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J. Jpn. Soc. Soil Phys.
3<ABC;
No. 22, p. -1῍.. ῎,**+῏
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E#ects of Opener-Type Subsoil Improvements with Amendment Matter on
Hardsetting Soils in the Kamikawa District of Hokkaido
Yoshio YOKOI*, Iwao KITAGAWA**, Eiji GOTOU*** and Hiroyuki TAMARU**** Hokkaido Pref. Kitami Agric. Exp. Stn, /, Aza Yayoi Kunneppu-cho
Hokkaido *33ῌ+.30, Japan** Hokkaido Pref. Central Agric. Exp. Stn, Kita +/ Higashi 0 Sen Naganuma-cho
Hokkaido *03ῌ+-3/, Japan*** Hokkaido Pref. Kamikawa Agric. Exp. Stn, / Minami + Sen Pippu-cho
Hokkaido *12ῌ+-31, Japan
Abstract
The e#ects of subsoil improvements were examined on hardsetting soils in Kamikawa,
Hokkaido. The soils were ﬁne-textured gray terrace soils. They are clayey, hard, and compacted and have a shallow soil layer.
For subsoil improvement, a new technique has been developed that makes use of soil amendments.

The technique is a modiﬁed method of subsoiling.

It requires the construction of trenches that are +*cm wide and ,/ῌ// cm deep at 0*ῌ+,* cmintervals. Soil amendments are put into the trench.

The e#ects of the subsoil improvements andthe construction standards for the trenches are as follows :+.

Three years after the subsoil was amended, soil hardness and bulk density decreased along

the trench, and air ﬁlled porosity was maintained at around *.+* m- m--.

Penetration resistancewas greater than ,../ MPa at a depth of ,/ cm before treatment ; however, it decreased to *.32 to+..1 MPa after the treatment.
,.

The amended parts of the ﬁeld worked as a supplementary underground drain in the uplandﬁeld and by the improvements agricultural machinery can be operated more e#ectively even after
rainfall.
-.

The subsoil improvements caused the root zone of crops to expand.

improved remarkably, and yields increased.

Nutrient absorption

The improvements were especially e#ective todeep-rooted crops which are susceptible to wet injury.
..

The trench intervals were set at 0* cm when soil hardness was greater than +.+0 MPa ;however, the intervals were expanded to +,* cm when the soil hardness was *./- to +.+0 MPa.
Key Words : subsoil improvement, hardsetting soils, soil hardness, bulk density.

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Outline for concept ional opener-type
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Table +*.1,.+.31 MPa Ust +.+0 MPaW%&+me

Physical and chemical properties of amendmentsg

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Soil hardness and saturated permeability of hardsetting soils.

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40

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Table ,

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Soil physical properties of hardsetting soils

`
~
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m- m#- : pF +42±C
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! *.*.*

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Physical properties of subsoils at - years after opener-type subsoil improvement£¤,# ¥ "# m m : pF +.2
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«¬­ 0* cm ij
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+4.32
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The improved soil proﬁle by openertype subsoil improvement.

h&/ +2* cm

ij! fg [(--)&! 0* cm
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

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42

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f yz 34K 7G `  !"#$%& '()*+,

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< TU 12V 128  (YZ[\ ]H^_K72 ; /*cm `TU

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y()*+,zRoot distribution in the soil of the experiment ﬁeld (Irish potato).

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43

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Crop yield in the ﬁeld experiment

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STUV 0* cm ()i 14.2 +-,8
STUV +,* cm ()i 0432 +,.8
STUV +2* cm ()i 04+1 +*38
WXY 0* cm ()i04,, ++*8
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*4*20
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.0431
.34*.
.24,1
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./4.1 +-+8.-431 +,18.+4.- ++38..4/- +,28.-4.3 +,/8-.4.3 +*+8+24+241
+243
+342
+243
+24-

1340, +,18
124.2 +,/8
1,4.0 ++08
1,43* ++08
1-4,. ++18
0.4*2 +*,8

*430/
+4*00
*431.
+4*,**430**430.

*43-* +,28*420- ++38*41/3 +*/8*431/ +-/8*4112 +*18*42.. ++38

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-.401 +**8+140

0,402 +**8+4*0,*41,. +**8/40/ +**8

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Table 1h

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i

STUV 0* cm ()i
STUV +,* cm ()i
STUV +2* cm ()i
WXY 0* cm ()i
WXY +,* cm ()i
WXY +2* cm ()i
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The management evaluation of openertype subsoil improvement

nopTq

Table 2&'

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.53+-52,2
250+,
/5+.2
-5322

+-15+10 +/,8+--52,+ +.+8+,+5+00 +-.8+-*5320 +./8+-+5-23 +.08
3251-2 ++*8

WXY2Zῌ=%῍ [ \ ]^_`3

¬

3*5*/1 +**8

 M \a bcd ef

= +8
= ,8

­3=%w5 '0Sª< >E®¯ °?®5®<@±+33+8²= -8 &'<0 A0B rGC³´
+33-8 +/ BM=%= .8 &'<0 V<2¥µ= /8 ¶·¤ª<¤&'<03=%

1 5*! ¸ ῌD - M E0E ­318
Y¹F#ῌº0WX0,8
XGq9» MPa8 +4+0 4g&'()*4/- 4g +4+0 34

0* cm () +,* cm ()-8 O#PQR7%STUV:

.8

4g



&'()

*AhiMjMN

 $%STUViM A
/8 &'() * +, = 







 k  &'() *A jMN/ῌ ῍ ΐ ῒ ῏lm nopTq r - 1       

: E!1 "# =#s K7O# % tF u v "w#$bA#%x2!"#  $%&'() * +, &'y1() 2*+ !Lz

{|3,}R7

.ῌ ῐ ῎ ῑkuM -#abA#2~&y&'.2/ 2 

- ./01  02

MPQR7῍ ZῌV STUVNA W

345 $3"67XY8+8 -  19 :;O# 0* cm =<

5=  >?0 "67%

,8 @=:A- ./01 BC '=:A

20A 

+,* cm19

&'()2 1bv 23=O% +2* cm ()  

0



19

*./-

 DEF GHI JK L

MPa 4g3= +.+0 MPa 34MN7 +,* cm ()M&

MN'= +.+0 MPa 4gMN7 0* cm ()3

VWQ U » 22 ¼ M,**+N

44





    !"#$ %&' ()*ῌ+,-.

/01234567 ()892:;<=<3>?67@ABC῍
DEFV MNb Vd /, : ,--ῌ,-3b

 jk Vstbῌx ῌ 5 ῌ 

ῌ3GHIῌJKL M+332N : ()OHP

V`ab Vcd 03 : 0..ῌ0.2b

ῌ

¡¢{ M+300N :£¤¥¦01Q§¨ῌ©ª«¬~­U®¯°b "±²¯°³´ . : -/b
VWcµe()¶< M+321N : ()

()Ve M+33-N : fghijkl
mnopb pp. -10ῌ-11 qb
()r< M+330N : Vstjk&u : -1ῌ-2b
ῌ5vwxῌyz{ῌ>?

: 3ῌ+2b ῌ  M+32.N : QVW MQ 2N
t M+32.Nb VPtijkj

QR STUVWXYZ[\ ]^ Q_

DEF

VWX|}Vt~Qb V +*- M+33/N : R

VWc : +0-ῌ+1*b·¸¹º : ,*** ¹ +* º ,/ ·¹º : ,**+ ¹ 0 º 0 