生态环境 2008, 17(6): 2426-2432
Ecology and Environment
http://www.jeesci.com
E-mail: editor@jeesci.com
Behavior of nitrogen in the rhizosphere of sweet pepper plant
using the rhizobox system
Wunimuren1, N. Chishaki１, Chen Nengchang1,2*, S. Inanaga１
1. Lab of Plant Nutrition, Faculty of Agriculture, Kagoshima University, Kagoshima 890-0065, Japan;
2. Pollution Control Remediation Center, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650, China
Abstract: The behavior of N in the rhizosphere of sweet pepper (Capsicum annuum L.) plant was investigated using a rhizobox system filled with a shirasu soil applied with NH415NO3 or
15NH NO .
4
3
The rhizobox consisted of one 2 mm width center compart-
ment(CC), five 1-mm width compartments（C1～C5）, and one bulk compartment （BC）on both sides of CC. Sweet pepper was
sowed and grown in CC．After six weeks of cultivation，the soil from each compartment were collected and analyzed for contents of
the soil T-N，NO3-N, water-soluble NH4-N and KCl-extractable NH4-N and their 15N excess％. The obtained results were summarized as follows:
1. Although the T-N content of soil decreased in from BC to C1 compared to before cultivation, it gradually increased from BC
toward the CC and it was higher before cultivation in the CC.
2. The NO3-N contents of soil increased from BC to C2, then rapidly decreased from C2 to CC. The ratio of NO3-N which derived from fertilizer NO3-N increased from BC toward the CC and it reached 69% in the CC. On the contrary, the ratio of NO3-N
which derived from fertilizer NH4-N decreased from the BC toward the CC and it was 7% in the CC.
3. The water-soluble NH4-N and KCl-extractable NH4-N contents of soil decreased from the BC toward the CC and the ratio of
water-soluble NH4-N to KCl-extractable NH4-N are 3:10 in all compartments. The ratio of NH4-N which derived from fertilizer
NO3-N increased from BC toward the CC, but it was only 3% in the CC. The ratio of NH4-N which derived from fertilizer NH4-N
was 47~55% in the compartments from BC to C1, but it was low at 41% in the CC.
4. The immobilization of fertilizer NO3-N reached 62% in the whole rhizobox, but the rate was lower in the CC than in the other
compartments. On the other hand, the immobilization of fertilizer NH4-N was only about 11% in the whole rhizobox, while the rate
was higher in the CC than in other compartments.
Key words: 15N; immobilization; mineralization; N behavior; rhizobox; rhizosphere; sweet pepper
CLC number: S153.6+1
Document code: A
Article ID: 1672-2175（2008）06-2426-07
In the previous report, the behavior of N in
paddy field applied 15N-labeled NH4NO3 (NH415NO3
or 15NH4NO3) were studied and it was revealed that
immobilization and mineralization of N is actively
being carried out in the rhizosphere of rice than in
the non-rhizosphere[1]. However, since paddy field
soil under reduction condition is significantly different from upland field soil in terms of the physical
and chemical properties of soil[2-3] and microflora
(Ishizawa and Toyota, 1964; Takai and Tetsuka,
1964)[4-5], it is likely that the behavior of N under
upland field or paddy field are different.
In this study, in order to clarify the behavior of
N in the upland field, sweet pepper was cultured in
Received date：2008-08-26
*Corresponding author: ncchen@soil.gd.cn
rhizobox filled with shirasu soil applied with
NH415NO3 or 15NH4NO3 and nitrification inhibitor.
1
1.1
Material and Methods
Setting-up the rhizobox
In this experiment, similar soil and rhizobox
were used just as in the previous report[1]. As fertilizers, 1.0 g N worth of NH415NO3 (15NO3-N treatment) or 15NH4NO3 (15NH4-N treatment), and 0.5 g
K2O worth of KCl, 0.5 g P2O5 worth of Na2HPO4
were added to each rhizobox. The 15N excess% of
the applied NH4NO3 was 30.1% in both 15NO3-N and
15NH -N. As nitrification inhibitor, 4.0 mg 2-amino4
4-chloro-6-methlpyrimidine [0.4 ％ of applied
N[6]was added with the fertilizer.
