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1.
Nitrogen and carbon isotope responses of Chinese cabbage and chrysanthemum to the application of liquid pig manure 总被引:2,自引:0,他引:2
Sang-Sun Lim Woo-Jung Choi Jin-Hyeob Kwak Jae-Woon Jung Scott X. Chang Han-Yong Kim Kwang-Sik Yoon Soo-Myung Choi 《Plant and Soil》2007,295(1-2):67-77
The effects of the liquid pig manure (LM) used in organic farming on the natural abundance of 15N and 13C signatures in plant tissues have not been studied. We hypothesized that application of LM will (1) increase δ15N of plant tissues due to the high δ15N of N in LM as compared with soil N or inorganic fertilizer N, and (2) increase δ13C of plant tissues as a result of high salt concentration in LM that decreases stomatal conductance of plants. To test these
hypotheses, variations in the δ15N and δ13C of Chinese cabbage (Brassica campestris L.) and chrysanthemum (Chrysanthemum morifolium Ramatuelle) with two different LMs (with δ15N of +15.6 and +18.2‰) applied at two rates (323 and 646 kg N ha-1 for cabbage and 150 and 300 kg N ha-1 for chrysanthemum), or urea (δ15N = -2.7‰) applied at the lower rate above for the respective species, in addition to the control (no N input) were investigated
through a 60-day pot experiment. Application of LM significantly increased plant tissue δ15N (range +9.4 to +14.9‰) over the urea (+3.2 to +3.3‰) or control (+6.8 to 7.7‰) treatments regardless of plant species, strongly
reflecting the δ15N of the N source. Plant tissue δ13C were not affected by the treatments for cabbage (range −30.8 to −30.2‰) or chrysanthemum (−27.3 to −26.8‰). However, cabbage
dry matter production decreased while its δ13C increased with increasing rate of LM application or increasing soil salinity (P < 0.05), suggesting that salinity stress caused by high rate of LM application likely decreased stomatal conductance and
limited growth of cabbage. Our study expanded the use of the δ15N technique in N source (organic vs. synthetic fertilizer) identification and suggested that plant tissue δ13C maybe a sensitive indicator of plant response to salinity stress caused by high LM application rates. 相似文献
2.
The partitioning of fertilizer-N between soil and crop: Comparison of ammonium and nitrate applications 总被引:3,自引:0,他引:3
Field experiments were carried out in 1987 on winter wheat crops grown on three types of soil. 15N-labelled urea, 15NH4NO3 or NH4
15NO3 (80 kg N ha-1) was applied at tillering. The soils (chalky soil, hydromorphic loamy soil, sandy clay soil) were chosen to obtain a range of nitrogen dynamics, particularly nitrification. Soil microbial N immobilization and crop N uptake were measured at five dates. Shortly after fertilizer application (0–26 days), the amount of N immobilized in soil were markedly higher with labelled urea or ammonium than that with nitrate in all soils. During the same period, crop 15N uptake occurred preferentially at the expense of nitrate. Nitrification differed little between soils, the rates were 2.0 to 4.7 kg N ha-1 day-1 at 9°C daily mean temperature. The differences in immobilization and uptake had almost disappeared at flowering and harvest. 15N recovery in soil and crop varied between 50 and 100%. Gaseous losses probably occurred by volatilization in the chalky soil and denitrification in the hydromorphic loamy soil. These losses affected the NH4
+ and NO3
- pools differently and determined the partitioning of fertilizer-N between immobilization and absorption. 相似文献
3.
