Judul: Effects of Urea Fertilizer Dosage and Varieties on Growth and Yield of Maize (Zea mays L.)
Abstrak: Jagung adalah komoditas penting di Indonesia yang permintaannya terus meningkat sehingga produktivitasnya perlu ditingkatkan dengan penggunaan benih bermutu dan pemupukan berimbang. Penelitian bertujuan mengetahui pengaruh dosis pupuk Urea dan varietas terhadap pertumbuhan dan produksi jagung. Penelitian dilaksanakan menggunakan rancangan petak terbagi dalam rancangan kelompok lengkap teracak. Perlakuan terdiri dari 2 faktor yaitu varietas dan dosis pupuk Urea. Varietas sebagai petak utama terdiri dari varietas Bisma dan Pioneer 27. Dosis pupuk Urea sebagai anak petak terdiri dari dosis 0, 150, 300, 450, dan 600 kg ha-1. Penelitian menunjukkan dosis pupuk Urea berpengaruh nyata terhadap pertumbuhan dan produksi jagung. Peningkatan dosis pupuk Urea sampai 600 kg ha-1 secara linear nyata meningkatkan bobot kering biomassa, bobot tongkol berkelobot, bobot tongkol, diameter tongkol, bobot biji per tongkol, dan produktivitas. Tinggi tanaman, jumlah daun, dan panjang tongkol menunjukkan respon kuadratik terhadap dosis pupuk Urea dengan rata-rata dosis optimum adalah 417,30 kg ha-1. Terdapat korelasi positif nyata antara peubah tinggi tanaman, jumlah daun, panjang tongkol, dan produktivitas sehingga aplikasi pupuk Urea dengan dosis 450 kg ha-1 adalah yang paling mendekati optimum dan dapat direkomendasikan untuk kedua varietas. Aplikasi pupuk Urea dengan dosis 600 kg ha-1 atau lebih dapat dimanfaatkan untuk produksi jagung untuk pakan ternak., Maize is an important commodity in Indonesia whose demand continues to increase so that its productivity needs to be increased by using quality seeds and balanced fertilization. This study investigates the effect of Urea fertilizer dosage and varieties on the growth and production of maize. The experiment used a split-plot design in a completely randomized group design. The treatment consisted of 2 factors, variety and dose of Urea fertilizer. Varieties as the main plot consisted of Bisma and Pioneer 27. The doses of Urea fertilizer as sub-plots consisted of doses of 0, 150, 300, 450, and 600 kg ha-1. The results showed that the dose of Urea fertilizer had a significant effect on the growth and yield of maize. Increasing the dose of Urea fertilizer up to 600 kg ha-1 linearly significantly increased biomass dry matter, ear weight with husk, ear weight, ear diameter, seed weight per ear, and yield. Plant height, number of leaves, and ear length showed a quadratic response to the dose of Urea fertilizer with an average optimum dose of 417,30 kg ha-1. There is a significant positive correlation between the variables of plant height, number of leaves, ear length, and yield so that the application of Urea fertilizer at a dose of 450 kg ha-1 is the closest to the optimum and could be recommended for both varieties. Urea fertilizer application with a dose of 600 kg ha-1 or more can be used for maize production for animal feed.
Keyword: Bisma, dosis optimum, pakan ternak, Pioneer 27, produksi, animal feed, optimum dose, yield

Judul: The Effect of Urea Fertilization and Varieties on Maize (Zea mays L.) Plants in Terms of Biomass and Seed Production
Abstrak: Jagung merupakan tanaman pangan yang mempunyai peran strategis dalam pembangunan pertanian dan perekonomian nasional. Produktivitas jagung sangat ditentukan oleh mutu genetik varietas yang ditanam dan pemupukan yang tepat. Kegiatan penelitian ini bertujuan mengetahui pengaruh pemupukan berbagai dosis pupuk urea terhadap dua varietas jagung yang ditanam melalui produksi biomassa dan biji. Penelitian dilakukan pada Januari hingga Mei 2023 di Kebun Percobaan Leuwikopo Departemen Agronomi dan Hortikultura, Institut Pertanian Bogor, Dramaga, Bogor, Jawa Barat. Penelitian dilaksanakan menggunakan rancangan petak terbagi dalam rancangan kelompok lengkap teracak dengan tiga kali ulangan. Perlakuan terdiri dari 2 faktor yaitu varietas dan dosis pupuk urea. Varietas sebagai petak utama dan dosis pupuk urea sebagai anak petak. Dua varietas jagung, BISI 18 (hibrida) dan Bisma (komposit) ditanam dan dipupuk dengan dosis urea 0, 175, 350, dan 525 kg ha-1 . Peningkatan dosis urea hingga 525 kg ha-1 secara linier meningkatkan total bobot kering, bobot tongkol dengan kelobot, bobot tongkol tanpa kelobot, diameter tongkol, bobot biji per tongkol, dan bobot biji per plot. Tinggi tanaman, jumlah daun, diameter batang, panjang tongkol, dan nilai SPAD menunjukkan respon kuadratik dengan dosis urea optimum masing-masing 461,25, 435, 350, 435 dan 518 kg ha-1 . Dosis urea 439,25 kg ha-1 merupakan dosis optimum untuk mencapai produktivitas tinggi pada kedua varietas tersebut., Maize is a food crop that has a strategic role in the development of agriculture and the national economy. Maize productivity is largely determined by the genetic quality of the varieties planted and proper fertilization. This research activity aims to determine the effect of fertilizing various doses of urea fertilizer on two varieties of corn grown through the production of biomass and seeds. The research was conducted from January to May 2023 at the Leuwikopo Experimental Garden, Department of Agronomy and Horticulture, IPB University, Dramaga, Bogor, West Java. The research used a split-plot design in a completely randomized group design with three replications. The treatment consisted of 2 factors, variety and dose of urea fertilizer. The variety is the main plot and the dosage of urea fertilizer is the sub-plot. Two maize varieties, BISI-18 (hybrid) and Bisma (composite) were grown and fertilized with urea doses of 0, 175, 350, and 525 kg ha-1 . The increasing urea dose up to 525 kg ha-1 linearly increased the total dry weight, ear weight with husks, ear weight without husk, ear diameter, seed weight per ear, and weight of seed per plot. Plant height, number of leaves, stem diameter, cob length, and SPAD values showed a quadratic response with optimum urea doses of 461.25, 435, 350, 435, and 518 kg ha-1 , respectively. The urea dose of 439.25 kg ha-1 is the optimum dose to achieve high productivity for both varieties.
Keyword: ear weight, ear diameter, optimum dose, productivity, total dry weight

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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