OF FOLIAR FERTILIZER TO FRUITING OTIRABERRIES .., -- oI0 .,
klbregts, E. E., and C. M. Howard : Lray
culturall Research & Education Center
,AS, Univ. of Florida, 13138 Lewis
llagher Road, Dover, FL 33527 ''rs.
AREC-Dover Research Reprt DOV-1987-6
Foliar applied fer ilizer has been used for many years on strawberry to
correct soil fertility problems occurring during the fruit production season.
Plant nutrients in the soil can become unavailable to the plants because of
inadequate fertilization cold soils, leaching, root damage, and others (3).
Foliar application is one of the methods available when plant beds are covered
with polyethylene mulch and the soil fertility is not sufficient to produce
optimum yields. The advantages of foliar fertilizer is that it can be
accomplished with a pes icide sprayer, which most grower's have, and requires
only a small amount of time. The plant nutrients applied are highly availnthl
to the plant and can be rapidly assimilated (3). Sometimes, a plant response
is visible within a few days, but is a significant yield response obtained?
To determine the effect of applying foliar fertilizer to strawberry with
or without adequate soi3 fertilization, two experiments were conducted.
Treatments in Experiment A were: 3 rates of soil fertilizer in pounds/acre of
nitrogen, phosphorus, ard potassium 1) none, 2) 100-10-83, and 3) 200-20-166;
and 3 rates of foliar fertilizer, applied weekly from plant establishment to end
of season, in pounds/acre of nitrogen, phosphorus, and potassium 1) none, 2)
1.07-0.48-0.91, and 3) .14-0.96-1.82. All foliar fertilization treatments were
applied to all soil fertilizer treatments. In Experiment B, treatments were
one soil fertilizer rate which was 200-16-155 pounds/acre of nitrogen, phosphorus,
and potassium, respectively, and foliar fertilizer applied at different
frequencies. Foliar rates at each application ( lx = 0.28 nitrogen 0.09
phosphorus 0.10 potassium Ib/acre) and frequency of applications were: a) lx,
twice weekly, b) 2x, twice weekly, c) lx, once weekly, d) 2x, once weekly, e) lx,
once every two weeks, f) 2x, once every 2 weeks, and g) no foliar fertilization.
After -iting, overhead sprinkler irrigation was used to establish trans-
plants and used later for irrigation. Plants in Experiment A were visually
rated for plant size and color. In both experiments fruit were harvested twice
weekly, graded, and weig ed from January through April of each season. Both
experiments were planted to 'Dover' and 'Tufts' cultivars.
In Experiment A, increasing rates of soil-applied fertilizer increased fruit
yields, fruit number, fo iar nitrogen and potassium, plant size, and foliage
color (Tables 1 and 2). Rates of foliar nitrogen, phosphorus, and potassium had
much less effect than so 1-applied fertilizer. The greatest plant response to
foliar fertilizer was wi h inadequate rates of soil fertilizer. If the high
roil fertilizer was used marketable fruit yields were not increased in any
season with foliar ferti ization. The high fertilizer soil rate is the rate
recommended by the Agric ltural Research and Education Center, Dover. Marketable
fruit per plant was line rly correlated with soil fertilizer rate, while the
foliar fertilizer rate h d no effect on fruit number. Average fruit weight was
not correlated with fert lizer treatments. Foliar-applied fertilizer at low and
high rates damaged leave! each season. Damage was confined mostly to the leaf
riargins after 4 or more foliar applications, especially with the high foliar rate.
At times, browning of the calyx was noticed in the low and high foliar fertiliz n
plots. Damage was greatest in plots receiving the highest rates of foliar ard
soil fertilizer. How ver, damage was not evident in the high soil fertilizer
treatment not receivi foliar fertilizer.
With Experiment fruit yields were similar in all treatments for each
cultivar except the treatment receiving the highest rate of foliar fertilizer
(2x applied twice wee ) which gave significantly lower yields than other
treatments (Table 3). No foliage 'burn' occurred in this experiment, but rates
of foliar fertilizer a plied were lower than in Experiment A.
