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1.
Indirect evidence of the nitrogen (N) status of tropical forests strongly suggests that in heavily weathered soils under old-growth lowland tropical forests nitrogen is in relative excess. However, within the lowland forests of the Amazon basin, there is substantial evidence that soil texture influences soil NH4+ and NO3? concentrations and hence possibly N availability and retention in the soil. Here, we evaluate the soil N status of two heavily weathered soils which contrast in texture (sandy versus clay Oxisol). Using 15N pool dilution, we quantified gross rates of soil N cycling and retention. We also measured the δ15N signatures from the litter layer down to 50-cm depth mineral soil and calculated the overall 15N enrichment factor (ε) for each soil type. The clay soil showed high gross N mineralization and nitrification rates and a high overall 15N enrichment factor, signifying high N losses. The sandy soil had low gross rates of N cycling and 15N enrichment factor, manifesting a conservative soil N cycling. Faster turnover rates of NH4+ compared to NO3? indicated that NH4+ cycles faster through microorganisms than NO3?, possibly contributing to better retention of NH4+ than NO3?. However this was opposite to abiotic retention processes, which showed higher conversion of NO3? to the organic N pool than NH4+. Our combined results suggest that clay Oxisol in Amazonian forest have higher N availability than sandy Oxisol, which will have important consequences for changes in soil N cycling and losses when projected increase in anthropogenic N deposition will occur.  相似文献   

2.
Extensive use of chemical fertilizers in agriculture can induce high concentration of ammonium nitrogen(NH4+-N) in soil. Desorption and leaching of NH4+-N has led to pollution of natural waters. The adsorption of NH4+-N in soil plays an important role in the fate of the NH4+-N. Understanding the adsorption characteristics of NH4+-N is necessary to ascertain and predict its fate in the soil-water environment, and pedotransfer functions(PTFs) could be a convenient method for quantification of the adsorption parameters. Ammonium nitrogen adsorption capacity, isotherms, and their influencing factors were investigated for various soils in an irrigation district of the North China Plain. Fourteen agricultural soils with three types of texture(silt, silty loam, and sandy loam) were collected from topsoil to perform batch experiments. Silt and silty loam soils had higher NH4+-N adsorption capacity than sandy loam soils.Clay and silt contents significantly affected the adsorption capacity of NH4+-N in the different soils. The adsorption isotherms of NH4+-N in the 14 soils fit well using the Freundlich, Langmuir, and Temkin models. The models’ adsorption parameters were significantly related to soil properties including clay,silt, and organic carbon contents and Fe2+ and Fe3+ ion concentrations in the groundwater. The PTFs that relate soil and groundwater properties to soil NH4+-N adsorption isotherms were derived using multiple regressions where the coefficients were predicted using the Bayesian method. The PTFs of the three adsorption isotherm models were successfully verified and could be useful tools to help predict NH4+-N adsorption at a regional scale in irrigation districts.  相似文献   

3.
Repeated applications of mineral and/or organic fertilizer will probably affect gross nitrogen (N) dynamics in soils in the long term but only a limited number of observations are available. Here we present results of a 15N tracing study with soil from the various fertilizer treatments of the Huang‐Huai‐Hai Plain experiment that has been in operation for more than 17 years. Mineral fertilizer in various combinations of N, phosphorus (P) and potassium (K), organic manure (OM) or a mixture of mineral fertilizer and manure had been repeatedly applied for 17 years. The gross N transformation rates were quantified with a 15N tracing model, which uses a parameter optimization routine based on Bayesian principles. Mineralization of soil organic matter was at least 2.7 times greater in all fertilizer treatments compared with the untreated control (0.67 µg N g?1 day?1). While application of mineral N enhanced mineralization from recalcitrant organic N, the application of organic fertilizers stimulated the mineralization of labile organic N. Gross nitrate (NO3?) production solely resulted from ammonium (NH4+) oxidation. Compared with the gross NO3? production in the control treatment (2.22 µg N g?1 day?1), long‐term N applications stimulated gross nitrification by more than 5.3 times. The largest gaseous N emissions were associated with the organic manure treatments. The ratio of gross NO3? production to total mineral N consumption, a ratio proposed previously to determine potential NO3? loss, was a good indicator except for the treatment without N application. This ratio increased from 0.8 in the control to 2.7 in the mixture of mineral fertilizer and manure treatment. The largest gaseous N emissions (N2O + NO) (P < 0.05) were generally found at greater ratios. Results clearly showed that various fertilizers have a differential effect on N dynamics and potential gaseous N losses in the long term.  相似文献   

