Location: Forage Seed and Cereal Research Unit
2021 Annual Report
Objectives
The long-term aim of this project is to address strategic, high priority needs of grass seed growers in the Pacific Northwest (PNW) by assessing and developing management practices that simultaneously improve crop productivity and advance soil health. This aim will be met by interrogating research questions that fall into two broad objectives. The first objective is primarily focused on improving crop production by lessening the overall impact of pests, weeds, and pathogens, improving the arability of marginal lands with novel soil amendments, and assessing the impacts of management practices on soil health and fertility. Objective 2 also aims to improve crop productivity by identifying key interactions between genetics, environment, and management (G x E x M). Within this objective, tradeoffs between intensifying production and advancing ecosystem services are quantified and better understood to help farms reach and sustain their potential, including the impact of crop rotation and other management practices on increasing populations of beneficial microbes and improving soil health. Collectively, Objectives 1 and 2 advance our understanding of how G x E x M interactions impact agroecosystem productivity and resilience. For Objective 3, these data will be synthesized and developed into decision-support tools and models to provide growers with concrete strategies for improved land management and cultivation of grass seed cropping systems.
Objective 1: Identify and evaluate management practices that improve crop productivity and crop health or that enhance environmental quality.
- Sub-objective 1A: Identify technologies to reduce priority pests, diseases, and weeds that limit the profitability and sustainability of the cropping system.
- Sub-objective 1B: Assess the environmental and production outcomes from the application of biochar on marginal soils.
- Sub-objective 1C: Determine the effectiveness of crop rotation in reducing populations of weeds, diseases, and invertebrate pests.
Objective 2: Identify and assess key interactions between cropping system, environmental conditions and management practices that influence cropping outcomes and agroecosystem productivity.
- Sub-objective 2A: Evaluate the impact of management practices, including crop rotation, on soil health parameters.
- Sub-objective 2B: Assess the impact of cruciferous crop rotations on plant growth and microbiomes.
Objective 3: Develop knowledge and decision support tools that enable growers to optimize production.
- Sub-objective 3A: Develop and expand decision support tools that provide information about biochar to growers.
- Sub-objective 3B: Develop models and decision aids that improve soil health and improve system productivity by decreasing the yield gap.
- Sub-objective 3C: Develop strategies to reduce priority pests, diseases, and weeds and improve soil health.
Approach
The overall hypothesis of the project is that improved cropping practices in grass seed cropping systems provides simultaneous benefits to soil health and crop productivity. This hypothesis is tested within three objectives and their related subobjectives. In Objective One, we explore methods to reduce the populations of weeds and pests that limit productivity. This research is conducted in laboratory, greenhouse, and field experiments that determine if practices that promote soil health and lessen environmental impacts (application of soil amendments, selective herbicide application, and precision weed management) are detrimental or beneficial to crop yield. In Objective Two, the research aims to determine if conservation practices (cover cropping and reduced tillage) improve soil health, and if soil health can be attributed to improvements in crop yield. These objectives are met with laboratory, greenhouse, and field experiments that assess soil health and identify allelopathic responses mitigated by cover crops. The aim of Objective Three is to synthesize the information gathered in Objectives One and Two, and to create decision support tools that enable growers to optimize production. These tools will be provided to growers as web-based tool kits, models, or agronomic measures used to control pests, pathogens, and weeds, and to apply soil amendments. In general, these approaches aim to identify key interactions between genetics, environment, and management that simultaneously reduce farm inputs and improve ecosystem services by identifying and quantifying tradeoffs.
Progress Report
Aphid-transmitted viruses are widespread in Oregon’s grass seed production systems and have been associated with crop damage and reduced yield. In support of Sub-objectives 1A and 3C, regional and statewide monitoring efforts were initiated to investigate the composition and spatiotemporal distribution of the aphid and barley/cereal yellow dwarf virus complex, Cocksfoot mottle virus, and other viruses in grass grown for seed. Understanding the spatial and genetic diversity of this virus-vector complex will inform concurrent applied research investigating interactions between aphid species, virus strains, crop damage symptomology, and crop yield potential. Prediction modeling and complementary datasets of significant abiotic and biotic factors will be used in combination with field survey data to identify ‘high-risk’ areas of aphid and associated disease outbreaks in grass seed production systems.
Economically damaging noctuid (armyworm/cutworm) pest outbreaks in grass crops grown for seed production is a critical issue facing the grass seed industry. In support of Sub-objectives 1A and 3C, regional and statewide monitoring efforts have been initiated incorporating current and archived data to determine the spatiotemporal distribution and ecology of these economically important pests. Environmental risk factors are being investigated using geographic information system (GIS) and geospatial predictive modeling to understand local and regional drivers of noctuid pests in grass seed systems. Furthermore, university collaborations have been established to develop automated moth traps that send real-time data to a cloud computing service for data visualization that can be shared with stakeholders. These traps are economical, easy to use, and will be an excellent monitoring tool for researchers and grass seed producers. Expected outcomes are: 1) phenological models and timing of moth and larval activity; 2) landscape and management risk factors and prediction models; 3) validation of automated trap network capturing real-time data to deploy in areawide monitoring; 4) survey of natural biological control agents; and 5) understanding genetic variability and migration patterns of important noctuid pests.
