Judul: Distribusi N-Amonium Dan N-Nitrat Pada Latosolsemplak Dan Pengaruhnya Terhadap Produksi Jagung Manis (Zea Mays Saccharata)
Abstrak: Air merupakan pelarut dan pembawa hara, sehingga proses pergerakannya akan mempengaruhi pergerakan dan distribusi hara dalam tanah. Kecepatan pergerakan air dalam tanah dipengaruhi oleh sifat fisik tanah, kandungan bahan organik dan perbedaan penggunaan lahan akibat dari pengelolaan tanah yang berbeda. Nitrogen merupakan unsur hara yang memiliki mobilitas tinggi dalam tanah sehingga mudah bergerak bersama dengan air. Tujuan dari penelitian ini untuk mempelajari distribusi N-amonium dan N-nitrat per kedalaman setiap minggunya dan mempelajari pergerakannya pada lahan kering dan lahan bekas sawall serta melihat hubungannya dengan produksi jagung manis. Penelitian dilakukan pada dua lahan dengan jenis tanah latosol yaitu lahan kering dan lahan bekas sawah. Analisis unsur hara N-amonium dan N-nitrat merupakan parameter utama yang diamati. Pengukuran dilakukan dengan menggunakan alat Flow Injection Analysis (FIA) Star Analyzer 5000.
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Judul: Pengaruh Pemupukan Nitrogen Tinggi dan Kalium terhadap Produksi dan Rasa Manis PAda Jagung Manis (Zea mays saccharata Sturt)
Abstrak: Penelitian ini bertujuan untuk mempelajari pengaruh beberapa tingkat pemupukan nitrogen sampai dosis tinggi dan kalium serta interaksinya terhadap produksi dan rasa manis pada tanaman jagung manis. Penanaman dilakukan di Kebun Percobaan IPB Cikarawang, pada ketirlggian 240 m dpl dengan tanah jenis Latosol Coklat Kemerahan, pada musim hujan dari bulan November 1986 sampai bulan Februari 1987. Benih yang digunakan adalah varietas Seleksi Darmaga II (SD II). Percobaan terdiri dari lima taraf pemberian pupuk N (0, 100, 200, 300 dan 400 kg N/ha) dan dua taraf pupuk K (50 dan 150 kg K2O/ha) sehingga terdapat sepuluh Kombinasi perlakuan, yang disusun secara faktorial dalam Rancangan Acak Kelompok sebanyak tiga ulangan.
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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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