Drill-seeding blue oak acorns: a new method for restoration in California’s rangelands.

Final report for FW19-355

Project Type: Farmer/Rancher
Funds awarded in 2019: $19,920.00
Projected End Date: 12/01/2021
Host Institution Award ID: G260-19-W7501
Grant Recipient: Far View Ranch Inc.
Region: Western
State: California
Principal Investigator:
Alex Palmerlee
Far View Ranch Inc.
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Project Information


Our project: "Drill-seeding blue oak acorns: a new method for restoration in California rangelands," will quantify the feasibility and cost-effectiveness of drill-seeding as a technique for restoring blue oak (Quercus douglasii) woodlands in California rangelands.

California's blue oak woodlands are rich resources for agriculture and wildlife, accounting for one-third of the grazed land in California and harboring more wildlife than any other ecosystem in California (Borchert et al.1991, Pavlik et al.1991). However, in both cleared and existing woodlands, there is a lack of new oak recruitment (Adams et al.1992, Swiecki and Bernhardt 1998). This lack of recruitment throughout the blue oak range (3-million hectares (Bollsinger 1988)) requires that a restoration solution be cost-effective and scalable. Existing restoration techniques use irrigation, caging, tree tubes, and weed control, which is effective but costly and unfeasible on a large scale. We propose to test and demonstrate the application of drill-seeding to “farm” oaks in rangelands. Restoration of blue oak woodlands will benefit ranchers by providing invaluable shade and increasing the quantity and quality of forage beneath the trees (Frost et al.1991). Also, restoration at scale will be an important factor in mitigating the impacts of climate change on rangelands, and could play a significant role in helping California meet climate mitigation goals (Cameron et al. 2017).

We will test the efficacy of drill-seeding blue oak acorns under varying conditions, combining drill-seeding with the following variables in a paired nested block study: cattle grazing, shade, and seeding rate. Germination will be quantified in the late spring. Survivorship will be measured for two years, taking place once in the summer and once in the fall after the first rains.

Data will be analyzed, prepared for publication, and shared with agency and landowner partners via two workshops and a pamphlet about the practice.

Project Objectives:
  1. Create a prototype of an acorn-seeding implement and conduct field testing and trials
  2. Demonstrate a viable technique for seeding acorns at scale with germination rates similar to other direct -seeding applications.
  3. Perform a complete cost-benefit analysis of the this drill seeding technique relative to current industry standards.
  4. Introduce 30-50 individuals (landowners, land managers, agency partners, non-profit partners) to the concept of applying large-scale agricultural techniques to rangeland restoration through a field workshop.
  5. Submit a manuscript for publication based on the findings, in an applied science journal.
  6. Create an acorn drill-seeding pamphlet, including plans for the implement that is written in plain English, free of scientific jargon, for distribution to the ranching community.

See attached Gantt chart for timeline. SARE-timeline


Click linked name(s) to expand/collapse or show everyone's info
  • Dave Daley - Producer
  • Carrie Wendt - Technical Advisor
  • Truman Young (Researcher)


Materials and methods:

Our hypothesis is that restoration of blue oak woodlands can be more efficient and cost-effective by borrowing techniques from industrial agriculture, specifically drill seeding. We expect that survival will vary greatly depending on the intensity of cattle grazing (animals/acre/month), shade, and seeding rate (acorns/acre). In order to test the efficacy of drill seeding blue oak acorns under various conditions we will combine drill seeding in a paired block study with the following variables: cattle (standard, rotated, none), shade (yes/no), seeding rate (high, low), with 10 replicates of each treatment. See the attached graphic for an example of the experimental design (SARE-exp.-design-graphic).

  • The drill-seeder itself will be built using standard farming equipment (drill-seeder-diagram). A heavy gauge steel shank will be fitted to a three-point hitch. A section of tube steel will be mounted behind the shank so that an acorn dropped at the top will land in the furrow. A chain, looped around the hitch, will drag behind the shank and pipe to re-cover the furrow and bury the acorn. This represents a simple replication of drill-seeding equipment currently in use in agricultural settings, adapted for such a large seed size.
  • Treatments, including cattle grazing, will be kept separate using standard 4-wire barbed wire fencing. Current EQIP funding for fencing on the study ranch will act as match, providing fencing for many blocks. Other blocks will be made by modifying existing fence infrastructure. Under the rotational treatment, cattle will be brought into the exclosure areas for three weeks, twice during the grazing season at stocking rates typical for the region, with consultation from our grazing advisor Dave Daley.
  • Seeding rates have been determined using data from two previous pilot projects, which showed an average survival after first summer of 21% (see below). These data come from projects where acorns were direct-seeded by hand (without irrigation or tubes) and are a helpful barometer to approximate a seeding rate. Using the spread sheet attached we calculate that our LOW treatments will need 12 acorns per 100 linear-foot of drill seeding. Our HIGH treatments will be set at 3-times the rate (36 acorns/100').

