Consumer awareness of the environment and sustainability has increased in recent years. Market research shows that consumers are increasingly willing to pay premium prices for environmentally friendly products (Behe et al., 2010; Lopez et al., 2009, 2011). Commercial greenhouse operations that produce organic or sustainable crops have a new niche or specialty crop market.
As more greenhouse producers consider implementing organic production practices, questions arise about the use of organic media, fertilizers, and pest management methods for greenhouse crops. Organic media are available in the market, and pest management practices using organic pesticides and biological control agents are being established. However, cultural information about using organic fertilizers in a commercial greenhouse operation lags behind that available for other management areas. Specifically, information about the different organic fertilizers available in the market and their effects on plant growth and quality and substrate pH and electrical conductivity (EC) in comparison with inorganic fertilizers is needed.
Many organic fertilizers are byproducts of livestock, fish, food, and other processing industries (Gaskell and Smith, 2007). Some common materials used as organic fertilizer sources include fishmeal or fish powder, processed fish residues, feather meal, blood meal, meat and bone meal, and manure-based materials (Gaskell et al., 2006; Hartz and Johnstone, 2006).
Fish fertilizers are made from waste products of the ocean-fish processing industry. Fish fertilizers supply mostly NH4-N (Cox, 2010), which could be a disadvantage for some plants. Also, fish fertilizers can be a problem to store because they spoil and can be difficult to inject through some systems (Cox, 2010). Neptune’s fish hydrolysate 2-4-1 is the most commonly available fish fertilizer (Cox, 2010), and it is approved by the Organic Materials Review Institute (OMRI) for organic greenhouses (OMRI, 2012).
Some organic fertilizers are derived from residues (meals) of oilseeds such as soybean or from extracts during processing of oil from the seeds (Nelson et al., 2012). Among these fertilizers, some are OMRI-approved for organic use. Some soybean-based commercial preparations supply nutrients derived from inorganic salts and therefore are not OMRI-approved for organic use.
Other organic fertilizers are derived from alfalfa plants, in which the plant material (leaves) is dehydrated and pelletized (Fasina et al., 1997).
Although organic fertilizers are available in the market, little information is available on their performance, their influence on plant growth and quality, or their N leaching characteristics. Therefore, the objective of this work was to evaluate liquid fish, oilseed extract, and alfalfa pellets, used either alone or in combination, for plant growth and N leaching from two commonly grown floricultural crops, marigold (Tagetes erecta L. ‘First Lady’) and calibrachoa (Calibrachoa ×hybrida Llave & Lex ‘Million Bells Cherry Red’). Calibrachoa was particularly useful in this study because of its high fertility and acidic pH requirements and its tendency to demonstrate nutritional problems (Dole et al., 2002).
Argo, W.R. & Fisher, P.R. 2002 Understanding pH management for container-grown crops. Meister Publishing, Willoughby, OH
Bailey, D.A. & Nelson, P.V. 1998 Managing micronutrients in the greenhouse. NCSU Hort. Info. Leafl. 553
Bennett, W.F. 1994 Nutrient deficiencies and toxicities in crop plants. Amer. Phytopath. Soc., St. Paul, MN
Bi, G., Evans, W.B., Spiders, J.M. & Witcher, A.L. 2010 Effect of organic and inorganic fertilizers on marigold growth and flowering HortScience 45 1373 1377
Bunt, A.C. 1988 Media and mixes for container-grown plants. 2nd Ed. Unwin Hyman, London, UK
Cavins, T.J., Whipker, B.E., Fonteno, W.C., Harden, B., McCall, I. & Gibson, J.L. 2000 Monitoring and managing pH and EC using the pourthru extraction method. NCSU Hort. Info. Leafl. 590
Dole, J.M., Williams, A., Gibson, J.L., Whipker, B.E., Nelson, P.V., Cleveland, B.R. & Walls, F.R. 2002 Nutrient deficiencies of calibrachoa. 16 Apr. 2013. <http://wwvv.ces.ncsu.edu/dpts/hort/floriculture/deficalibrachoa.htm>
Ellis, B.W. 1999 Taylor’s guide to annuals. Houghton Mifflin Co., Boston, MA
Fisher, P.R., Wik, R.M., Smith, R.R., Pasian, C.C., Kmetz-Gonzalez, M. & Argo, W.A. 2003 Correcting iron deficiency in calibrachoa grown in a container medium at high pH HortTechnology 13 308 313
Gaskell, M., Smith, R., Mitchell, J., Koike, S.T., Fouche, C., Hartz, T., Horwath, W. & Jackson, L. 2006 Soil fertility management for organic crops. UC Publ. Bull. l7249
Issac, R.A. & Johnson, W.C. Jr 1998 Elemental determination by inductively coupled plasma atomic emission spectrophotometry, p. 165–170. In: Kalra, Y.P. (ed.). Handbook of reference methods for plant analysis. CRC Press, Boca Raton, FL
LaLiberte, K. 2013 When to water. 16 Apr. 2013. <http://www.gardeners.com/When-to-Water/8108,default,pg.html>
Lopez, R., Dennis, J., Behe, B., Hall, C., Yue, C. & Campbell, B. 2011 Demand for sustainability, Part 2: What are growers doing about sustainability? Greenhouse Grower 29 32 36
Lopez, R.G., Dennis, J.H., Camberato, D.M., Smith, J.T., Behe, B. & Hall, C. 2009 Consumer perceptions of sustainably produced poinsettias. Greenhouse Grower. 16 Apr. 2013. <http://www.greenhousegrower.com/article/11990/consumer-perceptions-of-sustainably-produced-poinsettias>
Mills, H.A. & Jones, J.B. 1996 Plant analysis handbook II. MicroMacro Publ., Inc., Athens, GA
OMRI 2012 OMRI product list. Crop fertilizers and soil amendments. Organic Materials Review Institute. 16 Apr. 2013. <http://www.omri.org/sites/default/files/opl_pdf/crops_category.pdf/>
Robbins, J.A. & Evans, M.R. 2010 Growing media for container production in a greenhouse or nursery, part II (physical and chemical properties). 16 Apr. 2013. <http://www.uaex.edu/Other_Areas/publications/PDF/FSA-6098.pdf/>
Römheld, V. 1987 Existence of two different strategies for the acquisition of iron in higher plants, p. 445–476. In: Winkehnann, G., D. van der Helm, and J.B. Neilands (eds.). Iron transport in microbes, plants and animals. VCH Verlagsges, Weinheim, Germany
SAS Institute Inc 2002 SAS/STAT user’s guide, version 9.1 for Windows. SAS Institute, Inc., Cary, NC
Scoggins, H.L. & van Iersel, M.W. 2006 In situ probes for measurement of electrical conductivity of soilless substrates: Effects of temperature and substrate moisture content HortScience 41 210 214
Sonneveld, C. 1990 Estimating quantities of water soluble nutrients in soils using a specific 1:2 by volume extract Commun. Soil Sci. Plant Anal. 21 1257 1265
Steel, R.G.D. & Torrie, J.H. 1980 Principles and procedures of statistics. McGraw-Hill, New York, NY