B.H. Prasetyo’s research while affiliated with Centre for Ecology Development and Research and other places

Ultisols are a major group of marginal soils extensively found in the upland area of Indonesia. To better understand the potential of the Ultisols developed from claystone and sandstone in the Sasamba Integrated Economical Development Area in East Kalimantan, chemical and mineralogical characteristics of 27 Ultisols pedons consisting of 76 topsoil and 118 subsoil samples were investigated. Besides analysis and interpretation of data, relationships of several soil characteristics were constructed using simple regression. The results indicated that Ultisols showed acid to very acid reaction, had low content of organic matter and low base saturation. Soils generally exhibited net negative charge, and the point of zero charge was reached at pH 3.6. Both potential and available phosphates were low, and there was a trend that amorphous aluminum was responsible for phosphate fixation. The low content of exchangeable potassium in topsoil and subsoil indicated a positive correlation with potential potassium. Clay mineral was composed chiefly of kaolinite, with small amounts of illite, vermiculite, and quartz. The domination of kaolinite and low organic matter content causes the soils to have low cation exchange capacity. Soil management in this area should be focused on building up and maintaining soil fertility, and applying appropriate soil conservation techniques to minimize erosion. To obtain sustained productivity, various soil amendments including the use of farm and/or green manure, liming with agricultural lime, and application of rock phosphate and K fertilizers were highly recommended.

Tidal flats in the Musi Banyuasin region that cover more than 200,000 ha are the largest area for agricultural development in South Sumatra Province. Only about a half of this has been used for tidal swamp rice fields, therefore, the other half needs to be developed. To obtain a better understanding of their properties for appropriate soil management, soil characteristics of the area need to be studied. To characterize the soil, thirty-four soil samples from seven soil profiles were analyzed for their chemical and mineralogical composition at the laboratories of the Center for Soil and Agroclimate Research and Development. The results indicate that soils from the tidal flat areas have an aquic soil moisture regime, the upper parts of the soils are mostly ripe, and most of the pedons show the presence of sulfidic materials below 65 cm of the mineral soil surface. The soils are classified as Sulfic Endoaquept (P1, P2), Histic Sulfaquent (P3), Typic Sulfaquept (P4), Fluvaquentic Endoaquept (P5), and Sulfic Hydraquent (P6, P7). Mineral composition of the sand fraction is dominated by quartz, while the clay minerals consist of predominantly kaolinite, mixed with small amount of smectite, illite, quartz, and crystoballite. Organic carbon content is high to very high, potential phosphate content of most pedons ranges from very low to medium, while potential potassium content varies from very low to medium in the upper layers and medium to very high in the bottom layers. Phosphate retention of topsoil sample varies from 56 to 97%, and is positively correlated (r2 = 0.73) with aluminum from amorphous materials. Exchangeable cations are dominated by Mg cation, and in all pedons cation exchange capacity values are medium to very high, and seem to be influenced by organic carbon. Specific chemical properties, particularly soil pH and content of exchangeable aluminum exhibit a significant change about 1-2 months after soil samples were taken from the field. Theoretically, interaction between good water management and fertilizer application are among the choices of management to make these soils productive.

Kelimutu stratovolcano is one of the young volcanoes extensively found in Flores island. Studies on volcanic soil properties and their suitability for agricultural development in the whole island are lacking. The research was conducted to evaluate the relationship of elevation and soil properties, and suitability for agricultural development. Five representative pedons at elevation of 550, 1,000, 1,200, 1,400, and 1,600 m above sea level (asl), respectively, were studied in the field, and 22 soil samples were analyzed in the laboratory. The results indicated that elevation significantly affected soil properties and degree of soil weathering. With decreasing elevation, sand content, amorphous material content, and phosphate retention decreased. Concomitantly, clay content, H2O-pH, exchangeable Ca and Mg, base saturation, and soil-CEC increased. A highly positive correlation was shown between P retention and NaFpH, Al, and (Al+0.5 Fe) contents extracted by acid ammonium oxalate. Soil-CEC also showed significant positive correlation with clay and silt contents, organic carbon, and exchangeable Ca and Mg. Degree of weathering increased with decreasing elevation as reflected by decreasing silt/clay ratio. Soils developed from Entisols (Lithic Udorthents) at 1,600 m asl, to Andisols (Typic Hapludands) at 1,000-1,400 m asl, and Mollisols (Typic Hapludolls) at lower elevation down to 550 m 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, horticulture, and estate crops. Dominant limiting factors are steep slopes and P retention. Soils at 550 m asl are suitable for food and estate crops, and also lowland horticulture.

