Judul: Association of Culture Techniques to Major Diseases on Paddy Rice in Gandrungmangu District Cilacap Regency, Central Java
Abstrak: Beras merupakan makanan utama sebagian besar penduduk di Benua Asia, termasuk Indonesia. Penurunan produksi padi salah satunya dipengaruhi oleh penyakit tanaman. Penyakit tanaman dapat menyerang pada berbagai fase tanaman. Penelitian bertujuan mempelajari hubungan teknik budi daya yang diterapkan petani terhadap keparahan penyakit penting padi di Kecamatan Gandrungmangu, Kabupaten Cilacap. Data diperoleh dari wawancara langsung dengan kuisioner terstruktur kepada petani dan pengamatan insidensi serta keparahan penyakit di lapangan. Pengolahan data dilakukan dengan metode statistika analisis tabulasi silang dan uji chi-square. Hawar daun bakteri (HDB) menjadi penyakit utama pada fase vegetatif, diikuti oleh blas, kemudian bercak coklat sempit. HDB masih menjadi penyakit utama pada fase generatif, diikuti bercak coklat sempit, lalu blas. Keparahan ketiga penyakit tersebut meningkat dari fase vegetatif ke fase generatif. Frekuensi penggunaan pestisida dan metode pengendalian gulma berhubungan dengan keparahan penyakit HDB. Aplikasi herbisida sebagai metode pengendalian gulma membuat keparahan penyakit HDB semakin besar. Varietas, dosis pupuk nitrogen dan rotasi tanam berhubungan dengan keparahan penyakit blas. Pemakaian pupuk N yang berlebihan mengakibatkan keparahan penyakit blas semakin besar.
Keyword: bacterial leaf blight, blast, cultivation, narrow brown leaf spot, paddy rice

Judul: Disease Incidence and Severity of Blast (Pyricularia  oryzae) and Bacterial Leaf Blight (Xanthomonas oryzae pv. oryzae) on Rice  Plants in Gebang and Kuripan Villages, Pekalongan City, Central Java
Abstrak: Padi adalah sumber pangan penting bagi masyarakat di dunia terutama masyarakat Indonesia. Peningkatan produktivitas padi memiliki beberapa kendala seperti adanya penyakit tanaman. Terdapat dua penyakit penting padi di Indonesia yaitu blas (Pyricularia oryzae) dan hawar daun bakteri (Xanthomonas oryzae pv. oryzae). Penelitian ini bertujuan mengukur tingkat insidensi dan keparahan penyakit blas dan hawar daun bakteri pada tanaman padi di Kota Pekalongan, Jawa Tengah. Pengamatan di lapangan dilakukan pada 5 petak contoh di Desa Gebang dan 5 petak di Desa Kuripan. Pengamatan juga dilakukan terhadap bobot 1000 butir gabah kering panen dari tanaman contoh. Selain pengamatan di lapangan juga dilakukan wawancara dengan petani. Di Desa Gebang varietas yang ditanam adalah Varietas Inpari 43, sedangkan di Desa Kuripan ditanam varietas Inpari 42. Hasil penelitian menunjukkan bahwa serangan P. oryzae dan X. oryzae pv. oryzae ditemukan pada semua petak pengamatan. Keparahan penyakit blas pada lahan pengamatan di Desa Gebang relatif lebih tinggi (rata-rata 51.11%) dibandingkan dengan lahan pengamatan di Desa Kuripan (rata-rata 25.55%). Keparahan penyakit HDB pada lahan Desa Gebang juga relatif lebih tinggi (rata- rata 92%) dibandingkan dengan lahan pengamatan di Desa Kuripan (rata-rata 60.44%), Rice is an important crops as staple food in Indonesia. Increasing rice productivity has an important constraint such as plant diseases. Two important rice diseases in Indonesia are blast (Pyricularia oryzae) and bacterial leaf blight (Xanthomonas oryzae pv. oryzae). This study was aimed to measure the incidence and severity of blast and bacterial leaf blight diseases on rice plants in Pekalongan City, Central Java. As many as 5 sample plots of rice fields each in Gebang Village and Kuripan Village were observed. Observations were also carried out on the weight of 1000 dry-harvested grains from the sample plants. In Gebang plots were grown Inpari 43 variety, while in Kuripan plots were grown Inpari 42 variety. This study has shown that blast and bacterial leaf blight disease were observed in all observation plots. The severity of blast disease in the observation plots in Gebang Village was relatively higher (51.11%) than Kuripan Village (25.55%). Similarly BLB disease severity in Gebang Village was higher (92%) than in Kuripan Village (60.44%)
Keyword: Grain, Inpari 42, Inpari 43, Plots, Rice diseases

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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