Genesis and Properties of Peat at Toba Highland Area of North Sumatra

Abstract

In Indonesia, peat soil in the highland area is only found in the plateau of Toba Highland, North Sumatra, and its morphologi-cal, physical, and chemical properties have been studied. Four profiles of peat soil were made in the field and eighteen samples were taken and analyzed in laboratory. Most of the properties of highland peat were similar with lowland peat. The differences were in their Al saturation, P retention, and andic soil properties. High Al saturation was resulted from weathering of primary minerals under the acid condition. Andic soil properties were caused by amorphous materials resulted from weathering of volcanic materials in the peat, and P retention was related with the presence of amorphous materials. Phosphate retention of the highland peat was classified high (>60%) and positively correlated with amorphous materials. The presence of amor-phous materials was confirmed by ammonium oxalate extract-able Alo+½Feo. The presence of andic soil properties in the highland peat created problem in their classification. To provide a place for andic soil properties that influence the P retention in the highland peat soil, the soil classification of peat soil should be modified by adding andic modifier at subgroup level. <br /><br />

Distribution of soil minerals along the toposequence of Hyang-Argopuro Volcanic Mountain, Jember, Indonesia

“…The high NaF-pH and low H2O-pH also point to the Andisol origin of this soil. Prasetyo et al (2009) argued that the low allophane in soils was due to the development of the soil and the desilification process so that the allophane content was reduced and formed halloysite hydrate crystalline minerals. The halloysite of 10 Å is found only on the Bw2 horizon in soil profile 1, while the halloysite with 7 Å diffraction peak is the one found in the Ah horizons of soil profiles 1 and 2.…”

“…Cristobalite is a silica (SiO2) mineral member, while gibbsite is an aluminum hydroxide mineral (Al(OH3)). Gibbsite can be formed directly through the weathering of primary minerals (Wada and Aomine, 1966;Prasetyo et al, 2009). Cristobalite can be known through XRD analysis with diffraction peaks of 4.26 and 3.34 Å. Gibbsite displays a diffraction peak of 4.82 Å. Interestingly, illite (10 Å) is present in few to moderate amounts in all soil profiles and tends to increase with soil depth.…”

Analysis of degraded land suitability and regional comparative advantages for maize development in the Gorontalo sustainable agriculture areas, Indonesia

“…This was presumably because it is influenced by the parent material in each soil unit (pedon). The nature and characterization of soils were shown to be strongly influenced by the parent material (Prasetyo, 2007;Suharta, 2007). The analysis results showed that the soil erosion rate of maize plantings was dominated by moderate, heavy, and very heavy categories, with an area percentage of 80.14%, as shown in Table 5 and Figure 2.…”