Soil nitrification is mediated by ammonia-oxidizing archaea (AOA) and bacteria (AOB), which occupy different specialized ecological niches. However, little is known about the diversification of AOA and AOB communities...Soil nitrification is mediated by ammonia-oxidizing archaea (AOA) and bacteria (AOB), which occupy different specialized ecological niches. However, little is known about the diversification of AOA and AOB communities in a large geographical scale. Here, eight paddy soils collected from different geographic regions in China were selected to investigate the spatial distribution of AOA and AOB, and their potential nitrification activity (PNA). The result showed that the abundance of AOA was predominant over AOB, indicating that the rice fields favor the growth of AOA. PNA highly varied from 0.43 to 3.57 μg NOX-N·g·dry·soil·h-1, and was positively related with soil NH3 content, the abundance of AOA community, and negatively related with the diversity of AOB community (P amoA genes revealed remarkable differences in the compositions of AOA and AOB community. Phylogenetic analyses of amoA genes showed that Nitrosospiracluster-3-like and Nitrosomonas cluster 7-like AOB extensively dominated the AOB communities, and 54d9-like AOA within the soil group 1.1b predominated in AOA communities in paddy soils. Redundancy analysis suggested that the spatial variations of AOA community structure were influenced by soil TN content (P < 0.01), while no significant correlation between AOB community structure and soil properties was found. Findings highlight that ammonia oxidizers exhibit spatial variations in complex paddy fields due to the joint influence of soil variables associated with N availability.展开更多
The diversification of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) communities and their potential nitrification activity (PNA) on a large scale have not been well documented. In this work, se...The diversification of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) communities and their potential nitrification activity (PNA) on a large scale have not been well documented. In this work, seven paddy soils from different geographic regions in Sichuan, P. R. China were selected to determine the spatial distribution of the activities, abundances and community compositions of AOB and AOA. PNA varied greatly among paddy soils, and was positively correlated with soil pH (P< 0.05). The abundance of AOA was 81.1 to 1 670.0 times more than that of AOB, which indicates paddy soil environments favor the growth of AOA. Denaturing gradient gel electrophoresis fingerprints of amoA genes exhibited distinct spatial differences in AOA compositions rather than in AOB compositions. Sequencing analysis revealed that acidic soils were dominated by AOA within marine group 1.1 a-associated lineage, whereas the soil group 1.1b lineage AOA predominated in neutral and alkaline soils. Both nitrosopira cluster 3-like and Nitrosomonas cluster 7-like AOB dominated the AOB communities in the paddy soils. Redundancy analysis suggested that soil NH4^+-N content was the most significant driver determining the AOB community structure, while no significant correlation between AOA community structure and soil properties was found. The findings highlight that the activity and composition of ammonia oxidizers exhibit spatial variations in complex paddy fields due to the joint influence of soil variables associated with pH and N availability.展开更多
Nitrogen（N） loss from fertilization in agricultural fields has an unavoidable negative impact on the environment and a better understanding of the major pathways can assist in developing the best management practice...Nitrogen（N） loss from fertilization in agricultural fields has an unavoidable negative impact on the environment and a better understanding of the major pathways can assist in developing the best management practices. The aim of this study was to evaluate the fate of N fertilizers applied to acidic red soil（Ferralic Cambisol） after 19 years of mineral（synthetic） and manure fertilizer treatments under a cropping system with wheat-maize rotations. Five field treatments were examined： control（CK）, chemical nitrogen and potash fertilizer（NK）, chemical nitrogen and phosphorus fertilizer（NP）, chemical nitrogen, phosphorus and potash fertilizer（NPK） and the NPK with manure（NPKM, 70% N from manure）. Based on the soil total N storage change in 0–100 cm depth, ammonia（NH_3） volatilization, nitrous oxide（N_2O） emission, N plant uptake, and the potential N leaching loss were estimated using a mass balance approach. In contrast to the NPKM, all mineral fertilizer treatments（NK, NP and NPK） showed increased nitrate（NO_3~–） concentration with increasing soil depth, indicating higher leaching potential. However, total NH_3 volatilization loss was much higher in the NPKM（19.7%） than other mineral fertilizer treatments（≤4.2%）. The N_2O emissions were generally low（0.2–0.9%, the highest from the NPKM）. Total gaseous loss accounted for 1.7, 3.3, 5.1, and 21.9% for NK, NP, NPK, and NPKM treatments, respectively. Estimated N leaching loss from the NPKM was only about 5% of the losses from mineral fertilizer treatments. All data demonstrated that manure incorporation improved soil productivity, increased yield, and reduced potential leaching, but with significantly higher NH_3 volatilization, which could be reduced by improving the application method. This study confirms that manure incorporationis an essential strategy in N fertilization management in upland red soil cropping system.展开更多
In this study, we investigated the potential nitrification and community structure of soil-based ammonia-oxidizing bacteria （AOB） in apple orchard soil during different growth periods and explored the effects of env...In this study, we investigated the potential nitrification and community structure of soil-based ammonia-oxidizing bacteria （AOB） in apple orchard soil during different growth periods and explored the effects of environmental factors on nitrification activity and AOB community composition in the soil of a Hanfu apple orchard, using a culture-dependent technique and denaturing gradient gel electrophoresis （DGGE）. We observed that nitrification activity and AOB abundance were the highest in November, lower in May, and the lowest in July. The results of statistical analysis indicated that total nitrogen （N） content, NH4＋-N content, NO3-N content, and pH showed significant correlations with AOB abundance and nitrification activity in soil. The Shannon-Winner diversity, as well as species richness and evenness indices （determined by PCR-DGGE banding patterns） in soil samples were the highest in September, but the lowest in July, when compared to additional sampled dates. The DGGE fingerprints of soil-based 16S rRNA genes in November were apparently distinct from those observed in May, July, and September, possessing the lowest species richness indices and the highest dominance indices among all four growth periods. Fourteen DGGE bands were excised for sequencing. The resulting analysis indicated that all AOB communities belonged to the 13-Proteobacteria phylum, with the dominant AOB showing high similarity to the Nitrosospira genus. Therefore, soil-based environmental factors, such as pH variation and content of NHa＋-N and NO3--N, can substantially influence the abundance of AOB communities in soil, and play a critical role in soil-based nitrification kinetics.展开更多
