free-living rhizosphere fungus Trichoderma hamatum GD12 enhances clover productivity in clover-ryegrass mixtures

AIM: A principal goal of grassland management is to minimize the use of artificial fertilizers by maximising the productivity of nitrogen-fixing leguminous plants such as clovers. The objective of this study was to investigate whether a plant-growth-promoting strain of the free-living rhizosphere fungus Trichoderma hamatum (GD12) could be used as a natural and sustainable means of enhancing the competitiveness of white clover (Trifolium repens) while allowing increased productivity of both clover and ryegrass (Lolium perenne) in mixed species systems. METHODS: An assay was conducted in rhizotrons with white clover and ryegrass sown alone and in mixture and in soils inoculated and non-inoculated with GD12. Plant height, growing rate, phenological stage, number of Rhizobium nodules and biomass were assessed. A histological study of Rhizobium nodules and a stable isotopes analysis was conducted to determine the N fixation capacity of white clover. RESULTS: When introduced as a soil inoculant, the fungus increased biomass production of both plant species and shortened their phenological cycles. Furthermore, in clover, GD12 enhanced plant height and growth rate and stimulated Rhizobium nodulation, while ¹⁵ N stable isotope analysis demonstrated increased N₂ fixation. CONCLUSION: This shows that soil amendment with a beneficial strain of saprotrophic fungus bestows a competitive advantage to white clover in clover-ryegrass mixtures and provides a sustainable mechanism for improving the mixture productivity.