ῐJ. Jpn. Soc. Soil Phys.
ῑ῏῎ῒΐῐ
No. 21, p. -1ῌ./ ῍,**+῎Land Characteristics and Soil Erosion in Relation to Slope
Farming in the Highlands of Candikuning, Bali, Indonesia
Hajime NARIOKA*, I.W. Sandi ADNYANA**, Mastur*** and Simplicio M. MEDINA***** Faculty of Environmental Science and Technology, Okayama University, -ῌ+ῌ+ Tsushima-naka,
Okayama 1**ῌ2/-*, Japan** Faculty of Agriculture, Udayana University, Jl. PB. Sudiman, Denpasar, Bali 2*,-,, Indonesia*** Watershed Management Technology Center, Jl. Jend. A. Yani-Pabelan, P.O. Box ,3/, Solo/1+*,,
Central Java, Indonesia**** Farming Systems and Soil Resources Institute, College of Agriculture, University of the Philippines
Los Banõs, College, Laguna .*-+, Philippines
Abstract
Many environmental problems, such as soil erosion, a#ect upland and hillyland agriculturalsystems. In a study conducted in Candikuning village, Bali, Indonesia, biophysical characteristics
and soil erosion were determined in relation to slope farming.
The area is dominated by forests and vegetables dry land with slopes ranging from moderate tosteep. Soils in the area have medium to high fertility levels and the major soil types are Andosolsand Regosols.
Erosion was found to occur slightly in the forestland but was more severe in the dry and shrub
lands especially in areas with slope more than +/ῌ.

As such, appropriate soil and water

conservation measures are needed to achieve sustainable farming systems in these areas.
Key words : soil erosion, slope farming, highland, Bali, Indonesia

Introduction
According to the Bali Local Government(+33/), population growth rate in the island isquite high during the last twenty years.
Coupled with a limited area for cultivation offood crops, the need to produce more food tomeet the demands of an increasing population
has become highly imperative.
Faced with this reality, farmers are forced tocultivate even the sloping lands, which areoftentimes unsuitable for annual crops. The
intensive nature of annual crop cultivation inslope lands can cause soil erosion. Without
appropriate soil conservation measures, soil
productivity will decrease and erosion materials from upslope can accumulate in the lowlying areas as sediments. As a result, land andwater resources will be degraded.
This study was conducted in order to generate basic data related to land characteristics
and degree of soil erosion in sloping farmlands.
The ﬁndings of this study can also be used asimportant information or input to future research activities.
Materials and Methods
The research was conducted in Candikuning
village, district of Tabanan, Bali, Indonesia
which had an elevation between +,,** m to,,+** m above sea level and having coordinates
2ῌ+.῍-*῍S to 2ῌ+2῍-*῍S latitude and ++/ῌ1῍-/῍Eto ++/ῌ++῍-*῍E longitude.
Landform units
found in the village are cauldron valleys in thenorthern and northwestern parts, which areundulating to rolling, and volcanic ridge in the῏38Fig. +21,**+

Land unit map of Candikuning, Tabanan, Bali, Indonesia

south and western parts where the topography
is hilly to mountainous. The soil types are
Gray Brown Andosols whose parent material isintermediary volcanic ash and Gray Regosols
which have intermediary tu# volcanic ash as
parent material.
Primary data on climatic characteristics,
land use, soil characteristics, topographic features, slope patterns and status of erosion wereobtained through direct observation, soil sampling and farmer interviews. Secondary data
was also collected. A ﬁeld survey was done toascertain the dominant and existing land usesin the area. A land use map of Bedugul area
produced by the local government of Bali wasused as a baseline map.
The boundaries of each land use were delineated using an air photography, topographic
map (+ : ,/,***) and a slope map where +, land

units were identiﬁed as presented in Fig. +.
Soil sampling was done based on slope sequence, slope class and land status. The soil’s
physical and chemical analysis were done at
the Laboratory of Soil Science in Udayana University. The degree of erosion was evaluatedusing the Universal Soil Loss Equation (USLE)
formulated by Wischmeier and Smith (+312)
which states that :ARῌKῌLῌSῌCῌP
where, A is the predicted soil loss (t ha+ y+), R
is the annual rainfall erosivity factor (MJ mmha+ h+ y+), K is the soil erodibility factor(t ha h MJ+ ha+ mm+), L is the slope length
factor, S is the slope steepness factor, C is thecover and management factor and P is theconservation support practice factor.
Each component of the USLE as applied tothe research site was determined based on cer-῏῎ : Land Characteristics and Soil Erosion in Relation to Slope Farming in the Highlands of Candikuning, Bali, Indonesia

