Volatilization of ammonia from submerged tropical soils

Summary A laboratory study was made of the losses of nitrogen through ammonia volatilization from four flooded, tropical soils. The soils used varied considerably in pH, organic matter content, and cation exchange capacity. Losses were measured from the unamended soils, and from ammonium sulphate and urea-treated soils. Two rates of nitrogen application (approximately 50 and 200 kg/ha N) and two methods of application (simulated field broadcast and fertilizer incorporation) of the nitrogen were used. Losses of ammonia were detected for each of the unamended soils, including an acid sulphate soil of pH 3.6. Increased application of both ammonium sulphate and urea resulted in increased losses of ammonia through volatilization. Incorporation of the nitrogen into the mud of the flooded soils significantly decreased losses due to volatilization. It was concluded that the initial or ‘aerobic’ pH of the soils was the soil characteristic most closely related to the magnitude of losses due to volatilization.     

Leaching of nitrogen from subtropical soils as affected by nitrification potential and base cations

A soil column method was used to determine the effect of nitrification on leaching of nitrate and ammonium from three acid subtropical soils after application of ammonium bicarbonate. Three soils, designated QF, GB and SU, derived from Quaternary red earth, granite and tertiary red sandstone, were collected from forest land, brush land and upland field, ranged in nitrification potential and cation exchange capacity. The results indicated that nitrate leaching increased with the soil nitrification potential. The soils with higher nitrification potential had a higher nitrate peak concentration and required a shorter time to reach it. In soils QF and GB with low cation exchange capacity, and a low content of exchangeable base cations, there were not sufficient base cations to accompany the nitrate leached with the result that ammonium and hydrogen ions were leached from the soil, and pH changes occurred in different layers of the soil column.     

The volatilization of ammonia from cattle urine applied to soils as influenced by soil properties

The amounts of ammonia volatilized, following the application of cattle urine to 22 soils, were measured in the laboratory during an incubation period of 10 days. The urine contained 12.0 g N dm^-3 and was applied to small columns of soil at a rate equivalent to 26.5 g N m^-2. The soils were from fields of both grassland and arable cultivation and varied widely in properties. Ammonia volatilization ranged from 6.8 to 41.3% of the total urinary N, with a mean value of 26.4%. The soil property most closely related to the extent of volatilization was cation exchange capacity (CEC), and this was so whether all 22 soils were considered together or whether the 14 grassland and 8 arable soils were considered separately. In general, the higher the CEC the less the amount of ammonia volatilized. However, for a given value of CEC, volatilization tended to be greater from a grassland than from an arable soil. The pH of a soil/urine mixture measured after 24 hours was also quite closely correlated with the amount of ammonia volatilized, but the initial pH and titratable acidity of the soil were poorly correlated with ammonia volatilization. ei]H Marschner ei]H Lambers     

Ammonia volatilization from a flooded tropical soil

Summary Ammonia volatilization, which follows upon the application of nitrogenous fertilizers to a flooded tropical soil, was directly measured in the greenhouse and in the field. Most of the ammonia volatilization losses occurred during the first 9 days after nitrogen application. Ammonia volatilization increased markedly with increases in soil pH. Nitrogen losses from ammonium sulfate applied to soils whose pH values were below 7.5 were very small. The losses from urea were much greater than those from ammonium sulfate. Mixing the fertilizer materials with the puddled soil reduced the losses. Ammonia losses from flooded soil were larger than from dry soil, and drying of a flooded soil reduced the duration and magnitude of ammonia volatilization. It is suggested that only a small amount of nitrogen is being lost through ammonia volatilization from many lowland rice soils. re]19750820     

Ammonia volatilization from applied nitrogen in alkali soils

Incubation studies in a highly alkali soil showed ammonia volatilization losses from applied nitrogen to be largely governed by pH/alkalinity of the system. Submergence of the soil decreased the pH value resulting in lower losses. The anion of ammonium did not influence the losses. Ammonia volatilization obeyed first order kinetics. The losses were considerably reduced by deep placement of urea but were unchanged with variation in temperature from 20° to 40°C. Urea or ammonium sulphate lost similar amounts of nitrogen. Losses from green manure were very low. The results are discussed for their implication in nitrogen fertilizer efficiency and management in alkali soils.     