Metagenomic studies have demonstrated the existence of ammonia-oxidizing archaea(AOA) and revealed they are responsible for ammoxidation in some extreme environments. However, the changes in compositional structure an...Metagenomic studies have demonstrated the existence of ammonia-oxidizing archaea(AOA) and revealed they are responsible for ammoxidation in some extreme environments. However, the changes in compositional structure and ammonia-oxidation capacity of AOA communities in biological soil crusts(BSCs) of desert ecosystems remain poorly understood.Here, we utilized Illumina MiSeq sequencing and microbial functional gene array(GeoChip 5.0) to assess the above changes along a 51-year revegetation chronosequence in the Tengger Desert, China. The results showed a significant difference in AOA-community richness between 5-year-old BSCs and older ones. The most dominant phylum during BSC development was Crenarchaeota, and the corresponding species were ammonia-oxidizing_Crenarchaeote and environmental_samples_Crenarchaeota. Network analysis revealed that the positive correlations among dominant taxa increased, and their cooperation was reinforced in AOA communities during BSC succession. Redundancy analysis showed that the dominant factor influencing the change in AOA-community structure was soil texture. GeoChip 5.0 indicated that the amoA gene abundances of AOA and ammonia-oxidizing bacteria(AOB) were basically the same, demonstrating that AOA and AOB played an equally important role during BSCs development. Our study of the long-term succession of BSC demonstrated a persistent response of AOA communities to revegetation development in desert ecosystems.展开更多
The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and tra...The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and transformation rules of ammonia-nitrogen in three typical types of sand soil using the indoor leaching experiment of soil column, and then makes comparison with the indoor experiment results in combination with the numerical simulation method. The experiment process shows that the change in ammonia-nitrogen concentration goes through three stages including "removal-water saturation-saturation". As the contents of clay particles in soil sample increase, the removal of ammonia-nitrogen from soil sample will take more time and gain higher ratio. During the removal period, the removal ratio of Column 1, Column 2 and Column 3 averages 68.8%(1-12 d), 74.6%(1-22 d) and 91.1%(1-26 d). The ammonia-nitrogen removal ratio shows no noticeable change as the depth of soil columns varies. But it is found that the ammonia-nitrogen removal ratio is the least of the whole experiment when the soil columns are at the depth of 15 cm. It can be preliminary inferred that the natural purifying performance of soil along the river for ammonia-nitrogen in river water mainly depends on the proportion of fine particles in soil. HYDRUS-1D model is used to simulate this experiment process, analyze the change of the bottom observation holes by time and depth in three columns(the tenth day), and make comparison with the experiment result. The coefficients of determination for fitting curves of Column 1, Column 2 and Column 3 are 0.953, 0.909, 0.882 and 0.955, 0.740, 0.980 separately. Besides, this paper examines the contribution of absorption, mineralization and nitrification in the simulation process. In the early removal stage, mineralization plays a dominant role and the maximum contribution rate of mineralization is 99%. As time goes by, absorption starts to function and gradually assumes a dominant position. In the middle and late removal stage, nitrification in Column 1 and Column 2 makes more contribution than mineralization. So the experiment result of the ammonia-nitrogen concentration is 0.6% and 2.4% lower than that in effluent and the maximum contribution ratio of nitrification is -4.53% and -5.10% respectively when only the function of absorption is considered. The mineralization in Column 1 and Column 2 in the middle and late removal stage still plays a more important role than nitrification. So the experiment result is 1.4% higher than that in effluent and the maximum contribution ratio of nitrification is -2.51% when only the function of absorption is considered. Therefore, absorption, mineralization and nitrification make different contributions during different part of the stage. This means that the natural purifying performance of soil along the river for ammonia-nitrogen in river water not only depends on the proportion of fine particles in soil, but depends on the mineralization and nitrification environment. This can offer some insights into the protection and recovery of groundwater along the riverbank.展开更多
Ammonia oxidation, the first and rate-limiting step of nitrification, is carried out by both ammonia-oxidizing bacteria （AOB） and ammonia-oxidizing archaea （AOA）. However, the relative importance of AOB and AOA to...Ammonia oxidation, the first and rate-limiting step of nitrification, is carried out by both ammonia-oxidizing bacteria （AOB） and ammonia-oxidizing archaea （AOA）. However, the relative importance of AOB and AOA to nitrification in terrestrial ecosystems is not well understood. The aim of this study was to investigate the effect of the nitrogen input amount on abundance and community composition of AOB and AOA in red paddy soil. Soil samples of 10-20 cm （root layer soil） and 0-5 cm （surface soil） depths were taken from a red paddy. Rice in the paddy was fertilized with different rates of N as urea of N1 （75 kg N ha＂ yr-1）, N2 （150 kg N ha~ yrl）, N3 （225 kg N ha1 yrl） and CK （without fertilizers） in 2009, 2010 and 2011. Abundance and community composition of ammonia oxidizers was analyzed by real-time PCR and denaturing gradient gel electrophoresis （DGGE） based on amoA （the unit A of ammonia monooxygenase） gene. Archaeal amoA copies in N3 and N2 were significantly （P〈0.05） higher than those in CK and N1 in root layer soil or in surface soil under tillering and heading stages of rice, while the enhancement in bacterial amoA gene copies with increasing of N fertilizer rates only took on in root layer soil. N availability and soil NO3--N content increased but soil NH4＋-N content didn＇t change with increasing of N fertilizer rates. Otherwise, the copy numbers of archaeal amoA gene were higher （P〈0.05） than those of bacterial amoA gene in root lary soil or in surface soil. Redundancy discriminate analysis based on DGGE bands showed that there were no obvious differs in composition of AOA or AOB communities in the field among different N fertilizer rates. Results of this study suggested that the abundance of ammonia-oxidizers had active response to N fertilizer rates and the response of AOA was more obvious than that of AOB. Similarity in the community composition of AOA or AOB among different N fertilizer rates indicate that the community composition of ammonia-oxidizers was relatively stable in the paddy soil at least in short term for three years.展开更多