Peter Sørensen 《Plant and Soil》2004,267(1-2):285-296
About 50–60% of dairy cattle slurry nitrogen is ammonium N. Part of the ammonium N in cattle slurry is immobilised due to
microbial decomposition of organic matter in the slurry after application to soil. The immobilisation and the remineralisation
influence the fertiliser value of slurry N and the amount of organic N that is retained in soil. The immobilisation and the
remineralisation of 15 N-labelled dairy cattle slurry NH4-N were studied through three growing seasons after spring application under temperate conditions. Effects of slurry distribution
(mixing, layer incorporation, injection, surface-banding) and extra litter straw in the slurry on the plant utilisation of
labelled NH4-N from slurry were studied and compared to the utilisation of 15N-labelled mineral fertiliser. The initial immobilisation of slurry N was influenced by the slurry distribution in soil. More
N was immobilised when the slurry was mixed with soil. Surface-banding of slurry resulted in significant volatilisation losses
and less residual 15N in soil. Much more N was immobilised after slurry incorporation than after mineral fertiliser application. After 2.5 years
the recovery of labelled N in soil (0–25 cm) was 46% for slurry mixed with soil, 42% for injected slurry, 22% for surface-banded
slurry and 24% for mineral fertiliser N. The total N uptake in a ryegrass cover crop was 5–10 kg N/ha higher in the autumn
after spring-application of cattle slurry (100–120 kg NH4-N/ha) compared to the mineral fertiliser N reference, but the immobilised slurry N (labelled N) only contributed little to
the extra N uptake in the autumn. Even in the second autumn after slurry application there was an extra N uptake in the cover
crop (0–10 kg N/ha). The residual effect of the cattle slurry on spring barley N uptake was insignificant in the year after
slurry application (equivalent to 3% of total slurry N). Eighteen months after application, 13% of the residual 15N in soil was found in microbial biomass whether it derived from slurry or mineral fertiliser, but the remineralisation rate
(% crop removal of residual 15N) was higher for fertiliser- than for slurry-derived N, except after surface-banding. Extra litter straw in the slurry had
a negligible influence on the residual N effects in the year after application.
It is concluded that a significant part of the organic N retained in soil after cattle slurry application is derived from
immobilised ammonium N, but already a few months after application immobilised N is stabilised and only slowly released. The
immobilised N has negligible influence on the residual N effect of cattle slurry in the first years after slurry application,
and mainly contributes to the long-term accumulation of organic N in soil together with part of the organic slurry N. Under
humid temperate conditions the residual N effects of the manure can only be optimally utilised when soil is also covered by
plants in the autumn, because a significant part of the residual N is released in the autumn, and there is a higher risk of
N leaching losses on soils that receive cattle slurry regularly compared to soils receiving only mineral N fertilisers. 相似文献
4.
Fate of urine nitrogen on mineral and peat soils in New Zealand 总被引:2,自引:0,他引:2
A field lysimeter experiment was conducted over 150 days to examine the fate of synthetic urinary nitrogen (N) applied to peat and mineral soils, with and without a water table. At the start of the winter season, synthetic urine labelled with 15N, was applied at 500 kg N ha–1. Plant uptake, leaching losses and nitrous oxide (N2O) fluxes were monitored. Total plant uptake ranged from 11% to 35% of the urine-N applied depending on soil type and treatment. Plant uptake of applied N was greater in the presence of a water table in the mineral soil. Nitrate-N (NO3
--N) was only detected in leachates from the mineral soil, at concentrations up to 146 g NO3
--N mL–1. Presence of a water table in the mineral soil reduced leaching losses (as inorganic-N) from 47% to 6%, incrased plant uptake and doubled apparent denitrification losses. In the peat soils leaching losses of applied urine-N as inorganic-N were low (<5%). Losses of N as N2O were greater in the mineral soil than in the peat soils, with losses of 3% and <1% of N applied respectively after 100 days. Apparent denitrification losses far exceeded N2O losses and it is postulated that the difference could be due to dinitrogen (N2) loss and soil entrapment of N2. 相似文献
5.
15N-labelled ammonium nitrate was applied to spring barley growing on a Cambisol soil in western Switzerland. Immobilization, plant uptake and disappearance of inorganic nitrogen were followed at frequent intervals. Fertilizer nitrogen disappeared shortly after its application, mainly through immobilization by soil microorganisms and absorption by the crop. Some of the added nitrogen was probably denitrified as a result of humid conditions during the first days after fertilizer application. At the end of the growing season, 31% of the added nitrogen was recovered from the aerial barley plants, and 56% was immobilized by microorganisms. Most of the fertilizer nitrogen not used by the crop was immobilized in the upper 0–30 cm soil layer. This prevented downward movement of nitrate and limited nitrogen losses. Fertilizer efficiency was mainly determined by the competition between crop uptake and microbial immobilization. Careful consideration of the time of fertilization, taking into account plant growth and weather conditions, can result in an increase in fertilizer efficiency and minimal pollution. 相似文献
6.