滨海盐渍农田土壤硝化势特征及其影响因素

明确滨海盐渍农田土壤的硝化能力,探究土壤环境中影响硝化过程的主要因子,对调控农田土壤硝化作用和提高氮肥利用率具有重要意义。通过野外调查和室内分析相结合的方法,研究了滨海淤泥质滩涂盐渍区域(东营市和东台市)农田土壤硝化势和土壤物理、化学、生物学性质,运用多元逐步回归分析和结构方程模型(SEM)建立了土壤性质与土壤硝化势的相关关系。结果表明:滨海盐渍农田土壤除pH值较稳定外,其他土壤性质和土壤硝化势变化差异较大。土壤硝化势范围为0.04～10.42 mg·kg^-1·d^-1,随土壤盐渍化程度增加而降低。相关分析表明,土壤硝化势与土壤有机质、阳离子交换量和Cl^-的相关性最强,相关系数分别为0.409、0.397和-0.337;而多元逐步回归分析表明,Na⁺、粉粒、阳离子交换量、CO₃^2-+HCO₃^-为土壤硝化势的主要影响因子。SEM分析结果表明,Na⁺、粉粒、阳离子交换量、CO₃^2-+HCO₃^-为影响土壤硝化势的直接因子,有机质、黏粒、Cl^-、SO₄^2-为影响土壤硝化势的间接因子。总之,土壤Na⁺和阳离子交换量是影响硝化作用的两个主要因素,在该区域调控土壤NaCl含量和阳离子交换量为调节土壤硝化过程的有效手段。     

Autotrophic Ammonia Oxidation at Low pH through Urea Hydrolysis

Ammonia oxidation in laboratory liquid batch cultures of autotrophic ammonia oxidizers rarely occurs at pH values less than 7, due to ionization of ammonia and the requirement for ammonium transport rather than diffusion of ammonia. Nevertheless, there is strong evidence for autotrophic nitrification in acid soils, which may be carried out by ammonia oxidizers capable of using urea as a source of ammonia. To determine the mechanism of urea-linked ammonia oxidation, a ureolytic autotrophic ammonia oxidizer, Nitrosospira sp. strain NPAV, was grown in liquid batch culture at a range of pH values with either ammonium or urea as the sole nitrogen source. Growth and nitrite production from ammonium did not occur at pH values below 7. Growth on urea occurred at pH values in the range 4 to 7.5 but ceased when urea hydrolysis was complete, even though ammonia, released during urea hydrolysis, remained in the medium. The results support a mechanism whereby urea enters the cells by diffusion and intracellular urea hydrolysis and ammonia oxidation occur independently of extracellular pH in the range 4 to 7.5. A proportion of the ammonia produced during this process diffuses from the cell and is not subsequently available for growth if the extracellular pH is less than 7. Ureolysis therefore provides a mechanism for nitrification in acid soils, but a proportion of the ammonium produced is likely to be released from the cell and may be used by other soil organisms.     

Nitrogen transformation processes in relation to improved cultural practices for lowland rice

Summary Inappropriate method and timing of N fertilizer application was found to result in 50–60% N losses. Recent nitrogen transformation studies indicate that NH₃ volatilization in lowland rice soils is an important loss mechanism, causing a 5–47% loss of applied fertilizer under field conditions. Estimated denitrification losses were between 28 and 33%. Ammonia volatilization losses from lowland rice can be controlled by i) placement of fertilizer in the reduced layer and proper timing of application, ii) using phenylphosphorodiamidate (PPD) to delay urease activity in flooded soils, and iii) using algicides to help stabilize changes in floodwater pH. Appropriate fertilizer placement and timing is probably the most effective technique in controlling denitrification at the farm level. The effectivity of nitrification inhibitors as another method is still being evaluated. With 60–80% of N absorbed by the crop derived from the native N pool, substantial yield gains in lowland rice are highly possible with resources already in the land. Extensive studies on soil N and its management, and an understanding of soil N dynamics will greatly facilitate the decrease in immobilization and ammonium fixation in the soil and the increase in N availability to the rice crop. Critical research needs include greater emphasis on N transformation processes in rainfed lowland rice which is grown under more harsh and variable environmental regimes than irrigated lowland rice.     

