Pacific Northwest Cover Crop Decision Aid System

Progress report for SW22-940

Project Type: Research and Education
Funds awarded in 2022: $349,697.00
Projected End Date: 09/30/2025
Host Institution Award ID: G102-23-W9209
Grant Recipients: University of Idaho; Palouse Conservation District
Region: Western
State: Idaho
Principal Investigator:
Dr. Sanford Eigenbrode
University of Idaho
Kendall Kahl
University of Idaho - Soil and Water Systems
Dr. Subodh Adhikari
University of Idaho
Ryan Boylan
Palouse Conservation District
Tracy Ericksen
The Eriksens
Garry Esser
Esser Farms
Dr. Douglas Finkelnburg
University of Idaho
Dr. Patrick Hatzenbuehler
University of Idaho
Lucas Sheneman
University of Idaho
Chloe Wardropper
University of Idaho
Frank Wolf
Lester Wolf Farms
Clint Zenner
Zenner Family Farm
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Project Information


This collaborative project uses replicated on-farm research trials in combination with online information delivery to support adoption of cover cropping for inland Pacific Northwest (iPNW) dryland cereal-based cropping systems. Globally, cover cropping is a recognized strategy for mitigating soil erosion, loss of fertility and soil acidification, compromised soil health, reliance on synthetic inputs, and decreased biodiversity that jeopardize the sustainability of cropping systems. Despite these advantages, adoption of cover cropping has lagged in the iPNW relative to other regions. This is largely due to uncertainty regarding integrating cover crops into longstanding cereal-based crop rotations and how cover crop species perform for specific agronomic goals. In much of the region, low precipitation presents unique challenges to cover crop establishment and ensuring moisture sufficient for primary cash crops. Ongoing climatic challenges, including reduced summer precipitation and greater frequency of heat stress events, exacerbate these changes. The grower partners for this project (co-PIs and cooperators), all of whom are early adopters of cover cropping in the region, are motivated to diversify their production for the long-term benefits to soil health and resilience to climate variability and the potential to generate novel sources of income for their farms. They have expressed needs for research to help them and others succeed with cover crops in the iPNW, and participated in the design of this project’s three objectives: 1. Compare cover crop mixtures and termination dates for effects on cover crop performance, water infiltration rates, bulk density, nitrogen availability, weed and insect biodiversity and performance of the subsequent cash crop, 2. Compare the effects of treatments in Objective 1 on soil moisture profiles during the season and after different termination dates, 3. Use information from Objectives 1 and 2, existing published literature and data, and grower workshops and interviews to develop a comprehensive online support system for iPNW cover crop management. The system will include tools for deciding on what cover crops to plant and how to manage them, links to cover crop information and a platform for producer discussions and information sharing. The project will be the first of its kind to address key issues challenging cover cropping in iPNW cereal systems by providing key information needed for optimization and adoption. It is a crucial step toward improving soil health and the sustainability of these systems over the long run. This proposal is for a 3-year project, but we have also indicated the intent to carry it on for three additional years with additional funding to be requested in a proposal to WSARE.

Project Objectives:

1. Compare cover crop mixtures and termination dates for effects on cover crop performance, water infiltration rates,

bulk density, nitrogen availability, weed and insect biodiversity and performance of the subsequent cash crop

2. Compare the effects of treatments in Objective 1 on soil moisture profiles during the season and after different

termination dates

3. Use information from Objectives 1 and 2, existing literature and data, and grower workshops and interviews to develop the first comprehensive online support system for inland Pacific Northwest cover crop management



Project organizational meetings will include a launch meeting and annual project meetings in the first quarter of each year. Funds are requested for a project start in October of 2022. We will use the last quarter of 2022 for planning and to begin constructing the PaNDAS site. Plot establishment and assessments for Objectives 1 and 2 will take place in 2023-2025. In a fourth partial year (2025), data from the subsequent winter wheat will provide three full years of that assessment. Workshops to inform PaNDAS design will take place in the first winter (2023). Review of beta versions of PaNDAS site will be ongoing into 2024. A live version of PaNDAS will be launched in first quarter of 2024 and maintained through end of project. Funds will be sought to continue PaNDAS, which is conceived as a permanent, dynamic resource for producers.  Each season, the project will be represented at field days and grower schools, and it will hold its own field day demonstration at two of its (AC and AC-F) sites.


Table 2. PaNDAS project timeline

PaNDAS Timeline_


Click linked name(s) to expand/collapse or show everyone's info
  • Bruce Petty - Producer
  • Doug Schuster - Producer


Materials and methods:

Research Objectives 

The project addresses two key grower-identified questions through two objectives.

