Judul: Effects of Plant Density and Nodes Cutting on Sweetpotato (Ipomoea batatas L.) Growth and Yield in Polybag in Context of Urban Farming
Abstrak: Ubi jalar (Ipomoea batatas L.) memiliki potensi dalam pertanian perkotaan. Stek mini dapat menurunkan kebutuhan bahan tanam. Kerapatan tanam yang lebih tinggi dapat meningkatkan efisiensi lahan. Penelitian ini bertujuan untuk menentukan jumlah buku bibit dan kerapatan tanam yang optimal bagi pertanian kota yang efisien. Penelitian dilakukan antara Mei - Oktober 2021 di Setu, Tangerang Selatan. Penelitian dirancang dengan split plot-rancangan kelompok lengkap teracak (SP-RKLT). Faktor pertama adalah jumlah buku bibit dengan taraf 2, 4, dan 6 buku. Faktor kedua adalah kerapatan tanam dengan 1, 2, dan 3 stek per polybag. Hasil menunjukkan bahwa bibit dengan buku yang lebih banyak memiliki pertumbuhan batang, daun, dan buku awal yang lebih baik sampai 8 MST. Perlakuan 1 stek per polybag memberikan pertumbuhan akhir individu tinggi namun perlakuan 2 dan 3 stek per polybag memberikan pertumbuhan per polybag dan hasil umbi yang paling tinggi., Sweet potato (Ipomoea batatas L.) has potential for efficient urban farming. Mini cutting can reduce plant material needs. High plant density can lead to more efficient land use. This research aims to deduce the most optimal node cutting and plant density for efficient urban farm. Research was done from May to October 2021 in Setu, Tangerang Selatan. This research is designed with split-plot randomized complete block design (SP-RCBD). First factor is node cutting with treatment 2, 4, and 6 node each cutting. Second factor is plant density with treatment 1, 2, and 3 cutting each polybag. Result shows that cutting with more node have better early growth until 8 weeks after planting. Plant density of 1 plant per polybag gives best individual plant late growth while 2 and 3 plant per polybag give better per polybag growth and tuber yield.
Keyword: jumlah buku bibit, kerapatan tanam, pertanian kota, polybag, ubi jalar, node cuttings, plant density, sweet potato, urban farming

Judul: The Growth and Tuber Yield of Sweetpotato (Ipomoea batatas L.) Ase Kapas at Various Rates of Nitrogen Fertilizer
Abstrak: Ubijalar merupakan tanaman pangan penting di Indonesia. Produktivitas ubijalar dapat dipengaruhi oleh pemupukan. Tujuan penelitian ini yaitu menentukan dosis nitrogen bagi pertumbuhan dan produksi ubijalar Ase Kapas. Penelitian dilakukan pada bulan Januari sampai Juli 2020 di Kebun Percobaan Cikabayan IPB dengan rancangan kelompok lengkap teracak dengan 3 ulangan. Dosis N yang diaplikasikan yaitu 0; 22,5; 45; 67,5; dan 90 kg ha-1 . Bahan tanam yang digunakan yaitu bagian stek pucuk. Curah hujan selama penelitian cenderung tidak sesuai dengan kondisi optimal pertumbuhan ubijalar. Pada tanah dengan kandungan nitrogen berstatus sedang (0,29% setara dengan 174 kg ha-1 ), dosis N tidak berpengaruh signifikan terhadap perubahan panjang dan diameter sulur, jumlah daun dan cabang, panjang dan diameter umbi, serta bobot basah dan kering umbi dan brangkasan. Pada tanah dengan kandungan N total sedang, dosis 0 kg N ha-1 dapat diaplikasikan untuk mendukung pertumbuhan dan produksi yang baik bagi ubijalar klon Ase Kapas., Sweetpotato is an essential crop plant in Indonesia. The productivity of the sweetpotato could be affected by fertilization. The objective of this research is to assess optimal nitrogen rate for growth and root yield of sweetpotato Ase Kapas. The experiment was conducted at IPB University experimental field Cikabayan from January to July 2020 used randomized complete block design with 3 replications. The level of nitrogen fertilizer consists of 0; 22,5; 45; 67,5; and 90 kg ha-1 . The planting material is the vine cuttings. The rainfall during this experiment tends to be insufficient as climate requirements. In the soil with moderate N content (0.29% equal to 174 kg ha-1 ), nitrogen had no significant effect on the growth of length and diameter of main stem, the amount of leaves and secondary stems, length and diameter of storage roots, wet- and dry-weight biomass of storage roots and aboveground part. In the soil with a moderate N total, dose of 0 kg N ha-1 could be applied to support good growth and yield of sweetpotato clone Ase Kapas.
Keyword: produktivitas, suplai nitrogen, umbi, Urea, nitrogen supply, storage root, productivity

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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