IndonesianSoil properties Journal of the of eastern Agricultural toposequence Science of4(1) Mount 2003: 1-11 1

SOIL PROPERTIES OF THE EASTERN TOPOSEQUENCE OF MOUNT KELIMUTU, ISLAND, AND THEIR POTENTIAL FOR AGRICULTURAL USE

Hikmatullah, H. Subagyo, and B.H. Prasetyo

Indonesian Center for Soil and Agroclimate Research and Development Jalan Ir. H. Juanda No. 98, Bogor 16123,

ABSTRACT 15,000 ha. Its caldera has three-colored lakes, i.e., dark red, green, and bluish colors. The color always changes Kelimutu stratovolcano is one of the young volcanoes exten- with season, making it an interesting tourism site. To sively found in Flores island. Studies on volcanic soil properties date, studies on soil properties and their suitability and their suitability for agricultural development in the whole for supporting agricultural development of the whole island are lacking. The research was conducted to evaluate the relationship of elevation and soil properties, and suitability for island are lacking. agricultural development. Five representative pedons at eleva- Soils of the Kelimutu were developed from andesitic tion of 550, 1,000, 1,200, 1,400, and 1,600 m above sea level volcanic rocks, and dominantly grouped into Andi- (asl), respectively, were studied in the field, and 22 soil samples sols, Mollisols, and Inceptisols (Hikmatullah et al. were analyzed in the laboratory. The results indicated that 1997). According to Suwarna et al. (1990), Kelimutu elevation significantly affected soil properties and degree of had been erupting and collapsing, as shown soil weathering. With decreasing elevation, sand content, amorphous material content, and phosphate retention de- by the formation of three-lake calderas. The erupted creased. Concomitantly, clay content, H2O-pH, exchangeable materials were composed of lava, breccias, agglomer- Ca and Mg, base saturation, and soil-CEC increased. A highly ate, ash and sandy tuffs, all of andesitic to basaltic positive correlation was shown between P retention and NaF- composition. Shoji et al. (1975) reported that andesitic pH, Al, and (Al+0.5 Fe) contents extracted by acid ammonium and basaltic volcanic rocks were composed of SiO2 as oxalate. Soil-CEC also showed significant positive correlation with clay and silt contents, organic carbon, and exchangeable much as 53.5-62% and 45-53.5%, respectively. Mineral Ca and Mg. Degree of weathering increased with decreasing assemblage consists of plagioclase-andesine, pyro- elevation as reflected by decreasing silt/clay ratio. Soils de- xenes, hypersthenes, augite, and olivine. From the veloped from Entisols (Lithic Udorthents) at 1,600 m asl, to landform view, the landscape of Kelimutu may be Andisols (Typic Hapludands) at 1,000-1,400 m asl, and divided into summit, volcanic upper slopes, middle Mollisols (Typic Hapludolls) at lower elevation down to 550 m slopes, and lower slopes (Hikmatullah et al. 1997). asl. Soils at 1,400-1,600 m asl are unsuitable for agriculture. Soils at 1,000-1,200 m are moderately suitable for food crops, The soil study following a toposequence is useful horticulture, and estate crops. Dominant limiting factors are to understand the change of physical, chemical, and steep slopes and P retention. Soils at 550 m asl are suitable for mineralogical soil properties with increasing eleva- food and estate crops, and also lowland horticulture. tion, and to assess their suitability for crop develop- [Keywords: Soil chemicophysical properties, mineral content, ment. Subardja and Buurman (1980) studied a topo- soil classification, land suitability, East Nusa Tenggara] sequence of soils derived from andesitic volcanic materials of the Gede-Pangrango volcanoes in the humid -Bogor-Jakarta area, and the results INTRODUCTION showed that elevation influenced soil properties, degree of weathering, and soil development. With Flores island, with a total area of 1.42 million ha is one decreasing elevation, soil sequence was found chang- of the major islands in East Nusa Tenggara Province. ing from Andisols to Inceptisols, and became Oxisols The southern part of the island, from west to east, is in the low elevation. Down to lower elevation, the dominated by volcanic landform and about 32% is soils became more weathered and developed, and made up of young volcanoes, a few of them are still leaching of bases/nutrients was more intense. Similar active. One of these young volcanoes is Mount results were also reported by Van Schyulenborgh Kelimutu in the , a stratovolcano having (1957) and Subagyo et al. (1997) in a toposequence of the peak of 1,650 m asl, with a total area of about soils at various elevations of volcanoes in West . 2 Hikmatullah et al.

