
J. Jpn. Soc. Soil Phys.
B¼C59No. 33, p. +- ,* ,**/



*ῌ*ῌ*ῌ*Model Analysis for Reduction of E%uent Load from Cultivated Lands
Eisaku SHIRATANI*, Ikuo YOSHINAGA*, Tadayoshi HITOMI* and Asa MIURA** National Institute for Rural Engineering, Tsukuba Science City -*/ῌ20*3, Japan
Abstract
We developed a numerical model to simulate N ﬂow in an agricultural paddy ﬁeld and uplandﬁeld area and analysed scenarios for recycling the agricultural runo#, including ﬁeld drainage,from an agricultural area with an irrigation/drainage system.

In it, we considered N removal inpaddy ﬁelds, a regulating reservoir, and canals. The results of analysis indicated that a large
amount of the e%uent load occurred during the transplanting period and just after fertilisation,and that recycling could reduce the e%uent N load. In the case where paddy ﬁelds occupied thearea, the e%uent N load would be equal to the inﬂowing N load (net zero e%uent) at a .2῍recycling rate.

However, in the case where upland ﬁelds (--῍) and paddy ﬁelds (01῍) occupied,3/῍ recycling rate was needed to achieve the net zero e%uent.

To implement the knowledge forreduction of e%uent load from an agricultural area, we should solve the matter that the water
environment deteriorates as pollutants accumulate with intensive recycling of runo#.
Key words : nitrogen, recycling irrigation, sustainable agriculture, paddy ﬁeld, upland ﬁeld/ '; 4Takeda et al., +331 ; Takeda and+     %&' Fukushima, ,**. ; Feng et al., ,**.51 L L ` !" ῌ# $0ST#WafL {|#y a}1 o/~&';G;1  ()*+,-./01Q"RST 2%&'3tg+GST 4`-/$23 4+3335  6789:; 2<1 L L !" ῌ# ῌG #G$

=>? 4@ ++ A ++* B5C &DEFG; DEHI 4@ ++  +* J ,, $*ST %&'6`

23A 03 B5 KL MND .OP D

7/01 `s 0F!"!Q"RST789:; 2<U

ῌ# Wa*fE; 8+,v@VW#GST$1$5%&'w.9`%&'y1 g+GST

X/ ()*STL' :%&YL';`-.#/01Z['\]^(  $_$)/ ῌ`/ :¡/ $)ῌ¢'\£¤¥+`%&' aL''\ b*¦§L `¥+d L $!" ῌcd L'\efg+9-hij ,k'

% a +,¨;' ©ª#Gs; 4l) +332 ; mn ,**.51 o !" ῌ/-«5;P/9`%¬pqrs =L¯>°1 '\tuvw-x.G`-yz%&'* 4?5 ±²hiN$±@ ³-*/ῌ20*3 ´µ¶¨·¸¹º» ,ῌ+ῌ0 : '\ !" A 78#  $) (.­<®

¸¹ "º » 33 ¼ s,**/t

14, ῌdNpaddya Npaddy
dth,+      Fig. +  +  +** ha!

. "#$%&'ῌ()*+[["

Npaddy!

+

bc~ smg L+th!

p smt aN ~ sm d+t "L%,ῌ uv^_%bc  *,  -./0123   - 4567

689: ;, &'ῌ< - XU i  ! x bc~- i-+  ~12="4%,>?

F H@ABCDEF %G%, F H IJ- KL% -()12  MQ+  689t %

RSTῌ

NOPD=U%:V=,

Npaddy, i

WXU F H : Y9Z%[=XU&'
ῌ\%-]Z%[= "9%,&'ῌ "- ( F H^_>?`a% ῌbcdefg%L%,ῌ!

 [["  
wi Nirrigation, iRi Nrain, iLiῌ+***hi,Nirrigation ^_ Nrainῌ ^_uv bc~smg L+t Lskg m,t s

smmt

dhi-j  kl%, i ^_ i+ - i ^_ i+  >?  ,"- j-mnUo%! pq$

smmt wῌ

N ~-  Fg12@G%[= "% k<r =*+ > <i

9 *.*+*.*- m d+f sShiratani et al., ,**.t, uv+

bN

 ! p f Fig. , , / wxy^_ 1wzyY: uv L ]Z%[={1%,, ! x bc~ f-bc|}N +N s+ t "[= "9% sTabuchi, ,**+ ;Yoshinaga, ,**-t,"-¦"Q§D¨D ©ªῌ«u^_n"¬­ n ®{ ¯o°=% sShiratani et al., ,**.t,
Tabuchi s,**+t~-!῍+²³´%G!µ g12@G - "¶,a+.+·+*/sTpaddy,1-t,*.**/[[" Tpaddy!

