Judul: The utilization of activated carbon as micro nutrients carrier in slow release fertilizer formulation
Abstrak: In many plantations, fertilizers were often added in high dosage and applied several times in order to get maximum productivity. Actually, some processes in soil caused not all nutrients in fertilizer could be uptaken by plants. Besides, high dosage can be toxic to plants. The use of slow release fertilizer can overcome this case. Slow release fertilizers (SRF) were fertilizers coated within a substance that enables a slow release time and had higher efficiency rate than soluble fertilizers. This research was aimed to: 1) identify the characteristics of bamboo and coconut shell activated charcoal that were activated in 600oC or 700oC temperature and steamed for 90 minutes, 2) obtain the data of adsorptive capacity of activated charcoal to the nutrients mixed, 3) gathering the information about nutrients release rate of fertilizer produced, and 4) determine the influence of slow release fertilizer addition to nutrient uptake in Acacia crassicarpa. The study was conducted by converting materials into charcoal. The charcoal was then activated in 600oC and 700oC temperature and steamed for 90 minutes. The activated charcoal was ground and analyzed based on SNI 06-3730-1995. SRF was formulated by soaking fine activated charcoal in 1N or 2N of CuSO4, FeSO4 or ZnSO4 solution for 24 hours. Analysis conducted were observation of surface topography by SEM, qualitative analysis using EDX, calculation of chrystallinity, width, length and number of aromatic layer, and determination of total Cu, Fe and Zn in SRF. The optimal treatment was chosen to determine its release rate by extracting fertilizer with distilled water and 2% citric acid during 0, 15, 30, 45, and 60 minutes. The influence of SRF addition to nutrients uptake was determined by observing nutrients content in root. The results showed that the activated charcoal produced met SNI 06-3730-1995 except for its adsorptive capacity to iodine and blue methylene. Nevertheless, the activated charcoal could be used to adsorb nutrients mixed as shown by SEM and EDX results. The adsorption of Cu, Fe and Zn increased the activated charcoal chrystallinity and influence its width and length of aromatic layer. The highest nutrients concentration obtained were 11,443 ppm Cu, 5,476 ppm Fe, and 6,603 ppm Zn for bamboo activated charcoal and 10,775 ppm Cu, 7,611 ppm Fe, and 6,343 ppm Zn for coconut shell activated charcoal. Nutrients in the charcoal could be released slowly and could not be easily leached out.
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Judul: Slow Release N-Urea dalam Bentuk NH4+ dan NO3- setelah Aplikasi Arang Aktif pada Tanah Andisol
Abstrak: Urea is fertilizer that has low efficiency absorption in soil-plant system, which is about 30-50%. This is due to highly hygroscopic nature of urea that made urea dissolve easily into groundwater as nitrate when it applied to plants. Slow release fertilizer releases essential nutrient contained in urea slower than original urea fertilizer. Agriculture waste could be used as activated carbon which used to coat the urea in order to make slower release. The activated carbon in this study functioned in two different ways, as a coating material for the urea and as an adsorbent of urea residue. The research aimed to compare decreasing efficiency of dissolved urea as NH4+ and NO3- in Andisol soils using four activated carbon materials: coconut shells, rice hulls, corn cobs, and palm empty bunch during incubation period of 30 days. The result pointed out that the activated carbon could decrease NH4+ and NO3- dissolved in soil about 4-44% as compared with the control soils. It also showed that the activated carbon was the most effective in decreasing dissolved NH4+ and NO3- were those derived from coconut shells and rice hulls.
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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