Electronic Theses and Dissertation

Produksi kopi arabika pada tahun 2017 sebanyak 28.358 ton dengan luas areal 46.273 ha, kemudian pada tahun 2018 meningkat menjadi 30.408 ton dengan luas areal 46.273 ha dan pada tahun 2019 produksi kopi arabika mengalami penurunan kembali yaitu mencapai 29.101 ton dengan luas areal 46.273 ha (distanhub, 2021). faktor penyebab turunnya produksi kopi arabika salah satunya yaitu kurangnya unsur hara nitrogen. azotobacter sp. merupakan salah satu bakteri aerob penambat nitrogen non simbiotik dengan kemampuan memfiksasi nitrogen dalam jumlah yang relatif tinggi, berkisar antara energi, keberadaan nitrogen, mineral, reaktivitas tanah dan faktor lingkungan lainnya serta keberadaan bakteri tertentu (rahmi, 2014). penelitian ini bertujuan untuk mengeksplorasi bakteri azotobacter sp. yang berasal dari kebun kopi arabika kabupaten bener meriah dan menguji bakteri azotobacter sp. yang mampu mengikat nitrogen dari udara. penelitian ini menggunakan metode survei lapangan dan deskriptif. pengambilan sampel tanah dilakukan dikawasan perkebunan kopi arabika di 20 desa yang ada di kecamatan pintu rime gayo, gajah putih, bandar, bener kelipah dan mesidah dengan ketinggian 860 – 1550 m dpl. pengambilan sampel tanah dilakukan pada rhizosfer tanaman kopi yang berumur produktif 20-35 tahun dengan kedalaman 0-20 cm. setiap kebun kopi diambil satu sampel tanah satu kilogram dan setiap sampel tanah merupakan komposit dari empat titik pemboran tanah di rhizosfer tanaman kopi. sampel tanah dimasukan kedalam kantong plastik dan disimpan pada suhu 4 oc. isolasi dilakukan terhadap sampel tanah dari rhizosfer tanaman kopi arabika dari kabupaten bener meriah, kemudian dilanjutkan dengan pemurnian, seleksi pada medium ashby cair dan uji aktivitas pada media tanah terhadap bakteri azotobacter sp. yang terseleksi. data yang diperoleh dianalisis secara deskriptif. hasil penelitian ini ditemukan isolat bakteri azotobacter sp. dari sampel tanah rhizosfer kebun kopi arabika kabupaten bener meriah diperoleh sebanyak 40 isolat. 40 isolat tersebut berasal dari 20 desa yang ada di kabupaten bener meriah, dimana setiap desa diambil tingkatan pengenceran 10-3 dan 10-4. jumlah isolat yang ditemukan berbeda dari setiap tingkatan pengenceran. bakteri yang berhasil diisolasi diberi kode a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, a31, a32, a33, a34, a35, a36, a37, a38, a39 dan a40. sampel tanah yang diinokulasikan isolat bakteri azotobacter sp. dengan kode a15 dan a35 memiliki rata-rata n-total tanah sama dengan kontrol dengan kriteria sedang yaitu 0,21 % dan 0,22 % dari sampel tanah yang diinokulasikan isolat azotobacter sp. yang lain. sampel tanah yang diinokulasikan isolat bakteri azotobacter sp. dengan kode a3, a4, a5, a16, a24 dan a36 memiliki rata-rata n-total tanah dengan kriteria rendah dari kontrol yaitu 0,20 %, 0,18 %, 0,17 %, 0,20 %, dan 0,17 %. isolat bakteri azotobacter sp. dari sampel tanah rhizosfer kebun kopi arabika kabupaten bener meriah tidak mampu mengikat nitrogen dari udara.

Arabica coffee production in 2017 was 28,358 tons with an area of 46,273 ha, then in 2018 it increased to 30,408 tons with an area of 46,273 ha and in 2019 Arabica coffee production decreased again, reaching 29,101 tons with an area of 46,273 ha (Distanhub, 2021). One of the factors causing the decline in Arabica coffee production is the lack of nitrogen nutrients. Azotobacter sp. is one of the non-symbiotic nitrogen-fixing aerobic bacteria with the ability to fix nitrogen in relatively high amounts, ranging from energy, the presence of nitrogen, minerals, soil reactivity and other environmental factors and the presence of certain bacteria (Rahmi, 2014). This study aims to explore Azotobacter sp. bacteria from Arabica coffee plantations in Bener Meriah Regency and test Azotobacter sp. bacteria that are able to fix nitrogen from the air. This research used field survey and descriptive methods. Soil sampling was conducted in Arabica coffee plantations in 20 villages in Pintu Rime Gayo, Gajah Putih, Bandar, Bener Kelipah and Mesidah sub-districts with an altitude of 860 - 1550 m above sea level. Soil sampling was conducted in the rhizosphere of 20-35 years old productive coffee plants with a depth of 0-20 cm. One kilogram of soil was taken from each coffee plantation and each soil sample was a composite of four soil boring points in the rhizosphere of coffee plants. Soil samples were put into plastic bags and stored at 4 oC. Isolation was carried out on soil samples from the rhizosphere of Arabica coffee plants from Bener Meriah Regency, then continued with purification, selection on liquid Ashby medium and activity tests on soil media against selected Azotobacter sp. bacteria. The data obtained were analyzed descriptively. The results of this study found isolates of Azotobacter sp. bacteria from rhizosphere soil samples of Arabica coffee plantations in Bener Meriah district obtained as many as 40 isolates. The 40 isolates came from 20 villages in Bener Meriah Regency, where each village was taken at dilution levels 10-3 and 10-4. The number of isolates found is different from each level of dilution. Bacteria that were successfully isolated were coded A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39 and A40. Soil samples inoculated with Azotobacter sp. bacterial isolates with code A15 and A35 have the same average soil N-total as the control with moderate criteria, namely 0.21% and 0.22% of soil samples inoculated with other Azotobacter sp. isolates. Soil samples inoculated with isolates of Azotobacter sp. with the code A3, A4, A5, A16, A24 and A36 have an average soil N-total with low criteria from the control, namely 0.20%, 0.18%, 0.17%, 0.20%, and 0.17%. Isolates of Azotobacter sp. bacteria from rhizosphere soil samples of Arabica coffee plantations in Bener Meriah Regency are not able to fix nitrogen from the air.