Fig. +L ! "-¡"L¢Z s*.*+ m d+ £~t ¤¥± N! bcN- ! x bc|}=*

smmt " ² sKt "L%,()Model paddy ﬁeld irrigation system used in analysis.

-r s@tuvw : x Oyz{|"#$]}

ῌ ῍

15BB-CTank +BTank - DEF0GHIJK S+ Fig. - LS , /0 r - C'J

MNOPF/0PQ!"#$%&'(R S, /0 r+CTank , S Tank - TPF) *Shiratani et al., ,**-+, -. Tank +, Tank , /0

/0PQR r,CTank + S Tank , QR r.

Tank - 123456789 :6789

CTank - UV

/0;<=>?@, A) X+BX- 0 B+ῌ῍,Fig. ,MNOPQRWX,  U V N O   Y Z  [ \ ]^_`YZ

abcd *ef+ Sghij)d *kf+ lmnopq

Target depth (solid lines) and calculated depth (dotted lines) with actual rainfall of ponding
water in paddy ﬁeld.

ῌ῍Fig. -lm

!"#$Tank model to calculate drainages from upland ﬁeld.

ª« Q¬? ­ 33 ® ,**/

16

NOx-N 

m3+ NN2 Fig. .

  +330    !"
#.$ %& + '%() *+,-."

NOx-N 6 kg m3, Q2

rs t ! u"v\w4]pM jxxyzt {b|}~!%\4]

Arrhenius /01pM

ῑEaῌT3T῕ΐN
ῒ῔RTT῕ῌ ῍ ῑ#.$V2k῕exp

TXY=

44 V2 5, kg m3, d3+ N2
d3+ Ea2<=: >?@AB J mol3+ R2C

       *, 'JFKLM

RS5," #/$ % TUDVWXYZ[^_?".

`6;ab]cEP2

Sij PQ=῍ b t῏῎ H ῐ#1$44 N canal  N canal, * 2 k
3+

mg L  b2nf



f

o,3+

5,EF m d  t2

o, " n¡¢]£¤nf o,¥ + '%01 i3+ ¦ §¨gh6 kg m3, pe2

gh6 kg m3, kl" mnf

o,p'% i ¦ §w
Nreservoir, i2 

NOx-N 6;ab]cE #0$ %0 k l 5 , kg m3, d3+ e 2 E Fῌ῎.
Fig. .

H    
#0$

L2eNN Q

4 4  L 2

 o , " #1$ %῍ ῐ῎῏#/$

RS5, kg m3, d3+ l2;de5, d3+ p2PQfxkjx d H2 m dp
῍ p ῏2lp +3
῎ peῐdt44 P2PQ

ManningNcanal2Ncanal, * exp 3

 N ῌO +33*
\" NH.-N ] NOX-N

6

Streeter-Phelps %7M

DEF JK3+ mol3+ T2G+ K T῕ : 278+,
K  HG G+" I+mn" *k5%\jx\G6 kg m3, k῕2 78+,9:;5,PQ

mnq m d3+ ©

qin, i Ncanal, i©Ai Ri Nrain, iVi

Conceptual model of nitrogen cycle in upland ﬁeld.

#2$ : /019z{()*<=

ῌ+Table +()*<=Vc-.

Calculating conditions for the analysis

Variables

Conditions

Depth of regulating reservoir+4* m

RainfallEastern coast of Lake Biwa in +33/

N concentration of river waterand precipitation

River water : +4* mg L+
Rainfall : *42 mg L+N removal rate in paddy ﬁelds
and wetlands

Paddy ﬁelds : *4*,/ m d+Regulating reservoir : *4*,/ m d+Clay bottomed canal : *4*+ m d+

Fertilizer in paddy ﬁelds

Basal dressing at transplanting : .*4* kg ha+Topdressing : ,*.* kg ha+ in mid-June ;-/4* kg ha+ in mid-July

ῌ/173YVWZ

Fig. / Required water ﬂow in irrigation canals.

 Nreservoir

mg L+ Vῌ0 m  A m, g-  m d+ qin  qout

  m- !"#,,  ῌ
Figure + z

Relationship of inﬂowing N load andoutﬂowing N load of the paddy ﬁelds
area to the recycling rate.

