Judul: Kajian Aplikasi Herbisida Sulfosat Tunggal serta Campurannya dengan Paraquat dan Metsulfuron Metil dalam Pengendalian Gulma Alang-alang
Abstrak: Penelitian ini bertujuan untuk mengetahui tingkat dosis herbisida yang efektif dari aplikasi sulfosat tunggal dan campuran sulfosat dengan paraquat maupun metsulfuron metil dalam mengendalikan gulma alang-alang. Penelitian dilakukan di Kecamatan Cigudeg, Jasinga, Kabupaten Bogor, Jawa Barat, dengan ketinggian tempat sekitar 360 m di atas permukaan laut, mulai bulan Juni hingga Oktober tahun 2000. Sebagai perlakuan digunakan herbisida sulfosat, paraquat, dan metsulfuron metil, untuk aplikasi pada alang-alang fase vegetatif yang tumbuh di lapang, pada petak percobaan berukuran 3 m x 5 m. Aplikator yang digunakan adalah knapsack sprayer tipe Solo, nozel kuning, dengan volume semprot 500 llha. Aplikasi dan pembabatan manual dilakukan pada alang-alang yang tumbuh setelah 18 hari sebelumnya dibabat sampai permukaan tanah.
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Judul: Aplikasi metsulfuron metil dan glifosat dengan menggunakan dua aplikator untuk pengendalian gulma pada jalur tanaman karet belum menghasilkan
Abstrak: Penelitian dilakukan di Perkebunan Cikasungka, PT Perkebunan XI, Kabupaten Bogor, dengan ketinggian tempat sekitar 360 m di atas permukaan laut. Curah hujan rata- rata 4 593 mm per tahun dengan 220.6 hari hujan. Jenis tanah di areal penelitian adalah podsolik merah kuning dengan pH berkisar 5.0 5.5. Penelitian berlangsung mulai bulan Januari 1991 hingga April 1991. Penelitian dilakukan terhadap gulma yang tumbuh di jalur tanaman karet belum menghasilkan. Pohon karet yang dijadikan petak penelitian ditanam tahun 1987 dengan jarak tanam yang digunakan 8.0 m x 2.5 m. Herbisida yang digunakan adalah metsulfuron metil yang terformulasi dalam Ally 20 WP dan glifosat yang ter- formulasi dalam Eagle 480 AS. Kedua herbisida tersebut dilarutkan dalam air. ...
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Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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