Perennial crops have fewer environmental impacts compared to annual crops, but there are no perennial grains available to replace the annual grains that occupy a majority of U.S. cropland. Here we report grain and biomass yields from an improved breeding population of intermediate wheatgrass (IWG) [Th inopyrum intermedium (Host) Buckworth & Dewey], a perennial grass being domesticated to serve as the fi rst widely grown perennial grain crop. Our objective was to measure grain and biomass yields of this improved grain-type IWG (TLI-C2), a forage variety of IWG (cultivar Rush), and switchgrass (Panicum virgatum L.) in response to N fertilization rates ranging from 0 to 200 kg N ha -1 . TLI-C2 grain yields responded quadratically to increasing N rates in all but one environment, but yields declined at high N rates due to lodging. TLI-C2 grain yields were highest during the fi rst year of fertilization, yielding 961 and 893 kg ha -1 when fertilized at agronomically optimum nitrogen rates (AONRs) of 61 and 96 kg N ha -1 for stands seeded in fall of 2011 and spring of 2012, respectively. Grain yields declined with stand age. When fertilized with AONRs for grain, biomass yields of TLI-C2 harvested aft er grain ranged from 9.2 to 12.3 Mg ha -1 and had similar forage and bioenergy quality characteristics compared to Rush, which demonstrates the potential to manage TLI-C2 as a dual-use cropping system for both grain and forage.

Plant breeders are increasing yields and improving agronomic traits in several perennial grain crops, the first of which is now being incorporated into commercial food products. Integration strategies and management guidelines are needed to optimize production of these new crops, which differ substantially from both annual grain crops and perennial forages. To offset relatively low grain yields, perennial grain cropping systems should be multifunctional. Growing perennial grains for several years to regenerate soil health before rotating to annual crops and growing perennial grains on sloped land and ecologically sensitive areas to reduce soil erosion and nutrient losses are two strategies that can provide ecosystem services and support multifunctionality. Several perennial cereals can be used to produce both grain and forage, and these dual-purpose crops can be intercropped with legumes for additional benefits. Highly diverse perennial grain polycultures can further enhance ecosystem services, but increased management complexity might limit their adoption.

'MN-Clearwater' (Reg. no. CV-287, PI 692651) is the world's first commercial foodgrade intermediate wheatgrass [IWG; Thinopyrum intermedium (Host) Barkworth & D.R. Dewey subsp. intermedium] grain cultivar. It was developed as a synthetic population at the University of Minnesota, St. Paul, MN, and released in August 2019. Intermediate wheatgrass is a perennial grain crop currently undergoing domestication and is known for its extensive long root system that can recycle soil nutrients and sequester carbon. MN-Clearwater (experimental designation MN1504) was created by intercrossing seven parents selected for high grain yield, reduced shattering, high free grain threshing, reduced lodging, and uniform maturity. MN-Clearwater was advanced for two generations before being evaluated in statewide yield trials, after which the fourth seed generation was released as the cultivar in a limited public release. In variety trials across Minnesota, MN-Clearwater produced 696 kg ha −1 (621 lb ac −1) of grain with minimal lodging and negligible disease levels. The first 2 yr produce the highest grain yields under Minnesota conditions, and third-year yields are significantly lower (average reduction of 77%) than the first 2 yr. As the first IWG cultivar released for sale under the Kernza trade name (The Land Institute), we expect this population to be a cornerstone resource for the IWG research community as well as for interested growers, food processors, and commercial partners. MN-Clearwater grain is sold as Kernza perennial grain.

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Increasing intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] grain yield and maintaining yield over the life of a stand will be critical to the economic viability of Kernza (The Land Institute) grain production. Research on perennial grasses has shown that seed yield can be enhanced by (a) mechanically defoliating the stand for hay production and (b) increasing row spacing. We evaluated the interacting effects of row spacing and defoliation across the 4-yr life of an intermediate wheatgrass (IWG) stand in St. Paul, MN. We measured grain yield, harvest index, lodging, and yield components including grain mass and number of tillers, spikes, and grains. Data was analyzed with linear mixed models and partial least squares path analysis. Overall, grain yield declined substantially over time, from a mean of 880 kg ha −1 in 2015 to 276 kg ha −1 in 2018. Wider row spacings tended to increase grain yield. Defoliation increased grain yield in the first 2 yr, but may have decreased stand vigor in later years. Neither management practice fundamentally mitigated yield decline. The main cause of yield decline was the reduction in grain number per high-yielding spike, which dropped by roughly half after the first year. The proportion of spikes that were high yielding also declined over time. Increasing competition among reproductive units likely contributed to yield decline, but there is also evidence that resource allocation to reproduction declined over time. Future research in IWG breeding and management should focus on maintaining high grain number, reducing intra-stand competition, and increasing resource allocation to reproduction.Abbreviations: Ctrl, no defoliation; Fa, defoliation only in fall; HI, harvest index; IWG, intermediate wheatgrass; R/FR, red/far red; Sp, defoliation only in spring; SpFa, defoliation in spring and fall; TKW, thousand kernel weight; YC, yield component.

