Judul: Pengaruh Pemberian Ekstrak Bahan Organik dari Kompos Kotoran Ayam, Kompos Kotoran Sapi dan Larutan Bahan Humat terhadap Fosfor Tersedia pada Inseptisol Dramaga dan Inseptisol Surade
Abstrak: Phosphorus (P) is an essential macro-nutrient for plant growth and development. Phosphorus problems in the soils are the small amount of P content and low availability because of high fixation. This research was aimed to find out the influence of applying organic matter extract from chicken manure compost, cow manure compost and solution of humate materials on the amount of available P in Dramaga Inceptisol and Surade Inceptisol. In this research, organic matter extract from chicken manure compost (1:10), cow manure compost (1:10), and solution of humate materials (1:4) were added to Dramaga Inceptisol and Surade Inceptisol. Analysis of available P was conducted using Bray I methods. The results analysis showed that available P were increased by adding chicken manure compost extract and cow manure compost extract. Addition of extract from chicken manure compost and cow manure compost which contained P of 1.43 ppm and 1.02 ppm each has increased available P in Dramaga Inceptisol from 5.3 ppm on control sample to 163 ppm and 216 ppm. The same treatment also increased available P in Surade Inceptisol from 4.8 ppm on control sample to 142 ppm and 179 ppm. Addition solution of humate materials A and B that containing P in Dramaga Inceptisol successfully increased available P from 5.3 ppm on control sample to 44 ppm and 35 ppm, and available P in Surade Inceptisol increased from 4.8 ppm on control sample to 26 ppm and 30 ppm.
Keyword: humate materials, cow manure compost, chicken manure compost, organic matter extract, Inceptisol, available P

Judul: Pengaruh Bahan Organik terhadap Ketersediaan Fosfor pada Tanah-Tanah Kaya Al dan Fe
Abstrak: Phosphorus (P) is one of the essential nutrients for plants. However, the availability of P that can be absorbed by plants in the soil is generally very low, because P in the soil are manily in adsorbed form. Addition of organic matter can improve the availability of P in the soil, because organic acids that are resulted by decomposition of organic matter have an ability to make chelation of Al and Fe so P may become available. The aim of this research was to study effect of organic matter in releasing and preventing adsorption of P and to study wether the effect of organic matter is better if it is applied before or after P fertilization. This research consisted of five treatments: (1) Soil (Andosol, Latosol, Podsolic) was added with straw compost and 2 weeks later P fertilizer was added, (2) Soil (Andosol, Latosol, Podsolic) was added with P fertilizer and after 2 weeks straw compost was added, (3) Soil (Andosol, Latosol, Podsolic) was added with cow manure compost and after 2 weeks P fertilizer was added, (4) Soil (Andosol, Latosol, Podsolic) was added with P fertilizer and after 2 weeks cow manure compost was added, and (5 ) Soil (Andosol, Latosol, Podsolic) was added with P fertilizer only. Each treatment on the three soils was incubated for 1 and 2 months. The results showed that treatment of organic matter and P fertilizer addition is more effective in increasing pH and P-availability, as well as lowering the Al-dd and Fe-availability on the three soils than the treatment of only addition of P fertilizer. Cow manure compost gives a higher effect than straw compost. The addition of organic matter to improve releasing adsorbtion of P and preventing adsorption of P on Latosol and Podsolic, meanwhile for Andosol effect of organic matter is less visible. Latosol and Podsolic, the addition of organic matter is better if it is done after P fertilization, meanwhile for Andosol the addition of organic matter is better if it is done before P fertilization. The highest available-P of Andosol is in the treatment is soil was added with cow manure compost and after 2 weeks P fertilizer was added is 10.67 ppm, meanwhile available-P for Latosol is soil was added with P fertilizer and after 2 weeks cow manure compost was added is 90.95 ppm, and Podsolic is Soil was added with P fertilizer and after 2 weeks cow manure compost was added is 40.73 ppm.
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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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