Title: TropicLine
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Title: TropicLine
Series Title: TropicLine
Physical Description: Serial
Language: English
Creator: Fort Lauderdale Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida
Publisher: Fort Lauderdale Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Ft. Lauderdale, Fla.
Publication Date: January/February 1993
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Bibliographic ID: UF00089450
Volume ID: VID00004
Source Institution: University of Florida
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TropicLine 6(1)


Sropi cL n e Volume 6, Number 1, January-February, 1993


Editor: Alan W. Meerow
Christine T. Stephens, Dean, Cooperative Extension



Growth Response Of West Indies Mahogany To Continuemtm Or

Osmocotetm Application During Transplanting: Another follow-up onpolymers
(hydrogels)

Sven E. Svenson

Former Horticultural Physiologist

Hydrogels are sold under various brand names and include many formulations.
These "polymers" can absorb hundreds of times their weight in water. The
assumption for their use is that incorporating these polymers into soils or
growing media increases retention of large quantities of water that becomes
available for plant use; thus, plant growth rates could be increased,
and/or water supplies conserved.

Research has suggested that polymers may reduce watering frequency of
container-grown or field-grown plants (Letey, 1992; Wang, 1989), enhance
plant growth (Bearce and McCollum, 1977), increase media mineral nutrient
retention (Henderson and Hensley, 1985), and increase the shelf-life of
potted crops (Bearce and McCollum, 1977; Gehring and Lewis, 1980). Some
studies have reported a delay in the onset of permanent wilting when
evaporation is intense (Johnson, 1984) or when twice the manufacturers
recommended rate of polymer was used (Wang and Boogher, 1987). In contrast,
many other studies have indicated that there is little or no benefit from
use of polymers (Austin and Bondari, 1992; Conover and Poole, 1976;
Henderson and Davies, 1987; Ingram and Yeager, 1987; Keever et al., 1989;
Steinberger and West, 1991; Tripepei et al., 1991; Wang, 1989).

Common media fertilizer amendments, such as dolomitic limestone, have been
shown to reduce the water absorption of polymers (Foster and Keever, 1990),
leading some researchers to conclude that polymer amendment provides little
or no significant improvement in the water holding capacity of most
container media (Bowman et al., 1990). One study suggested that much of the
"extra" water held by polymers may not be available for use by plants
(Tripepei et al., 1991). Polymers used as soil amendments during
transplanting killed from 25% (Gupton, 1985) to 100% of blueberries
(Vaccinium sp., Austin and Bondari, 1992), depending upon the amount of
concurrent addition of organic matter.

ContinuemTM is a hydrogel containing N-P-K fertilizer in its
polyacrylamide matrix (Pan Agro, Inc., Logan, Utah). The manufacturer
claims the N-P-K is plant-available as the hydrogel breaks down
(slow-release fertilizer); thus, you obtain the benefits of a hydrogel
treatment (water retention in the soil), and the benefits from fertilizer
treatment from the labor of a single application.


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The objective of this study was to determine if the application of
ContinuemTM would influence the field establishment or subsequent growth
of West Indies mahogany (swietenia mahagoni), and to determine if that
influence was related to the polymer or the fertilizer component of the
product.

MATERIALS AND METHODS

West Indies mahogany seedlings growing in 4-inch pots (3.5 inch top
diameter, 2.75 inch bottom diameter, 3.75 inch height to rim) in a 5 pine
bark: 4 Florida sedge peat: 1 sand (by volume) medium were selected for
field transplanting. Seedlings averaged 32+1.2 inches tall, with a caliper
of 6.0+0.2 millimeters at the soil line. Seedlings were field-planted at
the University of Florida-FLREC (Miramar fine sand soil) using the
treatments listed in Table 1 (footnotes).

After planting, seedlings were not watered, receiving only natural
rainfall. Rainfall of 0.25 inches occurred within 2 hours of transplanting,
and rainfall exceeding 1.5 inches occurred within 24 hours of
transplanting. Nearby weeds were mowed, but were not removed.

Seedling heights and stem calipers were recorded over 9 months. Data were
analyzed with analysis of variance, and means were separated using Duncan's
New Multiple Range Test at the 5% level of significance.


RESULTS AND DISCUSSION

Control seedlings were shorter than all other treatments only 30 days after
planting (Table 1), and remained the shortest for the duration of the
study. Seedlings given 1 tsp. OsmocoteTM as a dibble were taller than all
other treatments after 30 days, and this treatment had the tallest
seedlings at all measurement times for the duration of the 281 day study.
Stem caliper growth responded similarly to height in response to treatments
(Table 1). While seedlings treated with ContinuemTM were taller than
controls, they were not taller than seedlings treated only with fertilizer.