4.
Impacts of crop residue biochar on soil C and N dynamics have been found to be subtly inconsistent in diverse soils. In the present study, three soils differing in texture (loamy sand, sandy clay loam and clay) were amended with different rates (0%, 0.5%, 1%, 2% and 4%) of rice-residue biochar and incubated at 25°C for 60 days. Soil respiration was measured throughout the incubation period whereas, microbial biomass C (MBC), dissolved organic C (DOC), NH4+-N and NO3–N were analysed after 2, 7, 14, 28 and 60 days of incubation. Carbon mineralization differed significantly between the soils with loamy sand evolving the greatest CO2 followed by sandy clay loam and clay. Likewise, irrespective of the sampling period, MBC, DOC, NH4+-N and NO3–N increased significantly with increasing rate of biochar addition, with consistently higher values in loamy sand than the other two soils. Furthermore, regardless of the biochar rates, NO3–-N concentration increased significantly with increasing period of incubation, but in contrast, NH4+-N temporarily increased and thereafter, decreased until day 60 in all soils. It is concluded that C and N mineralization in the biochar amended soils varied with the texture and native organic C status of the soils.  相似文献   

5.
Fate of fertilizer ammonium in soils with different composition of clay minerals in an incubation experiment In an incubation experiment with three different soils (gray brown podsolic soil from loess, alluvial gley, and brown earth, derived from basalt) the specific adsorption (fixation) and release of fertilizer NH4+ was investigated. In one treatment 120 mg NH4–N/kg soil was added, while the other treatment (control) received no nitrogen. Soils samples were taken every ten days and analyzed for nonexchangeable and exchangeable NH4+ and NO3?. The experimental results are showing that the specific adsorption of applied NH4+ was related to the type of clay minerals. While the loess soil, rich in illite, and the alluvial soil, rich in expansible clay minerals, bound about 40% of the added NH4+ specifically, the soil derived from basalt with mainly kaolinite bound only about 10 %. From the recently “fixed” fertilizer NH4+ about a half was nitrified during the incubation period of about 9 weeks. In the control there was no significant release of specifically bound NH4+. Obviously this NH4+ is located more deeply in the interlayers of the clay minerals and not available to microorganisms.  相似文献   

6.
Most investigations into the effects of changing soil pH on microbial activity use, from necessity, soils taken from different sites so that soil physical and chemical properties are confounded. Studies along continuous gradients of soil pH within a single soil type are rare, simply because so few exist, in UK or even worldwide. Here we report measurements of mineralisation of native organic matter and added arginine along a continuous soil pH gradient (range about pH 3.7–8.3) of a UK silty clay loam soil (Chromic Luvisol or Typic Paleudalf). The soil has been maintained under constant management for more than 100 years, with winter wheat sown annually. The soil NH4+-N concentration was maximal at the lowest pH (pH 3.7), declining exponentially until pH 5.5 and remaining negligible thereafter. However, unexpectedly, soil NO3?-N concentration was also maximal at pH 3.7 and was significantly negatively correlated with increasing pH thereafter. To investigate these unexpected NO3?-N results, arginine was added as a labile source of organic N and its extent of ammonification and nitrification measured at soil pHs 3.79, 4.42, 6.08 and 7.82. While arginine ammonification was apparently greatest at pHs 3.79 and 4.42, similar to mineralisation of soil organic N, nitrification of this added N was greatest at soil pH 7.82 and least at pH 3.79, the reverse of the situation with soil organic N, but much more in line with what was expected. It was concluded that the decline in soil NO3?-N with increasing pH in the unamended soils was an artefact, caused by increasing plant uptake of NO3?-N as yield increased, rather than a true effect of low pH increasing nitrification of soil organic N. Our results differ from most previous studies, which showed poor correlations between soil pH and arginine mineralisation. This was attributed to our use of much longer incubation times (up to 50 days) than usually employed. Under our conditions, arginine was therefore shown to be a useful model for mineralisation of labile soil organic N.  相似文献   

