Fuel Type and Releasing the Heated Air near Plant Roots Reduced Production Cost of Greenhouse Tomatoes

A study was conducted to determine the effects of a constructed interplant bottom heating system using diesel fuel and an above-plant heating system using natural gas on heating and production cost of greenhouse tomatoes (Lycopersicon esculentum). Two identical greenhouses of size 30 x 96-ft were used for this study. The interplant bottom-heated greenhouse consumed an average of 195,790,000 Btu during the heating period (January- March) to raise the air temperature 5 ft above the floor to the optimum level for greenhouse tomato production. The above-plant-heated greenhouse consumed an average of 208,100,000 Btu to do the same. Using the interplant bottom heating system reduced energy consumption by 6%. Average cost was $6.22 and $9.10 per million Btu from diesel fuel and natural gas, respectively. The difference is approximately a 32% reduction in fuel cost based on fuel type. The interplant bottom heating system raised root-media temperature to near the optimum level for tomato growth and increased total yield by 9.5%. Producing 1 lb of tomatoes in the interplant bottom-heated greenhouse required 13,266 Btu at a heating cost of $0.08; however it required 15,459 Btu in the above-plant-heated greenhouse at a heating cost of $0.14. Less energy, cost-effective fuel, and increased yield reduced heating cost per production unit by 43% in the interplant bottom-heated greenhouse.