Rapid abiotic transformation of nitrate in an acid forest soil 总被引:14,自引:4,他引:10
Nitrate immobilization into organic matter isthought to require catalysis by the enzymes ofsoil microorganisms. However, recent studiessuggest that nitrate added to soil isimmobilized rapidly and this process mayinclude abiotic pathways. We amended living andsterilized soil with 15N-labeled nitrateand nitrite to investigate biotic and abioticimmobilization. We report rapid transformationof nitrate in incubations of the O layer offorest soils that have been sterilized toprevent microbial activity and to denaturemicrobial enzymes. Approximately 30, 40, and60% of the 15N-labeled nitrate added tolive, irradiated, or autoclaved organic horizonsoil disappeared from the extractableinorganic-N pool in less than 15 minutes. About5% or less of the nitrate was recovered asinsoluble organic N in live and sterilizedsoil, and the remainder was determined to besoluble organic N. Added 15N-nitrite,however, was either lost to gaseous N orincorporated into an insoluble organic N formin both live and sterile organic soils. Hence,the fate and pathway of apparent abioticnitrate immobilization differs from thebetter-known mechanisms of nitrite reactionswith soil organic matter. Nitrate and nitriteadded to live A-horizon soil was largelyrecovered in the form added, suggesting thatrapid conversion of nitrate to solubleorganic-N may be limited to C-rich organichorizons. The processes by which this temperateforest soil transforms added nitrate to solubleorganic-N cannot be explained by establishedmechanisms, but appears to be due to abioticprocesses in the organic horizon. 相似文献
7.
Forest floor-mineral soil interactions in the internal nitrogen cycle of an old-growth forest 总被引:8,自引:2,他引:6
Seasonal patterns and annual rates of N inputs, outputs, and internal cycling were determined for an old-growth mixed-conifer forest floor in the Sierra Nevada Mountains of California. Rates of net N mineralization within the forest floor, and plant N-uptake and leaching of inorganic N from the forest floor were 13, 10, and 9 kg-N ha-1 yr-1, respectively. The Mediterranean-type climate appeared to have a significant effect on N cycling within this forest, such that all N-process and flow rates showed distrinct seasonal patterns. We estimated the forest floor supplies less than one-third of the total aboveground plant N-uptake in this forest. The rate of net nitrification within the forest floor was always low (1 kg-NO3
--N ha-1 30d-1). Mean residence times for organic matter and N in the forest floor were 13 and 34 years, respectively, suggesting that this forest floor layer is a site of net N immobilization within this ecosystem. We examined the influence of the forest floor on mineral soil N dynamics by injecting small amounts of15N-enriched (NH4)2SO4 solutions into the surface mineral soil with the forest floor present (+FF) or removed (-FF). K2SO4-extractable NO3
--N, total inorganic-N, and total-N pool sizes in the mineral soil were initially increased after forest floor removal (after 4 months), but NO3
--N and total inorganic-N were not significantly different thereafter. Microbial biomass-N and K2SO4-extractable total-N pool sizes were also found to be larger in mineral soils without a forest floor after 1 and 1.3 years, respectively. Total15N-recovery was greater in the +FF treatment compared to the -FF treatment after 1-year (about 50% and 35%, respectively) but did not differ after 1.3 years (both about 35%), suggesting that the forest floor delays but does not prevent the N-loss from the surface mineral soil of this forest. We estimated using our15N data that fungal translocation from the mineral soil to the forest floor may be as large as 9 kg-N ha-1 yr-1 (similar in magnitude to other N flows in this forest), and may account for all of the observed absolute increase of N in litter during the early stages of decomposition at this site. Our results suggest that the forest floor acts both as a source and sink for N in the mineral soil. 相似文献
8.
A pulse dilution 15N technique was used in the field to determine the effect of the ammonium to nitrate ratio in a fertilizer application on
the uptake of ammonium and nitrate by ryegrass and on gross rates of mineralization and nitrification. Two experiments were
performed, corresponding approximately to the first and second cuts of grass.
