Perennial Grain: Persistent or Fleeting?

Today, most crops are annuals – they are only grown for one season before harvest and replanting. Common annual crops include corn, soybean, rice and wheat. We grow these species because they have high yields per acre, but as annuals their production tends to result in erosion, nutrient pollution from fertilizer runoff and soil carbon loss. Perennial crops might help us address some of these issues. Since they stay in place for several years, they offer greater ground cover and have deeper root systems, helping to keep soil and nutrients in place. Alfalfa is a good example of a perennial crop with these types of benefits – it can significantly reduce erosion and nitrate leaching into groundwater.

Perennial grains are another promising avenue to reap these environmental benefits. As a PhD student and FFAR Fellow at the University of Minnesota I study Kernza®, a perennial grain crop developed from varieties of Intermediate wheatgrass (Thinopyrum intermedium) that have been selected for larger seed size, shorter stature and other desirable grain production traits. Kernza can be harvested for grain and forage and is drought tolerant, offering farmers flexibility and resilience in their operations. While Kernza is a perennial in the sense that it does not need to be replanted from seed every year, the per-acre yield declines over time. As a result, farmers typically grow it for three years and then return to annual crops. Advances in breeding may enable longer rotations in the future, but Kernza is currently a 3-year crop for most farmers.

We know that Kernza production helps reduce nitrate leaching to groundwater, reduces erosion compared to annual crops, reduces soil organic carbon losses and improves soil structure, but questions remain about the persistence of these benefits after the system returns to annual crop production. Do these benefits accrue only during the perennial grain crop production itself? Do they persist during all or part of the following annual crop? Or are gains in soil health lost upon termination of the perennial grain crop? Specifically, we want to know if soil carbon content and the physical stability of soil change when the grain crop is terminated, and if the method of termination – through tillage or herbicide – makes a difference. Since most Kernza production is organic, termination requires aggressive tillage to kill the plants without herbicide to ready the field for re-planting. This will almost certainly have impacts on the soil, but very little research currently exists on this topic.

My research in the Gutknecht Lab will explore these questions using a five-year Kernza fertility experiment that ended in August 2025 and can now be terminated and transitioned back to a corn-soybean rotation. Some plots will be left in Kernza as a control to allow us to answer two experimental questions: 1) Does a multi-year Kernza rotation result in improved yields and soil health for subsequent corn and soybeans crops? 2) Does the termination method of the Kernza stand (chemical vs. mechanical) impact subsequent corn and soybean yields and soil health benefits including soil organic carbon, labile soil carbon fractions and soil aggregate size and stability?

By answering these questions, we will be able to provide better management recommendations to maintain soil health benefits after Kernza production, for example, by suggesting a specific termination method or length for the rotational crops. We will also be able to assess if Kernza can provide benefits for the following corn or soybean crop. I am excited about this experiment because I am interested in the impacts of agricultural systems on the environment, including soil health, water quality, habitat quality and emissions of CO₂, methane, and N₂O.

I am grateful to the individuals at General Mills who supported my application to the FFAR Fellows program and made this possible! Connecting with other students and receiving professional mentorship and training has already enriched my graduate school experience and equipped me with additional skills to support a career in sustainable agriculture research.