7.
 Wheat straw enclosed in mesh bags was buried for periods up to 1 year over two seasons in Scottish, Danish and Portuguese soils treated with 15NH4NO3 or NH4 15NO3. Scottish soils were: Terryvale, a poorly drained sandy loam; and Tipperty, an imperfectly drained brown forest soil with a higher clay content. The Danish soil (Foulum) was a freely drained sandy loam and the Portuguese soils were a sandy soil (Evora) and a clay soil (Beja). During the first month, 15N was being incorporated into the straw in the Tipperty, Terryvale and Foulum soils simultaneously as the total N content was decreasing. Subsequently, the straws began to show net immobilization and the total N content of the original straw was exceeded in Tipperty and Foulum soils after 4 months and 8 months, respectively. Net immobilization in Terryvale was detected only in the second season and did not occur in the first because of high soil moisture content. The rates of 15N incorporation were similar in the two Portuguese soils, and a loss of N was only detected after 8 months. After 1 month, in the two clay soils, Beja and Tipperty, 15NO3 – was incorporated into straw to a greater extent than 15NH4 + and this was attributed to 15NH4 + fixation by clay minerals. In contrast, 15NH4 + was more efficiently incorporated than 15NO3 – under waterlogged conditions (Terryvale) and NO3 – loss could be attributed to denitrification. The proportion of added 15N in the straw residue after 1 month varied between 6% and 18% for 15NH4 + and 2% and 23% for 15NO3 – and immobilization of N in the longer term tended to be greater in soils from northern Europe than from Portugal. Received: 19 January 1998  相似文献   

8.
The contribution of bacteria and fungi to NH4+ and organic N (Norg) oxidation was determined in a grassland soil (pH 6.3) by using the general bacterial inhibitor streptomycin or the fungal inhibitor cycloheximide in a laboratory incubation study at 20°C. Each inhibitor was applied at a rate of 3 mg g?1 oven‐dry soil. The size and enrichment of the mineral N pools from differentially (NH415NO3 and 15NH4NO3) and doubly labelled (15NH415NO3) NH4NO3 were measured at 3, 6, 12, 24, 48, 72, 96 and 120 hours after N addition. Labelled N was applied to each treatment, to supply NH4+‐N and NO3?‐N at 3.15 μmol N g?1 oven‐dry soil. The N treatments were enriched to 60 atom % excess in 15N and acetate was added at 100 μmol C g?1 oven‐dry soil, to provide a readily available carbon source. The oxidation rates of NH4+ and Norg were analysed separately for each inhibitor treatment with a 15N tracing model. In the absence of inhibitors, the rates of NH4+ oxidation and organic N oxidation were 0.0045 μmol N g?1 hour?1 and 0.0023 μmol N g?1 hour?1, respectively. Streptomycin had no effect on nitrification but cycloheximide inhibited the oxidation of NH4+ by 89% and the oxidation of organic N by more than 30%. The current study provides evidence to suggest that nitrification in grassland soil is carried out by fungi and that they can simultaneously oxidize NH4+ and organic N.  相似文献   

9.
We examined the influence of various urea granule sizes (< 2, 7.0, 9.9 and 12.7 mm) applied into a silt loam soil (experiment 1) and soil types (sandy, silt and clay loam) treated with the largest granule (experiment 2) on gaseous N loss (except N2) at field capacity. The prilled urea (PU) was mixed into the soil whereas the urea granules were point-placed at a 5.0-cm depth. For experiment 1, N2O emission was enhanced with increasing granule size, ranging from 0.17–0.50% of the added N during the 45-day incubation period. In the case of experiment 2, the sandy loam soil (0.59%) behaved similarly with the silt loam (0.53%) but both showed remarkably lower emissions than were found for the clay loam soil (2.61%). Both nitrification and N2O emissions were delayed by several days with increasing granule size, and the latter was influenced by mineral N, soil water and pH. By contrast, the NH3 volatilization decreased with increasing granule size, implying the inhibition of urease activity by urea concentration gradients. Considering both experimental results, the NH3 loss was highest for the PU-treated (1.73%) and the larger granules regardless of soil type did not emit more than 0.27% of the added N over 22 days, possibly because the high concentrations of either mineral N or NH4 + in the soil surface layer (0–2.5 cm) and the high H+ buffering capacity might regulate the NH3 emission. Similar to the pattern of NH3 loss, NOx emission was noticeably higher for the PU-treated soil (0.97%) than for the larger granule sizes (0.09–0.29%), which were the highest for the sandy and clay loam soils. Positional differences in the concentration of mineral N and nitrification also influenced the NOx emission. As such, total NH3 loss was proportional to total NOx emission, indicating similar influence of soil and environmental conditions on both. Pooled total N2O, NH3 and NOx emission data suggest that the PU-treated soil could induce greater gaseous N loss over larger urea granules, largely in the form of NH3 and NOx emissions, whereas a similar increase with the largest granule size was mainly due to the total N2O flux.  相似文献   