The following is list of generalizations from this and other research
and from observations n the effect of applying foliar nitrogen, phosphorus and
potassium fertilizer t fruiting strawberry (1,2).
1. Generally, foliar fertilization of strawberries with nitrogen, potassium
and phosphate wil not enhance fruit yields if adequate soil nutrients are
available to the lant roots. A possible exception is when the soil, on
rare occasions, i very cold during a prolonged period of cold weather
which may cause s il nitrogen to become unavailable to the plant* Another
exception is with poor root development caused by nematodes, diseases or
other factors, U der these circumstances, the root does not have access to
sufficient nutrients to satisfy plant requirements.
2. Application of fo iar fertilizer can result in leaf and calyx tburnt if
adequate amounts (f N, P, and K are present in the soil. With high rates
of foliar fertili action leaf and calyx 'burn' may occur with low fertilizer
rates and even wh n no soil fertilizer is applied.
3. The foliar applic tion of fertilizer cannot be substituted for soil
application of fe tilizer. Severe foliage damage will occur before
sufficient foliar nutrients are applied. Therefore, if little or no
fertilizer is app led or if nutrients are severely leached, foliar
fertilization wil give only minimal fruit yields.
4. If soil nutrients re slightly to moderately below that required for
optimum yields, fo iar fertilization may result in maximum yields.
However, one must be able to apply sufficient nutrients to meet the plant
needs without sust dining foliage or calyx 'burn', which can result in
reduced yields and/or unmarketable fruit.
5. Possible methods to supply adequate supplemental nutrients without foliage
damage is with the injection wheel and drip irrigation. With either of
these methods one -an supply adequate fertilizer yet not so much so as to
cause foliage 'bur'. Of course, the drip irrigation system must be in
place at the beginng of the season. Some growers apply fertilizer with
the overhead irrigation system. This may work, but a large percentage of
the fertilizer wil: 'run-off', leach, or be positionally unavailable to
If overhead sprinkler irrigation is used, it is important to place adequate
but not excess fertilize r in the plant bed before mulching. Placement should
be in a position in the bed so it will be least likely to leach. This usually
is a band between plant rows about 1 or 2 inches deep. If the bed is not
flooded and slow-rele4
adequate fertilizer st
1. Albregts, E. E.,
of fruiting straw
se nitrogen and perhaps slow-release potassium are used,
would be available to produce optimum yields.
mad C. M. Howard. 1986. Supplemental foliar fertilization
berries. Proc. Fla. State Hort. Soc. 99:329-331.
Albregts, E. E., Omd C. M. Howard. 1986. Response of strawberries to soil
and foliar fertile zer rates. HortScience 21:1140-1142.
3. Wittever, S. H., I
feeding of plant
and L. B. Nelson,
Amer. Madison, WiL
I. S. Bukovac, and H. B. Tukey. 1963. Advances in foliar
nutrients, p 429-455. In: M. J. McVocker, G. L. Bredger,
(eds). Fertilizer technology and usage. Soil Sci. Soc.
Table 1. Effect of s il and foliar fertilizer rates on seasonal strawberry
marketable fruit y elds and fruit number, Experiment A.