Autotrophic ammonia oxidation at low pH through urea hydrolysis.

Ammonia oxidation in laboratory liquid batch cultures of autotrophic ammonia oxidizers rarely occurs at pH values less than 7, due to ionization of ammonia and the requirement for ammonium transport rather than diffusion of ammonia. Nevertheless, there is strong evidence for autotrophic nitrification in acid soils, which may be carried out by ammonia oxidizers capable of using urea as a source of ammonia. To determine the mechanism of urea-linked ammonia oxidation, a ureolytic autotrophic ammonia oxidizer, Nitrosospira sp. strain NPAV, was grown in liquid batch culture at a range of pH values with either ammonium or urea as the sole nitrogen source. Growth and nitrite production from ammonium did not occur at pH values below 7. Growth on urea occurred at pH values in the range 4 to 7.5 but ceased when urea hydrolysis was complete, even though ammonia, released during urea hydrolysis, remained in the medium. The results support a mechanism whereby urea enters the cells by diffusion and intracellular urea hydrolysis and ammonia oxidation occur independently of extracellular pH in the range 4 to 7.5. A proportion of the ammonia produced during this process diffuses from the cell and is not subsequently available for growth if the extracellular pH is less than 7. Ureolysis therefore provides a mechanism for nitrification in acid soils, but a proportion of the ammonium produced is likely to be released from the cell and may be used by other soil organisms.     

Ammonia volatilization from tropical legume mulches and green manures on unlimed and limed soils

In the humid tropics, legumes are harvested and surface applied as mulch or incorporated as green manure. Studies on N dynamics and budgets from these systems report unaccounted losses of N. Ammonia volatilization may account for a significant percentage of these unexplained N deficits. The main objectives of this study were to: 1) determine the rate and amount of ammonia volatilization from organic amendments, both incorporated (green manure) and unincorporated (mulch), 2) compare ammonia volatilization of organic amendments on both acid (unlimed) and limed soils, and 3) correlate quality, i.e. polyphenolic and lignin concentration and carbon-to-nitrogen ratio, of the organic amendments with ammonia volatilization and net N mineralization. In an incubation experiment, ammonia volatilization losses and net N mineralization were measured from fresh leaflets of 10 legumes over a three-week period. Ammonia volatilization losses for the 10 species ranged from 3.4 to 11.8% of the total N applied in the organic amendment. Lignin content was negatively correlated to ammonia volatilization. Ammonia volatilized from mulches but not green manures, on both unlimed and limed soils, suggesting that ammonia volatilization is a surface phenomenon and not affected by soil pH. Net N mineralization was affected by species and soil pH, but was unaffected by placement (green manure or mulch). For the farmer in low-input agriculture where N tends to be limiting, volatilization losses of N from legume mulch systems could be on the same order of magnitude as crop removal.     

Laboratory measurements and simulations of ammonia volatilization from urea applied to calcareous Chinese loess soils

Ammonia volatilization is the major pathway for mineral nitrogen loss in the calcareous soils of the Chinese loess plateau, with maximum losses reaching 50% of the fertilizer-N applied. A volatilization-diffusion experiment was carried out in the laboratory using a forced-draft system and soil columns of 15.5 cm depth. Urea was surface applied at rates of 210 kg N ha^-1 to a soil with 10% CaCO₃ and a pH of 7.7. The amount of ammonia volatilized as well as the concentration profiles of ammoniacal-nitrogen and soil pH in the upper 50 mm of the soil columns after 4, 7 and 10 days were measured and subsequently modelled. The mechanistic model of Rachhpal-Singh and Nye, originally developed for neutral, non-calcareous soils, was modified to include the pH-buffering action of the soil carbonates. Model parameters were independently determined or taken from the literature. Measured and predicted cumulative NH₃ losses agreed very well in the first 10 days following fertilizer application. However, in contrast to the simulations, NH₃-volatilization was still proceeding in the experiment even after 13 days, with cumulative losses reaching 60% of the applied N. In addition to the high initial soil pH, the low bulk density and high volumetric air content of the soil columns used for the experiment proved decisive for the high rates of ammonia volatilization, provoking a strong increase in the amount of ammoniacal-N diffusing towards the soil surface as gaseous NH₃. The simulations showed that due to the high soil pH, the buffering action of the soil carbonates played a comparatively smaller role.     