Fig. ,39

Topography map of Candikuning, Tabanan, Bali, Indonesia

tain equations such that the rainfall erosion
index (R) was calculated based on Bols’s equation (Bols, +312). The values for of K and LSfactors were calculated based on the equationaccording to Wischmeier and Smith (+312).
Values for C and P factors were based on theCP values published by Hammer (+32*). The
tolerable soil loss as computed by Hammer(+32,), was also the basis of determining themagnitude of erosion from each land unit
identiﬁed in the research site.
Results and Discussion
Agro-climatic and Meteorological Characteristics
When monthly rainfall is less than 0* mm, it
is dry season while rainy season is characterized by rainfall more than +** mm (Sandy,+321). In the research site, the months from
October to April is rainy season and May toSeptember are the dry months. The meanannual rainfall is ,,/02 mm.
Minimum and maximum temperatures wererecorded at +.῍ and ,.῍, respectively. Monthly evaporation was also found to be high in
October and low in June with a daily mean of-., mm. The magnitude of evaporation issigniﬁcantly correlated with temperature.
Monthly relative humidity recorded show thatthe highest occurred in March and the lowestin October with daily mean of 21.3ῌ.
Topography and Slope Pattern
Areas with ﬂat to undulating topography
and having a slope of *ῌ2ῌ account for ,/ῌ(about /0, hectares) of the research area. However, areas with moderate to steep slopesΐῐ῎῔῕ῑ ῒ 21 ῏ ῌ,**+῍40Fig. -Slope map of Candikuning, Tabanan, Bali, Indonesia

occupy 1/ῌ (about +,1,2 hectares) of the totalarea. Steep lands are usually prone to erosion
and cultivation could exacerbate the problem.
The topographic and slope class maps of theresearch area are shown in Figs. , and -, respectively.
Soil Characteristics
Tables + and , present the physical andchemical properties of the soil in the researcharea, respectively. Soil texture ranges fromsilty loam to loamy sand, although there is aconsiderable amount of sand present. The
dominance of sand causes some elements, particularly nitrate nitrogen to decrease rapidlyeither by leaching or runo#. This explains thevery low availability of nitrogen.
Other parameters analyzed to determine thefertility status in the area included CEC, basesaturation and organic carbon content(Puslittanak, +33/). As the parent material ofthese soils is intermediary volcanic ash temporary deposited from surround volcanoes, theytend to have high nutrient content. The soil
fertility status in the research area is presented
in Table -.
It was also found that the fertility of the soilin the lower slope is relatively higher compared to the middle and upper slopes. This is a
result of nutrient deposition in the lower slopes
from the upper slopes because of erosion. As
consequence of advanced erosion, nutrient
availability may drop in long-term.
Land Use
Candikuning village is dominated by forest῏῎ : Land Characteristics and Soil Erosion in Relation to Slope Farming in the Highlands of Candikuning, Bali, Indonesia

Table +Samples
Codes

Characteristics

41

Physical properties of the soil in the research area
Depth Sand Silt(cm)(ῌ) (ῌ)Clay(ῌ)TextureBulk
Structure Permeabilitydensity(cm sῌ+)(g cmῌ-)S+ (.)

Bukit Catu(dry land(slope : ,-ῌ))*ῌ-*-*ῌ0*2/42
3+4/,42.42+4.
-41

Loamy SandSand

GranularGranular+40+῍+*ῌ+4+3῍+*ῌ-*430*43+S, (-)

Bukit Catu(dry land (+/ῌ))*ῌ-*-*ῌ0*20420+4/14/-042/41+41

Loamy Sand
Sandy Loam

GranularGranular04+3῍+*ῌ.
-4+1῍+*ῌ.

*413
*400

S- (-)

Kembang Merta(dry land (++ῌ))*ῌ-*-*ῌ0*//42,04--*4+/*4++.4+,-40

Sandy Loam
Silty Loam

GranularGranular-4.1῍+*ῌ.
04++῍+*ῌ.

*42*41,

Kembang Merta(dry land (2ῌ))*ῌ-*-*ῌ0*-.43/.41//4,-*42.43+.4/

Silty Loam
Sandy Loam

GranularGranular.4/*῍+*ῌ.

S. (,)+4,1῍+*ῌ-*42.
*42.

S/ (,)

Kembang Merta(dry land (-ῌ))*ῌ-*-*ῌ0*0/410-4*+04,340+24*
14.

Sandy Loam
Sandy Loam

GranularGranular24,/῍+*ῌ.
+4--῍+*ῌ-*41*410Forrest land (1ῌ)*ῌ-*-*ῌ0*.340
2.4-.340+-43*42+41

Sandy Loam
Loamy Sand

GranularGranular

34/2῍+*ῌ.

