Karakteristik Kadar Air, Kemantapan Agregat, Berat Isi Tanah dan Bahan Organik Pada Tanah Terdampak Likuifaksi di Kelurahan Petobo dan Desa Jono Oge, Sulawesi Tengah.

Alifa Taskiya, Mayank and Prof. Dr. Ir. Zaenal Kusuma, SU. (2023) Karakteristik Kadar Air, Kemantapan Agregat, Berat Isi Tanah dan Bahan Organik Pada Tanah Terdampak Likuifaksi di Kelurahan Petobo dan Desa Jono Oge, Sulawesi Tengah. Sarjana thesis, Universitas Brawijaya.

Abstract

Indonesia memiliki letak geografis yang unik yaitu berada pada pertemuan tiga lempeng besar yaitu Lempeng Eurasia, Lempeng Indo-Australia, dan Lempeng Pasifik menyebabkan Indonesia menjadi negara yang rawan bencana alam. Pada tahun 2018 terjadi bencana alam gempa bumi, tsunami, dan likuifaksi di Kota Palu, Kabupaten Sigi, dan Kabupaten Donggala. Likuifaksi merupakan proses hilangnya kekuatan tanah akibat naiknya tekanan pori tanah. Tanah mengalami perubahan signifikan dimana permukaan tanah rusak, struktur tanah yang berubah dari padat menjadi cair, serta terjadinya percampuran lapisan tanah. Likuifaksi menyebabkan penurunan produktivitas lahan akibat kerusakan tanah, 30 ha dari 50 ha lahan pertanian hanyut, 5.700 ha sawah kekeringan dan 65% petani kehilangan lahan pertanian dan hanya 35% petani yang masih memiliki lahan pasca terjadinya likuifaksi di Kabupaten Sigi, Sulawesi Tengah. Berdasarkan Peraturan Daerah Kabupaten Sigi Nomor 1 mengenai tata ruang wilayah Kabupaten Sigi dan peta zona ruang rawan bencana Kota Palu merekomendasikan zona dengan potensi likuifaksi sangat tinggi dimanfaatkan sebagai kawasan lindung, kawasan pertanian, dan perkebunan. Tujuan penelitian adalah mengetahui karakteristik dan perbedaan kadar air, kemantapan agregat, berat isi tanah dan kandungan bahan organik di zona runtuhan, zona akhir, dan kontrol pada tanah terlikuifaksi. Penelitian dilakukan bulan Januari hingga Juni 2023 pada tanah terdampak likuifaksi di Kelurahan Petobo dan Desa Jono Oge, Sulawesi Tengah. Penelitian menggunakan Rancangan Acak Kelompok (RAK) dengan 5 titik pengambilan sampel dan 9 kali ulangan yang berada pada masing-masing zona runtuhan dan zona akhir tanah terlikuifaksi. Parameter yang diamati meliputi kadar air tanah pada pF 2,5 dan kadar air jenuh , kemantapan agregat tanah, berat isi tanah dan kandungan bahan organik. Analisa data menggunakan uji T dengan tingkat toleransi kesalahan 5%. Hasil penelitian menujukkan adanya penurunan kadar air pF 2,5 pada tanah setelah terlikuifaksi. Penurunan terbesar terjadi pada daerah JLR yang mengalami penurunan sebesar 7,89% sedangkan perubahan kadar air terkecil terdapat pada PLA dimana tanah mengalami penurunan kadar air sebesar 3,98%. Kadar air pF 2,5 tertinggi berada pada tanah JK dengan nilai sebesar 24,24% dan kadar air kapasitas lapang terendah terdapat pada JLA sebesar 16,35%. Pada parameter kemantapan agregat dan kandungan bahan organik tidak terjadi perubahan yang signifikan setelah likuifaksi dimana kemantapan agregat pada kedua daerah terlikuifaksi dan tidak terlikuifaksi tergolong kurang mantap dan bahan organik tanah tergolong sangat rendah hingga rendah. Nilai berat isi tanah setelah terjadi fenomena likuifaksi meningkat sebesar 0,37 gr.cm−3 sedangkan daerah yang mengalami kenaikan nilai berat isi terkecil terdapat pada JLR hanya sebesar 0,15 gr.cm−3. Hal ini dapat terlihat penurunan bahan organik pada tanah sebesar 0,54%. Perlu dilakukan perbaikan kualitas lahan setelah likuifaksi seperti perbaikan bentang lahan, pemberian bahan organik tanah untuk memperbaiki struktur, kemantapan agregat tanah, dan pori tanah. Konservasi secara vegetatif juga dapat dilakukan dengan pemilihan komoditas sesuai kondisi lahan.

