Judul: Potato based sustainable vegetable farming systems planning in Siulak watershed, Kerinci district, Jambi
Abstrak: Established agricultural practices in upland vegetable growing areas in Indonesia are generally implementing up and down the slope cultivation with relatively high rates of fertilizers and pesticides applications. Combined with high rainfall intensity, these practices have contributed to high runoff and severe erosion and in turn gradually decreased land productivity and farmers income, thus unsustainable farming systems. The objectives of this research were : 1) to identify and describe existing conditions of the potato based vegetable farming systems, 2) to study soil conservation measures alternatives to control soil erosion and obtain optimal net farm income, and 3) to design potato based sustainable vegetable farming systems in Siulak Watershed, Kerinci District, Jambi Province. Land biophysical and farmers characteristics as well as agrotechnologies were identified through soil survey and farmers interview, while alternatives of soil conservation measures were studied through soil erosion plot experiments. Models of patato based sustainable vegetable farming system were formulated by simulation using Universal of Soil Loss Equation (USLE) model and multiple goal programming. Results of the research showed that up and down the slope vegetable farming practices and inadequate of soil conservation practices caused soil erosion rate of 39.25 - 229.14 ton/ha/year which was higher than the local soil tolerable loss (24.09 - 20.89 ton/ha/year), and net farm income was generally not enough to support life worthed living (Rp 28 000 000/year). Planting on ridges across the slope, or ridges constructed 15 degrees across the slope, or in ridges down the slope with a mound constructed across the slope in each 4.5 m distance and silt-pit, can be considered as alternatives soil conservation methods for vegetable farming systems. Potato based sustainable vegetable farming systems in Siulak Watershed could be accomplished by improving the cultivation practices by integrating the soil conservation methods (planting on ridges across the slope and mulch, or ridges down the slope with a mound constructed across the slope, mulch and silt-pit) into the existing systems. Potato based sustainable vegetable farming systems with the cropping pattern of potato-cabbage-tomato and recommended agrotechnologies performed the most optimum models in Siulak Watershed, Kerinci District, Jambi; this system generated soil erosion about 10.59 - 18.82 ton/ha/year and the net farm income about Rp 40 714 558 - Rp 52 745 652 per hectar per year on 0.44 ha farm area. Some farmers in Siulak Watershed have started applicating the recommended agrotechnologies right after the research was completed.
Keyword: farming systems, Siulak Watershed, Kerinci District, Jambi

Judul: Internalisasi Biaya Konservasi Lahan Pertanian Kentang Di Das Serayu (Studi Kasus Di Desa Igir Mranak, Kecamatan Kejajar, Kabupaten Wonosobo)
Abstrak: Environmental degradation caused by intensive potato farming on the upper Dieng Plateau has reached an alarming level. Farmers who intensively plant potatoes and other vegetables in this Plateu mostly do not apply soil and water conservation practices on their gardens. This is suspected as one of the main causes of high erosion and sedimentation rates in the watershed. These environmental problems combined with farmers’ behavior torwards soil and water conservation in their potato gardens require further attention and information on how to solve such problem. Therefore, this research offers some fundamental analysis on farm-budget under different conservation techniques, farmers’ willingness to accept in improving their conservation practices and potential of application of rewards for environmental services schemes in the upper Dieng Plateu. The objective of this study are (i) to evaluate the conservation practices of potato farming by comparing rate of erosion and farm productivity under different soil and water conservation techniques, (ii) to determine the Willingness to Accept (WTA) value to environmentally friendly farming practices for sedimentation reduction. The research involving 100 respondents was carried out in January–May 2011 at Igirmranak village, Wonosobo district, Central Java, Indonesia. The study shows that the total potato production on land without conservation techniques was 37% higher compared to the one with conservation techniques. This result is based on the measurement of the potato farming erosion rate that the conservation techniques could control erosion and run-off at higher rates (18.38% and 33.90% respectively) compared to potato farming without conservation techniques. Farmers who adopted conservation techniques experience less profit per season (IDR 5,905,021) than those who do not apply such technique. In contrast, the potato production per stem in conservation farming was 26% higher compared to production on land without conservation techniques. The study also showed that the value of WTA among farmers was IDR 5,000,000. Some factors that influenced them to make decisions were 1) bid amount and 2) perception of profitability of potato. Overall, this study concluded that the RES concept in Dieng could be implemented by setting enabling conditions for environmentally friendly agriculture system that could provide long-term benefits to farmers. Government involvement and support would be needed to provide livelihoods’ alternatives that can fill the gap between opportunity costs and WTA.
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Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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