Combined effect of microbial and non-microbial biostimulants on wheat growth, yield, and grain nutritional quality under sandy soil conditions.

Abstract

Background: The agricultural use of sandy soils has expanded worldwide to meet the increasing demand for food and other agricultural commodities resulting from rapid population growth and urbanization. However, the inherent limitations of these soils, particularly their low capacity to retain water and nutrients, pose major challenges to sustainable crop production. Accordingly, field experiments were conducted to assess the effectiveness of integrated microbial and non-microbial biostimulants in improving the performance of wheat (Triticum aestivum L. cv. Sakha-94). Wheat grains were co-inoculated with Trichoderma harzianum and Aspergillus niger as phosphate-solubilizing fungi (TD + PSF), and plants were treated with potassium sulfate (K₂SO₄ 200 mg/l), tryptophan (Try 50 mgL-¹), K₂SO₄ (200 mgL-¹) + Try (50 mgL^-1), and two concentrations of banana peel extract (BPE) (500 and 1000 mgL-¹).

Results: Yield performance was substantially improved, with increases of 34.2%, 38.9%, and 44.1% in straw yield, biological yield, and grain yield, respectively. Supporting these yield gains, growth characteristics and physiological attributes were significantly enhanced. The combined application of TD + PSF and BPE1000 produced the highest increases in chlorophyll a (31.4%), chlorophyll b (83.6%), total pigments (48.2%), and phenolic compounds (18.9%). Indole-3-acetic acid (IAA) content increased significantly following co-inoculation, with the greatest enhancement (34.9%) recorded under the K₂SO₄ + tryptophan treatment combined with TD + PSF. Grain nutritional quality was also enhanced. The BPE at 1000 mg L^-1 combined with TD + PSF treatment resulted in the highest carbohydrate content (12.5%), whereas BPE500 combined with TD + PSF achieved the greatest increase in grain protein content (33.2%). The combination of K₂SO₄ + tryptophan and TD + PSF significantly improved mineral accumulation, increasing N, P, K, and Mg contents by 33.2, 41.7, 16.2, and 44.2%, respectively. In addition, the highest water productivity (44.12%) was obtained with BPE1000 combined with TD + PSF. The ratio of essential to non-essential amino acids in the grain yield was enriched by approximately 12-15% in plants treated with the combination of TD + PSF and other treatments. This enrichment indicates an improvement in the nutritional quality of the wheat grains, enhancing their value for human dietary needs.

Conclusion: Among the tested treatments, the combined application of (TD + PSF) and banana peel extract (1000 mg L⁻¹) produced the greatest improvements in wheat growth, yield, and grain quality. These findings demonstrate that banana peel extract, particularly when combined with beneficial fungi, is a promising, low-cost, and eco-friendly biostimulant for wheat cultivation in reclaimed sandy soils, while promoting the sustainable utilization of agricultural waste.