共查询到20条相似文献，搜索用时 31 毫秒
1.
Stephanie A. Boyle Rockie R. Yarwood Peter J. Bottomley David D. Myrold 《Soil biology & biochemistry》2008,40(2):443-451
A study was conducted at two experimental tree plantations in the Pacific Northwest to assess the roles of bacteria and fungi in nitrogen (N) cycling. Soils from red alder (Alnus rubra) and Douglas-fir (Pseudotsuga menziesii) plots in low- (H.J. Andrews) and high- (Cascade Head) productivity stands were sampled in 2005 and 2006. Fungal:bacterial ratios were determined using phospholipid fatty acid (PLFA) profiles and quantitative (Q)-PCR. Ratios from these two molecular methods were highly correlated and showed that microbial biomass varied significantly between the two experimental sites and to a lesser extent between tree types with fungal:bacterial biomass ratios lower in more N-rich plots. 15N isotope dilution experiments, with ammonium (NH4+) and nitrate (NO3?), were paired with antibiotics that blocked bacterial (bronopol) and fungal (cycloheximide) protein synthesis. This modified isotope dilution technique was used to determine the relative contribution of bacteria and fungi to net N mineralization and gross rates of ammonification and nitrification. When bacterial protein synthesis was blocked NH4+ consumption and nitrification rates decreased in all treatments except for NH4+ consumption in the Douglas-fir plots at H.J. Andrews, suggesting that prokaryotic nitrifiers are a major sink for mineral NH4+ in forest soils with higher N availability. Cycloheximide consistently increased NH4+ consumption, however the trend was not statistically significant. Both antibiotics additions also significantly increased gross ammonification, which may have been due to continued activity of extra- and intracellular enzymes involved in producing NH4+ combined with the inhibition of NH4+ assimilation into proteins. The implication of this result is that microorganisms are likely a major sink for soil dissolved organic N (DON) in soils. 相似文献
2.
Stefan Ruyters Jelle Mertens Dirk Springael Erik Smolders 《Soil biology & biochemistry》2010,42(5):766-772
Field data have shown that soil nitrifying communities gradually adapt to zinc (Zn) after a single contamination event with reported adaptation times exceeding 1 year. It was hypothesized that this relatively slow adaptation relates to the restricted microbial diversity and low growth rate of the soil nitrifying community. This hypothesis was tested experimentally by recording adaptation rates under varying nitrification activities (assumed to affect growth rates) and by monitoring shifts in community composition. Soils were spiked at various Zn concentrations (0-4000 mg Zn kg−1) and two NH4+-N doses (N1, N2) were applied to stimulate growth. A control series receiving no extra NH4+-N was also included. Soils were incubated in pots under field conditions with free drainage. The pore water Zn concentration at which nitrification was halved (EC50, mg Zn l−1) did not change significantly during 12 months in the control series (without NH4+-N applications), although nitrification recovered after 12 months at the highest Zn dose only. The EC50 after 12 months incubation increased by more than a factor 10 with increasing NH4+-N dose (p < 0.05) illustrating that increased activity accelerates adaptation to Zn. Zinc tolerance tests confirmed the role of Zn exposure, time and NH4+-N dose on adaptation. Zinc tolerance development was ascribed to the AOB community since the AOB/AOA ratio (AOB = ammonia oxidizing bacteria; AOA = ammonia oxidizing archaea) increased from 0.4 in the control to 1.4 in the most tolerant community. Moreover, the AOB amoA DGGE profile changed during Zn adaptation whereas the AOA amoA DGGE profile remained unaffected. These data confirm the slow but pronounced adaptation of nitrifiers to Zn contamination. We showed that adaptation to Zn was accelerated at higher activity and was associated with a shift in soil AOB community that gradually dominated the nitrifying community. 相似文献
3.
