and land environments. However, this process is still not fully understood. In this study, a 2‐year field experiment is conducted in the Taihu Lake region of China to monitor ammonia volatilization from a paddy soil. The ammonia volatilization losses are in the range of 43.4 to 53.6 kg N ha−1 in the year 2013 and 25.9 to 35.4 kg N ha−1 in the year 2014, which account for 19.7% to 19.9% and 11.8% to 13.1% of the applied nitrogen with two different N treatments (N1: 220 kg N ha−1, N2: 270 kg N ha−1). The ammonia volatilization loss is highest during the basal fertilizer application, followed by the tillering and the ear‐differentiation stages. Then, two empirical models and one mechanistic model are used to simulate the ammonia volatilization process. These models are calibrated and validated with field experimental data. The results show that none of the three models accurately predict the ammonia volatilized from the rice field (R2 < 0.40), however, among the three models evaluated, the mechanistic model is more effective in simulating the ammonia volatilization process (R2 = 0.38).

Effects of biochar on ammonia volatilization from farmland soil: A review.

Reducing soil ammonia volatilization is one of the key ways to reduce soil nitrogen loss and improve nitrogen utilization efficiency in farmlands. Biochar has unique physico-chemical pro-perties, which can change soil physical and chemical properties, affect soil nitrogen cycle, and affect ammonia volatilization in farmland soil. Firstly, we reviewed the ammonia volatilization process and its influencing factors (climatic condition, soil environment, and fertilization management, etc.) in paddy fields and upland fields. Then, research progress on the impacts of biochar on ammonia volatilization from farmland ecosystem was reviewed. Furthermore, the mechanisms underlying the responses of ammonia volatilization to biochar intervention were discussed from the aspects of physical adsorption, gas-liquid equilibrium, and biochemical progress regulation. The reduction of soil ammonia volatilization is mainly based on the adsorption of soil NH4+ and NH3 by oxygen-containing functional groups on the surface of biochar and the promotion of soil nitrification. How-ever, the increases of soil ammonia volatilization are mainly related to the increases of soil pH, air permeability, activities of microorganisms related with soil organic nitrogen mineralization. Finally, the research direction of reducing soil ammonia volatilization and improving nitrogen utilization efficiency by biochar was prospected.

Membrane-based conductivity probe for real-time in-situ monitoring rice field ammonia volatilization

Reliable real-time and in-situ monitoring of ammonia volatilization could provide invaluable information in improving agriculture ammonia fertilizer utilization efficiency and solving ammonia relevant environmental issues, however, few applicable monitoring techniques are available in the current market. This work reported a new gaseous ammonia sensing principle and developed a gas-permeable membrane-based conductivity probe (GPMCP) to obtain critical information that enables insightful understanding of agriculture ammonia volatilization process. The analytical principle based on real-time measurement of the rate of conductivity increment in the receiving solution to achieve real-time, in-situ gaseous ammonia concentration and volatilization flux in a reliable and continuous fashion. It is also capable of obtaining an average ammonia volatilization flux and amount over a deployment period. The delicate design of GPMCP and developed precalibration strategy in this study bestows this technique a direct method that can effectively avoid ongoing calibration. Field deployments results showed that GPMCP had significant advantages on presenting continuous detailed ammonia volatilization information. The reported GPMCP can be an effective tool to monitor agricultural ammonia volatilization process.

NO3− circulation and associated driving factors in the unsaturated zone of southwestern Tengger Desert, Northwestern China

