Adaptation of Warm Season Perennial Grasses for Forage Quality, and Resilience High Temperatures in California Irrigated Pastures

Progress report for OW23-384

Project Type: Professional + Producer
Funds awarded in 2023: $74,975.00
Projected End Date: 03/31/2026
Grant Recipient: University of California Ag and Natural Resources
Region: Western
State: California
Principal Investigator:
Theresa Becchetti
University of California Ag and Natural Resources
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Project Information


California has been experiencing a warming trend with hotter summers and long-term forecasts expect the trend to continue.  Irrigated pastures are a key component to livestock operations and historically planted with cool season forages.  We propose to investigate warm season forages better adapted to a hotter summer, while being palatable and maintain the current level of production. This is key to ensure financial viability of ranches and protect the natural resources of associated rangelands. Small plots at the USDA Lockeford Plant Material Center (PMC) are our first step to investigate which species will establish and test for nutritional value. The PMCs in Arizona, New Mexico, and Texas have information on adaptation and forage value of warm season grasses species that we will utilize.  With the help of our partners, we will select species to then plant on their irrigated pastures, adding the warm season forages to the existing forage. We will collect forage production and forage quality data as well as data on selectivity of cattle.  Field days at the PMC and our partners’ irrigated pastures will demonstrate the success of warm season species.  We will also use print (newsletters, handouts, newspaper articles, blog posts, trade magazines, peer-reviewed articles) and social media posts to educate ranchers not only in our local area, but regional and statewide.  We expect to be able to identify species well adapted to our summer heat while being palatable and highly productive, providing a viable forage for our irrigated pastures long into the future.

Project Objectives:
To determine warm season forages that thrive in California’s hotter summer climate while providing nutritious, palatable forage. 

Please see Grantt Timeline for visual layout: Gantt_Timeline Becchetti

  • Spring 2023
    • Seeding of plots at PMC
      • Seeding was completed April 27, 2023.  The Plant Material Center (PMC) prepared plots to be planted with their drill.  Triticale was used to ensure proper planting depth and rate.  Seeds for planting at the PMC were received from PMCs in other states where the warm season grasses are common.  The annual mix was donated by local seed company.  During seeding, the crew noticed one seed was not falling correctly through the seeder.  The seed was determined to be too "fluffy" for the drill mechanism, the drill was then cleaned out, and the seeds determined to be too fluffy for the drill were hand broadcasted and lightly harrowed.  One week post planting, very little germination from the planted species could be found, but there was a heavy weed pressure.  Researchers started an aggressive weed management with hand pulling since annual bluegrass (Poe annual) was germinating as well as broadleaved forbs, making herbicide not the best choice.  If grasses could not be identified, they were allowed to grow and not pulled.  After two month of this effort with very little germination seen of the planted species, the team decided the planting was a failure and started to research what might have gone wrong.  The ranchers involved in the project were kept up to date on the plots, and were notified that the planting failed, including the broadcasted plots.  Discussions with PMCs in Arizona and New Mexico to determine our best course of action shed light that our planting date might have been too cold for germination in addition to the heavy weed pressure.  Plans were adjusted to plant again in 2024 growing season, researching required temperatures, weed control planned ahead of planting, and planting methods to prevent seeds from being lodged in the planter.  With this set back in plots, this will push our timeline back as well.  We will be requesting a modification in our schedule to adjust for our failed germination in Year 1, moving everything back a year.    
  • Summer 2023
    • Irrigation and sampling of plots
      • Irrigations occurred for about two months before the plots were considered a fail.  Sampling did not occur because there were no grasses to sample.  
  • Fall 2023
    • Project meeting with partner ranchers to see PMC plots, select species for Spring 2024 planting
    • First Field Day at PMC
    • Newsletters created to summarize first irrigation season results
  • Spring 2024
    • Planting of small pastures on partner ranches
  • Summer 2024
    • Irrigation and sampling at all sites
  • Fall 2024
    • Project meeting with ranchers to discuss successes, concerns, and next steps.
    • Newsletters created.
    • Field Day at PMC and at least one partner site
  • Summer 2025
    • Final irrigation season and sampling on all plots
  • Fall 2025
    • Project meeting with ranchers to discuss status of project after two summers
    • Newsletters created
    • Field Days at PMC and partner sites.
  • Winter 2025
    • Prepare final reports, presentations at livestock meetings, trade magazine articles and peer-reviewed article.
  • Spring 2026
    • Hold last field days to encourage ranchers to add warm season forages to their pastures based on results of the project.


Click linked name(s) to expand/collapse or show everyone's info
  • Theresa Becchetti - Technical Advisor (Researcher)
  • Alan Bower - Technical Advisor
  • Philip Brownsey - Technical Advisor
  • Annie Edwards - Technical Advisor
  • William Fogarty - Producer
  • John Gallo - Producer
  • Steve Kistler - Producer
  • Kristan Norman - Technical Advisor
  • Margaret Smither-Kopperl - Technical Advisor


Materials and methods:

The research approach to this project will include two separate, but complimentary components. The first is a replicated field study at the Lockeford PMC in San Joaquin County looking at establishment success, growth, and nutritional quality over the course of the irrigation system of a selection of potentially desirable warm season perennial grasses and comparing these to traditional cool season species mixes. The second will be working with producers in San Joaquin and Stanislaus Counties that will select warm season perennial grasses, informed by initial results from the PMC study, and establishing these on a portion of their irrigated pastures and looking at establishment success, growth, and nutritional quality of these species mixes, compared to existing cool season species mixes in a production setting.