Vertical occurrence of soil urease activity along with ammonia content from three distinct regions viz. Deep forest region (No tidal action and wave attack occurs as it is furthest from river shore and it contains max...Vertical occurrence of soil urease activity along with ammonia content from three distinct regions viz. Deep forest region (No tidal action and wave attack occurs as it is furthest from river shore and it contains maximum content of organic carbon and minimum soil salinity and silicate concentration. In this zone plenty of pneumatophores, below ground root and dense vegetation are found), Rooted region (It is situated in between Deep forest region and Un-rooted region. This region contains only pneumatophores but it is devoid of long roots and vegetations. It faces wave attack and tidal action less than that of Un-rooted region) and Un-rooted region (It is closest to river shore and faces maximum wave attack and tidal action;it contains minimum organic carbon but maximum soil salinity and silicate concentration. This zone is totally devoid of any roots, pneumatophores and vegetations) of Sundarban mangrove forest ecosystem, India revealed an interesting explanation. Soil urease activity showed a decreasing pattern with increase in depth from the deep forest region of the Sundarban forest ecosystem. Soil urease activity was found to be more sensitive to soil temperature and pH rather than soil salinity. This ensured that soil urease along with the microbes present in the Sundarban forest ecosystem are more tolerant to fluctuation in salinity than that of temperature. Soil ammonia concentration was found to be directly governed by the soil urease activity [The regression equation is Ammonia in soil = -1.64 + 0.0402 Urease Activity (R-Sq = 62.9%, P < 0.001, n = 41)].展开更多
A red soil, a fluvo-aquic soil and a permeable paddy soil were used in a long-term investigation to study changes in nitrification with treatments: 1) soil incubation, 2) liquid incubation inoculated with soil samples...A red soil, a fluvo-aquic soil and a permeable paddy soil were used in a long-term investigation to study changes in nitrification with treatments: 1) soil incubation, 2) liquid incubation inoculated with soil samples, and 3) liquid incubation inoculated with ammonia-oxidizing bacteria (AOB) from the soils. There were significant differences (P < 0.001) in nitrification rates among the three soils when measured for 28 days by adding (NH4)SO4 at the rate of 154 mg N kg-1 dry soil to fresh soil. However, the amounts of nitrifying bacteria in the three soils were not related to soil nitrification capacity. When the soil samples or the isolates of AOB enriched from the corresponding soil were incubated in liquid with pH 5.8, 7.0 and 8.0 buffers and 10 mmol L-1 ammonium nitrogen, there were no significant nitrification differences in the same soil type at each pH. The ability to oxidize ammonia through AOB from different types of soils in a homogeneous culture medium was similar, and the soil nitrification capacity could reflect the inherent properties of a soil. Altering the culture medium pH of individual soil type also showed that acidification of an alkaline fluvo-aquic soil decreased nitrification capacity, whereas alkalinization of the acidic red soil and permeable paddy soil increased their nitrification. For a better insight into factors influencing soil nitrification processes, soil properties including texture and clay composition should be considered.展开更多
We conducted field trials of rice grown in sandy soil and clay soil to determine the effects of nitrogen application levels on the concentration of NH4＋-N in surface water, loss of ammonia through volatilization from...We conducted field trials of rice grown in sandy soil and clay soil to determine the effects of nitrogen application levels on the concentration of NH4＋-N in surface water, loss of ammonia through volatilization from paddy fields, rice production, nitrogen-use efficiency, and nitrogen content in the soil profile. The concentration of NH4＋-N in surface water and the amount of ammonia lost through volatilization increased with increasing nitrogen application level, and peaked at 1-3 d after nitrogen application. Less ammonia was lost via volatilization from clay soil than from sandy soil. The amounts of ammonia lost via volatilization after nitrogen application differed depending on the stage when it was applied, from the highest loss to the lowest： N application to promote tillering 〉 the first N topdressing to promote panicle initiation （applied at the last 4-leaf stage） 〉 basal fertilizer 〉 the second N topdressing to promote panicle initiation （applied at the last 2-leaf stage）. The total loss of ammonia via volatilization from clay soil was 10.49-87.06 kg/hm2, equivalent to 10.92%-21.76% of the nitrogen applied. The total loss of ammonia via volatilization from sandy soil was 11.32-102.43 kg/hm2, equivalent to 11.32%-25.61 % of the nitrogen applied. The amount of ammonia lost via volatilization and the concentration of NH4＋-N in surface water peaked simultaneously after nitrogen application; both showed maxima at the tillering stage with the ratio between them ranging from 23.76% to 33.65%. With the increase in nitrogen application level, rice production and nitrogen accumulation in plants increased, but nitrogen-use efficiency decreased. Rice production and nitrogen accumulation in plants were slightly higher in clay soil than in sandy soil. In the soil, the nitrogen content was the lowest at a depth of 40-50 cm. In any specific soil layer, the soil nitrogen content increased with increasing nitrogen application level, and the soil nitrogen content was higher in clay soil than in sandy soil. In terms of ammonia volatilization, the amount of ammonia lost via volatilization increased markedly when the nitrogen application level exceeded 250 kg/hm2 in the rice growing season. However, for rice production, a suitable nitrogen application level is approximately 300 kg/hm2. Therefore, taking the needs for high crop yields and environmental protection into account, the appropriate nitrogen application level was 250-300 kg/hm2 in these conditions.展开更多
