Judul: Uji Efektivitas Pupuk Organik Hayati (Bio-Organic Fertilizer) dalam Mensubstitusi Kebutuhan Pupuk pada Tanaman Caisin (Brassica chinensis)
Abstrak: Currently, there are several factors which stimulate the increase of attention toward application of bio-organic fertilizer which is based on local raw materials in Indonesia. One of the factors is energy crisis which caused increasing price of fertilizer-raw materials, so that the producers were not able to fulfill the domestic demand for fertilizer. Therefore, the fertilizer price increased progressively, causing subsidy of fertilizers threefold increased. Beside that, there is also a growing awareness toward the potency of environmental pollution due to excessive and inefficient use of inorganic fertilizer.
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Judul: Substitusi Sebagian Pupuk Kimia dengan Pupuk Organik Hayati dan Pupuk Hayati pada Caisim (Brassica juncea L.).
Abstrak: Penggunaan pupuk kimia secara terus menerus menyebabkan kerusakan pada tanah dan lingkungan. Hal ini disebabkan oleh penggunaannya yang tidak efisien, dosis yang berlebihan, dan tidak mengembalikan bahan organik ke dalam tanah. Pupuk organik hayati dan pupuk hayati mengandung mikrob fungsional yang mampu memperbaiki sifat-sifat tanah dan memacu pertumbuhan tanaman. Penelitian ini bertujuan untuk mempelajari pemberian pupuk organik hayati (POH) dan pupuk hayati (Biofertilizer) dalam menggantikan sebagian kebutuhan pupuk kimia, serta pengaruhnya terhadap pertumbuhan caisim. Percobaan lapangan dilakukan di University Farm Pasir Kuda IPB, Kelurahan Pasirkuda, Kecamatan Bogor Barat, Kota Bogor. Analisis laboratorium biologi dan kimia tanah dilakukan di Laboratorium Bioteknologi Tanah dan Lingkungan serta Laboratorium Kimia dan Kesuburan Tanah, Departemen Ilmu Tanah dan Sumberdaya Lahan, Fakultas Pertanian IPB. Penelitian dilaksanakan pada bulan September 2017 - Februari 2018. Perlakuan pemupukan terdiri dari 8 perlakuan dengan 4 ulangan, sehingga terdapat 32 satuan percobaan. Perlakuan pemupukan tersebut ialah P1 (POH), P2 (Biofertilizer), P3 (0,5 NPK), P4 (0,5 NPK + POH), P5 (0,5 NPK + Biofertilizer), P6 (1,0 NPK), P7 (1,0 NPK + POH), dan P8 (1,0 NPK + Biofertilizer). Rancangan percobaan menggunakan Rancangan Acak Lengkap (RAL). Sebagai media tanam digunakan bahan Latosol dari University Farm Pasir Kuda IPB, Kelurahan Pasir Kuda, Kecamatan Bogor Barat, Kota Bogor. Caisim varietas Tosakan digunakan sebagai tanaman indikator. Pemanenan dilakukan pada umur 28 hari setelah tanam. Hasil penelitian menunjukkan bahwa pemberian pupuk 0,5 NPK + POH dan 0,5 NPK + Biofertilizer mampu mensubstitusi setengah takaran pupuk kimia (N,P,K) dan pemberian pupuk 0,5 NPK + POH dan 0,5 NPK + Biofertilizer mampu meningkatkan pertumbuhan caisim setara dengan pemberian pupuk 1,0 NPK, 1,0 NPK + POH, serta 1,0 NPK + Biofertilizer.
Keyword: pupuk organik hayati, pupuk hayati, pupuk NPK, caisim

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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