Soil surface electrochemical properties may have a strong influence on nitrifying microorganisms, H+ and NH4+ activities, and therefore on the nitrification process. A gradient of surface electrochemical parameters was obtained by amendment of a subtropical acid pine soil (Oxisol) with 0% (control), 3%, 5%, 8%, 10% and 12% pure Ca-Montmorillonite by weight. The H+ and NH4+ activities, the abundance of the ammonia-oxidizing bacterial (AOB) and archaeal (AOA) amoA gene copies, and time-dependent kinetics of net nitrification were investigated. Soil particle surface specific area ranged from 53 to 103 m2 g−1 and increased with increasing montmorillonite application rate. Similar to specific area, surface charge quantity, surface charge density, electric field strength and surface potential increased after montmorillonite amendment. The H+ and NH4+ activities decreased linearly after montmorillonite addition. AOB amoA gene copy number was 1.82 × 105 copies g−1 for unamended soil, and the highest AOB amoA gene copy numbers were found for the 10% montmorillonite amendment (3.11 × 107 g−1 soil), which was more than 150 times higher than unamended soil. AOA amoA gene copy numbers were 9.19 × 103 copies g−1 dry unamended soil, and the highest AOA amoA gene copy numbers were found in the 8% montmorillonite amendment (1.22 × 105 g−1 soil). Although pH significantly decreased during the first three weeks of incubation, no significant difference was observed between the unamended control and different rates of montmorillonite addition treatments during the whole incubation. The largest net nitrification (103 mg N kg−1) was observed in the 10% montmorillonite amendment and the lowest in unamended soil (62 mg N kg−1). While montmorillonite did not change the kinetic patterns of net nitrification, the highest nitrification potential (275 mg N kg−1) for the 10% montmorillonite treatment was more than 3 times higher than unamended soil from simulation of time-dependent kinetics. Nitrification was significantly stimulated after montmorillonite amendment in acid soil mainly due to an increase in the quantity and activity of AOB and AOA. We concluded that soil particle surface parameters can significantly influence nitrification, especially in acid soils. 相似文献
4.
HongLing Qin HongZhao Yuan Hui Zhang YiJun Zhu Chunmei Yin Zhoujin Tan JinShui Wu WenXue Wei 《Biology and Fertility of Soils》2013,49(6):767-776
As part of a long-term sloped land use experiment established in 1995 at Taoyuan Agro-ecosystem Research Station (111°26′ E, 28°55′ N) in China, soil samples were collected from three land use types, including cropland (CL), natural forest, and tea plantation. Quantitative polymerase chain reaction and terminal restriction fragment length polymorphism were used to determine the abundance and community composition of amoA-containing bacteria (AOB) and archaea (AOA). The results indicate that land use type induced significant changes in soil potential nitrification rate and community composition, diversity, and abundance of AOB and AOA. Both AOB and AOA community compositions were generally similar between upper and lower slope positions (UP and LP), except within CL. The LP soils had significantly (p?<?0.05) higher diversity and abundance of both AOB and AOA than in the UP. Potential nitrification rate was significantly correlated (p?<?0.05) with diversity and abundance of AOA, but not with AOB. Among land use types, the NO3 ? and amoA-containing AOA runoff loss was greatest in CL. Nitrate-N runoff loss was significantly correlated (p?<?0.05) with the loss of AOA amoA copies in the runoff water. Furthermore, relationships between NO3 ?-N runoff loss and abundance of AOA but not of AOB at both slope positions were significantly correlated (p?<?0.05). These findings suggest that AOA are more important than AOB in nitrification and NO3 ?-N runoff loss in acidic soils across sloped land use types. 相似文献
5.
