Using the Pour Through Nutrient Extraction Procedure in Prodi~iEtThob.; ..
Optimum Fertilizer Rates and Associated Leachate Electrical Conductivity levelss of
Twelve Foliage Plants fence

C.A. Conover and R.T. Poole and K. Steinkamp' p 3 o 1g

University of Florida, IFAS Jn!,ersity of Florida
Central Florida Research and Education Center Apopka
CFREC-Apopka Research Report RH-92-24


Since many foliage plants can be grown satisfactorily with a wide range of fertilizer
ates, the best fertilization rate, from an environmental and economic standpoint, cannot
Ways be determined by visual inspection. Even though excess fertilizer may not harm
ome plants, excess nitrogen (N) and phosphorous (P) ions can be lost through leaching and
eventually contaminate groundwater supplies. Growing regimes designed to have minimum
detrimental impact on the natural environment should include only enough fertilizer for good
ilant growth, combined with irrigation practices that limit or eliminate leachate formation.

Environmentally sound fertilization rates can be determined by monitoring growing
nedium electrical conductivity (EC) levels. Medium EC levels, except in cases where salty
irrigation water is used, are generally associated with fertilization rates (the higher the
ertilizer rate the higher will be the associated EC level). Electrical conductivity levels will
Iso rise when leaching is limited and plants are over-fertilized because plants are not
utilizing all the available ions.

This paper presents the results of several years of research with 12 foliage plants to
ind the lowest fertilization rates (and associated leachate electrical conductivity levels as
determined by the pour-through method) associated with production of high quality plants.
"he pour-through method was used to determine leachate electrical conductivity because it
.as been shown to be as satisfactory as other more expensive and time consuming methods of
measuring EC. Unlike sampling methods that require removal of medium from containers,
he pour-through method does not disturb plant roots, a major advantage when periodic
monitoring is done. As nurseries implement more environmentally and economically sound
;rowing regimes, the pour-through method should become more widely used by foliage
;rowers for self-determination of EC levels periodically during the crop production cycle.






'Professor of Environmental Horticulture and Center Director, Professor of Plant






..... materials and Methods

GREENHOUSE PRODUCTION: The nine genera grown under greenhouse conditions w
'Silver Queen' aglaonema [Aglaonema Schott. 'Silver Queen'], 'Apollo' zebra plant
[Aphelandra squarrosa Nees 'Apollo'], parlor palm [Chamaedorea elegans Mart.], 'Banan;
croton [Codiaeum variegatum (L.) Blume 'Banana'], dumb cane [Dieffenbachia maculata
(Lodd) G. Don 'Camille'], corn plant [Dracaenafragrans (L.) Ker-Gawl. 'Massangeana'],
compact boston fern [Nephrolepis exaltata (L.) Schott. 'Bostoniensis Compacta'], heart-lea
philodendron [Philodendron scandens oxycardium (Schott) Bunt.] and 'Petite' peace lily:
[Spathiphyllum Schott. 'Petite']. Liners obtained from local growers were planted into 6-
inch containers using Vergro Container Mix A (Canadian peat moss:coarse grade
vermiculite:perlite, 2-1-1 by volume, plus starter nutrient charge, (Verlite Company, Tamp
FL 33610). Plants were grown in glass greenhouses where they received 1500 or 2000 ft-i
maximum light intensity with air temperatures ranging from 68 to 95 F, depending on
season. Plants were watered overhead with tap water (pH-7.4, EC-0.3 millimhos/cm) as
needed to promote healthy growth. Containers were top-dressed with Osmocote 19-6-12
(Grace/Sierra Co. Milpitas, CA 95035) fertilizer, at 3-month intervals, at the ten rates sho\
in figures 1 through 9.