乌尼木仁等：利用根箱法解析甜椒根际土壤中氮的行为
2427
Table 1 DW, N content and 15N excess% of sweet pepper
1.2 Plant Culture
Five sweet pepper seeds were sown in the CC of
the Rhizobox. During the experiment, the moisture
potential of the soil was maintained about the 60% of
maximum water holding capacity (WCH) by supplying deionized water uniformly over the soil surface every day, and the sweet peppers were grown in
a green house from May 10 th to June 22nd 2002.
1.3 Sampling and analyses of soil and plant
After experiment, the sweet pepper’s tops were
harvested and dried in an oven at 70 ℃ for threes
days. The rhizobox was dismantled to collect the soil
samples from each compartment. The roots were
taken out carefully and the soil attached to them was
shaken off, and the roots were washed with distilled
water and dried in an oven in the same way as the
top samples. The soil was collected from each compartment as fresh soil to be used as samples.
The N content of plant and their 15N atom%,
and the soil T-N, NO3-N, water-soluble NH4-N, KCl
extractable NH4-N and their 15N atom% were measured in a similar way indicated in the previous report[1]. Moreover, the 15N excess％, the ratio and
content of N in sweet pepper derived from fertilizer,
N amount in soil of each compartment derived from
fertilizer or soil, immobilization amount of fertilizer
N were calculated in a similar way to that indicated
in the previous report. Each data from the figures and
tables also has been indicated in a same way as in the
previous report[1].
2
Top
Root
5.52±0.09
1.31±0.05
N content (%)
4.48±0.13
4.01±0.13
N uptake(mg rhizobox-1)
242.0±7.19
52.5±1.68
15N excess%(15NO -N treatment)
3
14.94
10.82
6.34
9.23
15
N excess%(15NH4-N treatment)
Values are mean ±s.d.（n＝2）
Values are mean ±s.d.（n＝2）
Sweet peppers grown for six weeks in the Rhizobox looked healthy and there were no disorders
such as malnutrition or flowering found. As shown in
Table 1, the 15N excess％ in the top and the root of
sweet pepper was higher in the 15NO3-N treatment
than in the 15NH4-N treatment, and the 15N excess％
level was higher in the top than in the roots in the
15NO -N treatment and higher in the root than in the
3
top in the 15NH4-N treatment.
2.2 Soil T-N content and its 15N excess％
Fig.1 shows the soil T-N and its 15Ｎ excess％
in each compartment. Although the soil T-N gradually increased from the BC to the CC, it was lower
compared to the former cultivation from the BC to
C1 and high in the CC (Fig.1-A). The 15N excess％
of soil T-N was higher than before cultivation from
C5 to C1 in the 15NO3-N treatment, but it rapidly
decreased in the CC. In the 15NH4-N treatment, the
15N excess％ of soil T-N was lower than the former
cultivation and it decreased from the BC to the CC
(Fig.1-B).
2.3 Soil NO3-N content and its 15N excess％
Fig.2 shows the soil NO3-N content and its 15N
excess％ in each compartment. The content of soil
Results
2.1 Plant growth, N content and its 15N excess％
in plant
7.0
A
2.5
e
2.0
a
b
1.5
b
c
cd
d
15 N
1.0
excess% in total-N
3.0
Total-N(g ｋg-1 )
Items
Dry weight( g rhizobox-1)
0.5
0.0
6.0
△ 15NO3-N
B
◆15NH4-N
5.0
4.0
3.0
2.0
1.0
0.0
BC
C5
C4
C3
C2
C1
CC
BC
C5
C4
C3
C2
C1
CC
Fig. 1 Distribution of soil total-N and their 15N excess% around the CC after sweet pepper cultivation. Different letters indicate significant differences at 5%
level according to the Fisher's PLSD test. The error bars indicate the differences of 15N excess% values between right and left sides of CC. The dotted lines in
figures A or B indicate values of total-N or 15N excess% in total-N before sweet pepper cultivation, respectively.
