Location: Forage Seed and Cereal Research Unit
2022 Annual Report
Objectives
Objective 1. Assemble and integrate current hemp related data and collect new data in collaboration with University partners to establish and improve hemp production modeling efforts.
Objective 2. Develop modeling techniques that incorporate existing and newly generated hemp agronomic information into decision support tools to help farmers integrate hemp production into existing farm systems.
Approach
Industrial hemp is a potentially useful crop for production within the U.S. Various properties and uses for hemp are being explored, some focused on the unique properties of the plant itself (fiber production, protein content as livestock feed), and some focused on the properties of cannabidiol (CBD) for a variety of uses. The goal of this research will be to use existing agronomic information and generate new information, then use modeling techniques to incorporate that information into decision support tools to help farmers integrate hemp production into existing farm systems.
Progress Report
New crops can cause unexpected challenges in pest management for growers of the new crop and those producing related crops nearby. Industrial hemp and its incorporation into Pacific Northwest (PNW) cropping systems poses such challenges to hemp and surrounding cropping systems. To expand our understanding of the pests and diseases affecting hemp, ARS researchers in Corvallis, Oregon, initiated a regional survey. This research is in support of Sub-objective 1A. Through survey efforts in 2021, we identified several critical hemp diseases that have implications for PNW cropping systems. A major disease of concern is powdery mildew, since it can infect both hemp and hop, which are both grown in the PNW. We detected powdery mildew late (August-September) in the 2021 season near hop production fields. Studies comparing the genetics of the powdery mildew species affecting both hop and hemp are underway, as well as efforts to screen hemp germplasm for resistance to this pathogen, and to understand the interplay between a hemp infection near hop yards and vice versa.
A second disease of concern is Curly Top caused by beet curly top virus (BCTV), which is transmitted by beet leafhoppers. This virus has an extremely broad host range of over 300 host crops and weedy hosts. We detected the virus causing symptoms in hemp in 2021, though symptom expression and intensity varied by host genotype and virus strain. Further studies into the genetic variation amongst virus strains affecting hemp, germplasm screening for potential tolerance to the virus, and an evaluation of landscape factors like weed diversity and nearby crop hosts on virus incidence and severity in hemp are in development. A greater understanding of how important hemp is for creating new sources of virus for leafhoppers to transmit throughout the region is critical to the overall health of the PNW cropping system.
In addition to pathogens, we are surveying for nematodes in industrial hemp fields. Plant-parasitic nematodes (PPN) are a challenge to control in most other cropping systems and there has been some prior research indicating that planting hemp can reduce populations of PPN. Our surveys throughout the growing season will allow us to evaluate how populations of PPN change over time while hemp is in production and will provide insight into any significant PPN that affect hemp. Further research into how hemp can be incorporated into cropping rotations to impact PPN populations are underway. Other soilborne pathogens like Fusarium spp., Rhizoctonia spp. and Sclerotinia spp., are also of concern to the hemp cropping system since they can reduce yield in both hemp and rotation crops. The interaction between hemp, soilborne pathogens, and nematodes can have further implications for disease severity. These interactions of the soil disease system as a whole are a target for future research using microplot and greenhouse-based studies.
In support of Sub-objective 1A, a nation-wide network of cooperators organized by Oregon State University conducted a uniform cultivar trial of chemical-type hemp varieties resulting in 27 site-years of data. General observations were made determining the suitability of these genetic materials grown under production conditions typical of the regions. Establishment systems leading towards commodity production were used and evaluated for continued suitability. Local climatic/weather, edaphic, disease, insect, and weed stressors were assessed.
Irrigation research testing varying levels of irrigation were conducted in 2020 and in 2021 by Oregon State University collaborators. This work was conducted in support of Sub-objective 1A. Irrigation treatment levels were based on replacing percentages of estimated evapotranspiration (ETc) based on a weather station ET multiplied by an estimated crop coefficient, with irrigation treatment amounts estimated to range from a severe deficit to full ETc. Commercial photoperiod-sensitive and photoperiod-insensitive varieties were grown in each year at all locations. The crop water requirement for chemical-type hemp was greatly impacted by hemp growth form, partly due to size of plants and ground cover and crop time to maturity. This research suggests that optimal irrigation recommendations will depend on: 1) flower yield response to irrigation, 2) cannabinoid flower content response to irrigation, and 3) indirectly on the efficiency of cannabinoid extraction as a function of flower cannabinoid content.
In support of Sub-objective 1A, field research was conducted by Oregon State University to determine the optimal sampling time and inflorescence location in the plant canopy on cannabinoid profile. Results indicate that cannabinoid concentrations increased rapidly at the onset of flowering, and then leveled off as the plants matured. Previously used methods, such as the coloration of trichomes, may be an indicator of maturity. But the progression of color change in trichomes appears to differ among varieties, making a universal trichome-based maturity indicator unlikely. Plant-to-plant results revealed samples ranging from exceeding the 0.3% Tetrahydrocannabinol (THC) threshold by 60% to under the threshold by 60%. This indicates that single-inflorescence or single-plant sampling protocols used to measure average THC content (or Cannabidiol, CBD) are likely to result in unacceptable and inaccurate results, regardless of field size, and it is necessary to examine multiple samples.
In support of Sub-objective 1B, Oregon State University collaborators used Oregon Department of Agriculture data on 2017-2021 registered hemp acres to determine where different kinds of hemp production were grown and what changes occurred through time. Economic analyses were conducted using custom enterprise budgets, secondary data from other states, and published hemp yields, costs data, and USDA Ag Census data. Hemp has been grown in all the main agricultural production regions of Oregon, at various scales including most small-scale cannabinoid production is in the Willamette Valley, but also some larger fields mostly east of the Cascade Mountains in the Columbia River watershed, Central and Southern Oregon, and the Eastern Oregon Ontario area. As seen nationwide, there was a great increase in production in 2019 followed by great decreases in following years. Preliminary results of economic analyses of yield and management improvements for hemp fiber production indicate trade will play an important role in determining impacts. Without inter-state or international trade, higher productivity will drive down prices and limit producer adoption of hemp crops and beneficial hemp production technologies.
Accomplishments
Review Publications
Rivedal, H.M., Funke, C.N., Frost, K.E. 2022. An overview of pathogens associated with biotic stresses in hemp crops in Oregon, 2019-2020. Plant Disease. 106(5):1334-1340. https://doi.org/10.1094/PDIS-11-21-2415-SR.
Thomas, W.J., Borland, T.G., Bergl, D.D., Claassen, B.J., Flodquist, T.A., Montgomery, A.S., Rivedal, H.M., Woodhall, J., Ocamb, C.M., Gent, D.H. 2022. A quantitative PCR assay for detection and quantification of Fusarium sambucinum. Plant Disease. 106:2601-2606. https://doi.org/10.1094/PDIS-02-22-0269-RE.
