Judul: Pengukuran dan analisis trade-off jasa ekosistem untuk usaha perkebunan jeruk manis berkelanjutan di Selorejo, Kabupaten Malang
Abstrak: One of the biggest sweet orange fruits (Citrus sinensis L. Osbeck) production sites in Indonesia is located in Selorejo, Dau, Malang Regency. Currently, the site is however at risk of environmental degradation and constantly decreased. It is important for the development planning to improve production service without neglecting other services. This will reduce the risk of environmental changes and impacts on human welfare. This study aimed to analyze some ecosystem services and their trade-offs to create sustainable development planning for the orchards. The ecosystem service data was obtained from the interview with the sweet orange farmers and secondary data collection. Measurements of food production service used gross margin (GM) model and the orchards have GM of 12,465 IDR/m2. The biological control service is presented by the abundance of natural enemies on-site that are dominated by the Coccinellid and Formicidae families. But, the diversity of the pest and natural enemies is still considered low at 1.433 Shannon Wiener diversity index. The orchard also provided landslide prevention services as well as cultural and agrotourism services. In the carbon sequestration aspect, the orchard is leaning more to function as carbon stock. But the system can be shifted to function as a carbon sink with better management practice. We grouped the service into 2 bundles to determine their trade-offs: 1) food production-biological control-genetic diversity service bundle; and 2) moderation of extreme events-food provisioning bundle. To achieve a win-win condition and create sustainable agriculture practices on the sweet orange orchard, it is recommended for the farmer to reduce the intensive usage of chemical pesticides, use pruning biomass to make composts, use natural based pesticide, rejuvenate the root of 10 years old trees, use drip irrigation, and change the intercrops to flowering plants that would also boost the agrotourism potential.
Keyword: Ecosystem service, Sweet Orange, Sustainability, Trade-offs

Judul: Analisis Pendapatan Petani Jeruk (Cytrus sinensis L.) di Kecamatan Tigapanah Kabupaten Karo Sumatera Utara
Abstrak: Orange is one of the leading fruit commodity in Karo. Pest attacks causing crop failure, a decrease of the production and productivity, besides operating costs for farming activity is large. Selling price of oranges in 2013 is better than the previous year. This study aims to analyze the cost structure, income, efficiency of citrus farming. Analysis of the efficiency of farming is by analyzing the cost, revenue, income and analysis return cost ratio (R/C) and financial income and size of farming. Business scale having an effect on the income of farmers. The greater business scale give large income to the farmers. Age of plant have an effect on farmer’s income. The largest profit containt to 11-16 years old. The cost of cash farm are mostly used for the purchase of pesticides and chemical fertilizers and non cash incurred labour in family. Large scale of citrus farming is more efficient than another business scale with R/C 2.53 and citrus farming on old plant aren’t efficient than the other with R/C 1.46.
Keyword: income and R/C, cost structure, citrus farming, Bogor Agricultural University (IPB)

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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