生态环境 第 17 卷第 6 期（2008 年 11 月）
2428
200
25
e
B
160
120
d
d
80
N excess% in NO3 -N
20
c
40
b
a
△
15NO -N
3
◆
15NH -N
4
15
10
15
NO3 -N (mg kg-1 )
A
b
5
0
0
BC
C5
C4
C3
C2
C1
BC
CC
C5
C4
C3
C2
C1
CC
Fig. 2 Distribution of soil water-soluble NO3-N and their 15N excess% around the CC after sweet pepper cultivation. Different letters indicate significant
differences at 5% level according to the Fisher's PLSD test. The error bars indicate the difference of
excess% value of NO3-N in
b
200
b
b
bc
c
d
150
100
50
0
BC
C5
C4
C3
C2
C1
a
80
CC
b
b
b
b
c
60
d
40
20
0
BC
C5
C4
C3
C2
C1
CC
Fig. 3 Distribution of soil water-soluble NH4-N around the CC after
sweet pepper cultivation. Different letters indicate significant differences at
5% level according to the Fisher's PLSD test. The dotted line indicates
value of water-soluble NH4-N before sweet pepper cultivation
exess% in KCl-extractable
NH4 -N
a
excess% values between right and left sides of CC. The
treatment before sweet pepper cultivation, respectively
△ 15NO3-N
B
25
300
250
15N
100
A
350
15NO -N
3
decreased in all of the compartments in the 15NO3-N
treatments. In the 15NH4-N treatment, it showed an
almost uniform level from BC to C2, but it gradually
decreased from C2 to CC (Fig.4-B).
15 N
KCl-extractable NH 4 -N(mg kg-1 )
NO3-N increased from the BC to C2, then rapidly
decreased from C2 to the CC (Fig.2-A). As for the
15N excess％ of NO -N, it was lowest in the BC in
3
the 15NO3-N treatment, but it increased from BC up
to the CC and showed a level which was similar to
before cultivation in the CC. In the 15NH4-N treatments, it rapidly decreased from BC to C5, gradually
decreased from C2 to CC (Fig.2-B).
2.4
Soil water-soluble NH4-N content, soil
KCI-extractable NH4-N content and its 15N excess％
Fig.3, Fig.4 show the soil water-soluble NH4-N
content, the soil KCI-extractable NH4-N content and
its 15N excess％ in each compartment, respectively.
The content of soil water-soluble NH4-N and
KCI-extractable NH4-N decreased from BC to C5
and from C2 to the CC, and the ratio of water-soluble
NH4-N and KCI-extractable NH4-N was about 3:10
in all of the compartments (Fig.3, Fig.4-A). The 15N
excess％of KCI-extractable NH4-N was significantly
Water-soluble NH4-N(mg kg-1)
dotted lines in figure A or B indicate NO3-N value or
15N
◆15NH4-N
20
15
10
5
0
BC
C5
C4
C3
C2
C1
CC
Fig. 4 Distribution of soil KCl-extractable NH4-N and their 15N excess% around the CC after sweet pepper cultivation. Different letters indicate significant
differences at 5% level according to the Fisher's PLSD test. The error bars indicate values of 15N excess% at right and left sides of CC. The dotted lines in figure
A or B indicate values of NH4-N or 15N excess% value of NH4-N in the 15NH4-N treatment before sweet pepper cultivation, respectively
乌尼木仁等：利用根箱法解析甜椒根际土壤中氮的行为
2429
2.5 N amount by the morphology in the soil and
N amount in sweet pepper which derived from
soil
Table 2 shows the N amount by morphology in
the soil of each compartment and N amount in sweet
pepper which derived from soil. Compared to before
cultivation, the amount of soil total-N which derived
from soil decreased about 47 mg in the BC, but in
the CC increased about 37.4 mg (18.7×2). In each
compartment, organic N made up for over 90% of
the total-N which derived from soil and it was the
highest in the CC at 96%. However, the ratio of
NH4-N which derived from soil was significantly
high in the BC and low in the CC. Moreover, there
was less NO3-N which derived from soil than that of
NH4-N, and it was about 1%~2% of total N amount
which derived from soil in all of the compartments.
