Progress report for LNC18-406
- Kernza® (grain harvested from intermediate wheatgrass; Thinopyrum intermedium) is becoming the country’s first widely available perennial grain crop, which has potential to be a profitable alternative crop that greatly decreases the environmental impacts associated with US agriculture. The ecological sustainability of Kernza could be further improved using legume intercropping practices to reduce or eliminate synthetic nitrogen fertilizer requirements and improve soil health. Problems being addressed include a) limited agronomic advice for managing legume/Kernza intercrops to optimize profitability and ecological services regionally, b) a lack of quantifiable soil health metrics resulting from legume/Kernza intercrops and c) insufficient support for farmers to develop and share information and experiences related to Kernza production. This project pursues solutions to these problems by conducting research trials on farm and at research institutions to develop agronomic recommendations for managing legume/Kernza intercrops, to quantify the soil health impacts from legume/Kernza intercrops, and to develop and support a Kernza Growers Network for farmers to engage and share knowledge with other farmers and researchers related to Kernza production.
- Research Approach - The research approach is to conduct experiments, both on-farm and at research institutions, to determine which legume species establish and persist well with Kernza as an intercrop in different regions of the Upper Midwest and Great Plains, and to measure the soil health impacts from these different intercropping systems. Educational Approach - The educational approach includes partnering with the regional outreach and education consortium "Green Lands Blue Waters" to host field days, winter workshops, webinars, and other opportunities to present new data and research findings, provide opportunities for on-farm research partners to share their experiences and knowledge, and to offer an opportunity for future Kernza farmers to seek information and engage with experienced Kernza farmers. Learning Outcomes - Agronomic knowledge of legume-Kernza intercropping systems to improve Kernza yields while reducing costly nitrogen fertilizers. We will determine which legumes work best as intercrops in three states, and develop recommendations for managing legumes with Kernza. Ecological knowledge quantifying the soil health impacts of legume intercrops, including changes in nitrogen mineralization. Outreach activities improving grower connectedness and providing education; management document, field days, and winter workshops. Skills and awareness for farmers to successfully produce profitable Kernza yields without expensive synthetic fertilizers.
- Research Conclusions - The research is ongoing, thus no conclusions are available at the time of this report.
- Farmer adoption actions - We are still collecting data on this topic, but we are aware of multiple farmers who have participated in our outreach activities that have planted Kernza or plan to plant Kernza in 2020.
Agronomic knowledge of legume-Kernza intercropping systems to improve Kernza yields while reducing costly nitrogen fertilizers. We will determine which legumes work best as intercrops in three states, and develop recommendations for managing legumes with Kernza. Ecological knowledge quantifying the soil health impacts of legume intercrops, including changes in nitrogen mineralization. Outreach activities improving grower connectedness and providing education; management document, field days, and winter workshops. Skills and awareness for farmers to successfully produce profitable Kernza yields without expensive synthetic fertilizers.