  1. Compare cover crop mixtures and termination dates for effects on cover crop performance, water infiltration rates, bulk density, nitrogen availability, weed and insect biodiversity and performance of the subsequent cash crop
  2. Compare the effects of treatments in Objective 1 on soil moisture profiles during the season and after different termination dates

Design and Treatments

Treatments will be applied in replicated trials on the eight working farms of the Producer Co-PIs and Producer Cooperators for this project. Four farms will be in the region’s lower precipitation Annual Crop-Fallow (AC-F) agroecological zone where business as usual (BAU) cropping consists of a three-year fallow-winter wheat-spring wheat rotation.  Four farms will be in the higher precipitation annual cropping (AC) zone where BAU consists of a three-year rotation, predominantly spring legume-winter wheat-spring cereal. On each farm, nine strips (~ 0.5 ac. each) will be established within BAU fields, replacing fallow in AC-F and spring wheat in AC with experimental cover crop mixtures. A schematic of the plot design on a participating farm over three years is provided in Figure 1.

Figure 1. Schematic of plot design for each of 8 cooperator farms (total area of reps 1-3 ≈ 4 acres)

Figure 1_FINAL

Cover Crop Mixtures. On each farm, three cover crop mixtures will be established, each with three replicate strips. Configuration will vary among farms to accommodate geometry and equipment. Common treatments will include a low-diversity cover crop mixture (LD) and a high-diversity cover crop mixture (HD). The LD mixture will include one grass, one legume and one brassica species in these proportions: 60% oats, 30% pea, and 10% turnip. The HD mixture will include three grasses (20% oats, 20% millet, 20% triticale), three legumes (10% pea, 10% sweet clover, 10% lentil), and three brassicas (3.3% turnip, 3.3% radish, 3.3% mustard). The third mixture on each farm will be a ‘producer’s choice’ (PC). We recognize that growers in different parts of the region, in addition to their common interests and questions about cover crops, have different challenges that influence their selection of cover crop mixes. The PC treatment will enable producers to test performance of a mixture designed based on their experience and interest. The findings about these mixtures will also inform our cover crop selection tool (see Objective 3). The PC mixtures and rationales for including them (Table 1) were developed as an outcome of a discussion involving all the cooperators and producer co-PIs for this project. Rationales common to several producers include nitrogen fertilization (4/8), weed suppression (4/8), bio-drilling (4/8, all in AC-F subregion), increasing organic matter (3/8), grazing income (2/8, both in the AC subregion). For this project, all three treatments will be established each year in the spring to improve comparability. There is also interest in fall planted cover crops in the region but evaluating those practices will be beyond the scope of this project.

Table 1 Producer-choice cover crops which will comprise the third treatment on each farm.

Table 1

Termination Dates. Each of the standard treatments (HD and LD) and most of the PC treatments (see Table 1) will be terminated using herbicide in a split plot design on three dates based on cover crop vegetative growth profiles. Termination date 1 (TD1) will be on or before June 1, when cover crops are fully established and in accordance with USDA-NRCS guidelines and crop insurance program requirements. Termination date 2 (TD2) will be at first pod formation in any cover crop legume, and TD3 will be when all cover crops have reached maturity. The dates selected will maximize biomass production and related benefits to soil health while minimizing excessive moisture loss through transpiration and seed production leading to volunteer plants in the following.  Producer-choice mixtures will also be terminated on these dates.

Subsequent Crop: Each year, strips will be relocated on each farm, marking their locations. In the subsequent cropping year, the ground with strips will be planted to winter wheat following standard grower procedures. The subsequent winter wheat crop yield and quality and soil nitrogen availability in near-surface soil will be measured in this follow-on wheat crop in the previous year’s cover crop and BAU strips to assess the effects of cover crops on the principal cash crop.  Measurements to address Objective 1 and 2 on all farms will be as follows:

Objective 1.  Cover Crop and Subsequent Cash Crop Performance: Cover crops will be evaluated for percent emergence and established stand diversity and cover crop coverage and biomass by species at each TD. In the second and third year of the project, the subsequent winter wheat will be assessed following cover crop and in the BAU system for emergence, stand, mature biomass, yield, grain moisture and protein.

Soil Physical Properties: Penetration resistance (Dane et al. 2002), bulk density (Grossman and Reinsch 2002), and water infiltration rates (van Es and Schindelbeck 2001) in cover crops at TD3 and in the subsequent winter wheat crops will be assessed to determine the impact of cover crops on soil physical properties.  Penetration resistance measurements and infiltration rates will be measured once a year in cover crops and the following winter wheat crop.  Bulk density measurements will be made prior to planting of the cover crops and at the end of the experiment.

