Phosphorus is an essential nutrient for plant growth and reproduction. Intensive use of P fertilizers for crop production has led to eutrophication and deterioration of water quality, causing serious environmental concerns. P used in fertilizers is obtained from global phosphate rock reserves, and is a nonrenewable resource that could be depleted in 50–100 years (Marschner, 2012), and therefore, increasing the efficiency with which these reserves are used to produce crops is vital to maintain or increase crop productivity in current crop production systems (Cordell et al., 2009).
The major environmental impacts caused by horticulture operations include runoff that carries pollutants including P, which can be driven by overfertilization of P, excessive irrigation, or the use of soilless potting media with less ability to retain P than mineral soils (Whitcher et al., 2005; Yeager and Wright, 1982). Particularly, overfertilization of P has been a long-standing problem causing economic losses to farmers and negatively impacting environments. Conversely, insufficient P can lead to a loss of crop productivity and yield, and therefore, it is critical to precisely determine the P requirements of crops to ensure crop production and meet the growing environmental challenges.
A large number of studies have shown that early season P supply is critical for optimum crop yield of many field-grown crops (Grant et al., 2001), which might have led to the practice of providing P starter fertilizers for greenhouse and nursery crop production, and this practice is still common. Superphosphate is routinely incorporated into potting media followed by regular fertilization with either liquid fertilizer or controlled-release fertilizer containing P (Wright and Niemiera, 1987). Excessive concentrations of P have been applied for crop production during this practice, exaggerating the risk of P runoff to the environment. Little is known about optimum P rates for most greenhouse and nursery crop production (Bailey and Nelson, 2004; Warncke and Krauskopf, 1983), and therefore, P fertilizer has been applied far in excess of what is required to achieve high crop productivity. For example, in conventional horticultural production systems, plants are often grown with P concentrations ranging from 90 to 150 mg·L−1 to compensate for the lack of buffering capacity of soilless media (Bjerregård and Hansen, 1983; Williams and Nelson, 1996). Current application rates of P largely depend on nitrogen fertilizer recommendations. Due to a general perception that P stimulates root growth and helps the transplants to obtain a quick establishment, the application of fertilizers with low N:P ratios is still common (Broschat and Klock-Moore, 2000; Hansen and Lynch, 1998; Williams and Nelson, 1996). Alternatively, the fertilizers with a ratio of 2:1:2 are often recommended for commercial greenhouse crops (Nelson, 1996; Whitcher et al., 2005).
A few studies have been conducted to determine an optimum P concentration for container crop production (Wright and Niemiera, 1987). P applications of ≈10 mg·L−1 in the irrigation water have resulted in maximum growth of Ilex crenata (Yeager and Wright, 1982) and Chamaecyparis lawsoniana (Van der Boon, 1981), which was also true for the rooted cuttings of Rhododendron and Cotoneaster adpressus praecox (Havis and Baker, 1985). Meanwhile, maximum growth was achieved in Vinca and new guinea impatiens grown at P concentration around 20 mg·L−1 (Whitcher et al., 2005). Plant growth, biomass accumulation, and P dynamics can be affected during the transition from vegetative to reproductive growth as demonstrated in chrysanthemum (Hansen and Lynch, 1998). Therefore, plant growth stage should be considered when determining P requirement of a crop. Many additional factors can affect P requirement of the crop including growing media, and irrigation method and frequency (Majsztrik et al., 2011); however, it is important to define a baseline P concentration required for an optimum plant growth and the implications of such a baseline without interference with other factors.