Subagjo and Buurman (1980) studied a soil catena and soil moisture content (water contents at 33 kPa developed from andesitic volcanic materials under minus those at 1,500 kPa water retention). Chemical relatively dry climate condition on the western slope analyses included pH (in H2O and NaF solution), of Lawu volcano. They found that the soil sequence organic carbon, potential P2O5 and K2O contents by starting from the highest elevation was Andisols- HCl 25% extraction, exchangeable bases (Ca, Mg, K, Inceptisols-Alfisols-Vertisols. Na) and soil cation exchange capacity (soil-CEC) by

This study aimed to evaluate the relationship be- 1N NH4OAc pH 7.0 extraction, base saturation (per- tween elevation and soil physical, chemical and centage of sum of exchangeable bases relative to mineralogical properties in relation to degree of soil CEC), P retention by Blakemore et al. (1981), Al and weathering in a toposequence, and soil suitability for Fe contents extracted by acid ammonium oxalate, crop establishment to support agricultural develop- defined as amorphous aluminum (Alo) and amorphous ment. iron (Feo) (Ping et al. 1988). Mineralogical composition of sand mineral fraction was determined by line counting method using pola- MATERIALS AND METHODS rization microscope. Clay mineral composition was determined using X-ray diffractometer (XRD), with Climate and Vegetation standard saturation of Mg and K saturation plus heating to 550oC. Methods of analyses followed the The study area has a humid tropical climate. The standard procedures described in Soil Survey Labo- mean annual rainfall is 1,508 mm in the lowland of ratory Methods Manual (Soil Survey Laboratory Staff Ende (20 m asl), and becomes higher with increasing 1991). Regression analysis was used to analyze the elevation, i.e. 3,700 mm at Detusuko (650 m asl). correlation between some important soil properties. Rainfall type according to Schmidt and Ferguson The studied pedons were classified according to Soil (1951) is classified as C (relatively dry) at lowland, Taxonomy (Soil Survey Staff 1998) at subgroup level. and A (very wet) at higher elevation. Soil moisture The soil suitability for food crops, horticulture, and regime changes from ustic at lowland to udic at Detu- estate crops was determined using the criteria out- suko and higher elevation. Air temperature decreases lined by Djaenudin et al. (2003). with increasing altitude, from mean monthly of 27.7oC at Ende, 23.0oC at Detusuko, to 20.3oC at highland (Hikmatullah et al. 1997), therefore soil temperature regime also changes from isohyperthermic to iso- RESULTS AND DISCUSSION thermic. The present landuse of the area was com- posed of maize and sweet potatoes in the lower slope, Physical Properties horticultural crops, i.e., cabbage, potatoes, and carrot Downslope with decreasing elevation, as sand con- in middle slope, and pine forest in upper slopes and tent decreased, clay content significantly increased summit area of the volcano. (Table 2). The increasing clay content feature can be used as an indicator for increasing degree of weath- Soil Sampling ering. Van Wambeke (1962) used silt and clay ratio to Five representative pedons at the eastern topo- estimate the degree of weathering of soil pedon, and sequence of the volcano, at elevation of respectively postulated that the lower the ratio, the higher the 1,600, 1,400, 1,200, 1,000, and 550 m asl were selected degree of weathering. By increasing weathering, the for the study (Fig. 1). The description of soil morpho- silt fraction changed into clay fraction so that clay logical properties in the field was carried out follow- content increased, thus the silt and clay ratio was to ing the guideline outlined by FAO (1990). As much as be lower. 22 soil samples from each horizon of each pedon were Particle size distribution data showed that as selected for physical, chemical, and mineralogical elevation decreased, sand fraction consistently analyses in the laboratory (Table 1). decreased, silt fraction more or less constant, and the clay fraction significantly increased. As a result, silt and clay ratio (Table 2) consistently became smaller Laboratory Analyses with decreasing elevation. Therefore, it may be Physical analyses consisted of particle size distribu- concluded that the degree of soil weathering in- tion (three fractions) using Pipette method, bulk creased with decreasing elevation. With decreasing density at 33 kPa water retention, total pore space, elevation, particle size class became finer and finer, Soil properties of the eastern toposequence of Mount Kelimutu 3

Fig. 1. Location of the studied pedons, Ende regency, Flores island, East Nusa Tenggara.

Table 1. Distribution of pedons and soil samples on toposequence of Mount Kelimutu, East Nusa Tenggara.

