Assessing Thinopyrum intermedium establishment and agronomy in the maritime region of Canada

Abstract

Agricultural intensification has favoured simplified annual cropping systems to maximize short-term yield, but these practices have contributed to soil degradation, nutrient loss, and a reduced climate resilience. Integrating perennial plants into annual dominated agriculture offers an opportunity to balance productivity with ecological function. However, perennials operate under different developmental and resource allocation strategies than annuals, which creates challenges for the breeding and adoption of perennial crops for grain production. In addition, there is a limited understanding of perennial grass optimization for agriculture across diverse climates. Thinopyrum intermedium (intermediate wheatgrass; Kernza®) is a perennial grass developed for dual purpose grain and forage production. The deep rooting system of Th. intermedium provides environmental benefits that improve soil health and mitigate the impact of annual cropping systems. This thesis evaluated the agronomy required to optimize Th. intermedium performance under maritime conditions in Canada. The establishment strategies, stand age dynamics, intercropping compatibility, and nitrogen management were assessed in field experiments. Results demonstrated that stand age was a dominant regulator of plant trait expression and grain yield, and that early establishment conditions influenced the long-term plant allocation strategies. Compatible intercropping systems, particularly annual forage mixtures, enhanced cumulative biomass production in stands without compromising Th. intermedium persistence or grain yield. Annual barley was an incompatible intercropping species and inhibited the establishment of Th. intermedium, resulting in reduced stand performance. Nitrogen management influenced the developmental plant traits but did not prevent grain yield declines with stand age, highlighting perennial trade-offs between reproduction and persistence. Collectively, this research advances the understanding of perennial grain management by identifying agronomic decision pathways for performance optimization, aligning management with perennial developmental phases, and supporting the integration of diversified cropping systems in the maritime region of Canada. Widespread adoption of perennial grains requires framing agricultural success in terms of economic stability and ecological function. This thesis contributes to the development of agricultural systems that align productivity with environmental stewardship to secure stability in food production.