$%&'()*+,

Table + -./01$%2345067819Fig. 0$%k῍4No"?0Zj{Z9z{:;&<=,>#

L+ 5,># w> x@ ,/y ^5,>#Figure 0 N$%k῍45/0ABCDZjz{?3@ ABCDEῌFῌ?GHI 0 JK

Z9z{:;&|o# $%k῍3deLMNOPQR"STU3VW5,XYZ&&}F~o"5$%k῍4&"5IF /Fig. / 5[\],># 1Y@ ^_`U1VW01$%23NS78IU~NabF]VZ&c,de&f,>#U"> qr78/0Zjz{o"# /01@ gNhFI!"i\N /078Z9Z9z{Ij, k῍N@&lm`N$%n3

,># & +.* m & 2.3 ha 5],o"55,># p< qr78sd @>N$%k῍4I .2῍ 5U\ Z9z{&Qt"5IF"# uvqr

B5o"5IF># Table , N ? Y@ + mg9º:5 » 33 ¼ 1,**/4

18

ῌ,Table ,¹7UYZ8

1+.2 V4

N balances in paddy ﬁelds5 regulating reservoirs and canals during an irrigation period of +.2days
Inﬂowing N(kg)Outﬂowing N(kg)

Removed N(kg)N removal rate
per unit area(g ha2+ d2+)++5.+14,35*/34*+35+034,

25,..412510/42+35+.-42-5+1-4/,3-4,,/4.

/-40,,,40++.4.

Paddy ﬁelds (.** ha)
Regulating reservoir (243 ha)
Drainage Canals (+4/ ha)mg L2+ _`AB abcde(bM"R&f 3 ghJRij
LkMl m@*noK+ pKq NOῌ(^r sM!"n+-    
<tNOῌ<?C uv

wx #Bῌyz{| ^rsQ}~yz{$&+  + mg L2+

AB <t(NOῌ .2῍ _S<t"]L(MR&+& % --῍<+-* kgῌha 3K< NO@AB( L 6 @& ( 3*῍ _SNO MR&+ ! N
ῌ1NOῌ@ & <=YZ

Fig. 1

Relationship of inﬂowing N load andoutﬂowing N load of the paddy ﬁelds
and upland ﬁelds area to the recycling
ratio.

Oῌ*<%(XM'& MNOῌ' |(]"
MR&+^( ῌM)br l*O +:;
 1, ,**,4+ NOῌJRr=@ @ - ^<O @n+ !"

#$%&'( )*+,- ῌ
<=:> ῌ ?@ABC*. 
&+
< --῍ <DEFGHAB( Fig. 1I@JK LM@( 3/῍ NO KPQ MR&+^¡.¢^A!;_M+ £¤ῌ¥¦K§ /¨MH  &*n& .mPQ(©*0ª1'M]MAB*«,-. / ,** ha  0 1+-* kg ha2+ 3 4 5678 9:;^H  & lQ.m( & NOῌ

+ pPQ  =¬­G®¯78 °M ±2JR²³´3M:;+JKM²³µ¶4,·5yz{Q&@6¸(+   Feng, Y.W., Yoshinaga, I., Shiratani, E., Hitomi, T. andHasebe, H. (,**.) : Characteristics and Behavior*ST NO 3/῍ AB(of Nutrients in a Paddy Field Area EquippedῌUVW( ,.0 mg L2+with a Recycling Irrigation System. AgriculturalMR&+ X

1,***4 YZ[\] 1+32,4 ( ^( -Water Management 02 : .1ῌ0*.

³´µ¶· : "(¸ª ¹º»®¯!¼ +33* : ῌ

ῌ   !"#
$ .. : +῍3-.
3 " 4$ 00 +, : +3῍,-.
5678ῌ9:;<ῌ=&>8ῌ

AnalysisforReductionofE%uent Load from Agricultural Area by Recycling the Run-o# Water. Water Science and Tech-&?

,**. : ()*+ -.@ABCDEF(/GH "IJKLMLNO M PQ$ pp. .+῍.,.
6RSTῌ5UVῌW,**-, Dublin, Ireland : .-῍.2.
Shiratani, E., Yoshinaga, I., Feng, Y. and Hasebe, H.
(,**.) : Scenario%&' +332 : ()*+,-./01219nology, .3 (-) : //῍0,.
Tabuchi, T. (,**+) : Nitrate removal in the ﬂooded
paddy ﬁeld, Proc. of an International Workshop onXῌ5YZ[ +32, : E$ciency of Puriﬁcation Processes in Riparian\]D^  _!"`#$ ,- :Bu#er Zones, Organizing Committee for Interna-2-῍23.

tional Workshop of Riparian Bu#er Zones (ed.),abcd ,**, : "e(/fghiῌjk " 4$ 1* 3 : 133῍2*,.
"lm +333 : inop"etk

November /3, ,**+, Kushiro, Japan : 2+῍3*.
Takeda, I., Fukushima, A. and Tanaka, R. (+331) :lqrs

Non-point pollutant reduction in a paddy-ﬁelduvwx y ++ z +* { ,,watershed using a circular irrigation system.

