Group Title: AREC-A research report - Agricultural Research and Education Center-Apopka ; RH-86-14
Title: Variability of soluble salts of potting media mixed for various times
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 Material Information
Title: Variability of soluble salts of potting media mixed for various times
Series Title: AREC-Apopka research report
Physical Description: 2 p. : ; 28 cm.
Language: English
Creator: Poole, R. T ( Richard Turk )
Conover, Charles Albert, 1934-
Agricultural Research and Education Center (Apopka, Fla.)
Publisher: University of Florida, IFAS, Agricultural Research and Education Center-Apopka
Place of Publication: Apopka FL
Publication Date: 1986
Subject: Soils, Salts in -- Florida   ( lcsh )
Soils -- Composition -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: R.T. Poole and C.A. Conover.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065912
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70667587

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Variability of Soluble Salts of Potting Media Mixed for Various Times

R. T. Poole and C. A. Conover
University of Florida, IFAS ,i..i :! Science
Agricultural Research and Education Center Apopka ibraIry
AREC-Apopka Research Report RH-86-14

Many commercial nurseries mix their own potting media from Various 1987
purchased ingredients such as peat, bark, sawdust, and sand., Time of
mixing varies considerably, sometimes only a few minutes elapse while Florida
others prepare their mix by mixing for as much as 30 minutes.--Other-
foliage growers obtain a premixed potting medium from commercial

Sometimes problems that occur during production of foliage plants are
blamed upon improper mixing of medium. Certain areas of the mix may
contain more or less of one ingredient, e.g. dolomite or especially
micronutrients, than another portion of the mix. Tests were conducted to
determine the level of variability of fertilizer in a potting medium as
indicated by soluble salts (micromhos/cm) mixed for various periods of
time. In the first test, ten samples were obtained from various parts of
one bag of Vergro Container Mix (minus superphosphate) and placed in 10 6"
pots. The remaining portion was mixed in a.3 cubic ft cement mixer for 5
minutes, then 10 more 6" pots were filled. In the second test, a Florida
peat:pine bark medium (1:1 by volume), was prepared and mixed for 5 or 10
minutes in a cement mixer.

Soluble salts (SS) were determined by the pour-through method, which
is accomplished by pouring deionized water on the pot surface and reading
SS of the first 50-100 ml of the leachate. One day later, 500 ml of a
solution containing 2 lbs/100 gal of Miller 20-20-20 soluble fertilizer was
applied to each pot. Six hours later SS were determined.

Results from the test were quite variable (Table 1). The Vergro mixes
had a larger difference between the minimum and maximum soluble salt
variables than the peat:bark mix and a slightly larger variation.
Additional mixing of the Vergro medium had no effect, 18% vs 16%, before
fertilization, indicating there was probably more variation in the testing
procedure than the medium. This observation is also indicated by results
from the peat:bark medium where mixing for 10 minutes resulted in more
variation than mixing for 5 minutes (14% vs 7%). Variation after
fertilization was also erratic, with less variation (19%) for Vergro before
mixing than after mixing (26%). But the peat:bark mix had less variation
(9%) after than before (22%).

Results from these tests indicate that considerable variation can

Professor of Plant Physiology and Professor and Center Director,
respectively, Agricultural Research and Education Center, 2807 Binion
2Road, Apopka, FL 32703.
Vergro Container Mix is manufactured by the Verlite Company, Tampa, Fl.

occur within a mix that is supposedly uniform. In the experiments
described in this report there was no advantage to further mixing for
Vergro or mixing for more than 5 minutes for peat:bark. .Thus, the
variations induced by the media can be expected to occur commonly in
testing. This could result in erroneous information being obtained if only
one or a few samples are analyzed. There are also variations induced by
the testing procedure used and these can also be expected. The procedure
used in these experiments is relatively new, but has been compared against
the 2:1 by volume and saturated paste procedures and found to be no more
variable than those methods.

Table 1. Variability of potting media mixed (10 replications) for
different times.




Vergro (5 min. in mixer)

Peat:bark,1:1 by volume
(5 min. in mixer)

Peat:bark, 1:1 by volume
(10 min. in mixer)

July 9, 1985, before fertilization


2210 387

2104 349

852 59

882 122


Vergro (5 min. in mixer)

Peat:bark, 1:1 by volume
(5 min. in mixer)

Peat:bark, 1:1 by volume
(10 min. in mixer)

July 10, 1985, after

1991 389 .19

2180 t 574 .26

1578 344 .22

1295 122 .09

ferti izationy









ZS = standard deviation (variability of average, e.g. 387).

x = average micromhos/cm (e.g. 2210).

Y20-20-20, 2 pounds per 100 gallons, 500 ml added to 6" pot afternoon of
July 9, 1985.













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