The upland agricultural soils in North China are distributed north of a line between the Kunlun Mountains, the Qinling Mountains and the Huaihe River. They occur in arid, semi-arid and semi-humid regions and crop prod...The upland agricultural soils in North China are distributed north of a line between the Kunlun Mountains, the Qinling Mountains and the Huaihe River. They occur in arid, semi-arid and semi-humid regions and crop production often depends on rain-fed or irrigation to supplement rainfall. This paper summarizes the characteristics of gross nitrogen（N） transformation, the fate of N fertilizer and soil N as well as the N loss pathway, and makes suggestions for proper N management in the region. The soils of the region are characterized by strong N mineralization and nitrification, and weak immobilization and denitrification ability, which lead to the production and accumulation of nitrate in the soil profile. Large amounts of accumulated nitrate have been observed in the vadose-zone in soils due to excess N fertilization in the past three decades, and this nitrate is subject to occasional leaching which leads to groundwater nitrate contamination. Under farmer＇s conventional high N fertilization practice in the winter wheat-summer maize rotation system（N application rate was approximately 600 kg ha–1 yr–1）, crop N uptake, soil residual N, NH_3 volatilization, NO_3~– leaching, and denitrification loss accounted for around 27, 30, 23, 18 and 2% of the applied fertilizer N, respectively. NH_3 volatilization and NO_3~– leaching were the most important N loss pathways while soil residual N was an important fate of N fertilizer for replenishing soil N depletion from crop production. The upland agricultural soils in North China are a large source of N_2O and total emissions in this region make up a large proportion（approximately 54%） of Chinese cropland N_2O emissions. The “non-coupled strong ammonia oxidation” process is an important mechanism of N_2O production. Slowing down ammonia oxidation after ammonium-N fertilizer or urea application and avoiding transient high soil NH4＋ concentrations are key measures for reducing N_2O emissions in this region. Further N management should aim to minimize N losses from crop and livestock production, and increase the recycling of manure and straw back to cropland. We also recommend adoption of the 4 R（Right soure, Right rate, Right time, Right place） fertilization techniques to realize proper N fertilizer management, and improving application methods or modifying fertilizer types to reduce NH_3 volatilization, improving water management to reduce NO_3~– leaching, and controlling the strong ammonia oxidation process to abate N_2O emission. Future research should focus on the study of the trade-off effects among different N loss pathways under different N application methods or fertilizer products.展开更多
响应到稻田的脲申请的氨挥发损失，氮利用效率，和米饭收益在 Wangzhuang 镇上被调查， Changshu 城市，江苏省，中国。N 化肥处理，适用在三倍，是 0 (控制) ， 100， 200， 300，或 350 kg N 哈 ? 1。在脲被用于地面水以后，一个连续...响应到稻田的脲申请的氨挥发损失，氮利用效率，和米饭收益在 Wangzhuang 镇上被调查， Changshu 城市，江苏省，中国。N 化肥处理，适用在三倍，是 0 (控制) ， 100， 200， 300，或 350 kg N 哈 ? 1。在脲被用于地面水以后，一个连续气流包围方法被用来在稻田测量氨挥发。通过氨挥发的全部的 N 损失通常与 N 申请率，和申请评估的二更高的 N 增加了(300 和 350 kg N 哈 ? 1 ) 证明 N 的更高的比率通过氨挥发输了到应用 N。由在全部米饭期间，生长上演的氨挥发的全部的氨损失从 9.0% ～ 16.7% 应用 N 。增加申请率通常减少了在到在植物的 N 的种子的 N 的比率。为所有 N 处理，氮肥利用效率从 30.9% ～ 45.9%。有最高的 N 率的剩余 N 导致了米饭植物，氮肥利用的减少的率，和减少的米饭收益的住宿。从这个实验计算，最节俭的 N 化肥申请率是 227 kg 哈 ? 1 为在泰胡·莱克区域的水稻土的类型。然而，推荐适当 N 化肥申请率以便植物生长被提高，氨损失被减少能改进大米的 N 利用效率。展开更多
Field experiments were conducted in 2006 to investigate the impacts of modified rice cultivation systems on: grain yield, N uptake, ammonia volatilization from rice soil and N use efficiency (ANUE, agronomic N use eff...Field experiments were conducted in 2006 to investigate the impacts of modified rice cultivation systems on: grain yield, N uptake, ammonia volatilization from rice soil and N use efficiency (ANUE, agronomic N use efficiency;and PFP, partial factor productivity of applied N). The trials compared rice production using modified methods of irrigation, planting, weeding and nutrient management (the system of rice intensification, SRI) with traditional flooding (TF). The effects of different N application rates (0, 80, 160, 240 kg ha-1) and of N rates interacting with cultivation methods were also evaluated. Grain yields ranged from 5.6 to 6.9 t ha-1 with SRI, and from 4.0 to 6.1 t ha-1 under TF management. On average, grain yields under SRI were 24% higher than that with TF. Ammonia volatilization was increased significantly under SRI compared with TF and the average total amount of ammonia volatilization loss during the rice growth stage under SRI was 22% higher than TF. With increases in application rate, N uptake by rice increased, and the ratio of N in the seed to total N in the plant decreased. Furthermore, results showed that higher ANUE was achieved at a relatively low N fertilizer rate (80 kg ha-1 N) with SRI. Results of these studies suggest that SRI increased rice yield and N uptake and improved ammonia volatilization loss from rice soil compared with TF. Moreover, there were significant interactions between N application rates and cultivation methods. We conclude that it was the most important to adjust the amount of N application under SRI, such as reducing the amount of N application. Research on effects of N fertilizer on rice yield and environmental pollution under SRI may be worth further studying.展开更多
文摘Soil nitrification is mediated by ammonia-oxidizing archaea (AOA) and bacteria (AOB), which occupy different specialized ecological niches. However, little is known about the diversification of AOA and AOB communities in a large geographical scale. Here, eight paddy soils collected from different geographic regions in China were selected to investigate the spatial distribution of AOA and AOB, and their potential nitrification activity (PNA). The result showed that the abundance of AOA was predominant over AOB, indicating that the rice fields favor the growth of AOA. PNA highly varied from 0.43 to 3.57 μg NOX-N·g·dry·soil·h-1, and was positively related with soil NH3 content, the abundance of AOA community, and negatively related with the diversity of AOB community (P amoA genes revealed remarkable differences in the compositions of AOA and AOB community. Phylogenetic analyses of amoA genes showed that Nitrosospiracluster-3-like and Nitrosomonas cluster 7-like AOB extensively dominated the AOB communities, and 54d9-like AOA within the soil group 1.1b predominated in AOA communities in paddy soils. Redundancy analysis suggested that the spatial variations of AOA community structure were influenced by soil TN content (P < 0.01), while no significant correlation between AOB community structure and soil properties was found. Findings highlight that ammonia oxidizers exhibit spatial variations in complex paddy fields due to the joint influence of soil variables associated with N availability.
