Evaluation of the effect of Azospirillum-like bacteria on the growth and yield of green onion (Allium cepa L.)

Results of the nursery experiment showed that green onion could be successfully raised in pots with minimum expense through inoculation with B10-N alone or in combination with 60-30-30. Plants inoculated with B10-N alone improved the fresh weight of the test plants with 134.40% over the control while the plants that were inoculated with B10-N + 60-30-30 gave 149.71% increase. Post soil analysis suggests that P- content decreased from 7 ppm to 1 ppm in the unfertilized but inoculated pots while the P in the fertilized pots increased. The most number of tillers of green onion grown in Maligaya clay under nursery conditions were produced by the fully fertilized plants and those that were treated solely with B10-N, with 10.50 and 10.25, respectively compared with only 5.5 tillers from the control. Fresh weight of the test plants at harvest was heaviest in the 60-30-30- + B10-N treatment (71.37 g/plant) but shoot dry weight was heaviest in plants grown with B10-N inoculation alone (23.65 g/plant). The N-content of shoots was highest in the fertilized + B10-N plants, while the N-uptake of 517.84 mg/plant was highest in the 60-30-30 + B10-N with 5-fold % increase over the unfertilized, uninoculated control plants. Tiller production in field experiment using Lipa clay loam did not differ among treatments and this ranged from 5.50-7.5 tillers/plant. Yield at harvest was highest in the B10-N inoculated plants in the presence or absence of inorganic input. The mean shoot biomass obtained from all treated plants were significantly higher than that of the control but the shoot N-uptake was highest in the 60-30-30 + B10-N treated plants. As in the pot experiment, a decrease in the P content of green onions after harvest was observed in both field experiments. At the CLSU [Central Luzon State University] site, the maximum decrease of 10.5 ppm was noted from plots that were treated with B10-N alone followed by 7.50 ppm decrease in the 60-30-30 + B10-N treated plots. At the BIOTECH [National Inst. of Biotechnology and Microbiology, College, Laguna, Philippines] demo farm, a 10.3 ppm decrease was noted from the plots that were treated with B10-N alone followed by a 3 ppm decrease in plots that received 60-30-30 + B10-N treatment. A doubling of soil N-content in the unfertilized soil but inoculated with B10-N at the BIOTECH demo farm was also noted. The increase in P-content and concommitant increase in N of soils in inoculated plots must have been a contribution of biological nitrogen fixation that occurred in the system and/or partially by the application of fertilizer. The results suggest that green onion can be grown with reasonable yield if inoculated with B10-N alone or in combination with modest amount of inorganic fertilizer