
J. Jpn. Soc. Soil Phys.
rs 
No. 21, p. ,1-0 ,**+





*ῌ**ῌ ***Experiment on the Nitrate Removal in the Flooded Paddy Field
Toshio TABUCHI*, Hisao KURODA** and Motoko SHIMURA**** Former professor of The University of Tokyo** Faculty of Agriculture, Ibaraki University*** Chugoku National Agricultural Experimental Station
Abstract
Recently nitrate outﬂow from the agricultural area became one of big problems in Japan. We
continue the long term experiment on nitrate removal in the ﬂooded paddy ﬁeld from +33+.
Experimental plots consist of four plots ; weed plant, rice, non-plant and covered plot. In the
non-plant plot any plant does not grow, but some of algae grow.

In the covered plot, no algae

grows due to the shield of the light. Natural water with high nitrate concentration about ,* mg
Lῌ+ are supplied to each plot continuously. Nitrate is removed through the ﬂow process in theplots by denitriﬁcation and the uptake by the plant. Average values of nitrate removal rate for
2 years are *.-* gm , d + in a weed plot and *.,1 gm , d + in a rice and a non-plant plots. Nitrate
removal rates gradually decreased in the ﬁrst few years, but now they keep the ability of nitrate
removal after 3 years.

In order to clarify the inﬂuence of plant growth and algae on nitrate

removal these data are examined by the nitrate removal equation as shown in eq. (,), whichindicates the relation between the nitrate removal by denitriﬁcation (Ro) and nitrate concentration of water (X) and temperature (T).
Key words : Nitrate removal, Denitriﬁcation, Plant growth, Paddy ﬁeld+    

!"#$"%&'( +333 $))*+73)mn$oU(  "6j)p)"5 "?qrs_B^l4
tuvwT vx3( Q"'tuyC7zC M +332 aN5,-./0$12345 67)

{3)|}~9G|wQ3tu

89:;<=$"'( >9 "?( ( ]Bl M3 +321(

$@AB 2C5 3$ DEF9G HI+33-N( 3$JKL$"C M3 +332 aN5zl4 M +332 bN5 4 +33+ Q3$4

PBvx$

64O PQ3BR7 !"S

vwtuB( 6B#$"'( T PU$EF PVBWX

kl!4 M3 +33-( +330( 3 ,***N5 

YCZ[C5 6\]^_8`a)6 3 $&vwn$$l( qrs_tu$ ¡¢l45

PJb9cdefg$hLi

C BjiC7kO3C5 lQl* £¤¥ bb!¦§** ¨© bb! ª-**ῌ*-3- ¨©«¬"­®¯°\± -ῌ,+ῌ+*** #²³\´ vwµ ª1,+ῌ2/+. o¶«$·¸¹º» 0ῌ+,ῌ+: tu( ¼( ]( z:ST¤ U 21 ¼ S,**+U28,ῌ ῐ῏῍῎ΐ,+ 

ῑ+   ,/ m  +.. m   
-/ m,   /    !"#$%&'()*+ +33+ ,-.  /&012 + 3%2+/ mLsῑ+ "4&*+ 02 -1 mmdῑ+ 5  "'6789:2; +7<=> ?@:7; 9 &*+ +333 ABCDEF2 1.1 mmdῑ+ "G HIJ 2 K!L"7M89 # ,* mgLῑ+ "ῑῌ+2ῌ NO ῍ A ῎ $% ῏ ῌP

Fig. +



Experimental plots

ῐ &QR ST'U "VW(X*+ YNOZ 2N

O R[7\\()&" ]2NO2^_ῒῌ+R`&*2a\\+?bX NOc'2d

Table +

e fg hiij k" YAZ 2A &,-Jvw£¡N O ;
»QRnS@1t<U

t<

 A 

;
»AnSno1@ῌt<U



&QR
ST ' U;»T'nS@1t<U

@

ῌ P 

;

;

&./"lQm0& no pGqrs2a
\\t Y&QRZ 2QR R`() +NO2uvw&*xG" &&T
71R&*+* ayz72/+" YT'Z 1>+[ aX"3{M&QR|"G῏  +331  1 }~ῌP SῌP4 2*῍U)>BThe features of each plot*T'1R 5& YῌPZ 1&
.K /  "NO A &QR - 

¢



!