基金Funded by the National Natural Science Foundation of China (No.41606142)the Fundamental Research Funds of China West Normal University (No.463140 and No.412554)
文摘The diversification of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) communities and their potential nitrification activity (PNA) on a large scale have not been well documented. In this work, seven paddy soils from different geographic regions in Sichuan, P. R. China were selected to determine the spatial distribution of the activities, abundances and community compositions of AOB and AOA. PNA varied greatly among paddy soils, and was positively correlated with soil pH (P< 0.05). The abundance of AOA was 81.1 to 1 670.0 times more than that of AOB, which indicates paddy soil environments favor the growth of AOA. Denaturing gradient gel electrophoresis fingerprints of amoA genes exhibited distinct spatial differences in AOA compositions rather than in AOB compositions. Sequencing analysis revealed that acidic soils were dominated by AOA within marine group 1.1 a-associated lineage, whereas the soil group 1.1b lineage AOA predominated in neutral and alkaline soils. Both nitrosopira cluster 3-like and Nitrosomonas cluster 7-like AOB dominated the AOB communities in the paddy soils. Redundancy analysis suggested that soil NH4^+-N content was the most significant driver determining the AOB community structure, while no significant correlation between AOA community structure and soil properties was found. The findings highlight that the activity and composition of ammonia oxidizers exhibit spatial variations in complex paddy fields due to the joint influence of soil variables associated with pH and N availability.
基金supported by the National Key Research and Development Program of China(2016YFD0200301)the open fund of Key Laboratory of Non-point Source Pollution Control,Ministry of Agriculture,China(20130104)the Key Technologies R&D Program of China during the 12th Five-year Plan period(2012BAD14B04)
文摘Nitrogen（N） loss from fertilization in agricultural fields has an unavoidable negative impact on the environment and a better understanding of the major pathways can assist in developing the best management practices. The aim of this study was to evaluate the fate of N fertilizers applied to acidic red soil（Ferralic Cambisol） after 19 years of mineral（synthetic） and manure fertilizer treatments under a cropping system with wheat-maize rotations. Five field treatments were examined： control（CK）, chemical nitrogen and potash fertilizer（NK）, chemical nitrogen and phosphorus fertilizer（NP）, chemical nitrogen, phosphorus and potash fertilizer（NPK） and the NPK with manure（NPKM, 70% N from manure）. Based on the soil total N storage change in 0–100 cm depth, ammonia（NH_3） volatilization, nitrous oxide（N_2O） emission, N plant uptake, and the potential N leaching loss were estimated using a mass balance approach. In contrast to the NPKM, all mineral fertilizer treatments（NK, NP and NPK） showed increased nitrate（NO_3~–） concentration with increasing soil depth, indicating higher leaching potential. However, total NH_3 volatilization loss was much higher in the NPKM（19.7%） than other mineral fertilizer treatments（≤4.2%）. The N_2O emissions were generally low（0.2–0.9%, the highest from the NPKM）. Total gaseous loss accounted for 1.7, 3.3, 5.1, and 21.9% for NK, NP, NPK, and NPKM treatments, respectively. Estimated N leaching loss from the NPKM was only about 5% of the losses from mineral fertilizer treatments. All data demonstrated that manure incorporation improved soil productivity, increased yield, and reduced potential leaching, but with significantly higher NH_3 volatilization, which could be reduced by improving the application method. This study confirms that manure incorporationis an essential strategy in N fertilization management in upland red soil cropping system.
基金the National Natural Science Foundation of China(31101504 and 31171917)the Postdoctoral Science Foundation of China(2011M500575)+1 种基金the China Agricultural Research System(CARS-28)the Shenyang Municipal Science and Technology Research Projects,China(F12-109-3-00)for their financial support
文摘In this study, we investigated the potential nitrification and community structure of soil-based ammonia-oxidizing bacteria （AOB） in apple orchard soil during different growth periods and explored the effects of environmental factors on nitrification activity and AOB community composition in the soil of a Hanfu apple orchard, using a culture-dependent technique and denaturing gradient gel electrophoresis （DGGE）. We observed that nitrification activity and AOB abundance were the highest in November, lower in May, and the lowest in July. The results of statistical analysis indicated that total nitrogen （N） content, NH4＋-N content, NO3-N content, and pH showed significant correlations with AOB abundance and nitrification activity in soil. The Shannon-Winner diversity, as well as species richness and evenness indices （determined by PCR-DGGE banding patterns） in soil samples were the highest in September, but the lowest in July, when compared to additional sampled dates. The DGGE fingerprints of soil-based 16S rRNA genes in November were apparently distinct from those observed in May, July, and September, possessing the lowest species richness indices and the highest dominance indices among all four growth periods. Fourteen DGGE bands were excised for sequencing. The resulting analysis indicated that all AOB communities belonged to the 13-Proteobacteria phylum, with the dominant AOB showing high similarity to the Nitrosospira genus. Therefore, soil-based environmental factors, such as pH variation and content of NHa＋-N and NO3--N, can substantially influence the abundance of AOB communities in soil, and play a critical role in soil-based nitrification kinetics.
