Effects of Forage Harvest on Non-Structural Carbohydrates and Spring Regrowth of Kernza Intermediate Wheatgrass.

Kernza ® intermediate wheatgrass (Thinopyrum intermedium) is a widely adapted, high-yielding, high-quality cool-season grain and forage dual-use perennial grass. Early spring regrowth of perennial grass is relevant to extend its utilization period. Non-structural carbohydrates stored in rhizome and stubble are important storage sources for spring regrowth. This study compared three forage cutting treatments after grain harvest (no harvest, summer harvest, and summer and fall harvest), in a replicated complete blocks design with three replications at Arlington, Wisconsin, USA. Kernza seeds were selection cycle 4 from The Land Institute, KS, and the plants were sown in fall of 2015. Rhizome and stubble were harvested twice on October 14^th and November 17^th in 2016. Water soluble carbohydrates (WSC) were 20%, accounting for 99% of the total NSC, in rhizome and stubble for the one-year old plants. The WSC concentration in rhizome significantly higher than that of stubble, but the total WSC content of stubble was higher than that of rhizome because the stubble dry weight was much higher. The WSC concentration of October harvest time was lower than that of November harvest time. The WSC concentration in the stubble of control was higher than that of clipping treatments in both dates, but no significant difference sin total WSC content were found. There were significant correlations between the regrowth rate with the stubble WSC concentration and content in October harvest time. In conclusion, delaying harvest time could increase the WSC content in one-year old Kernza stubble, while clipping after grain harvest could decrease the WSC content in stubble, thus affecting the regrowth of the grass in next spring.