76 "" 67"2a 
3{8&*9  :"Jvw2;

Y;Z 1+G>  017"/ a0

1QRn :t< - =JG*X1

17¡¢£Jvw¤Ek¥F

X7 K - 2 G> > S?ῑ+U10¦" ? YNOZ 2;>7QRn>2/+,, G

NO2no(X +"4 2@(X7  ~#C§ ABC1HABC@*vw

@2t<1X @~RJ2¨M YABCZ 2A"Q[  / }K© A~ aq;&~ a>B2Q

pª~ 3 } ©\"# +-* I§"7 J« + ¬Rnt<~ t<1+[ YAZ 2

C­ G YHABCZ 2pª~K;An7~ aX2noG

Q[\"C§"*rs.<2<?(X rs2t<7C­¬¯2# -** ¬ 

1k7@1X a>B2no®« + ¬­" 3 §

'°L"Jvw2#M ῌ 

?&" Y&QRZ "2;T'n HIJ

77 aX2C"@(X* AJ ¨M a±²& M HI

~ ;  tD2; +1X >BJ2³´J 3*῍ .K

2@ YῌPZ 2QR> 9 T'1R>5"2 2*῍ .K­& a "MῌHIµM µM &7G*¶¬N·"2H

(X*+";xvw" &7G

IJ"Jvw

*;2#"> QR12O¸²& \#M

 ~ aXX Yt<Z YZ Y@;Z

MO1O" pH 1 DO 

§O O - O"¹1PºQR­&SECU 

ῑ· : ¸¹ºc»§¼.HI

ῒῌ,

O

3

Table ,

29

C (+33+, /+333, +,*

Average values during 3 years
´µ

PQ8

;,8

E>?8

joop;<῎
gm, d+ῌ®¶+24*4-*
.341

,,41
*4,1
.-4.

,-43
*4,1
..4.

῎

O

C

+33+ῌ+332(Rῌ,*+;,8STU῎VW -XYZ .

tha+ [\ ]!^^_`' ()ῌ-*+Yabc%&5&:YYdZeUf g&%&'+-ῌ ῐ ῏ ῎ ῍-+ ;<#h)ῌ.

O\.i\jkl , mn8op3q;<#hcr:'+ n8/:s=3t
ῑῌ,Fig. ,

῎

&uv#hcr%&'+ w

#$xt^ +33-

Changes of nitrate removal in each plot

zPQ8{ ;<:3 s;< +33+῏s)y%&'+Qj|5'}~8D6-* lCcrF+ s zE>?8{.* : ~8D6:=&+ y j|5&}'+ z;,8{῍oOCcrF

 , %&5&m. E>?8C!&+ 3
Oi\C

E>?8 ,-.3 ;,8,,.1 PQ8 +2.- /125K?M (R ῌ,*+zῌ8{  ῌc} +331

1 YZ;<&+ 59)ῌ. o. +33, +33.

W5&  ;Xw6^
ῐ;D';῎5&i\?M}
ῑῌFig. -'+;,8:U῎#hsi\ + mOO;<#hc'/Change of the yield of rice()ῌ/* z;,8{ ^ zE>?8{  ]=;</];

</K
῎
  

 *../ gm, d+ 
*.,**.,/ gm, d+ !"#$%&' ()ῌ,*+ ,-./0,-. ῎ 123456 789&%:;<=3 >??@AB5,-.C0,-.CD6:12&+ /3
E>?8C.D6123#$F'+ 1G/%- HI8῎ J6K53 LMDN5#$%&'+ 2
,

gm

+

 +* + %j;< \.i\m;<D6: / &/

,- ῎OC

PQ8 *.-*,d  ;,8/E>?8 *.,1 gm

d

+



5'+

yn¡/j;</\.i\m;<¢c£}%92 l¤F'¥¦§&'j;<¢c¨%i\m;<YZ©ª%£}+-, «¬­®#hz;,8{ ῌ¯;/ῌ°;«¬­®#hc)ῌ0 r+ ῌ¯;®,* mgL+ l±²

+³\ =&m ,/ mgL  &m +/ mgL+ '+
ῌ°;«¬­® uvD%123#hF   21  I,**+K

30

ῌῌ/Fig. /

N- I +331 7 2 K

Hourly changes of water temperaturein summer

ῌῌ0 %&'()
1
IcD ; 4K
Fig. 0Changes of NO--N concentration in arice plot>>3 Xo CD

 X 4

3=*    NOP Q2 IR῍1K
STUDV 3W7

+33+ 7*

+**ῌ XYZ, 5 [ 2*ῌ \63= ῌῌ.
Fig. .

