Judul: Perubahan Fraksi Fosfor Cepat Tersedia pada Tanah Tergenang yang Diameliorasi Bahan Organik
Abstrak: Prolong phosphorus fertilization has result in high unavailable P residue in soil. In this condition, further P fertilization will not result in higher plant productivity known as leveling off. P in soil exists in inorganic and organic forms, and in broad-range of availability from freely available to unavailable forms. The objective of this research was to study the effects of organic matter on rapidly available P extracted with 0.5 M NaHCO3 in submerged soil. Organic matter treatments were 0, 500, 750, 1000, 2000, and 5000 kg/ha. Research unit was 200 g soil (105oC ovendry weight) in a 10 cm diameter pot. Everyweek for 5 weeks, subsamples of each research unit was extracted for determining NaHCO3-P fraction following Tiessen and Moir 1993 procedure. The results showed that NaHCO3-P increased with increasing organic matter treatments and submersion time. Some dynamics, however, were found that likely related to redox dynamics in submerged soil.
Keyword: Bogor Agricultural University (IPB), Submerged Soil, NaHCO3-P, P availability, Organic Matter

Judul: Perubahan Fraksi Fosfor Lambat Tersedia pada Tanah Tergenang yang Diameliorasi Bahan Organik
Abstrak: The low availability and easily fixed phosphorus (P) in soil resulted in heavy and continuous P fertilization by farmers, leading to accumulation of residue-P in soil. In such condition, further P fertilization will not result in higher plant productivity known as leveling off. One way to increase the availability of residual P in soil is to add organic matter. There are various forms of P in the soil, from soluble to unavailable phosphorus can also be differenciated as inorganic and organic forms, where the sum of both referred as total-P. The objective of this research was to study the changes of slow-available phosphorus fraction in a submerged soil ameliorated with organic matter effect of organic matter (extracted with 0.1 M NaOH). Research unit was 200 g (oven-dry, 105°C) in a 10 cm pot. The soil was treated with 0, 500, 750, 1000, 2000, and 5000 kg/ha, and submerged for 5 weeks. Every week for 5 weeks, subsample of each research unit was extracted for determination of NaOH-P following Tiessen and Moir 1993 procedure. The results showed that in general NaOH-Pi, NaOH-Po, and NaOH-Pt increase with increasing organic matter treatments. There was a dynamic pattern of NaOH-Pt, NaOH-Pi, and NaOH-Po with the time of submersion, in which in general NaOH-P initially decreased, increased, then finally decreased.
Keyword: Bogor Agricultural University (IPB), Submerged Soil., Organic Matter, NaOH-Pt, NaOH-Po, NaOH-Pi

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