Kelimutu stratovolcano is one of the young volcanoes extensively found in Flores island. Studies on volcanic soil properties and their suitability for agricultural development in the whole island are lacking. The research was conducted to evaluate the relationship of elevation and soil properties, and suitability for agricultural development. Five representative pedons at elevation of 550, 1,000, 1,200, 1,400, and 1,600 m above sea level (asl), respectively, were studied in the field, and 22 soil samples were analyzed in the laboratory. The results indicated that elevation significantly affected soil properties and degree of soil weathering. With decreasing elevation, sand content, amorphous material content, and phosphate retention decreased. Concomitantly, clay content, H2O-pH, exchangeable Ca and Mg, base saturation, and soil-CEC increased. A highly positive correlation was shown between P retention and NaFpH, Al, and (Al+0.5 Fe) contents extracted by acid ammonium oxalate. Soil-CEC also showed significant positive correlation with clay and silt contents, organic carbon, and exchangeable Ca and Mg. Degree of weathering increased with decreasing elevation as reflected by decreasing silt/clay ratio. Soils developed from Entisols (Lithic Udorthents) at 1,600 m asl, to Andisols (Typic Hapludands) at 1,000-1,400 m asl, and Mollisols (Typic Hapludolls) at lower elevation down to 550 m 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, horticulture, and estate crops. Dominant limiting factors are steep slopes and P retention. Soils at 550 m asl are suitable for food and estate crops, and also lowland horticulture.

Tidal flats in the Musi Banyuasin region that cover more than 200,000 ha are the largest area for agricultural development in South Sumatra Province. Only about a half of this has been used for tidal swamp rice fields, therefore, the other half needs to be developed. To obtain a better understanding of their properties for appropriate soil management, soil characteristics of the area need to be studied. To characterize the soil, thirty-four soil samples from seven soil profiles were analyzed for their chemical and mineralogical composition at the laboratories of the Center for Soil and Agroclimate Research and Development. The results indicate that soils from the tidal flat areas have an aquic soil moisture regime, the upper parts of the soils are mostly ripe, and most of the pedons show the presence of sulfidic materials below 65 cm of the mineral soil surface. The soils are classified as Sulfic Endoaquept (P1, P2), Histic Sulfaquent (P3), Typic Sulfaquept (P4), Fluvaquentic Endoaquept (P5), and Sulfic Hydraquent (P6, P7). Mineral composition of the sand fraction is dominated by quartz, while the clay minerals consist of predominantly kaolinite, mixed with small amount of smectite, illite, quartz, and crystoballite. Organic carbon content is high to very high, potential phosphate content of most pedons ranges from very low to medium, while potential potassium content varies from very low to medium in the upper layers and medium to very high in the bottom layers. Phosphate retention of topsoil sample varies from 56 to 97%, and is positively correlated (r2 = 0.73) with aluminum from amorphous materials. Exchangeable cations are dominated by Mg cation, and in all pedons cation exchange capacity values are medium to very high, and seem to be influenced by organic carbon. Specific chemical properties, particularly soil pH and content of exchangeable aluminum exhibit a significant change about 1-2 months after soil samples were taken from the field. Theoretically, interaction between good water management and fertilizer application are among the choices of management to make these soils productive.