Pedon Elevation Slope gradient Dominant landuse Number of number (m asl) (%) sample

K-1 1,600 38 Pine forest 2 K-2 1,400 32 Pine forest and shrub 5 K-3 1,200 22 Shrub and pine forest 5 K-4 1,000 20 Maize, horticulture 5 K-5 550 18 Cassava, sweet potatoes 5

that was, gradually changed from coarse-loamy to density became higher (0.68 and 1.01 g cm-3 vs. 1.14 fine loamy, and eventually fine or clayey. These find- and 1.18 g cm-3), total pore space was smaller (74 and ings are in agreement with the results reported by 62% vs. 57 and 55%), and available moisture content Subagjo and Buurman (1980) and Honeycutt et al. decreased (10.0 and 19.1% vs. 10.4 and 6.8%). (1990). Soil physical property data represented by two Chemical Properties pedons, i.e. K-2 (1,400 m asl) and K-4 (1,000 m asl), and by two different horizons, i.e. topsoil and sub- Soil H2O-pH varied with elevation. Pedon K-1 (1,600 m soil, indicated that by decreasing elevation, bulk asl) was extremely acid (pH 4.3-4.5) under pine forest 4 Hikmatullah et al.

Table 2. The particle size distribution, pH, phosphate (P) retention, P2O5 and K2O-25%HCl of Mount Kelimutu soils, East Nusa Tenggara.

Horizon Particle size distribution Textural Silt/ pH P- Org. HCl 25% extract. reten- depth class/ clay C Sand Silt Clay H2O NaF tion P2O5 K2O (cm) PSC ratio (%) ...... (%) ...... (%) (mg 100 g-1 soil) Pedon K-1 (1,600 m asl) 0-15 73,5 17.2 9.3 SiCL/CoLo 1.85 4.5 10.5 59 2.95 52 171 15-40 56.5 29.8 13.7 SL/CoLo 2.18 4.3 10.2 50 1.45 48 149 >40 Consolidated rock

Pedon K-2 (1,400 m asl) 0-16 63.8 25.2 11.0 SiC/CoLo 2.29 5.3 10.7 70 4.06 56 75 16-57 63.8 26.7 9.5 SiL/CoLo 2.81 5.6 11.2 80 1.80 49 69 57-90 63.0 29.8 7.2 SiL/CoLo 4.14 5.4 11.3 78 0.95 - - 90-126 72.6 23.9 3.5 SiL/CoLo 6.83 5.3 11.4 94 2.18 - - 126-190 72.3 26.2 1.5 SiL/Sandy 17.47 5.4 11.3 78 0.81 - - Pedon K-3 (1,200 m asl) 0-25 72.1 19.6 8.3 SiCL/CoLo 2.36 5.7 11.2 78 3.61 52 39 25-51 67.9 25.1 7.0 SiL/CoLo 3.59 5.8 11.3 79 2.62 34 35 51-112 66.2 26.0 7.8 SiL/CoLo 3.33 6.0 10.9 65 1.40 - - 112-150 20.0 70.5 9.5 SiL/CoLo 7.42 5.8 10.7 74 3.95 - - 150-180 34.9 29.6 35.5 SiC/Fine 0.83 6.1 9.5 50 1.46 - - Pedon K-4 (1,000 m asl) 0-16 55.4 26.2 18.4 SiL/FiLo 1.42 5.9 9.2 31 1.90 50 62 16-42 52.7 28.6 18.7 SiL/FiLo 1.53 6.1 9.4 36 1.62 42 88 42-70 55.8 24.3 19.9 SiCL/FiLo 1.22 6.4 9.3 33 1.47 41 83 70-90 54.6 29.5 15.9 SiCL/CoLo 1.86 6.5 9.3 30 0.81 - - 90-130 51.1 30.5 18.4 SiCL/FiLo 1.66 6.6 9.3 32 0.62 - -

Pedon K-5 (550 m asl) 0-15 43.6 27.1 29.3 L/FiLo 0.92 6.3 9.4 36 2.01 7 51 15-45 17.1 29.7 53.2 C/Fine 0.56 6.4 8.9 28 1.04 5 24 45-78 15.3 36.3 48.4 C/Fine 0.75 6.5 9.0 29 0.82 6 16 78-108 23.7 41.0 35.3 CL/Fine 1.15 6.6 9.3 33 0.72 - - 108-153 29.1 39.9 31.0 CL/FiLo 1.23 6.7 9.4 35 0.70 - - PSC = particle size class; CoLo = coarse-loamy; S = sandy; FiLo = fine-loamy; - = not analyzed