S0 (2)*41,*41*

Table ,

Chemical properties of the soil in the research area
Base
CEC
(c mol/kg) saturation(ῌ),4,1῍+*ῌ-Samplescodes(Land unit)

Depth(cm)pH(H, *)

Org. matter(ῌ)

S+ (.)*ῌ-*-*ῌ0*/421
04,3+40*42/+,4++
+,42*

2,410
224+-

*4*/2
*4*+/

20410
-+4/3,14/2--4,3S, (-)

*ῌ-*
-*ῌ0*

04**
04-2

-410
-4*+

+140*
+041.

334/0
3.41.

*4+2*
*4+,-

3141+,4+---4-+,.413

S- (-)

*ῌ-*
-*ῌ0*

/402
/4,2-4,1,400+14+3+34//

-.4+/
.04/,

*4*2+
*4*0.

,,43.
+*421

0+4,0
214.-

S. (,)*ῌ-*-*ῌ0*/421
04+,,43*+41-+.4,1,,4..

3/4/-+402

*4*0*
*4*-+

1-4*2
34*,

++34*0+.34/+

S/ (,)*ῌ-*-*ῌ0*.420
/4.0

-402
,4/-+34/,+.4.3//43,234/0

*4*..
*4*0+

1/4./.40*

,/4.3
-+40.

S0 (2)*ῌ-*-*ῌ0*/43.
04+2

-4,2
,4/*

+-422
,*4-,

3*43+
3042.

*4*22
*4*01

+14-*
143+.-421,1422

Table -

Soil fertility status in the research area

Samplescodes(Land unit)

Location

Slopes(ῌ)

Fertility
statusS+ (.)
S, (-)
S- (-)
S. (,)
S/ (,)
S0 (2)

Bukit Catu
Bukit Catu
Kembang Merta
Kembang Merta
Kembang Merta
Forrest land,+/++
21

mediumvery highmediumhighvery highhigh

Total-N(ῌ)

Available-P Available-K
(ppm)
(ppm)

with a total area of about +,,/- hectares, distributed in the surrounding part of Beratan
Lake and in the western part of the village.
The forest area includes parts of Mt. Pohen, Mt.
Tapak and the Botanical Garden of Bedugul.
The major land use classiﬁcations in the village include forest, dry land crops, settlements
and lake. Land uses patterns and their distribution is described in Fig. .. Vegetable is thedominant dryland crop, which include cab-42Fig. .

21,**+

Land use map of Candikuning, Tabanan, Bali, Indonesia

bage, potato, carrot, lettuce, garlic, celery andothers. Corn, sweet potato and banana are also
planted in the dry lands and consist of about
0.- hectares.
ErosionValues for the USLE equation factors as determined from the research site are presented
in Table .. Table / presents comparison between the actual level of erosion and the valueof tolerable soil loss in the research area. Basedon these calculation, predicted soil erosion in
the research area was delineated in map asshown in Fig. /.
It was found out that the soil erosivity washigh during the months of October to March,which are within the rainy season. Soil erodibility was classiﬁed as moderate to veryhigh. This is mainly due to the high percentage of very ﬁne sand and silt and low clay
content. As regards the slope length and steepness (LS) factor, the increase in length andsteepness of slope results to higher LS values
for the USLE.
The applied soil conservation measure in thedryland vegetable areas was bench terrace, although the quality of terraces in the lowerslopes is better than those constructed in theupper slopes. This condition caused stabilityof the bench terrace riser in the upper slopes islower than in the lower ones. Accordingly, thelocations in the dryland vegetable crops with
+/ῌ-*ῌ slope, experience a severe tovery severe erosion occurrence. Aside from theslope, low density of vegetation contributed toῐ῏ : Land Characteristics and Soil Erosion in Relation to Slope Farming in the Highlands of Candikuning, Bali, Indonesia

Table .

43

Values of the USLE components as determined in the research areasLandunitErosivity(MJ mm haῌ+hῌ+ yῌ+)(R)

Erodibility(t ha h MJῌ+haῌ+ mmῌ+)
(EK)

+,.
/
0123+*+++,,+,10,+,10,+,10,+,10,+,10,+,10,+,10,+,10,+,10,+,10,+,10,+,10*4*+1*4*.+**4*,0,*4*+2+*4*-*2*4*-*2*4*-/.
*4*-/.
*4*-/.
*4*-/.
*4*-/.
*4*-/.