Ultisols are a major group of marginal soils extensively found in the upland area of Indonesia. To better understand the potential of the Ultisols developed from claystone and sandstone in the Sasamba Integrated Economical Development Area in East Kalimantan, chemical and mineralogical characteristics of 27 Ultisols pedons consisting of 76 topsoil and 118 subsoil samples were investigated. Besides analysis and interpretation of data, relationships of several soil characteristics were constructed using simple regression. The results indicated that Ultisols showed acid to very acid reaction, had low content of organic matter and low base saturation. Soils generally exhibited net negative charge, and the point of zero charge was reached at pH 3.6. Both potential and available phosphates were low, and there was a trend that amorphous aluminum was responsible for phosphate fixation. The low content of exchangeable potassium in topsoil and subsoil indicated a positive correlation with potential potassium. Clay mineral was composed chiefly of kaolinite, with small amounts of illite, vermiculite, and quartz. The domination of kaolinite and low organic matter content causes the soils to have low cation exchange capacity. Soil management in this area should be focused on building up and maintaining soil fertility, and applying appropriate soil conservation techniques to minimize erosion. To obtain sustained productivity, various soil amendments including the use of farm and/or green manure, liming with agricultural lime, and application of rock phosphate and K fertilizers were highly recommended.

Spodosols are problem soils due to coarse texture, acid soil reaction, low nutrient status, and low soil moisture retention. About 2.16 million ha of Spodosols (1.1% of the Indonesian land areas) distributed in lowland and highland areas in Kalimantan, Sumatra, Sulawesi, and Papua. Spodosols of the Toba highland areas require special attention because these forested lands are gradually cleared, but then abandoned because they are not suitable for agricultural development, causing land degradation. This study aimed to evaluate mineralogical and chemical characteristics of Toba highland Spodosols, North Sumatra, and their implication on agricultural development. Three pedons of the Toba highland Spodosols from Humbang Hasundutan regency were studied, consisted of soils developed from volcanic sand overlying liparite tuff under the influence of low temperature and high rainfall. Field observation was conducted in January 2008. Fifteen soil samples were collected from the three pedons based on the depth of soil horizon. Results indicated that the formation of these Spodosols were influenced by parent material, high elevation (1676-1821 m) above sea level), and by high amount of rainfall (2167 mm). The Spodosols in Toba highland were still in the early stage of development as characterized by shallow effective soil depth (22-23 cm), domination of weatherable minerals (39-81%) in the sand fraction and dominated by amorphous mineral as shown by sum of A1 + 1/2 Fe extracted by ammonium oxalate as much as 0.6-12.8%. The Spodosols were also characterized by coarse texture (66-95% sand fraction in E and B horizons), high organic-C content (1.4-37.7%), acid soil reaction (pH 3.7- 5.3), very high K2O in Oa horizon (552-933 mg kg-1) and B spodic or C horizon (812-2028 mg kg-1), and low base saturation (< 5%). The existence of biological processes in the surface layer was indicated by accumulation of exchangeable bases (0.88-1.14 cmolc kg-1 in Oa horizon and 0.09-0.25 cmolc kg-1 in B horizon), P2O5 (181-298 mg kg-1 in Oa horizon and 3-24 mg kg-1 in E horizon), and K2O (552-933 mg kg-1 in Oa horizon and 13- 30 mg kg-1 in E horizon). However, these nutrients were easily leached after deforestation. With the sandy texture, loose structure, and no vegetation cover, the erosion hazard is high in the deforested areas. Therefore, lands with Spodosols of the Toba highland, especially are not recommended for agricultural development, rather they should be kept as forest lands.

The properties of iron oxide concentrates of Oxisols and Alfisols on volcanic tuff in West Java, Indonesia, were studied by XRD,TGA, TEM and chemical analysis.Goethite and hematite are the co-dominant iron oxides and are present in all samples. Iron content of the soils (dithionite-soluble Fe) ranges from 6.0 to 15.4%. Aluminium substitution in goethite and hematite ranges between 11 and 26 mol% and 0 and 9 mol% respectively. The Al substitution in hematite increases at about half the rate for goethite within the same samples. Crystal size of goethite and hematite was measured from line broadening of the 110 reflections and ranges between 7 and 18 nm for goethite with a mean value of 10 nm and between 7 and 28 nm for hematite with a mean value of 18 nm. The dehydroxylation temperature of goethite is in the range 290-320 °C and is linearly related to Al substitution by the equation y = 280 + 1.53x, (R(2) = 0.53). The goethite and hematite in these Indonesian soils are very similar to these minerals in tropical and Mediterranean soils from other regions.

