Effect of Bacillus subtilis and Aspergillus niger inoculation on soil physicochemical parameters in agricultural soils from Béni Mellal (Morocco)

¹ Health, Environment, and Biotechnology Laboratory, Ain Chock Faculty of Sciences (FSAC), Hassan II University, Casablanca 20100, Morocco
² Laboratory of Chemistry-Physics and Biotechnology of Biomolecules and Materials (LCP2BM), Faculty of Science and Technology of Mohammedia (FSTM), Hassan II University, Mohammedia 28806, Morocco
³ Agricultural and Agri-Food Analysis Laboratory (Lab2A), Rabat 10100, Morocco
⁴ A Biotechnology Analyzes, Agrifood and Environment Testing Laboratory, Mohammedia 28830, Morocco

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Soil quality plays a key role in sustainable agricultural productivity, particularly in semi-arid regions where fertility constraints limit crop performance. Microbial biofertilizers represent environmentally friendly alternatives to chemical fertilizers by enhancing nutrient availability and soil health. This study evaluated the effects of Bacillus subtilis and Aspergillus niger inoculations on the physicochemical properties of agricultural soils from the Béni Mellal region of Morocco. A total of 84 soil samples were analyzed, divided into four groups: untreated control, inoculated with B. subtilis, inoculated with A. niger, and combined inoculated. The results showed distinct treatment-dependent responses. B. subtilis significantly enhanced total nitrogen (N), while A. niger increased available phosphorus (P₂O₅) and influenced soil pH. Combined inoculation produced the most pronounced improvements, particularly for total nitrogen, available phosphorus, ammonium, and boron. Manganese (Mn) exhibited moderate but consistent variation among treatments, while organic matter (OM), carbon dioxide (CO₂), iron (Fe), copper (Cu), and zinc (Zn) showed no significant short-term changes. Correlation analysis indicated strong positive associations among key nutrients, suggesting synergistic effects of microbial inoculation. Overall, the findings highlight the potential of Bacillus subtilis and Aspergillus niger, especially when combined, to selectively improve soil fertility and support more sustainable agricultural practices in the Beni Mellal region.