Judul: Aggregate Stability and Permeability in Podsolic and Latosol due to the addition of brown coal
Abstrak: Podsolik merupakan tanah marginal yang banyak dimanfaatkan untuk lahan perkebunan. Secara umum, Podsolik memiliki tingkat kesuburan yang rendah karena kandungan bahan organik tanah yang rendah. Rendahnya kandungan bahan organik tanah semakin jelas jika tanah diolah secara intensif. Pengolahan tanah intensif cenderung menyebabkan kandungan bahan organik tanah menurun. Penambahan bahan organik dilakukan untuk memperbaiki dan mempertahankan kualitas sifat fisik tanah. Namun, pengaruh penambahan bahan organik pada umumnya relatif singkat sehingga kurang efektif untuk pertanian jangka panjang. Aplikasi bahan pembenah tanah tahan lapuk pengganti bahan organik seperti batubara muda dapat menjawab permasalahan tersebut. Suatu penelitian yang bertujuan untuk menguji pengaruh aplikasi batubara muda terhadap stabilitas agregat dan permeabilitas tanah Podsolik dan Latosol telah dilakukan di rumah kaca dengan waktu inkubasi 5 bulan. Penelitian menggunakan rancangan acak lengkap dengan dosis batubara muda sebagai perlakuan penelitian. Dosis batubara muda yang diterapkan adalah lima taraf yaitu 0, 20, 40, 60 dan 80 ton/ha. Hasil penelitian menunjukkan bahwa stabilitas agregat tanah Podsolik lebih rendah dari pada Latosol karena kandungan bahan organik di Latosol lebih tinggi. Permeabilitas tanah Podsolik lebih tinggi dibandingkan Latosol karena persentase kandungan pasir Podsolik lebih dominan. Dengan masa inkubasi 5 bulan, pemberian batubara muda dapat meningkatkan indeks stabilitas agregat dan permeabilitas tanah baik pada Podsolik maupun Latosol. Semakin tinggi dosis, semakin tinggi indeks stabilitas agregat dan permeabilitas tanah., Podsolic is a marginal soil that is widely used for plantation land. In general, Podsolic has low fertility due to low soil organic matter content. The low soil organic matter content becomes clearer if the soil is cultivated intensively. Intensive soil tillage tends to cause the decline of soil organic matter content. The addition of organic matter can improve and maintain soil physical properties. However, the effect of adding organic matter is generally relatively short, making it less effective for long-term agriculture. Application of resistant soil amendments as a substitute for organic matter such as brown coal might answer the problem. A study aimed at examining the effect of brown coal application on soil aggregate stability and permeability of Podsolic and Latosol was carried out in a greenhouse with an incubation time of 5 months. This study used a completely randomized design with a rate of brown coal as the research treatment. The rate of brown coal application consists of five levels, namely 0, 20, 40, 60 and 80 tons/ha. The result showed that soil aggregate stability of Podsolic was lower than Latosol due to the higher organic matter content in Latosol. Soil permeability of Podsolic was higher than Latosol since the percentage of sand content of Podsolic is more dominant. After 5 months of incubation, the provision of brown coal can increase the soil aggregate stability and permeability in Podsolic and Latosol. The higher the rate of brown coal application, the higher the soil aggregate stability and permeability.
Keyword: stabilitas agregat, permeabilitas, batubara muda, bahan organik

Judul: The Role of Resistant Organic Materials Bromelain Extraction Waste and Brown Coal on Penetration Resistance of Podzolic and Regosol
Abstrak: Pengolahan tanah secara intensif dapat menyebabkan terjadinya pemadatan tanah. Pemadatan tanah merupakan indikator penurunan kualitas tanah. Pemadatan tanah dapat diatasi dengan pemberian bahan organik. Pelapukan bahan organik yang cepat mengakibatkan kebutuhan bahan organik hanya akan terpenuhi di awal masa pertumbuhan. Untuk tanaman berumur panjang dengan kerapatan tinggi seperti nanas, penambahan bahan organik sulit dilakukan di tengah musim tanam. Dalam kasus seperti demikian perlu dilakukan pemberian bahan organik tahan lapuk diantaranya adalah limbah ekstraksi bromelin asal bonggol nanas dan batubara muda. Penelitian bertujuan mengetahui ketahanan penetrasi pada jenis tanah yang memiliki kelas tekstur berbeda akibat pemberian bahan organik tahan lapuk limbah ekstraksi bromelin asal bonggol nanas dan batubara muda. Parameter yang diamati adalah paramater terkait kepadatan tanah yaitu ketahan penetrasi. Penelitian dilakukan di rumah kaca dengan menggunakan rancangan acak lengkap tiga faktor, yaitu dua jenis tanah, dua jenis bahan organik, dan lima dosis bahan organik. Sebaran nilai ketahanan penetrasi Podsolik dan Regosol pada bulan pertama berkisar 0–0.46 kg/cm2 , pada bulan ketiga berkisar 0.46–0.79 kg/cm2 , dan bulan kelima berkisar antara 0.58–0.88 kg/cm2 . Perlakuan limbah ekstraksi bromelin asal bonggol nanas dan batubara muda belum memberikan pengaruh nyata terhadap ketahanan penetrasi pada Podsolik dan Regosol selama lima bulan inkubasi., Intensive tillage seems to be more crucial in causing soil compaction. Soil compaction can be overcomed by adding organic matter. The rapid weathering of organic matter results in the need for organic matter application at the very beginning of the growth season. The addition of organic matter is difficult to be applied in the middle of the growing season for high density perennial plants, such as pineapple. In such cases, it is necessary to apply a weather-resistant organic matter, namely pineapple based bromelain extraction waste and brown coal. The aim of this study was to determine the penetration resistance of soil on different texture classes due to the application of weather-resistant organic matter pineapple based bromelain extraction waste and brown coal. The parameter observed ware related to soil density i.e. penetration resistance. The study was conducted in a greenhouse using a completely randomized design with three factors, namely two types of soil, two types of organic matter, and five doses of organic matter. The result showed that the penetrability values of Podzolic and Regosol soils in the first month of application ranged from 0–0.46 kg/cm2 , in the third month of application it ranged from 0.46–0.79 kg/cm2 , and in the fifth month of application it ranged from 0.58–0.88 kg/cm2 . Treatment of pineapple based bromelain extraction waste and brown coal had no significant effect on the penetration resistance of Podzolic and Regosol during five months of incubation.
Keyword: Brown coal, Bromelain extraction waste, Penetration resistance

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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