基金supported financially by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDA2003010301)the National Natural Science Foundation of China (Grant No. 41621001)
文摘Metagenomic studies have demonstrated the existence of ammonia-oxidizing archaea(AOA) and revealed they are responsible for ammoxidation in some extreme environments. However, the changes in compositional structure and ammonia-oxidation capacity of AOA communities in biological soil crusts(BSCs) of desert ecosystems remain poorly understood.Here, we utilized Illumina MiSeq sequencing and microbial functional gene array(GeoChip 5.0) to assess the above changes along a 51-year revegetation chronosequence in the Tengger Desert, China. The results showed a significant difference in AOA-community richness between 5-year-old BSCs and older ones. The most dominant phylum during BSC development was Crenarchaeota, and the corresponding species were ammonia-oxidizing_Crenarchaeote and environmental_samples_Crenarchaeota. Network analysis revealed that the positive correlations among dominant taxa increased, and their cooperation was reinforced in AOA communities during BSC succession. Redundancy analysis showed that the dominant factor influencing the change in AOA-community structure was soil texture. GeoChip 5.0 indicated that the amoA gene abundances of AOA and ammonia-oxidizing bacteria(AOB) were basically the same, demonstrating that AOA and AOB played an equally important role during BSCs development. Our study of the long-term succession of BSC demonstrated a persistent response of AOA communities to revegetation development in desert ecosystems.
基金supported by Special Scientific Research Expenditure for Public Charity Industry of Ministry of Water Resources(No.201501008)Institute of Resources and Environment of North China University of Water Resources and Electric Power
文摘The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and transformation rules of ammonia-nitrogen in three typical types of sand soil using the indoor leaching experiment of soil column, and then makes comparison with the indoor experiment results in combination with the numerical simulation method. The experiment process shows that the change in ammonia-nitrogen concentration goes through three stages including "removal-water saturation-saturation". As the contents of clay particles in soil sample increase, the removal of ammonia-nitrogen from soil sample will take more time and gain higher ratio. During the removal period, the removal ratio of Column 1, Column 2 and Column 3 averages 68.8%(1-12 d), 74.6%(1-22 d) and 91.1%(1-26 d). The ammonia-nitrogen removal ratio shows no noticeable change as the depth of soil columns varies. But it is found that the ammonia-nitrogen removal ratio is the least of the whole experiment when the soil columns are at the depth of 15 cm. It can be preliminary inferred that the natural purifying performance of soil along the river for ammonia-nitrogen in river water mainly depends on the proportion of fine particles in soil. HYDRUS-1D model is used to simulate this experiment process, analyze the change of the bottom observation holes by time and depth in three columns(the tenth day), and make comparison with the experiment result. The coefficients of determination for fitting curves of Column 1, Column 2 and Column 3 are 0.953, 0.909, 0.882 and 0.955, 0.740, 0.980 separately. Besides, this paper examines the contribution of absorption, mineralization and nitrification in the simulation process. In the early removal stage, mineralization plays a dominant role and the maximum contribution rate of mineralization is 99%. As time goes by, absorption starts to function and gradually assumes a dominant position. In the middle and late removal stage, nitrification in Column 1 and Column 2 makes more contribution than mineralization. So the experiment result of the ammonia-nitrogen concentration is 0.6% and 2.4% lower than that in effluent and the maximum contribution ratio of nitrification is -4.53% and -5.10% respectively when only the function of absorption is considered. The mineralization in Column 1 and Column 2 in the middle and late removal stage still plays a more important role than nitrification. So the experiment result is 1.4% higher than that in effluent and the maximum contribution ratio of nitrification is -2.51% when only the function of absorption is considered. Therefore, absorption, mineralization and nitrification make different contributions during different part of the stage. This means that the natural purifying performance of soil along the river for ammonia-nitrogen in river water not only depends on the proportion of fine particles in soil, but depends on the mineralization and nitrification environment. This can offer some insights into the protection and recovery of groundwater along the riverbank.
基金the National Natural Science Foundation of China(40801097)the Natural Science Foundation of Fujian Province,China(2012J01107)
文摘Ammonia oxidation, the first and rate-limiting step of nitrification, is carried out by both ammonia-oxidizing bacteria （AOB） and ammonia-oxidizing archaea （AOA）. However, the relative importance of AOB and AOA to nitrification in terrestrial ecosystems is not well understood. The aim of this study was to investigate the effect of the nitrogen input amount on abundance and community composition of AOB and AOA in red paddy soil. Soil samples of 10-20 cm （root layer soil） and 0-5 cm （surface soil） depths were taken from a red paddy. Rice in the paddy was fertilized with different rates of N as urea of N1 （75 kg N ha＂ yr-1）, N2 （150 kg N ha~ yrl）, N3 （225 kg N ha1 yrl） and CK （without fertilizers） in 2009, 2010 and 2011. Abundance and community composition of ammonia oxidizers was analyzed by real-time PCR and denaturing gradient gel electrophoresis （DGGE） based on amoA （the unit A of ammonia monooxygenase） gene. Archaeal amoA copies in N3 and N2 were significantly （P〈0.05） higher than those in CK and N1 in root layer soil or in surface soil under tillering and heading stages of rice, while the enhancement in bacterial amoA gene copies with increasing of N fertilizer rates only took on in root layer soil. N availability and soil NO3--N content increased but soil NH4＋-N content didn＇t change with increasing of N fertilizer rates. Otherwise, the copy numbers of archaeal amoA gene were higher （P〈0.05） than those of bacterial amoA gene in root lary soil or in surface soil. Redundancy discriminate analysis based on DGGE bands showed that there were no obvious differs in composition of AOA or AOB communities in the field among different N fertilizer rates. Results of this study suggested that the abundance of ammonia-oxidizers had active response to N fertilizer rates and the response of AOA was more obvious than that of AOB. Similarity in the community composition of AOA or AOB among different N fertilizer rates indicate that the community composition of ammonia-oxidizers was relatively stable in the paddy soil at least in short term for three years.
