In 2013, the U.S. green industry generated $136.44 billion in direct output, of which $16.77 billion were contributed by greenhouse and nursery growers (Hodges et al., 2015). To produce high-quality, uniform, and consistent products, commercial floriculture greenhouses and nurseries apply irrigation and fertilization at a high frequency, thus, potentially leading to the contamination of ground and surface water (Richards and Reed, 2004). Reducing volume or frequency of irrigation would not only save water, but could also reduce the greenhouse production time and costs by reducing water-related energy, labor, fertilizer, pesticides, growth regulators, and overhead costs, thus increasing sustainability (Lichtenberg et al., 2013). Also, studies show that plants with more sustainable attributes positively affect consumer preferences (Behe et al., 2013; Hall et al., 2010).
The portion of crops grown but considered unsalable is termed shrinkage. The later the shrinkage occurs in the value chain, the larger the impact it has on profitability because more inputs such as overhead, labor, water, fertilizer, and pesticides have been used before plants are thrown away. A recent survey of larger growers reported that production level shrink ranged from 2% to 10%, with a median of 5%, whereas retail-level shrink ranged from 8% to 33%, with a median of 19% (Hall et al., 2011). Leaf and flower senescence and flower abscission induced by ethylene or water deficit during shipping and shelf life causes the plant to lose its esthetic value, another cause of postharvest shrinkage for bedding and potted plants (Starman et al., 2007). Inadequate irrigation is a major challenge during postproduction (shelf life) because irrigation systems are almost never ideal in retail environments because of untrained personnel or understaffing.
Nemali and van Iersel (2006) developed a sensor-based automatic irrigation system to reduce irrigation water usage by maintaining distinct and constant SMC levels throughout the production period. By controlling the timing and length of lower SMC level, a controlled water deficit was applied to potted floral plants. Using controlled water deficit irrigation during greenhouse production could not only reduce water input and increase plant water use efficiency (WUE), but also increase plant quality by producing a more compact plant without applying a plant growth regulator. Applying water at a consistent 20% SMC during greenhouse production of angelonia (A. angustifolia) ‘Angelface Blue’ produced a more compact crop because of shorter internodes, and reduced or prevented wilting during the water deficit postproduction period, thus increasing plant postproduction quality. This consistent water deficit throughout angelonia production also increased the WUE (Jacobson et al., 2015). Similar results were reported for poinsettia (Euphorbia pulcherrima). A constant 20% SMC was also an effective alternative shoot height control method compared with plant growth retardant (daminozide, B-Nine) application during poinsettia greenhouse production (Alem et al., 2015).
The objective of this study was to determine the effect of water deficit using two levels of SMC applied by the dry-down method during greenhouse production on angelonia and heliotrope growth and physiological parameters. The dry-down method used in this study was conducted by irrigating to container capacity (CC) when the target SMC level was indicated by the sensor reading. The root substrate was dried back down to the target SMC and re-watered to CC repeatedly as needed throughout the experiment. We also studied the effects on postproduction performance during simulated retail conditions. Lastly, we examined the effects on associated economic costs. Our hypothesis was that lower SMC during greenhouse production would lower irrigation costs, better acclimate plants for the retail environment, and allow plants to maintain higher quality during postproduction.