10.
Summer solarization of six wet field soils of four different textures raised soil temperatures by 10–12°C at 15cm depth. Soil solarization increased concentrations of NO?3N and NH+4N up to six times those in nontreated soils. Concentrations of P, Ca2+, Mg2+ and electrical conductivity (EC) increased in some of the solarized soils. Solarization did not consistently affect available K+, Fe3+, Mn2+, Zn2+, Cu2+, Cl? concentrations, soil pH or total organic matter. Concentrations of mineral nutrients in wet soil covered by transparent polyethylene film, but insulated against solar heating, were the same as those in nontreated soil. Increases in NO?3N plus NH+4N were no longer detected in fallowed soils 9 months after solarization. No significant correlation between mineral-nutrient concentration in plant tissue and plant growth was found. Fresh and dry weights of radish, pepper and Chinese cabbage plants usually were greater when grown in solarized soils than in nontreated soils. Fertilization of solarized soils sometimes resulted in greater plant growth responses than observed in solarized but nonfertilized soils.  相似文献   

11.
Surface samples (0–10 cm) of two equally-acidic soils (pH 4.5) exhibited very different net N mineralization rates. In an andic soil, it was negligible despite a high (46%) organic matter content, whereas it was appreciable in a colluvial soil of lower (14%) organic matter content. During incubation experiments no NO?3 was observed in the andic soil, whereas nitrification occurred in the colluvial soil. Incorporation of added 15NH4 is much higher in the andic soil, despite no greater biological immobilization than in the colluvial soil.Added 15NO2? and nitrapyrin experiments showed that incorporation of inorganic-N into the organic fraction of the andic soil can also proceed via a chemical pathway, NO2? self-decomposition and fixation on organic matter. This can be a limitation to NO3? appearance in this soil. The protective effect of amorphous aluminium is also considered to lower mineralization of organic-N. These two mechanisms could be responsible for low concentration of inorganic-N in many aluminous humic-rich acidic soils.  相似文献   

12.

Purpose

Few studies have examined the effects of biochar on nitrification of ammonium-based fertilizer in acidic arable soils, which contributes to NO3 ? leaching and soil acidification.

Materials and methods

We conducted a 42-day aerobic incubation and a 119-day weekly leaching experiment to investigate nitrification, N leaching, and soil acidification in two subtropical soils to which 300 mg N kg?1 ammonium sulfate or urea and 1 or 5 wt% rice straw biochar were applied.

Results and discussion

During aerobic incubation, NO3 ? accumulation was enhanced by applying biochar in increasing amounts from 1 to 5 wt%. As a result, pH decreased in the two soils from the original levels. Under leaching conditions, biochar did not increase NO3 ?, but 5 wt% biochar addition did reduce N leaching compared to that in soils treated with only N. Consistently, lower amounts of added N were recovered from the incubation (KCl-extractable N) and leaching (leaching plus KCl-extractable N) experiments following 5 wt% biochar application compared to soils treated with only N.

Conclusions

Incorporating biochar into acidic arable soils accelerates nitrification and thus weakens the liming effects of biochar. The enhanced nitrification does not necessarily increase NO3 ? leaching. Rather, biochar reduces overall N leaching due to both improved N adsorption and increased unaccounted-for N (immobilization and possible gaseous losses). Further studies are necessary to assess the effects of biochar (when used as an addition to soil) on N.  相似文献   

13.
Increasing the retention of nutrients by agricultural soils is of great interest to minimize losses of nutrients by leaching and/or surface runoff. Soil amendments play a role in nutrient retention by increasing the surface area and/or other chemical processes. Biochar (BC) is high carbon-containing by-product of pyrolysis of carbon-rich feedstocks to produce bioenergy. Biosolid is a by-product of wastewater treatment plant. Use of these by-products as amendments to agricultural soils is beneficial to improve soil properties, soil quality, and nutrient retention and enhance carbon sequestration. In this study, the adsorption of NH4-N, P, and K by a sandy soil (Quincy fine sand (QFS)) and a silty clay loam soil (Warden silty loam (WSL)) with BC (0, 22.4, and 44.8 mg ha?1) and biosolid (0 and 22.4 mg ha?1) amendments were investigated. Adsorption of NH4-N by the QFS soil increased with BC application at lower NH4-N concentrations in equilibrium solution. For the WSL soil, NH4-N adsorption peaked at 22.4 mg ha?1 BC rate. Biosolid application increased NH4-N adsorption by the WSL soil while decreased that in the QFS soil. Adsorption of P was greater by the WSL soil as compared to that by the QFS soil. Biosolid amendment significantly increased P adsorption capacity in both soils, while BC amendment had no significant effects. BC and biosolid amendments decreased K adsorption capacity by the WSL soil but had no effects on that by the QFS soil. Ca release with increasing addition of K was greater by the WSL soil as compared to that by the QFS soil. In both the soils, Ca release was not influenced by BC amendment while it increased with addition of biosolid. The fit of adsorption data for NH4-N, P, and K across all treatments and in two soils was better with the Freundlich model than that with the Langmuir model. The nutrients retained by BC or biosolid amended soils are easily released, therefore are readily available for the root uptake in cropped soils.  相似文献   

