Exploration of indigenous free nitrogen-fixing bacteria from rhizosphere of Vigna radiata for agricultural land treatment

摘要

Nitrogen is the most abundant element in the atmosphere, however, most often deficient in agricultural lands. This research was an exploratory to get indigenous non-symbiotic nitrogen-fixing bacteria. Soil samples were collectedfrom rhizosphere of green beans. This study was aimed to determine the bacterial population of the three regions; screening, isolation and selection of free nitrogen-fixing bacteria. Antagonism and pathogenicity tests were performed to observe its potential for a biofertilizer product. The highest number of free nitrogen-fixing bacteria was found from forest soil sample of 2.5x 10~(11)CFU/ml. Screening and isolation process has obtained 10 free nitrogen-fixing isolates. Then was selected into 4 isolates namely SNF4, SNF5, SNF7 and SNF8 according to the ammonia production test qualitatively. When an antagonism activity performed, there was no inhibition zone each other. The pathogenicity test did not show the pathogenic symptom. This study also showed that bacterial isolates obtained significantly affected the germination growth of green beans compared to controls. Possibility, bacteria of this type produced growth hormone for a plant. Strain SNF8 has shown the highest ammonium production then was selected for 16S rRNA identification. Similarity test of genome sequence of strain SNF8 had 99% similarity with Bacillus cereus.