N I] +33/ 7^_W.`a#bE *ῌ X

 [ , -K

Changes of water temperature in center
parts

YZ
ScDV 3 STUDV OPd+ Q2, *ῌ Xef, STUDV gh#    

 









  !"# -$- %&'()

 %&'()
3 4

oF,-./012

5 6637 892 :;*3CD 7 892

 6Z +33/ 7^_3.

D3

*W.`a##, pqrs

tu,v #m ()wxyz{v#  Sῌ|DV 3ῌ| }~Z +331 7  .*ῌ ^3  *ῌ YZ* b ?@3ABEF
bGHIXoJXKῌXoLM+**n +330 7  ],], *ῌ >,ghZ > * +<3= 5>3?@3AB2%&'()

SijkDV 3Ol d+ Q2, +33/ 7m

IῌK

-$.
ῌ

pH

ῌ|D Z +331 7 1  +332 7 - 63  : 

_h31

῏ῌ2 pH DO COD y +331, 1+332, -Fig. 2

῏ῌ1
Fig. 1

6Jh]OLk b y

Decreased ratio b of NO--N concentration

Changes of the values of pH, DO and
COD

mgL`+ )* !"#$% ,L  ῌF

e_L /mg L`+ NO&' ῌFP pH  ῌ2

 

+* ++ d - d W/ !ῌF%  DO 
3$



12fg

 : 6h789/ ;</ !XY%  XYlmnfg ;</3 )*!"#$% &' (+,-./ 0/

123$  456789/ :;<
/ =

1

>

 +?@i/9<L / mgL`+ jk0'0SDO  opqfg12 rs

tuvw& x R
-\0

COD ]OA  BC DE !ῌF%GH"#$IJ&'<13$K :!"#]O  "#$(_ $% L !M% GHNO 1 PQ 1 opq${|}/0

R 0S 12 pH TUVW/
!XY%

1 L 4&DELῌ2

COD ]Oyz

R ~ XY+ =_  lmnfg *</ 0S  A Z[& 123.ῌ ῍

$?@UV 
-\/

DO ]O

ῌ2

 ῎.\+ ]OLk

G^_ DO ]O

 !"#$%ῌ3]OL

 +* mgL`+ )* abcIJ&' 0/1k 

23$/]OLk ?@ :;</ !M%  +* tu '

|}£¤¥ e 21 ¦ X,**+Y

32

ῌῌ3

 
*.1,





*.10

¡¢

5#$%&' b 

Relationship between decreased ratio b and water temperature

Fig. 3

*.0+

 

ῌ *..+ 

 ,*  /2῍ !"#$%&'   ( .-῍ )*+ ῌ ,-./012%+#$%&')*+* +.῍  3.4 567)+89:; -<=>?@;*A)4. -BCDEFGHIJ*KLMNO0P;Q*+R.S῏+*   

T7 5#$%&'UVW X+33+῏3-Y ZW X+33.῏30Y BW X+331

ῌῌ+*

¡¢

Fig. +*

Change of regression lines in a nonplant plot

῏33Y  - [\]7*^_*`+0 VW

5#$%&'
X YZW a.BWP;/ bcNO;de%&J*f*+
.g, LMbch#$%&' bo ijklMFbcLMm4<=>?
@*0no-*+ ,ῌ=>?@L
MpU8D_LMbcpUijJ*
PqrUns LMbcpijtu;vwJxyz5{|}~T7&LMbch

