Application of electric carbon crystal soil-warming system for tomato production in greenhouse

Abstract: The soil temperature is one of the most important and direct factors for vegetables, but it was often below the optimum growing temperature of vegetables in a Chinese solar greenhouse during the winter. There are some warming facilities in a greenhouse such as a warming cable, warm air oil furnace, water or ground-source heat pump and traditional coal-fired boiler but their installation cost or power consumption are priced beyond an affordable level. An electric carbon crystal soil-warming system, a new warming device applied in winter heating for civil architecture, was introduced and redesigned into solar greenhouse tomato production in this experiment. A carbon crystal board was fully buried, half buried and laid flat on the top of substrate (not buried) to heat the 10 cm-depth-substrate to or over 17 ℃. The soil and air temperature, the amount of growth, some physiological characteristics such as root activity etc., production of tomato and power consumption were detected.The results showed that the electric warming facilities, including electric carbon crystal soil-warming system and warming cable, significantly (P<0.05) enhanced the soil temperature, but had no influence on air temperature. Differences of soil temperature fields between the electric carbon crystal soil-warming system and warming cable were quite obvious as the result of their different heating area. Root activity and leaf photosynthetic rate of tomatos were improved remarkably by both the whole buried method and warming cable. Moreover, the early and total yields of tomato by the whole buried method were 38.7% and 28.2% higher than those of CK respectively. However, the tomato yield of half-buried and no-buried method had no difference from those of CK. Comparing with the energy consumption，the whole buried method is better than warming cable because the level of tomato production was enhanced the highest and its power consumption was 25.1% lower than those of warming cable. But nowadays, the installation cost of an electric carbon crystal soil-warming system equals twice cost of warming cable. Both the electric carbon crystal soil-warming system and warming cable share a higher running cost than heating by the traditional coal-fired boiler. There is also a promising prospect for the electric carbon crystal soil-warming system to applied in protected vegetable production because of its outstanding energy saving and cost-reduction with the technology innovation.