Judul: Utilization of Weatherable Organik Materials for Improvement of Soil Physical Properties (Soil Permeability and Shear Strength)
Abstrak: Penurunan produktivitas pertanian di Indonesia umumnya disebabkan oleh terjadinya penurunan kualitas tanah akibat penggunaan tanah secara terus-menerus. Penurunan produktivitas juga dialami oleh PT Great Giant Pineapple (GGP) sejak 2018. Hal tersebut terjadi karena kandungan bahan organik yang rendah dan terjadinya pemadatan tanah. Pemadatan tanah dapat diatasi dengan pemberian bahan organik. Pemberian bahan organik sering mengalami kendala akibat residence time-nya yang relatif singkat terutama untuk tanaman berumur panjang seperti nanas. Salah satu alternatif adalah dengan memanfaatkan limbah ekstraksi bromelain yang tersedia. Penelitian ini bertujuan mengidentikasi pengaruh aplikasi limbah ekstraksi bromelain dan bambu cacah berbagai dosis terhadap proses agregasi, kekuatan geser tanah dan permeabilitas tanah. Penelitian dilakukan di lokasi 88 C2 Kebun PT GGP, Lampung Tengah dengan metode rancangan acak kelompok (RAK) faktorial. Tanah dengan perlakuan limbah ekstraksi bromelain memiliki indeks stabilitas agregat tanah yang lebih tinggi dibandingkan tanah dengan perlakuan bambu cacah. Laju permeabilitas tanah mengalami penurunan pada 5 bulan setelah aplikasi bahan organik baik pada limbah ekstraksi bromelain maupun bambu cacah. Pemberian bahan organik memicu pertumbuhan akar tanaman nanas sehingga meningkatkan nilai kekuatan geser tanah. Semakin tinggi dosis bahan organik yang diberikan maka semakin baik dampaknya terhadap sifat fisik tanah., The decline in agricultural productivity in Indonesia is generally caused by a decrease in soil quality due to continuous land use. PT Great Giant Pineapple (GGP) has also experienced a decline in productivity since 2018. This is due to the low organik matter content and soil compaction. Soil compaction can be overcome by adding organik matter. The application of organik matter often experiences problems due to its relatively short residence time, especially for long-lived plants such as pineapple. One alternative is to utilize the available bromelain extraction waste. This study aims to identify the effect of the application of bromelain extraction waste and various doses of chopped bamboo on the aggregation process, soil shear strength and soil permeability. The research was conducted at location 88 C2 of PT GGP's plantation, Central Lampung with a factorial randomized block design (RBD) method. Soil treated with bromelain waste extraction had a higher soil aggregate stability index than soil treated with chopped bamboo. The rate of soil permeability decreased 5 months after the application of organik matter in both bromelain extraction waste and chopped bamboo. The application of organik matter triggers the growth of pineapple plant roots thereby increasing the shear strength value of the soil. The higher the dose of organik matter given, the better the impact on soil physical properties.
Keyword: aggregate stability, bromelain, residence time, soil compaction

Judul: Permeability and Shear Strength of PT GGP Pineapple Land after Eleven Months of Resistant Organic Matter Application
Abstrak: Penurunan produktivitas pertanian pada umumnya disebabkan oleh penurunan kualitas tanah akibat penggunaan terus-menerus. Penelitian ini dilakukan pada lahan PT Great Giant Pineapple (GGP) yang mengalami penurunan produktivitas buah nanas seiring terjadinya penurunan kualitas tanah. Penurunan kualitas tanah terjadi karena rendahnya pemberian bahan organik yang sesuai dengan usia tanaman nanas, sehingga mengakibatkan pemadatan tanah. Dalam penelitian ini, limbah ekstraksi bromelain dan bambu cacah dipilih sebagai sumber bahan organik tahan lapuk karena mampu mempertahankan residence time pada pengaplikasian nya di lahan. Tujuan penelitian adalah menguji pengaruh bahan organik tahan lapuk setelah 11 bulan aplikasi terhadap permeabilitas dan kuat geser tanah. Metode penelitian yang digunakan adalah rancangan acak kelompok (RAK) di lokasi lahan 88 C2, PT GGP, Lampung Tengah. Hasil penelitian menunjukkan bahwa perlakuan limbah ekstraksi bromelain menghasilkan nilai laju permeabilitas yang lebih rendah dibandingkan dengan perlakuan bambu cacah. Laju permeabilitas pada kedua perlakuan mengalami penurunan setelah 11 bulan aplikasi bahan organik dibandingkan dengan setelah aplikasi 5 bulan. Nilai Kekuatan geser tanah meningkat seiring bertambahnya usia tanaman pada bulan 11, terutama pada kedalaman 0-10 cm, 10-20 cm, dan 20-30 cm. Pemberian dosis bahan organik yang lebih tinggi memberikan perbaikan sifat fisik tanah yang lebih baik., The decline in agricultural productivity is generally caused by a decrease in soil quality due to continuous use. This research was conducted on PT Great Giant Pineapple (GGP)’s land which experienced a decrease in pineapple productivity along with a decrease in soil physical quality. The decline in soil quality occurred due to the low provision of organic matter in accordance with the age of pineapple plants, resulting in soil compaction. In this study, bromelain extraction waste and chopped bamboo were chosen as a source of resistant organic matter since they are able to maintain quite long residence time in land after application. The research objective was to examine the effect of resistant organic matter after 11 months of application on permeability and soil shear strength. The research was held based on Randomized Block Design (RBD) at the location of 88 C2 land of PT GGP, Central Lampung. The results showed that the bromelain extraction waste treatment produced a lower permeability rate than the chopped bamboo treatment. The permeability rate in both treatments decreased after 11 months of organic matter application compared to the 5 months of application. Soil shear strength values increased with plant age of month 11, especially at depths of 0-10 cm, 10-20 cm, and 20-30 cm. Application of higher doses of resistant organic matter provided better improvements in soil physical properties.
Keyword: bromelain, organic matter, permeability, shear strength

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.
Keyword: