The biological impact of Azospirillum spp. isolated from the Samawa desert on several growth indices of wheat crops

Biostimulants are one of the important components of the sustainability of agriculture production. Additionally, they replace chemical fertilizers and mitigate environmental pollution and soil contamination. Azospirillum is a free-living bacterial, which can be used as a fertilizer and promote growth.  This study is designed to evaluate the biological impact of isolated Azospirillum spp. from the Samawa desert on several growth indices of wheat crops. Four strains of nitrogen-fixing bacterium were isolated from the Samawa desert. The bacterial isolates were identified according to colonies' morphology, microscopical features, and biochemical characteristics as Azospirillum spp. Three isolates were classified as A. lipoferum according to their superior nitrogen fixing efficiency. Then, three isolates were designated A1, A2, and A3 and utilized to inoculate wheat groups. The inoculants served to fulfill a portion of the nitrogen requirements of the wheat crop via the execution of a field experiment. Cultivation occurred in pots, with three replications as follows: A0 without inoculant, A1, A2, and A3 with three different isolates. Meanwhile, nitrogen fertilization was N1, N2, and N3 for 0, 0.25, and 0.5 % of the fertilizer guideline. Significant effects were seen on the plant height for the Azospirillum spp group compared to the control group. The plant height, dry weight of shoots, leave area, and Chlorophyll content (SPAD) revealed variations between the treated and control groups.  The results also showed that isolate A3 revealed better efficacy in enhancing plant height compared to other isolates. The increase was 92.53 cm in plant dry weight with a 9.60 grams total increase. Further, isolate A3 demonstrated superiority over the other strains in augmenting leaf area with a 47.47 cm² total increase and 38.34 spad chlorophyll content increment. In conclusion, this study approved the growth improvement of wheat plants with bacterium inoculum. The authors recommend future studies to investigate more features of Azospirillum spp, such as biostimulants.