Biochar Effectively Reduces Ammonia Volatilization From Nitrogen-Applied Soils in Tea and Bamboo Plantations

Intensive practices in forest soils result in dramatic nitrogen (N) losses, particularly ammonia (NH₃) volatilization, to adjacent environmental areas. A soil column experiment was conducted to evaluate the effect of bamboo biochar on NH₃ volatilization from tea garden and bamboo forest soils. The results showed that biochar amendment effectively reduced NH₃ volatilization from tea garden and bamboo forest soil by 79.2% and 75.5%, respectively. The soil pH values increased by 0.53-0.61 units after biochar application. The NH₄⁺-N and total N of both soils were 13.8-29.7% and 34.0-41.9% higher under the biochar treatments than under the control treatment, respectively. In addition, the soil water contents of the two biochar-amended soils were significantly higher (P < 0.05), by 10.7-12.5%, than that of the soils without biochar amendment. Therefore, biochar mitigates NH₃ volatilization from the tested forest soils, which was due to the increases in soil NH₄⁺-N, total N and water contents after biochar amendment. Our main findings suggest that biochar addition is an effective management option for sustainable forest management.     

施用南荻生物炭对不同类型土壤氨挥发的影响

在洞庭湖区农田施用秸秆生物炭不仅能实现秸秆资源化利用,还可降低环境污染压力。本研究于2020年采用水稻盆栽试验,研究了不同南荻秸秆生物炭施用量对土壤氨挥发速率、累积氨挥发量、表面水pH值和NH₄⁺-N浓度的影响。供试土壤为第四纪红土发育的红黄泥和花岗岩发育的麻砂泥水稻土,设置6个南荻秸秆生物炭添加处理,即分别以土柱0～20 cm土壤重量的0%、1%、2%、4%、6%和8%比例添加生物炭,每盆施用复合肥200 kg N·hm^-2。结果表明: 施用生物炭导致两种土壤之间或不同生物炭处理之间的氨挥发速率和累积量均存在显著差异。麻砂泥施用生物炭处理在施肥后第2天出现氨挥发峰值,且较不施生物炭处理峰值降低了23.6%～53.4%;红黄泥氨挥发峰值出现在施肥后第7～13天,且其峰值随着生物炭添加量的增加而升高。整体上,麻砂泥土壤的氨挥发速率均高于红黄泥。麻砂泥土壤＜4%生物炭添加量能抑制土壤氨挥发速率及累积量,其中以2%处理降幅最大(46.9%),但生物炭添加对水稻生长前期表面水pH值的影响不显著;红黄泥土壤随着南荻生物炭用量的增加,表面水中pH值和NH₄⁺-N浓度增加,导致氨挥发速率及累积量增幅达1.3～10.5倍。回归分析显示,生物炭添加量是影响两种土壤氨挥发的关键因素。Elo-vich方程能较好地拟合两种土壤的氨挥发累积量随时间的变化动态,各施炭处理的相关系数均达极显著水平。总体上,对于偏中性的麻砂泥土壤,施用一定量的南荻生物炭对氨排放有一定的抑制作用,而对于酸性的红黄泥土壤,增施南荻生物炭会通过提高表面水的pH值和NH₄⁺-N浓度促进氨挥发,因此针对不同类型土壤施用南荻秸秆生物炭应注意选择适宜用量,以降低氮素损失。     

生物炭对农田土壤氨挥发的影响机制研究进展

降低土壤氨挥发量是农田生态系统中减少土壤氮素损失、提高氮肥利用率的关键途径之一。生物炭具有独特的理化性质,施入土壤后可改变土壤理化性状,影响土壤氮素循环,并对农田土壤中氨挥发产生重要的影响。本文首先介绍了稻田和旱田两种土地利用方式下农田氨挥发过程及其影响因素(气候条件、土壤环境、施肥管理等);其次,重点综述了生物炭对农田生态系统氨挥发影响的研究进展,并从物理吸附机制、气液平衡机制、生物化学过程调节机制等方面探讨了生物炭介入下农田土壤氨挥发的响应机制,认为土壤氨挥发减排的响应主要是基于生物炭表面含氧官能团对土壤NH₄⁺和NH₃的吸附作用及促进土壤硝化作用;而生物炭增加土壤氨挥发排放主要与生物炭提高土壤pH值和透气性、增强土壤有机氮矿化微生物活性有关。最后,对生物炭减少土壤氨挥发、提高氮肥利用率的研究方向进行了展望。     

