Judul: Perbaikan Sifat Kimia Tanah Masam, Produksi, dan Serapan P Tanaman Kacang Tanah (Arachis hypogaea) dengan Pemberian Pupuk Fosfat Alam
Abstrak: Potential of land resources in Indonesia is very large. Indonesia has 148 million ha of upland. Climate variation, specifically precipitation in most areas of Indonesia is relatively high therefore leaching of bases in the soil mostly high. It causes the low content of bases in soil, and then the soil become acid and have nutrients deficiency. About 102.8 million ha or 69.5 % of the total upland in Indonesia have acid soil. The utilization of acid soil for agriculture have several problems such as P-deficiency. It is due to the phosphate ions is adsorbed by the various component in the soil, such as Fe and Al ions, and Fe and or Al hydrous oxide. One of the efforts to overcome the P-deficiency is to apply rock phosphate into acid soil. The use of rock phosphate as fertilizer because highly soluble in the acid soil condition. Therefore, rock phosphate is appropriate as a source of P fertilizer in acid soil. The objectives of this research were to study the effect of rock phosphate fertilizer on the improvement acid soil quality, on groundnut yield, and P uptake of groundnut plant (Arachis hypogaea) in Latosol (Oxyc dytropept) Darmaga, Bogor. The experimental design was used is a randomized complete block design with one factor, that is dosage of phosphate fertilizers. Phosphate Fertilizer used in this experiment were rock phosphate and SP-36. Phosphate fertilizer dosages were: 0% (as a control treatment), Std 100%, Std 50% + P 50%, Std 25% + P 75%, P 100%, P 125%, and P 150%. The results of the study showed that rock phosphate fertilizer significantly increased the soil pH, exchangeable Ca, the uptake of Ca and P of groundnut plant. The phosphate fertilizer treatments were not increase significantly different in the growth, weight of pod, weight of seed, and percentage of full pod. However, the rock phosphate treatments resulted the percentage of full pod (87.76%-90.01%) was higher than standard fertilizer treatment (86.51%).
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Judul: Pengaruh Pemberian Fosfat Alam Terhadap Perubahan Sifat Kimia Tanah, dan Kadar Hara Pada Tanaman Jagung (Zea mays)
Abstrak: The utilization of acid soil for agriculture faced several obstacles, including P deficient. It is because P ions sorbed by various soil components, such as Fe-Al ions, and Fe-Al hydrous oxides. One of the efforts made to overcome this problem is the use of natural phosphate in acid soils. This study aims to determine the effect of natural phosphate fertilizers in soil chemical properties and nutrients rate in plant of Latosol (Oxyc Dystrudept) Darmaga. Experimental design used in this study was a randomized design with a single factor, named P fertilizer. Source of P fertilizer used in this study is a natural phosphate and SP-36. Treatment dosage of P fertilizer are, control I (0%), control II (N + K), Std 100% (N+K+SP36), RP 50%, RP 100%, RP 150%, RP 200%, (N + K 50%) + RP 50%, and (N + K 50%) + RP 100%. The results showed that the phosphate fertilizer did not significantly affect soil pH, exchangeable-Al, available-P, exchangeable-Ca, and exchangeable-Mg. phosphate fertilizer have significantly affect only in exchangeable-K. Meanwhile, phosphate not significantly affect the rate of Mg, K, Ca, P and N. Rock phosphate’s application significantly affected the growth of maize on 4 week after planting (MST) and 6 MST. Rock phosphate’s application did differ significantly on increasing cob with husk’s weight and cob without husk’s weight. But rock phosphate’s application did not differ significantly on total weight of stover. The highest percent of crop value in treatment who give rock phosphate fertilizer there is in treatment of RP 150% with 158.1%, and the lowest percent of crop value there is in treatment of (N+K 50%) + RP 50% with 98.6%, and lowest in all treatment there in treatment of Control I with 74.7%. From result of crop value can get a conclusion that rock phosphate fertilizer is better than standard fertilizer (SP36).
Keyword: acid soil, maize, phosphate

Judul: Penggunaan Teorema Homeomorphy 2-Manifold dan Teorema Euler Poincare pada Torus 𝑇�� dan Simplicial Complex 𝐾��
Abstrak: Two dimensional topological spaces are said to be homeomorphic if they have the same topological invariant, where one of topological invariant used is an Euler characteristic. Homeomorphy 2-Manifold’s Theorem and Euler Poincare’s Theorem are used to distinguish two topological spaces. Homeomorphy 2-Manifold’s Theorem uses Euler characteristic to identify two dimensional topological spaces. Euler Poincare’s Theorem is an alternative way to find Euler characteristic with Betti number, which is topological invariant as well. The objective of this paper is to investigate the homeomorphism of torus 𝑇����� and simplicial complex 𝐾�����. Topological space torus and simplicial complex 𝐾����� have the same Euler characteristic, which is two. Based on Homeomorphy 2-Manifold’s Theorem topological space torus 𝑇����� and simplicial complex 𝐾����� is homeomorphic.
Keyword: simplicial, torus, Euler, homeomorphism, topology