Chang YIN Xiaoping FAN Hao CHEN Mujun YE Guochao YAN Tingqiang LI Hongyun PENG Shengzhe E Zongxian CHE Steven A. WAKELIN Yongchao LIANG 《土壤圈》2022,32(4):532-542
Disparities in the substrate affinity and tolerance threshold for ammonia have been believed to play a key role in driving niche differentiation between ammonia-oxidizing archaea (AOA) and bacteria (AOB); however, recent surveys argue that direct competition between AOA and AOB is also important in this phenomenon. Accordingly, it is reasonable to predict that diverse AOA lineages would grow in ammonium (NH4+)-rich alkaline arable soils if AOB growth is suppressed. To test this hypothesis, a microcosm study was established using three different types of alkaline arable soils, in which a high NH4+ concentration (200 μg N g-1 dry soil) was maintained by routinely replenishing urea and the activities of AOB were selectively inhibited by 1-octyne or 3,4-dimethylpyrazole phosphate (DMPP). Compared with amendment with urea alone, 1-octyne partially retarded AOB growth, while DMPP completely inhibited AOB. Both inhibitors accelerated the growth of AOA, with significantly higher ratios of abundance of AOA to AOB observed with DMPP amendment across soils. Nonmetric multidimensional scaling analysis (NMDS) indicated that different treatments significantly altered the community structures of both AOA and AOB and AOA OTUs enriched by high-NH4+ amendment were taxonomically constrained across the soils tested and closely related to Nitrososphaera viennensis EN76 and N. garnensis. Given that these representative strains have been demonstrated to be sensitive to high ammonia concentrations, our results suggest that it is the competitiveness for ammonia, rather than disparities in substrate affinity and tolerance threshold for ammonia, that drives niche differentiation between these phylotypes and AOB in NH4+-rich alkaline soils. 相似文献
6.
7.
Short-term population dynamics of ammonia oxidizing bacteria in an agricultural soil 总被引：2，自引：0，他引：2
Ammonia oxidizing bacteria (AOB) control the rate limiting step of nitrification, the conversion of ammonia (NH4+) to nitrite (NO2−). The AOB therefore have an important role to play in regulating soil nitrogen cycling. Tillage aerates the soil, stimulating rapid changes in soil N cycling and microbial communities. Here we report results of a study of the short term responses of AOB and net nitrification to simulated tillage and NH4+ addition to soil. The intensively farmed vegetable soils of the Salinas Valley, California, provide the context for this study. These soils are cultivated frequently, receive large N fertilizer inputs and there are regional concerns about groundwater N concentrations. An understanding of N dynamics in these systems is therefore important. AOB population sizes were quantified using a real-time PCR approach. In a 15 day experiment AOB populations, increased rapidly following tillage and NH4+ addition and persisted after the depletion of soil NH4+. AOB population sizes increased to a similar degree, over a 1.5-day period, irrespective of the amount of NH4+ supplied. These data suggest selection of an AOB community in this intensively farmed and C-limited soil, that rapidly uses NH4+ that becomes available. These data also suggest that mineralization may play an especially important role in regulating AOB populations where NH4+ pool sizes are very low. Methodological considerations in the study of soil AOB communities are also discussed. 相似文献
8.
Soil organic carbon (SOC) dynamics and nutrient availability determine the soil quality and fertility in a Chinese fir plantation forest in subtropical China. Uniformly 13C-labeled Chinese fir (Cunninghamia lanceolata) and alder (Alnus cremastogyne) leaf litter with or without 100 mg NH4+ or NO3− were added to the soil. The purpose was to investigate the influence of N availability on the decomposition of the litter and native SOC. The production of CO2, the natural abundance of 13C–CO2, and the inorganic N dynamics were monitored. The results showed that Chinese fir (with a high C:N ratio) and alder (with a low C:N ratio) leaf litter caused significant positive priming effects (PEs) of 24% and 42%, respectively, at the end of the experiment (235 d). The PE dynamics showed that positive PE can last for at least 87 d. However, the possible occurrence of a significant negative PE with a sufficient incubation period is difficult to confirm. The application of both NH4+ and NO3− was found to have a stimulating effect on the decomposition of Chinese fir and alder leaf litter in the early stage (0–15 d) of incubation, but an adverse effect in the late stage. Compared with NO3−, NH4+ caused a greater decrease in the PE induced by both Chinese fir and alder leaf litter. The effects of NH4+ and NO3− on the PE dynamics had different patterns for different incubation stages. This result may indicate that the stability or recalcitrance of SOC, especially in such plantation forest soils, strongly depends on available leaf litter and application of N to the soil. 相似文献
9.