Carbon seeding is a weed management practice that allows producers to establish crops by applying a narrow band of activated carbon (AC) directly over the seed furrow, followed by treatment with a broadcast preemergent herbicide. The AC provides crop safety by absorbing the herbicide, essentially deactivating it within the planting row. While this method is effective, the combined cost of the AC and the herbicide limits its feasibility. In support of Sub-objective 1A, we tested the efficacy of three biochars (barley, juniper, and a mixed-conifer biochar) as a replacement for AC to absorb three herbicides used in carbon banding practices [diuron, indaziflam (Alion), and a mixture of flumioxazin + pyroxasulfone (Fierce)]. Greenhouse experiments suggested that the ability of biochar to bind herbicides is driven by feedstock origin, production conditions, and the chemical properties of the herbicide. In all cases, the mixed conifer biochar provided crop safety equivalent to that provided by AC, while the crop safety provided by barley and juniper-origin biochars varied. Field trials will determine if biochar can be a low-cost replacement for AC under normal environmental conditions.
In support of Sub-objective 1A, field experiments were initiated to determine if precision weed management with marginally selective herbicides will improve seed yield of perennial grasses grown for seed. Plants of the weed, roughstalk bluegrass, were counted and images were taken in three field experiments. Images were taken to assess the competition of roughstalk bluegrass in spring planted tall fescue and to determine the injury caused by glufosinate in tall fescue at different application timings.
Pyroligneous acid (PA) is a byproduct of biochar production that has the potential to control soil-borne phytopathogenic fungi. Progress under Sub-objective 1B confirmed that PA is fungicidal towards Verticillium dahliae at very low concentrations in artificial soils; however, in field soils, we noted that high PA application rates were phytotoxic. In greenhouse experiments, mint plants were exposed to a range of PA application rates, both preplant and during growth. During growth, PA caused the pH of the soil to decrease beyond the optimum range. However, we determined that phytotoxicity could be mitigated if the soil was watered between the time of treatment and the time of planting. To optimize the timing of PA application, we conducted greenhouse trials to test the hypothesis that PA can control Verticillium Wilt under a controlled setting. To support that effort, we developed droplet digital polymerase chain reaction (DDPCR) assays to accurately measure inoculum loads in infested soils. V. dahliae specific primers were co-opted from previous work using quantitative PCR methods. By switching to a DDPCR method, we can detect V. dahliae at a very low inoculum density without interference from PCR inhibitors. Efforts to expand this methodology to other pathogens are now underway.
Biochar, a carbon-rich by-product of energy production, has received growing attention as a soil amendment that can improve soil structure, increase yield, and sequester carbon. These impacts are especially evident on marginal soils, including abandoned mine sites and metal-impacted agricultural soils. Progress under Sub-objective 1B determined that biochar aids in the phytostabilization of mine soils. To test this, we established field trails at the Formosa Mine in southern Oregon using various mixtures of lime and biosolids with or without the addition of fertilizer, biochar, or locally sourced microbial inoculum (LSM). In collaboration with the EPA, field plots were tilled, amended, and planted with six species of native plants. Preliminary data suggest that native plants are unable to establish in unamended mine soils and that native grasses grow larger when inoculated with LSM. We expect that this field trial will continue for several years; as such, handheld Light Detection and Ranging (LiDAR) methods are being developed to assess biomass without the need for destructive sampling.
As legislative action to regulate carbon (C) use in Oregon looms, there is a need to quantify the amount of C stored in crop production systems. Perennial grass seed crops have the potential to accumulate C due to the lack of repeated tillage; however, a full accounting of C stocks in these systems is lacking. Progress under Sub-objective 2A quantified the C storage potential of perennial grass seed crops grown in the Willamette Valley, Oregon. We hypothesized that C accumulates over time due to the lack of tillage and full straw chop-back management (flailing). To investigate this, 12 flailed fields were paired with 12 baled fields, where management was consistent for at least 75% of the stand years. Intact soil cores (85-100cm) were collected using an all-terrain vehicle-mounted hydraulic probe to estimate bulk density and soil C. Above and belowground biomass was collected to assess total plant C. Plant cover was used to estimate total root and aboveground biomass C in the field. Ongoing analysis of these samples will determine the C balance in grass seed fields to determine if there is a potential for net carbon storage.
