Judul: Nitrogen Mineralization of Four Andisol Soil Depths which is Cultivating Organic and Conventional in Ciwidey and Cisarua.
Abstrak: Conventional agricultural system uses pesticide and organic fertilizer excessively that cause nutrient accumulation in waters and ground water that can pollute environment. Nitrogen is one of essential nutrient with low availability in the ground. Nitrogen is dynamic nutrient and easy to change. Therefore it needs to obtain information about nitrogen mineralization degrees especially NH4+ and NO3- in some depths of Andisol soil which is developed for cultivating organic and conventional in Ciwidey and Cisarua. The soil samples were taken from 0-25, 25-50, 50-75, and 75-100 cm depths at Ciwidey (Bukit Organik) and Cisarua (Permata Hati dan Bina Sarana Bakti). Drilling was done in each embankment of four points which were chosen randomly of each cultivating area. Soil samples of four points were mixed to homogenous. NH4+ and NO3- contents of the soil were analyzed using KCl and CaCl2 spectrophotometric methods. Based on the results, there was a difference of nitrogen mineralization (content of NH4+ and NO3-) in the some depths of Andisol soil which is developed for cultivating organic and conventional at Permata Hati, Bukit Organik, and Bina Sarana Bakti. Nitrogen mineralization of NH4+ in the soil of organic cultivating is slower than conventional cultivating.
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Judul: Mineralization potency of N-NH4 + and N-NO3 - at Andisol Soil planted vegetables on highly upland.
Abstrak: Nitrogen is one of essential minerals for plant but it has less availability in the soil. Nitrogen is absorbed by plant as NH4 + (ammonium) and NO3 - (nitrate). Nitrogen organic in the soil is easy to change so this experiment was carried out to measure mineralization potency of N-NH4 + and N-NO3 - at Andisol Soil planted vegetables on highly upland. Andisol soils sample used came from Kejajar Wonosobo and Sumowono Semarang represent farmer 1 and 2. The first step of analysis was preparation of soil sample, and put it into PVC (diameter 5,4 cm and high 10 cm) for incubation. Experiment needed 102 days incubation with 9 times sampling with time duration of each sampling is 0, 7, 18, 31, 46, 60, 74, 88, and 102 days. Then, NH4 + and NO3 - contents of the soil were analyzed using KCl and CaCl2 spectrofotometri method. Based on the experiment, mineralization potency of released N-NH4 + at Kejajar Wonosobo from soil farmer 1 and 2 were 7,45 and 7,15 mg kg-1, whereas N-NO3 - of farmer 1 and 2 were 111,20 and 123,41 mg kg-1, respectively. Mineralization potency of released N-NH4 + at Sumowono Semarang from soil farmer 1 and 2 were 7,23 and 7,17 mg kg-1, whereas N-NO3 - of farmer 1 and 2 were 94,95 and 103, 55 mg kg-1, respectively. Ammonium or Nitrate mineralization processes almost has same pattern in andisol soils at Kejajar Wonosobo and Sumowono Semarang.
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Judul: Pemodelan Harga Saham Menggunakan Model Lévy dan Model Black-Scholes
Abstrak: Stock may produce high profits. However, it has a high risk as well, because the stock prices fluctuate over time. Therefore, a model is required to estimate the future stock prices accurately. In this paper, Lévy model is compared to Black-Scholes model in estimating the stock price at Bank of America Corporation. As a result, it is concluded that the Black-Scholes model is more accurate than Lévy model.
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