Effects of seeding date on grain and biomass yield of intermediate wheatgrass

Abstract

Intermediate wheatgrass (Thinopyrum intermedium) (IWG) is a perennial grass being domesticated for grain production with potential to provide economic return and ecosystem services across a broad geographic range in North America, yet optimum seeding dates for grain and biomass yield are unknown. Our objective was to determine the effect of late‐summer, fall, and spring seeding dates on grain and biomass yield of a grain‐type IWG population. Trials were conducted at St. Paul and Roseau, MN, Kalispell, MT, and Salina, KS. Seeding dates ranged from August to June of the following year. Grain and biomass yields were highest when seeded at the earliest late‐summer date for all environments except for Kansas, where a September 29 seeding date produced the greatest grain and biomass yields. Little to no grain was produced from spring seedings in the first production year, substantiating that photoperiod and vernalization requirements are needed for seed head induction. Grain and biomass yields were positively correlated to cumulative growing degree days (GDD) from seeding date to winter dormancy. A quadratic response was observed at Salina, KS, where seed yields maximized when GDD accumulation reached 912. Accumulation of vernalization units throughout fall, winter, and spring after seeding was also positively correlated with grain yield. The minimum vernalization units for grain production varied from 50 to 87 across sites. Results highlight important associations between thermal units and IWG grain yield when seeded in late summer; however, other variables affecting IWG seed head induction (e.g., photoperiod, snow cover) require further study.

Agronomic assessment of two populations of intermediate wheatgrass—Kernza® (Thinopyrum intermedium) in temperate South America

“…The estimation of the cold requirements consisted of two steps: the vernalizing value of a given day was first computed [ VV ( i )], and then the slow‐down factor [ SFV ( i )] was calculated as the ratio of completion of the total vernalization requirements: $$${VV}(i)=\max \left(1-{\left[\frac{{T}_{\text{vern}}-{T}_{\text{mean}}(i)}{{{Ampli}}_{\text{vern}}}\right]}^{2},\unicode{x02007}0\right),$$$ $$$\left\{\begin{array}{c}{SFV}(i)=\frac{\left[{\sum }_{j={D}_{\text{emer}}\unicode{x02007}\mathrm{or}\unicode{x02007}{D}_{{\rm{h}}\text{arv}}}^{i}VV(j)\right]-V{V}_{\min }}{V{V}_{\text{req}}-V{V}_{\min }},\\ {SFV}(i)=\max \{\min [{SFV}(i),1],0\},\end{array}\right.$$$where VV ( i ) is the vernalization unit on day i , T vern is the temperature to reach an optimal vernalization value, T mean is the mean temperature on day i , and Ampli vern is the temperature range with vernalizing effects. In this study, we used the best estimates calculated by Duchene et al (2021) and also used by Jungers et al (2022): T vern = 4.5 and Ampli vern = 7.4. The accumulation of vernalization units was calculated by summing VV i from the day of emergence to the first grain harvest and between this one and the second grain harvest (Table 1).…”

“…Low‐latitude regions may not accumulate enough days of cold temperature to meet those requirements to initiate flowering, resulting in lower grain yields. The vernalization requirements of Kernza may not only be a constraint to its agronomic adaptation to low‐latitude regions but are also being studied in high‐latitude regions of the world with cold winters due to their negative impact on 1st‐year grain yields (Cattani & Asselin, 2022; Jungers et al, 2022). Although the expansion of a perennial crop such as Kernza would be advantageous for every region, breeding advances have only taken place in cold areas of North America.…”

Intercropping legumes and intermediate wheatgrass increases forage yield, nutritive value, and profitability without reducing grain yields

“…In general, planting IWG and the legumes together in the spring was no better than planting in the fall. Although it is widely known that IWG does not produce grain in the summer of the establishment year when it is planted in the spring due to lack of vernalization induction (Duchene et al, 2021;Olugbenle et al, 2021;Jungers et al, 2022;Locatelli et al, 2022), we hypothesized that some advantages could be manifested in the first grain production year. However, growing IWG for a longer establishment period (i.e., with more ), for the control IWG monoculture (i.e., without N fertilization or weed removal), and four IWG intercrops with legumes (Berseem clover, Kura clover, red clover, alfalfa) sown at two planting seasons (spring, fall), at Arlington, Wisconsin, USA.…”

“…Additionally, effective stand establishment is critical for IWG's long-term productivity, and in intercropping systems, it can be influenced by both the planting date and the row spacing. For IWG monocultures of the USA Midwest, late summer and early fall typically achieve successful establishment of Kernza grain production systems (Jungers et al, 2022). Intermediate wheatgrass requires a two-stage induction period with vernalization for flowering (Duchene et al, 2021;Locatelli et al, 2022), thus spring seedings will not produce grain during the first year (Olugbenle et al, 2021;Jungers et al, 2022).…”

“…For IWG monocultures of the USA Midwest, late summer and early fall typically achieve successful establishment of Kernza grain production systems (Jungers et al, 2022). Intermediate wheatgrass requires a two-stage induction period with vernalization for flowering (Duchene et al, 2021;Locatelli et al, 2022), thus spring seedings will not produce grain during the first year (Olugbenle et al, 2021;Jungers et al, 2022). For IWG-legume intercropping systems, limited information is available.…”