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: Soil Penetrability in Podzolic and Latosol due to the Addition of Bromelain Extraction Waste and Chopped Bamboo
Abstrak: Peningkatan ketahanan penetrasi menyebabkan pertumbuhan akar tanaman terhambat sehingga mengakibatkan penurunan produksi tanaman. Oleh karena itu, mempertahankan ketahanan penetrasi tanah agar tetap rendah merupakan salah satu syarat untuk mempertahankan produksi tanaman. Salah satu upaya yang dapat dilakukan untuk mempertahankan penetrabilitas tanah adalah pemberian bahan organik. Suatu penelitian yang bertujuan untuk mengetahui ketahahanan penetrasi tanah akibat penambahan bahan organik dengan dosis yang berbeda pada tanah Podsolik dan Latosol telah dilakuan di rumah kaca kebun Pendidikan Cikabayan IPB. Bahan organik berasal dari limbah industri perkebunan berupa limbah ekstraksi bromelin dan bambu cacah. Penelitian ini menggunakan rancangan acak lengkap yang terdiri atas dua perlakuan jenis tanah, dua perlakuan bahan organik dan lima perlakuan dosis bahan organik dengan inkubasi selama lima bulan. Hasil penelitian menunjukkan bahwa nilai ketahanan penetrasi tanah pada perlakuan bahan organik limbah ekstraksi bromelin dan bambu cacah selama lima bulan inkubasi belum berubah nyata. Nilai ketahanan penetrasi untuk tanah podsolik pada bulan pertama, ketiga dan kelima adalah berturut-turut berkisar 0.29-0.54 kg/cm2, 0.75-0.92 kg/cm2, 0.71-0.87 kg/cm2 sementara untuk Latosol adalah 0.33-0.71 kg/cm2, 0.54-0.88 kg/cm2, dan 0.46-0.79 kg/cm2. Ketahanan penetrasi akan meningkat dengan menurunnya kadar air, namun peningkatan ketahanan penetrasi akibat penurunan kadar air pada Podsolik lebih besar daripada Latosol., Increased penetration resistance causes stunted plant root growth resulting in decreased crop production. Therefore, maintaining low penetration resistance is one of the efforts for maintaining crop production. One effort that can be done to maintain soil penetrability is the application of organic matter. A study aimed at determining soil penetrability as response to the addition of organic matter at different doses in Podzolic and Latosol soils was carried out in the greenhouse of the education garden Cikabayan IPB. The organic material used came from industrial plantation waste in the form of bromelain extraction waste and chopped bamboo. This study used a completely randomized design consisting of two treatments of soil type, two treatments of organic matter, and five doses of organic matter with incubation time for five months. The results showed that the value of soil penetrability in the treatment of organic matter from bromelain extraction waste and chopped bamboo with five months incubation had not changed significantly. Penetration resistence values for podzolic soils in the first, third, and fifth months ranged from 0.29-0.54 kg/cm2, 0.75-0.92 kg/cm2, 0.71-0.87 kg/cm2 respectively while for Latosol were 0.33-0.71 kg/cm2, 0.54- 0.88 kg/cm2, and 0.46-0.79 kg/cm2. Penetration resistance will increase with decreasing water content, but the increase in penetration resistance due to decreased water content in Podzolic is greater than that in Latosol.
Keyword: Bromelain Extraction Waste, Chopped Bamboo, Soil Penetrability

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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