Hidayat, Rohmat (2019) Studi Ketahanan Geser Tanah Pada Berbagai Kerapatan Akar Pohon. Sarjana thesis, Universitas Brawijaya.
Abstract
Perubahan iklim menyebabkan cuaca ekstrim dan peningkatan curah hujan rata-rata di beberapa daerah di Indonesia. Hal tersebut berpotensi memicu terjadinya bencana alam longsor dan degradasi lahan pada daerah berlereng terjal. Tanah longsor berhubungan dengan gaya penahan lereng bawah yaitu ketahanan geser tanah dan kekuatan akar. Penelitian ini bertujuan mengkaji pengaruh peningkatan kerapatan perakaran pohon terhadap peningkatan ketahanan geser tanah dan mengkaji pengaruh tingkat kadar air tanah terhadap ketahanan geser tanah. Penelitian lapangan dilakukan pada bulan April – Juni 2019 di KHDTK UB Forest, Dusun Tumpangrejo (Buntoro) dan Dusun Sumberwangi pada daerah dengan kemiringan 26-28° (sangat terjal). Sedangkan analisa tanah dilakukan di laboratorium Fisika tanah & Biologi tanah Fakultas Pertanian Universitas Brawijaya. Pengukuran akar dilakukan pada 5 jenis pohon yang umum dijumpai disepanjang jalur survei yaitu tanaman kopi robusta (Coffea Canephora), alpukat (Persea americana), dadap (Erythrina variegata), petai (Parkia speciosa), dan gamal (Gliricida sepium). Pengukuran masing-masing jenis pohon dilakukan sebanyak 5 kali. Pengambilan contoh tanah dan akar untuk pengukuran ketahanan geser tanah dilakukan pada 2 zonasi/lereng, yaitu zona di atas pangkal batang dan di bawah pangkal batang. Contoh diambil dari kedalaman tanah 0-10 cm menggunakan ring berukuran 10x10 cm. Parameter yang diamati adalah ketahanan geser tanah Soil shear strenght (Direct Shear Strees Method), Root lenght per volume (Lrv), Dry Root per Volume (Drv), Specrol (Spesific root lenght density, Lrv/Drv), dan pengamatan ketahanan geser tanah dengan perlakuan kadar air. Hasil penelitian ini menunjukkan nilai Lrv dan Drv tertinggi yaitu pada tanaman kopi dengan nilai Lrv 0,272 cm.cmˉ³ dan nilai Drv 0,00064 g.cmˉ³. . Nilai tahan geser tanah tertinggi yaitu terdapat pada tanah di sekitar tanaman gamal (1904 Kpa), namun bila kerapatan akar turut dipertimbangkan dalam perhitungan nilai tahan geser tanah maka nilai tahan tertinggi pada tanaman kopi (1444 Kpa) dan terendah pada tanaman gamal (57 Kpa). Tingkat kerapatan akar meningkatkan nilai tahan geser, semakin tinggi nilai Lrv diikuti oleh peningkatan nilai tahan geser tanah (R²= 0,52). Ketahanan geser tanah akan meningkat bila kadar air menurun. Hasil pengukuran menunjukkan bahwa penurunan kadar air 23 % dapat meningkatkan ketahanan geser tanah hingga 689 Kpa. Peningkatan kadar air tanah menyebabkan peningkatan beban terhadap gaya yang diberikan terhadap tanah sehingga terjadi pergerakan. Selain itu, adanya air dalam tanah bersifat sebagai pelicin yang menyebabkan melemahnya ikatan antar partikel tanah. Berdasarkan nilai Lrv dan Drv yang diperoleh jenis tanaman yang berpotensi menstabilkan lereng lahan agroforestri adalah pohon kopi dengan pohon penaung pohon petai dan alpukat. Tanaman tersebut bermanfaat bagi masyarakat dari segi ekonomi maupun ekologi yang sangat dibutuhkan untuk mencapai pertanian berkelanjutan.
English Abstract
Climate change is causing extreme weather and increasing average rainfall in some regions in Indonesia. This has the potential to trigger landslides, and land degradation in steep sloped areas. Landslides are influenced by the restraining force of the lower slope which is the soil shear strenth and root strength. Research purpose to examine the effect of increasing tree root density on increasing soil shear strenght and assessing the effect of soil moisture content on soil shear strenght. Field observation was conducted in April - June 2019 in KHDTK UB Forest, Tumpangrejo Village (Buntoro) and Sumberwangi Village in areas with a slope of 26-28 ° (very steep). Soil analysis is carried out in the Soil Physics & Soil Biology laboratory, Faculty of Agriculture, Universitas Brawijaya. Root measurements performed on 5 species of trees commonly found along the survey path, that are robusta coffee (Coffea Canephora), avocado (Persea americana), dadap (Erythrina variegata), petai (Parkia speciosa), and gamal (Gliricida sepium), measurements of each tree species was repeated 5 times. Sampling of Soil and root sampling for measuring of soil shear strenght is done in 2 zones / slopes, on the slope above the tree trunk and below the tree trunk. Soil sample taken from soil layer depth 0-10 cm using a 10x10 cm ring sample. The observed parameters are soil shear strenght Soil shear strength (Direct Shear Strees Method), Root length per volume (Lrv), Root dry weight per Volume (Drv), Specrol (Specific root length density, Lrv / Drv), and measurement of soil shear strength by treating soil at various conditionsof water content. The results of this study showed the highest Lrv and Drv values in the coffee tree with an Lrv value of 0.272 cm.cmˉ³ and Drv value of 0,00064 g.cmˉ³. The highest soil shear strenght value is found in the soil around the gamal plant (1904 Kpa), but if root density is taken into account in calculating the soil shear strenght, the highest is found around coffee trees (1444 Kpa) and the lowest was found near gamal (57 Kpa) . The tree root density increases the shear strenght, the higher the value of Lrv followed by an increase in soil shear strenght (R² = 0.52). The shear strenght of the soil will increase if the water content decreases. The measurement results show that a 23% decrease in water content can increase the shear strenght of the soil up to 689 Kpa. An increase in groundwater content causes an increase in the load on the force exerted on the ground resulting in movement. In addition, the presence of water in the soil acts as a lubricant that causes weakening of bonds between soil particles. Based on Lrv and Drv values obtained by plant species that have the potential to stabilize the slopes of agroforestry lands are coffee trees with shade trees of petai trees and avocados. The plants are beneficial to the community in terms of economy and ecology that are needed to achieve sustainable agriculture.
Other obstract
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| Item Type: | Thesis (Sarjana) |
|---|---|
| Identification Number: | SKR/FP/2019/871/052000953 |
| Subjects: | 600 Technology (Applied sciences) > 631 Specific techniques; apparatus, equipment materials > 631.4 Soil science > 631.43 Soil physics > 631.433 Soil mechanics |
| Divisions: | Fakultas Pertanian > Ilmu Tanah |
| Depositing User: | Nur Cholis |
| Date Deposited: | 10 Aug 2020 08:16 |
| Last Modified: | 25 Oct 2021 07:26 |
| URI: | http://repository.ub.ac.id/id/eprint/179489 |
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