English Abstract

Indonesia has a unique geographical location, which is located between three large plates, namely the Eurasian, the Indo-Australian, and the Pacific Plate, making Indonesia a country prone to natural disasters. In 2018 the biggest disaster of earthquakes, tsunamis, and liquefaction happened in Palu City, Sigi, and Donggala Regency. Liquifaction is the process of loss of soil strength due to increased soil pore pressure. The soil undergoes significant changes where the soil surface is damaged, the soil structure changes from solid to liquid, and the mixing of soil layers. Liquefaction caused a decrease in land productivity due to soil destruction, 30 of 50 ha of agricultural land was washed away, 5,700 ha of rice fields were drought and 65% of farmers lost agricultural land and only 35% of farmers still owned land after liquefaction in Sigi Regency, Central Sulawesi. Based on the Regional Regulation of Sigi Regency Number 1 regarding the spatial planning of Sigi Regency and the map of disaster-prone space zones, Palu City recommends zones with very high liquefaction potential be used as protected areas, agricultural areas, and plantations. The purpose of the study was to determine the characteristics and differences in water content, aggregate stability, soil density, and organic matter in several regions such as collapse zone, final zone, and control on liquefied soil. The study was conducted from January to June 2023 on land affected by liquefaction in Petobo and Jono Oge Village, Central Sulawesi. The study used Group Random Design (RAK) with 5 sampling points and 9 repeats located in each collapse zone and final zone of liquefaction soil. Parameters observed include water content at pF 2.5 and saturated moisture content, aggregate stability, soil density and organic matter. Data analysis using a T test with an error tolerance rate of 5%. The results showed a decrease in water content pF 2.5 in the soil after liquefaction. The largest decrease occurred in the JLR area which decreased by 7.89% while the smallest change in water content was found in PLA where the soil experienced a decrease in water content by 3.98%. The highest pF 2.5 moisture content is in JK soil with a value of 24.24% and the lowest field capacity moisture content is found in JLA at 16.35%. In the parameters of aggregate stability and organic matter content, there was no significant change after liquefaction, where the aggregate stability in both liquefaction and nonliquefaction areas was classified as less stable and soil organic matter was classified as very low to low. The weight value of soil contents after the liquefaction phenomenon increased by 0.37 gr.cm−3 while the area that experienced the smallest increase in the weight value of the contents was found in JLR only by 0.15 gr.cm−3. This can be seen a decrease in organic matter in the soil by 0.54%. It is necessary to improve land quality after liquefaction such as landscape improvement, addition of organic matter to improve structure, aggregate stability, and soil pores. Vegetative conservation can also be done by selecting right commodities according to land conditions.

Item Type:	Thesis (Sarjana)
Identification Number:	052304
Uncontrolled Keywords:	likuifaksi, kadar air tanah, kemantapan agregat, bahan organik, berat isi
Divisions:	Fakultas Pertanian > Ilmu Tanah
Depositing User:	Unnamed user with username ismiatun
Date Deposited:	09 Jan 2024 07:07
Last Modified:	09 Jan 2024 07:20
URI:	http://repository.ub.ac.id/id/eprint/206561

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