Judul: Soil Shear Strength and Aggregate Stability in Podsolic and Latosol due to Bromelain Extraction Waste Application
Abstrak: Praktik pengolahan tanah yang intensif, terutama jika dikaitkan dengan tanaman perkebunan tahunan berumur panjang seperti nanas, dapat menyebabkan penurunan kandungan bahan organik tanah yang sejalan dengan penurunan produktivitas tanaman. PT Great Giant Pineapple Plantation mengalami penurunan produktivitas sejak 2018, yang disebabkan oleh rendahnya kandungan bahan organik dan pemadatan tanah. Sementara itu, inkorporasi bahan organik ke dalam tanah seringkali mengalami kendala karena residence time yang relatif singkat. Aplikasi limbah ekstraksi bromelain sebagai sumber bahan organik yang resisten diharapkan dapat menjawab permasalahan tersebut. Serangkaian percobaan yang terdiri dari 0, 20, 40, 60, dan 80 ton ha-1 limbah ekstraksi bromelain telah dilakukan untuk menunjukkan pengaruhnya dalam memperbaiki sifat fisik tanah. Parameter yang diamati adalah stabilitas agregat, kuat geser, dan sensitivitas tanah. Aplikasi limbah ekstraksi bromelain pada bulan kelima menunjukkan agregasi partikel tanah yang lebih stabil. Agregat yang stabil berhubungan erat dengan pori drainase tanah. Selain itu, stabilitas agregat tanah berkorelasi negatif dengan kuat geser tanah. Semakin tinggi jumlah aplikasi limbah ekstraksi bromelain, semakin rendah kekuatan geser dan sensitivitas tanah. Aplikasi limbah ekstraksi bromelain menurunkan bobot isi dan meningkatkan ruang pori tanah, yang keduanya berperan dalam menurunkan kuat geser dan sensitivitas tanah., An intensive soil tillage practice, especially when related to long-live perennial crops such as pineapples, may leads to soil organic matter content depletion which is in line with a decline in crop productivity. PT Great Giant Pineapple Plantation has experienced a decline in productivity since 2018, which was caused by low soil organic matter content and soil compaction. However, incorporation of organic matter into soil often experiences problems due to its relatively short residence time. Application of bromelain extraction waste as resistant organic matter resources might answer the problem. A set of experiments consisting of 0, 20, 40, 60, and 80 ton ha-1 of bromelain extraction waste has been done to indicate its role in increasing soil physical quality. The parameters observed were aggregate stability, shear strength, and sensitivity of soil. The application of bromelain waste extraction in the fifth month showed a more stable aggregation of soil particles. Stable aggregates are closely related to soil drainage pores. In addition, soil aggregate stability is negatively correlated with soil shear strength. The higher amount of bromelain extraction waste applications, the lower the shear strength and sensitivity of the soil. The application of bromelain extraction waste has been shown to reduce bulk density and increase pore space, both of which play a role in reducing soil shear strength and sensitivity.
Keyword: bromelain, karbon organik tanah, kuat geser, sensitivitas tanah, stabilitas agregat

Judul: Utilization of Weatherable Organik Materials for Improvement of Soil Physical Properties (Soil Permeability and Shear Strength)
Abstrak: Penurunan produktivitas pertanian di Indonesia umumnya disebabkan oleh terjadinya penurunan kualitas tanah akibat penggunaan tanah secara terus-menerus. Penurunan produktivitas juga dialami oleh PT Great Giant Pineapple (GGP) sejak 2018. Hal tersebut terjadi karena kandungan bahan organik yang rendah dan terjadinya pemadatan tanah. Pemadatan tanah dapat diatasi dengan pemberian bahan organik. Pemberian bahan organik sering mengalami kendala akibat residence time-nya yang relatif singkat terutama untuk tanaman berumur panjang seperti nanas. Salah satu alternatif adalah dengan memanfaatkan limbah ekstraksi bromelain yang tersedia. Penelitian ini bertujuan mengidentikasi pengaruh aplikasi limbah ekstraksi bromelain dan bambu cacah berbagai dosis terhadap proses agregasi, kekuatan geser tanah dan permeabilitas tanah. Penelitian dilakukan di lokasi 88 C2 Kebun PT GGP, Lampung Tengah dengan metode rancangan acak kelompok (RAK) faktorial. Tanah dengan perlakuan limbah ekstraksi bromelain memiliki indeks stabilitas agregat tanah yang lebih tinggi dibandingkan tanah dengan perlakuan bambu cacah. Laju permeabilitas tanah mengalami penurunan pada 5 bulan setelah aplikasi bahan organik baik pada limbah ekstraksi bromelain maupun bambu cacah. Pemberian bahan organik memicu pertumbuhan akar tanaman nanas sehingga meningkatkan nilai kekuatan geser tanah. Semakin tinggi dosis bahan organik yang diberikan maka semakin baik dampaknya terhadap sifat fisik tanah., The decline in agricultural productivity in Indonesia is generally caused by a decrease in soil quality due to continuous land use. PT Great Giant Pineapple (GGP) has also experienced a decline in productivity since 2018. This is due to the low organik matter content and soil compaction. Soil compaction can be overcome by adding organik matter. The application of organik matter often experiences problems due to its relatively short residence time, especially for long-lived plants such as pineapple. One alternative is to utilize the available bromelain extraction waste. This study aims to identify the effect of the application of bromelain extraction waste and various doses of chopped bamboo on the aggregation process, soil shear strength and soil permeability. The research was conducted at location 88 C2 of PT GGP's plantation, Central Lampung with a factorial randomized block design (RBD) method. Soil treated with bromelain waste extraction had a higher soil aggregate stability index than soil treated with chopped bamboo. The rate of soil permeability decreased 5 months after the application of organik matter in both bromelain extraction waste and chopped bamboo. The application of organik matter triggers the growth of pineapple plant roots thereby increasing the shear strength value of the soil. The higher the dose of organik matter given, the better the impact on soil physical properties.
Keyword: aggregate stability, bromelain, residence time, soil compaction

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.
Keyword: