Judul: Phosphorus Movements at Saturated Water Condition in Andosol Lembang, Latosol Dramaga, and Grumusol Cianjur Soil Columns
Abstrak: Pergerakan hara di setiap jenis tanah berbeda-beda berdasarkan sifat fisik dan kimia dari tanah tersebut. Kecukupan dan pasokan hara yang tepat dibutuhkan oleh tanaman agar dapat tumbuh dan berkembang dengan baik. Namun fosfor dapat diikat oleh suatu jenis tanah yang mengakibatkan menjadi tidak tersedia untuk tanaman, sehingga pemupukan fosfor banyak dilakukan di lahan pertanian. Penggunaan pupuk fosfor yang dilakukan secara terus-menerus dan dapat menjadi tidak efektif. Pengetahuan tentang pergerakan fosfor di dalam tanah menjadi penting dalam hal ini untuk dipelajari, maka melalui penelitian ini dapat disajikan gambaran tentang pergerakan fosfor dalam beberapa tipe tanah dalam tabung tanah. Setiap kolom tanah diberi perlakuan dengan menjenuhinya menggunakan larutan fosfor kemudian untuk diamati pergerakan P-total nya. Penelitian pergerakan fosfor ini menggunakan pipa PVC dengan kedalaman tanah yang diambil ialah 30 cm dan diameter pipa 10 cm. Alat yang digunakan untuk mengamati pergerakan fosfor ialah constant head dan spektrofotometer. Larutan fosfor yang digunakan dalam penelitian ini adalah larutan KH2PO4 dengan konsentrasi yang dimasukkan ke dalam kolom tanah (inffluent) sebesar 500 ppm. Larutan fosfor dialiri secara jenuh dan kontinyu, sehingga larutan fosfor yang keluar dari kolom tanah (effluent) ditampung berdasarkan pada setiap volume yang diinginkan dengan waktu secara periodik pada setiap jenis tanah. Pergerakan fosfor berhenti diamati pada saat konsentrasi effluent sama dengan konsentrasi inffluent, yaitu ketika mencapai titik kesetimbangan (C/Co= 1). Pergerakan fosfor untuk mencapai titik kesetimbangan (C/Co= 1) paling lama terdapat pada tanah Andosol karena fosfor dijerap sangat kuat oleh tanah. Rasio konsentrasi C/Co pada tanah Andosol mencapai titik kesetimbangan pada saat (V/Vo= 13,74), dengan volume larutan yang dibutuhkan ialah 22 liter. Pada tanah Latosol rasio konsentrasi C/Co mencapai titik kesetimbangan pada saat (V/Vo= 5,99), dengan volume larutan P yang dibutuhkan sebanyak 8,6 liter. Sedangkan pada tanah sawah Grumusol rasio konsentrasi C/Co mencapai titik kesetimbangan pada saat (V/Vo= 4,87), dengan volume larutan P yang dibutuhkan sebesar 7 liter. Kata kunci :aliran massa, penjerapan fosfor, sifat fisik dan kimia tanah, The movement of nutrients in each type of soil varies based on the physical and chemical properties of the soil. Adequacy and supply of the right nutrients by plants needed for these plants to grow and develop properly. In certain types of soil, phosphorus can be found by the soil so it is not available for plants, so phosphorus fertilization is mostly done on agricultural land. The use of phosphorus fertilizers that are carried out continuously can produce ineffective fertilization. Knowledge of the movement of phosphorus in the soil is important to be studied, so through this research will be presented an overview of fosfor movement in several types of soil colums. Each soil column was treated by saturating the soil with a phosphorus solution to observe the total P-movement. This research on the movement of phosphorus uses a soil column in a PVC pipe with a soil depth of 30 cm and a pipe diameter of 10 cm. The tools used to observe the movement of phosphorus are to find a constant head and a spectrophotometer. The phosphorus solution used in this study is a KH2PO4 solution with an influent concentration of 500 ppm which
Keyword: adsorption phosphorus, mass flow, soil physical and chemical properties

Judul: Potassium (K+) Movements in Andosol Lembang, Grumusol Cianjur and Latosol Dramaga Soil Columns
Abstrak: Modern agriculture using excessive and continuous use of inorganic fertilizers needs to be reviewed because apart from being inefficient in terms of cost, it also has a negative impact on the environment. One example is the use of K fertilizer. Therefore, it is necessary to maximize the effectiveness of using K fertilizer and minimize its movement to underground water with knowledge of the movement of solutes or chemicals such as K fertilizer. This study aims to examine the movement of solutes, especially potassium (K) in the soil. Soil column of Lembang Andosol Soil, Latosol Dramaga and Grumusol Cianjur. The measurement of the movement of K is carried out using a constant head device based on the decrease in water level in the permeameter. KCl fertilizer solution is flowed into the soil column which is used in a saturated state, using a certain concentration periodically and a certain time span. The extract that came out of the soil column was accommodated with a measuring flask periodically, then the concentration of the solution was measured using a flamephotometer to obtain a concentration equal to the concentration of the solution that was inserted into the soil column. The movement of solutes, especially potassium in the soil, can occur through the process of diffusion and mass flow, or hydrodynamic dispersion. The ability of the soil to absorb solute (potassium) greatly affects the movement of solutes. Equilibrium point (C/Co)=1 movement of potassium in each different soil, namely in Andosol soil is equal to (V/Vo)=7.5, Latosol is (V/Vo)=4.8 and Grumusol (V/Vo) )=4,1. From the three types of soil, it shows that the movement of K nutrients is dominated by mass flow, which can be concluded from if the velocity of water and fertilizer is almost the same, then the process of nutrient movement is dominated by mass flow.
Keyword: mass flow, solutes, physical and chemical properties of soil

Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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