In the southwestern Tengger desert in northwestern China, nitrate circulation processes in the unsaturated zone and associated driving factors were studied using water chemistry and stable isotope techniques. At unvegetated sand sites, NO3− content increases from the south to north in the desert. Additionally, a negative correlation (R2 = 0.90, P < 0.005) was evident between the stability of soil NO3− and elevation, suggesting that NO3− storage in soil is significantly influenced by precipitation and temperature. And a significant positive correlation between mNO2−/Cl− in unsaturated zone and elevation (R2 = 0.50, P < 0.0001), indicating both nitrification and denitrification are strongly in the south of desert, however, the nitrification plays a dominant role in the north of desert. Isotopic analyses (δ15N-NO3−, δ18O-NO3−, and δ18O-H2O, δ2H-H2O) of soil pore-water showed that the two dominant NO3− sources were the mixing of atmospheric deposition and soil nitrification, and that the NO3− circulation at the vegetated sand sites was affected by vegetation and animals. Additionally, local environmental conditions lead to complex driving factors, such as the abiotic process of ammonia volatilization of NO3− circulation, which resulted in the 15N enrichment and 18O depletion of residual nitrate in the unsaturated zone of one of the soil profiles. Denitrification was noted in the deep unsaturated zone of two profiles, indicating that the N loss resulted from abiotic versus biotic processes. Analyses of the stable isotope results and the distribution characteristics of NO3− and Cl− suggests leaching of soil NO3− as a result of NO3− in unsaturated zone poses a potential threat to groundwater quality in Dengmaying region. This study suggests that NO3− circulation in the unsaturated zone responds to climate characteristics in the desert ecosystem, and to provide useful information for the protection of groundwater quality in arid desert regions.

The interactive effects of water and nitrogen addition on ammonia volatilization loss and yield of winter wheat.

An experiment with winter wheat of Shimai 15 and treatments of two types of fertilizers (organic manure, M; urea, U), two amounts of nitrogen application (180 kg·hm-2, M1U1; 90 kg·hm-2, M2U2), two irrigation levels (500 mm, W1; 250 mm, W2) was carried out in the lysimeters in 2015-2017. The results showed that ammonia volatilization was substantial after fertilization and irrigation. The dynami of ammonia volatilization during two years was similar. The process of ammonia volatilization after fertilization lasted for seven days. In 2015-2016, the total amount of ammonia volatilization ranged from 13.36 to 46.04 kg·hm-2, and the loss rate of ammonia nitrogen ranged from 8.9% to 41.1%. The total amount of ammonia volatilization in 2016-2017 ranged from 14.78 to 52.99 kg·hm-2, and the ammonia nitrogen loss rate ranged from 9.2% to 45.8%. During the two years, the highest loss of ammonia volatiles occurred in W2U1, the highest loss rate of ammonia volatilization occurred in W2U2. Ammonia volatilization loss rate significantly decreased under appropriate water and nitrogen management. Ammonia loss under the application of urea was about 2-3 times of organic manure. The highest yield occurred in W1M1 during the two growing seasons. The type of fertilizer, the amount of irrigation and nitrogen applied interactively affected the yield of winter wheat. As for the increases of production, organic manure was better than urea. Under the experimental condition, the best treatment was irrigation amount of 500 mm and application of organic manure with about 180 kg·hm-2 of N fertilizers, which could be applied in practice for wheat production in Huang-Huai-Hai region.

Impact of Anaerobic Digestion of Liquid Dairy Manure on Ammonia Volatilization Process

<abstract> <bold><sc>Abstract.</sc></bold> The goal of this study was to determine the effect of anaerobic digestion (AD) on ammonia volatilization from liquid dairy manure, in storage or treatment lagoon, prior to land application. Physical and chemical properties of liquid dairy manure, which may affect ammonia volatilization, were determined before and after AD. The properties of interest included particle size distribution (PSD), total solids (TS), volatile solids (VS), viscosity, pH, total ammoniacal nitrogen (TAN), and ionic strength (IS). The overall mass transfer coefficient of ammonia (K_oL) and the NH₃ fraction of TAN (β) for the undigested (UD) and AD manures were then experimentally determined in a laboratory convective emission chamber (CEC) at a constant wind speed of 1.5 m s^-1 and fixed air temperature of 25°C at manure temperatures of 15°C, 25°C, and 35°C. The PSD indicated non-normal left-skewed distributions for both AD and UD manures particles, suggestive of heavier concentrations of particles toward the lower particle size range. The volume median diameters (VMD) for solids from UD and AD were not significantly different (p= 0.65), but the geometric standard deviations (GSD) were significantly different (p = 0.001), indicating slightly larger particles but more widely distributed solids in UD manure than in AD manure. Results also indicated significantly higher pH, TAN, ionic strength (IS), and viscosity in AD manure. The β for AD manure, determined under identical conditions (air temperature, liquid temperature, and airflow), was significantly higher (p < 0.001) than for UD manure. However, mass transfer of ammonia (K_oL) was significantly lower for AD manure than for UD manure (p < 0.001). Overall, these findings suggest that AD of dairy manure significantly increased initial ammonia volatilization potential from liquid dairy manure, with the largest increase (~61%) emanating from increased ammonium dissociation. The initial flux of ammonia, at 15°C, was ~16% more from AD manure than from UD manure.