Treatment effects were exhibited during the first 30 days after planting
(Table 1), with growth responses after 30 days explainable as a response to
plant size (larger plants growing faster than smaller plants). ContinuemTM
did enhance plant growth, but the effect was no different than the response
to slow-release fertilization. If there had been a benefit from the polymer
component of the ContinuemTM, then the ContinuemTM seedlings would have
been larger than the 2 tsp. dibbled OsmocoteTM seedlings. Therefore, the
ContinuemTM functioned only as a slow-release fertilizer, with no benefit
from the polymer component.

The largest plants were in the treatment providing the lower rate of
fertilizer (1 tsp. OsmocoteTM, dibbled), suggesting that faster growth may
not have been possible if higher fertilizer rates had been used. The
top-dress treatment (1 tbsp. OsmocoteTM) may have been less beneficial
compared to the dibble treatment due to more efficient weed competition for
fertilizer in the top-dress treatment.

Both ContinuemTM and OsmocoteTM are sold as "three to four-month"
treatments, but neither influenced growth after 30 days. Application rates
may have been too low, or a different application technique may be required


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to extend usefulness beyond 30 days. Since fertilizer salts have been shown
to destroy the integrity of polymers (Bowman, Evans and Paul, 1990), the
presence of fertilizers in the ContinuemTM may have reduced the
effectiveness of the polymer component of the product.

In a separate study, ContinuemTM reduced the irrigation frequency of
Hypoestes transplanted into 14-in nursery containers from 4-in pots by about
one day for every seven days (data not shown), certainly not even close to
the 2 to 3 week frequency suggested on some labels (see Letey et al.,
1992).

CONCLUSION

In this study, ContinuemTM functioned as an effective slow-release
fertilizer for field-planted seedlings. Consistent with earlier studies
(Conover and Poole, 1976; Henderson and Davies, 1987; Ingram and Yeager,
1987; Tripepei et al.; Wang, 1989), no growth benefits were obtained from
the polymer component of the product.

Polymers do not reduce evapotranspiration (Letey et al., 1992; Wang, 1989;
Wang and Boogher, 1987). Since the amount of water lost through
evapotranspiration must be replaced by irrigation, polymers do not conserve
water. Even if the polymer were able to extend the time-period between
irrigations (Letey et al., 1992), more water would be needed to bring the
growing medium or soil to full water-holding capacity -- allowing a grower
to schedule the use of more water, less often. If a grower's labor or other
expenses are high for each irrigation application, then the reduction in
irrigation frequency could be economically important. However, the
available research data indicates that the total amount of water needed
will be about the same with or without polymers.

Polymers may be effective at accomplishing certain goals, such as
increasing the water-storage capacity or enhancing plant growth in
coarse-textured growing media or soils (such as coarse sands or light
gravel), or under saline conditions (Letey et al., 1992). One report
suggests the presence of polymers might reduce nematode populations in
coarse-textured soils (Steinberger and West, 1992). However, polymers are
not beneficial in all situations. Simply altering the physical properties
of your growing medium could produce as much benefit as the use of a
polymer. Polymer users should clearly identify what they hope to accomplish
by using the product, and keep accurate records to determine if the goal
was attained. Possible alternative ways to accomplish the same goal should
be evaluated, and the relative costs compared.

LITERATURE CITED

Austin, M.E. and K. Bondari. 1992. Hydrogel as a field medium amendment for
blueberry plants. HortScience 27:973-974.

Bearce, B.C. and R.W. McCollum. 1977. A comparison of peatlite and
noncomposted hardwood-bark mixes for use in pot and bedding-plant
production. Effects of a new hydrogel soil amendment on their performance.
Flor. Rev. 161:21-23, 66.

Bowman, D.C., R.Y. Evans and J.L. Paul. 1990. Fertilizer salts reduce
hydration of polyacrilamide gels and affect physical properties of


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gel-amended container media. Jour. Amer. Soc. Hort. Sci. 115:382-386.

Conover, C.A. and R.T. Poole. 1976. Influence of Viterra hydrogel on growth
and control of wilting of 3 foliage plant species. Florida Foliage Grower
13:9-11.

Foster, W.J. and G.J. Keever. 1990. Water absorption of hydrophilic
polymers (Hydrogels) reduced by media amendments. J. Environ. Hort. 8:
113-114.

Gehring, J.M. adn A.J. Lewis, III. 1980. Effect of hydrogel on wilting and
moisture stress of bedding plants. J. Amer. Soc. Hort. Sci. 105:511-513.