曝气充氧条件下污染河道氨挥发特性模拟

以污染河道为研究对象,模拟研究污染河道在曝气充氧(底泥曝气,ES组;水曝气,EW组)条件下氨挥发的特性,探讨主要影响因素及其作用过程.研究表明,污染河道水体具有一定氨挥发潜力,在实验室模拟条件下,氨挥发速率平均为2.51mg·m-2·h-1,相当于0.50 kgN· hm-2·d-1;曝气污染河道水体的氨挥发有一定的促进作用,与对照相比(EC组)氨挥发速率和累积氨挥发量存在显著差异(P＜ 0.05);不同曝气方式对氨挥发过程影响不同,氨挥发速率存在显著差异(P＜0.05);至实验结束,EW组的累积挥发量为2809.76 mg/m2,分别是ES组和EC组的1.17和2.25倍;各实验组的氨挥发累积量用一级动力学方程能很好地拟合,根据模型可以预测氨挥发量;同一温度条件下,pH值、铵氮浓度和通气频率是影响氨挥发的主要因素;曝气可以通过增加通气频率和提高水体pH值来促进氨挥发进行;在曝气作用下随着硝化过程的进行对氨挥发有一定的限制作用;曝气条件下,氨挥发作用在硝化过程启动阶段最为明显.     

Analysis of ammonia loss mechanisms in microbial fuel cells treating animal wastewater

Ammonia losses during swine wastewater treatment were examined using single- and two-chambered microbial fuel cells (MFCs). Ammonia removal was 60% over 5 days for a single-chamber MFC with the cathode exposed to air (air-cathode), versus 69% over 13 days from the anode chamber in a two-chamber MFC with a ferricyanide catholyte. In both types of systems, ammonia losses were accelerated with electricity generation. For the air-cathode system, our results suggest that nitrogen losses during electricity generation were increased due to ammonia volatilization with conversion of ammonium ion to the more volatile ammonia species as a result of an elevated pH near the cathode (where protons are consumed). This loss mechanism was supported by abiotic tests (applied voltage of 1.1 V). In a two-chamber MFC, nitrogen losses were primarily due to ammonium ion diffusion through the membrane connecting the anode and cathode chambers. This loss was higher with electricity generation as the rate of ammonium transport was increased by charge transfer across the membrane. Ammonia was not found to be used as a substrate for electricity generation, as intermittent ammonia injections did not produce power. The ammonia-oxidizing bacterium Nitrosomonas europaea was found on the cathode electrode of the single-chamber system, supporting evidence of biological nitrification, but anaerobic ammonia-oxidizing bacteria were not detected by molecular analyses. It is concluded that ammonia losses from the anode chamber were driven primarily by physical-chemical factors that are increased with electricity generation, although some losses may occur through biological nitrification and denitrification.     

Low Nitrification Rates in Acid Scots Pine Forest Soils Are Due to pH-Related Factors

In a previous study, ammonia-oxidizing bacteria (AOB)-like sequences were detected in the fragmentation layer of acid Scots pine (Pinus sylvestris L.) forest soils (pH 2.9–3.4) with high nitrification rates (>11.0 μg g⁻¹ dry soil week⁻¹), but were not detected in soils with low nitrification rates (<0.5 μg g⁻¹ dry soil week⁻¹). In the present study, we investigated whether this low nitrification rate has a biotic cause (complete absence of AOB) or an abiotic cause (unfavorable environmental conditions). Therefore, two soils strongly differing in net nitrification were compared: one soil with a low nitrification rate (location Schoorl) and another soil with a high nitrification rate (location Wekerom) were subjected to liming and/or ammonium amendment treatments. Nitrification was assessed by analysis of dynamics in NH₄ ⁺-N and NO₃ ⁻-N concentrations, whereas the presence and composition of AOB communities were assessed by polymerase chain reaction–denaturing gradient gel electrophoresis and sequencing of the ammonia monooxygenase (amoA) gene. Liming, rather than ammonium amendment, stimulated the growth of AOB and their nitrifying activity in Schoorl soil. The retrieved amoA sequences from limed (without and with N amendment) Schoorl and Wekerom soils exclusively belong to Nitrosospira cluster 2. Our study suggests that low nitrification rates in acidic Scots pine forest soils are due to pH-related factors. Nitrosospira cluster 2 detected in these soils is presumably a urease-positive cluster type of AOB.     

