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Characteristics of the humic substances in sugarcane cultivated soils of
Minami daito and Kita daito islands in Japan.
INTRODUCTION
●Sugarcane yields in Minami daito and Kita daito islands in
Japan showed a declining tendency in recent years.
10
Minami daito island
Kita daito island
Yields(t/10a)
8
●The cause of the decline in sugarcane yields may be low
content of humic substances.
6
4
●A study was conducted to examine the characteristics of the
humic substances, which are being considered of having close
relationship with the properties of sugarcane cultivated soils.
2
0
1995
1997
1999
(Year)
2001
2003
Yields of sugarcane in Minami and Kita
daito islands, Japan.
Sampling sites
Methods
131°20′N
K-6
K-7
K-5
K-4
K-3
K-8
K-1
<Kita daito island>
K-2 K-9
●Soil chemical and mineralogical
properties were determined.
●Humic substances were extracted
and quantified according to the method
described by Kumada (1977).
<Kumada method>
M-11
M-14
Soil sample
M-8
M-12
M-9
<Minami daito island>
M-7
25°50′E
M-10
M-4
M-6
0.1M NaOH+
0.1M Na4P2O7
Supernatant
0.1M H2SO4
M-1
M-13
M-3
M-2
M-5
0
5km
●Sugarcane cultivated soils
in two islands is classified
into calcareous soil.
●Sugarcane cultivated soils
were collected from 9 fields in
Kita daito island and 14 fields in
Minami daito island, respectively.
Precipitation
(insoluble fraction
; humin)
●Collected surface soils
were utilized characterize the
humic substances.
Humic acid
(precipitation)
Fulvic acid
(Supernatant)
*Humic acid, fulvic acid and humin were
determined by back titration using the potassium
permanganate solution.
*The degree of humification was determined by
calculating ΔlogK(logK400nm-logK600nm) and
RF({K600nm×1,000} / {0.1N KMnO4
consumption(mL) / 30mL of humic acid solution)
●Kazutoshi Kinjo1, Koichi Yoshida2, Yoshihiro Tokashiki1, Makoto Kitou1, Yasushi Gima3, Shigeru
Kameya3 and Naoko Miyamaru3
1). Faculty of Agriculture, University of the Ryukyus,Okinawa, Japan, 2). Okinawa Agricultural
Technology & Dvelopment Office, 3). Okinawa Prefectural Agricultural Research Center
Results & Discussions
⇒Soil pH and EC of the soils from both islands were in the range of about 4.0-8.0 and 0.08-0.36 S/cm,
respectively. The results of XRD indicated that kaolinite and illite were the most predominant mineral
in all soils. Soil texture was almost heavy clay in all soils.
<Humification of humic acids of sugarcane surface soils>
⇒The degree of
humification of
humic acids in
sugaracane soils
showed a low
degree(Rp type).
160
120
A
3.0
⇒The
percentage of
humin, fulvic
acids and
humic acids
contents in
Total humic
substances
were 42%, 37%
and 20%,
respectively.
Content of humic and fulvic
acids and humin (g/kg)
2.0
RF
80
B
40
P
Rp
0
1.1
0.9
0.7
⊿log K
0.5
⇒The low degree of
humification is
classified into
1.0
degradationresistant categories
of which the
materials are lignin,
0.0
tannin and
melanoiding.
Humic acid
(HA)
Fulvic acid (FA)
Humin
Significant correlation coeficients (Kita daito and Minami daito islands,n=23, **1%, *5%)
pH(H2O)
pH(KCl)
EC
HA
FA
Humin
⊿logK
Na
K
Ca
Fine sand
Ca
Mg
Coarse
sand
0.471*
0.837**
0.693**
0.421*
-0.410*
0.471*
0.854**
0.651**
0.424*
-0.414*
pH(KCl)
Humin
0.994**
T-HS
Na
Fine
sand
Silt
Clay
0.590**
0.524**
0.419* -0.601**
0.619**
-0.483*
0.626**
-0.406*
0.429*
-0.575**
0.458*
-0.568**
0.514*
0.761**
-0.445*
-0.515*
●Soil organic matter(humin) accumulation in the sugarcane soils has been enhanced by the presence of
exchangeable calcium.
●It was suggested that liming materials, which are having high concentrations of calcium, can be
effectively utilized to enhance the soil organic matter(humin) accumulation to improve the soil properties.