Investigating Fall Grazing in Kernza to Improve Grain Yields

Commodities

Practices

More than 4,000 acres of Kernza are grown in the North Central region of the U.S., according to surveys by The Land Institute. An important distributor of Kernza, the Perennial Promise Growers Coop, has reported sellouts of organic grain in the last two years, indicating acreage will grow although most growers I talk to struggle with low yields. Grain yields of 500 lb/acre or less are commonly reported, although Kernza yields can be improved with fertilization. Many growers without access to organic on-farm manure, like myself, must purchase off-farm organic manure, which is expensive and slow to result in yield gains. Kernza produces more than 14,000 lb/acre of biomass during the course of the season, representing a large reservoir of nutrients that if unlocked, could contribute to yield gains. Grazing of fall regrowth could naturally cycle the nutrients tied up in the extensive biomass left behind after Kernza harvest (straw plus regrowth), and could control the thick thatch level and open up the crowns to receive more light the following year. "Cleanup" and recycling in this system with grazers could be an important tool for improving grain yields through ruminant digestion conversion of plant nutrients, manure deposition, and soil mixing.

Grazing animals were a crucial factor in nutrient cycling in natural tallgrass prairie systems for millennia, the system that Kernza mimics. In Fields Best's 5 years of growing Kernza, the farm has surface spread compost, pelleted poultry manure, and has chopped and removed post-harvest straw, in different years. Nicole realized that chopping and removing as hay or straw the post-harvest material, was resulting in the export of several hundred pounds of nutrients from the field that had real value; however, the nutrient release from the perennial grass residues is slow. Grazing would perform in vitro composting, essentially, of the residue and convert the biomass to manure, which would aid with nutrient mobilization for Kernza plant uptake--this mechanism, through intensive (bison) grazing, was what sustained tallgrass prairie productivity in the U.S. for millennia. Grazing livestock hooves also can mix soil, contributing to nutrient mobilization and prevents nutrient stratification in soils, which can also limit plant access to soil fertility. The introduction of grazing into Kernza furthers the food-producing prairie restoration paradigm because it a) preserves the productivity of the beneficial perennial system, enabling more use, b) integrates crop and livestock systems to capture ecological synergies, c) enhances closed-loop on-farm biological cycles, and d) takes pressure off of farmers to purchase off-farm inputs and limits financial risk from lower operating loan values (less fertilizer needs to be purchased). The objectives of our study are to: 1) Work with a respected contract goat grazier in the area to establish 5-day grazing of replicated paddocks in Kernza post-harvest, paired with non-grazed exclosure areas; 2) measure soil nutrient status before and after grazing/non-grazing treatments; 3) monitor Kernza plant nutritional status and grain yields in grazed/non-grazed areas the year following grazing, and 4) perform outreach and education through field days, video production, and conference presentations on the outcomes.

Four replicated paddocks approximately one acre in size each will be established in a 20-acre Kernza field owned by Fields Best outside of East Troy, WI in fall 2026. Each grazed paddock with be paired with a non-grazed paddock of the same size, in a randomized complete block design, with 8 plots total. Goat Grazing of Wisconsin will set up the temporary fencing, water trough, and portable shelters per their usual protocols. Stocking rates will be determined using their standard protocols; with the typical levels of Kernza biomass available, we are estimating a goat stocking rate of 8-10 animals per acre, with the goal of keeping grazing activity under one week. Dr. Tautges will conduct soil sampling prior to grazing, and immediately after grazing; soil samples will receive a routine analysis for SOM, nitrate, phosphorus, potassium, and sulfur content, as well as percent total carbon and nitrogen. Paddock areas will be marked with permanent markers and the grazed/non-grazed plots will be sampled with 0.5-m2 quadrats, two per paddock at the time of Kernza anthesis in 2027; biomass will be dried and analyzed for total NPKS content. Grain yields will be collected in September 2027 each plot with a plot combine by harvesting 2x100-ft long strips with a Wintersteiger plot combine, bagging, and weighing the grain harvested from each plot. Statistical analysis will be perfomed using paired t-tests to compare grazed/non-grazed treatments. During the grazing period in 2026 and prior to harvest in 2027, we will hold a field day, inviting Kernza farmers, graziers, and Kernza end users, to observe grazing and the residual effects on the stand. We will collect video footage to be edited into short outreach videos for social media and the web. Kernza agronomic outcomes will be reported at grower conferences.