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

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').

• 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).