Group Title: CFREC-Apopka research report - Central Florida Research and Education Center-Apopka ; RH-90-15
Title: Effect of potting medium temperatures on release curves of slow-release fertilizers in the presence of Ficus benjamina
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Permanent Link: http://ufdc.ufl.edu/UF00065861/00001
 Material Information
Title: Effect of potting medium temperatures on release curves of slow-release fertilizers in the presence of Ficus benjamina
Series Title: CFREC-A research report
Physical Description: 6 p. : ; 28 cm.
Language: English
Creator: Conover, Charles Albert, 1934-
Poole, R. T ( Richard Turk )
Central Florida Research and Education Center--Apopka
Publisher: University of Florida, IFAS, Central Florida Research and Education Center-Apopka
Place of Publication: Apopka FL
Publication Date: 1990
 Subjects
Subject: Ficus (Plants) -- Florida   ( lcsh )
Fertilizers -- Experiments -- Florida   ( lcsh )
Potting soils   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 3).
Statement of Responsibility: C.A. Conover and R.T. Poole.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065861
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70294807

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-& f Effect of Potting Medium Temperatures on Release Curves
o-1' of Slow-Release Fertilizers in the Presence of Ficus benjamin

C. A. Conover and R. T. Poole1 [
University of Florida, IFAS,
Central Florida Research and Education Center .
CFREC-A Research Report RH-90-15 i 1 -(

Osmocote is a slow-release fertilizer of choice for many foliage r' Fr 7,":;'
growers in Florida. Osmocote's release rate varies with temperature, and
soil temperatures in containers in Central Florida were found to range from
a low of 40F in winter, to a high of 1050F in summer. None of the
Osmocote sources designed to provide nutrients for 12 months performed well
in full-sun in central Florida, but several provided adequate nutrients
under 63% shade.

The following two experiments were designed to determine influences of
soil temperatures and Osmocote sources with different release durations on
plant growth as well as to follow the amount of nutrients released by these
Osmocote sources over time as determined by measuring soluble salt levels.
Both experiments compared the performance of 4 fertilizer sources when used
to grow Ficus benjamin at 4 soil temperature levels. Since the two
experiments were very similar, experiment 1 is described in detail, while
only the differences are listed for experiment 2.

On June 7, six inch tall liners of Ficus benjamin (weeping fig) in 3
inch pots were repotted into 6 inch plasti-cpots containing a soil mix made
up of 3 sedge peat moss:l mason sand (v/v) amended with 1 lb Micromax and 5
lbs dolomite per yd3. Micromax is a micronutrient blend manufactured by
Sierra Chemical Co., Milpitas, CA. Pots were then placed in zoned
forced-air chambers where soil temperatures were maintained at 68, 77, 86,
and 95F. Chambers were located in glass greenhouses where light levels
reached a maximum of 1000 ft-c and air temperatures ranged from 70 to 900F.
Fertilizer was surface applied at time of placement of plants in the
greenhouse using four Osmocote sources with different ratios and release
times. The treatments were as follows: (1) 24-5-12, an 8 to 9 months, (2)
24-6-12, a 3 to 4 months, (3) 19-6-12, a 3 to 4 months, and (4) 18-6-12,
with an 8 to 9 months release time.

Fertilizer application rates were as follows: (1) 24-5-12, 12 grams
per pot every 9 months, (2) 24-6-12, 4 grams per pot every 3 months, (3)
19-6-12, 5 grams per pot every 3 months, and (4) 18-6-12, 15 grams per pot
every 9 months. Application amounts were based on % N and release time of
the fertilizer, so that all pots theoretically received the same amount of
nitrogen. Soluble salt levels were determined every 2 weeks starting on
June 17, using the pour-through nutrient extraction method. Data recorded

ICenter Director and Professor and Professor of Plant Physiology,
respectively, Central Florida Research and Education Center, 2807 Binion
Road, Apopka, Florida 32703









at the conclusion of experiment 1, on October 21, included plant height,
top and root fresh weights, plant grade (1 = poor, unsalable to 5 =
excellent quality) and root grade (1 = no visible roots to 5 = entire root
ball covered by roots). Plant tissue was analyzed to determine percentage
of nitrogen, phosphorus, potassium, calcium and magnesium and also parts
per million (ppm) copper, iron, manganese and zinc.

Experiment 2 used rooted cuttings of Ficus benjamin potted directly
into 6 inch pots on April 15. Plants were grown on a greenhouse bench on a
maintenance fertilizer program of 0.15 grams per pot 20-20-20 received
weekly. On May 27 plants were pruned to a height of 6 inches and placed in
temperature-controlled chambers where soil temperature and fertilizer
treatments were started. Two slow-release fertilizer sources tested, (1)
19-6-12, a 3 to 4 months and (2) 18-6-12, an 8 to 9 months, were retained
from experiment 1, but 24-6-12 and 24-5-12 were replaced with (3) 24-5-9,
an 8 to 9 months, and (4) 24-5-8, with a 12 to 14 month release duration.
Fertilizer application rates were as follows: (1) 19-6-12, 5 grams per pot
every 3 months, (2) 18-6-12, 15 grams per pot every 9 months, (3) 24-5-9,
12 grams per pot every 9 months and (4) 24-5-8, 16 grams per pot every 12
months. Soluble salts levels were measured every 3 weeks starting June 29.
Experiment 2 was terminated on Nov. 2 when plant height, top and fresh
weights, plant grade and root grade, as in experiment 1, were recorded.