Kernza® (grain harvested from intermediate wheatgrass; Thinopyrum intermedium) is becoming the country’s first widely available perennial grain crop, which has potential to be a profitable alternative crop that greatly decreases the environmental impacts associated with US agriculture. The ecological sustainability of Kernza could be further improved using legume intercropping practices to reduce or eliminate synthetic nitrogen fertilizer requirements and improve soil health. Preliminary data show that Kernza can be effectively grown in mixture with legumes, but the agronomic practices needed to manage crop interactions to optimize profitability and ecological services are not well established and require regional assessment. This project will test four different legumes, each intercropped with Kernza as a biculture, in two experiments that will occur at six on-farm and three institutional research sites in Minnesota, Wisconsin, and Kansas. One objective is to identify legume intercrops that increase Kernza yield and reduce or eliminate nitrogen fertilizer needs. We will measure Kernza grain yield and nitrogen fertilizer offsets from atmospherically-fixed nitrogen provided by the legumes, and determine the economic implications related to these outcomes. We will quantify the effects of legume species on soil health characteristics, carbon sequestration and nitrogen transformations. Project partner Green Lands Blue Waters will develop and facilitate a Kernza grower network that will guide the design and execution of experiments and outreach and education events. Six farmers from three states of this network will host the on-farm Kernza legume intercropping experiments. The Kernza grower network will also include a panel of three experienced Kernza farmers to advise researchers and on-farm research hosts on Kernza management and the dissemination of our results. Early-adopter Kernza farmers are well-respected leaders in their community and well positioned to influence a much wider group of farmers in their networks, creating a multiplier effect of credible peer-to-peer farmer knowledge sharing. An outcome of this project will be the expansion of the grower network by recruiting future Kernza growers during our outreach and education events, which will include field days and winter workshops that demonstrate how to establish and manage Kernza-legume intercrops. Additional outputs will include a management document on Kernza-legume intercropping for Minnesota, Wisconsin, and Kansas. The research experiments included in this proposal, and the Kernza grower network and associated farmer-to-farmer education and outreach activities, were based on farmer-identified needs and designed in collaboration with the farmers listed in the “Team Experience and Roles” section.
Hypothesis: The null hypotheses being tested include:
- A range of legume species will establish and persist equally well when fall-seeded with Kernza in multiple different environments varying in soil type, temperature, and precipitation.
- Alternative hypothesis – Legume species especially suited to regional environments at the research sites will establish and persist better than other legume species when intercropped with Kernza.
- A range of legume species will have similar effects on Kernza grain yields when intercropped with Kernza at multiple environments varying in soil type, temperature, and precipitation.
- Alternative hypothesis – Legume species especially suited to regional environments at the research sites will result in higher Kernza grain yields in an intercrop compared to other legume species when intercropped with Kernza.
- Kernza grain yields will be lower when grown with legume intercrops compared to monoculture Kernza fields managed with organic N fertilizer.
- Alternative hypothesis – Intercropping legume species especially suited to regional environments at the research sites with Kernza will result in similar Kernza yields compared to Kernza monocultures fertilized with organic N fertilizer sources.
- Kernza monocultures and legume/Kernza intercrops will maintain similar levels of potential mineralizable N throughout the growing season.
- Alternative hypothesis – Legume/Kernza intercrops will have higher levels of potential mineralizable N in the soil compared to the Kernza monocultures throughout the growing season.
- Kernza monocultures will have similar water infiltration rates and soil aggregate stability values compared to legume/Kernza intercrops.
- Alternative hypothesis – Legume/Kernza intercrops will have higher levels of soil water infiltration and aggregate stability compared to the Kernza monocultures.
Activities: We are conducting two experiments, one at seven on-farm sites and another at three institutional research stations. We have at least two on-farm and one institutional location in each of the three participating states: Minnesota, Wisconsin, and Kansas.
Experiment 1 is an on-farm comparisons of Kernza grain yield and total biomass yield in various legume/Kernza intercropping systems including: 1) Kernza intercropped with alfalfa, and 2) Kernza intercropped with another perennial legume best fit for the growing conditions of the on-farm participant. A table of participating farmers and the legume intercropping treatments they are testing is in Table 1 below.
Experiment 2 was established at the Rosemount Research and Outreach Center (UMN), the Arlington Agricultural Research Station (UW), and The Land Institute (KS) in September, 2019. Legume intercropping treatments, as well as fertilized and unfertilized monocultures, are listed in Table 1.
Materials and measurement strategies: Stands were established in early September 2019. Establishment was determined in spring 2020 by counting the number of IWG and legume plants along five 25-cm transects aligned parallel with IWG and legume rows. Leaf area index will be determined at the peak of the growing season at five points within each plot using a Li-core 2200. Grain and biomass yield and C and N content will be determined annually using the methods described above.