In support of Sub-objective 2A, greenhouse studies were initiated to understand the effects of conservation tillage practices on soil health indicators and to understand if improvements in soil health increase yield. We hypothesized that plant yield and biomass will be positively correlated with soil health indicators and that microbial community composition will differ between till and no-till soils. Annual ryegrass (ARG) was grown in soil collected from 12 paired till and no-till ARG fields. After five months, biomass and seeds were harvested, and bulk soil was collected for microbial community analysis. We anticipate that soil parameters influenced by carbon cycling processes will correlate positively to plant biomass and seed yield and that tillage history will be correlated to plant metrics and specific microbial groups.
Progress was made under Sub-objective 2B. Cruciferous species produce a suite of well-known allelopathic compounds that alter the soil microbiome, including isothiocyanates (ITC). ITCs alleviate pathogen pressure in several cropping systems. The ability of ITCs to positively select for plant growth promoting rhizobacteria (PGPR) is not well understood and has not been studied in seed cropping systems. To understand whether brassica species improve the growth of seed crops due to ITC production, a bacterial biosensor that detects the presence of ITCs was optimized for use in soils. Greenhouse experiments that compare soils fumigated with ITCs from green manure to those that were not fumigated were initiated. Should ITCs promote the growth of ARG, we will determine if those effects are due to the presence of PGPRs or if other edaphic conditions are responsible for increased yields.
Research conducted under Sub-objective 3B facilitated the expansion of the Pacific Northwest Biochar Atlas, an online biochar decision support toolkit. We also developed and published three new case studies to demonstrate how biochar is being used. We also developed a partnership with the U.S. Biochar Initiative to establish an online learning center to provide information, frequently asked questions, and other resources to the general public. The creation of the learning center is intended to cull the spread of misinformation about the use and outcomes of biochar-based amendments by creating peer-reviewed content. Currently, seven modalities are being developed to address emerging topics and create best management practices for biochar utilization.
Accomplishments
1. Soil amendments promote the growth of plants at abandoned mines. In the western United States, over 500,000 abandoned mines cause economic and environmental harm to nearby communities. Strategies to reclaim mines are urgently needed; however, extremely degraded soils prevent plants from establishing and growing. ARS scientists in Corvallis, Oregon, collaborated with scientists from the Environmental Protection Agency to develop biochar-based soil amendments that allow plants to thrive in these extreme environments. The amendments were deployed at the Formosa Mine in southern Oregon, where plants are now growing for the first time in four decades.
Review Publications
Trippe, K.M., Manning, V., Reardon, C.L., Klein, A.M., Weidman, C.S., Ducey, T.F., Novak, J.M., Watts, D.W., Rushmiller, H.C., Spokas, K.A., Ippolito, J.A., Johnson, M.G. 2021. Phytostabilization of acidic mine tailings with biochar, biosolids, lime, and locally-sourced microbial inoculum: Do amendment mixtures influence plant growth, tailing chemistry, and microbial composition? Applied Soil Ecology. 165. Article 103962. https://doi.org/10.1016/j.apsoil.2021.103962.
Phillips, C.L., Meyer, K.M., Hanson, C.V., Biraud, S., Trippe, K.M. 2020. Manipulating rangeland soil microclimate with juniper biochar for improved native seedling establishment. Soil Science Society of America Journal. 85(3):847-861. https://doi.org/10.1002/saj2.20207.
Strimbu, B., Mueller Warrant, G.W., Trippe, K.M. 2021. Agricultural crop change in the Willamette Valley, Oregon, from 2004 to 2017. Data. 6(2). Article 17. https://doi.org/10.3390/data6020017.
Manning, V., Trippe, K.M. 2021. Absence of 4-Formylaminooxyvinylglycine production by Pseudomonas fluorescens WH6 results in resource reallocation from secondary metabolite production to rhizocompetence. Microbiology. 9(4). Article 717. https://doi.org/10.3390/microorganisms9040717.
Davis, E.W., Okrent, R.A., Manning, V., Trippe, K.M. 2021. Unexpected distribution of the 4-formylaminooxyvinylglycine (FVG) biosynthetic pathway in Pseudomonas and beyond. PLoS ONE. 16(4). Article e0247348. https://doi.org/10.1371/journal.pone.0247348.
Trippe, K.M., Meyer, K., Watts, D.W., Novak, J.M., Garcia-Jaramillo, M.N. 2021. Biochar: an alternative to activated carbon for the establishment of perennial ryegrass. Seed Production Research. 50-53.
Ducey, T.F., Novak, J.M., Sigua, G.C., Ippolito, J.A., Rushmiller, H.C., Watts, D.W., Trippe, K.M., Spokas, K.A., Stone, K.C., Johnson, M.G. 2021. Microbial response to designer biochar and compost treatments for mining impacted soils. Biochar. 3:299-314. https://doi.org/10.1007/s42773-021-00093-3.
Gent, D.H., Claassen, B.J., Massie, S.T., Phillips, C.L., Shellhammer, T.H., Trippe, K.M., Twomey, M.C. 2021. Delayed early season irrigation: impacts on hop yield and quality. Journal of the American Society of Brewing Chemists. 80:62-65. https://doi.org/10.1080/03610470.2021.1915053.
