Seleksi Bakteri Penambat Nitrogen dan Penghasil Hormon IAA (Indole Acetic Acid) dan Uji Potensinya terhadap Pertumbuhan dan Produksi Tanaman Kedelai (Glycine max L.)

Abstract

Rizosphere bacteria which is fix nitrogen and produce IAA (Indol Acetic Acid) is used as an effort to increase both growth and production of soybean plants. The research had been done in the Microbiology laboratory and in the home screen, Department of Biology, Faculty of Mathematics and Natural Sciences, University of North Sumatera from February until September 2012. The aim of this study is to select the most potential nitrogen fixing and IAA producing bacteria then examine their effect on growth of soybean plants which had been grown in soil containing less nutrients. The in vivo test has been done on seven days old of soybean plants. Bacteria were introduced by pouring them on the rhizosphere of plants. The results showed that the highest IAA concentration was produced by I3 isolate which was 33.3 ppm and the highest concentration of nitrogen was produced by N3 isolate which was 29.93 ppm. Combination between N3 and I3 isolates (N3I3) showed the best results in affecting the growth and production of plants, among which the weight of fruit, root volume, plant height, number of fruits, fresh and dry weights of soybean plants. The use of nitrogen fixing and producing IAA bacteria simultaneously can significantly increase the growth of soybean plants (P < 0.05).

Bakteri rizosfer yang menambat nitrogen dan menghasilkan IAA (Indol Acetic Acid) dapat dimanfaatkan sebagai salah satu upaya peningkatan pertumbuhan dan produksi tanaman kedelai. Penelitian ini telah dilakukan di laboratorium Mikrobiologi dan pengujian secara in-vivo di rumah kasa, Departemen Biologi, FMIPA, Universitas Sumatera Utara dari bulan Februari hingga September tahun 2012. Penelitian ini bertujuan untuk menyeleksi bakteri penambat nitrogen dan penghasil IAA paling potensial dan melihat pengaruhnya terhadap pertumbuhan dan produksi tanaman kedelai yang ditanam di tanah kuning yang diduga mengandung sedikit unsur hara. Penambahan bakteri dilakukan pada tanah penanaman kedelai yang berumur 1 minggu dengan cara menyiramkannya pada daerah rizosfer. Hasil penelitian menunjukkan bahwa konsentrasi IAA tertinggi dihasilkan oleh isolat I3 sebanyak 33.3 ppm, sedangkan konsentrasi nitrogen yang tertinggi dihasilkan oleh N3 dengan konsentrasi 29.93 ppm. Perlakuan penambahan gabungan isolat N3 dan I3 (N3I3) menunjukkan pengaruh terbaik terhadap pertumbuhan dan produksi tanaman, seperti berat buah, volume akar, tinggi tanaman, jumlah buah, berat basah dan berat kering tanaman kedelai. Pemakaian bakteri penambat nitrogen dan penghasil IAA secara bersamaan dapat meningkatkan pertumbuhan tanaman dan produksi kedelai secara signifikan (P < 0.05).