14.
High yield agricultural systems, such as high tunnel (HT) vegetable production, require a large supply of soil nutrients, especially nitrogen (N). Compost is a common amendment used by HT growers both to supply nutrients and to improve physical and biological soil properties. We examined commercially-available composts and their effects on soil N, plant N uptake, and tomato yield in HT cultivation. In addition, a laboratory study examined N and carbon (C) mineralization from the composts, and the usefulness of compost properties as predictors of compost N mineralization was assessed under field and laboratory conditions. The field study used a randomized complete block design with four replications to compare four compost treatments (all added at the rate of 300 kg total N ha?1) with unamended soil and an inorganic N treatment (110 kg N ha?1). Tomatoes were grown in Monmouth, Maine during the summers of 2013 and 2014. Compost NO3?-N and NH4+-N application rates were significantly correlated with soil NO3?-N and NH4+-N concentrations throughout the growing season. Marketable yield was positively correlated with compost total inorganic N and NO3?-N in both years, and with NH4+-N in 2014. There were no significant differences among composts in percentage of organic N mineralized and no correlations were observed with any measured compost property. In the laboratory study, all compost-amended soils had relatively high rates of CO2 release for the initial few days and then the rates declined. The compost-amended soils mineralized 4%–6% of the compost organic N. This study suggested compost inorganic N content controls N availability to plants in the first year after compost application.  相似文献   

15.
The aim of this study was to investigate the influence of four different horticultural management practices in open field and in greenhouse conditions under organic and conventional cultivation on the amount of soluble organic nitrogen (SON) present in the soil. Soils used in greenhouses and open field cultivation were sampled in Shanghai, China, where organic farming has been conducted for 3 years or conventional faming has been continued in the same area. The amounts of SON, nitrate (NO3?) and ammonium (NH4+) were greater in the greenhouse soils than those under open field cultivation, which indicated a higher degree of soil management was imposed under greenhouse conditions. Greenhouse cultivation is also known to accelerate the turnover of SON in the soils, which may explain the significantly higher amounts of SON present in these soils. Organic farming, which does not use artificial fertilizers and pesticides, also resulted in significantly higher amounts of SON (average 42.10 mg kg?1) compared with soils under conventional faming (24.59 mg kg?1). The reasons for the observed differences in pool sizes of soluble inorganic nitrogen (SIN) and NO3? in the greenhouse soils and the open fields include (a) the heavy application of both complex fertilizer and organic fertilizer that exceeded crop requirements and (b) warmer temperatures and moist soils in the greenhouses, which are likely to lead to greater rates of N cycling compared with the open field soils. These results suggest that SON may be an important source of N in all horticultural systems, representing a pool of labile N readily available for plant growth. However, its concentration is less sensitive to different management practices than SIN. In contrast to SON, the total soluble nitrogen and inorganic N (SIN) pools varied widely with the different management practices although they were dominated by NO3? in all treatments. Soil organic N was positively related to dissolved organic carbon and NO3? contents. This relationship indicates that NO3? and dissolved organic matter play a key role in the retention of SON in soil.  相似文献   

