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Group Title: Circular
Title: Commercial vegetable crop nutrient requirements
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Title: Commercial vegetable crop nutrient requirements
Series Title: Circular
Physical Description: 8 p. : ; 28 cm.
Language: English
Creator: Hochmuth, George J ( George Joseph )
Hanlon, Edward A ( Edward Aloysius ), 1946-
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1990, 1989
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Subject: Vegetables -- Fertilizers -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
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Statement of Responsibility: G.J. Hochmuth and E.A. Hanlon.
General Note: Title from cover.
General Note: "June 1989."
General Note: "Reprinted August 1990"--P. 4 of cover.
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Holding Location: University of Florida
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oclc - 26977794
alephbibnum - 001752722
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3oG
June 1989 Circular 806






Commercial Vegetable
Crop Nutrient
Requirements irary
SJ P 8 1982
G. J. Hochmuth and E. A. Hanlon no:,, .


Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences
University of Florida / John T. Woeste, Dean








Contents

1 Introduction
Nutrient requirements


2 Soil testing


3 Irrigation
Supplemental fertilizer
Mulched crops
Soil pH


3CU~Kcv


4 Nutrient forms


5 Secondary nutrients


6 Micronutrients
Placement and timing


Liquid vs. dry fertilizer
Foliar fertilization
Double-cropping


Authors

G. J. Hochmuth, Associate Professor and Extension
Specialist, Vegetable Crops Dept., IFAS, Gainesville.
E. A. Hanlon, Assistant Professor, Extension Soils
Specialist, Soil Science Dept., IFAS, Gainesville.


7


'* '.











Introduction


The purpose of this circular is to present crop
nutrient requirements for commercial vegetables in
Florida. It is intended to be a supplement to Exten-
sion Circular 225-C, "Commercial Vegetable Fer-
tilization Guide." Certain information included in
225-C is repeated here to increase the clarity of this
presentation.
The first part of this publication contains discus-
sions of several topics pertaining to fertilization of
vegetable crops. The second part presents, in tabular
form, the crop nutrient requirements of vegetables
in Florida.


Table 1. Crop nutrient requirements for N, P, and K
for vegetables grown on irrigated mineral soils.


Crop
Beans, bush
Beans, pole
Beans, lima
Beets
Broccoli
Cabbage
Carrots
Cauliflower
Celery
Chinese cabbage
Collards
Corn, sweet
Cucumber
Eggplant
Lettuce
Muskmelon
Mustard
Okra
Onions
Peas, English
Peas, southern
Pepper
Potato, Irish
Potato, sweet
Radish
Spinach
Squash, summer
Squash, winter
Strawberry
Tomato
Turnip
Watermelon


Crop nutrient requirements1'2
N-P205-KO
Lb/A
60-80-80
90-120-120
90-120-120
90-120-120
110-150-150
120-160-160
110-150-150
110-150-150
200-300-300
110-150-150
110-150-150
90-120-120
90-120-120
120-160-160
110-150-150
120-160-160
110-150-150
110-150-150
120-120-120
60-80-80
60-80-80
160-160-160
150-120-140
60-120-120
90-120-120
90-120-120
90-120-120
90-120-120
120-160-160
160-160-160
110-150-150
120-160-120


Footnotes
3
3
3
3
3,4,5,10
3,4,5,10
3
3,4,5,10
3,10
3,10
3
3
3,4,5
3,4,5,10
3,10,11
3,4,5,10
3
3
3
3
3
3,4,5,7,10
3
3
3,6,9
3
3,4,5
3,4,5
5,7,8
3,4,5,7,10
3
3,4,5,10


Footnotes:
1These amounts should be applied as fertilizer only to soils testing
"very low" in P and K. Use a soil test to determine precisely how
much fertilizer is needed.
2Additional supplemental sidedress applications of 30 ib N and 20
Ib K20 should be applied only after rainfall/irrigation amounts ex-


