Judul: Pemanfaatan Trass Sebagai Sumber Silikon dan Pupuk MgO Untuk Padi di Tanah Gambut Dari Kumpeh, Jambi
Abstrak: The high number of Indonesian resident requires high food production to meet the food needs, especially the rice. Changes in land use from agricultural to non-agricultural land, reducing the ability of Indonesia for rice production. Therefore, the expansion of agricultural land on peatland is one alternative to increase rice production. However, peat as agricultural land has constraints i.e generally low in availability of macro and micro element, including Mg and Si. This study was a continuation of research by Fatmawaty ( 2013). Greenhouse trials conducted with a completely randomized factorial design with two factors which consisted of 12 treatments with 3 replicate, so there are 36 pot. Trials results showed that Trass increased crop height , number of tillers, soil Si availability and uptake of Si and P by rice plant. MgO increase soil pH, exchangeable of Mg, soil P availability, and uptake of Mg by rice plant. Trass as a source of Si was significantly increasing soil Si availability and uptake of Si by rice plant, so it can be used as fertilizer Si.
Keyword: Trass., Silica, Peat, MgO

Judul: Pemanfaatan Trass sebagai Pupuk Silika dan Pemberian Dolomit untuk Padi di Tanah Gambut dari Kumpeh, Jambi
Abstrak: High number of population in Indonesia demanding a high amount of rice production to fulfill the food needs as well. Changes of land use from agricultural to non-agricultural land, reducing the ability of rice production. Utilization of peat land for agriculture is an alternative to increase rice production. However, the use of peat land for agriculture will be faced with several constraints such as the low availability of macro and micro nutrients, including deficiency of Mg and Si. Peat soil parent materials derived from organic materials that have a low content of Si. In this study trass and dolomite is used as a source of Si and Mg. This study aimed to know the effect of trass and dolomite as source of Si and Mg on growth and uptake of Si and Mg by paddy, and change the chemical properties of peat. The trial was conducted in the greenhouse and Soil Chemistry and Fertility Laboratory at the Cikabayan Experiments Station and of Department of Soil Science and Land Resources, Faculty of Agriculture, IPB. This trial was done from February to July 2012. Factorial completely randomized design was used in this trial. Trass treatment consist of T0 (without Trass), T1 (2.5% w/w), T2 (5% w/w), T3 (7.5% w/w), whereas the dolomite treatment consist of D1 (1.6 ton/ha), D2 (4.8 tons/ha), D3 (8 tons/ha). The treatment is combination of these two factors resulting 12 combined treatment and 3 repeated in order to get 36 units of trial. Dolomite was significantly affect on plant height, while trass either singly or in combination with dolomite was not. Trass and dolomite singly and in combinations was significantly affect to the number of tillers. Highest plant height and tillers was about 50.1 cm and 10 achieved in T3D3. It was concluded that trass can be used as Si fertilizer. Mg uptake by paddy was increased with increasing doses of dolomite also for Si uptake with increasing of Trass dose. Change of Mg uptake from D1 to D2 and D2 to D3 was 0.26 g/pot and of 1.23 g/pot. Change of Si uptake by paddy from T0 to T1, T2, T3 were 0.34, 11.42 and 43.72 g SiO2/pot respectively. Dolomite was significantly increased of soil pH. Highest and lowest pH values is 5.55 and 4.10 obtained in the treatment T0D3 and T3D1. Dolomite was increased of exchangeable Mg in peat. Change a exchangeable of Mg from D1 to D2 and D3 is 2.29 and 13.76 me/100g respectively. Total of peat SiO2 was increased with increasing dose of Trass. Trass and Dolomite either singly or in combination was significantly affect on availability of SiO2 in peat. Highest available levels of SiO2 was obtained on T3D1 treatment about 61.50 ppm.
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Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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