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 Resistant Organic Materials to Improve Soil Physical Properties (Infiltration and Penetrability)
Abstrak: Permasalahan utama tanah di kebun PT. Great Giant Pineapple (GGP) yaitu kandungan bahan organik yang rendah dan terjadinya pemadatan tanah. Pemadatan tanah sampai tahap tertentu dapat diatasi dengan perlakuan mekanik yang memaksa partikel tanah saling menjauh dan pemberian bahan organik untuk memicu proses agregasi tanah dan meningkatkan kemampuan menahan air, meningkatkan nilai infiltrasi tanah dan menurunkan nilai ketahanan penetrasi tanah. Penelitian ini bertujuan mengidentifikasi pengaruh aplikasi serat limbah ekstraksi bromelain dan bambu cacah terhadap infiltrasi dan ketahanan penetrasi tanah pada berbagai dosis bahan organik. Pengukuran infiltrasi konstan dilakukan dengan menggunakan alat infiltrometer dan pengamatan ketahanan penetrasi dilakukan dengan menggunakan alat penetrometer saku dan penetrologger. Kapasitas infiltrasi pada perlakuan limbah ekstraksi bromelain memiliki nilai awal sebesar 44,73 cm/jam pada bulan ke-1 dan nilai akhir sebesar 9,32 cm/jam pada bulan ke-5, sedangkan pada perlakuan bambu cacah memiliki nilai awal sebesar 47,26 cm/jam pada bulan ke-1 dan nilai akhir 15,18 cm/jam pada bulan ke-5. Ketahanan penetrasi tanah pada petak perlakuan bambu cacah memiliki nilai relatif lebih rendah dibandingkan dengan petak perlakuan limbah pemrosesan bromelain pada semua kedalaman pada bulan ke-1, bulan ke-3 dan bulan ke-5. Kurva penetrologger menunjukkan bahwa petak perlakuan limbah ekstraksi bromelain pada bulan ke-3 dan bulan ke-5 memiliki nilai relatif lebih tinggi dibandingkan petak perlakuan bambu cacah. Berdasarkan pengamatan, petak limbah ekstraksi bromelain dan bambu cacah berdampak baik terhadap infiltrasi konstan dan penetrasi tanah., The main problem of soil in PT. Great Giant Pineapple (GGP) namely are low of organic matter content and the occurrence of soil compaction. Soil compaction to a certain extent can be overcome by mechanical treatment which forces soil particles away from each other and the application of organic matter to trigger the soil aggregation process and increase the ability to hold water, to increase the infiltration and lowering the penetration resistance of soil. This study aims to identify the effect of the application of bromelain extraction waste product and chopped bamboo on soil infiltration and soil penetration resistence. Constant infiltration measurements were carried out using an infiltrometer and penetration resistance observations were carried out using a pocket penetrometer and a penetrologger. The infiltration capacity in the bromelain extraction waste product had an initial value of 44.73 cm/hour in the 1st month and a final value of 9.12 cm/hour in the 5th month, while in the chopped bamboo treatment it had an initial value of 43.78 cm/hour in the 1st month and a final value of 15.18 cm/hour at the 5th month. The soil penetration resistance of the chopped bamboo treatment plots had a relatively lower value compared to the bromelain extraction waste product treatment plots at all depths either at the 1st, 3rd or 5th month. The penetrologger curve shows that the plots treated with bromelain extraction waste product at the 3rd month and the 5th month had a relatively higher value than the plots treated with chopped bamboo. Based on observations, bromelain extraction waste product and chopped bamboo application had a positif effect on constant infiltration and soil penetration resistance.
Keyword: amelioran, bromelain extraction waste, chopped bamboo, penetrologger, 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.
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