Judul: Pengaruh Fosfat Alam, Bahan Organik dan Kombinasinya terhadap Perbaikan Sifat Kimia Tanah dan Produksi Tanaman Terung Ungu (Solanum melongena)
Abstrak: Arable land for farming system is commonly acid soils and has low nutrient content. As its low fertility, it is needed an effort to improve soil fertility and productivity. Podsolik is highly weathered acid soils that has low fertility level, but it has wide spread. Two fundamental factors limit the fertility of acid soils; nutrient deficiencies e.g. P, Ca and Mg, and the presence of phytotoxic substances e.g soluble Al and Mn (Haynes and Mokolobate 2001). Various efforts to improve the chemical properties of Podsolik such as fertilization, organic materials addition and liming. This research was aimed to observe the effect of rock phosphate, organic materials and its combination in improvement of soil chemical properties and crop production of eggplant (Solanum melongena) in Podsolik from Gajrug. The treatment laid out in a randomized complete by design with three replications. Treatment consisted of addition of rock phosphate, SP-36, organic materials, and their combinations. The results showed that the treatment of organic materials (cow dung or rice straw) affected significantly on total-N, available-P, exchangeable K, Ca, and Mg, the uptake of P and Ca, and crop production of eggplant. However, the treatment of singular rock phosphate did not effect significantly on all observed parameters. The treatment of organic materials which is combined with rock phosphate or SP-36 showed a higher crop production of eggplant than the treatment of singular organic materials (cow dung or rice straw). The highest crop production of eggplant was found in treatment of rock phosphate 100% + rice straw. It was followed by the treatment of rock phosphate 100% + cow dung .
Keyword: rock phosphate, P deficiency, organic materials

Judul: Pengaruh Pemberian Fosfat Alam Terhadap Perubahan Sifat Kimia Tanah, dan Kadar Hara Pada Tanaman Jagung (Zea mays)
Abstrak: The utilization of acid soil for agriculture faced several obstacles, including P deficient. It is because P ions sorbed by various soil components, such as Fe-Al ions, and Fe-Al hydrous oxides. One of the efforts made to overcome this problem is the use of natural phosphate in acid soils. This study aims to determine the effect of natural phosphate fertilizers in soil chemical properties and nutrients rate in plant of Latosol (Oxyc Dystrudept) Darmaga. Experimental design used in this study was a randomized design with a single factor, named P fertilizer. Source of P fertilizer used in this study is a natural phosphate and SP-36. Treatment dosage of P fertilizer are, control I (0%), control II (N + K), Std 100% (N+K+SP36), RP 50%, RP 100%, RP 150%, RP 200%, (N + K 50%) + RP 50%, and (N + K 50%) + RP 100%. The results showed that the phosphate fertilizer did not significantly affect soil pH, exchangeable-Al, available-P, exchangeable-Ca, and exchangeable-Mg. phosphate fertilizer have significantly affect only in exchangeable-K. Meanwhile, phosphate not significantly affect the rate of Mg, K, Ca, P and N. Rock phosphate’s application significantly affected the growth of maize on 4 week after planting (MST) and 6 MST. Rock phosphate’s application did differ significantly on increasing cob with husk’s weight and cob without husk’s weight. But rock phosphate’s application did not differ significantly on total weight of stover. The highest percent of crop value in treatment who give rock phosphate fertilizer there is in treatment of RP 150% with 158.1%, and the lowest percent of crop value there is in treatment of (N+K 50%) + RP 50% with 98.6%, and lowest in all treatment there in treatment of Control I with 74.7%. From result of crop value can get a conclusion that rock phosphate fertilizer is better than standard fertilizer (SP36).
Keyword: acid soil, maize, phosphate

Judul: Invers dari Matriks Tridiagonal Jacobi
Abstrak: Suatu matriks berukuran n×n dinamakan matriks tridiagonal jika untuk . Karya ilmiah ini memberikan algoritma yang mudah untuk menemukan invers ( dari matriks tridiagonal Jacobi yang simetrik dan nonsimetrik. Setiap elemen pada matriks tridiagonal ini adalah bilangan real. Terdapat 3 lema dan 2 teorema untuk menentukan . Lema pertama menunjukkan persamaan utama dalam membuktikan lema-lema dan teorema-teorema selanjutnya. Invers dari matriks yang simetrik dibuktikan oleh lema kedua yang menunjukkan elemen-elemen baris ke- dari . Selanjutnya, lema kedua dilengkapi dengan teorema pertama yang menunjukkan elemen-elemen dengan . Invers dari matriks yang nonsimetrik dibuktikan oleh lema ketiga yang menunjukkan elemen-elemen dengan dan elemen-elemen dengan dibuktikankan oleh teorema kedua.
Keyword: symmetric, nonsymmetric, matrix