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: Perbaikan Sifat Kimia Tanah Masam, Produksi, dan Serapan P Tanaman Kacang Tanah (Arachis hypogaea) dengan Pemberian Pupuk Fosfat Alam
Abstrak: Potential of land resources in Indonesia is very large. Indonesia has 148 million ha of upland. Climate variation, specifically precipitation in most areas of Indonesia is relatively high therefore leaching of bases in the soil mostly high. It causes the low content of bases in soil, and then the soil become acid and have nutrients deficiency. About 102.8 million ha or 69.5 % of the total upland in Indonesia have acid soil. The utilization of acid soil for agriculture have several problems such as P-deficiency. It is due to the phosphate ions is adsorbed by the various component in the soil, such as Fe and Al ions, and Fe and or Al hydrous oxide. One of the efforts to overcome the P-deficiency is to apply rock phosphate into acid soil. The use of rock phosphate as fertilizer because highly soluble in the acid soil condition. Therefore, rock phosphate is appropriate as a source of P fertilizer in acid soil. The objectives of this research were to study the effect of rock phosphate fertilizer on the improvement acid soil quality, on groundnut yield, and P uptake of groundnut plant (Arachis hypogaea) in Latosol (Oxyc dytropept) Darmaga, Bogor. The experimental design was used is a randomized complete block design with one factor, that is dosage of phosphate fertilizers. Phosphate Fertilizer used in this experiment were rock phosphate and SP-36. Phosphate fertilizer dosages were: 0% (as a control treatment), Std 100%, Std 50% + P 50%, Std 25% + P 75%, P 100%, P 125%, and P 150%. The results of the study showed that rock phosphate fertilizer significantly increased the soil pH, exchangeable Ca, the uptake of Ca and P of groundnut plant. The phosphate fertilizer treatments were not increase significantly different in the growth, weight of pod, weight of seed, and percentage of full pod. However, the rock phosphate treatments resulted the percentage of full pod (87.76%-90.01%) was higher than standard fertilizer treatment (86.51%).
Keyword: 

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