Judul: Efektivitas Isolat Rhizobium Dalam Meningkatkan Pertumbuhan Semai Akasia (Acacia Crassicarpa A. Cunn. Ex Benth)
Abstrak: Dalam kurun waktu 20 tahun terakhir, HTI Pulp telah berkembang dengan pesat. Pada tahun 2002, HTI Pulp tercatat mempunyai luas sebesar 1.3 ha. Spesies-spesies tanaman HTI Pulp yang sering ditanam merupakan tanaman yang mampu tumbuh cepat seperti Acacia cracicarpa dan A. Mangium. Adapun salah satu faktor terpenting yang menentukan kesuksesan program HTI Pulp yaitu ketersediaan bibit akasia yang sehat. Oleh karena itu, penggunaan strain Rhizobium yang sesuai dan efektif merupakan faktor penting untuk menghasilkan bibit akasia yang sehat. Penggunaan inokulan Rhizobium tersebut dapat mengurangi biaya produksi pembibitan dan juga pencemaran lingkungan yang disebabkan oleh penggunaan pupuk N inorganik. Penelitian ini bertujuan untuk menyeleksi isolat Rhizobium yang efektif dalam meningkatkan pertumbuhan A. crassicarpa yaitu tinggi dan bobot kering tanaman. Disamping itu, penelitian ini juga bertujuan untuk mengetahui kadar dan serapan N, P dan K serta aktivitas nitrogenase. Penelitian ini dilakukan di Rumah Kaca, Laboratorium Biologi Tanah dan Laboratorium Kimia dan Kesuburan Tanah Departemen Ilmu Tanah dan Sumberdaya Lahan, Fakultas Pertanian, IPB. Digunakan tanah podsolik merah kuning (Ultisol) yang belum pernah diolah sebagai media pertumbuhan. Tanah tersebut berasal dari Stasiun Penelitian Hutan Haurbentes , Jasinga yang bersifat masam dengan tingkat kesuburan yang rendah. Salah satu tanah tersebut dilakukan sterilisasi dengan autoklaf dan juga pengapuran untuk menaikkan pH 6.5. Isolat Rhizobium yang digunakan dalam penelitian ini merupakan hasil isolasi bintil akar A. crassicarpa berumur 4 tahun yang tumbuh pada tanah gambut di kawasan HTI RAPP Pelalawan, Pangkalan Kerinci, Riau. Isolat tersebut yaitu Rh Ac-1; Rh Ac-2; Rh Ac-3; Rh Ac-4; Rh Ac-5; Rh Ac-6; Rh Ac-7; Rh Ac-8; Rh Ac-9 dan Rh Ac-10. Digunakan dua perlakuan blanko yaitu (1) tanpa inokulasi isolat Rhizobium dan tanpa pemupukan N inorganik, (2) tanpa inokulasi isolat Rhizobium tetapi dipupuk 45 ppm N inorganik. Jumlah perlakuan sebanyak 12 dengan 3 ulangan, sehingga total satuan percobaan sebanyak 60. Digunakan Rancangan Acak Lengkap (RAL) yang dilanjutkan dengan Analisys of Variances (ANOVA) dengan uji lanjut Duncan Multiple Range Test (DMRT) taraf 5%. Hasil penelitian menunjukkan bahwa diperoleh 3 isolat Rizobium dari 10 isolat yang diuji sangat nyata meningkatkan pertumbuhan A. crassicarpa (tinggi dan bobot kering tanaman) dan kadar N serta serapan N dan K. Ketiga isolat tersebut yaitu Rh Ac-1, Rh Ac-5 dan Rh Ac-4. Perlakuan isolat Rh Ac-1 menghasilkan Bobot Kering Akar 191% dan serapan K sebesar 136% terhadap Blanko. Disamping itu, perlakuan isolat Rh Ac-5 menghasilkan tinggi sebesar 56% dan Rh Ac-4 menghasilkan bobot kering tanaman bagian atas sebesar 84% terhadap Blanko. Pengaruh inokulasi isolat Rh Ac-1, Rh Ac-4 dan Rh Ac-5 terhadap pertumbuhan bibit A. crassicarpa setara dengan penggunaan pupuk 45 ppm N inorganik dan lebih baik dari pada yang tidak diinokulasi. Ketiga isolat tersebut mampu berkompetisi dengan Rhizobium indegenus.
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Judul: Uji inokulum rhizobia dan pengaruhnya terhadap pertumbuhan Acacia mangium pada tanah masam bekas tambang
Abstrak: Acacia mangium is a legume plants, which became widely known in Indonesia. This plant can make symbiosis with rhizobia to form nodules on legume crops in order to fix nitrogen for the needs of plants. In addition, it also has the ability to adapt in marginal lands, rapid growth, and good characteristhic of wood. Thus, this plant is used to fulfil the needs of industry and potential to be developed as a commodity of Industrial Timber Estates. Generaly the symbiosis between rhizobia and A. mangium can grow well only in neutral soil. However this symbiosis also has been found in acid soil and very acid soil. In this research, there were three inoculant treatments isolated from nodules of A. mangium which grown in three different places. They were KPC inoculant treatment and Kampus inoculant treatment represented acid soil, and also RR inoculant treatment represented very acid soil. Each treatment was given one ml of rhizobia inoculant. The fertilizers given were urea and KH2PO4, i.e. 0.12 g/polybag equivalent to 240 kg/ha urea and 0.08 g/polybag equivalent to 160 kg/ha KH2PO4, respectively. The plant growth media were made from the ex-mining acid soil and cow dung with ratio of 1:1 and the pH was 3.68. Analysis of variance showed that rhizobia inoculant treatment significantly increase the availability of ammonium and nitrate in the soil for all treatments. KPC inoculant treatment had the highest value of ammonium and nitrate in soil, also N plant uptake i.e. 73.1 ppm, 251.7 ppm, and 94 mg, respectively. Then, followed by RR inoculant treatment i.e. 57.4 ppm, 233.7 ppm, and 93 mg respectively. Meanwhile, RR inoculant treatment had the highest value of N-total concentration that is 2.79%. In the RR inoculant treatment occured “the concentration effect” where the N-total concentration was high but the N plant uptake was low. In the other way, KPC inoculant treatment had lower N-total concentration than RR inoculant treatment, but the plant N uptake was higher than RR inoculant treatment, this is called as “the dilution effect”. The results showed that KPC and RR inoculants treatment significantly increase dry weight of upper plant, N-total concentration, and N plant uptake. The addition of rhizobia inoculant significantly increase the value of ammonium and nitrate in soil also N-total concentration and N plant uptake in all treatments as compared with control plant.
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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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