Responses of bacterial and archaeal ammonia oxidisers of an acidic luvisols soil to different nitrogen fertilization rates after 9?years 总被引：1，自引：0，他引：1
It is still not clear which group of ammonia-oxidizing microorganisms plays the most important roles in nitrification in soils. Change in abundances and community compositions of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) under long-term different nitrogen (N) fertilization rates were investigated in an acidic luvisols soil using real-time polymerase chain reaction and denaturing gradient gel electrophoresis, respectively, based on the ammonia monooxygenase a-subunit gene. The experimental plan included the following treatments: control without N fertilization (NCK), low N fertilization rate, middle N fertilization rate, and high N fertilization rate as 0, 100, 150, and 250?kg urea-N?ha?1, respectively. Long-term different N fertilization rates did not significantly alter the total C and N contents of soil while it significantly decreased soil pH, which ranged from 5.60 to 5.20. The AOB abundance was more abundant in the N fertilization treatments than the NCK treatment; the AOA abundance decreased by the increasing N fertilization rates, as did the ratios of AOA/AOB. The large differences in the potential nitrification rates among four treatments depended on the changes in AOA abundance but not to changes in AOB abundance. Phylogenetic analysis showed that the AOB communities were dominated by Nitrosospira clusters 1, 3, and 9 while all AOA sequences were grouped into soil/sediment cluster except for one sequence. Taken together, these results indicated that AOB and AOA preferred different soil N conditions and AOA were functionally more important in the nitrification than AOB in the acidic luvisols soil. 相似文献
10.
《Applied soil ecology》2010,46(3):131-137
The effects of bacterial-feeding nematodes on nitrification and the ammonia-oxidizing bacteria (AOB) community composition were studied in soil microcosms. Sterilized soils were inoculated with mixed soil bacteria (obtained by filtering) or with bacteria and bacterial-feeding nematodes, after which the dynamic inorganic nitrogen concentration was measured weekly. After 28 days of incubation, denaturing gradient gel electrophoresis (DGGE) based on PCR amplification of the amoA gene was used to analyze the AOB community composition. In addition, a clone library from the amoA gene fragments was established using clones randomly selected and sequenced from the two treatments. The results showed that the presence of bacterial-feeding nematodes led to significantly greater NH4+ and NO3− contents over the entire incubation period, indicating that bacterial-feeding nematodes promoted both N mineralization and nitrification. The results of DGGE showed that the AOB community composition was significantly changed in the presence of bacterial-feeding nematodes. Furthermore, the sequencing results suggested that Nitrosospira sp. was the dominant species in the treatment without nematodes, while Nitrosomonas sp. and Nitrosospira sp. were the dominant species in the treatment with nematodes. Such changes in the AOB community may be one of explanation of the important role that nematodes play in promoting nitrification. 相似文献
11.
Wang Mengzi Wang Shanyun Long Xien Zhuang Linjie Zhao Xue Jia Zhongjun Zhu Guibing 《Journal of Soils and Sediments》2019,19(3):1077-1087
Purpose
Ammonia oxidation is the limiting step in soil nitrification and critical in the global nitrogen cycle. The discovery of ammonia-oxidizing archaea (AOA) has improved our knowledge of microbial mechanisms for ammonia oxidation in complex soil environments. However, the relative contributions of AOA and ammonia-oxidizing bacteria (AOB) to ammonia oxidation remain unclear.
Materials and methodsIn this study, through large geographical scale sampling in China, totally nine samples representing various types of arable land soils were selected for analyzing the ammonia oxidation activity. The AOA and AOB activities were separately determined by using the dicyandiamide and 1-octyne inhibition method. High-throughput pyrosequencing and DNA stable-isotope probing (DNA-SIP) analysis were applied to investigate the distribution and activity of Candidatus Nitrosocosmicus franklandus in the arable land soils.