Where no substantial recent immobilization of inorganic nitrogen had occurred, mineralization was insensitive to the form
of nitrogen applied, ranging from 2.1–2.6 kg N ha-1 d-1. The immobilization of ammonium increased as the proportion of ammonium in the application increased. In the second experiment
there was evidence that high rates of immobilization in the first experiment were associated with high rates of mineralization
in the second. The implication was that some nitrogen immobilized in the first experiment was re-mineralized during the second.
Whether this was nitrogen taken up, stored in roots and released following defoliation was not clear. Nitrification rates
in this soil were low (0.1–0.63 kg N ha-1 d-1), and as a result, varying the ratio of ammonium to nitrate applied markedly altered the relative uptake of ammonium and
nitrate. In the first experiment, where temperatures were low, preferential uptake of ammonium occurred, but where >90% of
the uptake was as ammonium, a reduction in yield and nitrogen uptake was observed. In the second experiment, where temperatures
and growth rates were higher, the proportion of ammonium to nitrate taken up had no effect on yield or nitrogen uptake. 相似文献
9.
减量施氮对玉米-大豆套作系统下作物氮素吸收和利用效率的影响 总被引:6,自引:0,他引:6
为探索玉米-大豆套作系统中作物对N素吸收的差异特性,揭示减量施N对玉米-大豆套作系统的N高效利用机理。利用15N同位素示踪技术,结合小区套微区多年定位试验,研究了玉米单作(MM)、大豆单作(SS)、玉米-大豆套作(IMS)及不施N(NN)、减量施N(RN:180 kg N/hm2)、常量施N(CN:240 kg N/hm2)下玉米、大豆的生物量、吸N量、N肥利用率及土壤N素含量变化。结果表明,与MM(SS)相比,IMS下玉米茎叶及籽粒的生物量、吸N量降低,15N%丰度及15N吸收量增加,大豆籽粒及植株的生物量、吸N量及15N吸收量显著提高;IMS下玉米、大豆植株的N肥利用率、土壤N贡献率、土壤15N%丰度降低,15N回收率显著增加。施N与不施N相比,显著提高了单、套作下玉米、大豆植株的生物量、吸N量、15N丰度及15N吸收量;RN与CN相比,IMS下,RN的玉米、大豆植株总吸N量提高13.4%和12.4%,N肥利用率提高213.0%和117.5%,土壤总N含量提高12.2%和11.6%,土壤N贡献率降低12.0%和11.2%,玉米植株15N吸收量与15N回收率提高14.4%和52.5%,大豆的则降低57.1%和42.8%,单作与套作的变化规律一致。玉米-大豆套作系统中作物对N素吸收存在数量及形态差异,减量施N有利于玉米-大豆套作系统对N肥的高效吸收与利用,实现作物持续增产与土壤培肥。 相似文献
10.
The effect of incorporating cattle slurry in soil, either by mixing or by simulated injection into a hollow in soil, on the ryegrass uptake of total N and 15NH4
+-N was determined in three soils of different texture. The N accumulation in Italian ryegrass (Lolium multiflorum L.) from slurry N and from an equivalent amount of NH4
+-N in (15NH4) SO4 (control) was measured during 6 months of growth in pots. After this period the total recovery of labelled N in the top soil plus herbage was similar in the slurry and the control treatments. This indicated that gaseous losses from slurry NH4
+-N were insignificant. Consequently, the availability of slurry N to plants was mainly influenced by the mineralization-immobilization processes. The apparent utilization of slurry NH4
+-N mixed into soil was 7%, 14% and 24% lower than the utilization of (NH4)2SO4-N in a sand soil, a sandy loam soil and a loam soil, respectively. Thus, the net immobilization of N due to slurry application increased with increasing soil clay content, whereas the recovery in plants of 15N-labelled NH4
+-N from slurry was similar on the three soils. A parallel incubation experiment showed that the immobilization of slurry N occurred within the first week after slurry application. The incorporation of slurry N by simulated injection increased the plant uptake of both total and labelled N compared to mixing the slurry into the soil. The apparent utilization of injected slurry NH4
+-N was 7% higher, 8% lower and 4% higher than the utilization of (NH4)2SO4-N in the sand, the sandy loam and the loam soil, respectively. It is concluded that the spatial distribution of slurry in soil influenced the net mineralization of N to the same degree as did the soil type. 相似文献
11.
