Solid Fermentation Products of Trichoderma viride Improve Soil Aggregation, Soil Nutrient Status and Plant Growth

Soil degradation caused by intensive agricultural management has become a major constraint on sustainable crop production, highlighting the need for multifunctional soil amendments capable of simultaneously improving soil structural quality and crop performance. In this greenhouse pot experiment, the effects of Trichoderma viride-fermented xylose residue on soil physical and chemical properties, aggregate stability, soil nutrient status, root development, photosynthetic characteristics, and cucumber (Cucumis sativus L.) growth were evaluated. The fermented amendment was incorporated into soil at application rates of 0 (CK), 0.5 (T1), 0.75 (T2), 1.0 (T3), 1.25 (T4), and 1.5% (T5) (w/w). Amendment application significantly affected soil structural characteristics and plant growth responses. Compared with the control, T3 and T4 increased the proportion of macroaggregates by 3.12% and 6.09%, respectively, whereas mean weight diameter increased by 26.81–29.76% under T3–T5. The T2 treatment produced the highest soil porosity, aeration porosity, capillary porosity, chlorophyll content, and net photosynthetic rate. Soil total nitrogen, total phosphorus, total carbon, and total organic carbon concentrations also differed significantly among treatments, while plant nitrogen and phosphorus contents were markedly enhanced under T2 and T3. Aboveground biomass increased by up to 59.80% relative to the control. Mantel analysis revealed significant associations among soil physical and chemical properties, aggregate characteristics, root morphology, plant nutrient contents, and biomass accumulation. Collectively, these findings demonstrate that T. viride-fermented corncob xylose residue can improve soil structural properties and promote cucumber growth under greenhouse pot conditions. Among the application rates evaluated, 0.75% provided the most balanced overall response across soil physical properties and plant performance. The present study provides a basis for the utilization of fermented lignocellulosic residues as integrated bio-organic amendments for sustainable soil management.