Results and discussionIn this study, AOA abundance (3.2?×?107–3.4?×?109 copies g?1) and activity (0.01–1.33 mg N kg?1 dry soil day?1) were evaluated for nine selected arable land soils and accounted for 4–100% of ammonia oxidation. By separately determining AOA and AOB rates, we observed that archaeal ammonia oxidation dominated the ammonia oxidation process in six soils, revealing a considerable contribution of AOA in ammonia oxidation in arable land soils. Based on high-throughput pyrosequencing analysis, the AOA species Ca. N. franklandus with relatively low abundance (0.6–13.5% in AOA) was ubiquitously distributed in all the tested samples. Moreover, according to the DNA-SIP analysis for Urumqi sample, the high activity and efficiency of Ca. N. franklandus in using CO2 suggests that this species plays an important role in archaeal ammonia oxidation in arable land soils.
ConclusionsThrough determining the AOA activity and analyzing the potential predominant functional AOA species, this study greatly improves our understanding of ammonia oxidation in arable land soils.
相似文献12.
The occurrence of nitrification in some acidic forest soils is still a subject of debate. Identification of main nitrification pathways in acidic forest soils is still largely unknown. Acidic yellow soil (Oxisol) samples were selected to test whether nitrification can occur or not in acidic subtropical pine forest ecosystems. Relative contributions of autotrophs and heterotrophs to nitrification were studied by adding selective nitrification inhibitor nitrapyrin. Soil NH4+-N concentrations decreased, but NO3--N concentrations increased significantly for the no-nitrapyrin control during the first week of incubation, indicating that nitrification did occur in the acidic subtropical soil. The calculated net nitrification rate was 0.49 mg N kg-1 d-1 for the no-nitrapyrin control during the first week of incubation. Nitrapyrin amendment resulted in a significant reduction of NO3--N concentration. Autotrophic nitrification rate averaged 0.28 mg N kg-1 d-1 and the heterotrophic nitrification rate was 0.21 mg N kg-1 d-1 in the first week. Ammonia-oxidizing bacteria (AOB) abundance increased slightly during incubation, but nitrapyrin amendment significantly decreased AOB amoA gene copy numbers by about 80%. However, the ammonia-oxidizing archaea (AOA) abundance showed significant increases only in the last 2 weeks of incubation and it was also decreased by nitrapyrin amendment. Our results indicated that nitrification did occur in the present acidic subtropical pine forest soil, and autotrophic nitrification was the main nitrification pathway. Both AOA and AOB were the active biotic agents responsible for autotrophic nitrification in the acidic subtropical pine forest soil. 相似文献
13.
Increasing lines of evidence have suggested the functional importance of ammonia-oxidizing archaea (AOA) rather than bacteria (AOB) for nitrification in upland soils with low pH. However, it remains unclear whether niche specialization of AOA and AOB occurs in rice paddy wetlands constrained by oxygen availability. Using DNA-based stable isotope probing, we conclude that AOA dominated nitrification activity in acidic paddy soils (pH 5.6) while AOB dominated in alkaline soils (pH 8.2). Nitrification activity was stimulated by urea fertilization and accompanied by a significant increase of AOA in acid soils and AOB in alkaline soils. DNA-based stable isotope probing indicated significant assimilation of 13CO2 for AOA only in acidic paddy soil, while AOB was the solely responsible for ammonia oxidation in the alkaline paddy soil. Phylogenetic analysis further indicated that AOA members within the soil group 1.1b lineage dominated nitrification in acid soils. Ammonia oxidation in the alkaline soil was catalyzed by Nitrosospira cluster 3-like AOB, suggesting that the physiological diversity of AOA is more complicated than previously thought, and soil pH plays important roles in shaping the community structures of ammonia oxidizers in paddy field. 相似文献
14.
Purpose
Microbial nitrification plays an important role in nitrogen cycling in ecosystems. Nitrification is performed by ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (NOB) including complete ammonia oxidizers. However, the relative importance of nitrifiers in autotrophic nitrification in relation to soil pH is still unclear.