Gupton, C.L. 1985. Establishment of native vaccinium species on a mineral
soil. HortScience 20:673-674.

Henderson, J.C. and F.T. Davies, Jr. 1987. Effect of a hydrophylic gel on
water relations, growth, and nutrition of landscape roses. HortScience
22:1114.

Henderson, J.C. and D.L. Hensley. 1985. Ammonium and nitrate retention by a
hydrophylic gel. HortScience 20:667-668.

Ingram, D.L. and T.H. Yeager. 1987. Effects of irrigation frequency and
water-absorbing polymer amendment on Ligustrum growth and moisture retention
by a container medium. Jour. Environ. Hort. 5:19-21.

Johnson, M.S. 1984. The effects of gel-forming polyacrylamides on moisture
storage in sandy soils. Jour. Sci. Food Agr. 35:1196-1200.

Keever, G.J., G.S. Cobb, J.C. Stephenson, and W.J. Foster. 1989. Effects of
hydrophilic polymer amendment on growth of container grown landscape
plants. J. Environ. Hort. 7:52-56.

Letey, J., P.R. Clark and C. Amrhein. 1992. Water-sorbing polymers do not
conserve water. California Agriculture 46(3):9-10.

Steinberger, Y. and N.E. West. 1991. Effects of polyacrilamide on some
biological and physical features of soil: Preliminary results from a
greenhouse study. Arid Soil Res. Rehab. 5:77-81.

Tripepei, R.R., M.W. George, R.K. Dumroese, and D.L. Wenny. 1991. Birch
seedling response to irrigation frequency and a hydrophilic polymer
amendment in a container medium. J. Environ. Hort. 9:119-123.

Wang, Y.-T. 1989. Medium and hydrogel affect production and wilting of
tropical ornamental plants. HortScience 24:941-944.

Wang, Y.-T. and C.A. Boogher. 1987. Effect of a medium-incorporated
hydrogel on plant growth and water use of two foliage species. Jour.
Environ. Hort. 5:127-130.


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Table 1. Height and stem diameter of West Indies Mahogany from 30 to 250 days after transplanting as
influenced by application of ContinuemTM or OsmocoteTM application. All seedlings averaged 32.8+1.2 cm
of height at the start of the study. Means and standard errors.

Dais afler
lr;iis )l;111lin112


Tr le iii e it


( III


Control


[heiuht]

[callpelr]

Gel dibbled1



Gel Backfill2



(OImocote
dlibbled3



Osmocote
dibbled4


()sinocote
dressed5


32 8+ (I


I4 4+0 3

35 x+2 1

I_ 4+0 2

37.3+1.5

6.3+0.3

3,_ i_+ 1 4

r~ 1 +0 3


41.8+1.5




37.0+0.5

6.3+0.3


0.014


32 x+I lI


I_ ++0 4





39.3+1.6

7.5+0.3

38 'x + 1

.7+ 3


42.7+1.5


39.3+1.6

7.1+0.3


0.006


34 5+1 'I


38 l+2 2

8 4+0' 3

40.2+1.6

8.5+0.4

3 i--+ 1


S 5+0 4

43.5+1.5

L 1+( 4


3L.9+1.7

8.1+0.3

Significance
(ANOVA
F-test), Height

0.029
Sinificance
|ANO\.A
F-test). Stem
CaIii.er


34 x+1 cL


x 2+0 5

3 1+2 1

LI j +(1 3

41.4+1.7

0.0+0.5

4(1 4+1 5

0I 4+11, 4


46.7+2.0




40.2+1.7

8.2+0.4


0.001


35 i-n+2 1








42.6+1.7

9.2+0.6

42 '+1 I

L LI+( I 4


51.3+2.3




42.0+1.8

9.2+0.5


<0.001


3LI 3+2 4


LI 3+;+

43 0+1 L

I -+(ii 4

46.5+2.1


1i 1j+( 4

56.0+4.4

11 31+10


45.1+1.6


0.005


1ContinuemTM 16-16-16 (2 tbsp/liter) amended soil dibbled below the actual root ball.


2ContinuemTM 16-16-16 (2 tbsp/liter) amended soil used as backfill around root ball.


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3OsmocoteTM 14-6-12 (2 tsp./liter) amended soil dibbled below the actual root ball.

40smocoteTM 14-6-12 (1 tsp./liter) amended soil dibbled below the actual root ball.


50smocoteTM 14-6-12 (1 tbsp./liter) topdressed on soil after transplanting.


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