Judul: Comparison of nitrogen absorption by corn (Zea mays L.) from four urea fertilizers
Abstrak: Jagung merupakan salah satu komoditas pangan utama di Indonesia. Peningkatan produktivitas jagung umumnya menggunakan pupuk urea untuk memenuhi kebutuhan nitrogennya. Masalah utama terkait penggunaan urea yaitu tingginya jumlah nitrogen tercuci. Salah satu upaya mencegah pencucian N yaitu dengan mengubah senyawa urea menjadi senyawa urea lambat tersedia (slow release), diantaranya dengan mengubah sebagian senyawa urea menjadi urea-formaldehida yang bersifat lambat tersedia. Penelitian ini bertujuan untuk mempelajari pengaruh empat jenis pupuk urea terhadap bobot biomassa kering, serapan nitrogen, dan efisiensi serapan nitrogen. Penelitian menggunakan rancangan acak lengkap satu perlakuan dengan empat ulangan. Penelitian dilaksanakan di rumah kaca dengan media tanah seberat 15 kg (Bobot Kering Mutlak) dengan polybag. Perlakuan terdiri atas perlakuan tanpa pemupukan N (kontrol), pemupukan urea konvensional yang terdiri dari urea kujang dan urea pusri dan urea slow-release berupa urea urea granul (0,5% formaldehida) dan urea prill (0,1% formaldehida). Biomassa bagian atas tanaman untuk keperluan analisis dipanen tiap minggu selama 10 minggu dari satuan percobaan yang terpisah. Analisis kadar N jaringan jagung dilakukan setiap minggu panen dengan metode mikro Kjehdahl. Hasil percobaan menunjukkan pemberian urea slow-release, khususnya urea granul, meningkatkan bobot biomassa jagung dibandingkan dengan penggunaan urea konvensional. Selain itu, penggunaan urea slow-release memiliki tingkat efisiensi lebih tinggi dibandingkan dengan urea konvensional. Faktor yang menyebabkan urea granul memiliki serapan dan efisiensi yang lebih tinggi adalah pelapisan butir dengan senyawa urea-formaldehid pada urea slow-release., Corn is one of the main foods commodities in Indonesia. To increase corn productivity, urea fertilizer is commonly used to supply its nitrogen (N) needs. The main problem related to the use of urea fertilizer is the high amount of nitrogen leached. One way to prevent nitrogen leaching is by forming a urea compound to a slow-release compound, one of them is changing part of the urea compound to urea-formaldehyde. This research was aimed to study the effect of four different urea fertilizers on corn’s biomass production, nitrogen absorption, and nitrogen absorption efficiency. This research used a completely randomized design of one factor with four repetitions. The research was carried out in a greenhouse with 15 kg soil as plant’s media in a polybag. The treatments consisted of treatment without N fertilization (control), conventional urea fertilizers (kujang urea and pusri urea), and slow-release ureas which is granule urea (0.5% formaldehyde) and prill urea (0.1% formaldehyde). Upper plant biomass for analysis was harvested every week for 10 weeks from separated experimental uni. Total N analysis was determined by mikro Kjeldahl method. The result showed that the application of slow-release urea, especially granulated urea, increased nitrogen absorption and biomass weight compared to the application of conventional urea fertilizers. Factors that cause the granule slow-release urea has higher absorption and efficiency is the coating of the grain with urea-formaldehyde
Keyword: conventional urea, granulated urea, nitrogen efficiency, slow-release, urea-formaldehyde

Judul: The Effect Of Four Types Of Urea Fertilizer on Biomass and Nitorgen Uptake in Paddy (Oryza sativa L.)
Abstrak: Padi merupakan tanaman yang penting di Indonesia karena padi menjadi bahan makanan pokok bagi sebagian besar masyarakat Indonesia. Peningkatan produksi padi membutuhkan pemupukan yang relatif berkesinambungan sehingga aspek efisiensi menjadi penting. Nitrogen (N) merupakan unsur hara makro yang penting untuk padi. Kehilangan hara terutama hara N, adalah masalah yang sering terjadi dan menyebabkan kesuburan tanah rendah. Studi ini bertujuan mengevaluasi pengaruh jenis pupuk urea pada bobot kering biomasa, serapan N dan efisiensi serapan N pada tanaman padi. Penelitian ini disusun dalam rancangan acak lengkap dengan faktor tunggal yaitu jenis pupuk urea. Perlakuan terdiri dari lima perlakuan yaitu urea konvensional Kujang, urea konvensional Pusri, urea slow release Granul dan urea slow release Prill dan kontrol tanpa aplikasi pupuk. Perlakuan diulang empat kali. Sampel tanaman dikumpulkan setiap minggu dari 1 minggu setelah tanam (MST) sampai 12 MST sehingga total pot percobaan adalah 240 pot percobaan. Sidik ragam dilakukan untuk mengevaluasi efek dari perlakuan. Hasil penelitian menunjukan bahwa jenis pupuk urea tidak berpengaruh secara nyata pada berat biomasa, serapan N dan efisiensi serapan N pada 12 MST sebagai akhir pengamatan. Namun, pupuk urea slow release dalam bentuk butiran dan prill cenderung memiliki biomasa, serapan N, dan efisiensi serapan N yang lebih tinggi dibandingkan dengan urea konvensional Kujang dan Pusri., The Effect Of Four Types Of Urea Fertilizer on Biomass and Nitorgen Uptake in Paddy (Oryza sativa L.). Supervised by ARIEF HARTONO and BUDI NUGROHO. Paddy is an important plant in Indonesia because paddy becomes a staple food for most of the Indonesian people. Increasing paddy production requires relatively continuous fertilization so that the efficiency aspect becomes important. Nitrogen (N) is an important macronutrient for paddy. Nutrient loss, especially N, is a frequent problem and causes low soil fertility. This study aimed to evaluate the effect of urea fertilizer types on the dry weight of biomass, N uptake and N uptake efficiency in paddy. This study was set up in completely randomized design with a single factor, namely the type of urea fertilizer. The treatments consisted of five treatments namely conventional urea Kujang, conventional urea Pusri, slow release urea granule, slow release urea prill and control without fertilizer application. The treatments were repeated three times. Plant samples were collected weekly from 1 week after planting (MST) to 12 MST so the total number of experiment pots were 240 pots. Analyses of variance was conducted to evaluate the effect of the treatments. The results showed that the type of urea fertilizer did not effect significantly on biomass weight, N uptake and N uptake efficiency at 12 MST as the end of observation. However, slow release urea fertilizers in the form of granule and prill tended to have higher biomass, N uptake and N uptake efficiency compared to conventional urea Kujang and Pusri.
Keyword: conventional, efficiensy, granule, prill, slow release

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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