Effects of Azospirillum lipoferum enriched-vermicompost application on growth and yield of corn (Zea mays L.) and on soil microbial community

Fresh vermicompost was prepared from plant residues and cow dung using Eisenia foetida. The total NPK of the prepared vermicompost was enhanced by inoculation with Azospirillum lipoferum BSS-8 from 4.42% to 5.05%; where, the total N was 2.05 %, total P was 1.5%, and total K was 1.5%. Increase in the population of the culturable bacteria and fungi in the enriched vermicompost were observed through incubation time. The application of the enriched vermicompost in corn production showed that growth parameters such as plant height, shoot diameter, plant and root biomass have no significant differences among the treatments amended with either vermicompost or inorganic fertilizer or a combination of both. Significant increase in corn yield was observed in treatments amended with full rate of recommended rate of chemical fertilizer (RRC), full rate RRC plus vermicompost, and half rate RRC plus vermicompost compared to the unamended control. However, no significant difference was observed on the yield of corn among all amended treatments. The short-term application of the enriched vemicompost had no effects on the soil properties and on the population of culturable bacteria, actinomycetes and fungi. The culture-independent approach used in the study was able to identify the soil prokaryotic community of the amended soils as well as the applied enriched vermicompost. A total of 18,779 sequence reads were classified using high-throughput sequencing wherein 18,751 reads (99.9 %) constituted to the bacterial population of which 33 phyla were identified while 0.1 % was classified under archaea. Among all the phyla, Proteobacteria were the most abundant constituting about 36.88% of the total bacterial reads followed by Acidobacteria (21.2%), Bacteroidetes (8.77%), Verrucomicrobia (8.15%), Chloroflexi (6.05%), Actinobacteria (4.88), Planctomycetes (3.01%), Firmicutes (1.89%), and Patescibacteria (1.16%). The different fertilization strategies used in the study were able to affect the distribution of these phyla and its representatives among the samples in terms of relative abundances. The application of vermicompost was able to increase members of copiotrophic bacteria such as Proteobacteria, Bacteroidetes, Planctomycetes, Chloroflexi, Actinobacteria, and Firmicutes which prefers nutrient-rich environments. A total of 20 phyla were common among the five rhizosphere soil samples making them the core prokaryotic biome in the experimental site. Crenarchaeota, Fibrobacteres, and Thaumarchaeota were found only in the vermicompost-amended plots while Omnitrophicaeota and Euryarchaeota were found only in the inorganically fertilized soils. The Canonical Correspondence Analysis (CCA) and predictive metabolic profiling revealed that samples treated with the enriched vermicompost were inclined to cluster and have similar metabolic profiles as compared to full rate of chemical fertilizer alone and the enriched vermicompost.