Monitoring Impacts of High Tunnels on Growing Conditions and Season Extension in Southcentral Alaska

View the project final report

• 2014 annual report

Commodities

• Fruits: melons, apples, apricots, berries (other), berries (blueberries), figs, grapes, peaches, pears, plums, berries (strawberries)
• Vegetables: artichokes, asparagus, beans, beets, broccoli, cabbages, carrots, cauliflower, celery, cucurbits, eggplant, garlic, greens (leafy), leeks, lentils, onions, parsnips, peas (culinary), peppers, radishes (culinary), rutabagas, sweet corn, tomatoes, turnips, brussel sprouts
• Additional Plants: herbs, ornamentals

Practices

• Crop Production: continuous cropping, irrigation, multiple cropping
• Education and Training: farmer to farmer, networking, on-farm/ranch research, participatory research, technical assistance
• Pest Management: prevention, weather monitoring
• Production Systems: general crop production
• Sustainable Communities: infrastructure analysis, local and regional food systems, partnerships, public participation, social networks

Since 2010, the United States Department of Agriculture has funded more than 150 producers with high tunnels in the Homer District through the Natural Resources Conservation Service (NRCS). This concentration of funded high tunnels is greater than anywhere else in the United States to date. Our area of Southcentral Alaska, the most populated region in the state, is home to over 15,000 people in nearly a dozen small communities (not counting Kodiak Island). We are at the literal “end of the road,” and it is critically important that we increase food security through development of local sustainable agricultural opportunities. The NRCS High Tunnel Program is providing local producers with an opportunity to maximize production and extend the short growing season in this maritime sub-Arctic region.

High tunnels are generally thought to add two to four weeks to a growing season; however, there has been little research done in coastal Alaska to ground-truth or better understand this assumption largely developed in the Lower 48 states. In addition, high tunnels respond to outside conditions and within often have far different microclimates for growing. Daily fluctuations in temperature and humidity, and how those relate to and are different from outside conditions, are added components of production and management facing farmers with high tunnels. Climate in the Homer area is dominated by cool and wet summers, with dramatic microclimatic differences in temperature and precipitation at varying elevations. Preliminary air temperature data collected during spring 2011 showed nighttime air temperatures inside our single-layer high tunnel up to 5 degrees (F) colder than outside ambient air temperatures as late as May 30. We speculate this was the result of increase humidity and evaporative cooling within the tunnel; however, more data are needed to understand the relationship between inside and outside temperatures and the effects of humidity when utilizing high tunnels on the farm.

With funding extended for the NRCS High Tunnel Program through 2013, we are seeing a rapid increase in the use of high tunnels in the Homer area. We believe there is a considerable need for engaging producers in a coordinated effort to better understand, and thus maximize, the potential of this concentrated agricultural system in our region. Through this project, we will employ temperature and humidity data loggers to understand the effects of high tunnels on growing conditions and season extension at different elevations (from sea level to 1,500 feet) in coastal Southcentral Alaska. We will also work with producers to understand the benefits of double-layer versus single-layer polyethylene HT covers in the region.

With the funding from Western SARE, we will increase the utility of high tunnels for the management and maximization of the growing season and for season extension in this region of Alaska through the collection, analysis, distribution and community discussion of soil temperature, air temperature and relative humidity data. Area farms range in elevation from sea-level to over 1,500 feet. Producers utilize both single- and double-layer polyethylene covers for increased heating potential, and a variety of methods for humidity control are used, including roll-down sides, solar-powered vents and electric fans. Through this project, we will identify producers to work with at different elevations and with diverse high tunnel glazing methods. Every participating farm will employ temperature and relative humidity data loggers inside and outside of their tunnel, following consistent protocols developed by the Technical Advisory and Principal Investigator and reviewed by the participating producers.

During the first year of this project, Kyra Wagner (producer, Sustainable Homer) will spearhead the development of an innovative High Tunnel website which will provide space for all local producers to enter environmental data they have on their high tunnels, including temperature and humidity data from private weather stations, as well as site-specific crop variety information and reviews. This website will include information on HT manufacturers, with reviews on durability and strength from local producers with experience in this challenging region for building. All analyzed data from this Western SARE-funded project will be included on the HT website, with additional outreach through the Homer High Tunnel Facebook group (as of November 2011 this group has 128 members), annual in-person meetings and annual reports written for and distributed to the local agricultural community. This project will provide the agricultural community an unprecedented amount of local data to better guide farming efforts and maximize limited resources.

Objective 1. Establish a baseline of data for air temperature, soil temperature and relative humidity effects of high tunnels at representative elevations in the Lower Kenai Peninsula of Alaska.

During summer 2012, the Technical Advisor and Principle Investigator will develop protocols for deploying soil and air temperature loggers and relative humidity loggers inside and outside of high tunnels at 12 farms representing different elevations around the Lower Kenai Peninsula. Farms will be identified at this time to meet sampling needs established during protocol development. Rachel Lord and Kyra Wagner personally know dozens of high tunnel owners in the Homer-area, and through current communication channels are in touch with many more. Among these farms, a subset of 10 (using Rachel's and Kyra’s HTs as two additional locations) will represent ideal locations for data logger placement. Data loggers will be deployed in fall 2012, prior to freezing, and will remain in place for the duration of the project (three years). Data will be uploaded at periodic intervals, at least once per year, preferably in the fall prior to freezing. All participating producers will be asked to take notes on standardized data sheets throughout the duration of the project on weather events, production, etc. Each winter, beginning in 2012-2013, the PI will post the raw data online and will analyze the data for maximum and minimum temperatures, fluctuation in humidity levels and relationships between in- and out-temperatures (both soil and air) and humidity levels. Tunnels from different elevations will be compared for elevation effects on season extension. Results from data analysis will be posted online and distributed through the HT website (see Objective 3). The annual meeting, held each winter of the project (2012-13, 2013-14, and 2014-15) will include discussion between producers on the results, with conclusions and suggestions for future work summarized and posted on the website following each meeting.

Objective 2. Begin to understand the effects of single- versus double-layer polyethylene high tunnel covers on soil temperature, air temperature and relative humidity in this region.

Participating producers have high tunnels with either single- or double-layer polyethylene covers. During the initial deployment of data loggers in fall 2012, both types of high tunnel covers will be equally represented by local farms (ideally six with single-layer and six with double-layer polyethylene covers). Each year of data will be analyzed to better understand the differences between these high tunnel cover options on soil temperature, air temperature and relative humidity. Other factors, such as humidity-control efforts, will be taken into account during data analysis. Similar outreach will be done as Objective 1, and all efforts from this project will tie into the third Objective.

Objective 3. Educate and engage the agricultural community of established and new local producers in order to maximize the potential of high tunnels in this region using local data.

During 2012-2013, Kyra Wagner will work to develop a High Tunnel website for regional producers. Using data collected through this project, we will facilitate annual winter meetings to engage producers in conversations that will grow the understanding of high tunnel impacts on local season extension for various crops. The HT website will include not only data collected through this project but also an online format for individuals to enter environmental data and crop variety and feedback data from their farms. This collection of site-specific information will be unprecedented in Alaska and will allow for existing and new producers to maximize their efficiency by the sharing of regionally-specific knowledge. Rachel Lord will also present at the Alaska SARE conference during the third year of this project in order to further spread the awareness of this website, results from this project, and to engage producers throughout Alaska to participate and enter environmental data from their high tunnels.