Mineralization and gaseous losses of nitrogen from urea and ammonium sulphate in salt-affected soils

Summary An incubation study on mineralization and gaseous losses of nitrogen was conducted on three soils with increasing levels (1.1 to 50 mmhos/cm) of salinity and two levels of urea and ammonium sulphate upto 6 weeks. Mineralization of nitrogen increased with time and decreased with the increase of salinity. It was more from ammonium sulphate than urea, and relatively more from the lower dose. The gaseous losses of NH₄-N increased with salinity. About 35±5 per cent of added N was lost in the gaseous form at maximum (ECe=45 to 50 mmhos/cm) salinity and losses were more from light than heavier soils. Salinity and pH, both were correlated negatively with the N mineralisation and positively with the gaseous losses of ammonia in these salt-affected soils. re]19751105     

Ammonium Nutrition as a Strategy for Cadmium Mobilisation in the Rhizosphere of Sunflower

Ammonium nutrition of higher plants results in rhizosphere acidification due to proton excretion by root cells. The acidification induced by ammonium-fed plants can be exploited to promote a localised metal mobilisation in neutral to alkaline polluted soils and therefore to improve phytoextraction. The effects of ammonium uptake by sunflower (Helianthus annuus L.) plants on the external medium pH, aerial and root growth and tolerance to soluble Cd were studied in hydroponic culture. The ammonium-fed sunflowers induced a strong acidification of the solution and, compared to the nitrate-fed sunflowers, a small modification in mineral nutrition and a different Cd partitioning between root and shoot. Moreover, ammonium nutrition was found to induce a great mobilisation of a sparingly soluble form of cadmium (CdCO₃). A pot experiment studied the ability of different ammonium-based fertilisers (ammonium sulphate, ammonium thiosulphate, urea) to modify bulk and rhizo-soil pH, compared to the effect of calcium nitrate and to the unfertilised soil. Furthermore, in order to promote the persistence of ammonium in soil, a combined treatment of ammonium sulphate and DMPP, a nitrification inhibitor, was tested. Soil pH was strongly modified by chemical and biological processes involved in fertiliser transformations. In particular, due to nitrification, all ammonium-based treatments showed a bulk soil acidification of over 1.5 pH units and a relative increase in rhizo-soil pH as a consequence of nitrate uptake. The treatment with DMPP showed an opposite trend with a lower pH in rhizo-soil than in bulk soil. The ability of ammonium-fed plants to mobilise heavy metals from the non-labile pool was studied in another pot experiment using three soils with different properties and at different degree and type of heavy metal contamination. Whatever the soil, the metal concentrations in shoots were higher in plants fed with ammonium (ammonium sulphate plus DMPP treatment). Our results support the hypothesis that ammonium nutrition with nitrification inhibitors is a viable strategy to improve heavy metals phytoextraction while protecting bulk soil from acidification and presumably from metal leaching. An erratum to this article is available at .     

川西亚高山针叶林不同恢复阶段土壤的硝化和反硝化作用

 采用气压过程分离(Barometric process separation, BaPS)技术对川西亚高山针叶林不同恢复 阶段土壤的总硝化和反硝化作用速率进行了测定,结果表明：川西亚高山针叶林不同恢复阶段土壤的总硝化和反硝化速率差异不显著(p<0.05),不同恢复阶段土壤总硝化作用的 Q10值 差异不显著(p<0.05);总硝化作用速率与土壤含水量呈显著正相关(p<0.05),与土 壤pH值、 土壤有机质、全氮及C/N相关不显著;不同恢复阶段土壤反硝化速率均维持在一个较低的水 平,反硝化速率与土壤中的C/N显著正相关(p<0.05),与土壤含水量、pH值、有机质及全氮相关不显著。与反硝化作用相比,硝化作用对亚高山针叶林土壤氮损失的影响可能更大