Judul: Pengaruh Dosis Pupuk Urea dan SP-36 terhadap Dekomposisi Bahan Gambut
Abstrak: Pemanfaatan lahan gambut di Indonesia saat ini meningkat seiring dengan semakin berkurangnya lahan produktif untuk kegiatan pertanian. Namun perkembangan kegiatan tersebut terhambat karena isu pembukaan dan pemanfaatan lahan gambut dapat meningkatkan emisi Gas Rumah Kaca (GRK). Penurunan muka air tanah dan pemberian pupuk pada lahan gambut seringkali dikorelasikan langsung dengan kehilangan gambut akibat peningkatan dekomposisi gambut yang melepaskan CO2 ke atmosfer. Disamping itu, pentingnya peranan mikrob seringkali tidak dipertimbangkan padahal peranan mikrob dalam dekomposisi bahan gambut sangat vital dalam hal total aktivitasnya. Aktivitas mikrob dipengaruhi oleh berbagai faktor seperti nutrisi, pH, kelembaban, dan kandungan senyawa beracun pada lahan gambut. Penelitian ini dilakukan untuk mengetahui pengaruh unsur hara N dan P terhadap aktivitas mikrob dan dekomposisi bahan gambut berkaitan dengan emisi CO2 yang dihasilkan. Aktivitas mikrob dicerminkan dari populasi bakteri dan fungi (metode cawan tuang) dan serta kaitannya dengan respirasi tanah (metode stoples). Hasil penelitian menunjukkan respirasi tertinggi berasal dari serasah. Hal ini disebabkan pada serasah daun Acacia crassicarpa masih terdapat banyak nutrisi dan sumber energi yang dapat dimanfaatkan oleh mikrob sehingga aktivitas mikrob pun meningkat. Hal ini menandakan bahwa kontribusi CO2 yang tinggi dihasilkan dari dekomposisi serasah dibandingkan dengan yang dihasilkan dari dekomposisi bahan gambut. Aktivitas mikrob dan dekomposisi bahan gambut tertinggi ditunjukkan pada penambahan pupuk N yang dilihat dari populasi mikrob dan respirasi yang lebih tinggi dibandingkan penggunaan pupuk N dengan pupuk P. Hasil ini menunjukkan unsur hara N yang menjadi faktor pembatas dari aktivitas mikrob (tanpa mengabaikan peran unsur hara N dan P untuk mikrob) sebagai sumber hara dan pertumbuhannya.
Keyword: aktivitas mikrob, dekomposisi bahan gambut, pupuk, respirasi

Judul: Pengaruh Kadar Air dan Pemberian Pupuk terhadap Dekomposisi Bahan Gambut
Abstrak: Peat land has often been used for large scale farming and plantation. Thus the technology on its utility has been improved and shows a bright prospect. However, the use of those technology upon the peat land has received many critics. Many scientists suggest that the decreasing of ground water levels in peat land will cause the increase of CO2 emission; the lower the groundwater surface, the more emission will be. However, this theory is only based on chemistry and physics reactions, while in fact the decomposition process is determined by biochemical reactions where microbes hold an important role. The objective of this research is to know the effect of water content combined with the addition of fertilizer on the peat decomposition and its composing materials based on its respirations. The respiration was measured by Jar Method. Respiration measurement was done every 10 days until the level of respiration rate was constant. The result showed that 2 times water holding at field capacity (WHFC) treatment has the highest respiration value as compared with 1 times WHFC and 0.5 times WHFC. The addition of urea fertilizer whether alone or combined with SP-36 has an effect to the value of the respiration. The addition of litters on sieved peat (GS) or the sieved peat combined with woody materials (GBS) also showed high respirations value. The high value of respiration was affected by the population of bacteria and fungi. This is supported by suitable environment and adequate food supply. Result of final analysis after incubation showed C/N and C/P ratio may not figured the rate of decomposition.
Keyword: water content, respiration, peat composing materials, peat decomposition

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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