The Technique for Improving Soil Physical Characteristics by Preventing the Formation of Soil Crust by Dressing the Sandy Pyroclastic Deposits

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1 J. Jpn. Soc. Soil Phys. No. +*-, p.-+,,**0 * The Technique for Improving Soil Physical Characteristics by Preventing the Formation of Soil Crust by Dressing the Sandy Pyroclastic Deposits Yoshio YOKOI* * Hokkaido College of Agriculture, Nishi-senbiri-,/+, honbetu, nakagawa-gun *23-01/, Japan Abstract E#ects of dressing pyroclastic deposits to the crust forming soils distributing in Biei hill area are summarized as follows. +) Crust forming soils in Biei hill area shows di$culty in plowing, which becomes the limiting factor for the crop production. This soil is not clayey, but easily dispersed after rain fall, and readily forms crust on drying. This crust forming soil has remarkably large solid percentage, high bulk density, and low coarse porosity. The soil hardness also increases remarkably on drying.,) Pyroclastic deposits improves these soil physical properties, and the yield of field crops increase steadily by dressing the pyroclastic deposits to the thickness of /+* cm. Larger dressing of pyroclastic deposit showed little e#ect on the yield of field crops due to the decrease of soil fertility. -) Soil dressing decreased the specific resistance on traction when field is plowed. Soil dressing of /+* cm thickness was e#ective enough to the decrease the specific resistance to the lowest value..) Critical thresholds of the necessity of soil dressing for improving the physical properties of soils were evaluated. These values were (+) siltclay contents*.-/ kg kg +,(,) Crust hardness *.2 MPa, (-) bulk density+.-/ Mg m -. When either one of the three criteria is applicable, it is judged that soil dressing is necessary. The goal value of the improving soil texture was set at *.-/ kg kg +. Key words : crust, pyroclastic deposits, soil dressing, hill area +,** CLLiC +303 * *23-01/,/ + * : *1.+, :

2 4 +*-,**0 Tanaka et al, +33,, +33/, +331 a;+331 b; /* ,,+ + *.+ L *-.+ kpa kpa 32.+ kpa +32- *.32 Nmm ph H,O CEC Truog *.+ N +320,, +32-, / cm, +* cm, cm -* cm / ** m, - -+ *.,3*.0. kg kg + *.+2*.-1 kg kg +

3 : 5 Fig Distribution of pyroclastic deposits covering the Biei hill area in the middle-south part of Kamikawa district (mapped according to Ikeda and Mukaiyama, +32-). SCLLiC *.1. kg kg + *.+2 kg kg *./* kg kg + / mm *./*,*.0/* kg kg ,*** Asgedom and Hasegawa,**/ Casagrande *./+ *.0, m - m - *.*/*.+.

4 6 +*-,**0 m - m - +.,2+.0- Mg m - + ph /./ CEC +* cmol kg + /**1** *.+ N,** , Table + kg kg + *4,* *4 *4*/ The moisture content of large soil clod and the soil hardness after plowing up. MPa ,.34* mm,. -,.* *.3* kg kg + *.*/ kg kg + LS +.+ Mg m - ph /0 CEC. cmol kg /* , --+, *.,-+ kg kg + +* cm *.. kg kg + *.+33 kg kg + +* cm *.*3, kg kg + CL SL +.0- Mg m - *.0,. m - m - / cm *.//1 m - m - cm *../2 m - m - *.*// m - m - / cm

5 : 7 Table,, E#ect of dressing pyroclastic deposits to the crust forming soils on the physical properties of soils. kg kg + cm m - m - m - m - m - m - m - m - Mg m - kg kg + MPa * / +* *4/1* *40., *41/. *42*3 *4,-+ *4+2+ *4. *4++1 *4+33 *4+11 *4*3, *4*1. * / +* *4-2+ *4.., *4/*/ *4/0. *4--+ *4,2, *4,/2 *4,,* *4,23 *4,10 *4,-1 *4,+1 a *422* *4*10 *4*./ b *4223 *4*0, *4*.2 CL SCL SL SL LiC LiC CL CL LS LS *40,. *4//1 *4/+3 *4./2 *4/*/ *4.,0 *4.,3 *4-30 *4+-1 *4,1, *4-** *4-// *4*,/ *4*1, *4+ *4+2, *4*/3 *4*0* *4*11 *4*2+ *4,30 *4,32 *4,,2 *4+2/ *4,33 *4,., *4+3. * ,2 +4,* +4,, * a b, *0., kpa, 0.,32.+ kpa, 32.+ kpa *40/* *4/*, *4/0 *4-/ , *421 *4.2 Table - - E#ect of dressing pyroclastic deposits to the crust forming soils on the chemical properties of soils. ph CEC cg kg + cm H,O cmolkg + CaO K,O MgO mg P,O / kg + * / +* * / +* a b / /43 /43 /4, / , * +*+ 0, /+ 2 +,+ ++* 13 /3 +.* 1, 0+ -, 1*.0.* -/ +-,.,2,0 +2 -, -*,, +,,* +2,* ,1 +, 1,. /**.2* -2*,3* 03* 02* /.*.+* +2* ++* *.+ N mg kg + mg kg + +4-/ +4-* +4,/ +4,* +4+, +4*/ *42, *41+ *4,3 *4/3,4.,4,, *4*// *4*1- *4+-2 *4+1/ ,2 +4*, /4, /4- /4- /4,,4,,4* +4/ +4- *40 +4* *.*1- m - m - cm *.+1/ m - m - +.,2 Mg m - *./*/ m - m - / cm *..,0 m - m - cm *.-30 m - m - *.+-1 m - m - / cm *.,1, m - m - cm *.-// m - m -

