Judul: Efektivitas Bakteri Metanotrof dan Bakteri Pereduksi N2O sebagai Pupuk Hayati pada Pertumbuhan Padi di Sawah Organik
Abstrak: Paddy fields are one of the methane (CH4) and nitrous oxide (N2O) emission sources. Methanotrophic bacteria have high activity in the oxidation of methane and denitrification bacteria also have high activity in N2O reduction respectively. Both types of bacteria have ability of fixing nitrogen and controlling emissions of CH4 and N2O from paddy fields. This research was conducted to test the effectivity of methanotrophic bacteria (BGM 1, BGM 5, BGM 9, and SKM 14), two isolates of Ochrobactrum anthropi (BL 1 and BL 2), and Azotobacter sp. and Azospirillum sp. bacteria on the paddy growth in organic rice cultivation. The experimental result showed that paddy growth (Ciherang) which is inoculated by the mixture of four types of bacteria isolates give the better value of growth indicated by some parameters such as number of tillers, plant height, biomass, and total N content than the paddy growth which is given only by compost fertilizer.
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Judul: Kombinasi Bakteri Metanotrof, Pereduksi Dinitrogen Oksida, dan Penambat Nitrogen sebagai Agen Pereduksi Gas Rumah Kaca dan Pupuk Hayati pada Tanaman Padi
Abstrak: High CH4 oxidation activity was found in methanotrophic bacteria (BGM 1, BGM 5, BGM 9, and SKM 14) isolated from paddy fields in Bogor and Sukabumi. Other bacteria, BL1 and BL2, are denitrifier that possess high N2O reduction activity. Those isolates combined with nitrogen (N2) fixing bacteria (Azotobacter sp. and Azospirillum sp.) could be used as biofertilizer to reduce CH4 and N2O emissions and enhance paddy’s growth. The objective of this research was to evaluate the effectiveness of those bacterial combinations as biofertilizer and greenhouse gases reducing agent in paddy. This research was consisted of two experiments. The 1st experiment was arranged in a completely randomized design (CRD) with four replicates and consisted of fertilizer types (inorganic and bacteria) and watering system (submerged and periodically intermittent) treatments. The 2nd experiment was arranged in CRD with four replicates that consisted of bacterial fertilizer types, types of inorganic fertilizer dosages, and watering system factor (submerged and periodically intermittent). The result of the 1st experiment showed that the plant height was not affected by the treatment. Plant fresh weight, dry weight, number of productive tiller, grain per panicle were affected by type of fertilizer. Inorganic fertilizer increased CH4 flux and bacterial fertilizer reduced CH4 flux from paddy field. The best reduction of CH4 flux achieved by bacterial fertilizer contained BGM 1 and BGM 5 isolates. The result of the 2nd experiment showed that combination of BGM 5 – BGM 9 isolates and N2 fixing bacteria enhanced paddy vegetative and generative growth under N fertilizer with the dosage of 166.67 or 250 kg/ha. There was no clear pattern in the CH4 and N2O flux reduction from paddy under bacterial fertilizer application. In general, methanotrophic bacteria and N2O reducing bacteria isolates could reduce CH4 and N2O flux in certain dosage of inorganic fertilizer. In addition, CH4 flux was decreased and N2O flux was increased in periodically intermittent condition.
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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