Sources of N uptake by wheat (Triticum aestivum L.) and N transformations in soil treated with a nitrification inhibitor (nitrapyrin) 总被引:1,自引:0,他引:1
Rates of N uptake by spring wheat as ammonium and as nitrate, and rates of nitrification, gross N immobilization and gross
N mineralization were measured in a pot experiment during 84 days of growth in a clay soil. Soil treatments included an unfertilized
control and addition of 15NH4NO3 or NH4
15NO3 in the absence and presence of N-serve 24E.
Incorporation of ammonium into the soil organic N pool was considerably higher in the presence compared to the absence of
nitrapyrin, but the processes contributing to this effect could not be positively identified. Both dry matter and grain yield
as well as N uptake by wheat were enhanced in the presence of the inhibitor in N fertilized soil, despite the increased immobilization
of N. On the other hand, inhibitor application had a detrimental effect on yield and N uptake by wheat in unfertilized soil.
Both ammonium and nitrate forms of inorganic N were absorbed by wheat, but nitrate uptake was dominant in the absence of the
inhibitor. The uptake of N as ammonium was higher and the uptake of N as nitrate was less, both in absolute and proportional
terms, in the presence compared to the absence of inhibitor. In addition, the proportion of N taken up as ammonium was higher
than the proportion of N as ammonium in the available N pool up to day 56 in the inhibitor treatment, which indicated a preference
for ammonium uptake by wheat.
Evidence was obtained which suggested that several factors may have contributed to the positive response of wheat to inhibitor
application in N fertilized soil, including reduced N losses, higher gross N mineralization and a physiological response due
to the proportional increase in uptake of inorganic N as ammonium. 相似文献
12.
Contributions to nitrogen leaching and pasture uptake by autumn-applied dairy effluent and ammonium fertilizer labeled with 15N isotope 总被引:1,自引:0,他引:1
The objective of this study was to compare the N leaching loss and pasture N uptake from autumn-applied dairy shed effluent
and ammonium fertilizer (NH4Cl) labeled with 15N, using intact soil lysimeters (80 cm diameter, 120 cm depth). The soil used was a sandy loam, and the pasture was a mixture
of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The DSE and NH4Cl were applied twice annually in autumn (May) and late spring (November), each at 200 kg N ha-1. The N applied in May 1996 was labeled with 15N. The lysimeters were either spray or flood irrigated during the summer.
The autumn-applied DSE resulted in lower N leaching losses compared with NH4Cl. However, the N applied in the autumn had a higher potential for leaching than N applied in late spring. Between 4.5–8.1%
of the 15N-labeled mineral N in the DSE and 15.1–18.8% of the 15N-labeled NH4Cl applied in the autumn were leached within a year of application. Of the annual N leaching losses in the DSE treatments
(16.0–26.9 kg N ha-1), a fifth (20.3–22.9%) was from the mineral N fraction of the DSE applied in the autumn, with the remaining larger proportion
from the organic fraction of the DSE, soil N and N applied in spring. In the NH4Cl treatments, more than half (53.8–64.8%) of the annual N leaching loss (55.9–57.6 kg N ha-1) was derived from the autumn-applied NH4Cl. DSE was as effective as NH4Cl in stimulating pasture production. Since only 4.4–4.5% of the annual herbage N uptake in the DSE treatment and 12.3–13.3%
in the NH4Cl treatment were derived from the autumn-applied mineral N, large proportions of the annual herbage N uptake must have been
derived from the N applied in spring, the organic N fraction in the DSE, soil N and N fixed by clover. The recoveries of 15N in the herbage were similar between the DSE and the NH4Cl treatments, but those in the leachate were over 50% less from the DSE than from the NH4Cl treatment. The lower leaching loss of 15N in the DSE treatment was attributed to the stimulated microbial activities and increased immobilization following the application
of DSE.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
R. V. Olson 《Plant and Soil》1987,97(2):189-200
Summary Field experiments with winter wheat (Triticum aestivum L.) were conducted in two years at two locations using15N-enriched (NH4)2SO4 on Smolan silt loam (Pachic Argiustoll) and Ost loam (Typic Arguistoll) soils. The objective was to relate differences in
crop utilization of fertilizer to movement and transformations of the N in a complete factorial experiment having fall and
spring applications, banded and broadcast, with and without nitrapyrin. Plant uptake of the 60 kg N/ha applied varied from
31% to 62% with greatest uptake when fertilizer was banded in the spring without nitrapyrin and least uptake from fall and
spring broadcast treatments using nitrapyrin.
