Composted Sludge and Trichoderma harzianum T-22 as a Dual Strategy to Enhance Wheat Growth and Soil Microbial Diversity

This study evaluated the effects of Trichoderma harzianum strain T-22 on wheat (Triticum turgidum L. var. Durum, cv. Vitron) growth and soil microbial dynamics. Three inoculation levels (I0, I1, and I2) were applied to different soil substrates: Villacañas soil (V), Quero soil (Q), and composted sewage sludge (C) from Alcázar de San Juan. Over six months, soil physicochemical properties, fungal diversity, and plant development were analyzed. The results showed that Trichoderma significantly increased fungal diversity, particularly in compost-amended substrates. In treatments with composted sludge and Trichoderma (CVI2 and CQI2), Trichoderma colonization reached up to 112,000 propagules/g, enhancing microbial activity. Higher shoot biomass and spike weight were observed when combining compost with Trichoderma since it improved nutrient availability and plant growth. Additionally, Trichoderma inoculation reduced the presence of pathogenic fungi such as Helminthosporium and Fusarium, reinforcing its biocontrol potential. However, high salinity of the soil limited microbial proliferation and plant performance. In conclusion, composted sludge and Trichoderma improved soil microbiota, enhanced wheat growth, and increased resistance against pathogens. The results highlight the potential of Trichoderma as a sustainable alternative to chemical treatments in crop production. Further studies should further investigate field-scale applications to validate these findings under real agricultural conditions.