Judul: Formulasi campuran rizobakteria pelarut fosfat dengan Bradyrhizobium japonicum menggunakan gambut sebagai bahan pembawa
Abstrak: Pertanian modern sangat bergantung pada penggunaan bahan-bahan kimia pada pupuk dan pestisida untuk meningkatkan hasil panen. Namun, saat ini telah berkembang pemanfaatan Plant Growth Promoting Rhizobacteria (PGPR) seperti rizobakteria pelarut fosfat dan bakteri penambat nitrogen Bradyrhizobium japonicum. Penelitian ini bertujuan mendapatkan formulasi terbaik campuran rhizobateria pelarut fosfat dengan Bradyrhizobium japonicum dengan menggunakan media produksi yang tepat dan dikemas dengan bahan pembawa gambut. Sebanyak 8 isolat Pseudomonas spp. (Crb), 10 isolat Bacillus spp. (Cr) dan 3 isolat Bradyrhizobium japonicum (BJ) diuji antagonistik.Isolat yang tidak saling antagonis diformulasi menjadi pupuk hayati menggunakan media alternatif terbaik. Tiga jenis media alternatif yang diuji, yaitu media susu skim, media Potato Dextrose Broth, dan media terasi. Gambut yang digunakan sebagai bahan pembawa (karier) dikemas masing-masing sebanyak 50g dan disterilisasi 2 kali. Inokulasi tiap suspensi isolat ke karier dilakukan secara akseptik yang selanjutnya disimpan pada suhu ruang dalam 5 masa simpan, yaitu 0, 2, 4, 6,dan 8 minggu serta dihitung konsentrasi sel bakteri setiap 2 minggu sekali. Dari uji kompatibilitas bakteri, didapatkan 10 paket formula yang tiap paketnya mengandung 4 ml Pseudomonas, 4 ml Bacillus, dan 4 ml B. Japonicum yang tidak saling antagonis yang dikulturkan pada media alternatif terbaik untuk produksi isolat, yaitu media susu skim kemudian dicampur dengan gambut dan menghasilkan viabilitas konsentrasi sel sekitar 108-109sel/gram selama 8 minggu masa penyimpanan
Keyword: Pseudomonas spp, Bacillus spp, Plant growth, Bogor Agricultural University, Institut Pertanian Bogor, IPB

Judul: Formulasi Konsorsium Rizobakteria Pelarut Fosfat dengan Bradyrhizobium japonicum sebagai Pupuk Hayati dan Aplikasinya pada Tanaman Kedelai
Abstrak: Phosphate solubilizing rhizobacteria were known for their ability to convert insoluble form of phosphate to the accessible form. The use of rhizobacteria as biofertilizer is one of the most promising biotechnologies to improve plant production. This study was conducted to formulate phosphate solubilizing rhizobacteria (Bacillus sp. Cr and Pseudomonas sp. Crb) coinoculated with Bradyrhizobium japonicum (Bj) and appliance them to soybean plant as biofertilizer. Pikovskaya medium containing tri-calcium phosphate at concentration of 0.5% was used to measure P-solubilizing ability of tested strains. Results revealed that Crb1 is the most powerful P-solublizer using tricalcium phosphate as a P source. It was also observed decreasing in pH along with the increasing of amount of soluble P ranged from -0.96 to -0.42 from initial culture during 72 hours. Isolates of the rhizobacteria (Crb and Cr) were grown in media containing skim milk and molases prior to formulation in peat as a carrier material. The combination of three strains produced 4 packages of inoculants. Each packages was tested for their viability and effectiveness on soybeans in the field. The number of bacterial population after 9 months of storage ranged from 7.5 x 106 to 5.8 x 108 cfu gr-1 of peats. Field experiment showed that treatments designed as F1+NPK and F3+NPK were significantly increased soybean plant growth and mineral uptake compared to untreated control and better than NPK treatment. While F1+NPK and F2+NPK were able to increase soybean productivity.
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Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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