2.6 N amount by morphology in the soil and N
Table 2
in the sweet pepper plant which derived from fertilizers
Table 3 and Table 4 show the N amount by
morphology in which derived from fertilizer NO3-N
and NH4-N, respectively. The amount of total-N
which derived from fertilizer NO3-N decreased by
71.3mg in the BC and by 7.8mg (3.9x2) in the CC
compared to before cultivation, but it increased from
C5 to C1. In the whole Rhizobox, fertilizer NO3-N
decreased by about 136mg, and this decrease was
approximately consistent with the amount absorbed
by the sweet peppers. Among the total-N which derived from fertilizer NO3-N residual in the soil, about
86% was organic N and only 12% was found as
NO3-N. In terms of each compartment, NO3-N,
NH4-N and organic N were highest in the BC, and
there were less NO3-N and organic N in the CC
compared to the other compartments in proximity
Amounts of NO3-N, NH4-N and organic-N in soil of the compartments derived from soil-N
mg
compartment
NO3-N (A)
NH4-N (B)
Organic N (C)
Total-N (A+B+C)
BC
14.8±2.23(26.81)
150.5±5.24(54.19)
1622±37.5(1753)
1787±14.9(1834)
C5
0.78±0.07(0.96)
4.33±0.14(1.95)
59.48±0.48(63.1)
64.59±0.69(66.0)
C4
0.69±0.08(0.96)
4.10±0.02(1.95)
58.13±1.57(63.1)
62.92±1.59(66.0)
C3
1.13±0.26(0.96)
4.76±0.05(1.95)
58.60±0.34(63.1)
64.49±0.58(66.0)
C2
1.28±0.26(0.96)
4.08±0.03(1.95)
59.27±1.99(63.1)
64.63±2.28(66.0)
C1
0.91±0.12(0.96)
4.32±0.07(1.95)
60.58±0.62(63.1)
65.81±0.81(66.0)
CC
0.43±0.05(0.96)
3.44±0.08(1.95)
80.81±1.48(63.1)
84.68±1.72(66.0)
Total*
40.04±6.14(65.20)
351.1±11.26(131.8)
3997±87.98(4263)
4388±45.14(4460)
N uptake(mg rhizobox-1)
89.2±8.8
For comparison with CC and other compartments, N amount of CC show a half of obtained N amount. Values are mean ±s.d.(n=4 except CC (n=2)). The
values in the parenthesis indicate N amounts before sweet pepper cultivation. * These values show N amounts in the whole rhizobox.