The effects of P on root growth and root-to-shoot ratio present conflicting results among the studies on container crops. According to Harris (1992), authors of several publications state or imply that P fertilizations primarily stimulate root growth, while other studies reported that increasing P supply increased root growth but decreased root-to-shoot ratio (Hansen and Lynch, 1998; Kim et al., 2008; Lynch et al., 1991), or it had no effect on root growth or root-to-shoot ratio (Broschat and Klock-Moore, 2000; Dufault and Schultheis, 1994; Ristvey et al., 2007). Little is known about the P accumulation patterns and PUtE in container crops, and there are only a few reports on the effects of P fertilization on partitioning in relation to their productivity. Such information is critical as it will help design more efficient management strategies for P fertilizer by better aligning the P requirements of crops and the application amount and timing of the nutrient. An understanding of such relationships is important to determine sustainable management practices for P fertilization. The objective of this experiment was to critically analyze the effects of P on shoot and root growth, P partitioning, and PUtE in lantana (L. camara ‘New Gold’). Our results will aid in refining the effects of P on plant growth and flowering in ornamental crops, and establishing the best P management practices.
Bailey, D.A. & Nelson, P.V. 2004 Designing a greenhouse crop fertilization program. Department of Horticultural Sciences, North Carolina State University, Raleigh, NC. 1 Jan. 2013. <https://www.ces.ncsu.edu/depts/hort/floriculture/plugs/fertprog.pdf>.
Bjerregård, A. & Hansen, M. 1983 Oversigt over jordanalyser, p. 110. In Jord, vand, næring. ed. Gartnerinfo, Copenhagen
Bost, T. 2014 Carolinas getting started garden guide: Grow the best flowers, shrubs, trees, vines & groundcovers. Cool Spring Press, Minneapolis, MN
Broschat, T.K. & Klock-Moore, A. 2000 Root and shoot growth responses to phosphate fertilization in container-grown plants HortTechnology 10 765 767
Caradus, J.R. & Snaydon, R.W. 1987 Aspects of the phosphorus nutrition of white clover populations. I. Inorganic phosphorus content of leaf tissue J. Plant Nutr. 10 273 285
Caradus, J.R., van den Bosch, J., Woodfield, D.R. & Mackay, A.C. 1991 Performance of white clover cultivars and breeding lines in a mixed species sward. 1. Yield and clover content N. Z. J. Agr. Res. 34 141 154
Cote, B. & Dawson, J.O. 1990 Autumnal allocation of phosphorus in black alder, eastern cottonwood, and white basswood Can. J. For. Res. 21 217 221
Dufault, R.J. & Schultheis, J.R. 1994 Bell pepper seedling growth and yield following pretransplanting nutritional conditioning HortScience 29 999 1007
Epstein, E. & Bloom, A.J. 2005 Mineral nutrition of plants: Principles and perspectives. 2nd ed. Sinauer Associates, Sunderland, MA
Föhse, D., Claassen, N. & Jungk, A. 1988 Phosphorus efficiency of plants. I. External and internal P requirement and P uptake efficiency of different plant species Plant Soil 110 101 109
Good, A.G., Shrawat, A.K. & Muench, D.G. 2004 Can less yield more? Is reducing nutrient input into the environment compatible with maintaining crop production? Trends Plant Sci. 9 597 605
Grant, C.A., Flaten, D.N., Tomasiewicz, D.J. & Sheppard, S.C. 2001 The importance of early season phosphorus nutrition Can. J. Plant Sci. 81 211 224
Hansen, C.W. & Lynch, J. 1998 Response to phosphorus availability during vegetative and reproductive growth of chrysanthemum: II. Biomass and phosphorus dynamics J. Amer. Soc. Hort. Sci. 123 223 229