Desired mature individuals/acre

Year one survival (%)

Survival from year 1-maturity (%)

Total survival

Total initial planted/acre

planting lines per acre (15' on center)

acorns per

100' line















  • Pre-planting weed control will be standardized across all treatments and will consist of discing, at least two-weeks after the first germinating rains, to control annual grass weeds. Annual forbs and late season grasses will not be controlled.
  • Acorns will be collected from trees in the fall (Sept-Oct.) and cold-stored in plastic bags of moist vermiculite. All seeds will be collected within a 5-mile radius of the implementation site. For all replicates we will need 2,880 acorns. No more than 100-acorns will be collected from any individual tree in order to maximize genetic diversity.
  • Planting time will depend on weather (approx. Nov.-Jan.), ensuring that the ground is wet enough to cut into the soil and dry enough to drive the tractor.
  • A metal t-post will be installed at each end of the line to mark location.
  • The control treatment for each replicate will exist within the treatment area but outside of the drill-seeded lines. The control treatment will consist of similar transects not seeded except through natural recruitment.
  • The first monitoring cycle will take place in the spring after the first signs of germination (March-April). Each line will be surveyed and all germinated seedling will be measured and marked with a metal pin flag. The control for each treatment, accounting for any natural recruitment, will be measured by a line-transect method.
  • The second monitoring cycle will take place in mid-summer (June-July) to assess early summer survivorship.
  • A third monitoring cycle will take place in the fall after the first rains (Oct.-Dec.).
  • Year 2 monitoring will include a spring and late summer data collection. Seedlings that survive two full irrigation-free summers will be considered 'established'.
  • We will record all labor hours and material costs (and separately, costs associated with the experimental set up) of this project in order to calculate the cost-benefit of our new technique versus the industry standard.
  • Because increasing the seeding rate would come at a low cost, even small rates of survival can be a promising first step towards fine-tuning a new practice. We've included the HIGH seeding rate to ensure a high probability of survival. However, low or even zero survival can provide valuable insight into the feasibility of large-scale re-seeding, (especially if we find significant correlation with cattle or shade treatments).
Research results and discussion:

Results were measured as a factor of planting success (number of live individuals/number seed planted) and the cost-effectiveness of that planting (cost/surviving plant). Our results suggest that drill-seeding should be considered a valuable too for restoration of large-seeded species. Compared to identical hand planting, the cost-savings (largely a factor of labor) make drill seeding 2.6-times more cost-effective than hand planting. Palmerlee_Table 3 shows the breakdown of cost-effectiveness. We suspect that these numbers can be made even better as a large portion of the cost was due to pre-discing the planting lines, a costly step which was mainly necessary only to ensure the credibility of survivability data, as any pre-existing seedlings counted in the data would skew results. Additionally, as this is a brand new technique, there are possible improvements such as planting time and seed planting depth which may increase the rates of emergence and survival.

Another key result was the importance of year of implementation in the results. Planting this project in two consecutive seasons provided an incredible comparison and a more accurate determination of the efficacy of our new technique.

Participation Summary
3 Farmers participating in research

Educational & Outreach Activities

4 Consultations
1 Curricula, factsheets or educational tools
1 Journal articles
1 On-farm demonstrations
1 Online trainings
1 Tours
1 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

4 Farmers
22 Ag professionals participated
Education/outreach description:

SARE flyer_2020

The first workshop, held January 13th at Far View Ranch, demonstrated the drill-seeding implement in use. To ensure a large number of producers in attendance we worked with Dave Daley, a project partner and former president of the California Cattlemen's Association, to publicize the event in the California Cattlemen's newsletter and on their web site. Furthermore, we used our local and regional partners Point Blue, Yolo, Solano, Tehema, and Butter RCDs and The Carbon Cycle Institute to publicize the flyer in their newsletters and email lists.