Table 3
Amounts of NO3-N, NH4-N and organic-N in soil of
the compartments derived from fertilizer NO3-N
com-
Table 4
mg
NO3-N (A)
NH4-N (B)
Organic N (C)
Total-N (A+B+C)
BC
10.94±1.23
3.34±0.18
120.0±2.85
134.3±4.26(205.6)
C5
0.99±0.06
0.19±0.00
6.36±0.10
7.54±0.16(7.4)
C4
1.20±0.06
0.16±0.00
7.46±0.05
C3
2.19±0.08
0.19±0.01
6.37±0.08
C2
3.21±0.14
0.15±0.00
C1
2.17±0.06
0.17±0.01
CC
1.16
0.22
partment
Total*
43.9±3.36
N uptake(mg rhizobox-1)
8.94±0.40
Amounts of NO3-N, NH4-N and organic-N in soil of the
compartments derived from fertilizer NH4-N
com-
mg
NO3-N (A)
NH4-N (B)
organic N (C)
Total-N (A+B+C)
BC
19.41±1.00
140.8±5.06
21.19±4.40
181.4±1.7(205.6)
C5
0.41±0.01
4.56±0.14
0.96±0.02
5.93±0.17(7.4)
8.82±0.11(7.4)
C4
0.43±0.02
4.71±0.00
0.61±0.02
5.75±0.00(7.4)
8.75±0.22(7.4)
C3
0.71±0.04
4.08±0.05
1.14±0.05
5.93±0.05(7.4)
5.78±0.04
9.14±0.10(7.4)
C2
1.11±0.12
4.30±0.03
0.36±0.04
5.77±0.11(7.4)
7.35±0.25
9.69±0.32(7.4)
C1
0.56±0.06
3.31±0.06
0.88±0.10
4.75±0.22(7.4)
2.16
3.54(7.4)
CC
0.11
1.99
1.99
4.09(7.4)
364.1±10.7(500)
Total*
45.48±2.50
327.5±10.66
54.32±9.26
427.3±4.50(500)
311.3±6.90
138.4
partment
N uptake(mg box-1)
66.8
For comparison with CC and other compartments, N amount of CC
For comparison with CC and other compartments, N amount of CC
show a half of obtained N amount. Values are mean±s.d.(n=2). The values
show a half of obtained N amount. Values are mean ±s.d.(n=2). The values
in parenthesis indicate N amounts before sweet pepper cultivation. * These
in the parenthesis indicate N amount before sweet pepper cultivation. *
values show N amounts in the whole rhizobox.
These values show N amounts in the whole rhizobox.
2430
(Table 3). The amount of total-N which derived from
fertilizer NH4-N decreased by about 73 mg in the
whole Rhizobox, and 66.8 of it was absorbed.
Among the N which derived from fertilizer NH4-N
residual in the soil, about 77% was NH4-N and the
ratio of organic N from the BC to C1 was low at
7%~19%, but it reached almost 50% in the CC.
Moreover, the ratio of NO3-N which derived from
fertilizer NH4-N was only 11% in the Rhizobox as a
whole and its level was high in the BC and low in the
CC (Table 4).
3
Discussion
In this study, nitrogen inhibitor was added to
analyze the dynamics of NH4-N in the upland field.
Since the amount of NO3-N which derived from fertilizer NH4-N in the after culture soil was less than
10% of the additive amount of NH4-N (Table 4), it
appears that the nitrogen inhibitor had a substantial
effect. Moreover, just as in the previous report[1], the
debate will be advanced on the CC where the sweet
peppers were grown as the rhizosphere.
The 15N excess％ of N in the sweet peppers
was higher in the 15NO3-N treatment than in the
15NH -N treatment, and it was higher in the tops than
4
in the roots in the 15NO3-N treatment and higher in
the roots than in the tops in the 15NH4-N treatment
(Table 1). These results suggest that sweet pepper is
a nitrate-loving plant and that fertilizer NO3-N is
used more in the top than in the roots and fertilizer
NH4-N is used more in the roots than in the top of
sweet pepper.
Moritsuka et al.( 2000a)[7] grew maize and kidney beans for 17 days in a growth chamber at 25 ℃
using rhizoboxes under no-fertilizer conditions and
studied the soil T-N and found that there was hardly
any change in all of the compartments. However, in
this experiment applied with N, the soil T-N content
was lower in the non-rhizosphere than before cultivation, but it increased towards the rhizosphere and
become higher than before cultivation in the rhizosphere (Fig.1-A). As a result of separating the soil
T-N according to the total-N which derived from the
soil and fertilizers, the total-N which derived from
the soil drastically increased in the rhizosphere (Table 2), but the total-N which derived from fertilizer
NO3-N and NH4-N significantly decreased in the
rhizosphere and they were less than the levels found
生态环境 第 17 卷第 6 期（2008 年 11 月）
near the rhizosphere (Table 3 and Table 4). These
results indicate that the content of soil T-N increased
in the rhizosphere of sweet pepper unlike results of
maize and kidney bean were due to the soluble N
compound which produced in the non- rhizosphere
were moving and accumulating in the rhizosphere.