SHADEHOUSE PRODUCTION: Three genera grown under shadehouse conditions were
Norfolk Island pine [Araucaria heterophylla (Salisb.) Franco], areca palm [Chrysalidocarpi
lutescens H. Wendl] and 'Warneckii' dracaena [Dracaena deremensis Engl. 'Warneckii'].
Seedlings of Norfolk Island pine and Areca palm and rooted cuttings of 'Warneckii' dracae
were potted into 8-inch pots, three per container. Growing medium used for shadehouse
production was composed of Florida sedge peat:pine bark:builders' sand in a ratio of 6:3:1
v/v, amended with 7 lbs/yd3 dolomite and 1 lb/yd3 Micromax (micronutrient blend






Plants were grown for a time sufficient for-production of a gooc
like zebra plant and compact Boston fern, were "finished" or re
'he whilb nthpre nnrh ar-en nflm and Nnrfnile Tinand ninp w,


WH \YILUL b~YYI
rl:L-- ---^t^tl^


shed" (haqed on n


Aglaonema 'Silver Queen'. Salable plants were produced at the
results indicate a rate near 7.2 g/6-inch pot/3-months would yield hi
i excellent roots (Fig. 1). Plants fertilized at higher rates received 1I
les. Root and plant grades of aglaonemas were highly correlated.
millimhos/cm are indicative of excess fertilizer application.

Aphelandra squarrosa 'Apollo'. 'Apollo' zebra plants with goot






U- LeeffeRLncniU mIUCutu LaIln1C rerunzauUi aLt +. g/O-l
duced 'Camille' dieffenbachia with highest quality foliage and rc
lity 'Camille' dieffenbachia were grown with rates ranging from


zer, which elevate


oducine EC leve


if 7.2 g/6-inch pot/3-months and the ma
illimhos/cm) is recommended to reduce
quality plants.


Nephrolepis exaltata
24 g/6-inch pot/3-months h,
with the lowest rate tested,
3. 01 However. suggested 1


'ompi
Id comp
3 A -1/A


Lcta compact boston fern plan
arable root and shoot grades (Fi
inch nnt/l-mnnthc wprp incal h


needed amounts.


;rades when tertil:


root and plant gr2


Araucaria heterophylla. Norfolk Island pines grew best with 12
months (Fig. 10) and increasing fertilizer rate beyond that level produce


- -- -- -- ---


' '
a






nts. An EC level near 1.0 millimhos/cm was associated with fe
el and is suggested.


for soluble salt tolerant plants as tertillzer rates increase. wnen plants
higher than optimum rates, the unused fertilizer accumulated in the grove
elevated EC levels. Some of the foliage plants that grew well only whe
range of fertilization rates were those that are known to be intolerant of

These results confirm for some growers what they already know.
crops at an unnecessarily high rate and relying on frequent medium leac
soluble salts buildup. Extra fertilizer is still viewed by many as an "insi
guaranteeing a fast growing, good looking crop. Since fertilizer expend
ahnut 1% of total nrtiifction costs- these erowine regimes can remain n


suggested fertilizer rate in the text against the rate you are applying and ;
No. 1 for rates producing high quality acclimatized foliage plants; 2) Che






ECQ-evels of crops in your nursery against levels shown here to determine if you are
applying too much fertilizer.

Further Reading

1. Conover, C.A. and R.T. Poole. 1990. Light and fertilizer recommendations for
production of acclimatized potted foliage plants. Nrsy. Dig. 24(10):34-36, 58-59.

2. Hipp, B.W., D.L. Morgan, and D.Hooks. 1979. A comparison of techniques for
monitoring pH of growing medium. Commun. Soil Sci. Plant Anal. 10:1233-1238.

3. Poole, R.T. and A.R. Chase. 1986. Growth of six ornamental plants and soluble
salts of the growing media. Proc. Fla. State Hort. Soc. 99:278-280.

4. Poole, R.T. and A.R. Chase. 1987. Response of foliage plants to fertilizer
application rates and associated leachate conductivity. HortScience 22(2):317-318.

5. Poole, R.T. and C.A. Conover. 1990. Leachate electrical conductivity and pH for
ten foliage plants. J. Environ. Hort. 8(4):166-172.

6. Wright, R.D. 1986. The pour-through nutrient extraction procedure. HortScience
21(2):227-229.

7. Yeager, T.H., R.D. Wright and S.J. Donohue. 1983. Comparison of pour-through
and saturated pine bark extract N,P,K, and pH levels. J. Amer. Hort. Sci.
108(1):112-114.