Havis, J.R. & Baker, J.H. 1985 Phosphorus requirement of Rhododendron ‘Victor’ and Cotoneaster adpressa grown in a perlite-peat medium J. Environ. Hort. 3 63 64
Huang, C.Y., Shirley, N., Genc, Y., Shi, B. & Langridge, P. 2011 Phosphate utilization efficiency correlates with expression of low-affinity phosphate transporters and noncoding RNA, IPS1, in barley. 2011 Plant Physiol. 156 3 1217 1229
Huang, C.Y., Roessner, U., Eickmeier, I., Genc, Y., Callahan, D.L., Shirley, N., Langridge, P. & Bacic, A. 2008 Metabolite profiling reveals distinct changes in carbon and nitrogen metabolism in phosphate-deficient barley plants (Hordeum vulgare L.) Plant Cell Physiol. 49 691 703
Hunt, R. 1990 Basic growth analysis. Unwin Hymin, London, UK
Kim, H.J., Lynch, J.P. & Brown, K.M. 2008 Ethylene insensitivity impedes a subset of responses to phosphorus deficiency in tomato and petunia Plant Cell Environ. 31 1744 1755
Lynch, J., Uäuchli, A. & Epstein, E. 1991 Crop physiology and metabolism. Vegetative growth of the common bean in response to phosphorus nutrition Crop Sci. 31 380 387
Lynch, J. & Brown, K. 2006 Whole plant adaptations to low phosphorus availability, p. 209–242. In: B. Huang (ed.). Plant-environment interactions, Taylor & Francis, Boca Raton, FL
Majsztrik, J.C., Ristvey, A.G. & Lea-Cox, J.D. 2011 Water and nutrient management in the production of container-grown ornamentals Hort. Rev. 38 253 296
Marschner, H. 2012 Mineral nutrition of higher plants. 3rd ed. Academic Press, San Diego, CA
Melton, R.R. & Dufault, R.J. 1991 Nitrogen, phosphorus, and potassium fertility regimes affect tomato transplant growth HortScience 26 141 142
Murphy, J. & Riley, J.P. 1962 A modified single solution method for the determination of phosphate in natural waters Anal. Chim. Acta 27 31 36
Nelson, P. 1996 Macronutrient fertilizer programs. In: D.W. Reed (ed.). Water, media and nutrition for greenhouse crops. Ball Publ., Batavia, IL
Ristvey, A.G., Lea-Cox, J.D. & Ross, D.S. 2007 Nitrogen and phosphorus uptake efficiency and partitioning of container grown azalea during spring growth J. Amer. Soc. Hort. Sci. 132 563 571
Rose, T.J. & Wissuwa, M. 2012 Rethinking internal phosphorus utilization efficiency (PUE): A new approach is needed to improve PUE in grain crops Adv. Agron. 116 185 217
Rose, T.J., Rengel, Z., Ma, Q. & Bowden, J.W. 2007 Differential accumulation patterns of phosphorus and potassium by canola cultivars compared to wheat J. Plant Nutr. Soil Sci. 170 404 411
Snapp, S.S. & Lynch, J.P. 1996 Phosphorus distribution and remobilization in bean plants as influenced by phosphorus nutrition Crop Sci. 36 929 935
Vance, C.P., Uhde-Stone, C. & Allan, D.L. 2003 Phosphorus acquisition and use: Critical adaptations by plants for securing a non renewable resource New Phytol. 157 423 447
Veneklaas, E.J., Lambers, H., Bragg, J., Finnegan, P.M., Lovelock, C.E., Plaxton, W.C., Price, C.A., Scheible, W., Shane, M.W., White, P.J. & Raven, J.A. 2012 Opportunities for improving phosphorus-use efficiency in crop plants New Phytol. 195 306 320
Warncke, D.D. & Krauskopf, D.M. 1983 Greenhouse growth media: Testing and nutrition guidelines. Mich. State. Univ. Coop. Ext. Bul. E-176
Whitcher, C.L., Kent, M.W. & Reed, D.W. 2005 Phosphorus concentration affects New Guinea impatiens and vinca in recirulating subirrigation HortScience 40 2047 2051
Williams, K.A. & Nelson, P.V. 1996 Modifying a soilless root medium with aluminum influences phosphorus retention and chrysanthemum growth HortScience 31 381 384
Yeager, T.H. & Wright, R.D. 1982 Phosphorus requirement of Ilex crenata Thunb. cv. Helleri grown in a pine bark medium J. Amer. Soc. Hort. Sci. 107 558 562