The content of soil NO3-N rapidly increased
from the BC to C2, but it drastically decreased from
C2 to the rhizosphere (Fig.2-A) and showed a
movement which was different from barley[8] which
significantly increased near the rhizosphere and
maize[10] which decreased near the rhizosphere. Furthermore, the amount of total-N derived from fertilizer NO3-N residual in the soil greatly decreased in
the BC compared to before cultivation and increased
from C5 to C1, but it significantly decreased in the
rhizosphere (Table 3). The above results suggest that
although NO3-N moved by mass flow from BC to
rhizosphere, the absorption rate of NO3-N by sweet
peppers in the rhizosphere was greater than the
moving rate by the mass flow and its affect had
reached C1. Moreover, the content of NO3-N and its
15N excess％ also drastically decreased in the BC
compared to before cultivation （Fig. 2-A，Fig. 2-B）
indicates that although NO3-N is supplied from the
soil as well as fertilizer NH4-N （Table 2, Table 4）,
its supply rate is slower than the moving rate of
NO3-N by mass flow.
Cai et al. reported that the soil water-soluble
NH4-N decreased significantly up to 2mm from
root-surface of wheat[10] and barley[11] and speculated
that it was largely due to the diffusion of NH4-N to
the rhizosphere caused by the absorption by the roots
or the nitrification activity in the rhizosphere. In this
study, water-soluble NH4-N also showed a movement similar to maize and barley (Fig.3). However,
since the ratio of NO3-N which derived from fertilizer NH4-N in the rhizosphere of sweet peppers was
lower than that of non-rhizosphere (Fig.2-B), the
diffusion of NH4-N to the rhizosphere was more
likely to be the main contributing factor of decreased
water-soluble NH4-N around the rhizosphere of
sweet pepper. When NH4+ is absorbed and lessens in
the soil solution, NH4+ attached to the soil particles is
released[12] and an equilibrium relation is established
between the water-soluble NH4+ and the amount of
solid-phase absorption[13]. In this treatment,
乌尼木仁等：利用根箱法解析甜椒根际土壤中氮的行为
KCI-extractable NH4-N also showed a similar
movement to water-soluble NH4-N and they were
both present at a ratio of about 10:3 in all of the
compartments, indicating that an equilibrium relation
is established between them (Fig. 3, Fig. 4A).
The immobilization and mineralization of N in
the rhizosphere and non-rhizosphere soil will be debated by analyzing the 15N excess％. First of all, the
ratio of NO3-N which derived from fertilizer NO3-N
was about 25% in the BC, but it increased the closer
it got to the rhizosphere which reached 69%. Meanwhile, the ratio deriving from fertilizer NH4-N was
43% in the BC, but it decreased to 7% in the rhizosphere (Fig.2-B). When these are summed, the ratio
of NO3-N which derived from fertilizer N reached
65%~78% and 76% in the non-rhizosphere and rhizosphere, respectively. As reported in the previous
report[1], in the case of rice, the ratio of NO3-N which
derived from soil N was 35%~55% in the
non-rhizosphere, but it reached 94% in the rhizosphere, which is higher than the rate of sweet peppers. Moreover, in the whole rhizoboxes, although
the immobilization rate of fertilizer NO3-N reached
62%, the rate was lower in the rhizosphere than in
the non-rhizosphere at about 30% (Table 3). In the
rhizosphere of crops, there are many more microorganisms than in the non-rhizosphere and nutrient
metabolism is also more actively carried out[14-16].