Net nitrogen mineralization and nitrification rates will be determined at three time intervals during each growing season (spring, summer, and fall of 2020 and 2021) (Robertson et al. 1999). This analysis is to determine when and how much nitrogen legumes contribute to the nitrogen needs of the IWG. Two sets of paired soil cores will be collected from each plot during each time interval. The first core of each pair will be analyzed immediately for nitrate and ammonium using 1 mol L-1 KCl extractions and flow-through colorimetric analysis. The second core of the pair will remain in the soil for four weeks at which time it will be removed and analyzed for nitrate and ammonium. These methods are in accordance with NSF Long-Term Ecological Research network protocols (https://lter.kbs.msu.edu/protocols/35; Mueller et al., 2013)
Soil baseline analysis will be determined using the methods described above for experiment 1. Additionally, soil infiltration, aggregate size, and stability will be measured in spring of year 2 and fall of year 3 of the study using the methods advised by the NRCS (Soil Quality Institute, 2001). For water infiltration, a 15.2 cm-diameter ring is placed in the soil, water is added to the ring to a depth of 2.5 cm, and the time to infiltration of the water into the soil is recorded. For aggregate stability, air-dried soil is passed through a 2 mm sieve, then weighed and placed in a set of sieves, where it is slowly wetted and vertically oscillated for 10 minutes. Aggregate and sand materials remaining on the sieve are dried and weighed, then aggregates are dispersed in Calgon solution and remaining sand is weighed. Percentage of water-stable aggregates is calculated as (aggregates - sand)/(total soil - sand) x 100. We will also measure soil bulk density using the core method (Blake and Hartge, 1986) at the beginning and end of the study in order to express soil C and N on a mass basis.
Data will be analyzed using suitable modern parametric and non-parametric methods based on the distributions they follow. Most response variables will be analyzed by location. When appropriate, location will be treated as a fixed effect and tested alone and as an interaction with treatments to determine if treatments affect soil and yield variables similarly across locations. In response to the American Statistical Association’s recent published statement on the use of P-values (Wasserstein and Lazar, 2016), we will use a combination of confidence and prediction intervals, in conjunction with P-values, to determine statistical significance of our findings. A priori comparisons of yields across treatments will be made using analysis of variance within years.
Establishment of the legumes in the intercropping trials at UMN - Rosemount and UW - Arlington was insufficient to achieve the research goals. The experiment was reestablished at the UMN and UW sites in fall 2020. At Minnesota, IWG was planted on September 3, 2020 at a rate of 10 lbs. pure live seed per acre with 12 inch spacing between rows at the UMN Rosemount Research and Outreach Center. In the “wide” row treatments and intercropping treatments, every other IWG row was terminated to result in a stand with 24 inch spacing between rows. Row termination occurred on October 1, 2020. Legumes were frost seeded on March 12, 2021. Urea fertilizer was applied on April 20, 2021. At Wisconsin, IWG was planted on September 16, 2020 and legumes were frost seeded on 3/17, 2021. Urea fertilizer was applied on May 5, 2021.
Grain yields were measured across treatments at two on-farm sites in Minnesota. Samples are still being processed in the lab to determine total grain yield on a per acre basis. Biomass was also harvested and is being sorted to IWG and legumes. Kurt Kimber harvested grain from his fields. Gary Goplen did not harvest grain but did harvest the field for forage at grain maturity. In WI, John Wepkin harvested both grain and straw in 2020. Grain is currently being stored before cleaning and dehulling. In Kansas, grain yields were calculated from Don Wagner’s field averaged 270 and 218 pounds per acre in the alfalfa and sainfoin intercrops, respectively. Straw yields averaged 2.25 and 2.12 tons per acre in the alfalfa and sainfoin intercrops, respectively.
Updates from 2021 Field Season:
For the first time in this study, we measured nitrogen mineralization rates in the legume intercropping research plots at the research institutions. Nitrogen mineralization rates are a measure of how much nitrogen is made available for plant uptake through the decomposition of soil organic matter. We expect that more nitrogen will be "mineralized" in plots with legumes compared to those without, and that this will have positive effects on Kernza yields. The method requires incubating soil cores in the field for 28 days. We measured nitrogen mineralization rates from three incubations throughout the year - one in spring, summer and fall. These measurements will be collected again in 2022.