Plant height was not affected by soil temperature in experiment 1 but
in experiment 2 plant height decreased as soil temperature increased. In
both experiments plant and root grades decreased by almost a whole grade as
soil temperatures increased from 68 to 950F (Table 1). Data collected from
experiments 1 and 2 show root fresh weight decreasing with increasing
temperatures and top fresh weight decreasing with increases in soil
temperature. Data from both experiments also show suppression of root and
top growth at much lower temperatures than previously observed, but this
was probably due to plants being exposed to the same soil temperature over
a 24 hour day. Tissue samples analyzed for percent of 5 major elements and
parts per million (ppm) of 4 minor elements cannot be used to explain
growth suppression observed at 950F (Table 2, soil temperature). Previous
research shows summer soil temperatures taken in pots of plants growing in
shaded structures in central Florida ranged from a minimum of 730F to a
maximum of 860F. This means some growth suppression might occur on Ficus
benjamin even in commercial shadehouse growing environments. GrowtHi
suppression is even more likely to occur where Ficus is grown in full sun,
where soil in containers may reach 1050F or higher.

Growth suppression of Ficus benjamin was not expected at these
temperatures but these data lp explain the large growth variation that
occurs with Ficus benjamin in shaded versus full-sun locations.
Fertilizer source had no effect on plant growth and tissue analysis
revealed only slight differences in element content of Ficus benjamin
tissue grown in experiment 1 using 4 different fertilizers (Table 2,
fertilizer ratio). This means the method of compensating for variable
release terms was satisfactory for these experiments.


-2-









Soluble salts levels of the leachate were much higher at the beginning
of experiment 1 than experiment 2 (Table 3). This was probably due to the
small root systems of the recently repotted liners used in experiment 1
being compared to the established plants used in experiment 2. Decreases
in soluble salts levels of the leachate over time were caused by plant
usage and irrigation, as well as the designed release time of the
fertilizer source.

Direct comparison of the Osmocote sources in both experiments is only
possible with 19-6-12 and 18-6-12 (Table 4). In general the long-term
materials released nutrients at the same level as the short-term materials
in the beginning and continued at higher levels as the short-term release
sources were depleted.

The effect of temperature on fertilizer release durations appears to
be more complicated than previously suspected. The release rates developed
by the manufacturer of Osmocote and those from research done in water show
decreasing release time with increasing temperatures. However, these tests
did not consider effects plants and soil could have on fertilizer source.
Results from these two experiments show nutrient release increased with
increasing temperatures up to 860F and then decreased as temperature rose
to 950F.

In these experiments plants grew and used nutrients as they were
released. This could have skewed the data in a way that would indicate low
availability of nutrients based on soluble salts levels even though plants
were growing rapidly. However, plants had poorer growth measurements when
grown at 950F than at 860F even though soluble salt levels were lower at
950F. These data show that rapid release of nutrients and possible plant
damage may not be as temperature dependent as is believed and may be
strongly influenced by plant size at time of fertilizer application.

Additional Reading

1. Conover, C. A. and R. T. Poole. 1985. Influence of fertilizer source,
rate and application method on growth of Brassaia actinophylla and
Viburnum odoratissimum. Proc. Fla. State Hort. Soc. 98:82-85.
2. Harbaugh, B. K. and G. J. Wilfret. 1982. Correct temperature is the
key to successful use of Osmocote. Florists Rev. 170(4403):21-23.
3. Ingram, D. L., C. Ramcharan, and T. A. Nell. 1986. Response of
container-grown banana, ixora, citrus and dracaena to elevated root
temperatures. HortScience 21:254-255.
4. Joiner, J. N., C. A. Conover, and R. T. Poole. 1981. Nutrition and
fertilization, p. 229-268. In: J. N. Joiner (ed.). Foliage Plant
Production. Prentice-Hall Inc., Englewood Cliffs, N. J.
5. Koller, D. C., K. L. Hiller, and R. W. VanDenburgh. 1980. A
forced-air system for controlling soil temperature in plastic pots.
HortScience 15:189-190.
6. Poole, R. T. and C. A. Conover. 1982. Influence of leaching,
fertilizer source and rate, and potting media on foliage plant growth,
quality and water utilization. J. Amer. Soc. Hort. Sci. 107:793-797.
7. Waters, W. E. and W. Llewellyn. 1968. Effects of coated slow-release
fertilizer on growth responses, chemical composition and soil salinity
levels for foliage plants. Proc. Fla. State Hort. Soc. 81:380-388.
8. Wright, R. D. 1986. The pour-through nutrient extraction procedure.
HortScience 21:27-229.