The fact that the mineralization of soil N in the rhizosphere of sweet peppers was not much different
from that of the non-rhizosphere (Table 2), but the
immobilization of fertilizer NO3-N was less than in
that of the non-rhizosphere suggest that the absorption rate of NO3-N by sweet peppers was faster than
the supply rate from the non-rhizosphere and its immobilization rate of NO3-N in the rhizosphere.
As for KCI extractable NH4-N in the soil, the
ratio deriving from fertilizer NO3-N increased the
closer it got to the rhizosphere, but was 1%~2% in
the non-rhizosphere and about 3% in the rhizosphere
(Fig.2-B). Although the ratio deriving from fertilizer
NH4-N was 50%~56% in the non-rhizosphere, it decreased to 44% in the rhizosphere (Fig.4-B) and the
ratio of NH4-N which derived from soil N in the rhizosphere was higher than that of the non-rhizosphere.
Meanwhile, immobilization of fertilizer NH4-N in
the rhizosphere was higher than the level found in its
2431
proximity (Table 4). These results suggested that the
mineralization of soil N into NH4-N and immobilization of fertilizer NH4-N were more active than in the
non-rhizosphere. However, the residual ratio of fertilizer NH4-N in the rhizoboxes as a whole was 85%,
but its immobilization rate was only 11%, indicating
that NH4-N was harder to immobilize than NO3-N in
upland field (Table 4).
As described, the immobilization rate of fertilizer NO3-N in the rhizosphere of sweet peppers was
about 30% (Table 3), while the ratio of NO3-N which
derived from soil was about 25%. In contrast, in the
rhizosphere of rice[1] the immobilization rate of fertilizer NH4-N was 50% and the ratio of NH4-N which
derived from the soil was 85%, suggesting that the
immobilization and mineralization of N in the rhizosphere of sweet peppers were significantly slower
compared to those of rice. Although the contribution
of fertilizer N was about 70% with sweet peppers,
the rate was about 56% with rice, supporting the old
patois that “rice is grown by soil fertility and wheat
gets its nutrients from fertilizer[17].
References:
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利用根箱法解析甜椒根际土壤中氮的行为
乌尼木仁 1，樗木直也 1，陈能场 1, 2，稲永醇二 1
1. 日本鹿儿岛大学农学部植物营养实验室，鹿儿岛 890-0065 日本；
2. 广东省生态环境与土壤研究所，广东 广州 510650
摘要：为研究甜椒根际土壤中氮的行为，与既报同样的方法进行研究，即，利用
15NH NO ）
4
3 ，在温室里对甜椒进行
的
15N
15NH +，15NO -双标记的硝胺（NH 15NO ，
4
3
4
3
6 周的根箱栽培。收割后，对土壤全氮，NO3-N, 水溶性 NH4-N，KCl 抽出 NH4-N 和其各自
atom％进行测定。结果表明，土壤全氮从非根际到根际逐渐增加，与栽培前相比，土壤全氮在非根际中减少，却在根际
中增大。土壤 NO3-N 浓度朝根际增加到离根际 2 mm 处，然后激减到根际。NO3-N 的来自施给 NO3-N 的比例靠近根际逐渐升高，
在根际达到了 69％，反而，来自施给 NH4-N 的比例靠近根际逐渐降低，在根际将至 7％左右。水溶性 NH4-N 和 KCl 抽出 NH4-N
浓度靠近根际逐渐降低，而且，从非根际到根际，二者匀保持 3∶10 的比例。KCl 抽出 NH4-N 的来自施给 NO3-N 的比例靠近根
际逐渐升高，但在根际仍低于 3％，反而，其来自施给 NH4-N 的比例在非根际约为 47%~55%，在根际降到 41%。在整个根箱里，
施用 NO3-N 的有機率达到 62％，但其值在根际比非根圏要低。相反，施用 NH4-N 的有機率仅 11％左右，但其值在根际比非根
际要高。以上结果表明，在甜椒根际土壤中氮的无机化-有机化活性与水稻相比显著低。
关键词：15N; 有机化; 无机化; 氮的行为; 根箱; 根际; 甜椒