Judul: Pengaruh Pemberian Pupuk Organik pada Kadar Asam Humat dan Asam Fulvat Tanah di Lahan Pertanian Organik
Abstrak: Humic acid and fulvic acid are active compounds of humus, resulted fi'om decomposition process of organic matter. These compounds play an important part in increasing the plant growth. Therefore, their availability in the soil must be ensured. The level of humic acid and fulvic acid in the soil can be increased by adding organic fertilizers. Different kinds of organic fertilizers will produce a different content of humic acid and fulvic acid. It depends on the fertilizers contents of lignin, carbon, nitrogen, and its humification process in the soil. The purpose of this research is to find out the effect of organic fertilizers in humic acid and fulvic acid level on welsh onion and cauliflower field in PeI'mata Hati Farm, Cisarua Bogor. The treatments were arranged by Randomize Block Design with 8 treatments and 3 repetitions. Organic fertilizers used were chicken manure, goat manure, Tithonia diversifolia, Chiollloiaena odorata, banana stem compost, plants residue compost, chaffs charcoal, and Mucuna. Analysis of Variance and DMRT (Duncan's Multiple Range Test) were done at level (J. = 5%. The result indicated that level of humic acid and fulvic acid not significantly different caused organic fertilizers. The highest level of humic acid and fulvic acid (0.28% and 0.71%) was resulted from 25 kg of chicken manure treatment (as a control).
Keyword: 

Judul: Pengaruh asam humat dan cara pemberiannya terhadap pertumbuhan dan produktivitas tanaman padi (Oryza sativa)
Abstrak: Agricultural land in Indonesia degraded continuously, characterized by decreasing in soil organic matter resulting from the utilization of chemical fertilizers which is not followed by organic fertilizers. In the rice field, the decrease of organic matter is followed by soil compacting and the decrease in soil pH. In order to increase paddy production, it is needed to improve the soil qualities plants growth. This can be achieved by providing ameliorants such as organic matter with chemical fertilizers. But there is a problem in applying organic matter because of its huge volume. Therefore, it is necessary to find a way to replace the organic matter with other materials that are easier not only in procurement but also in application. Humic acid is an extract of organic material which is expected to be able to replace the role of organic matter in improving physical, chemical, and biological properties of soils. Humic acid is expected to be able for improve plant growth through its role in accelerating the absorption of soil nutrients and water. The research was conducted in a greenhouse located at Cikabayan, Bogor Agricultural University with paddy var. Ciherang as the indicator plant. Soil was taken from Situ Gede, Bogor. Basal fertilizers were 300 kg/Ha SP-18, 200 kg/Ha KCl, and 200 kg/Ha urea. Humic acid dosages used were 0 L/Ha, 5 L/Ha, 10 L/Ha and 15 L/Ha. The methods of humic acid application were spraying on the surface of leaves, spraying underside of leaves, and spraying on the soil. The result showed that humic acid can increase the growth of rice plants by increasing tiller number. Humic acid dosage of 15 L/Ha spraying on the soil is the best treatment indicated by tiller number and dry weight of unhulled rice.
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