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: Application of Pesticides in Pest and Disease Control and Harvest Product Management of Keprok Orange (Citrus reticulata L.) in Dau District, Malang Regency
Abstrak: Jeruk merupakan komoditas yang banyak digemari dan dikonsumsi oleh masyarakat di Indonesia. Jeruk keprok merupakan salah satu kultivar jeruk yang mudah dalam penanamannya, dapat tumbuh pada berbagai kondisi iklim dan dapat ditanam dimana saja, baik di dataran rendah maupun tinggi. Permasalahan yang sering dijumpai dalam setiap pertanaman yaitu adanya serangan hama dan penyakit. Penerapan sistem pengendalian OPT yang belum optimum menyebabkan penggunaan pestisida seringkali tidak tepat sasaran dan melebihi dosis anjuran sehingga berpengaruh pada keamanan konsumen buah jeruk. Penelitian ini bertujuan mengetahui pengetahuan, sikap, dan tindakan petani jeruk keprok dalam penggunaan pestisida, mengetahui hama dan penyakit utama, dan mengetahui tindakan yang dilakukan terhadap produk hasil panen. Penelitian dilakukan di Kecamatan Dau, Kabupaten Malang dengan metode survei langsung menggunakan kuisioner terstruktur. Responden ditentukan dengan menggunakan perpaduan metode purposive sampling dan snowball sampling. Sebanyak 50 petani responden (100%) menyatakan menggunakan pestisida sintetik untuk pertanaman jeruknya. Hama utama pada pertanaman jeruk keprok adalah lalat buah (Bactrocera spp.) (100%), kutu-kutuan (T. citricida, T. aurantii, A. gossypii) (92%), dan penyakit utama yaitu busuk pangkal batang yang disebabkan oleh P. nicotianae (86%). Pengetahuan, sikap, dan tindakan petani dalam penggunaan pestisida dipengaruhi oleh pengalaman bertani yang turun-temurun dan tingkat pendidikan. Jenis pestisida yang digunakan meliputi insektisida sistemik dan kontak, serta fungisida yang bersifat protektif. Organofosfat dan karbamat merupakan golongan pestisida yang paling banyak digunakan. Mayoritas responden (100%) langsung menjual hasil panennya yang menyebabkan kemungkinan adanya residu pada buah jeruk., Citrus is a perennial fruit plant that is consumed by many people of Indonesia. Keprok orange is one of the citrus cultivars that is easy to be cultivated, well grow in various climatic conditions and altitudes, either in the lowlands or in the highlands. Pests and diseases often cause the decrease of keprok orange quantitatively as well as qualitatively. The improper and exceed use of pesticides lead to negative effect citrus fruit consumers. This study aimed to determine the knowledge, attitudes, and practices in the application of pesticides, to determine the main pests and main diseases, and to determine the practice that taken on harvested products. The research was conducted in Dau District, Malang Regency through direct survey methods using structured questionnaires. Sampling of respondents used a combination of purposive sampling and snowball sampling methods. Based on the results of interviews, 50 respondent farmers (100%) used synthetic pesticides for their citrus plantations. The main pests of keprok orange plantations were fruit flies (Bactrocera spp.) (100%), aphids (Toxoptera citricida, T. aurantii, Aphis gossypii) (92%), and the main disease was stem rot caused by Phyrophthora nicotianae (86%). Farmer’s knowledge, attitudes, and practices in the use of pesticides are influenced by their experience and education level. The types of pesticides used include systemic and contact insecticides and protective fungicides. Organophosphates and carbamates are the most widely used pesticides. The majority of respondents (100%) directly sell their harvested products which led to the possibility of residue on citrus fruits.
Keyword: Keprok orange, Residues, Survey, Synthetic pesticide

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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