Judul: Analysis of Biological and Chemical Characteristics of Soil at Various Altitudes in Bandung, West Java
Abstrak: Bandung memiliki ketinggian antara 675 mdpl – 2.100 mdpl dengan suhu udara berkisar 14oC sampai dengan 30oC. Ketinggian tempat merupakan salah satu faktor yang berpengaruh terhadap pertumbuhan dan perkembangan tanaman. Perbedaan ketinggian tempat di atas permukaan laut (dpl) dapat menimbulkan perbedaan iklim dan cuaca terutama suhu dan kelembapan. Perbedaan iklim dan cuaca dapat mempengaruhi populasi mikrob dan transformasi hara di dalam tanah. Tujuan dari penelitian ini mempelajari karakteristik sifat biologi dan kimia tanah pada beberapa ketinggian tempat di Bandung, Jawa Barat. Hasil penelitian menunjukkan ketinggian tempat menghasilkan aspek kesuburan tanah berbeda. Keragaman kadar unsur hara tanah yang karena tingkat pengelolaan lahan yang berbeda-beda. Populasi bakteri pelarut fosfat (BPF) dapat tumbuh dengan optimum pada ketinggian 1000 mdpl. Nilai pH yang sesuai untuk pertumbuhan bakteri serta kandungan P-Total yang sangat tinggi dan P-tersedia yang sedang merupakan faktor BPF tumbuh dengan memanfaatkannya sebagai sumber nutrisi. Total populasi fungi tumbuh optimum hanya sampai ketinggian 1200 mdpl, sedangkan pada ketinggian 1400 mdpl populasi fungi menurun. Respirasi tanah pada ketinggian tempat memiliki nilai yang tidak berbeda nyata. Tanaman hortikultura sesuai dibudidayakan pada ketinggian 600 – 1200 mdpl, sedangkan pada ketinggian > 1200 mdpl lebih sesuai untuk tanaman perkebunan., Bandung has an altitude between 675 masl – 2,100 masl with air temperatures ranging from 14oC to 30oC. The height of the place is one of the factors that influence the growth and development of plants. Differences in altitude above sea level (asl) can cause differences in climate and weather, especially temperature and humidity. Climate and weather differences can affect microbial populations and nutrient transformations in the soil. The aims of study is to study the characteristics of soil biological and chemical properties at several altitudes in Bandung, West Java. The results showed that the height of the place produced different aspects of soil fertility. The diversity of soil nutrient levels due to different levels of management. The population of phosphate solubilizing bacteria (BPF) can grow optimally at altitude of 1000 meters above sea level. The pH value is appropriate for bacterial growth as well as the very high P-Total content and moderate P-available is a factor in BPF growing by utilizing it as a source of nutrition. The total population of fungi grows optimally only at altitude of 1200 meters above sea level, while at altitude of 1400 meters above sea level the fungi population was decreased. Soil respiration at the height of the premises has no significant different value. Horticultural crops are suitable for cultivation at altitude of 600-1200 meters above sea level, while at an altitude of > 1200 meters above sea level are more suitable for plantation crops.
Keyword: Nutrient, Phosphate Solubilizing Bacteria, Temperature, Total Fungi

Judul: Analysis Biological and Chemical Characteristics of Soil in Several Types Land Use in Bogor Regency
Abstrak: Penggunaan lahan di Kabupaten Bogor memiliki vegetasi beragam dan karakteristik tanah berbeda. Karakteristik tanah memiliki pengaruh terhadap pengelolaan lahan. Keberadaan mikrob tanah dapat digunakan sebagai bioindikator kesuburan tanah. Kesuburan tanah dihasilkan oleh interaksi sifat fisik, kimia, dan biologi tanah. Penelitian ini bertujuan mengetahui karakteristik sifat biologi dan kimia tanah pada berbagai tipe penggunaan lahan di Kabupaten Bogor. Pengambilan sampel tanah dilakukan dengan menggunakan metode purposive random sampling dengan 5 kali ulangan. Lokasi penelitian meliputi delapan penggunaan lahan yaitu kebun bambu, kebun jabon, kebun sengon, kebun lamtorogung, tegalan, tanaman sereh wangi, kebun buah naga, dan kebun pisang. Hasil analisis menunjukkan lahan pisang dan buah naga memiliki kadar C-organik, N-total tertinggi dan populasi fungi tertinggi yaitu 3,78 x 105 CFU/gram. Sedangkan pada lahan di Kecamatan Jasinga yang memiliki hara dan populasi fungi yang cukup dan populasi Azotobacter tertinggi yaitu pada lahan lamtorogung dapat diusahakan untuk tanaman perkebunan yang lebih memiliki nilai jual lebih tinggi seperti pada lahan tegalan dapat ditanami pohon karet, kelapa sawit, atau kakao., Land use in Bogor Regency has diverse vegetation and different soil characteristics. Soil characteristics have an influence on land management. The presence of soil microbes can be used as bioindicators of soil fertility. Soil fertility is produced by the interaction of physical, chemical, and biological properties of the soil. This study aims to determine the characteristics of the biological and chemical properties of soil in various types of land use in Bogor Regency. Soil sampling using the purposive random sampling method with 5 repeats. The research location includes eight land uses, namely bamboo, jabon, sengon, lamtorogung gardens, moorings, fragrant lemongrass plants, dragon fruit orchards, and banana gardens. The results of the analysis showed that banana and dragon fruit fields had the highest C-organic, N-total levels and the highest fungi population of 3,78 x 105 CFU/gram. Meanwhile, on land in Jasinga District which has sufficient nutrients and fungi populations and the highest Azotobacter population, namely on lamtorogung land, it can be cultivated for plantation crops that have a higher selling value, such as in moorlands that can be planted with rubber trees, oil palm, or cocoa.
Keyword: Azotobacter sp., microbes, soil fertility, total fungi

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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