Judul: Formulasi Konsorsium Rizobakteria Pelarut Fosfat dengan Bradyrhizobium japonicum sebagai Pupuk Hayati dan Aplikasinya pada Tanaman Kedelai
Abstrak: Phosphate solubilizing rhizobacteria were known for their ability to convert insoluble form of phosphate to the accessible form. The use of rhizobacteria as biofertilizer is one of the most promising biotechnologies to improve plant production. This study was conducted to formulate phosphate solubilizing rhizobacteria (Bacillus sp. Cr and Pseudomonas sp. Crb) coinoculated with Bradyrhizobium japonicum (Bj) and appliance them to soybean plant as biofertilizer. Pikovskaya medium containing tri-calcium phosphate at concentration of 0.5% was used to measure P-solubilizing ability of tested strains. Results revealed that Crb1 is the most powerful P-solublizer using tricalcium phosphate as a P source. It was also observed decreasing in pH along with the increasing of amount of soluble P ranged from -0.96 to -0.42 from initial culture during 72 hours. Isolates of the rhizobacteria (Crb and Cr) were grown in media containing skim milk and molases prior to formulation in peat as a carrier material. The combination of three strains produced 4 packages of inoculants. Each packages was tested for their viability and effectiveness on soybeans in the field. The number of bacterial population after 9 months of storage ranged from 7.5 x 106 to 5.8 x 108 cfu gr-1 of peats. Field experiment showed that treatments designed as F1+NPK and F3+NPK were significantly increased soybean plant growth and mineral uptake compared to untreated control and better than NPK treatment. While F1+NPK and F2+NPK were able to increase soybean productivity.
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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: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf