Strategies to reduce plant height in dual‐use intermediate wheatgrass cropping systems

Abstract

AbstractIntermediate wheatgrass [IWG; Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] is a perennial cereal and forage crop marketed for its grain, Kernza. Lodging, which is correlated with plant height, can reduce IWG grain yield. Our goal was to determine the effects of the plant growth regulator trinexapac‐ethyl (TE) application rate; forage harvest timing; and N rate on IWG plant height, lodging, aboveground biomass, grain yield, and harvest index. The experiment was established in 2015 in southern Wisconsin using a population of IWG bred for increased grain yield. The experimental design was randomized complete blocks with three replications of a factorial arrangement of three factors: TE rate (0, 0.22, 0.66 kg a.i. ha−1), forage harvest timing (unharvested, summer, summer + fall, spring + summer + fall), and N rate (90 and 135 kg N ha−1). Responses were measured in the second (2017) and third (2018) production years of IWG. Lodging was not observed. No interactions among treatment factors were detected. Plant height was 6% lower, grain yield was 26% higher, and harvest index was 48% higher in the low TE rate treatment compared to non‐treated, averaged across other factors. Harvesting forage in the spring + summer + fall reduced plant height by 7% compared to unharvested control but reduced grain yield by 11%. The high N rate increased plant height by 4% and grain yield by 26%. Using TE can be a viable strategy to reduce plant height and increase grain yield in IWG dual‐use (grain and forage) production systems.