Judul: Application of nitrogen-fixing and phosphate solubilizing bacteria in matriconditioning to increase growth and yield of bambara groundnut (Vigna subterranea) and reduce nitrogen-phosphate fertilizer
Abstrak: Kacang bambara (Vigna suterranea (L) Verdcourt) berpotensi sebagai pangan alternatif dikarenakan memiliki kandungan protein dan karbohidrat yang tinggi. Namun, produktivitas kacang bambara di Indonesia masih rendah. Perlakuan invigorasi benih dengan metode matriconditioning yang dikombinasikan dengan penggunaan bakteri dapat meningkatkan pertumbuhan dan hasil kacang bambara. Penelitian ini bertujuan untuk: (1) mendapatkan karakter dan kompatibilitas bakteri penambat nitrogen dan pelarut fosfat serta viabilitasnya dalam media pembawa; (2) mengevaluasi pengaruh invigorasi benih yang dikombinasikan dengan bakteri penambat nitrogen dan pelarut fosfat dalam matriconditioning untuk meningkatkan pertumbuhan dan hasil kacang bambara serta menghemat dosis pupuk nitrogen-fosfat. Percobaan pertama untuk mendapatkan karakter dan kompatibilitas bakteri penambat nitrogen dan pelarut fosfat serta membandingkan viabilitasnya dalam media pembawa (lolos saringan 0,5 mm) yang berbeda, yaitu bubuk arang sekam padi dan biochar tongkol jagung. Percobaan dilaksanakan pada bulan Maret sampai Juli 2020 di Laboratorium Bioteknologi Tanah Departemen Ilmu Tanah dan Sumberdaya Lahan, serta Laboratorium Kesehatan Benih Departemen Agronomi dan Hortikultura, Fakultas Pertanian, Institut Pertanian Bogor. Percobaan ini terdiri atas uji patogenitas (uji hipersensitivitas dan uji aktivitas hemolitik), uji kemampuan penambatan nitrogen (uji Nessler), uji kemampuan pelarut fosfat pada media Pikovskaya padat, uji kompatibilitas, dan uji viabilitas pada media pembawa. Hasil percobaan pertama menunjukkan isolat Rhizobium KPB4 bersifat patogen terhadap hewan atau manusia (uji aktivitas hemolitik). Isolat bakteri penambat nitrogen dipilih isolat yang memiliki nilai konsentrasi NH3 tertinggi, yaitu Rhizobium KBP2 (94,46 mg L-1) dan Rhizobium KBP5 (92,63 mg L-1). Isolat bakteri pelarut fosfat (Pseudomonas BPF9) memiliki indeks pelarutan fosfat sebesar 1,14. Masing-masing isolat bakteri penambat nitrogen kompatibel terhadap terhadap isolat Pseudomonas BPF9. Hasil uji viabilitas menunjukkan populasi bakteri pada media pembawa biochar tongkol jagung memiliki populasi lebih tinggi (15,50 x 107 CFU g-1) dibandingkan arang sekam setelah 4 minggu disimpan pada suhu ruang (± 27 oC). Percobaan kedua untuk mengevaluasi pengaruh invigorasi dengan metode matriconditioning yang dikombinasikan dengan bakteri penambat nitrogen dan bakteri pelarut fosfat dalam meningkatkan pertumbuhan dan hasil kacang bambara serta menghemat dosis pupuk nitrogen-fosfat. Percobaan dilaksanakan di Desa Samoja Kecamatan Situraja Kabupaten Sumedang pada bulan November 2020 sampai April 2021. Percobaan disusun menggunakan split plot design dengan tiga ulangan. Petak utama adalah dosis pemupukan N-P (0, 50, dan 100% dari dosis rekomendasi). Anak petak adalah invigorasi benih (tanpa perlakuan, matriconditioning + Rhizobium KPB2 + Pseudomonas BPF9, dan matriconditioning + Rhizobium KPB5 + Pseudomonas BPF9). Perlakuan matriconditioning menggunakan biochar tongkol jagung sebagai carrier (media pembawa) dengan rasio 5 : 3 : 4,5 (benih : biochar tongkol jagung : inokulan bakteri). Peubah yang diamati adalah daya tumbuh, tinggi tanaman, jumlah daun, diameter kanopi, tingkat kehijauan daun menggunakan SPAD (Soil Plant Analysis Development) Minolta 502, bobot kering nodul akar per tanaman, bobot basah dan kering brangkasan per tanaman, bobot basah dan kering polong per tanaman, bobot biomassa per tanaman, serta jumlah polong per tanaman. Hasil percobaan kedua menunjukkan bahwa matriconditioning + Rhizobium KPB2 + Pseudomonas BPF9, dan matriconditioning + Rhizobium KPB5 + Pseudomonas BPF9 efektif meningkatkan pertumbuhan vegetatif tanaman (daya tumbuh, tinggi tanaman, jumlah daun, diameter kanopi, dan kandungan klorofil daun), bobot kering nodul akar per tanaman, dan hasil kacang bambara (bobot basah dan kering polong serta jumlah polong per
Keyword: biochar tongkol jagung, invigorasi benih, media pembawa, pemupukan, Pseudomonas sp., Rhizobium sp., rhizobakteri

Judul: Pengaruh Perlakuan Invigorasi Pada Benih Yang Berbeda Tingkat Masak Terhadap Viabilitas Dan Vigor Benih, Pertumbuhan Tanaman, Dan Hasil Kacang Bogor (Vigna subterranea (L.) Verdcourt)
Abstrak: Bambara groundnut can be cultivated in marginal land, however, its productivity is low. In order to increase the productivity, high quality of seeds must be used. Two consecutive experiments were conducted in laboratory and field at Bogor Agricultural University from April to October 2010. Seeds of three maturity levels were harvested from farmer’s field in Sukabumi, April 2010. The seeds were dried down to 11.6% moisture content before being used. The objectives of the experiments were to evaluate effects of seed invigoration applied on bambara groundnut seeds of three maturity levels on seed vigor, plant growth, and yield. Laboratory experiment was arranged in a completely randomized design while field experiment was arranged in a completely randomized block design. In both experiments, two factors were applied, seed maturity and invigoration. There were three levels of seed maturity i.e. seeds harvested at 119, 122, and 125 days after planting (dap). Seed invigoration consisted of untreated, Rhizobium sp., matriconditioning, matriconditioning plus Rhizobium sp. Matriconditioning was conducted using ratio of seeds to carrier (burned rice hull) to water of 20:12:12 (g) for 3 days in air-conditioned room ca. 25 0C. Rhizobium sp. 0.3 g/100 g seeds was either applied on seeds just before planted or incorporated in matriconditioning. Results of the laboratory experiment showed that matriconditioning alone or matriconditioning plus Rhizobium sp. applied on seeds harvested at 122 daf or 125 dap improved seed vigor (speed of germination and index of vigor). However, there was no interaction occurred between the two factors in the field experiment. Seeds treated with matriconditioning plus Rhizobium sp. or harvested at 125 dap showed the best improvement in plant growth (plant height, number of leaves, number of branches) and yields (number and weight of pods).
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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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