Analysis of single factor effects showed greater crop contents of fertilizer N for spring than fall applications. That was
related to immobilization of the applied N. Much more fertilizer N was in inorganic forms during the period of rapid wheat
growth with spring applications than with fall. Banding the fertilizer at a depth of 0.05 m resulted in greater plant uptake
than broadcasting or banding it on the soil surface. A significant portion of the applied N was immobilized near the point
of application. That limited the downward movement of the N placed on the surface, making it less available to plant roots
than the N placed 0.05 m deep where soil moisture was more favorable.
Use of nitrapyrin resulted in lowered amounts of fertilizer N as NO3-until mid-May for fall treatments and until harvest with spring treatments. That appeared to be the reason for lowered plant
uptake when nitrapyrin was used.
Published in memory of Professor R V Olson and over 40 years of contributions and service to agriculture and soil science
(1919–1985). 相似文献
14.
Relationship between rate of crop growth at date of fertiliser N application and fate of fertiliser N applied to winter wheat 总被引:1,自引:0,他引:1
To investigate the relationship between the timing of fertiliser N applications and the N use efficiency of wheat, three field
experiments with 15N were set up on winter wheat, on three different soils in France. Different crop N demands on the day of fertiliser application
were obtained by varying either crop densities or date of fertiliser application. Labelled 15NH4
15NO3 was applied at tillering and during stem elongation. The 15N recovered from plant and soil at different dates after 15N addition and at maturity of wheat was measured. The fate of fertiliser N was rapidly determined, most of the fertiliser
N accumulated in the wheat at maturity having been taken up within a few days of application. 15N recovery by the crop at final harvest (%) varied greatly (19–55% N applied) according to crop density, soil type and date
of application. It was linearly related to the instantaneous crop growth rate calculated at the day of 15N application. The amount of fertiliser N immobilised in the soil was constant at 20 kg N ha−1, for all soil types and crop densities. Because residual mineral 15N in the soil at harvest was negligible and immobilisation was constant, the level of total 15N measured in the different N pools (soil+plant) reflected the% 15N uptake by the plant. There was consequently a negative linear relationship between the percentage of 15N not recovered for measurement, and crop growth rate (i.e. crop N demand) at date of fertiliser application. These results
suggest that crop N demand at the time of N application determines the ability of the crop to compete for N with other processes,
and may be a major factor determining the division of N between soil and crop.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
Although a high proportion of fertilizer N may be immobilized in organic forms in the soil, no studies have examined the long-term
availability of residual fertilizer 15N in forestry situations. We investigated this by growing lodgepole pine (Pinus contorta) seedlings in surface (0–10 cm) soil sample eight years after application of 15N-urea, 15NH4NO3 and NH4
15NO3 to lodgepole pine in interior British Columbia. After nine months of growth in the greenhouse, seedlings took up an average
of 8.5% of the 15N and 4.6% of the native N per pot. Most of the mineral N in the pots without seedlings was in the form of nitrate, while
pots with seedlings had very low levels of mineral N. In contrast to the greenhouse study, there was no significantuptake
of 15N by trees in the field study after the first growing season, although half of the soil organic 15N was lost between one and eight years after fertilization. This indicates the need to understand the mechanisms which limit
the uptake of mineral N by trees in the field, and the possible mismatch of tree demand and mineral N availability. 相似文献
16.