We were very disappointed by the turn out for this event. Only 5 attendees came, 3 of whom we reached out to directly via phone and/or email. We hope that when there are results to show at our 2nd and final workshop, more people will be interested. We also intend to submit a proposal to the 2021 Oak symposium to present our findings.

March 2021 update:

Workshops/Presentations: Due to Covid-19 restrictions and concerns we did not hold any landowner workshops in 2020 or the first part of 2021. We did apply to present this project at the 2021 California Oaks Symposium, but this was also postponed due to Covid.

Journal articles: A working version of the future publication of results from this trial has been created with data collected after the first year's germination numbers, which were dismal due to a very unusual mid-winter drought in early 2020, when acorns are germinating. Luckily, we have data from the previous year, during a pilot project implemented while applying for SARE funding. Comparing these data will be extremely useful for publication. Because of the poor rain year, we spent much of 2020 applying for additional funding to pay for re-implementing the project in 2020. Unfortunately, none of our outreach efforts resulted in funding, though it did bring increased exposure to the project.

Instruction manual: Along with the journal article, a draft of the flyer/manual targeted at landowners was created. The manual will brief farmers and ranchers on the project and contain design details of the seeding implement.

December 2021 Update:

In the summer of 2021 we submitted a journal article to a prominent trade journal: Ecological Restoration. Our article: "Drill-seeding Blue Oak Acorns: Testing the (Cost-)Effectiveness of a new Restoration Technique Across Years and Microsites" was accepted for publication this fall and is in press. When the final article is released we will reach out via California Resource Conservation Districts, our contacts at California Cattlemen's Association, Audubon California's sustainable ranching community, and other interested parties.

We've also been invited to share our findings at the 2022 Oaks Symposium sponsored by the University of California Agriculture and Natural Resources.

In January of 2022 we will present our findings at the annual conference of the California Association of Resource Conservation Districts.

In the fall of 2021 we presented our final results via Zoom. 17 people attended the meeting hosted by Point Blue Conservation Science.  SARE presentation flyer

We also finalized our planting flyer/manual and sent out California Resource Conservation Districts, our contacts at California Cattlemen's Association, Audubon California's sustainable ranching community and UC Davis Natural Reserves. drillseeder pamphlet

Learning Outcomes

4 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key changes:
  • Importance of year effects on projects without irrigation.

  • Ease of creating innovative planting techniques.

  • Importance of fencing in natural oak recruitment.

Project Outcomes

2 Farmers changed or adopted a practice
2 Farmers intend/plan to change their practice(s)
5 New working collaborations
Project outcomes:

In September and October of 2019 we collected acorns for the study. It is long known that oaks are a masting species: producing massive amounts of acorns in some years and very few acorns in other years. 2019 was a VERY poor year for acorns. Hours and hours were spent by the PI (Alex Palmerlee) as well as a neighboring rancher and botanist. Together, we collected 2,000 acorns over the course of 8 days of harvesting. Many trees had no acorns, some had 5-10, and a very few had 20-40. Because of this, we reduced the number of acorns used in each replicate from 35 to 30, in order to complete all replicates with the limited number of acorns.

In December of 2018, while looking for funding for a larger trial, we tested the concept of the acorn seeder. In December of 2019 we modified the drill-seeder and planted all replicates. Replicates were disced, then seeded, and the seeded lines were marked by metal t-posts.

On February 11th, 2020 we sprayed each line with Roundup herbicide at 1-ounce/gallon with a fan nozzle spraying approximately 2-3' with the planting centered in the spray-zone.

March 2021 Report:

In June of 2020 data were collected showing dismal results. Most notably, a 7-week mid-winter drought spanning late January-mid March meant that many acorns likely germinated but then died in the dry top soil. The data tell a staggering story (see attached table). Only 2.3% of acorns emerged; this compared to 12.9% emergence in the project planted in 2018. There is a good outcome from comparing this data in that we see also how critical a wet winter is to making it through summer, as seen in the table attached. It is important to consider that even acorns planted via traditional, labor and material-intensive methods, would likely have died in these conditions.

These wildly divergent results show the importance of implementing research projects identically in multiple years. Year effects have a powerful role in oak recruitment. We hope that with our next round of data collection we will be able to tell a more complete story about the efficacy of drill-seeding (precisely because we have data from 2018-19 as well as 2019-20.

