Appropriate timing and concentration of nutrient supply in vegetative cutting propagation affects root development, uniformity of plant growth, uptake efficiency [(nutrient taken up/total nutrient applied-nutrients in substrate)*100], nutrient runoff, and transplant success. Root development can be divided into four stages: 1) cutting condition at “sticking” (insertion) into substrate; 2) callus formation; 3) root development; and 4) toning (Dole and Gibson, 2006). Fertigation recommendations for vegetative cuttings are currently correlated with root developmental stages with a recommended initial application of 50 to 75 mg N/L at visible callus development (Stage 2) and subsequent applications of 100 mg N/L after root emergence (i.e., during Stage 3) (Dole and Gibson, 2006). Nutrient availability in the substrate becomes particularly important for uptake at Stage 3 after root emergence. Nutrients can be supplied to vegetative cuttings through a combination of preplant dry fertilizers in the substrate, supplemental application of water-soluble fertilizer, and/or incorporation of controlled-release fertilizers. Historically, fertilization through overhead mist was not recommended for short-term crops as a result of the potential for clogged emitters and algae growth (Dole and Gibson, 2006).
Based on a survey of eight U.S. commercial greenhouses, the concentration of fertilizer solutions applied during the propagation of vegetative petunia and calibrachoa cuttings ranged from 0.5 to 80 and 64 to 158 mg·L−1 N for 7 and 28 d after sticking into substrate, respectively (Santos et al., 2008). Timing of fertigation varied from constant application of N for 28 d to application of N 14 d after sticking (Santos et al., 2008). The variation in observed practices at these operations suggests that the current recommended fertilization strategies may need to be refined with further consideration of fertilizer timing and N concentration.
Mist irrigation is intended to maintain cutting turgidity during root development and often water is supplied in excess of evapotranspiration loss and container capacity (representing the volume of water held in a drained substrate) resulting in the potential for rapid leaching of fertilizer (Kerr and Hanan, 1985; Mudge, 1995; Santos et al., 2008). Propagators surveyed leached as much as 46 L·m−2 in a 4-week crop cycle and six of eight operations leached over one container capacity during the same period (Santos et al., 2008). Nutrient leaching as a consequence of mist application during propagation is significant because soilless substrates have a limited ability to retain nutrients, especially when total leaching rates are greater than one container capacity (Biernbaum et al., 1995; Kerr and Hanan, 1985). During Stages 1 and 2 of root development, the loss of nutrients from leaching could deplete the substrate of nutrients by Stage 3 (root emergence), a critical stage for nutrient replenishment for the cutting. Therefore, commercial fertilizer application early in propagation before root formation may be required to recharge leached nutrients from the substrate. Water-soluble fertilizer applications before root emergence may also facilitate foliar uptake of nutrients (Tukey et al., 1958) and reduce observed tissue nutrient declines during preliminary phases of propagation (Svenson and Davies, 1995; Wilkerson and Gates, 2005).
Timing the supply of fertilizer to meet plant requirements at different root developmental stages has the potential to increase uptake efficiency and reduce nutrient runoff. Macronutrients, in absolute terms, are required in higher quantities compared with micronutrients only. Therefore, plant response to macronutrient supply is of particular interest before significant root growth (Phases 1 and 2 of rooting). The objective of this research was to evaluate the effect of timing of macronutrient supply on growth and nutrient uptake of petunia cuttings at 0 to 7, 8 to 14, and 15 to 21 d after sticking, in which these time periods correspond to mist fertigation during callus and root initial formation from Days 0 to 7 followed by hand fertigation during the root growth phase from Days 8 to 21.
Biernbaum, J.A., Argo, W.R., Weesies, B., Weesies, A. & Haack, K. 1995 Persistence and replacement of preplant nutrient charge fertilizers from highly leached peat-based root media HortScience 30 763
Blazich, F.A. 1988 Mineral nutrition and adventitious rooting 61 69 Davis T.D., Hassig B.E. & Sankhla N. Adventitious root formation in cuttings Dioscorides Press Portland, OR
Clor, M.A., Crafts, A.S. & Yamaguchi, S. 1963 Effects of high humidity on translocation of foliar-applied labeled compounds in plants part: I Plant Physiol. 38 501 507
Dole, J.M. & Gibson, J.L. 2006 Cutting propagation: A guide to propagating and producing floriculture crops 1st Ed Ball Publishing Batavia, IL
Gibson, J.L., Pitchay, D.S., Williams-Rhodes, A.L., Whipker, B.E., Nelson, P.V. & Dole, J.M. 2007 Nutrient deficiencies in bedding plants: A pictorial guide for identification and correction Ball Publishing Batavia, IL
Good, G.L. & Tukey H.B. Jr 1967 Leaching of metabolites from cuttings propagated under intermittent mist J. Amer. Soc. Hort. Sci. 89 727 733
Mills, H.A. & Jones J.B. Jr 1996 Plant analysis handbook. II: A practical sampling, preparation, analysis, and interpretation guide MicroMacro Publishing Athens, GA
Mudge, K.W. 1995 Comparison of four moisture management systems for cutting propagation of bougainvillea, hibiscus, and kei apple J. Amer. Soc. Hort. Sci. 120 366 373
Rowe, D.B. & Blazich, F.A. 1999 Mineral nutrient and carbohydrate status of loblolly pine during mist propagation as influenced by stock plants nitrogen fertility HortScience 32 1279 1285
Santos, K.M., Fisher, P.R. & Argo, W.R. 2008 A survey of water and fertilizer management during cutting propagation HortTechnology 18 597 604
Scoggins, H.L., Bailey, D.A. & Nelson, P.V. 2002 Efficacy of the press extraction method for bedding plant plug nutrient monitoring HortScience 37 108 112
Svenson, S.E. & Davies F.T. Jr 1995 Change in tissue mineral elemental concentration during root initiation and development of poinsettia cuttings HortScience 30 617 619
Tukey H.B. Jr, Tukey, H.B. & Wittwer, S.W. 1958 Loss of nutrients by foliar leaching as determined by radioisotopes Proc. Amer. Soc. Hort. Sci. 71 496 506
Wilkerson, E.G. & Gates, R.S. 2005 Transpiration capacity in poinsettia cuttings at different rooting stages and the development of cutting coefficient for scheduling mist J. Amer. Soc. Hort. Sci. 130 295 301