Judul: Pemberian kotoran sapi pada pertanaman jagung (Zea mays) dinamika kadar c-organik dan n-tersedia pada andisol Lembang Jawa Barat
Abstrak: Penelitian Pemberian Kotoran Sapi pada Pertanaman Jagung (Zea mays) : Dinamika Kadar karbon (C) organik dan nitrogen (N) tersedia pada Andisol Lembang Jawa Barat ini dilaksanakan dari bulan Oktober 2009 hingga Mei 2010. Penelitian di lapangan dilaksanakan di Balai Penelitian Tanaman Sayuran, Lembang, Jawa Barat, sementara analisis sifat kimia tanah dilaksanakan di Laboratorium Kimia dan Kesuburan Tanah, Departemen Ilmu Tanah dan Sumberdaya Lahan, Fakultas Pertanian Institut Pertanian Bogor. Tujuan dari penelitian ini adalah untuk mengetahui dinamika perubahan kadar C-organik dan juga kadar N-tersedia (ammonium dan nitrat) pada tanah yang diberi perlakuan kotoran sapi. Perlakuan yang diberikan adalah 0 ton ha-1 and 20 ton ha-1 kotoran sapi. Pengambilan contoh tanah dilakukan pada minggu ke-1, 2, 3, 4, 6, 8, 10, dan 14 pada daerah perakaran (rhizosfer). Hasil analisis menunjukkan bahwa terjadi perubahan kadar C-organik serta kadar ammonium (N-NH4 +) dan nitrat (N-NO3 -) pada minggu-minggu pengambilan contoh tanah baik pada petak kontrol dan petak yang diberi perlakuan kotoran sapi. Proses nitrifikasi terjadi sejak minggu pertama inkubasi. Kadar NO3 - jauh lebih besar dibandingkan dengan kadar NH4 + pada setiap periode pengambilan contoh tanah. Kadar N-NO3 - mulai terlihat naik sejak minggu ke-3 inkubasi, diikuti dengan menurunnya kadar N-NH4 +. N-tersedia adalah Total dari N-NH4 + dan N-NO3 -. Data N-tersedia pada petak kontrol dan petak kotoran sapi disimulasi dengan menggunakan persamaan first order kinetic yaitu N=Nm (1-exp(-kt)), dengan N adalah konsentrasi Ntersedia, Nm adalah nilai N yang berpotensi termineralisasi, k adalah konstanta kecepatan mineralisasi, dan t adalah waktu dalam minggu. Persamaan first order kinetic untuk petak kontrol adalah N=560 (1-exp-0.242t) dengan nilai R2 sebesar 0.51 dan untuk petak kotoran sapi adalah N=717 (1-exp-0.223t) dengan R2 0.72. Berdasarkan nilai Nm dapat dilihat bahwa N yang berpotensi termineralisasi pada perlakuan kotoran sapi lebih tinggi dibandingkan petak kontrol, tetapi konstanta kecepatan mineralisasi N pada petak kontrol lebih cepat dibandingkan dengan petak yang diberi perlakuan kotoran sapi. Nilai R2 yang tinggi (0.5-1.0) menunjukkan bahwa persamaan-persamaan ini dapat digunakan untuk memprediksi laju N-tersedia pada minggu ke-t pada tanah Andisol Lembang. Dengan persamaan ini dapat dihitung bahwa N yang dapat termineralisasi akan habis pada minggu ke-30 setelah tanam
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Judul: Pemberian kotoran sapi pada pertanaman jagung (Zea mays) perubahan beberapa sifat kimia dan fraksi fosfor inorganik pada andisol Lembang, Jawa Barat
Abstrak: The research entitled Fraction The Application of Cow Dung on Maize (Zea mays) cultivation: The Changes of Some Chemical Properties and Phosphorus Inorganic Fractions on Andisol Lembang was conducted from September 2009 until April 2010. The research in the field was conducted at Indonesian Vegetables Research Institute, Lembang, West Java, while the chemical properties of soil analyses were performed at the Laboratory of Soil Chemistry and Fertility, Department of Soil Science and Land Resource, Faculty of Agriculture, Bogor Agricultural University. The background of this research is the high application of organic metter to overcome the very high P retention in this soil. Therefore the research concerning the P fractions distribution is very important. The researches related to the effect of organic matter to changes on P fractions would have been a lot done, but researches data on those for Andisol Lembang is not yet available. The objectives of this research were to evaluate the effect of cow dung to changes of some chemical properties and fractions of inorganic P (Pi) on maize cultivation in the root (rhizosfer) area and in between crop rows. The treatments were applied in four rates those were 0, 10, 20, and 40 tons ha-1 and each treatments were repeated three times. Composite soil sampling was conducted at two weeks after incubation (prior to maize planting) and after harvest when the maize was about three months collected in the rhizosfer area and in between rows of plants. The changes on P fractions were calculated by subtracting the fraction P after two weeks of incubation with fraction P after harvest in the rhiszosfer area and in between rows of plants. The results of preliminary analyses suggested that this Andisol Lembang was slightly acid. C-organic carbon was very high status, cation exchange capacity (CEC) was high status, base saturation (BS) was low status, total N was medium status, available P was high status and soil texture class was silt loam. The high available P suggested that P fertilization in Andisol Lembang was very intensive. The results suggested that cow dung did not increase significantly soil pH, soil CEC, and C-organic. The cow dung did not increase BS significantly after two weeks of incubation but increase BS significantly at harvest in the rhizosfer area and in between rows of plants. The BS values at harvest were lower than two weeks after the incubation that suggesting there was leaching process or the removal of nutrients by the plants. The cow dung increased resin-Pi significantly. The changes in resin-Pi after harvest in between rows of plants and rhizosfer area were negative in their values. Those indicated that there was a transformation process of the resin-Pi into other P fractions or absorbed by plants. The cow dung increased NaHCO3-Pi significantly at harvest in both the rhizosfer area and in between rows of plants but did not increased this fraction significantly at after two weeks of incubation. The changes of NaHCO3-Pi in the rhizosfer area were positive in their values indicating that the resin-Pi transformed into this fraction. While the values of a negative changes
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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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