Slope Cover and Conservation Predictedfactor management practices
soil erosion
factorfactor(t haῌ+ yῌ+)
(ELS)
(EC)
(EP)
(A)

Level ofsoil erosion*4,+4.*+432/4/*
34/*
340*
*41/
,4**
/4**
24/*
+24-+
--4-,

very slightmoderate
moderateseverevery severe
very severe
very slightvery slightslightslightslightslight

*4.**
*4.**
*4.**
*4.**
*4.**
*4-**
*4**/
*4**/
*4**/
*4**/
*4**+
*4**+

*4+/
*4+/
*4+/
*4-/
*4-/
*4.*
+4**
+4**
+4**
+4**
+4**
+4**

/4*2
1-4,1
004,,
,304/,
21+4/,
1/.4++,42,14/+242-,4*+
+-413
,/4+*

A῎R · EK · ELS · EC · EP

Table /

Comparison of the predicted soil erosion and tolerable soil loss in the research areas

Landunit

Soil depth(mm)

Depth factor(mm yῌ+)Resource life(y)Predictedsoil erosion(t haῌ+ yῌ+)Tolerablesoil loss
(t haῌ+ y)

Degree oferosion

+,.
/
012
3
+*
++
+,

++**
+*/*
+,**
++**
++/*
+*/*
+,**
++**
+*/*
3/*
+***
2/*

+4*
+4*+4*
+4*
+4*
+4*
+4*
+4*
+4*
+4*
+4*
+4*

-**
-**
-**
-**
-**
-**-**
-**
-**
-**
-**
-**

/4*2
1-4,1004,,,304/,
21+4/,
1/.4++,42,14/+242-,4*+
+-413
,/4+*

-401
-4/*
.4**
-401
-42-4/*
.4**
-401
-4/*
-4+1-4-,42-

Very slightModerate
Moderate
SevereVery severe
Very severe
Very slight
Very slight
SlightSlightSlightSlight[Tolerable soil loss] ῎ [Soil depth (mm)] ῍ [Depth factor] / [Resource life (years)] .

the higher rates of erosion.
On the other hand, the forestlands and dry
vegetable crop areas with less than -ῌ slope
have only slight erosion. Combination between intensive soil surface protection (by vegetation canopy), e#ective soil conservation
measures and appropriate cropping pattern inthe high risk erosion such as the dryland vegetable area, should be established to prevent soil
erosion and maintain soil fertility as a prereq-

uisite to achieve sustainable farming system intropical volcanic highland.
Conclusion
Forest and dryland vegetable crops dominate the major land use in the research area.
The main physiography in the area is volcanic,
with rolling to mountainous landforms. Thearea has a moderate to steep slope. General soil
fertility status ranges from medium to highΐῐ῎῔῕ῑ ῒ 21 ῏ ῌ,**+῍44Fig. /Erosion map of Candikuning, Tabanan, Bali, Indonesia

due to high organic matter content and basesaturation. Important limiting factor of soil
fertility is low nitrogen. Soil texture is sandyand has low bulk density.
The erosion degree in the area ranges fromvery slight to very severe, depending on land
status. Erosion occurred slightly in the forestland, but it was severe in the drylands withslope more than +/ῌ. To achieve sustainable
farming in the slope lands, e#ective conservation measures combined with soil surface protection and appropriate cropping patternshould be establish in the tropical volcanic
highland.
References
Bali Local Government (+33/) : Land Planning ofBali Province. In : ,*+*, Facts and Analysis.

Bali Local Gov’t., Denpasar (In Indonesian).
Bols, P.L. (+312) : The Iso-erodent Map of Java andMadura. Soil Research Institute, Bogor, Indonesia (In Indonesian).
Dai, J. and Rosman (+31*) : Reconnaissance Soil
Map of Bali. Soil Research Institute, Bogor,Indonesia (In Indonesian).
Hammer, W.I. (+32*) : Soil Conservation Consultant
Report. Technical Note No. 1. FAO Project
INS/12/**0. Center for Soil Research, Bogor,Indonesia.
Hammer, W.I. (+32*) : Final Soil Conservation Consultant Report. Technical Note No. ,0. AGOF/
INS/12/**0. Center for Soil Research, Bogor,Indonesia.
Puslittanak Team. +33/. Technical Method for Soil
Fertility Evaluation. Tech. Report No. +/. Version +. Center for Soil and Agroclimate, Bogor,Indonesia (In Indonesian).
Sandy, I.M. +321. Regional Climate of Indonesia.
University of Indonesia, Jakarta.

῔¼ : Land Characteristics and Soil Erosion in Relation to Slope Farming in the Highlands of Candikuning, Bali, Indonesia

Wischmeier, W.H. and D.D. Smith. +312. Predicting
Rainfall Erosion Losses. A Guide to Conserva-ῌ

45

tion Planning. USDA Agric. Handbook No.
/-1.+.

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