基金This work was supported by the National Major Science and Technology Program for Water Pollution Control and Treatment[grant number 2017ZX07101001]the National Natural Science Foundation of China[grant numbers 41573079 and 41675144]the Chinese Academy of Sciences Pioneer Hundred Talents Program.
文摘Vertical occurrence of soil urease activity along with ammonia content from three distinct regions viz. Deep forest region (No tidal action and wave attack occurs as it is furthest from river shore and it contains maximum content of organic carbon and minimum soil salinity and silicate concentration. In this zone plenty of pneumatophores, below ground root and dense vegetation are found), Rooted region (It is situated in between Deep forest region and Un-rooted region. This region contains only pneumatophores but it is devoid of long roots and vegetations. It faces wave attack and tidal action less than that of Un-rooted region) and Un-rooted region (It is closest to river shore and faces maximum wave attack and tidal action;it contains minimum organic carbon but maximum soil salinity and silicate concentration. This zone is totally devoid of any roots, pneumatophores and vegetations) of Sundarban mangrove forest ecosystem, India revealed an interesting explanation. Soil urease activity showed a decreasing pattern with increase in depth from the deep forest region of the Sundarban forest ecosystem. Soil urease activity was found to be more sensitive to soil temperature and pH rather than soil salinity. This ensured that soil urease along with the microbes present in the Sundarban forest ecosystem are more tolerant to fluctuation in salinity than that of temperature. Soil ammonia concentration was found to be directly governed by the soil urease activity [The regression equation is Ammonia in soil = -1.64 + 0.0402 Urease Activity (R-Sq = 62.9%, P < 0.001, n = 41)].
基金1Project supported by the National Natural Science Foundation of China (NSFC) (Nos. 40271098 and 40471074).
文摘A red soil, a fluvo-aquic soil and a permeable paddy soil were used in a long-term investigation to study changes in nitrification with treatments: 1) soil incubation, 2) liquid incubation inoculated with soil samples, and 3) liquid incubation inoculated with ammonia-oxidizing bacteria (AOB) from the soils. There were significant differences (P < 0.001) in nitrification rates among the three soils when measured for 28 days by adding (NH4)SO4 at the rate of 154 mg N kg-1 dry soil to fresh soil. However, the amounts of nitrifying bacteria in the three soils were not related to soil nitrification capacity. When the soil samples or the isolates of AOB enriched from the corresponding soil were incubated in liquid with pH 5.8, 7.0 and 8.0 buffers and 10 mmol L-1 ammonium nitrogen, there were no significant nitrification differences in the same soil type at each pH. The ability to oxidize ammonia through AOB from different types of soils in a homogeneous culture medium was similar, and the soil nitrification capacity could reflect the inherent properties of a soil. Altering the culture medium pH of individual soil type also showed that acidification of an alkaline fluvo-aquic soil decreased nitrification capacity, whereas alkalinization of the acidic red soil and permeable paddy soil increased their nitrification. For a better insight into factors influencing soil nitrification processes, soil properties including texture and clay composition should be considered.
基金supported by the National Natural Science Foundation of China (Grant No.30671223)the 11th 5-year Major Project of National Science and Technology Support Plan (GrantNo. 2006BAD02A03)
文摘We conducted field trials of rice grown in sandy soil and clay soil to determine the effects of nitrogen application levels on the concentration of NH4＋-N in surface water, loss of ammonia through volatilization from paddy fields, rice production, nitrogen-use efficiency, and nitrogen content in the soil profile. The concentration of NH4＋-N in surface water and the amount of ammonia lost through volatilization increased with increasing nitrogen application level, and peaked at 1-3 d after nitrogen application. Less ammonia was lost via volatilization from clay soil than from sandy soil. The amounts of ammonia lost via volatilization after nitrogen application differed depending on the stage when it was applied, from the highest loss to the lowest： N application to promote tillering 〉 the first N topdressing to promote panicle initiation （applied at the last 4-leaf stage） 〉 basal fertilizer 〉 the second N topdressing to promote panicle initiation （applied at the last 2-leaf stage）. The total loss of ammonia via volatilization from clay soil was 10.49-87.06 kg/hm2, equivalent to 10.92%-21.76% of the nitrogen applied. The total loss of ammonia via volatilization from sandy soil was 11.32-102.43 kg/hm2, equivalent to 11.32%-25.61 % of the nitrogen applied. The amount of ammonia lost via volatilization and the concentration of NH4＋-N in surface water peaked simultaneously after nitrogen application; both showed maxima at the tillering stage with the ratio between them ranging from 23.76% to 33.65%. With the increase in nitrogen application level, rice production and nitrogen accumulation in plants increased, but nitrogen-use efficiency decreased. Rice production and nitrogen accumulation in plants were slightly higher in clay soil than in sandy soil. In the soil, the nitrogen content was the lowest at a depth of 40-50 cm. In any specific soil layer, the soil nitrogen content increased with increasing nitrogen application level, and the soil nitrogen content was higher in clay soil than in sandy soil. In terms of ammonia volatilization, the amount of ammonia lost via volatilization increased markedly when the nitrogen application level exceeded 250 kg/hm2 in the rice growing season. However, for rice production, a suitable nitrogen application level is approximately 300 kg/hm2. Therefore, taking the needs for high crop yields and environmental protection into account, the appropriate nitrogen application level was 250-300 kg/hm2 in these conditions.
