The Biological Correction Using Humic Substances, Vermicompost, and Azospirillum as an Optimum Way of Optimizing Plant Production and Enhancing Soil Micronutrients in Arid Regions

This field experiment aimed to investigate the effect of using foliar treatments and applying different fertilizers on wheat (TriticumaestivumL.) growth, productivity, and soil fertility under arid conditions.

Agriculture is a critical socio-economic sector in Egypt, generating approximately 10 to 15% of the national gross domestic product. Abiotic stresses arising from climate change negate crop growth and yield, leading to food insecurity.

Six treatments were carried out in the order: CK (control without amendment); NPK (mineral fertilizer: mineral fertilizers, 38 g/m² of urea (46% of N), 10 g/m² of calcium phosphate (45% of P₂O₅), 12 g/m² of potassium sulfate (50% of K₂O)); Azospirillum brasilense (Az), bacteria were soaked with the seeds for 4 hours before sowing and introduced three-time into the soil with irrigation water at 0.7 ml/m²; vermicompost (VC) applied to the soil (2.5 kg/m²); humic substances (0.5 ml/m²) for foliar inoculation (HS); HS + micronutrients (HS-M) soil application (1 ml/m²) with irrigation water. All treatments were applied as soil additives and foliar spray to wheat plants at 31±1 °C for the first two months from seed sowing in calcareous soil. Analysis of variance (ANOVA) of experimental data showed the significance of positive effects of all treatments on soil fertility and plant growth compared to the control and NPK treatments.

The HS and VC treatments had positive effects on the development of plant nutrition, wheat growth, soil pH, and plant availability of micronutrients, which was also reflected in the wheat grain yield and water use efficiency. It was also evident that treating the plants and soil with HS-M increased wheat yield from 3.45 to 8.97 t ha^-1 (260%) compared to the control. On the other hand, VC and Az treatments increased the grain yield by 278% and 267%, respectively, compared to control and NPK treatments. The water use efficiency (kg grain / m³) values increased by 279, 268, 262, 258, and 139% for HS-M, HS, VC, Az, and NPK treatments, respectively, compared to CK. The plants' total N, P, and K content were higher with all organic and biological treatments than NPK and control.

This study has shown that the HS, Az, VC, and HS-M soil additives and foliar applications significantly (p ≤ 0.05) increased the status of Fe, Zn, Mn, Cu, and B in soil, plant growth rate, grain yield, 1000 grain weight, water use efficiency, and soil macro-nutrient of wheat plants growing on calcareous soil.