"lm| 03 }

Water Research, -+ (++) : ,02/῍,03,.

~ῌ +33* : ^

Takeda, I. and Fukushima, A. (,**.) : Phosphorus pu-N riﬁcation in a paddy ﬁeld watershed using aJKyῌ  lN$ . : -῍circular irrigation system and the role of iron
+3.

compounds. Water Research, -2 (+3) : .*0/῍.*1..

^ῌ Z¡ῌ¢£¤¢¡ῌ¥¦'Z +330 :Yoshinaga, I., Feng, Y.W., Hitomi, T., Shiratani, E. and§^¨©@Aª«¬­®¯°O "Hasebe, H. (,**-) : Nitrogen removal function ofe LMQ$ +2+ : +*1῍++-.
Shiratani, E., Yoshinaga, I. and Singh, R.K. (,**-) :a paddy ﬁeld in a circular irrigation system, Proc.
of the 1th International Conference on Di#use Pollu-

Model Analysis for Nitrogen E%uent fromtion & Basin Management, . August +1῍,,, ,**-,

Upland Field Constructed with Under-drain.

Dublin, Ireland : .-῍.2.

Proc. of the 1th International Conference on Di#use
Pollution & Basin Management, ., August +1῍,,,±²z{ : ,**. z ++ { -* ±z{ : ,**/ z + { +3 op=`  33 º »,**/¼

20LM῍^ 1*῍ b<c#Pd')e75"EDf" )e" Qy=6^)e"mg"4i m4"   :

Qy=Z7

M῍TC)e iDQy=CD65 C 4 ^h)C% SD S)<L7'" | DUvD^}"7^ LM

῍" JD6ZQy=^S9TC=>6 :!"

#$%&' TD^5_  Qy=^S9T X (ῌ)*+,-./012"3456LM῍<jk 3E6C " | DU75

+,"7"Z COD lm" +/,* ppm, TOC lm" 12 ppm

89:4;<=>?@: ?@:AQy=^S9D6g~ z{RZQy=C% S9D

BCD63E6 ?@:A FGHCI6 # 3J KD?@: L< => ?@; :M῍N<>6 OPQCR<ST#nop qD=l"7^ SD6r UV  'W4 !<XFT#Z7CJ s);)l<=>"7_"I <#YT

n 6Z-.mT/0^7"4LM῍$ Z %[\]I^7 )'&Z7_ '(& )`&Z7 '( +,*a)`b+,*4D"A?@:<+<,D?@:^-./0 4^ :s`)'=lt!<mT#  ILCn"u=988^vwTCJ!;?@:<T BC ' s`)'^61KD64 c2d3e4f5C n 6ZJ/0`^7 Cx2D6g6 )'C67 89 ῌN^'('<g~ Ou3E6 DD IL<:CD: h;^Ji <D?@:j k D6?@:o~Zm4?@:</0^7 C'<:CD)LMῌ=lLM?@:CD6FG<HD &mn ^S>oJy4?@:¡¢X3£zT¤zi44 n<:CD?@:A ¥RN{i4 Fp-./012V?q@"7 , A

E6rstu"7

ABCD "#ῌ$%&'(#)*+,-.

 ! "#ῌ$%&'(#)*+,-.

/010#23456789:; :/010#23456789:; :6?@:<K|^ ¦8?@:"opBCvD<3 EFG"HI<JKD IL§})C )e~)oJ4$)7m<MwTCJN^7E^ vDO<]DEX ¨ZCD6FCJ^ op))FG<xPS>"4  ; Qy=a

7i"h4Z"7 ©ª)3«z{R^S9T^&C CN^ TD"4i>^©) ¬"Ji­& E6| DU<} _ ¦8?@:<>_SOX C5®@ 67~&44"4]D^ZTPQC^"«CJ^ )l<!TY <¯D6SD6CJ CZz0NCJ :6ND64^ KD?@:"V"7 WD XYO 6° ::"356 Z[vDC: \4]

?@:" SO±u"7 ¦8?

()`^K#M_&]:C4P@:²?@:"7~ ¦8CD6F6Qa P`DUPQ6 KD?@:Y| f>XY^Y X C

"S>oJ 4E64 r S>~J_z4 > ³´oJ  XY4PQ<S>oJ ?@:<aDC"µ«6¶·.¸¹<o~X ?@:|T/0=>6^7CJ