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

Project Overview

FW12-046
Project Type: Farmer/Rancher
Funds awarded in 2012: $19,615.00
Projected End Date: 12/31/2015
Region: Western
State: Alaska
Principal Investigator:
Rachel Lord
Alaska Stems (formerly Harambee Gardens)

Annual Reports

Information Products

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

    Summary:

    High tunnels are generally considered 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. Climate in the Homer area is dominated by cool and wet summers, with dramatic microclimatic differences in temperature and precipitation at varying elevations. Air and soil temperature and relative humidity data were collected hourly inside and outside of 10 high tunnels around Homer, Alaska. Based on our data, we do not see support for the idea that high tunnels alone in this area add two to four weeks of growing season. Season extension activities should likely be concentrated in the fall; and, regardless, some additional heat source or other temperature control methods (low tunnels, row cover, etc) likely must be employed to protect crops from cold temperatures. Moisture control in the fall is also a challenge that must be addressed. Our data do suggest; however, that high tunnels alone provide a great amount of season ‘enhancement’ – increasing the growing degree days an average of 2,000 over field conditions. In our coastal, sub-arctic climate this is a huge advantage and collective experiences have anecdotally confirmed faster growth rates and increased yields of certain crops. Farmers at higher elevations will likely see greater positive impacts from double-poly tunnels; however, added heat retention is likely greater and when using additional heat double-poly tunnels are likely advantageous regardless of the elevation.

    Introduction

    Since 2010, the United States Department of Agriculture has funded the construction of over 200 high tunnels in the Homer District through the Natural Resources Conservation Service (NRCS). The Homer District covers the southern Kenai Peninsula and Kodiak Island, all within the southcentral region of Alaska. This is one of the highest concentrations of NRCS-funded high tunnels in the nation. The southern Kenai Peninsula is home to over 15,000 people in nearly a dozen small communities. We are at the literal “end of the road,” and growers and families are increasingly interested in questions of food security and the development of local sustainable agricultural opportunities. Many feel that the NRCS High Tunnel Program is providing local producers with an opportunity to extend the short growing season in this maritime sub-Arctic region.

    High tunnels are generally considered 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. Climate in the Homer area is dominated by cool and wet summers, with dramatic microclimatic differences in temperature and precipitation at varying elevations.

    The NRCS is continuing to fund the high tunnel program and their numbers are consistently increasing in the Homer area. We believe there is considerable benefit to taking advantage of this dense concentration of high tunnels to collect regionally-specific and publically-available information to help engage and inform producers and growers at all scales. Through this project, we employed temperature and humidity data loggers and collected data in 10 high tunnels to understand the effects of high tunnels on growing conditions at different elevations (from sea level to 1,500 feet) and with single- or double-poly glazing in coastal southcentral Alaska. We also developed a website specifically for high tunnel owners around the state of Alaska to share and disseminate information.

    Project objectives:

    We had three primary objectives going into this project:

    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.

    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.

    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.

    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.