Fig 1. Aglaonema 'Silver Queen'
Plant & root quality vs. soluble salts


millimhos/cm


0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6
FERTILIZER RATE (g 19-6-12/6" pot/3 mos)
Plants grown for 6 months


Fig 2. Aphelandra squarrosa
Plant & root quality vs.

Quality Grade


'Apollo'
soluble salts

millimhos/cm


4-
4 aU- a - -- ^ ^



3 -

2 -
/ G Plant Quality
1 oot Quality
-- Soluble Salts
01 --I
0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6
FERTILIZER RATE (g 19-6-12/6" pot/3 mos)
Plants grown for 3 months






Fig 3. Chamaedorea elegans
Plant & root quality vs. soluble salts


Quality Grade


millimhos/cm


0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6 24
FERTILIZER RATE (g 19-6-12/6" pot/3 mos)
Plants grown for 7 months



Fig 4. Codiaeum variegatum 'Banana'
Plant & root quality vs. soluble salts


Quality Grade
(after 2 months in interiors)








Soluble salts ta
just prior to
placing plant in interiors


millimhos/cm


0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6
FERTILIZER RATE (g 19-6-12/6" pot/3 mos)
Plants grown for 6 months in ghse


Plant Quality
Root Quality
Soluble Salts
I


I I


I


i I L ; i






Fig 5. Dieffenbachia maculata 'Camille'
Plant & root quality vs. soluble salts

Quality Grade millimhos/cm
11



4 8-
7

3- 6
5
2- -4
Plant Quality 3
1 Root Quality 2
Soluble Salts 1
0 I 0
0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6 24
FERTILIZER RATE (g 19-6-12/6" pot/3 mos)
Plants grown for 3 months



Fig 6. Dracaena fragrans 'Massangeana'
Plant & root quality vs. soluble salts

Quality Grade millimhos/cm


4- 05

-4
3
3

2-
-2
SPlant Quality
1 Root Quality 1
Soluble Salts
0 I - - I I 0
0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6 24
FERTILIZER RATE (g 19-6-12/6' pot/3 mos)
Plants grown for 4 months







Fig 7. Nephrolepis exaltata 'Compacta'
Plant & root quality vs. soluble salts


Quality Grade


O L '
0 2.4 4.8 7.2
FERTILIZER
Plants grown for 3 months


9.6
RATE


millimhos/cm


12 14.4 16.8 19.2 21.6
(g 19-6-12/6" pot/3 mos)


Fig 8. Philodendron scandens oxycardium
Plant & root quality vs soluble salts


Quality Grade


millimhos/cm


Plant Quality
SRoot Quality
SSoluble Salts


0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6 24
FERTILIZER RATE (g 19-6-12/6" pot/3 mos)
Plants grown for 3 months


I I I


I






Fig 9. Spathiphylium 'Petite'
Plant & root quality vs soluble salts


0 2.4 4.8 7.2 9.6 12 14.4 16.8 19.2 21.6-' 24
FERTILIZER RATE (g 19-6-12/6" pot/3 mos)
Plants grown for 6 months


Fig 10. Araucaria heterophylla
Plant quality vs. soluble salts

Quality Grade millimhos/cm


0 4.1 8.2 12.2 16.3 20.4 24.5 28.6 32.6 36.7 40.8 45
FERTILIZER RATE (g 19-6-12/8" pot/3 mos)
Plants grown for 1 year






Fig 11. Chrysalidocarpus lutescens
Plant quality vs. soluble salts


Quality Grade


millimhos/cm


0 Q I I I I
0 4.1 8.2 12.2 16.3 20.4 24.5 28.6 32.6 36.7 40.8 4
FERTILIZER RATE (g 19-6-12/8" pot/3 mos)
Plants grown for 1 year


Fig 12. Dracaena deremensis 'Warneckii'
Plant quality vs. soluble salts


1.5

1.25

1

0.75

0.5

0.25


Quality Grade


millimhos/cm


0 4.3 8.6 12.9 17.2 21.5 25.8 30.1 34.4 38.7 43
FERTILIZER RATE (g 19-6-12/8" pot/3 mos)
Plants grown for 10 months


SPlant Quality
Soluble Salts


I I I t