Fruit and Berry Tree Crop Trial Program for Native Alaskan Rural Communities in Interior Alaska
Project Summary: This research project is investigating the potential for the production of domestically grown fruit and berry crops on cold (zone 2) sites in Interior Alaska. This research project utilizes cold, hardy fruit identified in other northern research locations and combines their production with the evaluation of high tunnel plastic structures that can potentially improve survival and yields of these crops. It is our hope that we can identify specific varieties of apple, cherry, plums, pears, and berries that can survive and produce fruit on zone 2 sites and the possible positive impacts of the use of high tunnels to increase survival and fruit yields, which could then be acquired and adopted by native communities.
Objective 1 : Establish two high tunnels and plant 2 plots interior and 2 plots exterior for the 3 year trial.
Objective 2: Establish environmental monitoring equipment for the trial for both interior and exterior plots.
Objective 3: Monitor survival and growth of trees through the first year along with evaluation of any fruit production for yield and sugar content by variety.
Preparations for the 2007 Spring planting of the fruit trees began in fall of 2006 with the location of the research trial on the grounds of the University of Alaska Agriculture and Forest Experiment Station in Fairbanks. Arrangements were made for the purchase of two (42’x96’) high tunnels from FarmTek. The structures were erected in late May and early June of 2007. Meanwhile, arrangements were made for the production of the root-grafted fruit trees including a selected list of 39 apple varieties. The very cold hardy Ranetka Crabapple tree, a cross between Siberian and Dolgo crab trees, was used as the grafted root stock. The trees were picked up at the nursery facilities in Wasilla and delivered to the planting site at UAF in late May 2007. Once the high tunnels were erected, we proceeded with the tree planting in mid-June. During October 2007 we established two Hobo weather stations and four Hobo micro-stations for recording hourly environmental conditions including air and ground temperatures, relative humidity, PAR, solar radiation, wind speed and gust speed, and soil moisture. These have been very helpful with interpreting the effects of the high tunnels on the trees being grown within them. We were able to monitor conditions of the outside and inside plots throughout the winter and link them to spring survival data. Through this project we were wanting to determine what were the impacts of the high tunnels on survival of the test varieties and any associated impacts on growth and yield for a cold site. Through the use of the weather data stations we were able to determine how closely the test site represents similar cold sites found in rural communities. Any success of the test varieties could then become the basis for recommendations for testing in rural villages.
We found that there was a dramatic difference between inside the high tunnel air and ground temperatures and those found outside the high tunnels. The thermal blanketing effect of the 16 inches of snow throughout the winter had a considerable effect on moderating the outside ground temperatures. We were surprised that the unheated but closed-up high tunnels provided very significant improvement in air temperatures. On the coldest day we found that where the outside air temperature was -47F the inside air temperature was -24F. The effects of the high tunnels on moderating extreme winter cold conditions resulted in the HT trees having less mortality than the outside plots since the HT temperatures fell well above the anticipated cold temperature limits of tree survival.
The following two charts (page 5) compare the daily soil and air temperatures for the outside (exterior) and inside the high tunnel conditions (Nov. 26, 2007-March 11, 2008). The snow cover on the outside plots provided substantial protection for the outside trees. The inside plot had colder soil fluctuations than the outside plots but were still very tolerable for the trees to survive. The exterior plots had very stable soil temperatures under the 16 inches of snow cover. In addition to these observed temperatures we were interested in the effect of the plastic 7oz. mesh plastic covers on the high tunnels for filtering both photosynthetically active radiation (PAR) and total Solar Radiation.
The two graphs shown above compared the solar radiation and PAR for both the exterior and interior plots and interior plots during the Nov. 26th – March 11th winter period. These results indicate that the filtering of the high tunnel covers is especially pronounced during the winter and increases as summer progresses. However, even at the peak of summer we found that the 7oz woven mesh transparent plastic cover material effectively filters about 30% of PAR to the trees. Based upon the survival, growth, and yield of the inside HT trees, we concluded that the shading had not caused a substantial loss to the trees. Given the long day length that we have at our northern latitude, it may even provide some protection from sun scald. It was noticeable that the shading effect was much more pronounced during winter period than during the summer. After consulting with experts on this issue it was concluded that this effect was most likely due to the reduced sun angle on the horizon and the effects of snow on the outside and ice and frost built up on the inside surface of the plastic cover that served to disperse the available light as well.
We found the covers to be relatively strong and durable under a snow load and cold temperatures. Throughout the duration of the winter we found that most of the trees did not lose their leaves until early spring. This however did not seem to affect their survival. Although the outside trees did lose their leaves, they were subjected to much more wind events and colder temperatures, which probably contributed to the differences in leaf retention. We were careful to try to harden off the trees both inside and outside by reduced watering in late summer.
Throughout the winter we were challenged to be able to get the snow off of the roof of the high tunnels due to the distance to the peak of the roof and difficulty with the accumulated snow on the sides of the tunnels that you had to stand in order to use the snow rake on the roof. We eventually were able to find a snow rake that was long enough and sturdy enough to do the job.
The tunnels were checked regularly throughout the winter for snow buildup and damage. Both tunnels made it through the winter without any major damage. The straw used for winter insulation inside the tunnels caused some pest issues early in the spring and was removed promptly. Vole traps and poison were set in the tunnels in early May. Both tunnels had thawed and were extremely wet in early May. All plant covers were removed from inside tunnels and in exterior plots mid May. The end walls were also removed in early June. Tunnels were tightened and anchors were secured as needed. Repairs were made as needed.
