Judul: Keterkaitan Sifat Tanah Gambut Terhadap Konsentrasi Hara dan Keragaman Mikrob Serta Makrofauna Tanah di Areal Penanaman Sagu
Abstrak: Indonesia has the largest peat land among tropical countries, about 21 million ha are scattered mainly in Sumatra, Kalimantan and Papua. Spread of peatlands in Indonesia's main islands, only about 6 million hectares are used for agriculture viable. It is associated with the utilization of peat which had many obstacles especially in peatlands that have not experienced further weathering. The one of the natural resources are not optimally managed sago palm (Metroxylon spp). Sago as one of the plants native to Indonesia which is a commodity that has a very good development prospects for the future, in addition to the sago plant has the ability to grow in marginal lands. One of the inputs required by the land associated with land productivity on farm land is soil organic matter and nutrients are available in a number of balanced. Soil microorganisms and organism play an important role in accelerating the supply of nutrients and also as a source of soil organic matter. Among groups of soil microbes, bacteria and fungi are the most likely group to attention. The role of bacteria in the recycling of nutrients such as carbon, nitrogen and phosphorus are very important. The purpose of this study was to examine the relationship between peat soil characteristics associated with plant nutrients and microbial diversity and macrofauna in a sago plantation. The area is used as a plot observations is to consider the different types of land management, the land cover types in the area of community cultivation, sago plantations in the area PT.NSP and sago plantations in the area of PT. NSP on fire. Based on the research results revealed that the highest nutrient content of K is in sago plantations in the area of PT. NSP on fire > community cultivation > sago plantations in the area PT.NSP, while the highest calcium content contained in sago plantations in the area PT.NSP > community cultivation > is in sago plantations in the area of PT. NSP on fire. Relationship between the availability of potassium in the soil with the availability of potassium in leaves and rachis showing a positive relationship between the availability of potassium in the soil with potassium content in the rachis. While the availability of calcium and magnesium in the soil did not show a positive relationship. In this research shown that the physical condition of the environment, that is water table depth pf peat and C/N ratio contribute impact on microbial diversity and macrofauna. The highest microbial and macrofauna diversities was found in community sago cultivation area with peat water table depth of 63.33 cm and content of C/N ratio of 56.12%.
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Judul: Variability of Some Physical and Chemical Properties of Peat  Based on Distance from River and Peat Depth
Abstrak: Pemanfaatan lahan gambut menjadi lahan pertanian harus dilakukan dengan baik dan bijaksana. Hal ini disebabkan banyaknya faktor penghambat yang dimiliki oleh lahan gambut seperti produktivitas lahan yang semakin rendah seiring dengan bertambahnya ketebalan gambut dan rendahnya kesuburan alami tanah. Sifat fisik dan kimia gambut sangat penting untuk pengelolaan produktivitas tanaman dalam kaitannya dengan jarak dari sungai dan kedalaman pengambilan contoh. Penelitian ini bertujuan untuk mempelajari hubungan antara sifat fisik dan kimia gambut di perkebunan kelapa sawit di Kabupaten Labuhanbatu, Provinsi Sumatera Utara berdasarkan jarak dari sungai dan kedalaman. Pengambilan contoh gambut dilakukan pada transek hidrosekuen dari Sungai Leidong sebanyak 10 titik contoh. Setiap titik berjarak sekitar 300 m dari titik lainnya dan pada setiap titik diambil contoh gambut pada kedalaman 0-50 cm dan 50-100 cm. Analisis bobot isi, porositas, pH, C-organik, KTK, N-total, P-tersedia, P-total dilakukan pada setiap contoh. Perbedaan jarak dari sungai tidak berpengaruh pada bobot isi dan porositas gambut. Sebaliknya, contoh yang lebih dalam nyata memiliki bobot isi yang lebih rendah dan porositas yang lebih tinggi. Jarak yang jauh dari sungai nyata memiliki pH yang lebih rendah. Jarak dari sungai dan kedalaman contoh tidak mempengaruhi C-organik, KTK, N-total, P-total, dan P-tersedia gambut. Studi ini menunjukkan bahwa perlu dilakukan penelitian lebih detil untuk mengetahui pengaruh jarak dari sungai, kedalaman gambut dan pengaruh antropogenik terhadap pengelolaan produktivitas gambut., The utilization of peatlands for agriculture must be coducted properly and wisely. This is due to the many inhibiting factors possessed by peatlands such as lower land productivity along with increasing peat thickness and low natural fertility of the soil. The study of peat physical and chemical properties are very important for management of plant productivity in relation with the distance from the rivers and depth of samples. This study was aimed to examine the relationship between physical and chemical properties of peat in oil palm plantation in Labuhanbatu Regency, North Sumatra Province based on the distance from the river and the depth of sampling. Ten peat sampling points were carried out according to hydro sequence transect from the Leidong River. Each point was about 300 m apart from one another, and at each point peat samples were taken at depths of 0-50 cm and 50-100 cm. Analysis of bulk density, porosity, pH, organik-C, CEC, total-N, total-P, available-P was carried out on each sample. The difference of the distance from the river had no effect on the peat bulk density and porosity. On the other hand, deeper samples had lower bulk density and higher porosity. More distance from the river had lower pH. The distance from the river and depth of samples did not affect peat organik-C, CEC, total-N, total-P, and available-P. This study showed that a more detailed research is needed to determine the effect of distance from river, peat depth, and anthropogenic affect on peat productivity.
Keyword: bulk density, hydrosequence transect, oil palm, pH, porosity

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. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular