Judul: Pengaruh Pemberian Abu Volkanik Gunung Kelud Letusan Tahun 2014 terhadap Produksi dan Efisiensi Pemupukan Kedelai.
Abstrak: Indonesia has many volcanoes that their material eruption causing rejuvenation of soil forming process and renew long term soil fertility. One of volcanoes in Indonesia is Kelud Mountain*. This research is to investigate the effect of Kelud Mt. volcanic ash application on soybean growth and yield efficiency. The pot experiment was carried out in poor-very acid Inceptisol soil. The ash was dominated by fine size particles (<100 μm). Based on total chemical analysis, Kelud volcanic ash was intermediet material in composition that consisted of SiO2, Al2O3, CaO, Fe2O3, Na2O, MgO, K2O, TiO2, SO3, P2O5, MnO, SrO, ZrO2, Cr2O3, ZnO and CuO. The field experiment conducted in randomize factorial block design with combination of four doses of volcanic ash (0, 10, 20, and 30% of w/w), and three doses of fertilizers (0, 50, and 100% of NPK recommendation doses), in five replication. The result showed that fertilizer application was not significant effect to all variables. In other side, Kelud volcanic ash addition had significant effect to nutrients uptake of P, K, and Ca, and was very significant effect to upper bio mass, amount of pods, pods weight, yield, and nutrient uptake of N and Mg. The treatment that was the highest effect was of application 30% volcano ash of doses treatment. Higher volcanic ash rates higher P and K fertilizer efficiency.
Keyword: volcanic ash, Kelud Mt, soybean, fertilizer efficiency, Inceptisol

Judul: Efektivitas Amelioran Abu Vulkanik Merapi dalam Mengubah Sifat Kimia Tanah Ultisol dan Pertumbuhan Kedelai
Abstrak: This research was carried out to study the effect of Merapi volcanic ash in improving chemical properties of Ultisol soil and its influence on the growth and production of soybean. The volcanic ash largely consist of minerals, such as glass volkan, labradorite, augite, bitownite, hiperstine, and hornblende with high total composition elements including Ca, Na, K and Mg that are potential to increase reserves of minerals, enrich chemical composition and physical properties of soil. The volcano ash was given on the Ultisol soil which is infertile. In this work, amelioran volcanic ash was applied at dosage of 0; 2.5; 5; 10; 20; and 40 t/ha. The result showed that the addition of Merapi volcanic ash did not increase the soil pH. However, the higher the dose of the applied volcanic ash the higher the value of Cation Exchange (K, Ca, and Mg) and Cation Exchange Capacity gained. In addition, the volcanic ash can reduce the acidity (Aldd and Hdd) of Ultisol soil. Plant tissue analysis showed that most of the N, P, and K nutrients were present in soybeans, while most of the Ca and Mg were in the leaves with the highest nutrient uptake in a dose of 20 t/ha. Merapi volcanic ash application can increase plant height, leaf number, and soybean yields with the best dose of 20 t/ha.
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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