vegetation. Downslope with decreasing elevation, Organic carbon contents in the pedons over 1,000 m soil reaction was strongly acid (pH 5.3-5.4) in pedon asl were generally low to high in the subsoil, due to K-2 at 1,400 m asl, changed to moderately acid (pH the presence of burried A horizons, and high in the 5.7-6.0) in pedon K-3, and slightly acid (pH 6.1-6.5) in topsoil. In pedons at and below 1,000 m asl, probably pedon K-4 at 1,000 m asl, and finally slightly acid to due to increasing soil temperature, organic carbon neutral (pH 6.3-6.7) in pedon K-5 at 550 m asl. contents were low to very low in both topsoil and Soil NaF-pH value of more than 9.4 is often used as subsoil. This agrees with result reported by Botschek an indicator to show the presence of amorphous et al. (1996). Other reason of such low to very low material (Ping et al. 1988), that later called short-range contents of soil organic carbon is a long time use of order materials, while Alvarado and Buol (1982) soils for upland farming without addition of organic suggested the lower limit of NaF-pH 10.7 to signify matter or green manure. soils rich in short-range order materials. Using this In the upper 50-70 cm soil layer, P2O5 was generally last NaF-pH value, it is concluded that significant high and K2O was very high in pedons of 1,000 m asl amount of short-range order materials is present in and higher. At the lowest elevation of 550 m asl, their pedon K-2 and major parts of pedon K-3 (Table 2). contents decreased to very low for P2O5 and medium

This seemed to be supported by phosphate retention, for K2O. Although P content in soils of higher than which was very high (65-94%) in most horizons of 1,000 m asl was high, it was not readily available to both pedons. crops due to very high P retention. In these soils, the Soil properties of the eastern toposequence of Mount Kelimutu 5

Table 3. Exchangeable cations, CEC, acid ammonium oxalate extractable Al and Fe, and physical properties of Mount Kelimutu soils, East Nusa Tenggara.

Horizon Exchangeable cations NH4OAc Acid amm. oxalate extr. Physical property depth pH 7.0 ext. Ca Mg K Na Total Al Fe (Al +0.5 Fe ) BD TPS AMC (cm) Soil-CEC BS o o o o ...... (cmol (+) kg-1) ...... (%) ...... (g cm-3) ..... (%) ..... (cmol (+) kg-1) (%) Pedon K-1 (1,600 m asl) 0-15 0.51 0.13 0.16 0.09 0.89 10 9 0.86 - - - - - 15-40 0.51 0.12 0.08 0.09 0.80 6 13 0.63 - - - - -

Pedon K-2 (1,400 m asl) 0-16 7.01 0.82 0.16 0.15 8.14 12 66 0.76 0.81 1.2 0.68 74 10.0 16-57 3.73 0.43 0.08 0.09 4.33 5 81 1.12 0.87 1.6 - - - 57-90 1.39 0.14 0.02 0.09 1.64 4 44 1.63 0.43 1.8 1.01 62 19.1 90-126 2.11 0.26 0.02 0.22 2.61 7 39 2.44 0.66 2.8 - - - 126-190 0.88 0.10 0.02 0.23 1.23 4 34 1.77 0.65 2.1 - - - Pedon K-3 (1,200 m asl) 0-25 11.41 1.55 0.30 0.11 13.37 13 100 1.40 0.67 1.7 - - - 25-51 6.32 1.16 0.31 0.09 7.88 11 75 1.29 0.57 1.6 - - - 51-112 5.92 0.97 0.31 0.15 7.35 8 96 1.18 0.65 1.5 - - - 112-150 20.68 2.37 1.13 0.36 24.54 28 89 1.19 0.68 1.5 - - - 150-180 13.29 2.24 1.92 0.48 17.93 18 100 0.44 0.82 0.8 - - - Pedon K-4 (1,000 m asl) 0-16 10.34 2.45 0.72 0.12 13.63 14 100 0.34 0.69 0.7 1.14 57 10.4 16-42 9.77 2.66 0.83 0.13 13.39 13 95 0.36 0.74 0.7 - - - 42-70 10.50 3.34 0.85 0.18 14.87 15 100 0.41 0.79 0.8 1.18 55 6.8 70-90 9.55 3.21 0.73 0.21 13.70 14 100 0.33 0.66 0.7 - - - 90-130 11.36 4.12 0.65 0.27 16.40 16 100 0.22 0.34 0.4 - - -

Pedon K-5 (550 m asl) 0-15 14.57 4.34 0.65 0.19 19.75 21 94 0.34 - - - - - 15-45 21.63 6.12 0.17 0.76 28.68 36 81 0.21 - - - - - 45-78 22.69 6.36 0.11 0.95 30.11 38 79 0.23 - - - - - 78-108 22.76 6.49 0.09 1.01 30.35 38 80 0.29 - - - - - 108-153 21.98 6.62 0.09 0.93 29.62 38 77 0.32 - - - - - CEC = cation exchange capacity; BS = base saturation; BD = bulk density; TPS = total pore space; AMC = available moisture content; - = not analyzed.