ABSTRAK Tanah berliat aktivitas rendah adalah salah satu tanah bermasalah di Indonesia. Jenis tanah ini meliputi tanah-tanah Ultisols, Oxisols, Alfisols, dan sebagian Inceptisols, mencakup sekitar 34,5% dari total daratan Indonesia, dan berkembang dari bahan induk yang beragam. Untuk mengevaluasi sifat-sifat tanah berliat aktivitas rendah, 6 pedon tanah (Oxisols dan Inceptisols) yang berkembang dari batu liat, batuan andesit, batuan ultra basis dan batu gamping, di daerah Kalimantan Selatan telah diteliti di lapangan maupun di laboratorium. Analisis laboratorium meliputi tekstur, kandungan bahan organic, pH (H2O dan KCl), P dan K potensial, ketersediaan P, retensi P, basa-basa dan kemasaman dapat tukar, kapasitas tukar kation, dan komposisi mineral. Hasil penelitian menunjukkan bahwa tanah berliat aktivitas rendah didominasi oleh mineral opak dan kuarsa sebagai mineral primer yang resisten. Fraksi liat didominasi oleh kaolinit, dan dalam jumlah yang jauh lebih sedikit dijumpai pula goethite, hematite, dan gibsit. Komposisi mineral dari tanah-tanah berliat aktivitas rendah mengindikasikan rendahnya cadangan sumber hara dalam tanah dan tingkat pelapukan tanah yang sudah lanjut. Dari sudut sifat kimianya, tanah-tanah berliat aktivitas rendah bersifat masam, mempunyai konsentrasi basa-basa dapat tukar dan kapasitas tukar kation yang rendah, serta mempunyai retensi fosfat dan kejenuhan aluminum yang tinggi. Pemupukan yang lengkap diperlukan untuk penggunaan yang berkelanjutan. Penambahan bahan organik lebih penting pada tanah berliat aktivitas rendah Oxisols bila dibanding Ultisols, tapi pengapuran lebih penting pada tanah berliat aktivitas rendah Ultisols. Walaupun kendala kesuburan tanah dapat diatasi dengan pengapuran dan pemupukan yang lengkap, kondisi sosial ekonomi dari petani masih merupakan kendala tersendiri. ABSTRACT Soils with low activity clay is one of the problem soils in Indonesia. These soils consisted of Ultisols, Oxisols, Alfisols, and some Inceptisols, occupied about 34.5% of total Indonesian land, distributed in almost all Indonesian islands, and derived from various parent materials. To evaluate the properties of low activity clay soils, 6 pedons of Oxisols and Inceptisols, derived from clay stone, andesitic rock, ultra mafic rock and lime stone, from South Kalimantan were studied both in the field and in the laboratory. The analyses consisted of texture, organic carbon content, pH (H2O and KCl), potential P and K, available P, P retention, exchangeable bases and acidity, cation exchange capacity and mineralogical composition. The results showed that low activity clay dominated by opaque and quartz as primarily resistant mineral. Clay fraction was dominated by kaolinite, and to a lesser extent goethite, hematite, and gibbsite were also present. The mineralogical composition of the low activity soils indicated a low natural potential nutrient reserve and an advanced stage of soil weathering. Chemically, the low activity clay soils were acid, low content of bases, low cation exchange capacity, high P retention, and some of them show a high aluminum saturation. A complete fertilizer application is necessary for a sustainable use. Although soil fertility constraints on the low activity clay soils can be corrected by liming and appropriate fertilization, socioeconomic condition of the local farmer is another constraint.