Trial settings and soil properties

The experiment was conducted during the maize vegetative period in 2018−2020 under dry farming conditions in Zemun Polje, Serbia (44° 52′ N, 20° 20′ E). The soil was slightly calcareous chernozem, containing 53.0% sand, 30.0% silt, and 17.0% clay. The preceding crop was always winter wheat (Triticum vulgare L.). Each year, at the beginning of April, the soil was sampled, and the chemical composition, including the pH, soil organic matter content (SOM), and contents of the available elements, were determined ( Table 1 ). The variations in the contents of the mineral elements were slight and could be owing to the soil conditions of the experimental area, the previous crop, and/or the meteorological conditions and variability in the growing conditions.

The soil composition, including soil organic matter (SOM) content and available forms of mineral elements.

The experimental trial included maize hybrids with different kernel colors: red (ZP 5048c), white (ZP 522b), and intense yellow (ZP 737). The sowing was performed in the spring (last week of April) in all 3 years. Together with seed-bed preparation (2–3 days before sowing), the fertilizer treatments were applied and incorporated into the soil according to the manufacturer’s recommendations: biofertilizer (BF; Team Micorriza Plus), 3 kg ha⁻¹ (0.5 kg 100 L⁻¹ water); organic fertilizer (OF; Fertor), 2.5 t ha⁻¹; mineral fertilizer (urea; 46% N), 200 kg ha⁻¹; and control (Con; no fertilization). Team Micorriza Plus is an inoculum in powder form that contains the arbuscular mycorrhizal fungi Rhizophagus intraradices (150 spores g⁻¹) and Glomus mosseae (150 spores g⁻¹) and rhizosphere bacteria (1 × 10⁷ UFC g⁻¹) with 56% organic matter content. It improves plant nutrient absorption, increases the crop’s tolerance to abiotic and biotic stresses, and maintains soil fertility. Fertor is a fertilizer in pellet form, produced from chicken manure and plant-based organic matter. It contains NPK (4.5:2.7:2.3) + 1.1% Mg + 9.3% Ca and other macro- and micronutrients, which are partly soluble and available to plants, whereas insoluble parts enable the continual release of nutrients during vegetation. Standard cropping practices were applied, according to the manufacturer’s requirements. Both fertilizers, Team Micorriza Plus and Fertor, are permitted for use in organic agriculture. After harvest (during the second half of October), the maize grain yield was measured and calculated at 14% moisture, and the grains were used for further analyses.