Germination and Emergence of Primed Grass Seeds Under Field and Simulated-field Temperature Regimes

Seed priming may enhance establishment success of cool-season range grasses which must compete with annual weeds for early spring moisture. Previous priming studies have confirmed germination rate enhancement for these species but relative treatment effects under field-temperature conditions have not been assessed. We primed seeds of thickspike wheatgrass [ Elymus lanceolatus (Scribn. and J. G. Smith) Gould], bluebunch wheatgrass [ Pseudoroegneria spicata (Pursh) Löve], Sandberg bluegrass ( Poa sandbergii Vasey.) and bottlebrush squirreltail [ Elymus elymoides (Raf.) Swezey] and evaluated their relative emergence rate in three soil types as a function of spring-planting date. Germination response was simultaneously evaluated in laboratory germinators that were programmed to simulate the field-temperature regime at planting depth. Seed priming enhanced both germination and emergence rate with the greatest effect occurring during the earlier, cooler planting dates. Total emergence and emergence rate in the field were lower than for the equivalent germination response in the laboratory. Thermal-germination response was modelled and predictions developed for evaluating potential germination under late winter/early spring soil-temperature regimes. Modelling results predicted that greater germination enhancement would have been possible at earlier planting dates than were measured in the field experiment.