During his 39 years at McGill Donald L. Smith has conducted research in the production and physiology of crop plants, with an emphasis on plant-microbe interactions. The areas of research investigation have been: nitrogen metabolism, nitrogen fixation, root zone temperature stress and nodulation, development of methods for injection of metabolites into plants, barley production, use of plant growth regulators, intercropping, the dynamics of inter-plant competition, plant-microbe signaling, plants and climate change, biofuel crops, crop stress responses and biochar as a soil amendment.