Perennial flax: a new crop for sustainable agriculture in the Northern Plains.
North Dakota and the surrounding North Central region are frequently plagued by excessive soil moisture, often causing inability to sow or harvest key crops during both spring and fall. These challenging conditions are often interspersed with seasonal drought. Growing perennial crops can help overcome these problems by improving in-season soil water infiltration/storage (thereby increasing crop-useable soil-water content), reducing offseason runoff (preventing soil erosion and associated nutrient loss), diversifying harvesting windows, and using a larger portion of the growing season. Perennial crops also foster increased soil carbon storage, healthy soil microbe communities, efficient nutrient cycles, and increased habitat for pollinators. For all these reasons, growing perennial flax will contribute to environmental sustainability. Additionally, many farmers lack profitable crop options for increasing rotation diversity and spreading risk. Perennial grain crops, such as Kernza®, have been successfully developed, but a high value perennial oilseed crop could also be beneficial for this region because of the availability of market centers for oilseed crops and growing consumer demand for such products. Moreover, perennial flax species (i.e., Linum lewisii) have the oil quality of annual flax (high in heart-healthy omega-3 oils) and are true perennials that regrow from winterhardy crowns and can be harvested up to two times a year in North Dakota. Consequently, perennial flaxseed is a high-value oilseed crop with the environmental benefits of perennials that could help foster both economic sustainability for farmers via increased profitability and social sustainability via contributions to producer work-time management and public health. We propose a series of agronomy and plant breeding experiments aimed at developing the informational and germplasm basis for perennial flax as a new oilseed crop for the North Central region. Our proposed outputs are outreach to producers on basic agronomic recommendations (including tactics for weed suppression) for this potential new perennial crop, and to provide information on existing public flax accessions and improved lines derived from public pre-variety resources, leading to a better crop for both organic and conventional producers. This project will also link potential first-adopter perennial flax producers with interested food industry partners to begin supply chain development (see attached letters of support from industry partners).
Three learning outcomes are (1) changes in awareness and knowledge among regional farmers about how perennial oilseed production can functionally diversify their operations, (2) graduate student education in sustainable agriculture, particularly agronomy, participatory plant breeding, and associated outreach, and (3) changes in undergraduate student awareness and knowledge of agricultural and food systems through a student internship exchange program. An action outcome includes linking our breeding program with producer and end-market support. The longer-term, system-wide goal is to assemble a supply chain that starts with producers and plant varieties and ends with food industry demand and consumer availability.
- Perennial crops may enhance cropping system sustainability, as well as improving aspects of soil health, e.g., organic matter.
- Highly variable soil moisture often prevents timely planting and harvesting in annual cropping systems – perennials add operational FLEXIBILITY for farmers.
- Established markets for flaxseed and flax oil ensure reliable crop value for farmers, making PERENNIAL FLAX (Linum lewisii) an ideal perennial crop to diversify north central Great Plains cropping systems.
- Therefore, our goal was to investigate agronomic best practices for planting and establishing productive perennial flax stands.
We hypothesize that agronomic approaches can be developed to facilitate growing perennial flax (Linum lewisii) as a perennial crop, and that evaluation of perennial flax germplasm will lead to identification of genotypes best suited for agronomic production in the northern Great Plains.
Objective 1: Agronomic recommendations for sowing, stand establishment and weed control.
Although perennial flax has been grown on seed production farms to increase seeds for revegetation and reclamation purposes, little is known about ideal management strategies to cultivate it as a grain crop. Our approach to augmenting existing information on agronomic management is predicated, first, on the fact that no herbicides are currently labelled for use on perennial flax species because of their limited agricultural use, and second, that an oilseed production use would open up a number of organic-inspired approaches that would not be appropriate management practices for certified seed production, such as nurse crops.
Two agronomy experiments will be conducted on perennial flax at organic farms in two locations. The first location, Comstock, MN, in the Red River Valley near the city of Fargo, was chosen because of the proximity to a moderately sized urban center with specialty agriculture presence, which is also within a few hours of the large population center of Minneapolis with more market options. The second is Carrington, ND, home of the Carrington Research and Extension Center of NDSU, a hub of research on specialty crops and an extension center with many well-attended research and stakeholder outreach events. The Carrington site also employs Steve Zwinger, who will also work with us in his private capacity as an organic farmer in the same area. Indeed, people with Steve’s diverse experience and skill set are hard to come by, and we are fortunate to work with an expert and a practitioner.
