Group Title: ARC-A research report - Agricultral Research Center-Apopka ; RH-78-2
Title: Fertilizer facts for foliage growers
Full Citation
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 Material Information
Title: Fertilizer facts for foliage growers
Series Title: ARC-Apopka research report
Physical Description: 7 leaves : ; 28 cm.
Language: English
Creator: Conover, Charles Albert, 1934-
Agricultural Research Center (Apopka, Fla.)
Publisher: University of Florida, IFAS, Agricultural Research Center
Place of Publication: Apopka FL
Publication Date: 1978
Subject: Foliage plants -- Fertilizers -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: Charles A. Conover.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065900
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70636230

Full Text


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida


Charles A. Conover
University of Florida, IFAS
Apopka, FL 32703 '.
ARC-Apopka Research Report RH-78-2

So many types of fertilizer are available to foliage growers- that

selection of a particular source, ratio and analyses is difficult. Of

particular importance to producers are (1) does the fertilizer source

grow good plants, (2) is the fertilizer source efficient, i.e., is use

of all or most of the active ingredients such as nitrogen obtained, and

(3) is the fertilizer source economical in cost per unit of fertilizer,

labor required for application and capital investment in equipment.

None of the presently available fertilizers rate highest in all

categories listed above. Additionally, temperature, rainfall, potting

medium and crop production cycle should all influence selection of a

fertilizer source. Thus, selection of a particular fertilizer depends

on factors listed below:

Results obtained from various fertilizer sources

Nearly 8 years of research on foliage plants with numerous fertilizer

sources has shown that many are acceptable, but that several are more

efficient in terms of growth and quality. Comparisons between fertilizer

sources should only be made when nitrogen is applied at similar levels,

although differences in levels of other nutrients should be considered.

Plant response depends on availability of nutrients as well as the period

of release for slow release sources. Table 1 provides an indication of

fertilizer efficiency for sources used at this research center. As shown

in the table, 1.33 pounds of a Urea Formaldehyde based fertilizer is


needed to get the same response as 1 pound of a liquid fertilizer of the

same analysis. Some of the reasons for this are that not all of the

nutrients may be released from slow release sources during the crop

cycle, and also, as foliage plants normally grow rapidly they require

nutrients be readily available as needed, which may not occur with some

slow release sources.

Table 1. Relative efficiency of several fertilizer sources based on foliage
plant response observed under experimental conditions.

Frequency of Relative* Lbs needed for
Fertilizer source application efficiency equal response

Liquid Weekly 100 '1.00
Dry (100% water soluble) Weekly 100 1.00
Slow release (Osmocote) Every 3 months 90 1.13
Slow release (Sulphur coated) Every 3 months 90 1.13
Slow release (Urea Formaldehyde) Every 3 months 75 1.33

Plant response to liquid fertilizer has been higher than other sources and has
been assigned a relative efficiency of 100 however, actual efficiency would
be less.

Fertilizer ratios (Nitrogen:Phosphorus:Potassium) are important, but,

experimentally, we have not noticed any difference between ratios of 1:1:1,

2:1:1 or 3:1:1. However, use of potassium at less than 50% or phosphorus

at less than 75% of the nitrogen level is not recommended, as deficiencies

may occur.

Fertilizer costs

Actual cost of fertilizers varies considerably even within a local area.

Prices listed in Table 2 are for 1 ton lots purchased from standard supply

sources in January, 1978.

Table 2. Approximate fertilizer cost per ton and/lb N for several fertilizer


Fertilizer source Manufacturer Cost/ton Cost/lb Nitrogen

Liqi id
9-3-6* USS Agri. Chem. $134.75 $ .75

16-4-8* USS Agri. Chem. 195.90 .61

Dry (100% soluble)

20-20-20* Peters 827.20 2.07

20-2-20 Mixed from NH4NO3, HPO4
and KNO3 216.80 .54

Slow Release (Osmocote)

19-6-12 Sierra Chem. Co. 879.90 2.32

18-6-12 Sierra Chem. Co. 916.65 2.55

Slow Release (Sulphur Coated)

14-14-14* Atlantic Fert. Co. 540.00 1.93

14-14-12* Nurseryman's Sure Gro Corp. 602.00 2.15

Slow Release (Urea Formaldehyde)

25-10-10 Scott's 640.00 1.28
18-6-12 Atlantic Fert. Co. 560.00 1.56

Contains micronutrients.

It is easy to change the fertilizer cost to reflect price changes in your

area and to obtain costs associated with your type of operation. When

calculating fertilizer costs, one must consider not only cost per ton, but

also cost per unit of fertilizer as well as associated equipment and labor

costs of application.


A quick reference to several commonly used fertilizer sources and

their approximate costs is listed in Table 3.

Table 3. Fertilizer costs ($) when 1500 lb N/A/yr is obtained from several
sources and applied broadcast or placed within containers*.

Cost/l000 ft2
Cost/1000 ft2 (1000 6" pots)
Fertilizer source Manufacturer Broadcast 6" O.C.

