Judul: Effect of Basic Fertilizer Application Time on Growth and Productivity of Various Amaranthus Genotypes (Amaranthus sp.)
Abstrak: Produktivitas nasional bayam tergolong rendah pada kisaran 20% potensi hasil, sedangkan luas lahan budidaya menunjukkan tren menurun. Produktivitas dapat ditingkatkan melalui penggunaan varietas unggul dan pemupukan yang optimal. Pemupukan yang optimal sangat penting karena tanaman semusim seperti bayam memiliki siklus hidup yang singkat. Pupuk dasar yang diaplikasikan pada waktu yang tepat dapat mengoptimalkan pertumbuhan dan produktivitas bayam. Penelitian ini bertujuan mengetahui pengaruh waktu aplikasi pupuk dasar terhadap berbagai genotipe bayam. Penelitian ini menggunakan rancangan kelompok lengkap teracak (RKLT) pola tersarang, dengan petak utama waktu aplikasi pupuk dasar (0 MST dan 1 MST) dan anak petak 14 genotipe bayam. Hasil analisis ragam menunjukkan waktu aplikasi berpengaruh sangat nyata terhadap karakter-karakter agronomis seperti panjang daun, lebar daun, panjang tangkai daun, diameter batang, luas daun, bobot pertanaman, dan produktivitas, serta berpengaruh nyata pada tinggi tanaman dan jumlah daun saat 2 MST. Terdapat keragaman yang nyata antara genotipe yang diuji pada semua karakter., The national productivity of spinach is low at around 20% of potential yield, while the area of cultivated land shows a declining trend. Productivity can be increased by use of high yield varieties and optimal fertilization. Optimal fertilization is very important because annuals such as spinach have a short life cycle. Basic fertilizer applied at the right time can optimize the growth and productivity of spinach. This study aims to determine the effect of basic fertilizer application time on various genotypes of spinach. This study used a nested completely randomized complete block design (RKLT), with the main plots of basic fertilizer application time (0 MST and 1 MST) and subplots of 14 spinach genotypes. The results of the analysis of variance showed that application time had a very significant effect on agronomic characters such as leaf length, leaf width, petiole length, stem diameter, leaf area, plant weight, and productivity, and had a significant effect on plant height and number of leaves at 2 WAP. There was significant variation between the genotypes tested for all characters.
Keyword: application time, basic fertilizer, fertilization, genotype, productivity

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: 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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