Drip irrigation was installed to both tunnels and one exterior plot. 1” poly pipe was used for the main and ¾“ for the sub main. Each tree received a foot and a half of micro tubing, which contained two inline 1/2gal per hour emitters. Trees were watered twice weekly for one hour until
September when watering was tapered and eventually stopped mid month. Exterior plots received additional rainfall throughout the summer.
Tunnels and plots were weeded and tilled daily and weekly as needed. The entire site was tilled once a month with a tractor. Cover crops were planted in neighboring fields in order to reduce weeds inside the trial area.
Trees and other plants
Apple trees that did not survive the winter were removed and replaced. Buds broke on a few trees inside the tunnel in late May. Some hornets and small flies were seen inside the tunnels throughout the summer. All trees were fertilized in late May. Trees received 113g of a 10-10-10 organic fertilizer from Peace of Mind. Pear, plum, and cherry trees were also planted inside the tunnels (see map).
The following berries were planted both inside and outside tunnels (see maps):
Scientific Name Variety
(Red Currant) Cherry Red
(Black Currant) Black September
Lonicera caerulea var. edulis
(Honey Berry) Blue Bird, Blue Sky, Blue
Rubus arcticus L. subsp. X stellarcticus
Arctic Raspberry Anna, Sophia, Beta, Valen-tine
Sea Berry Baikal, Male Sea Berry, Orange
Delight, Siberian Splendor, Sunny
The following additional fruit trees were planted in the high tunnels only:
Pyrus pyrifolia Raja P. Bet. , Seuri OHXF 513
Prunus x domestica Bavay’s Gage, Shropshire Damson
Prunus avium Crown Jewel, Crimson Passion
Plant materials were obtained from Dan Elliott (Wasilla, AK) and One Green
World (Molalla, OR).
(Refer to the trial planting maps)
Data Collection: (Refer to data summaries and graphs)
We collected climate data from inside one high tunnel and one of the exterior plots starting in October of 2007. We are measuring the following parameters:
– Air temperature
– Soil temperature (between 5-10 inches deep)
– Relative humidity
– Solar radiation
– Photosynthetic Active Radiation
– Soil moisture
– Wind speeds and gusts
Loggers collect data every hour. Batteries were replaced in the fall and repairs were made as needed.
- Survival Data
Survival data were collected in mid May. Our highest survivors overall included the following varieties. We anticipate these varieties to become leading candidates for testing in rural sites. We found that the outside plots had 68% survival and the high tunnel plots had 80% survival.
Altaiaski Sweet 6/1
Arctic Red 8/0
Golden Uralian 6/1
Heyer 12 8/0
Heyer 20 5/2
Lee 17 5/2
Nova Skibirski 6/1
Prairie Magic 5/3
Prairie Sun 5/2
Red Heart 6/2
Apples were harvested in early to mid September. They were weighed and sugar contents were measured with a refractometer (see chart below). Eleven trees produced apples for harvesting after 14 months from planting.
Winter Preparations (2008-09)
Winter preparations will be similar to last year’s preparations. Ends will be put on and tunnels will be sealed with plastic sheeting as done the previous winter. Trees inside the tunnels will be insulated with reflective insulation material and all replacement trees will be covered with treepees (tree covers) and tree guards (vole protection). Newly planted replacement trees in the exterior plots will be covered as well. Winter temperatures and snowfall will be monitored throughout the winter.
Apple crop images from the SARE project for the summer of 2008.
Monthly Average Temperature Comparisons and Significant Events –
Exterior and Interior Plots: January – May 2008
Month Exterior Exterior High Tunnel High Tunnel
Soil (10 cm) Air Soil (10 cm) Air
January 19.7 -5.9 9.6 2.3
February 20.5 -2.2 9.7 4.8
March 24 18 24.1 21.8
April 33 32.9 34.1 35.1
May 50.1 49.5 53.1 53.3
Significant events : Flowering began on May 28th in the high tunnels.
Exterior Plots –
Air Temperature March 7th was the first date when the exterior air tem-perature was recorded above 320 F.
Soil Temperature April 23rd was the first date when the soil temperature was recorded above 320 F.
High Tunnel Plots –
Air Temperature March 7th was the first date when the High Tunnel air temperature was recorded above 320 F.
Soil Temperature March 7th was the first date when the High Tunnel soil temperature was recorded above 320 F.
Impacts and Contributions/Outcomes
2008 Accomplishments and 2009 Expectations
Results from the SW06-111 trial this past year proved to be very encouraging both for the number of varieties that survived and the 11 trees that then produced fruit. It was a good winter for testing with a minimum exterior temperature of -47F and about 16 inches of snow on the ground. Tree survival in the exterior plots was 68% compared to the 80% survival in the interior plots. We found that the growth of the trees in the high tunnels was dramatically greater than that found in the exterior plots. The trees in general appeared to be very healthy heading into the second winter and we anticipate excellent survival again. We are especially excited about the potential for this coming year fruit crop and hope to substantially increase fruit yields. Through use of careful monitoring of site conditions, we have confidence in being able to recommend varieties that likely would be capable of surviving similar conditions in rural communities. In addition to the monitoring the trial through next summer we are intending to develop an educational document that will summarize the management procedures we used with both the exterior plots and those within the high tunnels. We believe that this trial has great potential to showcase cold tolerant varieties and culturing treatments that can open new doors for successful fruit tree production with rural cold sites in Interior Alaska.
122 First Avenue, Ste 600
Fairbanks, AK 99701
Office Phone: 9074528251