released P was readily fixed by short-range order (1,000-1,200 m asl), lot of exchangeable cations had materials, which was rich in Al and Fe, to form Al-P been released, so that their total contents became and Fe-P compounds. In soils at and below 1,000 m medium to high in particular exchangeable Ca and Mg. asl, due to their medium P retention, availability of P In soils at lower elevation of 550 m asl, in which seemed to be higher. It is already known that soils weathering has fully worked, total of exchangeable from young volcanic materials are rich in short-range cation contents became high to very high (Table 3). order materials and have a high to very high P Soil-CEC tends to increase with decreasing eleva- retention, and thus usually need higher amount of P tion. At higher elevation, soil-CEC values ranged fertilizer. from 4 to 12 cmol (+) kg-1 soil. It increased to 8-16 Exchangeable cations and their total seemed to be cmol (+) kg-1 soil in soils of medium elevation, and at related with elevation, and thus also related to degree 550 m asl it increased to 21-38 cmol(+) kg-1 soil. As of soil weathering. As has been discussed earlier, soil expected, soil-CEC increased with the increase in clay weathering tends to increase with decreasing eleva- content. Base saturation was very low (9-13%) in soils tion. In pedons K-1 and K-2 (1,600-1,400 m asl), of at the highest elevation (1,600 m asl). With decreasing which weathering was not yet fully developed, ex- elevation, base saturation became greater, i.e. medium changeable cation contents, i.e. Ca, Mg, K, and Na, (34-44%) in the subsoil and high (66-81%) in the and their total were generally very low to low. As soil topsoil. Further down at 1,200-1,000 m asl, base weathering increased in pedons of medium elevation saturation was very high (95-100%). However, further 6 Hikmatullah et al. down to 550 m asl, perhaps due to increased leaching, soil-CEC also has a positive relatively good linear base saturation became slightly lower (Table 3). The relationship with clay content (r2 = 0.69); a positive 2 contents of Alo + 0.5 Feo in the pedons K-2, K-3, and poor exponential relationship with silt content (r = K-4, totaling between 0.4 and 2.8%, and together with 0.36); and a positive good linear relationship with the amount of P retention of 25% or more, and the organic carbon content (r2 = 0.84). Beside that, soil- contents of volcanic glass of more than 5% fulfilled CEC has a positive very good linear relationship with the requirements of the andic soil properties (Ping et exchangeable Ca and Mg, with r2 of 0.92 and 0.86, al. 1988). respectively.

Relationships Between Soil Properties Mineralogical Composition

Figure 2 shows the relationships between P retention Mineralogical composition of the soils as represented and NaF-pH, Alo, Alo + 0.5 Feo and clay content. P by the sand fractions of pedons K-2 and K-4 was retention has a positive exponential relationship with similar, though the mineral components differed in NaF-pH, with a correlation coefficient, r2 = 0.98. P percentages (Table 4). The sand fraction was domi- retention also has a positive linear relationship with nated by andesine (intermediary plagioclase), hyper- 2 Alo and Alo + 0.5 Feo contents with r = 0.87 and 0.85, sthenes and augite (pyroxenes), volcanic glass, and respectively. Similar results were also reported by rock fragments, with few hornblende, weathered Sukarman and Subardja (1997), Hikmatullah et al. mineral fragments, and resistant opaque and quartz. (2000), and Prasetyo et al. (2001). However, P reten- Such mineral composition indicated an intermediary or tion seems to have a negative exponential relation- andesitic volcanic character of the eruption products. ship with clay content with r2 = 0.67. This means that This is in agreement with the original geologic if NaF-pH, Alo, and Alo + 0.5 Feo values increase, there description of Suwarna et al. (1990), and supported is a chance that P retention becomes higher. On the by the findings of Hikmatullah et al. (1999) and contrary, as clay contents increases because weather- Sukarman et al. (1999). ing increase for example, P retention tends to become In pedon K-2 (1,400 m asl), the amount of resistant smaller. opaque and quartz, and weathered mineral fragments Figure 3 shows that soil-CEC has a negative linear were lower, while rock fragments and volcanic glass relationship with sand content (r2 = 0.85). In addition, were higher compared to those of pedon K-4 (1,000 m

100 120 y = 0.001x4,6647 80 100 r2 = 0.98 60 80 60 40 40 y = 33.377x + 26.601

P retention (%) 20 P retention (%) 20 r2 = 0.87 0 0 0 5 10 15 0231 NaF-pH Alo (%)