Spatial variation of ammonia volatilization from soil and its scale‐dependent correlation with soil properties

SummaryQuantitative predictions of ammonia volatilization from soil are useful to environmental managers and policy makers and empirical models have been used with some success. Spatial analysis of the soil properties and their relationship to the ammonia volatilization process is important as predictions will be required at disparate scales from the field to the catchment and beyond. These relationships are known to change across scales and this may affect the performance of an empirical model. This study is concerned with the variation of ammonia volatilization and some controlling soil properties: bulk density, volumetric water content, pH, CEC, soil pH buffer power, and urease activity, over distances of 2, 50, 500, and &gt;2000 m. We sampled a 16 km × 16 km region in eastern England and analyzed the results by a nested analysis of (co)variance, from which variance components and correlations for each scale were obtained. The overall correlations between ammonia volatilization and the soil properties were generally weak: –0.09 for bulk density, 0.04 for volumetric water content, –0.22 for CEC, –0.08 for urease activity, –0.22 for pH and 0.18 for the soil pH buffer power. Variation in ammonia volatilization was scale‐dependent, with substantial variance components at the 2‐ and 500‐m scales. The results from the analysis of covariance show that the relationships between ammonia volatilization and soil properties are complex. At the &gt;2000 m scale, ammonia volatilization was strongly correlated with pH (–0.82) and CEC (–0.55), which is probably the result of differences in parent material. We also observed weaker correlations at the 500‐m scale with bulk density (–0.61), volumetric water content (0.48), urease activity (–0.42), pH (–0.55) and soil pH buffer power (0.38). Nested analysis showed that overall correlations may mask relationships at scales of interest and the effect of soil variables on these soil processes is scale‐dependent.

A process-based model of ammonia emissions from dairy cows: improved temporal and spatial resolution

This research has developed an integrated model of a dairy farm that predicts monthly ammonia emission factors based on farming practices and climate conditions, including temperature, wind speed, and precipitation. The model can be used to predict the seasonal and geographic variations in ammonia emission factors, which are important for accurately predicting aerosol nitrate concentrations. The model tracks the volume of manure and mass of ammoniacal nitrogen as the manure moves through the housing, storage, application, and grazing stages of a dairy farm. Most of the processes of ammonia volatilization are modeled explicitly, but poorly understood processes are parameterized and tuned to match empirical data. The tuned model has been compared to independent experimental data and is shown to be robust over the range of experimental conditions. We have characterized the differences in emissions resulting from changes in climate conditions and farming practices and found that both of these factors are significant and should be included when developing a national inventory.

Ammonia Volatilization Following Application of Livestock Manure to Arable Land

Ammonia volatilization from land-spreading of livestock manure was investigated by using a new micrometeorological measuring method based on passive diffusion sampling close to the ground surface. The approach implies that estimates of two parameters must be made: (1) the driving force, that is, the difference between the equilibrium concentration ( C eq) and the ambient concentration ( C a,z), and (2) the surface resistance represented by a mass transfer coefficient ( K z,a). The effect of factors related to meteorology, soil/manure characteristics and mode of application on NH 3 volatilization was examined in the laboratory and some of the results were validated by field experiments. Temperature influenced C eq according to a mathematical relationship, although absolute concentration level could not be estimated on the basis of temperature, pH and ammonia content only. It was suggested that temperature and air humidity interact in the dynamics of the ammonia volatilization process, primarily by establishing changes with time by an ammonia enrichment factor. Manure fluidity, a parameter related to dry matter content, substantially influenced C eq, as did the mode of application. By means of incorporation, volatilization rates could be reduced by as much as 83 to 98%, depending on type of manure and mode of incorporation. Differences in application rates did not influence the relative C eq but a linear relationship was suggested between the fraction of surface area covered and the initial C eq. Volatilization from band spreading and broadcast spreading followed different time courses in the initial stage after application but the cumulative loss difference was similar with time.

