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.
BaileyD.A.NelsonP.V.2004Designing 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>.
BjerregårdA.HansenM.1983Oversigt over jordanalyser p. 110. In Jord vand næring. ed. Gartnerinfo Copenhagen
BostT.2014Carolinas getting started garden guide: Grow the best flowers shrubs trees vines & groundcovers. Cool Spring Press Minneapolis MN
BroschatT.K.Klock-MooreA.2000Root and shoot growth responses to phosphate fertilization in container-grown plantsHortTechnology10765767
CaradusJ.R.SnaydonR.W.1987Aspects of the phosphorus nutrition of white clover populations. I. Inorganic phosphorus content of leaf tissueJ. Plant Nutr.10273285
CaradusJ.R.van den BoschJ.WoodfieldD.R.MackayA.C.1991Performance of white clover cultivars and breeding lines in a mixed species sward. 1. Yield and clover contentN. Z. J. Agr. Res.34141154
DufaultR.J.SchultheisJ.R.1994Bell pepper seedling growth and yield following pretransplanting nutritional conditioningHortScience299991007
EpsteinE.BloomA.J.2005Mineral nutrition of plants: Principles and perspectives. 2nd ed. Sinauer Associates Sunderland MA
FöhseD.ClaassenN.JungkA.1988Phosphorus efficiency of plants. I. External and internal P requirement and P uptake efficiency of different plant speciesPlant Soil110101109
GoodA.G.ShrawatA.K.MuenchD.G.2004Can less yield more? Is reducing nutrient input into the environment compatible with maintaining crop production?Trends Plant Sci.9597605
HansenC.W.LynchJ.1998Response to phosphorus availability during vegetative and reproductive growth of chrysanthemum: II. Biomass and phosphorus dynamicsJ. Amer. Soc. Hort. Sci.123223229
HavisJ.R.BakerJ.H.1985Phosphorus requirement of Rhododendron ‘Victor’ and Cotoneaster adpressa grown in a perlite-peat mediumJ. Environ. Hort.36364
HuangC.Y.ShirleyN.GencY.ShiB.LangridgeP.2011Phosphate utilization efficiency correlates with expression of low-affinity phosphate transporters and noncoding RNA, IPS1, in barley. 2011Plant Physiol.156312171229
HuangC.Y.RoessnerU.EickmeierI.GencY.CallahanD.L.ShirleyN.LangridgeP.BacicA.2008Metabolite profiling reveals distinct changes in carbon and nitrogen metabolism in phosphate-deficient barley plants (Hordeum vulgare L.)Plant Cell Physiol.49691703
HuntR.1990Basic growth analysis. Unwin Hymin London UK
KimH.J.LynchJ.P.BrownK.M.2008Ethylene insensitivity impedes a subset of responses to phosphorus deficiency in tomato and petuniaPlant Cell Environ.3117441755
LynchJ.UäuchliA.EpsteinE.1991Crop physiology and metabolism. Vegetative growth of the common bean in response to phosphorus nutritionCrop Sci.31380387
LynchJ.BrownK.2006Whole plant adaptations to low phosphorus availability p. 209–242. In: B. Huang (ed.). Plant-environment interactions Taylor & Francis Boca Raton FL
MajsztrikJ.C.RistveyA.G.Lea-CoxJ.D.2011Water and nutrient management in the production of container-grown ornamentalsHort. Rev.38253296
MarschnerH.2012Mineral nutrition of higher plants. 3rd ed. Academic Press San Diego CA
NelsonP.1996Macronutrient fertilizer programs. In: D.W. Reed (ed.). Water media and nutrition for greenhouse crops. Ball Publ. Batavia IL
RistveyA.G.Lea-CoxJ.D.RossD.S.2007Nitrogen and phosphorus uptake efficiency and partitioning of container grown azalea during spring growthJ. Amer. Soc. Hort. Sci.132563571
RoseT.J.WissuwaM.2012Rethinking internal phosphorus utilization efficiency (PUE): A new approach is needed to improve PUE in grain cropsAdv. Agron.116185217
RoseT.J.RengelZ.MaQ.BowdenJ.W.2007Differential accumulation patterns of phosphorus and potassium by canola cultivars compared to wheatJ. Plant Nutr. Soil Sci.170404411
SnappS.S.LynchJ.P.1996Phosphorus distribution and remobilization in bean plants as influenced by phosphorus nutritionCrop Sci.36929935
VanceC.P.Uhde-StoneC.AllanD.L.2003Phosphorus acquisition and use: Critical adaptations by plants for securing a non renewable resourceNew Phytol.157423447
VeneklaasE.J.LambersH.BraggJ.FinneganP.M.LovelockC.E.PlaxtonW.C.PriceC.A.ScheibleW.ShaneM.W.WhiteP.J.RavenJ.A.2012Opportunities for improving phosphorus-use efficiency in crop plantsNew Phytol.195306320
WarnckeD.D.KrauskopfD.M.1983Greenhouse growth media: Testing and nutrition guidelines. Mich. State. Univ. Coop. Ext. Bul. E-176
WhitcherC.L.KentM.W.ReedD.W.2005Phosphorus concentration affects New Guinea impatiens and vinca in recirulating subirrigationHortScience4020472051
WilliamsK.A.NelsonP.V.1996Modifying a soilless root medium with aluminum influences phosphorus retention and chrysanthemum growthHortScience31381384
YeagerT.H.WrightR.D.1982Phosphorus requirement of Ilex crenata Thunb. cv. Helleri grown in a pine bark mediumJ. Amer. Soc. Hort. Sci.107558562