Note: NEXUS is an STBE collaborative research site.
The Nexus team continues its work designing and evaluating technological solutions to extend the growing season for small-scale farmers in Southern Appalachia. The team will soon complete the second year of an on-farm pilot of two systems, one at Springhouse Farm and one at Against the Grain (ATG) Farm in the High Country area. This year’s work contributes additional evidence that effectively designed root zone heating systems can reduce fossil fuel consumption for greenhouse heating while maintaining productive growing conditions. Springhouse Farm used 30% less propane in 2019, even though heating degree days were only 100 less than the previous year. Additionally, the team reports exciting preliminary evidence that biochar improves the anaerobic digestion process. Preliminary data from bench scale tests of goat dairy feedstocks indicate that the addition of biochar stabilizes the rate of gas production, reduces retention time and increases total biogas production. The team has been busy this year, and these findings keep them excited and bode well for local farmers looking to increase production sustainably. Read more technical detail below.
The second year of the pilot system operation at partner farms
We started the second year of the pilot by upgrading bench covers to retain warmth and reduce heat loss. Growing bench covers were built using 6 mil polyethylene attached with zippers, Velcro, and magnetic strips for easy opening and closing. The germination bench cover at Springhouse farm was built using 8mm polycarbonate twin-wall panels which have twice the R value of 6 mil polyethylene. This upgrade supports improved germination by maintaining a consistent soil temperature (Fig 1).
Following these improvements at Springhouse Farm, air temperatures inside the growing and germination bench covers exceeded greenhouse air temperatures by 10 °F and 20 °F, respectively. As a result, the greenhouse space heater was not needed during Springhouse’s winter season, indicating that the root zone heating system with improved covers will perform well even without space heating. When greenhouse and outside air temperatures were lowest (31°F and 15°F, respectively), the system maintained soil temperatures of ~43°F on the growing bench without bottom insulation, 52°F on the growing bench with bottom insulation, and 73 °F on the germination bench. On the same night, the water on the table without cover and root zone heating was frozen (Fig 2). When the root zone heating system at Against The Grain (ATG) Farm was running, air temperature inside the vertical rack cover exceeded greenhouse air temperature by as much as 15°F.