AGROEKOSISTEM KOPI BERKELANJUTAN YANG MEMPERTAHANKAN KERAGAMAN BAKTERI TANAH

RUSDI EVIZAL, MS, Prof. Dr. Ir. Tohari, M.Sc.

2011 | Disertasi | S3 Bioteknologi

Pohon pelindung pada agroekosistem kopi menyediakan manfaat ekologi antara lain berupa konservasi tanah dan keragaman hayati, daur ulang unsur hara melalui guguran seresah, dan penambatan N udara oleh bintil akar pohon pelindung legum. Bakteri sebagai bagian dari keragaman hayati bawah tanah berperan penting dalam berfungsinya layanan ekosistem tersebut. Penelitian in bertujuan untuk mendapatkan model agroekosistem kopi yang mempertahankan keragaman bakteri tanah sebagai indikasi keberlanjutan usahatani kopi. Pada penelitian ini dilaksanakan survei dan percobaan petak agroekosistem kopi di benchmark Conservation and Sustainable Management of Below-Ground Biodiversity (CSM-BGBD) di Kecamatan Sumberjaya, Lampung Barat pada periode 2007-2010. Jenis agroekosistem yang dievaluasi adalah agroekosistem kopi robusta (Coffea canephora) berpohon pelindung gamal (Gliricidae sepium), dadap (Erythrina sububrams), cempaka (Michelia champaca), dan tanpa pohon pelindung sebagai kontrol. Petak percobaan terdiri dari petak agroekosistem kopi muda berumur 4-5 tahun dan petak quassy experiment agroekosistem kopi dewasa berumur 15-16 tahun. Keragaman bakteri tanah dianalisis berdasarkan uji fisiologi (kemampuan memetabolisme sumber C) dan uji molekular terhadap total bakteri tanah dan bakteri pembentuk bintil akar. Indeks keberlanjutan dianalisis berdasarkan variabel ekologi dan kelayakan usahatani. Kesimpulan umum penelitian ini adalah bahwa agroekosistem kopi berpohon pelindung legum memiliki indeks keberlanjutan yang tinggi dan mampu mempertahankan keragaman bakteri tanah.Kesimpulan tersebut diambil berdasarkan kesimpulan: (1) Perubahan lahan hutan menjadi lahan pertanian menurunkan keragaman bakteri tanah. Agroekosistem kopi mampu mempertahankan keragaman bakteri tanah; (2) Agroekosistem kopi berpohon pelindung memiliki indeks similaritas keragaman bakteri tanah terhadap hutan yang lebih besar daripada agroekosistem kopi tanpa pohon pelindung. Agroekosistem kopi berpohon pelindung lebih mampu mempertahankan keragaman bakteri tanah daripada agroekosistem kopi tanpa pohon pelindung. Agroekosistem kopi berpohon pelindung legum memiliki keragaman bakteri tanah yang tidak berbeda dengan agroekosistem kopi berpohon pelindung nonlegum; (3) Agroekosistem kopi berpohon pelindung legum lebih mampu mempertahankan keragaman bakteri pembentuk bintil akar daripada agroekosistem tanpa pohon pelindung dan agroekosistem kopi berpelindung nonlegum; (4) Pohon pelindung memberi layanan lingkungan antara lain menambat N oleh bintil akar pohon legum, memproduksi seresah, memberinaungan, menurunkan suhu udara di tajuk kopi dan suhu tanah, dan menekan pertumbuhan gulma. Pohon pelindung jenis dadap menyumbang N yang tertinggi dari seresah guguran dan pangkasannya,diikuti oleh pohon pelindung jenis cempaka dan gamal; (5) Agroekosistem kopi berpohon pelindung legum lebih dapat mempertahankan produktivitas kopi daripada agroekosistem kopi tanpa pohon pelindung dan agroekosistem kopi berpohon pelindung nonlegum; (6) Pada agroekosistem kopi berumur 15 tahun, Indeks keberlanjutan agroekosistem kopi berpelindung legum lebih tinggi daripada agroekosistem kopi tanpa pohon pelindung dan berpelindung nonlegum.

Shade trees in coffee agro-ecosystems provide ecological benefits such as soil conservation, biodiversity, nutrient cycling through litter fall, and N fixation by nodules of legume shade trees. Soil bacteria as part of belowground biodiversity plays an important role on ecosystem functioning. The aim of this research was to examine coffee agro-ecosystems with high sustainability index that sustain soil bacteria diversity. The research was conducted through survei and experimental petak of coffee agro-ecosystems, at benchmark site of Conservation and Sustainable Management of Below-Ground Biodiversity (CSM-BGBD), in Sumberjaya Subdistrict, West Lampung, Indonesia, during 2007-2010. Types of coffee agroecosystems to be examined were Coffea canephora with shade trees of Gliricidae sepium, Erythrina sububrams, Michelia champaca, and sun coffee (without shade tree). Two plots were 4-5 years old coffee plot and a quassy experiment plot of 15-16 years old coffee. Diversity of soil bacteria was evaluated based on C source and DNA finger printing of total soil bacteria and legume nodulating bacteria. Sustainability of coffee agroecosystems was assessed based on ecological variables and economic reliability. The main conclusion of the research was that legume shaded coffee agroecosystems had high sustainability indeces and able to sustain soil bacteria diversity. The detail conclusions were: (1) Landuse change from forest to agroecosystems decrease diversity of soil bacteria. Coffee agro-ecosystems were able to sustain soil bacteriadiversity; (2) shaded coffee agro-ecosystems were able to sustain soil bacteriadiversity better than sun coffee agro-ecosystem; (3) legume shaded coffee agro-ecosystems were able to sustain legume nodulating bacteria diversity better than sun coffee agro-ecosystem and nonlegume shaded coffee agro-ecosystem; (4) shade trees provide ecosystems service such as N fixation by legume nodule,producing litter fall, giving shading, reducing air and soil temperature, reducing weed growth, and influencing coffee leaf fall off dynamic. Litter fall of shade trees had significance in equalizing N export of coffee bean harvest. Seasonal shading dynamic and litter fall dynamic influences coffee productivity; (5) legume shaded coffee agro-ecosystems were able to sustain coffee productivity better than sun coffee agro-ecosystem and nonlegume shaded coffee agro-ecosystem; (6) for 15 years old coffee, legume shaded coffee agroecosystems had higher sustanability index than sun coffee agro-ecosystem and nonlegume shaded coffee agroecosystem.

Kata Kunci : Agroekosistem kopi, pohon pelindung legum, keragaman bakteri tanah, keberlanjutan