Judul: The Effect of Supplementary Fertilizer Types on The Growth and Yield of Various Amaranth (Amaranthus sp.) Genotypes
Abstrak: Bayam merupakan tanaman sayuran dengan kandungan vitamin dan mineral tinggi yang kedua paling banyak dikonsumsi di Indonesia. Produktivitas nasional bayam tergolong rendah pada kisaran 20% potensi hasil, sedangkan luas lahan budidaya memiliki tren menurun. Produktivitas dapat ditingkatkan melalui penggunaan varietas unggul dan pemupukan yang optimal. Pupuk susulan diberikan untuk mengantisipasi cepat hilang atau tercucinya pupuk terutama pupuk nitrogen. Penelitian ini bertujuan mengetahui pengaruh jenis pupuk susulan terhadap pertumbuhan dan produktivitas berbagai genotipe bayam. Penelitian dilakukan pada bulan Februari hingga April 2021 di Kebun Percobaan Leuwikopo Institut Pertanian Bogor. Penelitian ini menggunakan rancangan kelompok lengkap teracak (RKLT) pola tersarang, dengan petak utama jenis pupuk susulan (NPK dan urea) dan anak petak genotipe bayam yang terdiri dari 7 genptioe bayam yang diulang sebanyak 3 kali dalam petak utama. Hasil penelitian menunjukkan genotipe bayam V1 memiliki sifat agronomis paling baik, dengan umur paling genjah dan produktivitas tertinggi. Tidak adanya perbedaan yang nyata antar jenis pupuk susulan urea dan NPK mengindikasikan bahwa pupuk urea dapat mengsubstitutsi penggunakan pupuk NPK pada penelitian ini. Substitusi pupuk NPK dapat mengurangi biaya produksi dan mencegah pemupukan yang berlebihan., Amaranth is a vegetable high in vitamins and minerals that is the second most consumed in Indonesia. The national yield of amaranth is considered low at 20% of the potential yield, while amaranth acreage is on a downward trend. Crop yield can be increased with the use of superior high-yielding varieties and optimal fertilization. Supplementary fertilizer is applied to anticipate the washing away or leaching of fertilizer, especially nitrogen fertilizer. This study aims to determine the effect of supplementary fertilizer types on the growth and yield of various amaranth genotypes. The study was conducted at Leuwikopo Experimental Station, IPB University from February until April 2021. This study used the nested randomized complete block design (RCBD), with supplementary fertilizer types (NPK and urea) as the main blocks, and 7 amaranth genotypes as the plots repeated 3 times in the main blocks. Study results show that amaranth genotype V1 has good agronomical traits, with shortest harvest life and highest yield. The lack in significant difference between urea and NPK fertilizer types indicated urea can replace NPK as supplementary ferlitizer in this study. Substitution of NPK with urea can reduce production cost and prevent overfertilization.
Keyword: high yield, NPK fertilizer, short harvest life, superior varieties, urea fertilizer

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: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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