In addition to our resident technical experts and producer partners on this project, we plan to have a student learning component as well. A graduate student at NDSU will use Experiments 1 and 2 as a training project for their research assistantship, and will also participate in the germplasm evaluation research in Objective 2. Further, we currently have an exchange program through Dr. Hulke’s lab with University of Colorado-Boulder, in which 2 or more exceptional ecology and evolutionary biology students spend a summer in Fargo learning about agronomy and plant breeding research through hands-on participation. The intent of the program is to educate students about agriculture that have had little exposure to it previously.
At each of the two locations, we will conduct two trials, both arranged in a randomized, complete block design with four replications per location. All plots will be seeded to the Linum lewisii pre-variety ‘Maple Grove’. The first field study will evaluate planting date, row spacing, and seeding density. The second study will evaluate various weed management tactics assembled into four distinct systems, which comprise rational, ecological approaches. These experiments will facilitate development of basic agronomic management principles for perennial flax when grown for oilseed and edible whole seed purposes.
Experiment 1: Each plot will be 10’ x 20’ with a 20’ alley between ranges of plots to allow for equipment maneuvers. No additional space will be placed between adjacent plots in the same range. An annual nurse crop [oats and field peas] will be planted simultaneously with the flax at plot establishment to enhance flax establishment and provide competition against weeds. Some combination of tillage, hand-weeding, and mowing may be used throughout the experiments to manage weeds, and will be documented. Each entire plot will be harvested for yield estimation at each harvest date. The first experiment will include the following treatments in a factorial design:
- Planting date
- August 15-Sept 1 of 2019
- early spring 2020, as soon as possible
- Seeding density
- 363,000 PLS/A [1x seed production rate]
- 726,000 PLS/A [2x seed production rate]
- 1,452,000 PLS/A [4x seed production rate]
- Row spacing
- 30” corn planter
- 6” solid seed grain drill
Days to canopy closure, days to bloom, and plant height and lodging at 25% maturity will be assessed before each harvest. When plots reach 25% of the seed bolls turning brown, a crop plant census will be taken on a randomly chosen 1 m2 area in the center of each plot. Following the census data collection, each plot will be cut and left to dry in a windrow. The windrow will be taken up by a small plot combine with pickup header when dry, and seed yield determined by the weight of the harvested seeds. A small subsample will be taken for oil content analysis. Oil analysis will be conducted with a nuclear magnetic resonance instrument (NMR), which determines oil content non-destructively. The NMR will be calibrated using a set of samples pre-selected for their variation in oil content as determined by a destructive, wet chemistry method (AOAC method 2003.05)
Experiment 2: Each plot will be 10’ x 20’ with a 20’ alley between ranges of plots to allow for equipment maneuvers. No additional space will be placed between adjacent plots in the same range. The experimental design will be a randomized complete block with four replications. The experimental treatments will be four weed management systems, conceptualized as pairwise combinations of high/low diversity and high/low disturbance (detailed in Table 1). Flax will be harvested as discussed above to determine crop yield and quality. Weed emergence will be assessed at peak emergence, and weed biomass will be measured destructively at peak vegetative growth. At the beginning and end of the last field season associated with the project, we will sample soils cores from each plot to determine the effect of each weed management system on soil nutrients (N-P-K).
Objective 2: Enhance our perennial flax breeding program by learning from producer experiences in participatory, on-farm trials
Until recently, only a limited amount of Adenolinum perennial flax has been available through public germplasm banks. Additional germplasm resources recently obtained through private collections and additional exploration are uncharacterized. At the same time, producers have only had limited opportunity to see the variation in perennial flax, and their perceptions of various plant characteristics with respect to forming useful plant varieties is extremely valuable to our efforts. Thus, the purpose of this work is to better document available variation in perennial flax accessions of the Section Adenolinum, particularly L. lewisii, with producer involvement and under producer conditions. The accessions that will be evaluated include our pre-breeding lines (focused on rapid seed germination and seedling survival under unprotected winter conditions in North Dakota), wild collections from the Black Hills of SD and Boulder County, CO; new accessions from the USDA-National Plant Germplasm System; and pre-variety germplasm, including ‘Maple Grove’. This work will be split into two experiments, Experiment 3 to characterize our newly broadened accession base for traits of interest over the 3-year timespan of the grant, and Experiment 4 to conduct self-pollination and purification of lines from Experiment 3 accessions that have superior characteristics to ‘Maple Grove.’