Materials and methodsCombining DNA-based stable isotope probing (SIP) and molecular biological techniques, we investigated the abundance, structure, and activity of AOA, AOB, and NOB along a pH-gradient (3.97–7.04) in a vegetable cropped soil.
Results and discussionWe found that AOA abundance outnumbered AOB abundance and had a significantly negative relationship with soil pH. The abundances of NOB Nitrospira 16S rRNA, nxrB gene, and Nitrobacter nxrA gene were affected by soil pH. Incubation of soil with 13CO2 and DNA-SIP analysis demonstrated that significant 13CO2 assimilation by AOA rather than by AOB occurred in the acidic soils, whereas the labeled 13C level of AOA was much less in the neutral soil than in the acidic soils. There was no evidence of 13CO2 assimilation by NOB except for Nitrobacter with NxrB gene at pH 3.97. Phylogenetic analysis of AOA amoA gene in the 13C- and 12C-labeled treatments showed that the active AOA mainly belonged to Nitrososphaera in the acidic soils.
ConclusionsThese results suggested that the main performer of nitrification was AOA in the acidic soils, but both AOA and AOB participated in nitrification in the neutral soil with low nitrification activity. NOB Nitrospira and Nitrobacter did not grow in the soils with pH 4.82–7.04 and other populations of NOB were probably involved in nitrite oxidation in the vegetable cropped soil.
相似文献15.
The effects of plants on the microbiota involved in the oxidation of ammonia in soils have been controversial. Here, we investigated the dynamics in the abundances and community structures of the bacterial and archaeal ammonia oxidizers (AOB and AOA, respectively) in two fields that were cropped with potato. Six different potato cultivars were used, including a genetically-modified one, in a fourfold replicated experimental set-up. On the basis of bulk and rhizosphere soil extracted microbial community DNA, AOB and AOA quantitative PCR as well as PCR-DGGE were performed. In addition, samples were used for the production and analysis of amoA gene fragment based clone libraries. Regardless of sample type (bulk versus rhizosphere soil) and across soils, the population sizes of AOA (of the order 104–108 amoA gene copies g−1 dry soil), were generally higher than those of AOB in the same samples (about 104–105 g−1 dry soil), resulting in ratio's of log-transformed values > 1.0. Whereas the AOB numbers were generally raised in the rhizosphere versus bulk soils in both soils, the opposite was true for the AOA numbers. Moreover, significant effects of cultivar type on both the AOB and AOA community structures were found in both soils, and these extended to beyond the rhizospheres. The effects were found across the whole growth season. Soil type did not significantly affect the community structures of AOA, but had a small effect on the community structure of AOB. Analysis of the structures of the AOB communities revealed a prevalence of AOB subgroups 2, 3a, 3b and 4 in one field soil and of 2 and 4 in the other one. With respect to the AOA, soil/sediment clusters (SS) I, II, III and IV were found to prevail. 相似文献
16.
Forest soils are commonly limited in nitrogen (N), and the removal of aboveground biomass in harvesting operations can exacerbate the problem. Thus, the soil organisms that facilitate the rate-limiting step in the N cycle, the oxidation of ammonium (NH4+), are of special interest in harvested environments. The objective of this study was to investigate the changes in ammonia oxidizing bacteria (AOB) communities that occurred in the years following clear cutting, and link those community shifts to availability of inorganic N forms NH4+ and nitrate (NO3?). Genetic fingerprinting targeting the amoA gene coupled with denaturing gel gradient electrophoresis was carried out over two summers on forest floor (LFH) and mineral (Ae) soils of three similar cutblocks harvested during different years. In-situ NH4+ and NO3? availability was measured over the growing seasons of 2009 and 2010, as well as a suite of physical soil characteristics. Results indicated that the AOB community composition differed in younger vs. older cutblocks, but not by soil horizon. The changes seen in the AOB paralleled the change in N bioavailability across sites, soil horizons, and sampling years, thus indicating that N bioavailability may be directly linked to AOB community composition. This link may provide the basis for the use of AOB as indicators of nutrient availability in the future. 相似文献
17.
