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: Effect of Organic Fertilizer on Evapotranspiration, Water Use Efficiency, Growth and Yield of Red Spinach (Amaranthus tricolor) and Water Spinach (Ipomoea reptans)
Abstrak: Pemenuhan permintaan tanaman hortikultura dapat dilakukan melalui peningkatan produksi dengan mengetahui faktor iklim khususnya curah hujan, evapotranspirasi, serta kadar air tanah. Peningkatan produktivitas juga dapat dilakukan dengan pemberian pupuk organik pada tanaman. Penelitian bertujuan mengetahui pengaruh pupuk organik terhadap evapotranspirasi, efisiensi pemakaian air, pertumbuhan, dan hasil bayam merah (Amaranthus tricolor) dan kangkung (Ipomoea reptans). Percobaan dilakukan pada tanaman bayam merah dan tanaman kangkung secara terpisah. Kedua percobaan disusun dengan Rancangan Acak Kelompok (RAK) yang terdiri dari 3 perlakuan, yaitu tanpa pupuk: 0 ton ha-1 (P1), pupuk kandang: 10 ton ha-1 (P2) dan pupuk kompos organik: 10 ton ha-1 (P3) dengan 3 ulangan. Hasil penelitian menunjukkan bahwa pemberian perlakuan pupuk pada bayam merah memberikan pengaruh terhadap tinggi tanaman, jumlah daun, panjang akar, panjang daun, koefisien evapotranspirasi, kebutuhan air tanaman, serta efisiensi pemakaian air. Bobot segar tanaman bayam tertinggi yaitu 1866,7 g/3m2 dengan perlakuan pemberian pupuk kandang. Perlakuan pupuk pada kangkung berpengaruh pada tinggi tanaman, bobot segar sampel, bobot kering sampel, efisiensi pemakaian air, kadar air tanah. Pemberian pupuk organik juga memberikan pengaruh pada berat basah dan berat kering, khususnya pemberian pupuk kandang yang memiliki bobot segar paling tinggi yaitu 2166,7 g/3m2., Fulfilling the demand for horticultural crops can be done through increasing production by knowing climatic factors, especially rainfall, evapotranspiration, and soil water content. Increased productivity can also be done by applying organic fertilizer to plants. Research aims determine the effect of organic fertilizer on evapotranspiration, water use efficiency, growth, and yield of red spinach (Amaranthus tricolor) and water spinach (Ipomoea reptans). The experiment was carried out on red spinach and water spinach separately. Both experiments were arranged in a Randomized Block Design (RBD) consisting of 3 treatments, namely without fertilizer:0 ton ha-1 (P1), manure: 10 ton ha-1 (P2), and organic compost: 10 ton ha-1 (P3) with 3 replicates. The results showed thatfertilizer treatment on red spinach has an effect on plant height, number of leaves, root length, leaf length, evapotranspiration coefficient, plant water requirements, and water use efficiency. The highest fresh weight of spinach plants was 1866.7 g/3m2 with the treatment of manure. Fertilizer treatment on water spinach affects plant height, sample fresh weight, sample dry weight, water use efficiency, soil moisture content. The application of organic fertilizer also has an effect on the wet weight and dry weight, especially the application of manure which has the highest fresh weight of 2166.7 g/3m2.
Keyword: Compost, Evapotranspiration, Growth, Manure, 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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