Judul: Infiltrasi dan Penetrasi Tanah PT GGP Setelah Sebelas Bulan Aplikasi Bahan Organik Tahan Lapuk
Abstrak: Lahan PT Great Giant Pineapple (PT GGP) Lampung Tengah mengalami penurunan produktivitas akibat pengolahan lahan secara intensif selama 40 tahunan. Permasalahan yang dihadapi sejak tahun 2018 adalah rendahnya bahan organik dan terjadinya pemadatan tanah sehingga akar mengalami hambatan dalam menyuplai air dan hara yang dibutuhkan tanaman. Salah satu upaya untuk mengatasi pemadatan tanah di PT GGP adalah dengan pemberian bahan organik tahan lapuk seperti Limbah Ekstraksi Bromelain (LEB) dan Bambu Cacah (BC). Hal ini dilakukan karena penambahan bahan organik pada pertengahan fase umur nanas sulit dilakukan akibat kerapatan tanaman yang masif. Penelitian yang bertujuan untuk mengidentifikasi pengaruh bahan organik tahan lapuk setelah sebelas bulan aplikasi terhadap infiltrasi dan penetrasi tanah telah dilaksanakan di Lahan 88C2 Kebun PT GGP, Lampung Tengah. Rancangan percobaan yang digunakan adalah Rancangan Acak Kelompok (RAK). Pengukuran infiltrasi dilakukan dengan menggunakan alat double ring infiltrometer sementara pengamatan penetrasi tanah menggunakan alat penetrometer saku. Nilai infiltrasi pada bulan ke-11 mengalami penurunan dibandingkan dengan bulan ke-1 dan bulan ke-5 sedangkan nilai penetrasi tanahnya mengalami peningkatan. Penurunan infiltrasi dan peningkatan penetrasi pada bulan ke-5 dan ke-11 sudah menunjukkan pola mendatar. Peningkatan dosis bahan organik yang diberikan berpengaruh terhadap peningkatan nilai penetrasi dan menyebabkan penurunan infiltrasi setelah sebelas bulan aplikasi., The agricultural land of PT Great Giant Pineapple (PT GGP) Central Lampung experienced a decrease in productivity due to intensive land management during 40 years. The problem occurred since 2018 concerning low organic matter content and soil compaction so that the roots experience obstacles in supplying water and nutrients needed by plants. One of the efforts to overcome soil compaction at PT GGP is by providing a resistant organic matter such as Bromelain Extraction Waste and Chopped Bamboo trees since the addition of organic matter in the middle of the pineapple growth phase is difficult due to the massive density of the plant. Research aimed to identify the influence of a resistant organic matter after eleven months of application on soil infiltration and soil penetration resistant (SPR) has been carried out on Plantation Land 88C2 of PT GGP, Central Lampung. The research used the Randomized Block Design (RBD) method. Infiltration measurement was carried out using a double ring infiltrometer while SPR observation was carried out using a pocket penetrometer. The infiltration value after eleven months of application decreased compared to the value of the first month and the fifth month of application while the SPR value increased. The decrease in infiltration and increase in SPR in the fifth and eleven months have already leveled off. The increase of organic matter dose applied after eleven months of application has affected to increase the SPR value and lead to decrease soil infiltration.
Keyword: chopped bamboo, bromelain extraction waste, soil compaction, resistant

Judul: Permeability and Shear Strength of PT GGP Pineapple Land after Eleven Months of Resistant Organic Matter Application
Abstrak: Penurunan produktivitas pertanian pada umumnya disebabkan oleh penurunan kualitas tanah akibat penggunaan terus-menerus. Penelitian ini dilakukan pada lahan PT Great Giant Pineapple (GGP) yang mengalami penurunan produktivitas buah nanas seiring terjadinya penurunan kualitas tanah. Penurunan kualitas tanah terjadi karena rendahnya pemberian bahan organik yang sesuai dengan usia tanaman nanas, sehingga mengakibatkan pemadatan tanah. Dalam penelitian ini, limbah ekstraksi bromelain dan bambu cacah dipilih sebagai sumber bahan organik tahan lapuk karena mampu mempertahankan residence time pada pengaplikasian nya di lahan. Tujuan penelitian adalah menguji pengaruh bahan organik tahan lapuk setelah 11 bulan aplikasi terhadap permeabilitas dan kuat geser tanah. Metode penelitian yang digunakan adalah rancangan acak kelompok (RAK) di lokasi lahan 88 C2, PT GGP, Lampung Tengah. Hasil penelitian menunjukkan bahwa perlakuan limbah ekstraksi bromelain menghasilkan nilai laju permeabilitas yang lebih rendah dibandingkan dengan perlakuan bambu cacah. Laju permeabilitas pada kedua perlakuan mengalami penurunan setelah 11 bulan aplikasi bahan organik dibandingkan dengan setelah aplikasi 5 bulan. Nilai Kekuatan geser tanah meningkat seiring bertambahnya usia tanaman pada bulan 11, terutama pada kedalaman 0-10 cm, 10-20 cm, dan 20-30 cm. Pemberian dosis bahan organik yang lebih tinggi memberikan perbaikan sifat fisik tanah yang lebih baik., The decline in agricultural productivity is generally caused by a decrease in soil quality due to continuous use. This research was conducted on PT Great Giant Pineapple (GGP)’s land which experienced a decrease in pineapple productivity along with a decrease in soil physical quality. The decline in soil quality occurred due to the low provision of organic matter in accordance with the age of pineapple plants, resulting in soil compaction. In this study, bromelain extraction waste and chopped bamboo were chosen as a source of resistant organic matter since they are able to maintain quite long residence time in land after application. The research objective was to examine the effect of resistant organic matter after 11 months of application on permeability and soil shear strength. The research was held based on Randomized Block Design (RBD) at the location of 88 C2 land of PT GGP, Central Lampung. The results showed that the bromelain extraction waste treatment produced a lower permeability rate than the chopped bamboo treatment. The permeability rate in both treatments decreased after 11 months of organic matter application compared to the 5 months of application. Soil shear strength values increased with plant age of month 11, especially at depths of 0-10 cm, 10-20 cm, and 20-30 cm. Application of higher doses of resistant organic matter provided better improvements in soil physical properties.
Keyword: bromelain, organic matter, permeability, shear strength

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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