Alem, P., Thomas, P. & van Iersel, M. 2013 Irrigation volume and fertilizer concentration effects on leaching and growth of petunia Acta Hort. 1034 143 148
Alem, P., Thomas, P.A. & van Iersel, M.W. 2015 Controlled water deficit as an alternative to plant growth retardants for regulation of poinsettia stem elongation HortScience 50 565 569
Álvarez, S., Navarro, A., Nicolás, E. & Sánchez-Blanco, M.J. 2011 Transpiration, photosynthetic responses, tissue water relations and dry mass partitioning in Callistemon plants during drought conditions Scientia Hort. 129 306 312
Bayer, A., Mahbub, I., Chappell, M., Ruter, J. & van Iersel, M.W. 2013 Water use and growth of Hibiscus acetosella ‘Panama Red’ grown with a soil moisture sensor-controlled irrigation system HortScience 48 980 987
Bayer, A., Ruter, J. & van Iersel, M.W. 2015 Automated irrigation control for improved growth and quality of Gardenia jasminoides ‘Radicans’ and ‘August Beauty’ HortScience 50 78 84
Begg, J. 1980 Morphological adaptations to water stress, p. 33–42. In: N.C. Turner and P.J. Kramer (eds.). Adaptation of plants to water and high temperature stress. Wiley Interscience, New York, NY
Behe, B.K., Campbell, B.L., Hall, C.R., Khachatryan, H., Dennis, J.H. & Yue, C. 2013 Consumer preferences for local and sustainable plant production characteristics HortScience 48 200 208
Cormier, M., Prentice-Hudson, E., Irving, C., Marcshall, S., Burvill, M., Balchin, A., Laplante, J., Henri, T. & Brecker, G. 2011 Plant varieties journal. Can. Food Inspection Agency. 18 Mar. 2018. <http://publications.gc.ca/collections/collection_2011/inspection/A27-13-78-eng.pdf>
Fonteno, W., Hardin, C. & Brewster, J. 1995 Procedures for determining physical properties of horticultural substrates using the NCSU porometer. Hort. Substrates Lab., N.C. State Univ., Raleigh, NC
Hall, C., Jones, M.L., Starman, T., Pasian, C. & Staby, G. 2011 Shrink the shrink. Greenhouse Mgt. 18 Mar. 2018. <http://www.greenhousemag.com/article/greenhouse-0111-shrink/>
Hall, C.R., Campbell, B.L., Behe, B.K., Yue, C., Lopez, R.G. & Dennis, J.H. 2010 The appeal of biodegradable packaging to floral consumers HortScience 45 583 591
Hodges, A.W., Hall, C.R., Palma, M.A. & Khachatryan, H. 2015 Economic contributions of the green industry in the United States in 2013 HortTechnology 25 805 814
Hsiao, T.C. & Xu, L.K. 2000 Sensitivity of growth of roots versus leaves to water stress: Biophysical analysis and relation to water transport J. Expt. Bot. 51 1595 1616
Jacobson, A.B., Starman, T.W. & Lombardini, L. 2015 Substrate moisture content effects on growth and shelf life of Angelonia angustifolia HortScience 50 272 278
LeBude, V.A. & Bilderback, E.T. 2009 The pour-through extraction method: A nutrient management tool for nursery crops. N.C. State Univ. Coop. Ext. Bul. AG-717-W
Lichtenberg, E., Majsztrik, J. & Saavoss, M. 2013 Profitability of sensor-based irrigation in greenhouse and nursery crops HortTechnology 23 770 774
Martínez, D. & Guiamet, J. 2004 Distortion of the SPAD 502 chlorophyll meter readings by changes in irradiance and leaf water status Agronomie 24 41 46
Monneveux, P. & Belhassen, E. 1996 The diversity of drought adaptation in the wild, p. 7–14. In: E. Belhassen (ed.). Drought tolerance in higher plants: Genetical, physiological and molecular biological analysis. Springer, Dordrecht, The Netherlands
Nemali, K.S. & van Iersel, M.W. 2006 An automated system for controlling drought stress and irrigation in potted plants Scientia Hort. 110 292 297
Niu, G., Rodriguez, D.S. & Mackay, W. 2008 Growth and physiological responses to drought stress in four oleander clones J. Amer. Soc. Hort. Sci. 133 188 196
Niu, G., Rodriguez, D.S., Rodriguez, L. & Mackay, W. 2007 Effect of water stress on growth and flower yield of big bend bluebonnet HortTechnology 17 557 560
Niu, G., Rodriguez, D.S. & Wang, Y.T. 2006 Impact of drought and temperature on growth and leaf gas exchange of six bedding plant species under greenhouse conditions HortScience 41 1408 1411
Richards, D.L. & Reed, D.W. 2004 New Guinea impatiens growth response and nutrient release from controlled-release fertilizer in a recirculating subirrigation and top-watering system HortScience 39 280 286
Sakazaki, U. 2011 Heliotrope plant named ‘USHTRP0303’. United States Patent Application. 18 Mar. 2018. <https://patents.google.com/patent/USPP21681P2/en>
Starman, T. & Lombardini, L. 2006 Growth, gas exchange, and chlorophyll fluorescence of four ornamental herbaceous perennials during water deficit conditions J. Amer. Soc. Hort. Sci. 131 469 475
Starman, T.W., Beach, S.E. & Eixmann, K.L. 2007 Postharvest decline symptoms after simulated shipping and during shelf life of 21 cultivars of vegetative annuals HortTechnology 17 544 551
Taiz, L., Zeiger, E., Møller, I.M. & Murphy, A. 2015 Plant physiology and development. Sinauer Assoc., Inc., Sunderland, MA
Wang, Q., Chen, J., Stamps, R.H. & Li, Y. 2005 Correlation of visual quality grading and SPAD reading of green-leaved foliage plants J. Plant Nutr. 28 1215 1225