The intensive conversion from woodland to tea plantation in subtropical China might significantly change the potential supply processes and cycling of inorganic Nitrogen (N). However, few studies have been conducted to investigate the internal N transformations involved in the production and consumption of inorganic N and N2O emissions in subtropical soils under tea plantations. In a 15N tracing experiment, nine tea fields with different plantation ages (1-y, 5-y and 30-y) and three adjacent woodlands were sampled to investigate changes in soil gross N transformation rates in humid subtropical China. Conversion of woodland to tea plantation significantly altered soil gross N transformation rates. The mineralization rate (MNorg) was much lower in soils under tea plantation (0.53–0.75 mg N kg−1 d−1) than in soil sampled from woodland (1.71 mg N kg−1 d−1), while the biological inorganic N supply (INS), defined as the sum of organic N mineralized into NH4+ (MNorg) and heterotrophic nitrification (ONrec), was not significantly different between soils under woodland and tea plantation, apart from soil under 30-y tea plantation which had the largest INS. Interestingly, the contribution of ONrec to INS increased from 19.6% in soil under woodland to 65.0–82.4% in tea-planted soils, suggesting ONrec is the dominant process producing inorganic N in tea-planted soils. Meanwhile, the conversion from woodland to tea plantation destroyed soil NO3− retention by increasing ONrec, autotrophic nitrification (ONH4) and abiotic release of stored NO3− while decreasing microbial NO3− immobilization (INO3), resulting in greater NO3− production in soil. In addition, long-term tea plantation significantly enhanced the potential release of N2O. Soil C/N was positively correlated with MNorg and INO3, suggesting that an increase in soil C/N from added organic materials (e.g. rice hull) is likely to reduce the increased production of NO3− in the soils under tea plantation. 相似文献
18.
Purpose
Dicyandiamide (DCD) has been used commercially in New Zealand to reduce nitrate leaching and N2O emissions in grazed pastures. However, there is a lack of information in the literature on the optimum rate of DCD to achieve the environmental benefits while at the same time reducing the cost of the technology. The objective of this study was to determine the effect of DCD application rate on its effectiveness to inhibit ammonia oxidizer growth and nitrification rate in a grazed pasture soil.Materials and methods
The soil was a Templeton silt loam (Immature Pallic Soil; Udic Haplustepts) collected from Lincoln University Research Dairy Farm with a mixed pasture consisting of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) and was incubated alone (control) or with cow urine at 700 kg N/ha with 6 rates of DCD [0, 2.5, 5, 7.5, 10 (applied twice), 15 and 20 kg/ha] in incubation vessels. The incubation vessels were placed randomly in an incubator with a constant temperature of 12 °C. During 112 days of incubation, soil subsamples were taken at different time intervals to measure the concentrations of NO3 ?-N and NH4 +-N and the amoA gene copy numbers of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA).Results and discussion
DCD applied at all the different rates inhibited nitrification in urine-treated soils, but the effectiveness increased with DCD application rate. In addition, AOB growth and the amounts of nitrate-N in the soil were significantly related to the application rate of DCD. However, AOA population abundance showed no relationship to the application rate of DCD. The DCD rate at which the AOB growth rate and nitrate-N concentration were halved (effective dosage that causes 50 % reduction in nitrification rate, or ED50) was about 10 kg DCD/ha.Conclusions
These results suggest that DCD applied at relatively low rates still slowed down the nitrification rate, and the current recommended rate of 10 kg DCD/ha for DCD use in New Zealand grazed pastures would result in a 50 % reduction in nitrification rate in this soil. The actual rate of DCD application used would depend on the cost of the product and the environmental and agronomic benefits that would result from its use. 相似文献19.
Aimee Robinson Hong Jie Di Keith C. Cameron Andriy Podolyan Jizheng He 《Journal of Soils and Sediments》2014,14(8):1434-1444