Judul: Pengaruh Pemupukan Nitrogen Terhadap Fisiologi Dan Karakter Laju Pengisian Biji Beberapa Varietas Kedelai
Abstrak: Soybean is one of the main agricultural commodities in Indonesia. It seen from the high national demand. High demand is not accompanied by high national production, as a consequence the volume of imports is still high to meet national requirment. The large number of imports must be responded with various efforts to increase the productivity of soybean plants, one of them is by optimizing fertilization technology through studying the important role of essential nutrients in order to get optimal crop production. Nitrogen is needed by plants in large quantities. N affects the rate of single leaf photosynthetic capacity associated with size of leaf area. The rate of photosynthesis increases the production of dry matter plants, dry matter plants will be a source for seed development. Productivity is the yield of seeds per unit area of land. Seed weight is affected by the rate of seed filling per unit time during the seed filling period. This study aims to see how the characteristics of seed filling rate of varieties that have different seed sizes and the effect of N in the rate of seed fillings of plants. The study was conducted from July to November 2019 in the Cikabayan experimental station, Bogor. The experimental design used was a randomized complete group design (RCBD) with a dose factor of urea (0 and 50 kg ha-1) and soybean varieties with different seed sizes (Tanggamus, Anjasmoro, Grobogan, Biosoy 1) with two replications. The laboratories used were the Postharvest Laboratory of the Department of AGH IPB and PAU FATETA LAB IPB. The seed filling rate for each variety has a pattern that is increased towards the end of the filling phase except for Biosoy 1. Increased seed filling rate is followed by remobilization of assimilate (dry matter) and N from the canopy to the seeds. Dry matter remobilization has a positive correlation with N which is remobiliated from the canopy. Seed size does not have a correlation to the rate of seed filling, although at the beginning of filling each seed has a significantly different rate. N dose given to plants does not significantly influence the rate of seed filling. N dose influences the amount of N to be mobilized but does not affect the dry matter that could mobilized.
Keyword: N translocation, net assimilation rate, non-structural carbohydrates, rate of growth, seed filling rate

Judul: Seed Filling Characteristics of several Rice Varieties at Low and Optimum Nitrogen
Abstrak: Hasil tanaman padi yang bisa didapatkan dari masing-masing varietas berbeda-beda. Setiap varietas memiliki karakteristik pertumbuhan dan hasil yang berbeda, termasuk karakteristik pengisian bijinya. Hal ini dipengaruhi oleh genetik, lingkungan dan interaksi keduanya. Salah satu keadaan lingungan yang sangat berpengaruh terhadap pertumbuhan dan hasil tanaman padi adalah keberadaan nitrogen. Nitrogen merupakan unsur yang dibutuhkan dalam jumlah yang cukup banyak. Namun ketersediaannya bagi tanaman sedikit sehingga sering menjadi faktor pembatas pertumbuhan sehingga pemupukan nitrogen diperlukan dalam praktik budidaya. Tidak hanya mempengaruhi pertumbuhan dan perkembangan tanaman, tapi juga berperan dalam tinggi rendahnya hasil tanaman padi. Penelitian ini bertujuan untuk memperoleh informasi tentang karakteristik pengisian biji beberapa varietas padi dalam dua kondisi N yang berbeda (N rendah dan N optimum). Penelitian ini dilakukan di lahan persawahan di Desa Petapahan, Kabupaten Kampar, Riau. Rancangan percobaan yang digunakan adalah split plot rancangan acak kelompok dengan 2 faktor dan 3 kelompok. Faktor pertama sebagai petak utama adalah kondisi N. Terdapat 2 taraf pada faktor ini yaitu N rendah (0 kg ha-1 urea) dan N optimum (250 kg ha-1 urea). Kemudian faktor kedua sebagai anak petak adalah varietas, yang terdiri dari 4 taraf yaitu Hipa 18, IPB 3S, Ciherang, dan Way Apo Buru. Hasil penelitian meunjukkan adanya penurunan bobot kering batang dan daun pada semua varietas dan kondisi N yang mengindikasikan terjadinya remobilisasi asimilat dari bagian tersebu ke biji. Penurunan bobot kering batang dan daun terbesar terjadi pada varietas Hipa 18 di semua ontogeni tanaman yang diamati (inisasi malai, heading, heading+20 hari, dan panen), hal ini mengindikasikan terjadinya remobilisasi asimilat dalam jumlah yang paling besar pada varietas tersebut. Selain itu Hipa 18 juga memiliki penurunan kandungan N daun yang terbesar pada inisiasi malai menuju heading. Penurunan yang paling besar ini menunjukkan adanya penggunaan N yang lebih besar untuk pembentukan dan perkembangan malai pada varietas tersebut. Karakter tanaman yang mempengaruhi hasil tanaman padi adalah bobot kering tanaman, luas daun, laju fotosintesis, kehijauan daun, dan kandungan N daun.
Keyword: asimilat, fotosintesis, karbohidrat, nitrogen, remobilisasi

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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