Effects of inoculation on growth promotion and biological nitrogen fixation in maize (Zea mays L.) under greenhouse and field conditions

The application of PGPB to agriculture is increasing as it offers an alternative to the use of chemical fertilizers, pesticides and other supplements. Maize (Zea mays L.) is one of the world’s principal cereal crops, grown for grain, silage and biofuel. Nitrogen fertilizer constitutes one of the major costs in maize production, and PGPB poses a potential alternative for achieving more sustainable production. In this study, we present the results of maize inoculation experiments with PGPB under greenhouse and field conditions. We found significant differences in shoot and root dry weight among cultivars and inoculation treatments in the greenhouse. The inoculation of Maizon with Rhanella spp. EMA83 increased shoot dry weight (22%) relative to the non-inoculated control. Similarly, the maize cultivar PAU871 increased in shoot biomass when inoculated with Pantoea agglomerans EMA82 (33%) and Rhanella spp EMA83 (50%) relative to the non-inoculated treatment. There was a negative correlation between %N a.e. and shoot dry weight (r=0.6, P<0.05, n=75). In the field, maize grain yield (kg ha) increased among treatments with Rhanella spp. onto seed (15%) and soil (12%) and Azospirillum spp.in seed (15%) at 0 N fertilization rates. At maximum fertilization rates an increase was found only for maize inoculated with Rhanella spp. in soil (16%) relative to the non-inoculated control. Relative increases in 1000-grain dry weigth (g) and yield (kg ha) were also observed with inoculation treatments, regardless of N fertilization rate, respectively. In conclusion, Rhanella spp. EMA83 is a promising PGPB for growth enhancement of maize. This strain may potentially fix nitrogen, produce IAA and solubilize P. However, it is equally important to study the mechanisms by which this putative endophyte promotes growth as well as its potential for enhancing sustainable crop production.