Judul: Manufature of Potassium Silicate fertilizer Made from Silica sand of Bangka
Abstrak: Salah satu upaya pemanfaatan potensi pasir kuarsa yaitu melalui pembuatan pupuk kalium silikat (K2SiO3), melalui reaksi SiO2 dengan kalium hidroksida (KOH). Penelitian ini bertujuan mendapatkan suhu optimal dalam pembuatan pupuk K2SiO3 melalui pencampuran pasir kuarsa atau SiO2 dari Bangka dan KOH. Lebih jauh penelitian ini bertujuan mengevaluasi kelarutan pupuk K2SiO3 pada tanah serta pengaruhnya terhadap pH tanah, alumunium dapat ditukar (Al-dd), kalium dapat ditukar (K-dd) dan silika (Si) tersedia melalui percobaan inkubasi pada Podsolik Dramaga. Hasil menunjukan bahwa kandungan kalium dalam bentuk kalium oksida (K2O) tertinggi pada suhu 1000oC sebesar 66,9%, sedangkan terendah pada suhu 700oC sebesar 55,1%. Sebaliknya, kandungan Si dalam bentuk SiO2 pada suhu 1000oC sangat rendah. Kandungan SiO2 pupuk kalium silikat tertinggi pada suhu 800oC sebesar 35,1%. Pupuk K2SiO3 yang paling optimal dari penelitian ini adalah pada suhu 800oC dengan memiliki kandungan K2O 60,0% dan SiO2 35,1%. Percobaan inkubasi menunjukkan dosis pupuk kalium silikat 2,5% adalah dosis yang paling efektif karena selain meningkatkan hara K-dd dan Si tersedia, juga mampu menurunkan nilai Al-dd dan memperbaiki nilai pH tanah menjadi relatif netral., One of the efforts to utilize the potential for quartz sand (SiO2) is through the manufacture of potassium silicate (K2SiO3) fertilizer, by reacting SiO2 with potassium hydroxide (KOH). This study aimed to obtain the optimal temperature in the manufacture of K2SiO3 fertilizer by mixing quartz sand or SiO2 from Bangka and KOH. Furthermore the study aimed to evaluate the solubility of fertilizer in soil and its effect on soil pH, exchangeable aluminum (exchangeable Al), exchangeable potassium (exchangeable K) and available silica (Si) through incubation experiment on Podzolik Darmaga. The results showed that the highest K content in the form of potassium oxide (K2O) was at 1000o celcius (C) with a content of 66,9%, while the lowest was at 700o C with a content of 55,1%. In contrast, the Si content in the form of SiO2 at a temperature of 1000o C was very low. The highest SiO2 content of K2SiO3 fertilizer at a temperature of 800oC was 35,1%. The most optimal K2SiO3 fertilizer from this study was at a temperature of 800o C with a content of 60,0% K2O and 35,1% SiO2. Incubation experiment showed that the K2SiO3 with the rate of 2,50% was the most effective rate because besides increased the exchangeable K and available Si, it also reduced the exchangeable Al and improved the soil pH to relatively neutral.
Keyword: Potassium silicate, quartz sand, soil acidity

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: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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