Energy, water and carbon exchange over a perennial Kernza wheatgrass crop

The ecological impacts resulting from global warming and conventional agricultural practices are predicted to affect crop productivity and reduce the land area available for agriculture in the near future. Perennial crops can sustain high yields without replanting for numerous consecutive years, resulting in important climate benefits. At this time, the coupling between these ecosystems and the atmosphere is not well understood. The objective of this study was to examine the magnitude and temporal variability of the surface energy, water and carbon exchanges in a perennial Kernza wheatgrass crop in Salina, north-central region of Kansas (KS), USA. The study period comprised approximately 4.5 years (May 2012-October 2016) of eddy covariance observations collected at the US-KLS AmeriFlux tower established in April 2012. We analyzed the temporal dynamics of the fluxes of radiation, water and carbon in the perennial wheatgrass crop during five growing seasons. The results obtained here demonstrated the ability of the perennial Kernza in maintaining a relatively high water-use efficiency throughout the whole growing season and its highest evapotranspiration and net carbon uptake rates, particularly when compared to annual counterparts. These findings are important in order to better understand the coupling between the hydrologic and carbon cycles in these novel agroecosystems as well as to understand the benefits and disadvantages in relation to annual crops.