Using high tunnels to provide peony with a longer growing season to increase productivity in northern latitudes and cold soils
The purpose of this experiment is to evaluate growth and productivity of herbaceous peonies growing with and without late-season high tunnels. The peonies are growing on cold permafrost soils on a north-facing slope. We anticipate that high tunnels will warm soil and air temperatures, promote soil drying and provide an environment that will maximize plant growth and productivity on marginal sites. By extending the growing season, we expect there to be more carbohydrate storage in the roots and a more vigorous plant the following year.
The high tunnel experiment consists of six plots, with three replicates under high tunnels and three replicates not covered. Each plot of ‘Sarah Bernhardt’ peonies (at least 30 plants) are planted in raised beds with double rows, 18 inches between plants and between rows. Each replicate consists of two double rows, 28 feet long separated by a two foot aisle. There is at least a 10-foot buffer between treatments to minimize effects of high tunnels on adjacent plots. Rows are irrigated using thin wall trickle tape irrigation when necessary, but in 2012 we did not irrigate at all. Fertilization consists of 20-20-20 broadcast in the spring and 8-32-16 broadcast in the fall, at a rate determined by the soil test taken each fall. Plots are hand-weeded as needed. Roundup is used in areas with no peony plants. In 2012, it was determined the pH was dropping so ½ ton per acre of lime was broadcast on all plots.
Identify the value of using high tunnels in field grown peony production.
To meet this objective we will:
1. Monitor soil and air temperatures both inside and outside of high tunnels to determine impacts and optimum uses of high tunnel technology. Tunnels will be erected in an existing peony field during the spring of 2010. Data loggers will be added at the same time.
2. Determine spring emergence dates for plants inside and outside the high tunnels to determine if plant emergence timing is affected. Emergence dates will be recorded for plants in plot areas. This will be done over three growing seasons. Currently plants emerge over a three to four week time span.
3. Determine if increased growing days are possible with the use of high tunnels, especially extending into the fall. Data collection will include visual inspection for frost-damaged vegetation, and data loggers will record air temperature on an hourly basis over the growing season.
4. Determine if there is increased plant survival and vigor with the use of the high tunnels. Data collection will consist of pictures and counting the number of stems in the plot area before harvest over three growing seasons.
5. Determine if there is increased flower production with the use of high tunnels. Marketable flowers will be counted in plot areas over three seasons.
6. Monitor diseases by sampling and doing surveys in plot areas.
In 2012, the high tunnels were covered in late May. Preliminary data suggested the plot areas were very wet when compared to other peony fields in Alaska. As a result, we decided to use the high tunnels to dry out those plot areas by heating the soil in the spring and keeping the rain off. The tunnel-covered plots remained covered but with the sides up to facilitate air movement and cooler temperatures until August, when the sides were dropped to keep those plots from being affected by an early frost. The cover was removed in September and straw mulch was put on all plots. Tunnels will be re-covered in spring 2013 as soon as the field is dry enough to work in.
Data on soil and air temperature, soil moisture, relative humidity, PAR and rainfall was collected using Hobo weather station (Onset Computer) recorded hourly throughout the year. Data on plant growth was collected: date of stem emergence, growth rate and number of buds. No buds were harvested due to the small size of the plants. Biomass samples were collected from five plants per plot at the time high tunnel covers were removed for the winter.
We downloaded data collected by the Hobo dataloggers on September 8. We collected our sample plants and took them to the university to be dried and have the plant dry weight from those plants for three growing seasons. There is no significant difference in the development of these plants whether in a high tunnel or not. However, all plants are getting bigger, which is of course what we want. We hosted a farm workday for peony growers and others interested in farming on September 22, 2012. We showed how our high tunnels were constructed and rolled up the plastic so others could see how we closed it up for the winter. Then we applied straw and explained how we mulch and what benefits we expect from doing mulching. Thirty-two people attended our workday.
Impacts and Contributions/Outcomes
It appears that the growing degree days are increased by putting plants under a high tunnels. Whether that is enough to get our plants to thrive on the cold wet soils we have remains to be seen. If there is a difference, we hope it shows more in 2013, as the high tunnels will have been up and covered for two growing seasons. It is possible there are other factors limiting growth such as nutrients, pH and moisture. We continue to work to monitor and modify those factors. Since there is no data on what are the best practices are for fertilization, that part remains a learning opportunity.
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Polar Peonies, LLC
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