Organically managed intermediate wheatgrass (Thinopyrum intermedium) as a dual-use grain and forage crop

Abstract

Intermediate wheatgrass (Thinopyrum intermedium), a historically managed forage crop for livestock, is currently being domesticated to produce the cereal grain crop named KernzaⓇ. This study examines using intermediate wheatgrass as both a grain for human consumption and feed for livestock in a dual-use, organically managed system, and consequences for environmental quality. This was done by comparing agronomic and environmental responses to different fertilization strategies (none, commercial mineral fertilizer, or manure) and defoliation to simulate biomass removal for forage. Agronomic measurements included grain, straw, and forage yield as well as environmental effects, specifically nitrogen mineralization, total carbon, total nitrogen, and soil gas emissions. Treatments were carried out at two sites, in south central Minnesota and central Kansas. Results showed that manure increased grain, straw, and forage yields compared to unfertilized treatments in year two in MN and KS. In addition to yields, forage nutritive value increased in manure fertilized treatments compared to unfertilized control treatments in the second year at both sites. Soil extractable nitrogen differed across seasons in MN in years one and two, but KS only differed in year two. There was a difference in nitrogen mineralization among treatments and across seasons in MN in year 2. KS did show an interaction among treatments and season in 2020 and a difference across seasons in both years. Soil gas emissions were higher for CO2 in manure fertilized plots in the second year in MN, but there were no differences between treatments for CH4, N2O, or NH3. At the end of the experiment, soil carbon was higher in manure fertilized plots in MN. In summary, manure fertilizer improved agronomic variables important to farmers but environmental impacts of this practice should be considered. Manure application can result in increases in soil gas emissions thus exacerbating human impact on the climate. However, manure showed potential to increase soil organic carbon and potentially offset soil gas emissions associated with manure addition.