Effective weed suppression in dual‐use intermediate wheatgrass systems

Abstract

Intermediate wheatgrass [IWG; Thinopyrum intermedium (Host) Barkworth & D.R.Dewey] is a cool-season perennial forage grass bred for higher seed yield. It is the first perennial grain crop in the United States, commercialized as Kernza since 2015. Managing IWG as a dual-use grain and forage crop could provide several ecosystem services including conserving soil and clean water while increasing economic income to growers. However, little is known about the weed management risks associated with IWG. Therefore, we studied weed community composition, biomass, IWG grain, and aboveground biomass in a factorial experiment with two weed management treatments, two nitrogen fertilization rates, and four forage harvest schedules (no harvest, summer only, summer + fall, and spring + summer + fall).Over three production years, weed biomass decreased by 88% regardless of treatment, and the weed community composition changed from predominantly winter annual to perennial species. In the second and third production years the weed community composition remained relatively stable. Grain yield was 16% greater with 135 kg N ha −1 than 90 kg N ha −1 but was not affected by in-season forage harvest or weed management treatments in the second and third years. Grain yield decreased from 763 to 371 kg ha −1 over three years, while aboveground biomass remained stable. Weed presence did not affect yields in second and third years. Dual-use IWG cropping systems effectively suppressed weeds and IWG is a promising grain crop alternative for farmers interested in diversifying their cropping systems under similar conditions. Abbreviations: AIC, Akaike's Information Criterion; IWG, intermediate wheatgrass.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.

Ecological Intensification of Food Production by Integrating Forages

“…Kernza intermediate wheatgrass is a novel perennial grain and forage crop with the potential to provide multiple ecosystem services. Through its continuous above-ground productivity, i.e., perenniality, Kernza reduces annual weed populations [168], protects soil from erosion, and increases pollinators and insect diversity [169]. Kernza's perennial nature also leads to a reduction in nutrient leaching [170,171], an increase in the SOC pool and other beneficial soil properties [172], and improvements in biota linked to high soil quality [169,172].…”

Intercropping red clover with intermediate wheatgrass suppresses weeds without reducing grain yield

“…Weed management has not been widely studied in perennial grain crops and has the potential to contribute to improved crop productivity (Zimbric et al., 2020). Farmers have identified both organic and conventional weed management as a research priority in the development of perennial grain cropping systems (Lanker et al., 2020; Wayman et al., 2019).…”

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

“…An additional source of uncontrolled variability that may have interfered was the presence of weeds. Although weed biomass was very low in this experiment (Zimbric et al., 2020) weed root biomass would be concentrated in the first 10 cm of soil depth and could have increased sampling variability. Previous studies have also found contrasting results.…”

“…Furthers studies are needed to explore these mechanisms and potential tradeoffs in perennial grain systems. This is extremely relevant for Kernza, given the fact that grain yield has been reported to decline as the stand ages (Pugliese et al., 2019; Jungers et al., 2017; Zimbric et al., 2020).…”

“…Agronomic management of intermediate wheatgrass for forage has been investigated recently (Karn, Berdahl, & Frank, 2006; Lee, Donaghy, Sathish, & Roche, 2009; Liebig, Hendrickson, Berdahl, & Karn, 2008; Ogle, John, Tober, & Jensen, 2011). Furthermore, agronomic management practices of intermediate wheatgrass for optimizing both forage and grain yield in dual‐use systems is an increasing area of research (Favre, Munoz Castiblanco, Combs, Wattiaux, & Picasso, 2019; Hunter, Sheaffer, Culman, & Jungers, 2020; Hunter, Sheaffer, Culman, Lazarus, & Jungers, 2020; Pugliese et al., 2019; Zimbric, Stoltenberg, & Picasso, 2020). Understanding the mechanisms underlying biomass production, carbohydrate storage and utilization, and allocation to vegetative regrowth and reproduction over time is needed to develop management recommendations for dual‐use Kernza systems.…”