2020 Drill Seeding summary table

December 2021 Report:

There are several key take aways from this project:

1. Interannual variation: As we mentioned previously, year of implementation has a dramatic effect. The results from our 18-19 project show a very different story than the results of our 19-20 planting. This figure Palmerlee_Figure 3. illustrates the importance of year-effects, in our case the difference of a wet 18-19 winter (40-inches of rain) versus a dry 19-20 year (16-inches of rain). What we also see is that the relationship of cattle and shade did not interact as expected. In the wet year, our No Cattle + Shade replicates did not fare as well as we expected. In many cases the amount of grass growth was so intense that it out-competed the acorns. However, shade becomes helpful again in the dry year, when less grass growth means the oaks take better advantage of the shade. In Cattle + Shade replicates, cattle's tendency to congregate under oaks for shade left many of our plots trampled to bare ground.

2. Cost-effectiveness: When we add cost to the equation, as illustrated by Palmerlee_Table 3, the 'success' of the planting is seen in a new light. Adding cost shows that because of the low initial cost of seed, planting with a less labor-intensive process allows for drill seeding to be 2.6 times more cost-effective than hand planting. This is our big take away: if you're planting acorns by hand, without interventions such as tubes and irrigation, you're better off building a seeder and planting with a tractor. Furthermore, because interventions such as tubes and irrigation (commonly used in oak restoration) are so costly, a traditional restoration project would need to see 60% survival after two years to compete with the drill seeded planting.

3. Restoration Versus Management: Our results suggest that in areas with mature oaks, a management solution is likely more cost-effective than active restoration. Indeed, three of our year 1 No Cattle + Shade replicates had to be thrown out of the dataset because there was so much natural recruitment around our planting line we could not distinguish the planting line. Instead, restoration should be targeted at areas with either no or very few oaks and drill seeding should be seen as an important tool to consider. In order to further parse out these two issues, we plan to submit a proposal to the NRCS Conservation Innovation Grant to do a large ranch survey to quantify the areas where oaks are recruiting naturally in the presence or absence of cattle.

4. The Seeder works: Our results show that the drill seeder works and that with further testing can be make even more cost-effective. For example, we disced the study plots before planting, largely as a way to control that there were no oak seedlings existing in the planting area that would bias our results. This is a large part of our costs, requiring an extra pass with a tractor, operator, and implement. Also, our emergence rates were very low, suggesting that there are details we aren't considering: planting depth, timing, or location for example. More research is needed to come up with a list of best management practices and to further establish the drill seeding of large-seeded species as a viable tool for restoration.

Success stories:

Faced with a severe acorn shortage, we worked with a neighboring landowner with a 2,000-acre ranch who had several good-producing (20-40 acorns/per) oak trees. The landowner donated approximately 28-hours of his time to collect acorns with the PI and on his own. Without these contributions we would not have collected enough acorns to complete the project AND we brought in a new project partner and landowner with about 1,000-acres of deforested land that could be a good fit for future drill seeded oak projects.

One of the attendees on our Zoom meeting said that in the future he would, "put on my 'Alex' hat to think more about cost and how to implement a project with good results for less." Getting restoration practitioners and land managers to consider not just planting success, but cost per surviving individual into their considerations can only help more work be accomplished per dollar spent and more innovation of new techniques.


Oak masting, which created a significant challenge for our project because we struggled to find adequate acorns, is one of several factors making multi-year studies crucial for a fuller picture. There are several key year-effects that can influence the outcomes of research (rainfall, temperature, rodent/vole population cycles, etc). Implementing identical projects in multiple years can strengthen the results of any given project.

We were extremely fortunate to have implemented a pilot of this project the year before our SARE funding. Without the data from the first year we would have little to compare our results to. Year 2 was so bad, not just quantity of rain but also the timing of that rain, that we had very poor emergence. Without our strong numbers from Year 1 we'd have less confidence in the use of our drill seeder.

We were very successful in turning a lot of miscellaneous tractor equipment into a seeder that cost us nothing but time. Palmerlee_Figure 1. This is exactly what we set out to do: create a simple low-tech seeder that could easily be replicable by landowners with common farmyard tools.

The fact that our results will be published in a leading restoration journal demonstrate the value and cutting-edge nature of this project. We are very proud to receive this positive feedback.

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.