Judul: Produksi padi sawah dan dinamika populasi gulma pada berbagai perlakuan persiapan lahan dan waktu pemupukan urea
Abstrak: Usaha peningkatan produksi padi (Oryza sativa. L) senantiasa dilakukan dengan berbagai cara, antara lain dengan teknik persiapan laban dan waktu pemupukan. Cara persiapan lahan tanpa olah tanah dengan aplikasi herbisida sebagai salah satu sarana produksi dan penggunaan pupuk urea tablet pada beberapa kali pemberian dicoba pada penelitian ini.
Keyword: Gulma, Oryza sativa. L, pemupukan

Judul: Justifikasi Dan Perbaikan Secara Agronomi Pemakaian Pupuk Urea Tablet Pada Padi Sawah
Abstrak: Padi (Oryza sativa L.) merupakan salah satu tanaman yang sangat penting sebagai bahan pangan yang dibutuhkan Sebagian besar penduduk dunia. Pemerintah atau badan dunia yang berkaitan dengan masalah pangan selalu berusaha me- ningkatkan kuantitas dan kualitas produksi beras. Penelitian ini bertujuan untuk mengetahui (1) efisiensi pemakaian pupuk urea tablet terhadap urea butir; (2) mengetahui hubungan waktu, dosis dan bentuk pupuk terhadap pertumbuhan dan hasil sekaligus memberikan produksi tinggi pada budidaya padi sawah. Percobaan telah dilakukan di lapang di Kebun Perco- baan IPB Babakan Darmaga, Bogor. Data pendukung diperoleh dengan melakukan percobaan di pot. Percobaan dengan ran- cangan perlakuan Split-split Plot. gaman yang diteliti yaitu; Rincian sumber kera- Petak Utama: Waktu Pemberian, terdiri atas tiga taraf waktu pemberian, T1 = pupuk dibe- rikan satu kali, T2 = pupuk diberikan dua kali dan T3 = pupuk diberikan tiga kali. Anak Petak: Dosis, terdiri atas empat taraf yaitu, D1 = 45 kg N/ha, D2= 67,5 kg N/ha, D3 90 kg N/ha dan D4 = 112,5 kg N/ha. Anak-anak Petak: Bentuk pupuk, urea terdiri atas dua bentuk yaitu B1 = Urea bentuk tablet dan B2 = Urea bentuk butir. Hasil percobaan menunjukkan bahwa perlakuan T2D2B1 yaitu waktu pemberian dua kali, dosis 67,5 kg N/ha dan bentuk pupuk urea tablet memberikan hasil tertinggi yaitu 4720 kg gabah kering per hektar. Pemberian Urea Tablet Qua kali dibenarkan karena dapat memperbaiki pertumbuhan naman dan meningkatkan hasil gabah kering per satuan Luas lahan. an Dari kenaikan hasil yang diperoleh, pemakai- urea tablet lebih efisien dibandingkan dengan urea butir.,...dst
Keyword: Oryza sativa l, nitrogen in the soil, nitrogen fertilization in lowland rice plants

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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