Fertilizer Treatments 1981 1982 1983 1982 1983
Soil rates Foliar rates Flats/acre
None None 1338cz 729d 1065b 557b 775c
None Low 2187c 906cd 1327b 798b 10330
None High 2168c 1158c 1630b 1138ab 1098c
Low None 4516b 1502b 3862a 1300a 2106b
Low Low 4905a 1998a 3896a 1322a 1996b
Low High 4519b 1638ab 3989a 1454a 2555a
Normal None 5016a 1707ab 3860a 1200ab 2660a
Normal Low 4886a 2085a 3919a 1352a 2689a
Normal High 4468b 1704ab 3778a 1248a 2437ab
None None 17.5d 10.7d 17.8b 9.0c 12.7e
None Low 28.8c 13.6cd 18.8b 12.0c 16.2de
None High 2~11c 16.3c 23.1b 16.8b 16.8d
Low None 55.0b 22.2b 50.0a 19.4a 31.4b
Low Low 59.3b 28.1a 51.1a 19.4a 26.8c
Low High 56.6b 24.Ob 53.9a 21.3a 34.5b
High None 65.Oa 24.3b 52.5a 17.6ab 37.3ab
High Low 64.3ab 29.4a 52.3a 20.0a 40.3a
High High 59.7b 24.6b 52.2a 18.4ab 34.6b
in same column not significantly different.
7'Mans followed by same
Table 2. Effect of soil
and foliar fertilizer rates on plant size and foliage color,
Plant size .
Fertilizer treatments Dover Tufts
Soil rates Foliar ra es 1981 1982 1983 192 1983
None None 2.8dY 6.5e 6.2b 6.0c 6.2c
None Low 5.6c 8.0d 6.7b 8.0b 7.0b
None High 6.0c 8.5c 6.7b 8.5b 7.2b
Low None 9.1b 8.5c 10.Oa 9.0ab 10.Oa
Low Low 9.4ab 8.5c 9.5a 8.5b 9.5a
Low High 9.0b 8.5c 10.0a 8.9b 10.0a
High None 9.6a 9.0b 10.Oa 8.5b 10.Oa
High Low 9.4ab 9.5a 10.Oa 9.5a 10.0a
High High 9.3ab 9.lab 10.Oa 8.9ab 10.Oa
None None 1.OeY 2.0c 1.2e 2.4d 1.2e
None Low 1.6de 2.8c 2.3d 2.4d 2.2c
None High .20d 4.0b 2.5d 4.4c 2.5c
Low None 2.8c 4.4b 4.5bc 5.6a 5.Ob
Low Low 3.4c 4.4b 4.2c 6.0a 4.5b
Low High 4.2b 4.0b 5.0b 6.0a 5.7a
High None 4.6b 5.2a 5.5ab 4.8c 6.0a
High Low 5.6a 4.8ab 5.5ab 6.0a 6.0a
High High 5.2a 5.6a 5.8a 5.6a 6.0a
ZRated 10 (largest) to 1 smallest).
FYfeans followed by same letter in same column are not significantly different.
XRated 1 to 6 with 1 = li,
green with less than 50%
green, 5 = moderate gree:
ght green with 50% or greater red or yellow, 2 = light
red or yellow, 3 = light green, 4 = light to moderate
i, and 6 = dark green.
Effect of foli
ar fertilizer treatments on marketable fruit yield (flats/
Treat ients Harvest period
Cultivars Schedule Ratez Jan. + Feb. March April Total
Tufts Twice/wk lx 265aby 1088 776 2288ab
Tufts Twice/wk 2x 161b 986 671 2011b
Tufts Once/wk Ix 285ab 1289 1232 2806a
Tufts Once/wk 2x 120b 1034 960 2114ab
Tufts Once/2 week Ix 171b 1363 1151 2685ab
Tufts Once/2 weeks 2x 343a 1318 1074 2735ab
Tufts Control 210ab 1271 960 2441ab
Dover Twice/wk lx 482b 1452ab 217 2151ab
Dover Twice/wk 2x 486b 1305b 201 1992b
Dover Once/wk Ix 519b 1642ab 210 2370ab
Dover Once/wk 2x 502b 1444ab 204 2150ab
Dover Once/2 weeks Ix 552ab 1611ab 170 2333ab
Dover Once/2 weeks 2x 616ab 1768a 176 2561ab
Dover Control 704a 1761a 146 2612a
lx = 0.28
nitrogen, 0.09 phosphorus, 0.10 potassium Ibs/acre; 2x = twice the Ix
Y~Iean separation in column
is within a cultivar by Duncan's multipft range test, 5%
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