Patricia Torres-Cañabate Eric A. Davidson Ekaterina Bulygina Roberto García-Ruiz Jose A. Carreira 《Biogeochemistry》2008,91(1):1-11
Evidence for abiotic immobilization of nitrogen (N) in soil is accumulating, but remains controversial. Identifying the fate
of N from atmospheric deposition is important for understanding the N cycle of forest ecosystems. We studied soils of two
Abies pinsapo fir forests under Mediterranean climate seasonality in southern Spain—one with low N availability and the other with symptoms
of N saturation. We hypothesized that biotic and abiotic immobilization of nitrate (NO3
−) would be lower in soils under these forests compared to more mesic temperate forests, and that the N saturated stand would
have the lowest rates of NO3
− immobilization. Live and autoclaved soils were incubated with added 15NO3
− (10 μg N g−1 dry soil; 99% enriched) for 24 h, and the label was recovered as total dissolved-N, NO3
−, ammonium (NH4
+), or dissolved organic-N (DON). To evaluate concerns about possible iron interference in analysis of NO3
− concentrations, both flow injection analysis (FIA) and ion chromatography (IC) were applied to water extracts, soluble iron
was measured in both water and salt extracts, and standard additions of NO3
− to salt extracts were analyzed. Good agreement between FIA and IC analysis, low concentrations of soluble Fe, and 100% (±3%)
recovery of NO3
− standard additions all pointed to absence of an interference problem for NO3
− quantification. On average, 85% of the added 15NO3
− label was recovered as 15NO3
−, which supports our hypothesis that rates of immobilization were generally low in these soils. A small amount (mean = 0.06 μg N g−1 dry soil) was recovered as 15NH4
+ in live soils and none in sterilized soils. Mean recovery as DO15N ranged from 0.6 to 1.5 μg N g−1 dry soil, with no statistically significant effect of sterilization or soil type, indicating that this was an abiotic process
that occurred at similar rates in both soils. These results demonstrate a detectable, but modest rate of abiotic immobilization
of NO3
− to DON, supporting our first hypothesis. These mineral soils may not have adequate carbon availability to support the regeneration
of reducing microsites needed for high rates of NO3
− reduction. Our second hypothesis regarding lower expected abiotic immobilization in soils from the N-saturated site was not
supported. The rates of N deposition in this region may not be high enough to have swamped the capacity for soil NO3
− immobilization, even in the stand showing some symptoms of N saturation. A growing body of evidence suggests that soil abiotic
NO3
− immobilization is common, but that rates are influenced by a combination of factors, including the presence of plentiful
available carbon, reduced minerals in anaerobic microsites and adequate NO3
− supply. 相似文献
17.
Labelled urea or ammonium nitrate was applied to winter wheat growing on a loamy soil in Northern France. Two applications of fertilizer were given: 50 kg N ha–1 at tillering (early March) and 110 kg N ha–1 at the beginning of stem elongation (mid-April). The kinetics of urea hydrolysis, nitrification of ammonium and the disappearance of inorganic nitrogen were followed at frequent intervals. Inorganic nitrogen soon disappeared, mainly immobilized by soil microflora and absorbed by the crop. Net immobilization of fertilizer N occured at a very similar rate for urea and ammonium nitrate. Maximum immobilization (16 kg N ha1) was found at harvest for the first dressing and at anthesis for the second dressing (23 kg N ha1). During the nitrification period, the labelled ammonium pool was immobilized two to three times faster than the labelled nitrate pool. No significant net15N remineralization was found during the growth cycle.The actual denitrification and volatilization losses were probably more important than indicated from calculations made by extrapolation of fluxes measured over short intervals. However microbial immobilization was the most important of the processes which compete with plant uptake for nitrogen. 相似文献
18.
Microbial transformations of C and N in a boreal forest floor as affected by temperature 总被引:9,自引:0,他引:9
The effects of temperature on N mineralization were studied in two organic surface horizons (LF and H) of soil from a boreal
forest. The soil was incubated at 5 °C and 15 °C after adding 15 N and gross N fluxes were calculated using a numerical simulation model. The model was calibrated on microbial C and N, basal
respiration, and KCl-extractable NH4
+, NO3
−, 15NH4
+ and 15 NO3
−. In the LF layer, increased temperature resulted in a faster turnover of all N pools. In both layers net N mineralization
did not increase at elevated temperature because both gross NH4
+ mineralization and NH4
+ immobilization increased. In the H layer, however, both gross NH4
+ mineralization and NH4
+ immobilization were lower at 15 °C than at 5 °C and the model predicted a decrease in microbial turnover rate at higher temperature
although measured microbial activity was higher. The decrease in gross N fluxes in spite of increased microbial activity in
the H layer at elevated temperature may have been caused by uptake of organic N. The model predicted a decrease in pool size
of labile organic matter and microbial biomass at elevated temperature whereas the amount of refractory organic matter increased.
