Judul: The characteristics of paddy soils at the toposequence with volcanic parent material in Bogor – Jakarta area
Abstrak: The aims of the research were: (1) to study the characteristics and genesis of paddy soils at the toposequence with volcanic parent materials in Bogor . Jakarta area, (2) to study the influence of paddy cultivation intensity on the formation of surface gley, plow pan, Fe and Mn layer, (3) to study the movement of Fe and Mn soil, and (4) to study the mineralogy and classification of the soils. Twelve pedons, selected based on: (1) soils subgroup, and (2) cultivation intensity were investigated. Soil sample were collected from each horizon of the pedons for laboratory analysis. The result of the research shows that the morphology, the non-paddy soils consists only of tillage layer and the original soil layer. The once paddy a year soils, besides the tillage layer, show further horizonisation, including less visible plow pan layer (bulk density slightly higher than the tillage layer), Fe accumulation and Mn accumulation layer, and the original soil layer; meanwhile, the horizon of the twice a year paddy soils are as follows: more visible reduced tillage layer (chroma three month after harvesting . 2), more visible plow pan layer (bulk density clearly higher than the tillage layer above it and the layer below it, and permeability and porosity lower), Fe and/or Mn accumulation layer, and the original soil layer. At higher elevation (Yellowish Brown and Brown Latosols), both the once a year and twice a year of paddy soils, the plow pan layer was found at a shallower depth (10 . 12 cm), while at the lower elevation (Reddish Brown and Red Latosols) it was found deeper (15 . 16 cm), with similar thickness (12 . 19 cm). At higher elevation (Yellowish Brown Latosols), Mn accumulation layer were thicker (72 - 86 cm) than at lower elevation, and in Reddish Brown Latosols (42 - 46 cm). The color of tillage layer of paddy soils is lighter than the lower layer. At harvesting time the chroma 0, three month after harvesting chroma 2, but one year after harvesting if not rice cultivated the colors approach to the original soils colors. The consistence of the tillage layer after harvesting (wet) were very sticky and very plastic, at one to three month no rice cultivation still slightly sticky, but after six to nine month becoming friable to very friable. The pedogenesis processes of paddy soils were Fe/Mn elluviation of tillage layer Fe/Mn illuviation in the lower depth. This indicated by Fed, Feo, and Fep, or Mnd, Mno, and Mnp, and the quantity of Fe or Mn mottles. The tillage layer of paddy soils contain higher weatherable minerals than non-paddy soils, due to mineral materials containing in the irrigation water or mineral material erupted from surrounding volcanoes. In the tillage layer of non-paddy soils, there were processes enrichment, decomposition, lessivage, and leusinization. But of in the paddy soils there were also elluviation and gleyzation. The soil that are regularly cultivated with paddy, there are changes in soil classification, e.i. Typic subgroup of the non paddy soils changes into Aquic subgroup in the once/year paddy soils, and Aquic suborder
Keyword: tillage layer, plow pan layer, manganese layer, iron layer, West Java

Judul: Perkembangan, klasifikasi dan potensi tanah sawah tadah hujan dari bahan lakustrin di Paguyaman, Gorontalo
Abstrak: Efforts to increase and develop paddy soil other than irrigated paddy soil (IPS) are essential in order to improve rice production. Rainfed paddy soil (RPS) is the second granary national after IPS, although current productivity of RPS is low and it has complex limiting factor. The objective of this research were: (1) to study the development of RPS based on soil characteristics and genesis, (2) to identify the main factors influencing the formation of soil profiles, (3) to classify the soil according to Soil Taxonomy classification system, and (4) to evaluate land potency for rice and corn. The research was carried out on 9 pedons from lacustrine materials on E4 agroclimate zones. RPS and upland (UL) pedons are located in Sidomukti of Gorontalo Regency and Molombulahe of Boalemo Regency. While, the IPS pedon are Bandungrejo of Gorontalo Regency. Field observations were done throughout toposequent transect on the lower, middle and upper slope position. Soil samples taken from each horizon of each pedon for laboratory analysis. The observed parameters were morphological characteristics, physical, chemical and mineralogical properties of the soil. The data were analyzed with quantitative and qualitative analysis. Soils were classified based on Soil Taxonomy system, whereas land potentials were evaluate by land suitability analysis with the parametric approach. Land suitability classes (LSC) were determined by Square Root Land Index Method. The results of this study showed that all pedons have B horizon but IPS is more developed than the RPS and the UL. The IPS pedon is more weathered intensively than the RPS and the UL. The main genesis process in all pedon were eluviation, illuviation, lessivage, pedoturbation, braunification and gleization, except for UL pedon from Molombulahe that do not reflact gleization process. The main factors of soil formation were climate, age (time), topography and human activity. The soil classification of PNS1, PNM1 and PNM2 pedon were classified as Ustic Endoaquert, fine, smectitic, isohypertermic; PNS2 pedon classified as Vertic Endoaquept, fine, smectitic, isohypertermic; PNS3 pedon classified as Vertic Epiaquept, fine, smectitic, isohypertermic; PNS-LK pedon classified as Typic Eutrudept, fine loam, smectitic, isohypertermic; PNB pedon classified as Ustic Epiaquert, fine, mixed, active, isohypertermic; PNM3 pedon classified as Aeric Epiaquept, fine, smectitic, isohypertermic; and PNM-LK pedon classified as Typic Eutrudept, fine, smectitic, isohypertermic. The highest LSC of land utilization types (LUT) for local paddy was highly suitable (S1), while the lowest one was not suitable (Nna). The highest LCS of paddy-corn and paddy-corn-corn LUTs was marginally suitable with nutrient availability and water as a limiting factor (S3na and S3wa), while the lowest LSC was not suitable cause same limiting factors (Nna and Nwa). The potency of RPS similar to potency of IPS. The full recommendation of LUT were LUT of local paddy with B (100% of recommended dosage) and C pattern (prescription dosage), except for Inceptisol from Molombulahe consist of local paddy LUT to A (none fertilizing), B and C pattern. The Other LUTs were including requiring recommended and not recommended.
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Judul: Konstruksi aritmetika kurva eliptik F(2m) supersingular dan non-supersingular untuk skema kunci publik ElGamal
Abstrak: Algoritme ElGamal adalah salah satu algoritme kunci publik dengan aritmetik modular p yang mempunyai struktur grip siklik Z(p). Tingkat keanaman algoritme ini terletak pada pemecahan masalah logaritme diskret dari Z(p). Akan tetapi, tingkat keamanan tadi tahun ke tahun semakin menurun yang disebabkan kemampuan pemecahan algoritme diskret semakin meningkat. Untuk memenuhi tingkat keamanan yang memadai dibutuhkan p yang cukup besar yang menyebabkan proses enkripsi dan dekripsi menjadi lambat.
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