Karakteristik Sifat Fisik Tanah Guna Mengetahui Potensi Reaktivasi Longsor di Ngasinan, Bener, Purworejo

ALDIO KUSWARA, Prof. Dr. rer. Nat. Junun Sartohadi, M. Sc., Ph. D;Nur Ainun H. J Pulungan, M. Sc., Ph. D.

2023 | Skripsi | S1 ILMU TANAH

Kajian karakteristik tanah untuk mengetahui potensi reaktivasi pada lahan bekas longsor belum banyak dilakukan. Kajian karakteristik tanah pada lahan bekas longsor memberikan manfaat terhadap pengelolaan lahan yang tepat di lahan bekas longsor. Penelitian bertujuan untuk (1) mengetahui faktor-faktor sifat fisik tanah pada lahan bekas longsor yang dapat memicu longsor untuk aktif kembali , (2) memberikan rekomendasi pengelolaan lahan yang tepat pada lahan bekas longsor. Pengumpulan data penelitian meliputi kegiatan pra-lapangan, lapangan, dan analisis data. Pengumpulan data diawali dengan pengambilan contoh tanah pada area bekas longsor penelitian. Terdapat 4 area bekas longsor dan masing-masing bekas longsor dibagi menjadi 3 bagian berdasarkan tingkat kelerengan atas, tengah, dan bawah. Contoh tanah diambil pada jeluk 0-40 cm dan 40-80 cm dengan 3 ulangan pada setiap lereng sehingga terdapat 36 titik pengambilan sampel tanah. Contoh tanah terusik digunakan untuk pengukuran berat volume, sedangkan contoh tanah terusik digunakan untuk pengukuran kadar lengas, berat jenis, kadar air maksimum, batas plastis, batas cair, indeks plastisitas, tekstur, dan bahan organik. Data hasil pengukuran yang diperoleh kemudian dibandingkan dengan penelitian sebelumnya yang memiliki karakteristik tanah yang sama dan bentuk pemanfaatan tanah yang serupa. Data hasil penelitian sebelumnya dijadikan acuan sebagai ambang batas longsor reaktivasi untuk mengetahui indikasi reaktivasi pada setiap area bekas longsor. Area bekas longsor penelitian yang memiliki indikasi reaktivasi akan dilakukan evaluasi pengolahan lahan secara deskriptif. Hasil penelitian menunjukkan semua area bekas longsor penelitian mengalami proses reaktivasi yang dibuktikan dengan nilai porositas dan indeks plastisitas pada setiap sampel area bekas longsor penelitian cenderung melebihi nilai ambang batas reaktivasi longsor. Pengolahan lahan yang sesuai di terapkan pada area bekas longsor penelitian untuk memperkecil indikasi reaktivasi longsor adalah sistem agroforestri

Soil characteristic studies to determine the potential for reactivation in the former landslide area has not been widely carried out. Study of the characteristics of the soil in the former landslide area provides benefits for proper land management in the former landslide area. The objectives of this research were (1) determine the factors of the physical properties of the former landslide that can trigger another landslide, (2) provide recommendations for proper land management of the former landslide. Research data collection included pre-field, field and data analysis activities. Data collection begins with taking soil samples in the former landslide research area. There are 4 areas of former landslides and each landslide is divided into 3 sections based on the level of the upper, middle and lower slopes. Soil samples were taken at depths of 0-40 cm and 40-80 cm with 3 replications on each slope so that there were 36 soil sampling points. Disturbed soil samples were used to measure unit weight, while disturbed soil samples were used to measure length, specific gravity, maximum moisture content, plastic limit, liquid limit, plasticity index, texture, and organic matter. The measurement data obtained were then compared with previous studies which had the same soil characteristics and similar forms of land use. Data from previous studies is used as a reference as a reactivation landslide limit house to find out indications of reactivation in each landslide former area. Areas of former landslide research that have indications of reactivation will be carried out with a descriptive evaluation of land management. The results showed that all the research landslide areas underwent a reactivation process as evidenced by the porosity and plasticity index values in each sample of the research landslide areas which tended to exceed the landslide reactivation threshold value. Appropriate land management applied to the former landslide research area to minimize indications of landslide reactivation is an agroforestry system.

Kata Kunci : karakteristik tanah, longsor, potensi reaktivasi, pengolahan lahan.