Judul: Aplikasi Bahan Humat dengan Carrier Zeolit untuk Meningkatkan Produksi Tanaman Kangkung (Ipomoea reptans Poir) pada Latosol Dramaga
Abstrak: Upaya meningkatkan produktivitas tanah pertanian dapat dilakukan dengan pemberian bahan organik dalam jumlah besar secara terus-menerus. Cara ini terkendala oleh biaya dan ketersediaan bahan. Oleh karena itu, diperlukan bahan organik lain yang dapat diberikan dalam jumlah sedikit namun pengaruhnya sama. Bahan tersebut adalah bahan humat. Aplikasi bahan humat dalam bentuk cair mudah tercuci oleh air hujan sehingga diperlukan bahan pengikat dalam bentuk carrier yang dapat memperlambat laju tercucinya bahan humat. Zeolit merupakan mineral berongga yang memiliki kapasitas tukar kation (KTK) tinggi adalah bahan yang dapat digunakan sebagai carrier bahan humat. Tujuan penelitian ini untuk mengetahui pengaruh bahan humat dengan carrier zeolit terhadap sifat kimia tanah setelah panen, kadar hara tanaman, serapan hara tanaman, serta pertumbuhan dan produksi kangkung darat. Penelitian ini menggunakan rancangan acak kelompok dengan 10 perlakuan dan 3 ulangan. Perlakuan adalah (a) kontrol (b) zeolit 20 kg/ha (Z20), (c) empat perlakuan bahan humat jenis A dan B dengan dengan pengenceran 100 kali (HA5, HA10, HB5, dan HB10) dan (d) empat perlakuan kombinasi bahan humat dan zeolit (HA5Z20, HA10Z20, HB5Z20, dan HB10Z20). Hasil penelitian menunjukkan bahwa pemberian bahan humat dengan carrier zeolit meningkatkan sifat kimia tanah kecuali Mg, kadar dan serapan hara N, P, K, Ca, Mg, Na, Cu, Mn, Fe, dan Zn pada tanaman, meningkatkan pertumbuhan dan produksi tanaman kangkung darat dengan produksi tertinggi dicapai pada perlakuan HA10Z20 dengan peningkatan hampir 2.5 kali lipat dibandingkan kontrol.
Keyword: bahan humat, carrier zeolit, produksi kangkung, kadar hara, serapan hara

Judul: Aplikasi Bahan Humat dengan Carrier Zeolit untuk Meningkatkan Produksi Tanaman Jagung (Zea mays) pada Latosol Bogor.
Abstrak: Indonesia is one of wet-tropical countries having high temperature and rainfall so that leaching in soil is very intensive. This condition makes nutritions in the soil decrease significantly and declining crop production. Many efforts have been done for increasing food crop production without damaging soil characteristics and causing environmental pollution such as application of chemical fertilizer with accurate dossage accompanied by addition of organic fertilizer. However, soil need organic fertilizer in large amount for improving soil characteristics and increase food crop production. Humic substance which is extracted from organic matter can substitute organic fertilizer. Generally, humic substance is applied in liquid form with a small amount, therefore it need a carrier to make the application easy and the humic substance is not easily leached. Zeolite that has porous structure is material potential to be used as carrier of humic substance. Application of humic substance with zeolite as carrier is expected to increase production of food crop such as corn. This experiment consists of field experiment that was conducted in agricultural land at Sindangbarang District, Bogor City, green house experiment that was conducted in University Farm IPB, and soil and plant analysis in chemist and soil fertility, Laboratory of the Department of Soil Science and Land Resources, Faculty of Agriculture, Bogor Agricultural University. Field experiment is arranged in a randomized block design 2 factorial with 2 replications. Treatment is consist of 1 control, 3 humic substance treatment (A5, A10, and A15), 2 zeolite treatment (Z10, and Z20), and 6 combination humic substance and zeolite treatment (A5Z10, A10Z10, A15Z10, A5Z20, A10Z20, and A15Z20). The results showed that application of humic substance with zeolite as carrier gave a better effect for increasing corn production than application of humic substance or zeolite itself. Humic substance with zeolite as carrier can increase P-available and CEC of soil. Moreover, humic substance with zeolite as carrier increased nitrogen level in corn leaf. The growth of corn increased with the increase of root weight and plant height. The optimum and profitable dosage of humic substance with zeolite as carrier was 10 liters humic substance/ha with 20 kg zeolite as carrier/liter humic substance because it showed the biggest increase corn production or 19% increase than plants without application of humic substance with zeolite as carrier and gave profit up to Rp 1.212.000,00/ha per planting season. This dosage can be recommend by farmer.
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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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