Judul: Studi slow release fertilizer (SRF) uji formula SRF terhadap pertumbuhan dan produksi pada
Abstrak: Nitrogen adalah salah satu unsur hara esensial bagi tanaman dan biasa diberikan dalam bentuk pupuk urea. Urea memiliki karakteristik cepat larut dalam air. Dalam keadaan enzim urease cukup tersedia dalam tanah, urea dapat segera terurai menjadi ammonium dan selanjutnya dengan bantuan bakteri nitrifikasi ammonium berubah menjadi nitrat. Pada suasana alkalin ammonium dapat menguap dalam bentuk gas amoniak. Sedangkan nitrat dapat hilang melalui pencucian ataupun menguap dalam bentuk N2O dan gas nitrogen. Kehilangan nitrogen ini kurang menguntungkan karena tanaman memerlukan suplai nitrogen yang banyak selama masa pertumbuhannya. Oleh sebab itu, diperlukan usaha memodifikasi urea dalam bentuk-bentuk lambat larut dalam air. Kombinasi urea plus zeolit diharapkan mampu menjawab permasalahan tersebut.
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Judul: Studi "Slow Release Fertilizer" (SRF): Uji efisiensi formula pupuk ersedia lambat campuran urea dengan zeolit
Abstrak: Nitrogen (N) is one of macro plant nutrients which very important for plant growth. However, this nutrient is easily loss from soil because of leaching, change to other forms, and volatilizing to the air. Therefore, efforts to increase the efficiency of nitrogen fertilizer for improvement of agricultural production is necessary. Many attempts were done to reduce loss of nitrogen from soil, such as making N fertilizer as slow release form (SRF). However, most of slow release fertilizer use chemical materials as bider which can making bad effect for soil. Searching other materials which more cordial to environment is need. Zeolite is an unique mineral having high cation exchange capacity (120-180 meI100g) and porous structure may be used for slow release agent of nitrogen fertilizer. With the high exchange of ammonium ion, zeolite can adsorb and save temporary of nitrogen and release into the soil when needed. The objective of this research was to know the efficiency of slow release fertilizer made from mixture of urea and zeolite, with compared to urea fertilizer that ordinary used by farmers (urea prill and urea granule). The experiment was carried out by randomized complete design with 17 treatments and 3 replications. This experiment used paddy of Ciherang variety. Paddy was planted into pot having diameter of 28 cm and high of 32 cm. The growth parameters of paddy plant and production were recorded and evaluated. The results showed that slow release fertilizer which made by mixture of urea and zeolite at the accurate composition, binder and application can proceed production higher than urea prill and urea granule. Slow release fertilizer with ratio of urea and zeolite of 50:50 has the efficient value higher than that of slow release fertilizer with ratio of urea and zeolite of 70:30. That conclusion is shown from the paddy production. Aplication of SRF (50:50) containing 70% N gave the same production of normal dose. Therefore, slow release fertilizer with ratio of urea and zeolite of 50:50 increased the efficiency of urea 30%.
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Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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