Sustainable Microbial Strategies for Enhancing Soil Fertility and Wheat (Triticum aestivum L.) Production

This study aims to assess the relation between both soil and plants outputs by combining Azotobacter chroococcum with blue-green algae Cyanobacterium aponinum and Chroococcidiopsis cubana across different new wheat varieties. Additionally, investigate the prediction changes of soil fertility dynamics and grain yield responses in the upcoming season which has not been investigated. Two-seasons field experiment (2022–2023) was conducted in the Middle Delta region of Egypt using a split-plot design. The main plots comprising wheat varieties (miser3, side14, and Sakha95) and sub-plots included different nitrogen sources (recommended dose 179 kg N ha⁻¹) including bio-fertilizers of Azotobacter chroococcum and blue-green algae with/without nitrogen fertilizer (50%, 75%, and 100%) applied in clayey Vertisols. The interaction between Azotobacter chroococcum and blue-green algae, combined with 50% N (T8), significantly impacted soil microbial biomass carbon (SMB), organic matter, NPK, and fertility index (FI) in both seasons. This treatment affected dehydrogenase activity and ameliorated grain and straw yields significantly, particularly with miser3 recording 9.65 and 3.55 t ha⁻¹ respectively. T8 treatment increased mean FI, and grain weight through Multi-Variate Analysis with Sakha 95 had the lowest records while Principal Component Analysis showed correlations between grain yield and soil chemical properties (SMB < FI < available N < available K). The highest peak of grain yield obtained from 3D-surface contour plot, reaching 10 t ha⁻¹, is achieved with the SMB exceeding 800 mg kg⁻¹, available K 400 mg kg⁻¹, FI exceeding 11, and urease activity 60 µg NH₄ g⁻¹. Trend analysis predicted future increases in FI to 10.917 and grain yield to 10.617 t ha⁻¹. Integrating of bio-fertilizers such as Azotobacter sp. and blue-green algae with reduced chemical nitrogen (50%) not only improves essential soil parameters (pH, SMB, OM, NPK and FI) and enzyme activities, but also results in higher wheat grain (93.82%) and straw yields (50.58%) compared to control, particularly for the miser 3 variety. The forecasting results predicted an increase of both soil fertility by 11.74% and grain yield by 14.66%. The findings suggest a sustainable and effective strategy for overcoming challenges in wheat production by reducing reliance on chemical fertilizers while boosting crop yield and quality.