Experiment 3: We will evaluate about 100 pre-release and wild germplasms on-farm in a randomized, complete block design with three replications. Plots will be seeded between August 15-September 1, 2019, and maintained using mechanical tillage and hand weeding to keep as homogeneous an environment as possible and reduce competition effects that can mask genetic potential. Individual plots will be one row, 7’ in length, with 30” row spacing. Plots will be evaluated at both locations for stand persistence (crop plant counts), plant habit (numeric score of prostrate to upright), height at 25% maturity, general plant-to-plant phenotypic uniformity, lodging, yield, and oil content, as described above. At Comstock only, we will conduct additional notes and studies that require daily monitoring. These additional notes include: days to start of bloom (from April 30), synchronicity of bloom (number of days in bloom), and days to 30” spread (canopy). Additionally, at Comstock, five plants in the third replication will have a few branches covered by insect exclusion bags to exclude pollinators at bloom, and the seeds from under bags harvested separately to assess self-seed set, to provide seeds for oil compositional analysis, and to use for Experiment 4. Self-seed set can be determined by counting the number of seeds formed under bags (numerator term), counting the number of bolls formed under the bag and multiplying by 10 (denominator term), and forming the ratio. Oil composition will be conducted using routine gas chromatography protocols.
Experiment 4: After the first harvest of Experiment 3, the self-pollinated seeds obtained from each plant will be placed on germination paper and the fastest germinating seedling from each removed and placed in a 2” square pot. The plants will be grown in the greenhouse in an insect-free environment, and at bloom, will be allowed to self-pollinate. Bolls will be harvested, and the greenhouse process repeated. This process is known to breeders as single seed descent, and it is used to rapidly purify a large number of lineages in a small amount of space. During this time, yield and agronomic quality data on Experiment 3 will be obtained, and the top 10% of the lineages in Experiment 3 will be advanced in Experiment 4 (~100 lines x 10% = 10 lines x 5 single seed descent advancements = 50 F5 lines). These F5 lines will be sown in an experimental design similar to Experiment 3 above, near the end of year 2 (fall 2021) of the grant on NDSU campus in Fargo or, more desirably, on the Askegaard farm if the producer wishes to maintain involvement beyond the grant period. During the summer of 2022, we will continue to assess Experiment 3 for long term yield and stand quality, remove from breeding consideration any accession lineages that are not superior to ‘Maple Grove’ or other accessions by assessment of the traits under measure. At the end of the grant period, fall 2022, we expect to have the first season of yield assessment complete on the F5 lines, which will guide which lines are to have seeds increased through self-pollination under insect exclusion bagging and/or insect exclusion cages to produce F6 breeder’s seed or conduct further advancement, if necessary, beyond the grant. These cage increases can provide seed for replicated testing, food science research, and other evaluations in the future, which are better informed due to the agronomy work in Experiments 1 and 2.
Objective 1: Agronomic recommendations for sowing, stand establishment and weed control.
Sowing of perennial flax (Linum lewisii) experiments 1 and 2 was planned in the fall of 2019, prior to the start of the grant funding, but was prevented by persistent wet conditions in August and September that not only prevented planting of fall plots, but also prevented producer harvest of spring wheat (Triticum aestivum), resulting in loss of many fields due to pre-harvest sprouting and decay in the wheat crop.
Sowing of experiments 1 and 2 was attempted in May of 2020 with success. Our Comstock, MN, location was planted May 27 and Carrington, ND, was planted May 29. Approximately 2 weeks after planting, as flax seedlings were emerging (Figure 1), a thunderstorm with heavy rain caused soil movement that buried newly emerged seedlings at our Comstock site, resulting in nearly complete loss of stand. Slow emergence of the seed was not due to seed-related low vigor, as the seeds uniformly and quickly germinated in the laboratory. Rather, the species seems to emerge slowly in the field, for reasons that need to be investigated, but could include a “conservative” approach that focuses on root development and access to moisture before emerging. The Carrington site planting received inadequate rainfall after planting, which resulted in poor development of the flax and many of the weed management companion crops. However, the oat and field pea mixture for Experiment 1 did emerge nicely and provide some control of crop mimic weeds (common lambsquarters and Amaranthus spp.) that showed up later when rains arrived. Later emergence of perennial flax, with these rains, resulted in a poor-to-fair stands, which are still being maintained by mowing of the weeds and oat-pea cover, because we observed that the perennial flax was somewhat content with having fast growing annual cover, as long as it was not too dense (Figure 2). The reason we are maintaining these plots is to see the outcome of this management approach in year 2.