Flag leaf tissue samples were collected from the IWG plants at various stages of growth in 2021. These tissue samples will be ground and analyzed for N content. This data will be used to determine N deficit, which will be compared among the intercropping and fertilization treatments. All tissues samples were sent to UMN for grinding in fall of 2021. Grinding and tissue analysis will be conducted in 2022. The procedure will be repeated in 2022.
Collaborators at The Land Institute measured chlorophyl content of IWG leaves in 2021 as a way to estimate nitrogen deficit. The data from these measurements will be compared to the tissue N content data described above. These data will be analyzed to determine if other collaborating sites will collect similar chlorophyl content measurements in 2022.
Grain yields were estimated by harvesting seed heads and threshing the grain from sampled seed heads. Seed heads have been dried and weighed and are in the threshing queue. Legume and IWG biomass was harvested from all plots and separated by species. Weed biomass was also harvested and separated from legumes and IWG. Biomass yields have been measured and entered but analysis has not yet been conducted. This procedure will be repeated in 2022.
Soil samples, grain yields, and IWG and legume biomass yields were collected from the on-farm sites in 2021.
Upcoming field tasks for 2022.
Along with all the data collected mentioned above, the 2022 field season will also focus on soil health measurements. Although the perennial IWG and legume stands are relatively young, it's possible that changes in the physical, chemical, and biological parameters of soil health may have occurred from the start of the study (fall 2020) to the end (fall 2022). We will measure soil infiltration, microbial biomass, and aggregate stability. A final soil sampling will identify any changes in soil P, K, S, N, organic matter, and pH as a result of legume intercropping. These data will be incorporated with the grain yield and legume abundance data to provide a summary of the agronomic and environmental impacts of legume intercropping.
There are no research conclusions at this time.
Farmer-focused outreach and education activities are incorporated into the design of the project. While organizing and logistical support for outreach activities will be led by Green Lands Blue Waters, on-farm field days will be designed and hosted by farmers, targeting Kernza Growers Network participants (additional field days will be held at the research station sites - see Outreach section). Field days will be designed using the SARE Farmer Field Day Toolkit. Educational materials to be produced for outreach events include an updated version of the Kernza Grower Guide and an intercropping fact sheet. While a draft version of a Kernza Grower Guide management document exists for Minnesota, this project will contribute much needed farmer feedback to strengthen the accuracy and on-the-ground utility of the document (the current document is based largely on research station findings and lacks data from on-farm experience). This project will add geographic reach to the document, including management suggestions beyond MN, and will add an important intercropping supplemental fact sheet.
Educational & Outreach Activities
Details to the education and outreach activities can be found in the "Activities" section of this report. We expect to continue with outreach activities in 2020 but using virtual formats in place of in-person events. They may limit the number of activities conducted, but we hope to increase participation for each individual event.
- Production of Kernza
Planted Kernza for production.
A regional Grower's Cooperative formed around Kernza in 2020. Members of this co-op, called the Perennial Promise co-op, include participants in this project's Kernza Growers Network and an on-farm research participant. Some of these participants first met and were introduced to Kernza from SARE project activities, which highlights the critical role these projects play in network building.
2021 Update: The Kernza Growers Cooperative officially filed as an organization call the "Perennial Promise Growers Cooperative". Information about the organization can be found here. One of the on-farm partners on this project is a due-paying member and actively involved with development and management of the coop.
PI Jungers initiated a new multi-site Kernza legume intercropping trial with a group of researchers in Eastern US focused on organic production that was designed using experiences learned from this study. A second new legume intercropping trial was established among this current set of research partners as part of the USDA Sustainable Agricultural Systems KernzaCAP grant; again using information learned from this study.