Historically, agroecosystems have been designed to produce food. Modern societies now demand more from food systems-not only food, fuel, and fiber, but also a variety of ecosystem services. And although today's farming practices are producing unprecedented yields, they are also contributing to ecosystem problems such as soil erosion, greenhouse gas emissions, and water pollution. This review highlights the potential benefits of perennial grains and oilseeds and discusses recent progress in their development. Because of perennials' extended growing season and deep root systems, they may require less fertilizer, help prevent runoff, and be more drought tolerant than annuals. Their production is expected to reduce tillage, which could positively affect biodiversity. End-use possibilities involve food, feed, fuel, and nonfood bioproducts. Fostering multidisciplinary collaborations will be essential for the successful integration of perennials into commercial cropping and food-processing systems.

Intermediate wheatgrass (Thinopyrum intermedium; IWG) is a perennial cereal crop undergoing development for grain production; however, grain yield declines of >75% are often observed after year 2 of the perennial stand and may be linked to soil nutrient depletion. Intercropping IWG with a perennial legume such as alfalfa (Medicago sativa) could benefit nutrient cycling while increasing agroecological diversity. Intermediate wheatgrass was established at five environmentally diverse sites in Minnesota, USA in (1) bi-culture with alfalfa, (2) non-fertilized monoculture and (3) monoculture fertilized annually in the spring with 80 kg N/ha. At northern sites where alfalfa growth was favoured, IWG grain yields were reduced in year 2 by growing IWG in bi-culture with alfalfa, relative to the monoculture systems. Across all sites IWG grain yield decreased by 90% in the non-fertilized monoculture, 80% in the fertilized monoculture and 65% in the bi-culture from year 2 to 4 and plant macronutrient concentrations decreased by 25–70%. In year 4, IWG grain yield was similar or greater in the bi-culture than the fertilized monoculture at three of the five sites and alfalfa biomass was correlated positively with grain yield, harvest index and nutrient uptake in the year 4 bi-culture. Chemical-nitrogen fertilization increased grain yields in year 2 but did not mitigate the decline in yields as stands aged. Intermediate wheatgrass in the bi-culture had similar yields and nutrient uptake and lower yield declines than the chemically fertilized stand at sites where alfalfa growth was maintained throughout the life of the stand.

Management systems that produce both grain and biomass coproducts could enhance the profitability of the novel perennial grain crop Kernza intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] (IWG). Harvesting IWG for grain typically results in a straw harvest; in addition, vegetative biomass can be cut in spring, fall, or both for hay production. We evaluated the interacting effects of defoliation and row spacing on yield, forage quality, and economic return across the 3-yr life of a conventionally managed IWG stand in St. Paul, MN. We measured straw and hay yield and forage quality and then used recent hay auction results to model forage price and total potential value. We then used estimated production costs to calculate potential net return from straw production alone and with additional hay harvests. Overall, straw was more valuable than hay, despite being of much lower quality, since yields were 3-4 times greater. Straw potential value was similar to the cost of producing both straw and grain, greatly reducing the financial risk in Kernza grain production. Hay production was almost always profitable. Straw and hay yield and value were greater in 15-and 30-cm rows than in 61-cm rows. Defoliating in both spring and fall led to lower hay and straw yields in the third year. Our results indicate that the best strategy for achieving consistent high net return to biomass production is to plant in 15-or 30-cm rows and only cut hay in the fall.Abbreviations: ADF, acid detergent fiber; CP, crude protein; Ctrl, no defoliation; Fa, defoliation only in fall; GDD, growing degree days; IWG, intermediate wheatgrass; NIRS, near-infrared reflectance spectroscopy; NDF, neutral detergent fiber; RFV, relative feed value; Sp, defoliation only in spring; SpFa, defoliation in spring and fall.