120 140 120 100 y = 141.86x-0,403 100 80 r2 = 0.67 80 60 60 40 40 y = 31.975x + 18.124 P retention (%) P retention (%) 20 20 r2 = 0.85 0 0 0 12 3 0406020

Alo + 0.5 Feo (%) Clay content (%)

Fig. 2. Relationship between P retention and NaF-pH, Alo, Alo + 0.5 Feo, and clay content of Mount Kelimutu soils, East Nusa Tenggara. Soil properties of the eastern toposequence of Mount Kelimutu 7 ) )

-1 40 -1 50

30 40 30 20 20

10 y = 0.541x + 44.684 10 y = 0.6692x + 4.2314 r2 = 0.85 r2 = 0.69 Soil-CEC (cmol(+) kg

0 Soil-CEC (cmol(+) kg 0 020406080 0 20 40 60 Sand content (%) Clay content (%) )

50 ) -1 14 -1 40 12 10 30 8 20 6 4 10 y = 24.68Ln(x) - 66.22 y = 2.765x + 1.964 2 2 r2 = 0.36 r = 0.84 Soil-CEC (cmol(+) kg 0 Soil-CEC (cmol(+) kg 0 0 20 40 60 80 02 46 Silt content (%) Organic C (%) ) ) 40 40 -1 -1 y = 1.443x + 1.763 30 r2 = 0.92 30

20 20

10 10 y = 4.687x + 4.842 r2 = 0.86 Soil-CEC (cmol(+) kg Soil-CEC (cmol(+) kg 0 0 0102030 0246 8 Exch. Ca (cmol(+) kg-1) Exch. Mg (cmol (+) kg-1)

Fig. 3. Relationship between soil-CEC and sand, silt, clay, organic carbon, exchangeable Ca and Mg of Mount Kelimutu soils, East Nusa Tenggara.

asl). This suggests that pedon K-2 has a lower degree amorphous or short-range order minerals, probably of of weathering than pedon K-4. This is also supported allophanic nature, as shown by the presence of broad by the higher silt/clay ratio of pedon K-2 (Table 2). irregular reflections with absence of distinct indi- The soils have high amount of weatherable minerals, vidual peaks. However, the presence of somewhat in- as shown by high contents of dark colored minerals distinct small peaks around 10.2 and 7.2Å, is thought and volcanic glass, accounting to more than 50% to be an indication on the presence of hydrated throughout horizons. Since the source of nutrient halloysite and disordered kaolinite. In pedon K-4 reserve was high, the soils were considered to have a (1,000 m asl), the 10.2Å peak of hydrated halloysite of high soil fertility status. This is in accordance with the topsoil, and the 7.2Å peak of disordered kaolinite the finding of Buurman (1990) that the amount of of the subsoil, seemed to be more pronounced. These weatherable minerals in young volcanic soils is findings are in agreement with the results of studies always high, in the order of 30% or more. reported by Sukarman and Subardja (1997) and Clay mineral composition, as represented by topsoil Sukarman et al. (1999). Dominant content of allopha- and subsoil of pedons K-2 and K-4, is presented in nic materials was proven by high P retention, high

Table 5, and their XRDs are illustrated in Fig. 4. contents of Alo and Feo, and high NaF-pH values Mineralogical composition of the clay fractions as (Mizota and van Reeuwijk 1989). seen from the XRD was dominantly composed of 8 Hikmatullah et al.

Table 4. Mineralogical composition (%) of the sand fraction of Mount Kelimutu soils, East Nusa Tenggara. Horizon Rock Volcanic Green Total weath- depth Opaque Quartz Weath. Andesine Augite Hypersthene fragm. glass hornblende mineral (cm) mineral Pedon K-2 (1,400 m asl) 0-16 3 n 6 31 25 17 sp 6 12 60 16-57 1 sp 2 35 25 21 n 6 10 62 57-90 sp n 1 45 28 15 n 5 6 54 90-126 1 n 2 40 23 20 n 6 8 57 126-190 1 n 1 32 26 20 n 6 14 66

Pedon K-4 (1,000 m asl) 0-16 6 1 3 28 9 21 2 10 20 62 16-42 3 1 5 28 13 27 sp 7 16 63 42-70 4 sp 5 18 9 27 1 7 29 73 70-90 6 1 3 19 12 27 5 9 18 61 90-130 4 1 6 21 6 33 5 7 17 68 sp = sparse/very few, n = not detected

