Judul: Factors Affecting Pepper Production in Indonesia
Abstrak: Lada sebagai komoditas unggulan sub-sektor perkebunan Indonesia, dihadapi oleh rendahnya produktivitas lada yang disebabkan karena perkembangan produksi lada secara nasional masih belum optimal dan mengalami penurunan. Dari segi usahatani lada, petani belum sepenuhnya memperhatikan pentingnya penggunaan sarana produksi terhadap hasil produksi. Dampak yang ditimbullkan adalah penurunan kuantitas hasil produksi lada yang dapat merugikan petani. Tujuan dari penelitian ini adalah untuk mengetahui keragaan usahatani lada di Indonesia dan menganalisis faktor-faktor yang memengaruhi produksi lada di Indonesia. Pada penelitian ini digunakan data Survei Rumah Tangga Perkebunan Tahun 2014 yang bersumber dari BPS. Metode yang digunakan adalah analisis deskriptif dan analisis regresi linier berganda menggunakan fungsi produksi cobbdouglas. Keragaan usahatani lada di Indonesia dalam satu tahun produksi dapat digambarkan dengan hasil produksi sebesar 0,66kg/pohon, kepemilikan jumlah pohon sebanyak 1.113, penggunaan tenaga kerja sebanyak 159 HOK, pupuk NPK sebanyak 122kg, pupuk urea sebanyak 154kg, pupuk organic sebanyak 82kg, pestisida sebanyak 11,4L, bibit tidak bersertifikat, dan pola tanam monokultur. Faktor-faktor yang berpengaruh positif dan signifikan terhadap produksi lada yaitu jumlah pohon, usia tanaman, tenaga kerja, pupuk NPK, pestisida, dan dummy pola tanam., Pepper as the leading commodity of the Indonesian plantation sub-sector, is faced by the low productivity of pepper caused by the development of pepper production nationwide is still not optimal and has decreased. In terms of pepper farming, farmers have not fully considered the importance of using production facilities to the yields. The resulting impact is a decrease in the quantity of pepper production that can harm farmers. The purpose of this study is to identify the business practices of pepper farming in Indonesia and analyze the factors affecting pepper production in Indonesia. The source data used in this study were from the 2014 Plantation Household Survey by BPS. The methods used are descriptive analysis and multiple linear regression analysis using the cobb-douglas production function. The production of pepper business in Indonesia can be described by 0.66 kg/tree production, ownership of 1,113 trees, labor use of 159 HOK, NPK fertilizer of 122 kg, urea fertilizer of 154 kg, organic fertilizer of 82 kg, pesticide of 11.4L, uncertified seeds, and monoculture cropping system. Factors that have a positive and significant effect on pepper production are the number of trees, age of plants, labor, NPK fertilizer, pesticides, and dummy cropping system.
Keyword: Cobb-douglas, Production factors, Pepper

Judul: Autekologi tanaman lada (Piper nigrum L.) di Provinsi Lampung: karakteristik lingkungan dan faktor yang mempengaruhi produktivitas
Abstrak: Understanding the characteristic of crop plant species is a pivotal step to achieve the cultivation success on agricultural practices. Each plant requires a specific environmental condition for its growth and maturation. In case of pepper plant, environmental factors such as altitude and rainfall considerably affect on the growth as well as productivity of this plant. As one of pepper production center in Indonesia, Lampung Province has diversity of pepper varieties and different environmental characteristic with gradient of altitude and precipitation. Based on Dinas Perkebunan (Plantation Office) of Lampung Province, productivity of pepper in Lampung tends to decrease recently. The average pepper production was 651 kg/ha in 2005, 478 kg/ha in 2007 and 461 kg/ha in 2011. Those, well-knowledge about autecology of pepper plant in Lampung Province become an important concern to solve the problems on pepper cultivation. The main objective of this research was to study the autecology of pepper plant in Lampung Province. The research covered specific objectives were (i) to obtain the information about phenology of pepper plant in Lampung Province, (ii) to determine the recent environmental condition of pepper plant habitat including biotic and abiotic factors, and (iii) to investigate the environmental factors that affect the productivity of pepper plant in Lampung Province. Study about phenology of pepper plant in Lampung was conducted through direct observation on selected plot in two areas i.e. (i) Kebun Percobaan Balittri, Cahaya Negeri Village, Subdistrict of Abung Barat, North Lampung and (ii) Kebun Percobaan BPTP, Negara Ratu Village, Subdistrict of Natar, South Lampung. Whereas, study about of environmental characteristics and its factors effect on the productivity of pepper plant was conducted in four districts with different altitude i.e. (i) Sekincau Subdistrict, West Lampung, (ii) Abung Barat Subdistrict, North Lampung, (iii) Margatiga Subdistrict, East Lampung, and (iv) Natar Subdistrict, South Lampung. Observation and measurement were conducted to obtain the data for environmental factors, variability and productivity of pepper plant. Analysis of soil chemistry was performed to determine the condition of soil fertility on each location. To study the biotic component, insects were explored as study case to investigate the relationship between insect and pepper plant. Then, statistical analyses were performed to study the relationship between environmental factors including abiotic and biotic factors and the productivity of pepper in Lampung Province. The result showed that the phenology of pepper plant in Lampung is started from the seed or cutting, seedling, immature, and adult. In the mature period, pepper plant having an annual cycle between vegetative and generative phase. Vegetative phase is started around September to December, while generative phase is from January to August. Flowering characteristic of pepper plant varieties i.e. Natar 1 and Natar 2 have seasonal flowering time which is early flowering time follow the rainy season in the local region. In Abung Barat, variety of Natar 1 has higher variability and productivity than Natar 2. In contrast, variability and productivity of Natar 2 was higher than Natar 1 in Natar Subdistrict. The difference of environmental condition might affect the productivity of pepper plant in Lampung Province. Environmental characteristic of pepper plant habitat
Keyword: autecology, environmental factor, Lampung Province, phenology, Piper nigrum

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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