Warm season perennial grass species will be established on replicated small plots at the NRCS Plant Materials Center (PMC) in Lockeford following PMC protocols for research design in the spring of 2023. In addition, small plots of a cool season grass mix (orchard grass and perennial ryegrass), as well as a cool season grass and clover mix (orchard grass, perennial ryegrass, strawberry clover, and bird’s-foot trefoil), representing typical irrigated pasture mixes used in the area will also be established. We expect to select 12 to 20 species of warm season grasses for the PMC portion of the study, along with traditional pasture mixes. All plots will be assigned in a randomized complete block design with 4 blocks. Plots will be 5 feet by 20 feet and established using the plot drill at the PMC.  Irrigation will be applied either through a linear irrigation system or wheel-line at the common irrigation rates of the area to hold the water constant across the plots.

Data collected for each of 3 years at the PMC will include:

  • Soil analysis (performed by a third-party lab),
  • Amount and timing of irrigation water applied,
  • Soil moisture,
  • Initial growth and regrowth of each species by repeated clipping, and
  • Nutritional analysis (performed by a third-party lab) of each species through the irrigation season (at least 3 points between May and October).

Selection of species and method of planting will be determined in consultation with each of the partner ranchers using the plots at the PMC and the data collected during the 2023 irrigation season to inform these selections. The goal will be to establish warm season perennial grasses in 1 to 2 acres of currently irrigated pasture, with 1 to 2 acres of a paired reference cool season pasture adjacent. The warm season pasture may be established by interseeding into existing irrigated pasture by broadcast followed by pasture harrow, interseeding into existing irrigated pasture with a no-till drill or by establishing new pasture by leveling and then seeding of a mix of warm season grasses and appropriate legumes by broadcast and pasture harrow or by seed drill, depending on the specific situation and needs of the partner rancher for each site. Seeding would occur in spring of 2024 at the start of the irrigation season and grazing would be deferred until the pasture is established, likely during the 2025 grazing season. Maintenance during the first growing season may include clipping and baling or targeted grazing. The 2025 irrigation season would represent the established pasture performance for each pasture.

Data collected for each of 2 years at each of the partner ranches will include:

  • Soil analysis (performed by a third-party lab),
  • Seed mix and rate, method, and site prep,
  • Amount and timing of irrigation water applied,
  • Soil moisture,
  • Species composition for each pasture,
  • Initial growth and regrowth of pasture vegetation by repeated clipping of protected cage grazing exclosures,
  • Nutritional analysis (performed by a third-party lab) of each species through the irrigation season (at least 3 points between May and October), and
  • Grazing timing, duration, and stocking rate, as well as any other management interventions, such as clipping and baling.

Data will be presented as means and standard errors. Comparisons and tests of significant differences will be made using t-tests on the means and Tukey’s HSD where appropriate when performing multiple comparisons. The primary objective is to compare how production and nutritional quality (crude protein, neutral detergent fiber, and acid detergent fiber) compares over the course of the irrigation season and between each of the warm season grass species and the typical cool season pasture mixes in order to identify whether any of the warm season perennial grasses tested would be suitable species for irrigated pastures after the observed climate change in the region of the study.

Funds will be reserved to allow for the herbicide treatment of the warm season perennial pasture established in the trial and reseeding with a cool season pasture mix in the event that the selected species become problematic for the ranch operation and it is necessary to undo the project.

Participation Summary

Research Outcomes

Recommendations for sustainable agricultural production and future research:

We still believe our hypothesis is viable, but we let old thinking of when we should plant, based in part by a calendar date and historical weather patterns, influence our timing which in part led to a failed first year of plot work.  Long term forecasts show a hotter, drier California, which will mean that irrigated pastures will need to make changes in the near future to maintain productivity needed by rancher.  

Education and Outreach

2 Consultations

Participation Summary:

3 Farmers participated
1 Ag professionals participated
Education and outreach methods and analyses:

With a failed planting, we had no data to share in any meetings or newsletters as planned. The ranchers involved in the project were all notified of the failed germination.  We have taking steps to ensure success for plots in 2024 and then will progress with education and outreach methods as planned.  

Education and outreach results:

We have no results since we had no education and outreach the first year.  All of our planed efforts we are planing to move back one year.  

Education and Outreach Outcomes

Recommendations for education and outreach:

With a failed plot plantings, our planned outreach and education activities did not happen.  We have captured data on our failure to share with ranchers as we share information on the project, especially how to avoid pitfalls to have a successful pasture establishment. 

Key changes:
  • With planting failure, there was no opportunity for change in knowledge.

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.