Judul: The Difference in Weed Dominance in Various Years of Pruning in Tea Plant (Camellia sinensis L. (O.) Kuntze) at Wonosari, PTPN XII, Malang
Abstrak: PTPN XII Kebun Wonosari merupakan perusahaan perkebunan negara yang memiliki kebun teh seluas 549,72 ha. Kegiatan magang dilaksanakan di Kebun Wonosari pada bulan Januari–April 2021. Tujuan magang meningkatkan pengalaman dan keterampilan secara teknis dan manajerial serta menganalisis sistem perbedaan dominansi gulma berbagai umur pangkas. Pengamatan meliputi perbedaan dominansi gulma setiap afdeling, manajemen struktur pengendalian gulma, metode pengendalian gulma, alat pengendalian gulma, jenis herbisida, dosis herbisida, waktu aplikasi herbisida, efisiensi metode pengendalain gulma, tenaga kerja penyemprotan herbisida, dan laju penutupan gulma setelah semprot. Hasil pengamatan menunjukkan gulma dominan di Kebun Wonosari yaitu (Peperomia pellucida (L.) Kunth) dan (Borreria alata L.). Koefisien komunitas setiap afdeling pada berbagai umur pangkas cenderung heterogen. Metode pengendalian gulma secara kimiawi lebih efisien dibandingkan dengan manual. Laju penutupan gulma setelah semprot meningkat karena biji gulma terus tumbuh., PTPN XII Wonosari plantation is a state-owned plantation company that has 549.72 ha of tea plantation. The apprenticeship was performed in Wonosari plantation from January to April 2021. The apprentice aims are to improve the technical and managerial experience and skills as well as to analyzes the differences of weed dominance at various prune ages. The observations included the difference of weed dominance for each afdeling, the management of weeds control structure, the weeds control method, the weeds control tools, the herbicides, the dose of herbicides, the time of herbicide application, the efficiency of the weeds control method, the labor of herbicide spraying, and the weeds cover rates after spraying. The result showed that there were two dominant weed species in Wonosari plantation, which are (Peperomia pellucida L) and (Borreria alata L.). The community coefficient of every afdeling on a variety of prune ages tends to be heterogeneous. The method was chemically more efficient compared to the manual for controlling the weeds. The rate of weeds covering after spraying increased as the weed seeds keep growing.
Keyword: community coefficient, crop age, cover rate, weed dominance

Judul: Weeds Dominance According to the Pruning Years of Tea Plant (Camellia sinensis (L) O. Kuntze) at Negara Kanaan Tea Plantation, PT Ratnapura Bianka, Bandung
Abstrak: Budidaya tanaman teh tidak lepas dari keberadaan gulma. Dominansi gulma berdasarkan tahun pangkas perlu diketahui agar pengendalian gulma terlaksana dengan efektif. Kegiatan magang bertujuan menganalisis dominansi gulma menurut tahun pangkas tanaman teh. Hasil pengamatan menunjukkan bahwa gulma dominan yang tumbuh pada TP 1 dan TP 2 didominasi Oplismenus hirtellus sedangkan TP 3, 4, dan 5 didominasi Ageratum conyzoides. Nilai koefisien komunitas antar tahun pangkas kurang dari 70%, sehingga vegetasi gulma bersifat heterogen. Pengelolaan kerja pengendalian gulma berprinsip POACE. Pengendalian gulma dilaksanakan dengan metode manual menggunakan sabit dan kimiawi menggunakan knapsack sprayer. Herbisida yang digunakan berbahan aktif Isopropilamina glifosat dengan dosis antara 1,61-2,50 l ha-1. Pengendalian gulma kimiawi dilaksanakan dengan rotasi 3-6 bulan. Pekerja pengendalian gulma kimiawi dapat menyelesaikan 0,4 ha HK-1 pada TP 1 dan 0,5 ha HK-1 pada TP 2 hingga TP 4. Pekerja pengendalian gulma belum mematuhi kelengkapan APD yang ditetapkan perusahaan. Biaya pengendalian gulma pada TP 1 hingga TP 4 berkisar antara Rp541.971 hingga Rp1.004.928. Keberagaman gulma setiap tahun pangkas mempengaruhi kegiatan pengelolaan kerja pengendalian gulma secara umum., The cultivation of tea plants cannot be separated from the presence of weeds. Weed dominance by year of pruning needs to be known so that weed control is carried out effectively. The internship activity aims to analyze the dominance of weeds by year of pruning of tea plants. The results showed that the dominant weeds growing in TP 1 and TP 2 were dominated by Oplismenus hirtellus, while TP 3, 4, and 5 were dominated by Ageratum conyzoides. The community coefficient value between pruning years is less than 70%, so the weed vegetation is heterogeneous. Weed control work management is based on the POACE principle. Weed control is carried out manually using a sickle and chemically using a knapsack sprayer. The herbicide used as an active ingredient is Isopropylamine glyphosate with a dose between 1.61-2.50 l ha-1. Chemical weed control is carried out with a rotation of 3-6 months. Chemical weed control workers can complete 0.4 ha HK-1 at TP 1 and 0.5 ha HK-1 at TP 2 to TP 4. Weed control workers have not complied with the completeness of PPE set by the company. Weed control costs in TP 1 to TP 4 ranged from Rp. 541,971 to Rp. 1,004,928. The diversity of weeds each year affects weed control work management activities in general.
Keyword: Ageratum conyzoides, cost efficiency, herbicide, Oplismenus hirtellus, PPE

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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