Table 5. Mineralogical composition of the clay fraction of Mount Kelimutu soils, East Nusa Tenggara. Horizon depth Disordered Hydrated Short-range Mineralogical Pedons (cm) kaolinite halloysite order material class K-2 (1,400 m asl) Al (0-16) - (+) ++++ Amorphic Bw1 (16-57) - (+) ++++ Amorphic K-4 (1,000 m asl) Ap (0-16) - (+) +++ Amorphic Bw1 (16-42) (+) (+) +++ Amorphic - = absent, (+) = trace, +++ = abundant, ++++ = dominant

Soil Classification Pedon K-5 had a mollic epipedon, and a cambic horizon, with high to very high base saturation (77- All the pedons were classified according to Soil 94%) throughout. The soils had udic soil moisture Taxonomy (Soil Survey Staff 1998) at subgroup level. regime and isohyperthermic soil temperature regime. Pedon K-1 was shallow and had an AC-horizon with Its classification at subgroup level was Typic Haplu- weak soil structure and thin A horizon overlying dolls. consolidated rock. The color and base saturation meet the requirements of an umbric epipedon. Soil moisture regime was udic and soil temperature regime Agricultural Suitability of the Soils was isothermic. Therefore, the pedon was classified at subgroup level as Lithic Udorthents. The soils of the eastern slope of the Kelimutu Pedons K-2, K-3, and K-4 had A-Bw horizon, volcano at elevation of 550-1,600 m asl are generally having similar chemical properties. Their character- well drained and deep to very deep. They have istics meet the requirements of andic soil properties, medium to fine texture, low to medium CEC, organic i.e., fine-earth fraction has P retention of 25% or more, carbon, and available P, medium to very high potential

Alo+0.5 Feo is 0.4-2.0%, and the sand fraction contains P and K, and base saturation. Based on the land 5-30% volcanic glass. Therefore, all of the pedons fit suitability classification of Djaenudin et al. (2003), to be classified into Andisols. Pedon K-2 had an the land is suitable for food crops, vegetables, and ochric, and pedons K-3 and K-4 had mollic epipedon. estate crops (Table 6). They all had cambic diagnostic horizon, with udic soil The two highest elevation soils (pedons K1 and K- moisture regime, isothermic and isohyperthermic soil 2, 1,400-1,600 m asl) are not suitable for both food temperature regimes. They were all classified at sub- crops and vegetables. However, they are still group level as Typic Hapludands. marginally suitable for growing coffee. The present Soil properties of the eastern toposequence of Mount Kelimutu 9

Fig. 4. X-ray diffractograms of the clay fractions of the topsoil and subsoil of pedons K-2 and K-4 of Mount Kelimutu, East Nusa Tenggara.

use of these soils for pine forest is perhap the best constructed with ridge can also reduce runoff and choice for preserving the nature and environment. soil loss in the area. Soils at medium elevation (pedons K-3 and K-4, Soil fertility problems, including low to medium 1,200-1,000 m asl) are moderately suitable for all crops organic carbon content, low CEC, and high P reten- evaluated. With the moderate slopes, growing food tion may be solved by incorporating green manure to crops, vegetables, and estate crops at this elevation increase CEC and soil organic matter. Addition of this range is still possible by improving soil management. fertilizer mixed with high amount of farm manure to The limiting factors for the agricultural practices seem reduce the effect of active Al and Fe of the amorphous to be slope gradient and nutrient retention. Soil materials, is the common practice by highland vegeta- management practices focusing on application of ble farmers in the volcanic areas of Java. appropriate soil conservation techniques are recom- Soils at lower elevation (550 m asl) are moderately mended. These include contour cropping, planting suitable for food and estate crops, but only mar- of perennial crops on field border, and mulching. ginally suitable for highland vegetables. Agricultural Suganda et al. (1999) reported that contour cropping development should be avoided at elevation of above direction was the best method in controlling soil 1,200 m asl within which the area must be left as erosion in sloping areas of highlands. Raised bed protection forest. 10 Hikmatullah et al.

Table 6. Land suitability of Mount Kelimutu soils, East Nusa Tenggara for upland food crops, vegetables, and estate crops.

Elevation Slope Food crops Vegetables Estate crops Pedon (m asl) (%) Maize Sweet potatoes Potatoes Carrot Cabbage Coffee Clove K-1 1,600 38 N N N N N S3 N K-2 1,400 32 N N N N N S3 N K-3 1,200 20 S2 S2 S2 S2 S2 S2 S2 K-4 1,000 20 S2 S2 S2 S2 S2 S2 S2 K - 5 5 5 0 1 8 S2 S2 S3 S3 S3 S2 S2 N = not suitable; S3 = marginally suitable; S2 = moderately suitable

