How does nitrogen and forage harvest affect belowground biomass and nonstructural carbohydrates in dual‐use Kernza intermediate wheatgrass?

Abstract

Intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] is a cool‐season perennial forage grass, whose grain is commercialized in the United States as “Kernza.” Its extensive root system may help in reducing soil erosion, water pollution, and C emissions. Nitrogen fertilization and forage harvest intensity may affect the belowground biomass and nonstructural carbohydrate (NSC) concentrations, which may affect growth in subsequent years. We compared N doses and forage harvest treatments in a replicated complete block experiment in three environments (location‐years: Arlington, WI, 2016 and 2017; and St. Paul, MN, 2016). Seeds were sown in the fall, Kernza grain was harvested in the following summer, and rhizomes and roots were sampled in fall to a depth of 0.1 m over 2 yr. The water‐soluble carbohydrates (WSC) accounted for 97–99% of NSC, across environments. The WSC concentration was higher in rhizomes than in roots in both years, but WSC mass was higher in roots than rhizomes due to greater root biomass. Nitrogen generally did not change NSC concentrations across years, but reduced WSC in rhizome the second year in WI. Forage harvest did not affect NSC concentrations across locations and years. Belowground biomass to 1‐m depth in the fall of the second year in Wisconsin averaged 478.3 g m−2 regardless of treatment. Summer forage yield in the following year was positively associated with root biomass in the fall. These results suggest that harvesting forage in a Kernza dual‐use system is not detrimental to intermediate wheatgrass above‐ and belowground productivity.

Reductions in soil water nitrate beneath a perennial grain crop compared to an annual crop rotation on sandy soil

“…Nearly 63% of the IWG root biomass was found in the top 0-15 cm depth. Previous work has reported IWG belowground biomass to be 3.28 Mg ha −1 in the first 10 cm, on average, in Minnesota and Wisconsin (Sakiroglu et al, 2020). In an intra-annual study of root biomass beneath IWG, total root biomass from 0 to 20 cm peaked between 3.5 and 4 Mg ha −1 in June and July before declining to 1 Mg ha −1 at the end of the growing season (Pugliese et al, 2019).…”

Ecological Intensification of Food Production by Integrating Forages

“…In its first year, Kernza grain yield in the North Central US varies from 112 to 1150 kg ha −1 with large declines usually observed the following years (Table 1). Some practices are recommended to avoid Kernza grain decline such as increasing N fertilization [180,181], widening row spacing [182], post-harvest management practices (e.g., defoliation [182,183], stand-thinning [183,184], or chopping and burning [183], but thus far results have been highly variable. In contrast, first year Kernza forage harvest varies from 3243 to 11,753 kg ha −1 in summer but also shows a slow decline over time (Table 1).…”

Vernalization requirements of Kernza intermediate wheatgrass

“…Its dual use (grain and forage production) is a key factor for increasing productivity and profitability in this novel crop (Pugliese et al., 2019; Ryan et al., 2018). Kernza intermediate wheatgrass adapts well to a dual‐use system since the harvesting of forage does not negatively impact the above‐ and belowground biomass productivity (Sakiroglu et al., 2020). Moreover, forage quality of Kernza intermediate wheatgrass in a dual‐use system is suitable for lactating beef cows, dairy cows, and growing heifers (Favre et al., 2019).…”