16.
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17.
Abstract

A new soil extractant (H3A) with the ability to extract NH4, NO3, and P from soil was developed and tested against 32 soils, which varied greatly in clay content, organic carbon (C), and soil pH. The extractant (H3A) eliminates the need for separate phosphorus (P) extractants for acid and calcareous soils and maintains the extract pH, on average, within one unit of the soil pH. The extractant is composed of organic root exudates, lithium citrate, and two synthetic chelators (DTPA, EDTA). The new soil extractant was tested against Mehlich 3, Olsen, and water for extractable P, and 1 M KCl and water‐extractable NH4 and NO2/NO3. The pH of the extractant after adding soil, shaking, and filtration was measured for each soil sample (5 extractants×2 reps×32 soils=320 samples) and was shown to be highly influential on extractable P but has no effect on extractable NH4 or NO2/NO3. H3A was highly correlated with soil‐extractable inorganic N (NH4, NO2/NO3) from both water (r=0.98) and 1 M KCl (r=0.97), as well as being significantly correlated with water (r=0.71), Mehlich 3 (r=0.83), and Olsen (r=0.84) for extractable P.  相似文献   

18.
The inherent features of Acrisols with their increasing clay content with depth are conducive to reducing nutrient losses by nutrient adsorption on the matrix soil surfaces. Ammonium (NH4+) and nitrate (NO3?) adsorption by a Plinthic Acrisol from Lampung, Indonesia was studied in column experiments. The peak of the H218O breakthrough occurred at 1 pore volume, whereas the median pore volumes for NH4+ and NO3? ranged from 6.4 to 6.9 and 1.1 to 1.6, respectively. The adsorption coefficients (Ka in cm3 g–1) measured were 1.81, 1.51, 1.64 and 1.47 for NH4+ and 0.03, 0.09, 0.10 and 0.17 for NO3?, respectively, in the 0–0.2, 0.2–0.4, 0.4–0.6 and 0.6–0.8 m soil depth layers. The NH4+ and NO3? adsorption coefficients derived from this study were put in to the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model to evaluate their effect on leaching in the context of several cropping systems in the humid tropics. The resulting simulations indicate that the inherent ‘safety‐net’ (retardation mechanism) of a shallow (0.8–1 m) Plinthic Acrisol can reduce the leaching of mineral N by between 5 and 33% (or up to 2.1 g m?2), mainly due to the NH4+ retardation factor, and that the effectiveness in reducing N leaching increases with increasing depth. However, the inherent ‘safety‐net’ is useful only if deep‐rooted plants can recover the N subsequently.  相似文献   

19.
A study was carried out to investigate the potential gross nitrogen (N) transformations in natural secondary coniferous and evergreen broad-leaf forest soils in subtropical China. The simultaneously occurring gross N transformations in soil were quantified by a 15N tracing study. The results showed that N dynamics were dominated by NH4+ turnover in both soils. The total mineralization (from labile and recalcitrant organic N) in the broad-leaf forest was more than twice the rate in the coniferous forest soil. The total rate of mineral N production (NH4+ + NO3−) from the large recalcitrant organic N pool was similar in the two forest soils. However, appreciable NO3− production was only observed in the coniferous forest soil due to heterotrophic nitrification (i.e. direct oxidation of organic N to NO3−), whereas nitrification in broad-leaf forest was little (or negligible). Thus, a distinct shift occurred from predominantly NH4+ production in the broad-leaf forest soil to a balanced production of NH4+ and NO3− in the coniferous forest soil. This may be a mechanism to ensure an adequate supply of available mineral N in the coniferous forest soil and most likely reflects differences in microbial community patterns (possibly saprophytic, fungal, activities in coniferous soils). We show for the first time that the high nitrification rate in these soils may be of heterotrophic rather than autotrophic nature. Furthermore, high NO3− production was only apparent in the coniferous but not in broad-leaf forest soil. This highlights the association of vegetation type with the size and the activity of the SOM pools that ultimately determines whether only NH4+ or also a high NO3− turnover is present.  相似文献   

20.
Upland soils are the most important terrestrial sink for the greenhouse gas CH4. The oxidation of CH4 is highly influenced by reactive N which is increasingly added to many ecosystems by atmospheric deposition and thereby also alters the labile C pool in the soils. The interacting effects of soil N availability and the labile C pool on CH4 oxidation are not well understood. We conducted a laboratory experiment with soil columns consisting of homogenised topsoil material from a temperate broad-leaved forest to study the net CH4 flux under the combined or isolated addition of NO 3 ? and glucose as a labile C source. Addition of NO 3 ? and glucose reduced the net CH4 uptake of the soil by 86% and 83%, respectively. The combined addition of both agents led to a nearly complete inhibition of CH4 uptake (reduction by 99.4%). Our study demonstrates a close link between the availability of C and N and the rate of CH4 oxidation in temperate forest soils. Continued deposition of NO 3 ? has the potential to reduce the sink strength of temperate forest soils for CH4.  相似文献   

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