Judul: Pengaruh Pirit Terhadap Sifat Kimia Tanah Serta Produksi Tanaman Kelapa Sawit (E. guineensis)
Abstrak: Development of oil palm plantation areas in Indonesia has significantly increased every years. This makes the development leads to marginal lands, like the lands acid sulfate soil which has sulfidic material. The expansion of the plantation into the marginal lands, is not an expected alternative, but the suitable lands were limited. Oxidation of pyritic material in aerobic condition will produce sulfuric acid and mineral jarosit with extreme acidity that can prohibit plant growth. The conditions is obtained due to land reclaimation through establishment of drainage facilities. On the other hand, large amounts of plant nutrients washed out from the lands. The leaching are more conducive in high acidity drainage water. Ultimately this processes are reducing soil fertility with low soil pH as well. The study aims to determine the effect of different depths of pyritic material and pyrite oxidation on soil chemical properties and oil palm production. Location of soil sampling and observations conducted in the oil palm plantation Business Unit Bentayan and Betung Krawo, PT Perkebunan Nusantara VII (Persero), South Sumatra. Analysis of soil samples carried out at the Laboratory of Department of Soil Science and Land Resources, Faculty of Agriculture, Bogor Agricultural University. Observations focused on the depth pyritic material at <30 cm, 30-60 cm, and > 60 cm, and not containing pyritic material. Special observation conducted on soil chemical properties at the soil with and without oxidation. The results show that the content of pyrite at depths <30 cm have a significant effect on increasing soil acidity and exchangeable aluminum content (Al-dd), and reduced levels of N-total nutrients, potassium (K) and production of fresh tube fruits. Oxidation pyrite also gives a tendency of decreased levels of available nutrients phosphorus (P), calcium (Ca), magnesium (Mg), and base saturation. Pyritic lands which have undergone an oxidation process tended to decrease fertility.
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Judul: Pengaruh Kedalaman Muka Air Tanah dan Dosis Terak Baja terhadap Hidrofobisitas Tanah Gambut, Emisi Karbon, dan Produksi Kelapa Sawit
Abstrak: Development of oil palm plantation requires drainage to support growth and production of the oil palm. The excessive drainage would cause the peat dryness of as well as hydrophobicity and thus decreasing its capacity to retent water, soil infiltration, surface erossion. It can limit oil palm growth. The application of water management and soil amandment must be performed to avoid the decrease of peat soil quality and to improve the productivity of oil palm. This series research was designed to: 1) evaluate the peat soil hydrophobicity under oil palm plantation area, 2) study the effect of the ground water level depth and stell slag dose on the peat soil hydrophobicity and other soil physical changes, 3) study the effect of the ground water level depth and the steel slag dose on CO2 emission from peat soil, and 4) study the effect of ground water level depth and steel slag dose on the growth and production of oil palm. The first study has utilized sapric and hemic peat soil samples taken from the 6-year Panai Jaya Oil Palm Plantation (PAJ) and the 20-year Meranti Paham Oil Palm Plantation (MEP). Peat soil samples were heated at a temperature of 50°C with a time interval and the effects on hydrophobicity were recorded. Hydrophobicity of the peat soil was evaluated by Water Drop Penetration Time (WDPT) method. After the hydrophobicity of all peat soil samples had been observed, a number of soil properties, including soil water content (SWC), total acidity, carboxylic content (COOH) and phenolic-OH were then analyzed. Critical water content (CWC) of the peat soil. The point at which hydrophobicity occurred, was determined using exponential relationship between soil water content and the probability of the occurrence of soil hydrophobicity, the point at which the probability of the occurrence of hydrophobicity was between 60% and 80%. Fourier Transform Infra Red (FTIR) spectrometer was used to evaluate peat soil hydrophobicity by knowing the functional groups in peat soil. The second experiment was carried out in laboratory by application of various steel slag level (0; 7.17; 14.81; dan 22.44 g pot-1) on two peat type (sapric dan hemic) with two soil moisture conditions including wet and dry (hydrophobic). Peat soil samples that has been added with steel slag incubation for 60 days and observation of soil properties, FTIR analysis, and wettability by WDPT method. The field experiment was carried out in 6 years-oil palm block of PAJ. Research plots was designed using a split plot design with three replications. Plots treated with three treatments of ground water level (MAT-1, MAT-2, and MAT-3) as main plots and four level of steel slag application (0; 3.15; 6.51; 9.86 kg pohon-1) as a subplot. MAT-1 is ground water level (GWL) at depths of 30-50 cm, MAT-2 is GWL at depths of 60-75 cm, and WLM-3 is GWL at depths 70-90 cm below the soil surface. The research observation consists actual soil water content, actual v hydrophobicity, oil palm growth and production, subsidence, and accumulation of heavy metals in fruit. The results shown that hydrophobicity of peat soil in this study was
Keyword: CO2 emission, hydrophobicity, oil palm, peat soil, steel slag

Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh.
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. ,,,
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular.