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r n- AGRICULTURAL RESEAR4
AREC Bradenton ReSearch Report GC1979-7
MINI POT MUMS PRODUCTION PRACTICES USING CAPILLARY
AND SL6J RELEASE FERTILIZER
B. K. Harbaugh and G. J. Wtilfret
OCT 0 1979
.F.A.S. -Un'iv. of Fiorida
Florida growers produce many ornamental crops in shade structures and typically
use overhead sprinklers for irrigating and fertilizing. Over 40% of the area of
most structures is not cropped, but this area is irrigated when sprinklers are used.
Capillary mat irrigation can reduce water use by confining irrigation to the cropped
area. However, early studies indicated several problems due to poor quality water
or the injection of fertilizer into the delivery system (mat fertilization). Sul-
fur, bacteria; and other impurities in the water too fine for filtering cause plug-
ging in the delivery system, and injecting fertilizers in this water confounds the
problem. Mat fertilization leads to algal development, an increase in root growth in-
to the mat, and poor distribution of fertilizer. A solution to problems associated
with water quality, quantity, and fertilization is the use of slow release ferti-
lizers incorporated in the medium in conjunction with capillary mat irrigation.
irch on production of mini-mums (garden mums forced in 4" pots) utilizing
ise fertilizers and capillary mat irrigation was initiated at AREC-Bradenton
It was evident in these initial studies that plants produced with rates
-9 pounds of 14-14-14 Osmocote/cu. yd. soil (3 month release at 700F*) on
mats were of similar quality to mini-mums produced with liquid fertilizer
watered. Rates lower than 6 pounds Osmocote/cu. yd. soil resulted in plants
rotic leaves and/or stunted growth. Higher rates did not appear to improve
lity,so interest was in refining rates between 6 and 9 pounds/cu. yd. soil.
A test was designed to determine the effects of irrigation method, growing struc-
ture, and fertilizer rates on production of mini-mum 'Stardom.' In a glass greenhouse
6 pounds of 14-14-14 Osmocote/cu. yd. soil was used to grow 'Stardom' with either
hand-water or mat irrigation. Growth comparisons were made with plants produced in
a shade structure (30% shade) with 6 or 9 pounds Osmocote/cu. yd. soil and capillary
Over 6 inches of rain fell during the growing season. Relatively low soluble
salt readings taken at the end of the test (Table 1) indicated this rainfall appar-
ently caused leaching even in pots provided water through the mat. The highest salt
concentrations were in those pots mat irrigated in the greenhouse (no leaching con-
ditions) while lowest salt concentrations were found in pots hand irritated in the
greenhouse (i.e. leaching at every watering). Plant growth evaluations (height,
spread, number of breaks, and dry weight) and % nitrogen in leaf tissue also indicated
that nutrients were lost from pots under shade structures even on capillary mats.
CH & EDUCATION CENTER
sity of Florida
The practical application of this study was to define application rates of
slow release fertilizer in different growing environments. It was found that the
application rate used within these limits (6-9 pounds/cu. yd.) was not as important
as the conditions the plants were grown in. Irrigation method, structure, and en-
vironmental parameters would dictate the optimum rate of slow release fertilizer.
These tests indicated that if irrigation method or growing structure permitted
leaching, then 9 pounds of 14-14-14 Osmocote/cu. yd. were necessary to produce
quality plants. For instance, hand-watering, overhead watering, and/or growing
in shade structures that did not exclude rain, required the higher 9 pound rate.
On the other hand, when the irrigation method and growing structure provided no
leaching conditions, such as capillary mat irrigation in a glass greenhouse, these
tests indicated 6 pounds of 14-14-14 Osmocote/cu. yd. would produce quality plants.
In summary, mini-mums can be grown successfully with capillary mat irrigation
and slow release fertilizer incorporated in the soil as shown by the many research
projects during the past 4-5 years. However, the growing environment must be con-
sidered to determine the optimum fertilizer rate.
The following guidelines can be used to produce mini-mums with a capillary
mat irrigation-slow release fertilizer management practice.
1. Use a soil mixture that is adjusted to a pH of around 6.5. Flot more than
3 days before planting*, incorporate G-9 pounds of 14-14-14 Osmocote/cu. yd. into
the medium (depending on your environmental conditions as described above).
2. Plant one rooted garden mum cutting per 4" pot (be careful to buy pots
with holes in the bottom!). After placing pots on the capillary mat, establish
capillarity by watering thoroughly (water should run out of the bottom of the pot).
3. Pinch plants 3-5 days after planting. No black cloth or lights will be
needed under Florida day lengths when rooted cuttings are planted from August-April.
4. If short cultivars are selected, no growth regulators need be used.
Examples: 'Jackpot,' 'Starlet,' 'Baby Tears,' 'Penguin,' 'Roll Call,' 'Tinker
Bell,' 'Sunburst Cushion,' and 'Stardom.' If larger cultivars are preferred, use
a 0.5% a.i. B-9 solution (5000 ppm) 10-14 days after pinching (breaks should be
5. Plants will be ready for market 8 weeks from planting rooted cuttings.
*Osmocote is hygroscopic,so there is enough moisture even in "dry" soil to initiate
release. Thus, soil mixtures with Osmocote cannot be stored since nutrient release
starts immediately. The release rate of any particular Osmocote formulation is
affected primarily (almost entirely) by temperature. Release rates are calculated
at mean temperatures' ,f 700F. Temperatures greater than 800 ill cause rapid
nutrient release, loss of fertilizer, and/or salt damage. Since Florida soil
temperatures are usually greater than 700F, the 3 month 14-14-14 Osmocote formu-
lation generally will last 1-2 months. This is ideal for an 8-week mini-mun
ble 1. Effect of rates of Osmocote, structure, and irrigation method on soil soluble
salts, growth, and nitrogen content of mini-mum 'Stardom' at harvest.
unds of Total
-14-14 soluble Plant Plant Dry Leaf
mocote/ salts height spread Breaks wt. nitrogen
i.yd.soil Structure Irrigation (ppm) (inches) (inches) (no.) (gm.) (%)
6 Greenhouse Hand water 1500 7.0 8.7 6 6.0 2.7
6 Greenhouse Capillary rmat 2G50 8.3 10.2 6 6.0 3.6
6 Saran Capillary mat 2380 8.7 9.1 5 4.0 3.0
9 Saran Capillary mat 2280 9.1 10.2 8 5.3 3.3