Penggunaan Rhizobium dan bakteri pelarut fosfat pada tanah mineral masam untuk memperbaiki pertumbuhan bibit sengon (Paraserianthes falcataria (L.) Nielsen)

Abstract

The main problem of acid soil is the availability of nutrients and high exchangeable A1 content. Soil acidity will reduce many legum plant growth, decrease number of rhizobia and nodule initiation and inhibit the function and growth of ndule. Based on these problems, the experiment was cmducted to obtain the acid and A1 tolerant strain of Rhizobium isolated from sengon nodules, and to obtain the effective strain of Rhizobium in fixing atmospheric nitrogen, and phosphate solubilizing bacteria in increasing P availability, thus support plant growth. The study was focused on three aspects: ( I ) Research on Rhizobim consist of (a) collection of Ahitobiurn strains from sengon nodules, (b) screening Rhizobium toward acidity and high concentration of Al, (c) screening Rhizobium based on their ability to fix nitrogen, (d) marking the selected Rhizobim with antibiotic, and screening the resistant mutants, (e) assesing the effectiveness of the selected Rhizobim on acid soil in greenhouse; (2) Research on phosphate solubilizing bacteria, consist of (a) isolation of phosphate solubilizing bacteria, (b) selection of phosphate solubilizing bacteria in dissolving P from rock phosphate and Alms in liquid medium and acid soil, (c) identification of selected phosphate solubilizing bacteria, (d) determination of organic acid produced by selective phosphate solubilizing bacteria, (e) assessing the effectiveness of selected phosphate solubilizing bacteria in greenhouse; (3) winmulation between Rhizobim and phosphate solubilizing bactetia in greenhouse and field experiments.

Permasalahan yang utama dari tanah masam adalah cadangan unsur hara kesuburan tanah yang rendah, kandungan Al dapat ditukar tinggi, dan mempunyai kapasitas retensi P yang tinggi. Kemasaman tanah pada tanaman leguminosa akan menyebabkan terganggunya pertumbuhan tanaman, jumlah rhizobia dan pembentukan bintil akar berkurang serta terhambatnya fungsi dan perkembangan bintil.