Soil N and Organic Matter: Plant available nitrogen (Mulvaney 1996) in the first 1.5 m of soil will be measured in one TD in LD, HD and PC cover crop treatments at each site both in spring and at harvest.  Three replicate, 1.5-m deep soil cores will be taken within each plot and split into 30-cm increments in the field.  Subsamples from each depth increment will be combined to form one representative sample per treatment that will be analyzed.  Changes in plant available nitrogen with depth, along with measured values of total nitrogen in above ground biomass, will be used to evaluate the impact of each cover crop treatment on nitrogen uptake and availability to the following crop.  Sampling in the winter wheat crop will be limited to spring and results will be utilized to determine nitrogen fertilization application rates. Soil organic matter, estimated by loss on ignition (Nelson and Sommers 1996) will be assessed on the same samples collected to determine plant available nitrogen.

Weed and Insect Pressure and Biodiversity: Aphids (Aphididae; e.g., cereal aphids, pea aphid), wireworms (Elateridae), hessian fly (Mayetiola destructor), pea weevil (Bruchus pisorum), and pea leaf weevil (Sitona lineata) are some of the key insect pests in the iPNW. Additionally, several beneficial insects such as bees, wasps, flies, ladybug beetles, green lacewings are present in the region that need to be documented on cover crops. Similarly, key weeds are Mayweed chamomile (Anthemis cotula), cheat grass (Bromus tectorum), rattail fescue (Vulpia myuros), prickly lettuce (Lactuca serriola), common lambsquarters (Chenopodium album), and catchweed (Galium aparine). Baseline information of weeds, insect pests and beneficial insects within BAU and alternative cropping systems is important to understand the sustainability of future agricultural landscapes. Substantial changes in crop species and diversity could promote ecosystem services such as biological control and pollination, but also promote disservices by exacerbating existing pest populations or introducing new pests. To anticipate these potential effects, pests and beneficial organisms will be assessed in all treatments in the on-farm strip trials and in adjacent BAU crop fields. Briefly, weed abundance, coverage and diversity will be assessed before each termination dates in five 1-m2 quadrats in each cover crop strip and adjoining BAU fields during first two years,  and in winter wheat following cover crops in the second and third years. Aboveground weed biomass will be assessed by clipping all plants rooted within quadrats, sorting to species, drying, and weighing. Following a similar schedule, insect pests and beneficials will be assessed on each strip using a D-Vac vacuum sampling along a W-shaped 30 m transect. Insect samples will be sorted to species for key pest species and beneficial insects to genus or family.

Objective 2. Sensors linked to data loggers (Acclima, Meridian ID) will continuously monitor volumetric soil moisture and temperature at two depths in each cover crop treatment at TD2 and TD3 in one replicate block per farm. There will be 14 probes per site, which include 2 probes in each LD, HD, and PC at both TD2 and TD3 as well as 2 probes in the BAU.  As a complement, soil moisture will be measured gravimetrically based on soil samples at the beginning and end of each growing season in all plots on each farm, utilizing the same cores collected under Objective 1. Volumetric water contents will be calculated utilizing measured bulk density values. These measurements will allow assessment of water use and tradeoffs between soil moisture conservation and biomass production. Replicated gravimetric measurements will allow comparisons of treatments within and across farms. Continuous monitoring will provide new information on soil moisture dynamics to understand the origin of point measurement values and guide future efforts to identify optimal cover crop termination dates to balance benefits of biomass production and potential costs of cover cropping to the yield of subsequent cash crops in our region. Termination dates currently are determined by producers based on intuition, scantly replicated experience on individual farms and generally follow some aspect of cover crop phenology as an approximate guide. Some are incentivized to terminate early (before June 1) for crop insurance reasons. Data will be widely disseminated to stakeholders through our decision support system (see Objective 3). Results on termination after June 1 and before end of season will have relevance for those involved in advising on crop insurance policy requirements. Water infiltration rates will be measured in all treatments each spring and after the final TD. This measurement has been encouraged by producers who have seen evidence of water infiltration improvement after cover crops and are greatly interested in this output from the project. Under low rainfall, this can be critical for maximizing harvesting of precipitation for crop growth.

The project began formally on October 1, 2022. Between that start date and April 15, 2023, the specific plot locations were identified on each of the 8 farmer cooperator/co-PI farms and flagged for planting. Installation of instruments to measure soil moisture and planting all happened subsequent to that date. Seed for the common cover crop mixtures was procured and delivered to each farm in preparation for planting. No issues were encountered during these initial stages of the research component of the project.