Temperature averaged microbial C/N ratio was 14.7 in the LF layer suggesting a fungi-dominated decomposer community whereas
it was 7.3 in the H layer, probably due to predominance of bacteria. Respiration and microbial C were difficult to fit using
the model if the microbial C/N ratio was kept constant with time. A separate 15N-enrichment study with the addition of glucose showed that glucose was metabolized faster in the LF than in the H layer.
In both layers, decomposition of organic matter appeared to be limited by C availability.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
19.
The Vertical Pattern of Rooting and Nutrient Uptake at Different Altitudes of a South Ecuadorian Montane Forest 总被引:1,自引:1,他引:0
The vertical pattern of root length densities (RLD) of fine roots (<2 mm in diameter) and nitrogen (N) uptake potential were determined at different altitudes (1,900, 2,400, and 3,000 m a.s.l.) of a tropical montane forest in order to improve our knowledge about the depth distribution of nutrient uptake in this ecosystem. At higher altitudes, precipitation rate and frequency of fog were higher than at lower altitudes while mean annual air temperature decreased with increasing altitude. Soils were always very acid with significantly lower pH at a depth of 0.0–0.3 m in mineral soil at 3,000 m (2.8–2.9) than at 1,900 and 2,400 m (3.1–3.5). The vertical distribution of RLD was very similar both during the dry and the rainy season. During the dry season the percentage of root length in the organic layer increased from 51% at 1,900 m to 61% at 2,400 m and 76% at 3,000 m. At 3,000 m, RLD was markedly higher in the upper 0.05 m than in the remaining organic layer, whereas at 1,900 m and 2,400 m RLD were similar in all depths of the organic layer. In mineral soil, RLD decreased to a greater degree with increasing soil depth at the upper two study sites than at 1,900 m. The relative N uptake potential from different soil layers (RNUP) was determined by 15N enrichment of leaves after application of 15N enriched ammonium sulphate at various soil depths. RNUP closely followed fine root distribution confirming the shallower pattern of nutrient uptake at higher altitudes. RNUP was very similar for trees, shrubs and herbs, but shallower for saplings which obtained N only from the organic layer at both altitudes. Liming and fertilizing (N, P, K, Mg) of small patches in mineral soil had no significant impact on fine root growth. We conclude that the more superficial nutrient uptake ability at higher altitudes may be partly related to increased nutrient input from canopy by leaching. However, the specific constraints for root growth in the mineral soil of tropical montane forests warrant further investigations. 相似文献
20.
Intact amino acid uptake by northern hardwood and conifer trees 总被引:1,自引:0,他引:1
Anne Gallet-Budynek Edward Brzostek Vikki L. Rodgers Jennifer M. Talbot Sharon Hyzy Adrien C. Finzi 《Oecologia》2009,160(1):129-138
Empirical and modeling studies of the N cycle in temperate forests of eastern North America have focused on the mechanisms
regulating the production of inorganic N, and assumed that only inorganic forms of N are available for plant growth. Recent
isotope studies in field conditions suggest that amino acid capture is a widespread ecological phenomenon, although northern
temperate forests have yet to be studied. We quantified fine root biomass and applied tracer-level quantities of U–13C2–15N-glycine, 15NH4
+ and 15NO3
− in two stands, one dominated by sugar maple and white ash, the other dominated by red oak, beech, and hemlock, to assess
the importance of amino acids to the N nutrition of northeastern US forests. Significant enrichment of 13C in fine roots 2 and 5 h following tracer application indicated intact glycine uptake in both stands. Glycine accounted for
up to 77% of total N uptake in the oak–beech–hemlock stand, a stand that produces recalcitrant litter, cycles N slowly and
has a thick, amino acid-rich organic horizon. By contrast, glycine accounted for only 20% of total N uptake in the sugar maple
and white ash stand, a stand characterized by labile litter and rapid rates of amino acid production and turnover resulting
in high rates of mineralization and nitrification. This study shows that amino acid uptake is an important process occurring
in two widespread, northeastern US temperate forest types with widely differing rates of N cycling. 相似文献