Greenhouses are typically heated during the winter to maintain markets or to start plants early enough to meet spring consumer demand. Growers must decide which greenhouses to minimally heat and which to maintain at higher temperatures to meet market demands. Coupled with this decision is choosing the extent of insulation to install and gaps to seal, which will reduce air infiltration. Air infiltration can lead to a great deal of heat loss, but greenhouses that are sealed too tightly could have high humidity, inadequate air supply for heater intake or exhaust (Giacomelli and Roberts, 1993), and reductions in the atmospheric CO2 concentrations.
The drawdown of CO2 in a closed system is an often ignored issue and in some instances, can lead to plant growth problems. Measurements as low as 175 ppm CO2 inside greenhouses have been recorded (Frantz and Schmidlin, 2009), and CO2 concentrations are commonly 300 to 330 ppm (390 ppm atmospheric or outside), even in well-ventilated greenhouses. This drawdown in CO2 has been used in laboratory settings to document photosynthesis in the day time (Wheeler, 1992). It is not widely appreciated how quickly this drawdown can occur since many assume that greenhouses, even those that are well sealed and insulated, leak enough to maintain adequate CO2 for plant growth.
An option in counteracting potential CO2 drawdown in greenhouses is to supply supplemental CO2. A recent review describes many of the options and costs associated with different CO2 supplementation systems (Blom et al., 2009). Sustainable production practices have increased in recent years in greenhouse systems (Dennis et al., 2010), but it is unknown how the use of supplemental CO2 fits within the framework of sustainable controlled agriculture. In this study, the use of supplemental CO2 was explored in combination with reduced temperatures. The objective was to compare lettuce growth within a low-temperature greenhouse supplemented with CO2 against lettuce growth within a more traditional warm, well-insulated greenhouse, without CO2 injection. This experiment was combined with simulations using Virtual Grower software (Frantz et al., 2010) that compared cost, fuel use, and C consumed because of heating and CO2 supplementation between the two greenhouses.
Aldrich, R.A. & Bartok, J.W. Jr 1994 Greenhouse environment 61 72 Sailus M., Napierala C. & Sanders M. Greenhouse engineering Publ. 33. Natural Resource Agr. Eng. Serv. Publ. Ithaca, NY
Blom, T.J., Straver, W.A., Ingratta, F.J., Khosla, S. & Brown, W. 2009 Carbon dioxide in greenhouses Ontario Ministry Agr Factsheet 00-077
Dennis, J.H., Lopez, R.G., Behe, B.K., Hall, C.R., Yue, C. & Campbell, B.L. 2010 Sustainable production practices adopted by greenhouse and nursery plant growers HortScience 45 1232 1237
Frantz, J.M., Hand, B., Buckingham, L. & Ghose, S. 2010 Virtual Grower: Software to calculate heating costs of greenhouse production in the U.S HortTechnology 20 778 785
Frantz, J.M., Cometti, N.N. & Bugbee, B. 2004 Night temperature has a minimal effect on the growth and respiration and rapidly growing plants Ann. Bot. (Lond.) 94 155 166
Frantz, J.M. & Schmidlin, D. 2009 Using supplemental CO2 in tightly sealed greenhouses to offset growth and development decreases in cool production environments FloriBytes Digital Nwsl. 4 3 9 11
Goudriaan, J. & Monteith, J.L. 1990 A mathematical function for crop growth based on light interception and leaf area expansion Ann. Bot. (Lond.) 66 695 701
Jie, H. & Kong, L.S. 1998 Growth and photosynthetic responses of three aeroponically grown lettuce cultivars (Latuca sativa L.) to different rootzone temperatures and growth irradiances under tropical aerial conditions J. Hort. Sci. Biotechnol. 73 173 180
Korczynski, P.C., Logan, J. & Faust, J.E. 2002 Mapping monthly distribution of daily light integrals across the contiguous United States HortTechnology 12 12 16
Long, S.P. 1991 Modification of the response of photosynthetic productivity to rising temperature by atmospheric CO2 concentrations: Has its importance been underestimated? Plant Cell Environ. 14 729 739
Lopez, R.G. & Runkle, E.S. 2004 The effect of temperature and leaf and flower development and flower longevity of Zygopetalum Redvale ‘Fire Kiss’ orchid HortScience 39 1630 1634
Monteith, J.L. 1977 Climate and the efficiency of crop production in Britain Philosophical Trans. Royal Soc. London Ser. B 281 277 294
Thompson, H.C., Langhans, R.W., Both, A.J. & Albright, L.D. 1998 Shoot and root temperature effects on lettuce growth in a floating hydroponic system J. Amer. Soc. Hort. Sci. 123 361 364
U.S. Department of Commerce 2011 Global monitoring division observatory operations 3 Jan. 2011. <http://www.esrl.noaa.gov/gmd/obop/>.