| In sub-Arctic regions, cold environmental conditions and a short growing season limit the production of many horticultural plant species. Due to these conditions, localized food production is limited, and rural communities in these areas are forced to depend on expensive food resources supplied from other environmental regions. To address this scenario, a research study was conducted that incorporated the principles of thermal conductivity to raise both soil and soil-surface atmospheric temperatures, and increase the number of frost-free days for horticultural-plant production.;In order to raise temperature, this study adapted radiant-energy technology utilized in the architectural industry to build a supplemental-thermal-energy system into the soil profile. Through a thermal-conductive process, thermal energy was moved from an artificial source upward into the soil and then into the soil-surface atmosphere, forming a thermal gradient to offset cold soil temperatures. Due to the high cost of energy, an important design factor was energy efficiency. Radiant-energy technology is energy efficient, and future designs can be modified to utilize energy (waste heat) produced in many rural communities, which would decrease costs even further.;A split-plot statistical design was used and three experiments were conducted extending the 2009 and 2010 horticultural plant-production season, located in Olnes, Alaska (Latitude: 65°4'28" N; Longitude: 147°36'44" W). In April 2010, the supplemental system was able to thaw and increase soil temperature for an early germination process for both a warm (jalapeno) and a cool (spinach) seasonal-horticultural plant species. Observations also show an unforeseen outcome from the indirect affects from the system, which increased temperature in plant-growing containers receiving no thermal-energy treatments during both seasonal extensions.;Experimental results show the potential of a 160 frost-free-day growing season. However, changing the design to be more flexible to daily environmental conditions could improve plant growth. An advantage of this system is its ability to utilize direct-seeding methods that allow for plant growth undisturbed from transplanting, which improves production. Results also show the potential to increase food production in sub-Arctic regions by improving plant growth for species naturally produced, and by introducing new horticultural plant species. |
