Finding suitable humidity to produce biofertilizer containing nitrogen-fixing purple nonsulfur bacteria

Abstract

The study aimed to find a suitable humidity for producing biofertilizer containing nitrogen (N)-fixing purple nonsulfur bacteria (N-PNSB). The experiment was a completely randomized design with 2 factors and 3 replications. The first factor was 5 levels of humidity: 30, 40, 50, 60 and 70% and the second factor was the N-PNSB strains: W15, S27, W39 and W15+S27+W39, which were all experimented in a substrate of 1 straw: 3 pineapple leaf: 1 husk ask. The experiment revealed that the C content in the substrate peaked at the humidity of 30, 50, 60 and 70% (roughly 59.3, 59.4, 58.5 and 59.5%, respectively). At the same time, the treatments with the W15 or S27 strain resulted in C/N of 46.4 and 44.9, which were lower than the other treatments. Furthermore, at humidity of 40 - 70%, the the growth of the N-PNSB W15, S27 and S39 was optimal with a bacterial density of 0.424 - 0.428 x 10⁶ CFU/g.