CONCLUSION forest in the Itacoatiara vicinity, Amazonas, Brazil. Geo- derma 72: 119-132. Soil toposequence in the eastern slope of Mount Buurman, P. 1990. Chemical, Physical, and Mineralogical Characteristics for the Soil Data Base. Technical. Report No. Kelimutu showed that elevation significantly influ- 7, version 2.1. LREP Project. Center for Soil and Agro- enced soil properties. With the lower elevation, the climate Research, Bogor. degree of soil weathering increased as reflected by Djaenudin D., H. Marwan, H. Subagyo, A. Mulyani, dan N. increasing clay content. Soil pH, exchangeable Suharta. 2003. Petunjuk Teknis Evaluasi Lahan untuk Ko- cations, and base saturation also increased. On the moditas Pertanian. Versi 3. Balai Penelitian Tanah, Puslit- bang Tanah dan Agroklimat, Bogor (in press). contrary, contents of organic carbon, amorphous FAO. 1990. Guidelines for Soil Profile Description. Land and material, and P retention decreased. Soil physical Water Development Division. FAO-UN, Rome. properties tend to change, as shown by increasing Hikmatullah, Sukarman, T. F. Chendy, dan H. Subagjo. 1997. bulk density and decreasing values of total pore Potensi dan kendala sumberdaya lahan Pulau Flores Propinsi space and available moisture content. Nusa Tenggara Timur. hlm. 345-360. Dalam U. Kurnia (Ed.) The soils were developed from andesitic volcanic Prosiding Pertemuan Pembahasan Hasil Penelitian Tanah dan Agroklimat. Cisarua, Bogor, 7-9 Maret 1997. Pusat materials, with high amount (54-73%) of weatherable Penelitian Tanah dan Agroklimat, Bogor. minerals. Soils developed from Entisols (Lithic Hikmatullah, H. Subagjo, Sukarman, dan B.H. Prasetyo. 1999. Udorthents) at 1,600 m asl, to Andisols (Typic Karakteristik Andisols berkembang dari abu volkanik di Pulau Hapludands) at 1,400-1,000 m asl, and Mollisols Flores, Provinsi Nusa Tenggara Timur. Jurnal Tanah dan Iklim (Typic Hapludolls) at 550 m asl. 17: 1-13. Hikmatullah, H. Subagyo, and B.H. Prasetyo. 2000. Properties Soils between 1,200 and 1,000 m asl are potentially and classification of Andisols derived from volcanic ash in developed for food crops, highland vegetables, and the Tondano area, North . Agrivita, J. Agric. Sci. estate crops. Soil conservation techniques, such as 21(2): 28-40. contour hedge row planting and raised bed are Honeycutt, C.W., R.D. Heil, and C.V. Cole. 1990. Climatic and suggestible to reduce soil erosion and degradation. topographic relations of three great plains soils: I. Soil Soils at lower elevation is generally fertile and morphology. Soil Sci. Soc. Am. J. 54: 469-475. Mizota, C. and L.P. Van Reeuwijk. 1989. Clay mineralogy and suitable for growing food crops and estate crops. chemistry of soils formed in volcanic materials in diverse Soils above 1,400 m asl are unsuitable for agriculture, climatic regions. Soil Monograph 2. ISRIC Wageningen, The and they are better used for forest and nature Netherlands. conservation. Ping, C.L., S. Shoji, and T. Itho. 1988. Properties and classifi- cation of three volcanic ash derived pedons from Aleutian Island and Alaska Peninsula. Soil Sci. Soc. Am. J. 52: 455-462. Prasetyo, B.H., N. Suharta, H. Subagyo, and Hikmatullah. REFERENCES 2001. Chemical and mineralogical properties of Ultisols of Sasamba area, East . Indon. J. Agric. Sci. 2 (2): Alvarado and S.W. Buol. 1982. Field estimation of phosphate 37-47. retention by Andepts. Soil Sci. Soc. Am. J. 49: 911-914. Schmidt, F.H. and J.H.A. Ferguson. 1951. Rainfall types based Blakemore, L.C., P.L. Searle, and B.K. Daly. 1981. Methods for on wet and dry period ratios for Indonesia with Western New chemical analysis of soils. NZ Soil Bureau Sci. Rep. 10A. Soil Guinea. Verh. 42. Djawatan Meteorologi dan Geofisik, Ja- Bureau, Lower Hutt, New Zealand. karta. Botschek, J., J. Ferraz, M. Jahnel, and A. Skowronek. 1996. Soil Shoji, S., S. Kobayashi, I. Yamada, and J. Masui. 1975. Chemical chemical properties of a toposequence under primary rain and mineralogical studies on volcanic ashes. I. Chemical Soil properties of the eastern toposequence of Mount Kelimutu 11

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