The Comstock, MN, site was replanted for both Experiment 1 and Experiment 2 on June 24. During the following 2 week period, another heavy rain event occurred and resulted in washing/crusting of soil, which resulted in almost no plant stand for both the perennial flax and also many of the intercrops in Experiment 2. Sowing depth was between 0.5 and 0.75 inches deep for all the plantings to this point. We hypothesized that sowing depth, combined with poor soil conditions due to crusting, was preventing stand establishment, and that, perhaps, having a nurse crop in the same planting furrow may help emergence when crusts develop. We decided to investigate this further with another experiment at Prosper, ND (near Fargo), which we planted on August 6, 2020. The study design incorporated a factorial combination of the following treatments: 4 seeding densities of perennial flax (2x, 4x, 6x, and 8x the seed production rate on the NRCS guide sheet), 4 intercrops (none, annual flax, natto soybean, and hard red spring wheat), and 5 planting treatments (surface-no packing, surface-packed, 1/3″ deep, 2/3″ deep, and 1″ deep). In addition, half of each plot was left to heavy precipitation, which occurred naturally, while the other half had the soil loosened slightly after crusting with a Garden Weasel. This was an unreplicated preliminary experiment to determine if any of the treatments would show any signs of efficacy. The only treatments to result in more than a few seedlings emerging were the surface-seeded plots (both packed and unpacked; Figure 3; Table 2). There was no benefit of intercropping in-furrow for any of the depth treatments. The conclusion we reached is that perennial flax, in its current form, is very susceptible to heavy rain events that have become common from spring through summer in the Northern Plains region. This is, however, a logical target for plant breeding to solve.
|Table 2. Surface seed with crusting / decrusted after rain (counted 9/2/20)|
|# of seeds planted|
|Treat||100 (2x)||200 (4x)||300 (6x)||400 (8x)|
|No pack/no weasel||6||36||45||39|
Our fall planting of Experiment 1 was conducted on September 5, 2020, after the spring wheat harvest window. Although not seeded into spring wheat, we simulated what this planting window would be like in order to understand winter survival issues, if they arise. Learning from previous experiments, we reduced the seed depth to 1/8-1/4″ deep and planted oats as nurse crop perpendicular to the direction of planting of the perennial flax (as was planned in the proposal). Rates of seeding were also increased to 4x and 6x, instead of the 1x, 2x, and 4x seed production rates initially proposed. As heavy rainfall is not typical in fall, and did not occur, we had excellent emergence and stand establishment. Consistent with observations in Carrington, the perennial flax tolerated the oat cover well, and the oat established well enough to provide a “snow catch” to maintain winter cover (Figure 4). Experiment 1 was only planted at Comstock, MN, for fall sowing date because Carrington, ND, was still too droughty for emergence of shallow-seeded crops. Because of the lack of success of spring/summer planting, due to commonly experienced heavy rain events, we added a treatment of “dormant seeding,” which was planted at Comstock November 5, 2020, and at Absaraka, ND (in lieu of Carrington because of COVID related travel restrictions) on November 6, 2020. This followed the methodology originally outlined for Experiment 1, except planting depth was 1/8-1/4″, planted into fall-planted oat companion crop, at 4x and 6x seed production recommended rate. The soil was cold at both sites at the time of planting, and prior to the first persistent snowfall, both fields were confirmed to have no sprouted seeds.
Experiment 2 was not planted at either site this fall because our previous results suggested that perennial intercrops, too, were detrimentally affected by soil conditions, and were often too slow to provide meaningful protection from crop mimic weeds. Although we are still watching the effects of annual intercrops (the pea + oat combination in Experiment 1 at Carrington, ND), which may still provide results that are useful for production of perennial flax, we also hypothesized that organic-friendly flame weeding may be effective for weed control when the plants are very small, during establishment, and perhaps between cuttings when mature. This alternative approach is being tested in the field and greenhouse. In the field, we dormant seeded 4 replications of 7 — 10′ x 20′ plots with 4x seed production rate of perennial flax, on 30″ rows. The plots were planted at Comstock, MN, and Absaraka, ND, which are contrasting soil environments somewhat near Fargo because of Covid-related travel restrictions. Both are organic sites with moderate weed seed bank. These plots will be assigned flame weeding treatments including different timings, dosages, and presence of thermal shielding. Beyond the field trial, we have already attempted flame weeding treatments on plants in the greenhouse. A broadcast flaming treatment was applied that made equal contact with the perennial flax and problem weeds Kochia and wild Proso millet (Figure 5). Preliminary results indicated that the weeds were negatively affected by flaming, even at low rates, while the perennial flax seems to thrive under these conditions. This may be an evolved mechanism, as we find the best collection zones in the wild for perennial flax are in recently burned western forestland. For this reason, we feel that this is a proper new path to pivot towards.