Analysis for Objectives 1 and 2

The effects of cover-crop treatment, nested within farm, on each response variable (soil biological, chemical and physical properties) will be analyzed with analysis of variance (ANOVA), multivariate analysis of variance (MANOVA), or mixed models with data transformed as required for each variable. For common cover crop treatments, the effects of farm site and production zone and their interaction on response variables will also be assessed. Specifically, differences in weed and insect abundance, species richness, diversity, and community composition will be analyzed using appropriate mix-effects ANOVA models and multivariate analysis such as Non-Metric Multidimensional Scaling (NMDS). We will test differences in weed and insect community structures between cover crop treatment and termination timing using Permutational Multivariate Analysis of Variance (PERMANOVA) of the dissimilarity matrix using the vegan package in R statistical software (R Core Team 2019, Oksanen et al. 2020). This will enable detection of effects that are broadly relevant in the iPNW across its precipitation regimes and those that are site or production class specific, critical information for guiding cover crop implementation and management. Summaries of all these findings will be distilled for presentation on the project’s PaNDAS website into thematic segments such as: “Terminating your cover crop to optimize water use”, “Best cover crop species for water conservation”, and “iPNW cover crops and weed suppression”. The findings will also be unique and publishable in refereed journals including Journal of Agronomy, Journal of Soil and Water Conservation, Applied Soil Ecology.

Research results and discussion:

The project start date was October 1, 2022. Between then and April 15, 2023, no plots had been planted, instruments installed, or data acquired. No research results were acquired concerning cover cropping diversity and effects on soil moisture. The only field activities consisted of procuring seed, confirming and flagging the plot locations and boundaries on each farm.

Participation Summary
8 Producers participating in research

Research Outcomes

Recommendations for sustainable agricultural production and future research:

By the report date, April 15, 2023, no novel recommendations for sustainable agricultural production and future research can be offered, other than to note that, based on our surveys, although the issue of termination data and cover crop diversity are critical, there are many other aspects of cover cropping that require improved education and relevant research for the iPNW region. The project will continue to acquire this information through its outreach activities and to be summarized in project reports and potentially a refereed publication.

Education and Outreach

20 Consultations
1 Curricula, factsheets or educational tools
3 Webinars / talks / presentations

Participation Summary:

55 Farmers participated
14 Ag professionals participated
Education and outreach methods and analyses:

The project  has a social component in which participating producers were interviewed to determine their views on cover cropping, perceived barriers to adoption and challenges to implementing cover cropping in the cereal production systems of the inland PNW. In Dec. 2022, a semi-structured interview guide was designed with open-ended questions around: each operation context, producers' previous experiences with cover crops, expectations on the WSARE research project, cover crops benefits and concerns, and ideas for scaling up cover crop adoption in the inland Pacific Northwest.

The 8 in-person interviews were performed between December 2022 and January 2023. Each interview lasted approximately 1 hour, totaling 8h40m of content recorded. The 33-page report consists primarily of extracted quotes from subjects on a range of topics pertaining to cover cropping. 

  • Perceived benefits of cover crops
  • Cover crop concerns
  • Livestock on cover crops
  • Producer expectations related to WSARE project
  • Needs for scaling up cover crop in the inland Pacific Northwest


A presentation and data -gathering activity were conducted as a component of the Palouse Alternative Cropping Symposium held on Feb. 24 in Colfax Washington. Approximately 40 producers and 20 other persons were in attendance. These participants were provided with a quick overview of the interview based document followed by a data gathering activity using Menti-meter and prompts to garner views on cover crop challenges and benefits. Prompts included:

  • How do you rate each of the following factors as a  ‘+’ to ‘-‘ tradeoff you would (or are) experience by using cover crops?
  • Which of the following best describes your view on the relation of livestock to cover cropping for this region?  
  • What factors need to be in the economic equation to assess cover crops? (7 words or less)
  • How could your community benefit from expanding the use of cover crops?
  • In your view, when do you expect to be the best time during the crop year to BOTH plant AND terminate a cover crop? (choose one)


A website was created that houses a resource hub for cover cropping in the inland PNW, a synopsis of the project design and objectives, a link to a page with project updates, a link to a registration to enter a discussion board with threads on cover cropping issues, currently: "Seeding spring cover crops"; "Diversifying farm operations", "Cover cropping", "Other topics for the project". This website was stood up and beta tested during early 2023, after which it was fully activated. It has been operational since early February 2023.

Education and outreach results:

Reports of results of the producer interviews and the data gathered at the Palouse Alternative Cropping Symposium were generated and posted to the project website:

Education and Outreach Outcomes

Recommendations for education and outreach:

None to report at this time.

Key areas taught:

    Information Products

      Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.