-3-









Table 1. Effects of soil temperature on growth of Ficus benjamin.


Top Root
Treatment Height Plant Root fresh wt fresh wt
(OF) (in) grades grade (oz) (oz)

Experiment 1 June 7 Oct 21
68 38.5 4.7 4.7 6.5 1.8
77 36.6 4.5 4.5 6.1 1.9
86 39.3 4.8 4.4 7.0 1.5
95 37.0 4.1 3.7 5.8 1.4
Experiment 2 April 5 Nov 2
68 50.3 4.8 4.5 9.3 1.8
77 48.0 4.5 4.4 8.4 1.7
86 46.4 4.4 4.1 8.0 1.6
95 44.0 3.9 3.6 6.9 1.5

zPlant grade was rated on a scale from 1 = poor, unsalable to 5 =
excellent, highly salable.
YRoot grade was rated on a scale from 1 = no visible roots to 5 = entire
root ball covered by roots.


Table 2. Tissue analysis of Ficus benjamin grown using 4
and 4 soil temperature levels. Experiment 1.


fertilizer sources


Soil
temperature
(F) Nz P K Ca Mg Cu Fe Mn Zn
68 2.7 0.2 1.1 1.3 0.4 9.2 60 38 22
77 2.6 0.2 1.2 1.3 0.5 9.5 59 44 23
86 2.6 0.2 1.2 1.4 0.5 10.5 61 43 23
95 2.5 0.2 1.1 1.2 0.6 9.6 55 43 23

Fertilizer ratio
and duration
24-5-12 (8 to 9 mos) 2.5 0.2 1.1 1.2 0.4 9.5 58 44 24
24-6-12 (3 to 4 mos) 2.7 0.2 0.9 1.6 0.6 9.5 56 41 23
19-6-12 (3 to 4 mos) 2.5 0.2 1.2 1.3 0.5 10.1 63 40 21
18-6-12 (8 to 9 mos) 2.6 0.2 1.3 1.2 0.4 9.7 58 42 23


'Nitrogen (N), Phosphorus
are expressed as percent


(P), Potassium (K), Calcium (Ca), and Magnesium (Mg)
dry weight in tissue sampled.


Copper (Cu), Iron (Fe), Manganese (Mn), and Zinc (Zn) are expressed in parts
per million (ppm) in tissue sampled.


-4-










Table 3. Influence of soil temperature on soluble salts levels of the leachate utilizing the
pour-through system.


Soil Soluble salts (pmhos/cm)
temperature
(OF) Date Jun 17 Jul 1 Jul 15 Jul 29 Aug 12 Aug 26 Sep 9 Sep 22 Oct 7 Oct 21

Experiment 1
68 3244 3003 2329 1896 975 703 737 905 746 547
77 3362 3254 2163 1456 755 675 541 1006 778 609
86 3421 3767 3357 2668 1605 940 818 874 683 559
95 3346 3033 2634 2116 1086 736 545 1031 748 616


Soil Soluble salts (pmhos/cm)
temperature
(OF) Date Jun 29 Jul 20 Aug 10 Aug 31 Sep 21 Oct 13 Nov 2

Experiment 2
68 1017 731 1049 912 675 586 527
77 966 776 995 1156 835 676 533
86 996 1022 1366 1192 879 743 551
95 1141 1035 1218 977 769 711 597


5i-









Table 4. Influence of slow-release fertilizer source on soluble salts levels of the leachate utilizing the
pour-through system.


Experiment 1 Soluble salts (pmhos/cm)


Fertilizer Fertilizer
ratio" duration Jun 17 Jul 1 Jul 15 Jul 29 Aug 12 Aug 26 Sep 9 Sep 22 Oct 7 Oct 21

24-5-12 3 to 4 mos 3349 3228 3037 2693 1705 1142 783 812 586 480
24-6-12 8 to 9 mos 2941 2687 2217 1747 823 478 496 766 747 562
19-6-12 8 to 9 mos 3630 3708 2603 1885 898 568 514 1295 803 630
18-6-12 12 to 14 mos 3452 3432 2625 1811 995 865 847 944 819 658

Experiment 2 Soluble salts (pmhos/cm)


Fertilizer Fertilizer
ratio2 duration Jun 29 Jul 20 Aug 10 Aug 31 Sep 21 Oct 13 Nov 2

19-6-12 3 to 4 mos 1044 873 805 599 490 691 624
18-6-12 8 to 9 mos 1141 744 1210 1303 1081 817 596
24-5-9 8 to 9 mos 979 837 848 700 550 451 431
24-5-8 12 to 14 mos 955 1110 1765 1635 1036 758 557

ZSlow-release fertilizers manufactured by Sierra Chemical Co., Milpitas, CA.




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