Objective 2: Enhance our perennial flax breeding program by learning from producer experiences in participatory, on-farm trials
As a result of weather and Covid-related limitations to the research, we have condensed Experiment 3 and 4 into a common experiment. As stated previously, we had planned to conduct a fall nursery planting of perennial flax in 2019, but weather conditions that resulted in delays for our farmer-cooperator led us to abandon those plans in favor of starting greenhouse plants for Experiment 4 — development of inbred progenies for breeding and evaluation. During the greenhouse work, in March of 2020, our efforts ran into two issues, the development of the Covid pandemic and the diagnosis of the breeding research specialist (funded in part by this grant) with cancer. The research specialist took a leave of absence while obtaining treatment (which was successful and he is returning to work now). In order to work through these issues, we went from a full plot evaluation approach to a spaced plant evaluation that also included production of self pollinations and crosses, essentially combining the objectives (Figure 6). We also developed a working relationship with Noreen Thomas, a farmer that is closer to Fargo, which allowed us to do more of the breeding work with less travel, and this allowed us to more easily be Covid-protocol compliant. Data is currently being analyzed from our summer’s work, but indicate a wide variety in seed morphology, plant height, growth habit, flowering time and duration, and vigor among the 103 accessions that were evaluated. Progeny of these accessions are being grown in the greenhouse to continue the work of self-pollination to make uniform lines from these accessions for later release.
Figure 6. (L) Spaced plant nursery of perennial flax shortly after transplanting of seedlings. This was conducted on Doubting Thomas Farms, with participating farmer Noreen Thomas. (R) Brent Hulke and Noreen Thomas posing with a “picture frame” that we plan to set out in the field next year for visitors to take photos with the blooming perennial flax nursery.
During these conditions that have limited our onsite work activities late last winter and early spring, we learned of work that was unpublished by Tom Jones, USDA-ARS, Logan, UT, and Stan Kitchen, USDA-NRCS, Ephraim, UT. They have collected wild perennial flax from the intermountain west and evaluated it for traits of interest for disturbance restoration plantings. These data were used to release the ‘Maple Grove’ variety, but were unpublished. Andre Gossweiler, a graduate student on this project, and Peter Innes, a graduate student of a collaborator at University of Colorado-Boulder, have been analyzing these data and preparing them for publication. Andre is also adding to the dataset by collecting information that is of agronomic and end-user interest, namely, oil content and composition of the samples from the common garden experiment. We expect this manuscript to be submitted in late March.
Outreach: While Covid has certainly limited the opportunities for outreach, our new partnership with Noreen Thomas has been helpful for informing the public about our work, through her great network and her abilities as an educator. Noreen had many visitors to her farm, even during Covid, and has facilitated tours of our perennial flax nursery with researchers from the University of Minnesota and elsewhere, other farmers, interested members of the public, and even a virtual tour with New York City chef Dan Barber, which is turning into a new collaboration on the food aspects of perennial flax. In addition, although short-handed because of Covid and other health crises in our group, we have been able to produce two YouTube videos on perennial flax, one within our group and one with the assistance of NDSU extension. Some of our preliminary results were shared at the virtual American Society of Agronomy annual meeting in November 2020. As the plots mature and Covid issues are reduced, we plan to have additional tours at the four sites at which we are currently growing perennial flax.
Two M.S. students are involved with this project, Zachary Pull and André Gossweiler. These students are participating in all project experiments, and will prepare thesis documents to report the results.
Educational & Outreach Activities
We had planned to present preliminary results at two NDSU field days, but both field days were cancelled because of the pandemic. Instead, the field days were held via YouTube. We presented our preliminary results via poster at one professional meeting that was held virtually, the 2020 ASA-CSSA-SSSA International Annual Meeting. Other outreach included an additional YouTube video we produced, information found on our lab website (hulkelab.org), a popular press article, and personal visits to plots of 180 consumers, 5 interested scientists from outside of the collaboration, 4 extension staff educators, 3 politicians (including Sen. Tina Smith’s staff), and 1 chef / food advocate from New York City, who toured via zoom conference in the field, in addition to consulting with us thereafter.
A peer-reviewed journal article on the phenotypic diversity of Linum lewisii is in draft, expected to be submitted to a journal next month.
- knowledge of perennials as a new crop opportunity in the region.