Can Grass-Endophyte Technology be Utilized to Build Soil Organic Matter and Improve Pasture Soil Function?.

Majority of cool-season forage grasses have the ability to form a symbiotic relationship with Epichloë fungal endophytes. This symbiosis is widely considered a defensive mutualism, whereby the endophyte gains shelter, food, and a mode of reproduction from the plant and in return produces toxic alkaloids that deter herbivores from eating the plant. Since the discovery of this type of symbiosis and because of the dramatic negative effects it can produce on grazing animals (with substantial economic losses), scientists have identified naturally occurring strains of Epichloë that lack the ability to produce mammal toxic compounds. Such ‘novel symbioses’ have been explored for more than two decades, with new combinations continually arriving on the market and made available to producers via the seed industry. To date, the development of these ‘symbiotically modified organisms’ has focused primarily on maintaining insect deterrence and grass productivity and persistence, while eliminating mammal toxicity. However, recent research has shown that these symbioses can have significant impacts on pasture soil carbon stocks and soil-to-atmosphere greenhouse gas emissions, leading to the hypothesis that grass-endophyte symbioses may also be utilized to build soil organic matter and improve pasture soil function. I will present data from several recently completed studies that evaluate endophyte effects on soil carbon and greenhouse gas emissions and explore possible mechanisms driving these effects, as well as significant remaining unknowns.