6 8 +*-,**0 3.. MPa +* cm *.0 MPa..+ MPa +* cm *.3 MPa, - CEC ph +* cm Fig.,, The relationship between the amount of dressed soil and the hardness of soil crust.,**. --, +2 / cm 1* +* cm 2*,**/ 3, / cm +* cm *.2 MPa mm,./ Mg ha + / cm -.+ Mg ha +,. cm / cm +* cm +* cm,.20 Mg ha +,2 cm / cm +* cm -0.2 Mg ha + 1. / cm./.* Mg ha + 2* +,.+ Mg ha + +* cm -- Mg ha + +* cm / cm cm * kpa / cm

7 : 9 Table.. E#ect of dressing pyroclastic deposits to the crust forming soils on the yields of field crops. Mg ha + cm / *,4.2 +** +,4+ +**,4,. +** **,24+ +** +*4* +** +2 / ,/,142,*-,4/3 ++0./4* ++3 -, *4/ +*/ 1* +*,4/. +*, --4-,1/,420 +, */,241 +*, ,, /,11,4.. +*3 -/4/ 3. -,4/ * cm +** - Fig. - Relationship between the amount of dressed soil and the specific resistance of traction. Fig... Change in contents of silt clay in proportion to the amount of dressed soil..* kpa, +* cm / cm. -/ -*0* Mg m cm +323 /+* cm, cm * cm,**+ +323

8 10 +*-,**0 / Table / Critical physical properties of soils indicating the necessity for the dressing of pyroclastic deposits. kg kg + MPa Mg m - *4-/ *42 +4-/ +32*. /+* cm / +* cm. /+* cm 1./ cm *.-/ kg kg + *.2 MPa mm +.-/ Mg m -,**. +.-/ Mg m - / / +, /+* cm - /+* cm. *.-/ kg kg + *.2 MPa +.-/ Mg m : pp.,.3,0-. Asgedom, G.G. and Hasegawa, S. (,**/) : The e#ect of raindrop impact and initial soil conditions on surface crust. J. Jpn. Soc. Soil Phys., +** : 0/1/ : pp. +*1++, : +. :.3 3/. Casagrande, A. (+3.2) : Classification and Identific-

9 : 11 ation of Soils. Trans. ASCE, ++-, pp.3* /* : +1 : +03+1, : pp. +3+,*/ +32* :., : --.*.,**+ : :pp.-. -/ : 23 - : +0-+1, : * : : pp. 0,2, pp. +,-+, : pp.,.,/,**. : ao pp : 2 /, :,--, : + +- : 1*2/ : 1* : //0/.,*** : 1+ - : Tanaka, U., Yokoi, Y. and Kyuma, K. (+33,) :Morphological characteristics of soil surface crusts formed under simulated rainfall. Soil Sci. Plant. Nutr., -2 (.) :0//00.. Tanaka, U., Wada, T., Yokoi, Y. and Kyuma, K. (+33/) : Evaluation of crusting susceptibility of some Japanese soils based on water permeability and morphology of crusts. Soil Sci.Plant Nutr.,.+ :,0-,1.. Tanaka, U., Yokoi, Y., Kyuma, K. and Kosaki, T. (+331 a) : Mechanisms and processes of crust formation : I. E#ect of initial moisture conditions on aggregate stability and crusting. ibid.,.- : 33 +*1. Tanaka, U., Yokoi, Y., Kyuma, K. and Kosaki, T. (+331b) : Mechanisms and processes of crust formation : II. E#ect of slaking and impact of raindrops on crusting under di#erent moisture conditions. ibid.,.- : +*3+. Tanaka, U., Yokoi, Y., Kosaki, T. and Kyuma, K. (+333) : Mechanisms and processes of crust formation : III. Relations between natural rainfall characteristics and degree of crusting. ibid.,./ : /-1/ :.0 - : +1, : 03 0 : ,**+ :./, : +*/+++.,**. : 20 : /10-.,**/ : p CLLiC

10 12 +*-,**0 /+* cm *.-/ kg kg + * 2 MPa +.-/ Mg m - :,**/ 3 +. :,**0, -

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