Managing Global Resources for a Secure Future

Intermediate wheatgrass (Thinopyrum intermedium L.; IWG) is a cool-season forage grass currently undergoing selection for grain yield for use as a perennial cereal crop (DeHaan et al., 2005). A primary challenge limiting IWG grain production is stem lodging, which hinders pollination, grain fill, and reduces overall grain quantity. Lodged stands can harbor bacterial and fungal growth, compromising grain quality and reducing profits for growers. Trinexapac-ethyl (TE) and prohexadione-calcium (PC) are widely used plant growth regulators (PGRs) for mitigating lodging and improving seed yield in the grass seed industry, and have potential for use in IWG. We tested the effect of PGR type (non-treated control, PC, and TE) and nitrogen (N) fertilizer rate (0, 40, 80 kg N ha-1) on IWG lodging, plant height, and grain and biomass yield for three years at St. Paul, MN. In 2015 and 2016, TE reduced lodging and increased IWG grain yields by 65 to 95% relative to PC and the non-treated control. IWG that received 40 kg N ha-1 had 23 to 30% greater grain yields compared to 0 and 80 kg N ha-1, respectively. The third year of data collection in 2017 will evaluate effects of PGR application and N fertilization on IWG yield stability as stands mature. Identifying the optimal N rate and PGR type for IWG seed production is critical for the economic feasibility of IWG and utilizing PGRs in perennial grain cropping systems across the United States.