Judul: Effect of Subsurface Plastic Mulch Application on Growth and Production of Four Soybean Varieties
Abstrak: Kedelai merupakan salah satu komoditas pangan penting yang dapat diolah menjadi tahu, tempe, susu kedelai, dan kecap. Peningkatan produksi kedelai dapat dilakukan dengan perluasan areal tanam dan peningkatan produktivitas. Peningkatan produktivitas dapat dilakukan dengan pemberian air yang cukup bagi tanaman. Penelitian ini bertujuan mendapatkan informasi mengenai pengaruh mulsa plastik bawah tanah terhadap pertumbuhan dan produksi empat varietas kedelai. Penelitian dilakukan di Kebun Percobaan IPB Sawah Baru dari bulan Januari hingga Mei 2021. Percobaan menggunakan rancangan petak terbagi dengan tiga ulangan. Petak utama yaitu mulsa plastik bawah tanah dan tanpa mulsa plastik bawah tanah serta anak petak yaitu kedelai varietas Detam-1, Gepak Kuning, Grobogan, dan Anjasmoro. Hasil penelitian menunjukkan bahwa perlakuan mulsa plastik bawah tanah dapat meningkatkan kelembapan tanah, tinggi tanaman, jumlah daun trifoliate, jumlah cabang, dan indeks luas daun. Gepak Kuning merupakan varietas yang menghasilkan jumlah polong, jumlah polong isi, jumlah biji, jumlah biji per polong, dan produksi riil yang lebih tinggi dibandingkan varietas lainnya. Detam-1 memiliki jumlah polong hampa, persentase polong hampa, bobot basah polong hampa, dan evapotranspirasi yang lebih tinggi dibandingkan varietas lainnya. Anjasmoro dan Gepak Kuning memiliki nilai efisiensi pemakaian air yang lebih tinggi dibandingkan dua varietas lainnya., Soybean is one of important food commodities that can be processed into tofu, tempe, soy milk, and soy sauce. Soybean production can increase by expanding the planting area and increasing productivity. Increased productivity can be done by providing sufficient water for plants. This research aimed to study the effect of subsurface plastic mulch application on growth and production of four soybean varieties. This research was conducted in Teaching Farm Sawah Baru IPB from January to May 2021. This research used split plot design with three replications. The main plot was subsurface plastic mulch, non-subsurface plastic mulch and the sub plot was soybean varieties (Detam-1, Gepak Kuning, Grobogan, and Anjasmoro). The results showed that subsurface plastic mulch increased soil moisture, plant height, number of trifoliate leaves, number of branches, and leaf area index. Gepak Kuning variety has the higher number of pods, number of filled pods, number of seeds, number of seeds per pod, and real production compared to other varieties. Detam-1 has higher number of empty pods, percentage of empty pods, wet weight of empty pods, and evapotranspiration compared to other varieties. Anjasmoro and Gepak Kuning have a higher water use efficiency value than other two varieties.
Keyword: gepak kuning, leaf area index, moisture

Judul: The Effect of Doses of Phosphorus and Potassium Fertilizers on the Growth and Production of Soybean (Glycine max (L.) Merrill)
Abstrak: Kedelai merupakan salah satu komoditas prioritas yang diupayakan untuk ditingkatkan produksinya guna mengurangi impor. Upaya peningkatan produksi nasional kedelai di antaranya perbaikan teknik budi daya melalui pengaturan pupuk. Pupuk fosfor (P) dan kalium (K) menjadi salah satu pupuk dasar yang dibutuhkan untuk budi daya kedelai. Penelitian ini bertujuan mendapatkan informasi mengenai pengaruh dosis pupuk P dan K terhadap pertumbuhan dan produksi kedelai. Penelitian dilakukan di Kebun Percobaan IPB Sawah Baru dari bulan September hingga Desember 2021. Percobaan menggunakan rancangan kelompok lengkap teracak (RKLT) dengan dua faktor percobaan, yakni dosis pupuk P (0, 50, 100, dan 150 kg SP-36 ha-1) dan dosis pupuk K (0, 100, dan 150 kg KCl ha-1). Varietas yang digunakan adalah Anjasmoro. Hasil penelitian menunjukkan pemberian pupuk P mempercepat umur panen serta menaikkan indeks luas daun, nilai kehijauan daun fase R1, bobot kering tajuk, laju pertumbuhan tanaman fase R5−R8, bobot biji per tanaman, bobot ubinan, dan potensi hasil kedelai. Dosis 150 kg SP-36 ha-1 menghasilkan bobot biji per tanaman, bobot ubinan, dan potensi hasil tertinggi dibanding dosis lainnya. Hasil panen perlakuan pupuk P 100 kg SP-36 ha-1 dan 150 kg SP-36 ha-1 melampaui potensi hasil varietas. Pemupukan K memperpanjang fase pengisian polong (R5) dan meningkatkan tinggi tanamana pada 9 MST, bobot kering tajuk, bobot biji per tanaman, bobot 100 butir, bobot ubinan, dan potensi hasil kedelai. Dosis 150 kg KCl ha-1 menghasilkan komponen produksi kedelai tertinggi dibanding dosis lainnya., Soybean is one of the priority commodity which production is being increased in order to reduce imports. Efforts to increase national soybean production by improving cultivation techniques through fertilizer regulation. Phosphorus (P) and potassium (K) fertilizers are one of the basic fertilizers needed for soybean cultivation. This research aims to obtain information on the effect of doses of P and K fertilizers on soybean growth and production. The research was conducted at Sawah Baru Experimental Field and Post-harvest Laboratory of IPB University from September to December 2021. This research used a randomized complete block design (RCBD) with two experimental factors, the dose of P fertilizer (0, 50, 100, and 150 kg SP-36 ha-1) and the dose of K fertilizer (0, 100, and 150 kg KCl ha-1). Variety used was Anjasmoro. The results showed that the application of P fertilizer accelerated harvest age and increased leaf area index, leaf greenness in R1 phase, culm and leaf dry weight, rate of plant growth in R5−R8 phase, weight of seeds per plant, tile weight, and soybean yield potential. A dose of 150 kg SP-36 ha-1 produced the highest weight of seeds per plant, tile weight, and yield potential compared to other doses. The yields of fertilizer treatments of P 100 kg SP-36 ha-1 and 150 kg SP-36 ha-1 exceeded the yield potential of the variety. K fertilization extended age of pods filling (R5) and increased plant height at 9 WAP, culm and leaf dry weight, weight of seeds per plant, weight of 100 seeds, tile weight, and soybean yield potential. The dose of 150 kg KCl ha-1 resulted in the highest soybean production component compared to other doses.
Keyword: age of pods filling, culm and leaf dry weight, harvest age, seed weight, yield potential

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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