基金supported by the National Natural Science Foundation of China (41471190)the National Key Research and Development Program of China (2016YFD0800102)+2 种基金the Special Fund for the Agricultural Public Welfare Profession of China (201503106)the Newton Fund, United Kingdom (BB/N013484/1)the GEF on the ‘Towards INMS’
文摘The upland agricultural soils in North China are distributed north of a line between the Kunlun Mountains, the Qinling Mountains and the Huaihe River. They occur in arid, semi-arid and semi-humid regions and crop production often depends on rain-fed or irrigation to supplement rainfall. This paper summarizes the characteristics of gross nitrogen（N） transformation, the fate of N fertilizer and soil N as well as the N loss pathway, and makes suggestions for proper N management in the region. The soils of the region are characterized by strong N mineralization and nitrification, and weak immobilization and denitrification ability, which lead to the production and accumulation of nitrate in the soil profile. Large amounts of accumulated nitrate have been observed in the vadose-zone in soils due to excess N fertilization in the past three decades, and this nitrate is subject to occasional leaching which leads to groundwater nitrate contamination. Under farmer＇s conventional high N fertilization practice in the winter wheat-summer maize rotation system（N application rate was approximately 600 kg ha–1 yr–1）, crop N uptake, soil residual N, NH_3 volatilization, NO_3~– leaching, and denitrification loss accounted for around 27, 30, 23, 18 and 2% of the applied fertilizer N, respectively. NH_3 volatilization and NO_3~– leaching were the most important N loss pathways while soil residual N was an important fate of N fertilizer for replenishing soil N depletion from crop production. The upland agricultural soils in North China are a large source of N_2O and total emissions in this region make up a large proportion（approximately 54%） of Chinese cropland N_2O emissions. The “non-coupled strong ammonia oxidation” process is an important mechanism of N_2O production. Slowing down ammonia oxidation after ammonium-N fertilizer or urea application and avoiding transient high soil NH4＋ concentrations are key measures for reducing N_2O emissions in this region. Further N management should aim to minimize N losses from crop and livestock production, and increase the recycling of manure and straw back to cropland. We also recommend adoption of the 4 R（Right soure, Right rate, Right time, Right place） fertilization techniques to realize proper N fertilizer management, and improving application methods or modifying fertilizer types to reduce NH_3 volatilization, improving water management to reduce NO_3~– leaching, and controlling the strong ammonia oxidation process to abate N_2O emission. Future research should focus on the study of the trade-off effects among different N loss pathways under different N application methods or fertilizer products.
基金Project supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No.KZCX2-413-3)National Natural Science Foundation of China (No.30390080)National Basic Research Program of China (No.2005CB121108)
文摘响应到稻田的脲申请的氨挥发损失，氮利用效率，和米饭收益在 Wangzhuang 镇上被调查， Changshu 城市，江苏省，中国。N 化肥处理，适用在三倍，是 0 (控制) ， 100， 200， 300，或 350 kg N 哈 ? 1。在脲被用于地面水以后，一个连续气流包围方法被用来在稻田测量氨挥发。通过氨挥发的全部的 N 损失通常与 N 申请率，和申请评估的二更高的 N 增加了(300 和 350 kg N 哈 ? 1 ) 证明 N 的更高的比率通过氨挥发输了到应用 N。由在全部米饭期间，生长上演的氨挥发的全部的氨损失从 9.0% ～ 16.7% 应用 N 。增加申请率通常减少了在到在植物的 N 的种子的 N 的比率。为所有 N 处理，氮肥利用效率从 30.9% ～ 45.9%。有最高的 N 率的剩余 N 导致了米饭植物，氮肥利用的减少的率，和减少的米饭收益的住宿。从这个实验计算，最节俭的 N 化肥申请率是 227 kg 哈 ? 1 为在泰胡·莱克区域的水稻土的类型。然而，推荐适当 N 化肥申请率以便植物生长被提高，氨损失被减少能改进大米的 N 利用效率。
文摘Field experiments were conducted in 2006 to investigate the impacts of modified rice cultivation systems on: grain yield, N uptake, ammonia volatilization from rice soil and N use efficiency (ANUE, agronomic N use efficiency;and PFP, partial factor productivity of applied N). The trials compared rice production using modified methods of irrigation, planting, weeding and nutrient management (the system of rice intensification, SRI) with traditional flooding (TF). The effects of different N application rates (0, 80, 160, 240 kg ha-1) and of N rates interacting with cultivation methods were also evaluated. Grain yields ranged from 5.6 to 6.9 t ha-1 with SRI, and from 4.0 to 6.1 t ha-1 under TF management. On average, grain yields under SRI were 24% higher than that with TF. Ammonia volatilization was increased significantly under SRI compared with TF and the average total amount of ammonia volatilization loss during the rice growth stage under SRI was 22% higher than TF. With increases in application rate, N uptake by rice increased, and the ratio of N in the seed to total N in the plant decreased. Furthermore, results showed that higher ANUE was achieved at a relatively low N fertilizer rate (80 kg ha-1 N) with SRI. Results of these studies suggest that SRI increased rice yield and N uptake and improved ammonia volatilization loss from rice soil compared with TF. Moreover, there were significant interactions between N application rates and cultivation methods. We conclude that it was the most important to adjust the amount of N application under SRI, such as reducing the amount of N application. Research on effects of N fertilizer on rice yield and environmental pollution under SRI may be worth further studying.