ceed 2- to 3-inches within a 3-day period or 4 inches within a 7-day
period. Avoid mechanical damage to plants when applying sidedress
fertilizers.
3Fertilizer should be applied in split applications in order to reduce
leaching losses and to lessen danger of fertilizer burn. Broadcast
in the bed or band all P20s and micronutrients, if any, and 25% to
50% of the N and K20 at planting. Apply remaining N and K20 in
sidedress bands during the early part of the growing season.
4For mulched, subsurface-irrigated crops, incorporate 10% to 20%
of the N and K20, plus all of the P205 and micronutrients, if any,
in the bed. Apply the remainder of the N and K20 one inch deep
in bands about 6 to 10 inches from the plant row. For mulched,
overhead-irrigated crops, incorporate all of the N, P205, K20, and
micronutrients, if any, in the bed prior to installation of the mulch.
sFor drip irrigation, incorporate 20% to 40% of the N and K20 and
all of the P20s and micronutrients, if any, in the bed. Apply the re-
mainder of the N and K20 periodically though drip tubes according
to the rate of crop growth and development. For management
systems where both subsurface and drip irrigation are used, apply
no more than 20% of the N and K20 in the bed before mulching.
6Apply all fertilizer prior to or at planting.
7From 25% to 30% of the N may be supplied from slow-release N
sources, such as sulfur-coated urea or isobutylidene-diurea (IBDU).
Due to higher N efficiency with slow-release N sources, it might be
possible to reduce the overall N-fertilizer amount by about 15% to
20%.
8Apply all P20s and micronutrients, if any, and 25% of the N and
K20, in the bed. Place the remaining N and K20 in a band 2- to
3-inches deep in the center of the bed.
9Usually adequate for 2 to 3 crops in succession.
lOTransplants might benefit from application of starter-fertilizer solu-
tion, especially under cool soils.
"Ilncludes head, leaf, and romaine lettuces, in addition to escarole
and endive.





Nutrient requirements

Plants require 16 elements (C, H, O, P, K, N, S, Ca,
Mg, Fe, B, Mn, Cu, Zn, Mo, Cl) for normal growth and
reproduction. The crop nutrient requirement (CNR)
for a particular element is defined as the total
amount in lb/A of that element needed by the crop
to produce economic optimum yield. This concept of
economic optimum yields is important for vegetables
because a certain amount of nutrients might produce
a moderate amount of biomass, but produce negligi-
ble marketable product due to small fruit size. Fruit
size and quality must be considered in the crop
nutrient requirement concept for vegetables.
The crop nutrient requirement can be satisfied
from many sources, including soil, water, air, organic
matter, or fertilizer. For example, the CNR of
potassium (K) can be supplied from K-containing
minerals in the soil, from K retained by soil organic
matter, or from K fertilizers.








The CNR for a crop is determined from field ex-
periments that test the yield response to levels of
added fertilizer. For example, a watermelon study
involving K might be conducted on a soil which tests
very low in extractable K. In this situation, the soil
can be expected to contribute only a small amount
of K for optimum watermelon growth and yield and
K must be supplied largely from fertilizer. The re-
searcher plots the relationship of crop yield to fer-
tilizer rate. The CNR is equivalent to the'fertilizer
rate above which no significant increases in yield are
expected. The CNR values derived from such ex-
periments take into account factors such as fertilizer
efficiencies of the soils. These efficiencies include
fertilizer leaching or fertilizer nutrient fixing
capability of the soil. If data are available from
several experiments, then reliable estimates of CNR
values can be made.
In Florida, CNR values vary according to the type
of soil and vegetable crop and have been determined
for many vegetable crops on several soils in Florida.
For other situations, CNR values are those that have
been published in previous Extension circulars deal-
ing with fertilizer management for vegetables. Tables
1 through 4 present CNR values as we currently
understand them for vegetable crops in Florida. Us-
ing the CNR concept when developing a fertilizer
program will ensure optimum, economic yields while
minimizing both pollution from overfertilization and
loss of yield due to underfertilization.





Soil testing

The CNR values listed in Tables 1 through 4 are
those amounts of nutrients needed to produce op-
timum, economic yields from a fertilization stand-
point. It is important to remember that these
amounts of nutrients are supplied to the crop from
both the soil and the fertilizer. The amounts listed
in the tables are applied as fertilizers only when a
properly calibrated soil test indicates very small ex-
tractable amounts of these nutrients to be present
in the soil. Therefore, soil testing must be conducted
to determine the exact contribution from the soil to
the overall CNR. Based on such tests, the amount of
fertilizer that is needed to supplement the nutrition
component of the native soil can be calculated.
It is important that soil samples represent the field
or management unit to be fertilized. A competent soil
testing laboratory that uses calibrated methodologies
should analyze the samples. Not all laboratories can
provide accurate fertilizer recommendations for


Florida soils. Details on soil testing and how to make
it work effectively can be found in Extension Cir-
cular 596, "Procedures Used by the IFAS Extension
Soil Testing Laboratory, and Interpretations of
Results."




Table 2. Crop nutrient requirements for N, P, and K
for vegetables grown on irrigated organic soils.


