Judul: Potensi Bakteri Rhizosfer sebagai Pupuk Hayati pada Persemaian Tanaman Sengon (Paraserianthes falcataria).
Abstrak: Biological fertilizer is one of alternative fertilizer from nitrogen fixing bacteria for albizia. The aim of this research was to utilize rhizosfer bacteria from forest soil as biological fertilizer for albizia nursery (Paraserianthes falcataria). Growing media for albizia seedling was polybag filled of acid soil from Jasinga (Ultisol type) with pH 4.7 and peat with ratio 2:1. Rhizosfer bacteria used in the study was Burkholderia cepacia with isolate codes L6.5 and L10.1. Streak quadrant results showed rhizosfer bacteria had coccus form, was not absorb pink color, and had convex elevation. Rhizosfer bacteria isolate L6.5 and L10.1 that were added with ½ N from NPK fertilizer for albizia nursery showed similar influence with fertilization using NPK dosage as recommended. NPK fertilizer with ½ N dosage that was added to rhizosfer bacteria showed influences at root length, lateral root amount, crown length, wet weight, dry weight, and nodule amount compared with control.
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Judul: Teknologi formulasi pupuk hayati rizobakteria dan aplikasinya sebagai pemacu pertumbuhan tanaman kedelai dan biofungisida pada tanah masam
Abstrak: Soybean production in Indonesia is still low, therefore Indonesian government must import soybean from other countries up to 45-50% to fulfill national requirement. This is a problem that should be solved through many approaches. One of the approach to increase soybean production through the use of plant growth promoting rhizobacteria (PGPR) that have been understood important in plant health and fitness. Our previous study resulted several indigenous strains of Pseudomonas sp. and Bacillus sp. from soybean rhizosphere that are combined with nitrogen-fixing bacteria Bradyrhizobium japonicum from soybean plant. The combinations of these bacteria were potential as plant growth promoter and biocontrol for root phytopathogenic fungi (biofungicide). For further use of these rhizobacteria, need to be developed bioprocess technology for formulation of inoculants production to increase soybean productivity. Objective of this research was to made biofertilizer containing rhizobacteria to be applied on soybean in acid soils. This research was conducted in 3 stages; optimalization media production in laboratory, formulation and bioassay in the greenhouse. The best medium for inoculants production are skim milk and molasses that produce bacterial population of 108-109 cfu/ml. Peat and talcum powder were used to formulation as carrier material. Three kind of prototype were produced; there were M-Sr (isolate Cr24, Crb17 dan Bj11); M-Rs (isolate Cr55, Crb64 dan Bj11); dan M-Fo (isolate Cr76, Crb86 dan Bj11). Each inoculant formed to three forms of formulations; there were granules (G), talc powder (T) and peat powder (S). Greenhouse test showed that several combinations of bacteria in the formula can stimulate the height of soybean plant, root weight, and plant performance. The biofertilizer applied with doses 400 g/ha for talc powder and peat powder. Rhizobakteria inoculants can be used as biofungicide. Disease suppression on Sclerotium roflsii, Rhizoctonia solani and Fusarium oxysporum respectively 79.98%, 27.27%, 50.12%. Storage up to 6 months was still able to maintain the bacterial population to 107-108 cells/g. Based on this result, we will asses this formula in field experiments under acid soils.
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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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