Judul: Pengaruh Berbagai Cara Pemberian Bahan Humat terhadap Produksi Ubi Jalar (Ipomoea batatas L.)
Abstrak: Utilisation of humic substance has been widely known to have positive effect on plant productivity. Characteristic of this substance that is easily soluble in water and applied in small amount has brought several obstacles on its wide application. Zeolite that has porous structure is a potential mineral used for humic substance carrier. Various studies in order to examine the role of humic substance on crop yield enhancement were reported limitedly on rice and corn so far, whereas it is rarely conducted on sweet potato. Therefore, it is necessary to conduct research for determining the best method of humic substance application on increasing sweet potato yield. In this research, humic substance was applied in several methods i.e. control (without humic substance and zeolite), humic substance applied directly into soil, humic substance sprayed on leaves, zeolite without humic substance, and humic substance carried by zeolite. The results showed that the application of humic substance carried by zeolite was the best method on increasing sweet potato productivity. This improvement on sweet potato yield is shown by the greater amount and bigger size of tubers of each plant. Moreover, the application of humic substance carried by zeolite showed the highest soil exchangeable K.
Keyword: zeolite., sweet potato, production, humic substance

Judul: Pengaruh Pupuk Anorganik Dan Pupuk Organik Terhadap Produksi Dan Kualitas Ubi Jalar (Ipomoea batatas (L.) Lam) Dan Sifat Kimia Podsolik Jasinga
Abstrak: Podsolic is the soil that has a very wide spread in Indonesia, which reached 47,526 million ha of total land area of Indonesia. Podsolic is soil with organic matter content less than 2 %, base saturation is generally low (<35 %), acid (pH 3.5-5.5), low to high cation exchange capacity depending on the texture and clay mineral, low content of nutrients, especially N, P, K, and Ca, and generally have relatively low fertility rate. Sweet potato is a plant that has little risk of crop failure and has a wide adaptability to the environment, so that it can be cultivated on various types of land, altitude, and different levels of soil fertility. This research is a field experiment of planting sweet potatoes in demonstration plot of BPN RI, Setu village, Jasinga, Bogor District with total area of 1800 m2. The design of treatment randomized complete block design factorial two factors. The first factor is the dose of inorganic fertilizer (15-15-15 and Rock Phosphate), while the second factor is the organic fertilizer (with and without humic). Soil analysis was performed at the Center for Soil Research, Bogor and analysis of the quality of sweet potato conducted at the Laboratory of Technopark, Bogor Agricultural University. This study aims to determine the effect of inorganic fertilizer (15-15-15 and Rock Phosphate), and organic fertilizer (humic) on growth, production and quality of sweet potato (Ipomoea batatas (L.) Lam.) and soil chemical properties Podsolic Jasinga. The results showed that the inorganic fertilizer15-15-15 (Phonska) increased stem length and starch content, while inorganic fertilizer Rock Phosphate tends to produce biomass weight than inorganic compound fertilizer 15-15-15. Interaction between inorganic fertilizer and organic fertilizer significantly increased the number of leaves and weight of tuber. In the treatment without humic, inorganic compound fertilizer 15-15-15 tended to increase Pavailable, whereas giving Rock Phosphate increased pH, P-available, and K-dd. The treatment with humic, giving P1 15-15-15 compound fertilizer and Rock Phosphate dose of R2 increased available-P and soil cation exchange capacity, while lower dose of P2 and R1 increased available-P and soil cation exchange capacity. Organic fertilizer and inorganic fertilizer did not decrease the Al-dd but tended to increase the Al-dd.
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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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