Land stewards world-wide are increasingly interested in perennial grains as the ecological consequences associated with intensive annual grain production become evident. Novel perennial grain crops, such as the dual-use forage and grain crop Kernza ®, show promise both as a source of edible grain but also for its ecosystem services. In contrast with annual cereals, Kernza’s deep rooting structure, belowground biomass accumulation, reduced input costs and decreased tillage frequency has led to early grower adoption and could potentially result in soil carbon sequestration and increased soil health. However, there are major gaps in the data demonstrating Kernza’s productivity in agricultural regions and climates outside of the Midwest U.S., as well as its capacity to sequester soil carbon, support soil biodiversity and/or soil health. To address these gaps, in 2017 we implemented a long-term cropping systems trial (3 years) to assess annual and perennial grain productivity (i.e., grain and biomass yields) and ecosystem service contributions under gradients of nitrogen fertilization and irrigation in the Mediterranean climate of California.