Judul: Formulasi spora Bacillus Subtilis sebagai agens hayati dan PGPR [Plant Growth Promoting Rhizobacteria] pada berbagai bahan pembawa
Abstrak: Penelitian ini bertujuan untuk menguji pengaruh formulasi spora B. subtilis pada berbagai bahan pembawa terhadap viabilitas dan keefektifannya sebagai agens hayati dan PGPR. Penelitian dilaksanakan di Laboratorium Bakteriologi Tumbuhan Departemen Proteksi Tanaman Fakultas Pertanian Institut Pertanian Bogor mulai Februari hingga Juli 2009. Biakan B. subtilis yang digunakan didapat dari koleksi biakan bakteri yang terdapat di laboratorium Bakteriologi Tumbuhan Departemen Proteksi Tanaman Fakultas Pertanian Institut Pertanian Bogor. Formulasi yang digunakan merupakan formulasi dalam bentuk tepung, dimana bahan pembawa yang digunakan adalah tepung beras (TB), tepung singkong (TS), tepung jagung (TJ), talek (T), bentonit (B), dan tepung campuran (C) yang terdiri dari tepung singkong, tepung jagung, tepung udang, zeolit, dan dedak halus. Spora B. subtilis mampu bertahan secara optimal pada formulasi campuran (C). Pada uji keefektifan terhadap penekanan populasi patogen penyebab peyakit hawar daun bakteri pada benih padi, perlakuan dengan menggunakan formulasi tidak efektif dalam menekan populasi X. oryzae. Pengujian formulasi spora B. subtilis sebagai PGPR pada benih padi menunjukkan kefektifannya dalam memacu pertumbuhan panjang akar dan panjang tajuk.
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Judul: Studi Keefektifan Formulasi Spora Bacillus Subtilis Sebagai Agens Pengendali Hayati Penyakit Hawar Daun Bakteri dan Hawar Pelepah Serta Pemicu Pertumbuhan Pada tTanaman Padi:
Abstrak: In controlling rice diseases, most farmers still rely on chemical pesticide as the solution. However, because of high cost and negative effects of chemical pesticide, biocontrol is one of alternative solutions. Bacillus subtilis is a model of biocontrol agents to control many plant diseases, because its ability to produce antimicrobial and plant growth promoting substances. This research aimed to examine the effectiveness of Indonesian isolate of B. subtilis spore formulation through seed treatment and foliar spray with different frequencies and concentrations to control bacterial leaf blight (Xanthomonas oryzae pv. oryzae) and sheath blight (Rhizoctonia solani) diseases of rice. The influence of the formulation application to plant growth and other microbes was evaluated. The experiment was conducted in greenhouse and field with factorial experimental design. Seed treatment, concentration and frequency of application and its interaction effectively suppressed bacterial leaf blight and sheath blight diseases, increased plant growth and reduced yield loss. The concentration at 2% is recommended for applying the formulation. The interval of application at 1 and 2 week showed equal effect to disease suppression and increased yield. Application of B. subtilis spore formulation increased yield of Ciherang, Cisantana, and Sintanur as much as 26,3%, 18,5%, and 15,4% respectively. Application of the formulation gave no significant effect to microbe diversity in the field.
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Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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