Judul: Pengaruh Aplikasi Senyawa Humat Terhadap Sifat Kimia Tanah Vertisol dan Pertumbuhan Tanaman Jagung (Zea mays).
Abstrak: Vertisol is one of the potential soil type that can be used for agriculture activity intensively. This soil has high pH, cation exchange capacity (CEC), and base saturation percentage, but it has high potassium fixation that causes inefficiency in fertilization. Vertisol is considered as fertile soils, large cracks and hard soil consistency in drought seasons, sticky consistency in rainy seasons, and high potassium fixations are problems that are considered serious if the soil is used for the agriculture land. The purpose of this research are to find out the effects of applications of several dosages of humic substance to the chemical properties of vertisol, also the effects of applications of humic substance to the growth of the corn plant. This research was done in the green house university farm of Bogor Agriculture University. This research was done since September 2008 until February 2009. Soil analysis was done in the laboratory of land physical resource development, laboratory of physics and soil conservation, and laboratory of chemistry and soil fertility, Soil Science and Land Resource Department, Faculty of Agriculture, Bogor Agriculture University. Soils are applied with dosages of humic substance which are H0 (0 l/ha), H1 (5 l/ha)), H2 (10 l/ha), dan H3 (25 l/ha). The results of this research showed that addition of humic substance does not gives a significant increase to the soil chemical properties of vertisol generally. Soil acidity (pH) showed a relatively same value in all dosages that which were 7,49 - 7,51. Base saturation that was also analyzed in each application showed a percentage of >100%., where bases that analyzed were dominated by Ca and Mg Cations. CEC showed a small increase for all treatment. The highest increase of CEC is in H1 which is 30,76 me/100g from control which is 27,92 me/100g. C-organic showed a relatively same value for each application which is in the range of 1,05% in H1 and 1,22% in H3. Application of humic substance showed an increase in plant height, wet mass, and dry mass. But showed the same value relatively in the numbers of leaves of the corn.
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Judul: Aplikasi Bahan Humat dengan Carrier Zeolit untuk Meningkatkan Produksi Tanaman Jagung (Zea mays) pada Latosol Bogor.
Abstrak: Indonesia is one of wet-tropical countries having high temperature and rainfall so that leaching in soil is very intensive. This condition makes nutritions in the soil decrease significantly and declining crop production. Many efforts have been done for increasing food crop production without damaging soil characteristics and causing environmental pollution such as application of chemical fertilizer with accurate dossage accompanied by addition of organic fertilizer. However, soil need organic fertilizer in large amount for improving soil characteristics and increase food crop production. Humic substance which is extracted from organic matter can substitute organic fertilizer. Generally, humic substance is applied in liquid form with a small amount, therefore it need a carrier to make the application easy and the humic substance is not easily leached. Zeolite that has porous structure is material potential to be used as carrier of humic substance. Application of humic substance with zeolite as carrier is expected to increase production of food crop such as corn. This experiment consists of field experiment that was conducted in agricultural land at Sindangbarang District, Bogor City, green house experiment that was conducted in University Farm IPB, and soil and plant analysis in chemist and soil fertility, Laboratory of the Department of Soil Science and Land Resources, Faculty of Agriculture, Bogor Agricultural University. Field experiment is arranged in a randomized block design 2 factorial with 2 replications. Treatment is consist of 1 control, 3 humic substance treatment (A5, A10, and A15), 2 zeolite treatment (Z10, and Z20), and 6 combination humic substance and zeolite treatment (A5Z10, A10Z10, A15Z10, A5Z20, A10Z20, and A15Z20). The results showed that application of humic substance with zeolite as carrier gave a better effect for increasing corn production than application of humic substance or zeolite itself. Humic substance with zeolite as carrier can increase P-available and CEC of soil. Moreover, humic substance with zeolite as carrier increased nitrogen level in corn leaf. The growth of corn increased with the increase of root weight and plant height. The optimum and profitable dosage of humic substance with zeolite as carrier was 10 liters humic substance/ha with 20 kg zeolite as carrier/liter humic substance because it showed the biggest increase corn production or 19% increase than plants without application of humic substance with zeolite as carrier and gave profit up to Rp 1.212.000,00/ha per planting season. This dosage can be recommend by farmer.
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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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