Xtu. +321+332 bY U++33-

LMbc$ Ro Xgm῏,d῏+Y { ZMF#$
X XmgL῏+Y  J &1dha-

J

ῌ

RoaX
a |}< 5/D*+tt|}ds.;
5T,dh*a- Xtu. +33-Y
a*.****++ T,*.**/

XT+*

Y

῍

{ ZMF#$0%&D; -dha-
XXo exp X῏ atῌHY῎,, Xo VW#$ t  XdY H   XmY & pU Q Xm-d+Y U A Xm,Y# : ¹º$ » A¼²|

33

ῌῌ+,
ῌῌ++

9:
[

1AFG a %&Fig. ++

Change of removal coe$cients (a) withtemperatureb  bo t %Comparison of b with bo in a rice plot

Fig. +,

p@*qr-jk/.s-bo  b tTV bo uv&wxyjz{*|qQῌA md+ 

tAHῌQHῌqt yjῌ A/

A bo b14E%&[Q+,  %

XXo exp  aῌq῍  
bo +exp aῌq !+**῍#$%& q '()* bo,"-*./ %&0%&

+

1"

*23* *.*-1 md+ *4/ q '

56789:*1 +*;<.*; =*> ?+,@A*4- " BCC +*;=E1FG a  *; * *.*/ '5/ H /;-IJ*4KL

1* "CC*MN5/ B* +*; D=*O   .*῍* * 5/ 2>~?A b

P3

1A/ "*4

.1/ " b  bo ruh*r}- B5EDh 5Lyj
YE$@/ CA
>~qrY3TqrEC1/B*" bo  b r A, rDb+,A/bbboQ+-  b ' }A/ n 2*῍*E* 5@51RA9: 1%&-0/*῍ * 0%&- /; *ESBDT

%&-4H@*4/TU+*;

r-4d£¤}- +330 DWn' .*< dE1/ CA'- *῍ 5"-¥ ¦§¨©'5"Eª1/ yj  *«¬ ,CATV9:WXYZ %

 *¡

+330 DWE 0*῍¢1r-4-  *῍ ¢/ %/; *FG *.**- *; * * 5 Q++/ /; *a*.***0 T}1/ 9:?n bo dEN.1' }6d BrN"  %&(H@*  bo  bn 1 1/ n bo 
boXoXῌXo !+**

}1*>e~3?A b  

Db?jk
/ "

 t n 0*῍nr-N.1/

N.5'}- ¦§¨©

5"-¥1/ ῌ­  *ῌ­ ®RR5b[-\?1/ NWX-4]^A +331  1 ¯°DW ¦§¨©5"-¥%-_N`a? / B*N

HbA/

WX-4bc%-%dE_NAeO b  bo  Bfg9:H@hA/ 2Z bi-j³´µ !1A Q+./k-

lm% *.*-1 md+ *Z dEH

5dN.1*789:*5HbA/ HnZo-N.1ei ,*῍

5

+,

 ±²0'*Bbῌbo  B '-2" ,<-  }6d ¶A-1YY·¸£¤4/ %

 *

bc

34

!» r 21 ¼ ,**+

ῌῌ+.
Fig. +.

*+BºbῌboChanges of the values of B during therice-growing periodno"#' e .pL#qrg%B%6 Z
V .fg"')hO   sZV[tuvwhO5 'O<xy

XYz{ vw|}~, ZV 6 x
x w%j 9%P.
.. VWXYz{ a"bcdkW

.A#<XYz{

"#  01 b a

L */ cmbcN"#6 x| }~!

VWXY01N&#6 XYz{N' +33+  01 a+33. 

]

 ,/

*.*+,

B *.*+,

&' - &' J' +330 

E5 +331 E#&']ῌῌ+-b  boFig. +-

w Db  *.*+,

6 6

N"6 +ij%E&'

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35ῌ%&³./Inﬂuence of plant and algae on nitrate
removal



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V  7
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Components of nitrogen

T-N

NO--N

NH.-N

NO,-N

Org.-N+34,+24. 33/405*4, 3*425*4**41 3-4/5

++40
+-4+
+,4/

+*43 33-435+,4+ 33,4,5+*43 3214/5*4- 3,435*4- 3,435*4- 3,425

*4*
*4*
*4+

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5 ῍01   21 ¼ 1,**+236

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a,G

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