The role of the deep roots of perennial cereal kernza in a drying climate

Summary in the original language of the document

Agricultural lands under annual crop production are prone to degradation and as the climate becomes increasingly variable researchers and farmers alike are looking at resilient crops such as perennial grains to produce food regeneratively. Perennial grain crops support a myriad of ecosystem services, such as reducing nitrate leaching, erosion control and increasing carbon storage. With their deep roots, perennial grain crops like Kernza (Intermediate wheatgrass) could furthermore avoid surface stresses such as droughts. This has however not been investigated before. Therefore we set out to determine the depth of root water uptake (RWU) of this crop and compared the contribution of deep roots before and after anthesis and between a year of adequate water supply (2019) and a year of drought (2018). Natural abundances of 2H and 18O were determined, but were unable to be used properly due to mistakes during sampling. A tracer application showed limited uptake from 2m depth. Furthermore, soil water content measurements were used to inverse model the soil hydraulic parameters under the Kernza crop in Hydrus 1D. Modelling RWU showed that the deep roots (>1m) were responsible for almost 50% of the RWU between anthesis and harvest in 2018, whereas they only contributed between 10% and 15% throughout 2019 and most of 2018 outside of the indicated period. Kernza may thus be an important addition to a farmers toolbox in areas with periodic droughts, but only if grain yields are increased to be competitive with annual cereals or when used as a multifunctional crop for grain, forage and other ecosystem services.