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

Abstract

Intermediate 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.Abbreviations: GDD, growing degree days; IWG, intermediate wheatgrass; TE, trinexapac-ethyl This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Maintaining grain yield of Th. intermedium across stand age through constant spike fertility and spike density: Understanding its response to various agronomic managements

“…While reducing tiller density at grain harvest, the autumn defoliation had no impact on grain yield as compensation, with higher TKW, was reported. These results are in line with previous studies where forage harvest, when performed in summer (i.e., after grain harvest) or in autumn (Zimbric et al, 2021) didn't impact grain yield or even increased it (Pugliese et al, 2019;Culman et al, 2023). In addition, the study of Dick et al (2018) highlighted that the grazing of residues increased seed yield and harvest index compared to the removal or chopping of residues.…”

“…Variable yield responses to N fertilization have previously been reported in the literature, either with increases (Zimbric et al, 2021), decreases (Frahm et al, 2018) or no impact on Th. intermedium grain yield (Dobbratz et al, 2023).…”

“…intermedium, various management options have been studied to improve grain yield in young stands or to maintain yield in aging stands including crop defoliation in summer (i.e., just after grain harvest), in autumn or in spring, either by grazing (Dick et al, 2018) or mowing. As the spring mowing tends to decrease grain yield (Zimbric et al, 2021;Culman et al, 2023), the summer and autumn mowing can increase grain yield compared to no forage harvesting (Pugliese et al, 2019;Culman et al, 2023), but without mitigating yield decline with stand age (Hunter et al, 2020a).…”

Forage harvest management impacts “Kernza” intermediate wheatgrass productivity across North America

“…Commercial production of IWG grain is just starting, comprising 1000 ha located mainly in the North Central USA (Lanker et al., 2019; Skelly & Peters, 2021). While the main motivation for early‐adopter growers is the transition to more sustainable agriculture (Lanker et al., 2019; Wayman et al., 2019), two major challenges for IWG as a viable perennial grain crop are low seed yields (between 112 and 1150 kg ha −1 ; Franco et al., 2021) and 40–60% grain yield decline over the first 3 years (Franco et al., 2021; Hunter et al., 2020a; Jungers et al., 2017; Zimbric et al., 2021). In addition, plot‐level grain yield has been evaluated in few studies and locations, and a robust understanding of published realistic IWG yields across diverse environments is lacking in the literature.…”

Vernalization requirements of Kernza intermediate wheatgrass

“…Plant height increased with the length of incubation period up to 7 wk (Figure 1c). Our plants in the greenhouse were shorter than plants grown in field experiments (Jungers et al, 2018;Zimbric et al, 2020). Plants at 7 wk had the largest number of spikes per plant and spikelets per plant (Figure 2a, c).…”