Isotopic fractionation accompanying fertilizer nitrogen transformations in soil and trees of a Scots spine ecosystem

Foliage from a mature stand of Scots pine (Pinus sylvestris L.) receiving increasing doses of ammonium nitrate and urea nitrogen was assayed during the five subsequent growing seasons for total N concentration and 15N abundance. The aim of the study was to examine the potential of the δ15N technique to provide estimates on fertilizer N recovery and its fate in the ecosystem. The 15N abundance in the foliage increased in proportion to the dose of fertilizer application. This was generally owing to the fact that the δ15N of the fertilizer N was significantly higher than that in the soil inorganic-N pool, as well as in the needle biomass of the Scots pine trees on the nonfertilized plots. Due to 15N isotope discrimination occurring during N transformations in soil the relationship was however not very close. Calculations based on the principle of isotope dilution yielded only rough and, in some cases, even misleading estimates of the fraction of the fertilizer-derived nitrogen (Ndff) in the needles. This was especially the case for the urea-N, which undergoes significant isotopic fractionation during the process of ammonia volatilization and possibly microbial NH4+ assimilation in soil. Over five growing seasons, foliar total N concentration peaked at the end of the second season while the 15N abundance continued to increase. Although large methodological errors may be involved when interpreting natural 15N abundance, the measurement of δ15N seems to provide semi-quantitative information about fertilizer N accumulation and transformation processes in coniferous ecosystems. A better understanding of the tree and soil processes causing isotopic fractionation is a prerequisite for correct interpretation of 15N data.

A model of ammonia volatilization from applied urea. I. Development of the model

SUMMARYUrea application to soil raises the pH and ammonium concentration, thus providing ideal conditions for ammonia volatilization. A mechanistic model is presented, which combines the process of ammonia volatilization with the simultaneous transformation and movement of urea and its products in soil, for predicting the concentration profiles of urea, ammoniacal‐nitrogen and soil pH, and ammonia losses, following application of urea.The model consists of continuity equations describing the diffusion and reaction of urea, ammoniacal‐nitrogen and soil base; it takes into account the volatilization of ammonia and the concurrent acidification of the soil surface; and considers a variable PCo2 profile due to soil respiration and urea hydrolysis. The derivation of the continuity equations and their boundary conditions, calculations of ammonia volatilization, and appropriate methods for numerical solutions are described.

Effect of Nitrogen Source and Management on Ammonia Volatilization Losses from Flooded Rice‐Soil Systems

AbstractAmmonia volatilization was studied by equipping capped greenhouse pots with a forced‐draft system with external acid trap or by placement of open pots in a closed gas‐lysimeter (allowing plant growth) with internal acid traps. In both systems air turbulence was optimized to simulate undisturbed open systems. Flooded soils were fertilized with approximately 50 or 100 kg N/ha of granular urea (GU), ammonium sulfate (AS), and two modified urea products—sulfur‐coated urea (SCU) and urea supergranule (USG). The first three materials were broadcast and incorporated, whereas the last was placed at a depth of 8 cm.Ammonia volatilization from urea proceeded rapidly following hydrolysis of urea in the floodwater, leading to losses of up to 50% of the applied urea within 2 to 3 weeks. Ammonia loss from (NH4)2SO4 occurred to a lesser extent due to a lack of alkalinity and occurred at a nearly constant rate, accumulating to ∼15% loss in 3 weeks. Ammonia losses from the modified urea materials were negligible.Soil pH had little effect on the pH of the floodwater and, thus, on the ammonia volatilization process. However, ammonia volatilization losses were generally reduced by factors that reduced the level of ammoniacal N in the floodwater, such as increasing soil CEC and reduced N application.Daily ammonia volatilization losses correlated well (r = 0.92) with the NH3(aq) concentration of the floodwater sampled between 1000 and 1100 hours each day. This observation holds promise for the development of a simple technique for assessing ammonia volatization losses from flooded soils based on simple physical and chemical parameters of the floodwater.