The use of a recirculating subirrigation system is becoming increasingly popular in the greenhouse industry. In a survey on the status of nutrient solution recirculation in Ontario, Canada, Richard et al. (2006) found that almost half of the surveyed vegetable greenhouses and 30% of the ornamental crop greenhouses were recycling their nutrient solution. The use of recirculating subirrigation systems has been adopted for many reasons, including environmental, social, and economical benefits. In 2002, the government of Ontario introduced the Nutrient Management Act to regulate the discharge of nutrients and pesticide pollution and reduce water consumption (Ontario Ministry of Agriculture, Food and Rural Affairs, 2007). The use of a recirculating subirrigation system allows growers to comply with the Nutrient Management Act because it lowers nutrient and water requirements. It also allows for nutrients to be delivered in a uniform manner, avoids foliar wetting to reduce disease incidence, offers greater flexibility in pot sizing and spacing, and reduces the discharge of nutrients to surrounding ecosystems. These benefits can lead to savings in labor, material input, and product losses (Richard et al., 2006; Uva and Weiler, 1998).
Subirrigation, however, leads to salt accumulation at the substrate surface, which is a major drawback to the practice (Argo and Biernbaum, 1996; Kent and Reed, 1996; Morvant et al., 1997; Zheng et al., 2004a, 2005). In subirrigation, salts are not leached out of the containers like in overhead irrigation; as a result, water evaporates from the surface of the growing substrate leaving behind fertilizer salts on the top layers of the growing substrate causing salt accumulation (Zheng et al., 2004a, 2005). Salt concentration can quickly reach toxic levels resulting in visible damage in crops. This problem is further exacerbated by high fertilizer application rates (Zheng et al., 2004a, 2005).
Commercial greenhouse growers typically use high nutrient concentrations in an attempt to maximize crop yield, but this practice is not an economically optimized production strategy because excessive nutrients do not always result in higher crop yields (Zheng et al., 2004a, 2005). Siddiqi et al. (1998) showed that macronutrient concentrations, commonly used by commercial greenhouse tomato growers, can be reduced by 50% without having any adverse effect on growth, fruit yield, and fruit quality of tomato plants. For NFT lettuce production, Chen et al. (1997) showed that current nutrient concentrations can be reduced by up to 99% without having any adverse effect on growth and rates of nutrient uptake.
Our prior research (Zheng et al., 2004a, 2005) has shown that nutrient solution concentrations for potted gerbera production can be safely reduced by at least 50% without adversely affecting crop production over a 4- to 5-week period; however, many plants (such as miniature roses) may be subirrigated for up to 10 weeks before they are ready for the market (Beytes and Hamrick, 2003). The objectives of the present study were to: 1) determine the optimum feeding nutrient concentration for greenhouse potted miniature rose production; and 2) to profile vertical salt distribution within subirrigated growing substrate in the pot over the production period.
Argo, W.R. & Biernbaum, J.A. 1995 The effect of irrigation method, water-soluble fertilization, preplant nutrient charge, and surface evaporation on early vegetative and root growth of poinsettia J. Amer. Soc. Hort. Sci. 120 163 169
Argo, W.R. & Biernbaum, J.A. 1996 Availability and persistence of macronutrients from lime and preplant nutrient charge fertilizers in peat-based root media J. Amer. Soc. Hort. Sci. 121 453 460
Chen, G.X., Gastaldi, C., Siddiqi, Y.M. & Glass, M.D. 1997 Growth of a lettuce crop at low ambient nutrient concentrations: A strategy designed to limit the potential for eutrophication J. Plant Nutr. 20 1403 1417
James, E.C. & van Iersel, M.W. 2001 Fertilizer concentration affects growth and flowering of subirrigated petunias and begonias HortScience 36 40 44
Kang, J.G. & van Iersel, M.W. 2002 Nutrient solution concentration affects growth of subirrigated bedding plants J. Plant Nutr. 25 387 403
Kent, M.W. & Reed, D.W. 1996 Nitrogen nutrition of New Guinea impatiens ‘Barbados’ and Spathiphyllum ‘Petite’ in a subirrigation system J. Amer. Soc. Hort. Sci. 121 816 819
Mak, A.T.Y. & Yeh, D.M. 2001 Nitrogen nutrition of Spathiphyllum ‘sensation’ grown in sphagnum peat- and coir-based media with two irrigation methods HortScience 36 345 349
Morvant, J.K., Dole, J.M. & Allen, E. 1997 Irrigation systems alter distribution of roots, soluble salts, nitrogen and pH in the root medium HortTechnology 7 156 160
Ontario Ministry of Agriculture and Food 2003 Production Recommendations for Greenhouse Floriculture Publ. 370. Queen's Printer for Ont Toronto, Canada
Ontario Ministry of Agriculture, Food and Rural Affairs 2007 Act: Nutrient Management Act <http://www.omafra.gov.on.ca/english/nm/nasm/non_ag/municipal_op.htm>.
Siddiqi, Y.M., Kronzucker, J.H., Britto, T.D. & Glass, A.D.M. 1998 Growth of a tomato crop at reduced nutrient concentrations as a strategy to limit eutrophication J. Plant Nutr. 21 1879 1895
Uva, W.L. & Weiler, T.C. 1998 A survey on the planning and adoption of zero runoff subirrigation systems in greenhouse operations HortScience 33 193 196
Warncke, D.D. & Krauskopf, D.M. 1983 Greenhouse growth media: Testing and nutrient guidelines Mich. State. Univ. Coop. Ext. Ser. Vul E-1736
Yelanich, V.M. & Biernbaum, J.A. 1990 Effect of fertilizer concentration and method of application on media nutrient content, nitrogen runoff and growth of Euphorbia pulcherrima V-14 Glory Acta Hort. 272 185 189
Zheng, Y., Graham, T., Richard, S. & Dixon, M. 2004a Potted gerbera production in a subirrigation system using low-concentration nutrient solutions HortScience 39 1283 1286
Zheng, Y., Wang, L. & Dixon, M. 2004b Response to copper toxicity for several ornamental crops in solution culture HortScience 39 1116 1120
Zheng, Y., Graham, T., Richard, S. & Dixon, M. 2005 Can low nutrient strategies be used for pot gerbera production in closed-loop subirrigation? Acta Hort. 691 365 372