9-3-6** USS Agri. Chem. $ 43.27 $ 8.49
16-4-8** USS Agri. Chem. 38.45 7.55
Dry (100% soluble)
20-20-20** Peters 98.37 19.30
20-2-20 Mixed from NH4NO3, HPO4 51.65 10.14
and KNO3
Slow Release (Osmocote)
19-6-12 Sierra Chem. Co. 99.36 19.50
18-6-12 Sierra Chem. Co. 108.32 21.26
Slow Release (Sulphur Coated)
14-14-14** Atlantic Fert. Co. 84.19 16.52
14-14-12** Nurseryman's Sure Gro Corp. 92.75 18.20
Slow Release (Urea Formaldehyde)
25-10-10 Scott's 67.71 13.29
18-6-12 Atlantic Fert. Co. 80.54 15.81

Includes materials, equipment and labor.
Contains micronutrients.

The economic data in Table 3 are self-explanatory. However, several

comments can be made:

1. Broadcast application of liquid or dry soluble fertilizers is

much more expensive than in pot application. In addition,

when either is applied broadcast, the actual amount of fertilizer

being applied to the potting medium surface of container-grown

plants can vary because of deflection by the plant canopy. This

deflection may be as high as 50% with some types of plants.

Another problem with broadcast application is the large amount

of fertilizer that falls between the pots and runs off. New

fertilizer containment requirements by EPA will someday prevent

this application method.

2. Direct container applications of several liquid or soluble

fertilizers are lower in cost than most slow releaseforms

placed in the container. However, a quick inspection of

Table 3 will show that this is not always true, since pre-

mixed soluble fertilizer can be as expensive as other sources.

3. Cost consideration has not been given to inclusion of micro-

nutrients in the fertilizer program. The problem is that just

because a fertilizer source contains micronutrients they may

not be present in the proper ratio or quantity. Several

fertilizer sources listed that do contain some micronutrients

also require the addition of others or inclusion of another

micronutrient supplement in-the potting medium. Lack of

micronutrients or the need to supply additional ones will

add approximately 10% to the total fertilizer cost.

Selection of fertilizer sources

Selection of a fertilizer source depends on several factors in addition

to cost and application systems, and some of those that need to be considered

for listed sources follow:

Liquid Best plant growth usually occurs when liquid fertilizer is applied

to pots on a weekly or every 2 weeks basis, or in a constant feed program.

However, monthly application is often acceptable under greenhouse cover.

Where plants are subject to rainfall, especially during summer when rapid

growth occurs, monthly applications will not be adequate. Stock benches and

beds can be fertilized on a monthly basis without significant loss of'yield.

Be careful when selecting a liquid fertilizer, as some may clog spagetti tube

watering systems. Remember, liquid sources are fast acting and available to

the plant within hours of application. They can be leached from the potting

mixture, but their availability is not limited by temperature or soil micro-


Dry (100% soluble) Basically the same as liquid fertilizer; since it is mixed

with water to form liquid fertilizer. Be sure that all components go into

solution, since this may effect the ratio and analyses if they do not. Also,

suspended solids may lodge in injectors or spagetti tube watering systems if

all fertilizer does not go into solution.

Slow Release (Osmocote) This source releases through osmotic action (a

concentration gradient forms between the potting mixture and the capsule).

However, this can be strongly influenced by temperature. The release curve

is good at a 700F soil temperature, but at 80 or 90F soil temperature it

is often extremely rapid. During periods of extremely high temperature, it

may be better to apply a lesser amount more frequently. Reduced release rate

during cool weather is less important, since plants will not be actively

growing then. As all ingredients are coated, this is truely a slow release

fertilizer. For this reason, it cannot be leached from the potting mixture,

and thus applications should be timed to the production cycle so that large


amounts of fertilizer are not present at time of sale.

Slow Release (Sulphur Coated) Although called a slow release fertilizer

by many, this is not entirely true, since only nitrogen is in a slow release

form. The remaining elements are immediately available and may cause damage

if a high rate is utilized. Nitrogen is released when it goes into solution

and leaches slowly through the sulphur coating. The process of coating urea

with sulphur is somewhat inexact and thus the release rate sometimes varies

between lots. Another problem is possible growth reductions near the end of

the application cycle, since most of the phosphorus or potassium may be con-

sumed or leached.

Slow Release (Urea Formaldehyde) Although often termed a slow release

fertilizer, this is not entirely true, since only nitrogen is in a slow

release form. The remaining elements are immediately available, and may

cause damage if a high rate is used. The nitrogen from Urea Formeldehyde

is made available to plants by the action of microorganisms, as most of

the compound is insoluble in water. Therefore, release is slow when few

microorganisms are present such as with sterilized soils. Since a

significant portion is not available for up to a year, it is necessary

to supply plants higher than recommended rates to get the desired response.

Because of the very slow release characteristic, plant growth is sometimes

slowed during periods when rapid growth could be occurring, because the

release rate is less than plant demand.

This public document was promulgated at an annual cost of $25.97 or
5.2 cents per copy to inform county and state extension personnel,
Foliage growers, marketers and allied trades of research results
and improved practices in ornamental horticulture.

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