Judul: Increasing Yield of Upland Rice by Applications of Silicate, Phosphate and Inoculation of Arbuscular Mycorrhizal Fungi in Ultisol, Peningkatan produksi padi gogo dengan aplikasi silikat dan fosfat serta inokulasi fungi mikoriza arbuskular pada ultisol
Abstrak: Low soil phosphorus (P) availability and P fertilization efficiency were, among others, recognized as the main production constraints of acid upland soils. Laboratory, glasshouse and field experiments conducted with Typic Hapludult from Jasinga region. The objectives of laboratory experiment was to study the effect of Si on available of P, sorption of P, Al and Fe-P, soil charges, pH, exchangeable Al and Fe, amorphous Al and Fe, and effective CEC. Glasshouse experiment was to study the effect of Si (Na2SiO3), P and inoculation of AMF on unhulled rice yield and P, N, K, Ca and Mg leaf flag content. While, field experiment was to study the effect of Si (basic slag and Na2SiO3), P, and AMF inoculation to rice yield and the uptake of P, N, K, Ca, Mg and Fe content of rice straw. Our laboratory experiment showed that: At Si treatment at rate 1 x exchangeable Al, the soil-P increased about 6.67% (from 9.0 to 9.6 ìg P/g), pH value (from 4.85 to 5.51), and exchangeable-Al decreased (from 8.87 to 5.83 me/100 g of soil). Increasing in soil-P was related to the decreasing in P sorption energy (from 632.23 to 20.31 ml/ìg) or the increase in net negative charges as confirmed by the increase in ÄpH value (from 1.02 to 1.71). At 98 ìg/g P treatment (0.2 ìg/ml P in soil solution) the available of P increased 91% but followed by increasing in Al-P and Fe-P by 160 and 65 %. The availability of P fertilizer due to formerly Si addition higher than if Si added after phosphate.
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Judul: Pengaruh Fosfor dan Silikon terhadap Pertumbuhan dan Produksi Padi Gogo (Oryza sativa L.) Varietas Situ Patenggang pada Latosol Dramaga
Abstrak: Phosphorus (P) and Silicon (Si) deficiencies were two kinds of constraint of upland rice production. Latosol is one type of soil that is poor in nutrients, especially P and Si, acidic reaction due to intensively weathering and leaching. Greenhouse trial has conducted at experimental station of Cikabayan, Dramaga, and Chemistry and Fertility Laboratory of Soil, Department of Soil Science and Land Resources, Bogor Agricultural University. Materials were used at this study are: a soil material (Dramaga’s Latosol), upland rice seed cultivar Situ Patenggang, SP-36, Na2SiO3, KNO3, Urea, KCl. Research includes: Si liquid fertilizer formulation, and trial the effect of fertilizers of P, Si and Si application method to the growth and yield of upland rice with a completely randomized factorial design. Results of the trial showed that treated of P increasing the growth and yield of upland rice (plant height, number of tillers, dry weight of grain and straw dry weight) as well as increasing the levels of P straw. Treated of Silicon has increasing the growth and yield of upland rice (plant height, number of tillers, number of panicle, dry weight of grain and straw dry weight) and increasing the Si content in the straw and husk. The interaction effect was only found on the treated of P and the Si fertilizer application methods (T) on the variable of dry weight of grain and treated of Si and T on the variable of dry weight of straw. Silicon fertilizer can be applied through the leaves with spraying. Silicon fertilizer application via the soil slightly more effective than through the leaves.
Keyword: upland rice, phosphorus, silicon

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