Crop
Beans, bush
Beans, pole
Beans, lima
Beets
Broccoli
Cabbage
Carrots
Cauliflower
Celery
Chinese cabbage
Collards
Corn, sweet
Cucumber
Eggplant
Endive
Lettuce
Muskmelon
Mustard
Okra
Onions
Peas, English
Peas, southern
Pepper
Potato, Irish
Potato, sweet
Radish
Spinach
Squash, summer
Squash, winter
Strawberry
Tomato
Turnip
Watermelon


Crop nutrient requirements
N-P20s-K20
Lb/A
0-60-120
0-120-180
0-120-180
0-120-180
0-120-180
0-120-180
0-180-180
0-120-180
0-200-360
0-100-120
0-100-120
0-120-180

0-120-240
0-100-180
0-120-240

0-100-180
0-80-120
0-120-180
0-120-200
0-100-150
0-160-240
0-160-240

0-160-240
0-100-120
0-100-120
0-100-120


0-100-150


Footnotes
3,5
3,5
3,5
3,5
3,5
3,5
3,5
3,5
3,5
3,5
3,5
3,5
4
3,5,
3,5,6
3,5,7
4
3,5
3,5
3,5
3,5
3,5
3,5
3,5
4
3,5
3,5
3,5
3,5
4
4
3,5
4


Footnotes:
1These amounts should be applied as fertilizer only to soils testing
"very low" in P and K. Use a soil test to determine precisely how
much fertilizer is needed.
2These CNR values are sufficient for normal conditions. Most crops
will respond to supplemental applications of 30 to 40 Ib of nitrate-N
per acre during periods of cool weather or after a leaching rain.
30n new peat soils, make a broadcast application of 11 Ib of Cu/A,
7 Ib of Mn/A, and 1 Ib of B/A before the crop is planted. Use a soil
test to determine needs for further micronutrient applications.
4These crops not recommended for production on organic soils.
SApply all fertilizer broadcast prior to planting.
6lncludes escarole and chicory.
71ncludes head, leaf, and romaine.










Irrigation

Fertilizer and water management programs are
linked. Optimum management of one program re-
quires proper management of the other as well.
Overhead irrigation generally causes the
downward movement of nutrients such as nitrogen
(N) and K. Small amounts of irrigation water applied
on a regular basis will result in less leaching than will
large amounts applied infrequently. Excessive irriga-
tion can even remove fertilizer from plastic-mulched
beds, especially from the soil near the plant hole.
The water table in a subsurface (seep) irrigation
system should be maintained 13- to 15-inches below
the top of the bed. The water table should not be
fluctuated appreciably because nutrients can be lost
from the bed during fluctuations. High water tables
after heavy rains should also be lowered quickly to
avoid leaching of nutrients from flooded beds.
Drip irrigation provides an optimum method for ap-
plying water and nutrients, especially if used in con-
junction with mulch. Savings of water of more than
50%, compared to either seepage or overhead irriga-
tion methods, have been reported. However,
nutrient leaching can be severe with an improperly
managed drip system. For more information on drip
irrigation management, refer to Extension Circulars
606 and 607.




Supplemental fertilizer

If the CNR component supplied through fertiliza-
tion is properly managed in relation to irrigation and
fertilizer application timing, it is unlikely that sup-
plemental fertilizer will be needed. Supplemental
fertilizer may be needed after a leaching rainfall,
during which, about 50% of the N and 25% of the
K would be leached out of the root zone by a 2- to
3-inch rainfall under unmulched culture.
Supplemental applications, in general, should
supply approximately 30 lb N/A. Since leaching of
K is not as great as that of N, only about 20 lb KO20/A
is required in a typical supplemental application. The
number of supplemental applications will vary ac-
cording to the number of leaching rainfalls and the
length of the crop growing season.
Supplemental fertilizer should be applied in bands
to each side of the row for unmulched crops. The fer-
tilizer should be placed in the soil just ahead of the
advancing root tips. For crops growing in close rows


or in broadcast fashion, the supplemental fertilizer
can be broadcast over the top by air, ground
spreader, or overhead sprinkler-irrigation system.
Where plastic mulch is used, supplemental applica-
tions can be made through the mulch by a liquid in-
jection wheel or through the drip irrigation system.
Whenever applying supplemental fertilizer, the
equipment must be calibrated carefully. Fertilizer
placement is important in order to avoid damage to
either plants or roots from the application
equipment.




Mulched crops

Mulching is a standard practice for the production
of many vegetable crops in Florida. Polyethylene
mulch improves fumigant effectiveness, increases
weed control, increases soil temperature, and
reduces fruit rot. In addition, mulch can reduce fer-
tilizer leaching. Even though crop growth and pro-
duction are often greater with mulch, the increased
fertilizer efficiency of mulch culture means that CNR
requirements for the mulch system are not higher
than for unmulched crops. Therefore, CNR values in
Tables 1 through 4 apply to both unmulched and
mulched crops. The difference is in the application
of the fertilizer in each system. In unmulched
cultures, split applications of N and K should be used,
but in mulched systems, all N and K can be placed
under the mulch when the mulch is applied to the
bed.
Extra, or insurance fertilizer under the mulch is
not recommended. It can cause soluble-salt injury to
plants and can also contribute to groundwater pollu-
tion if it is leached from under the mulch by flooding
or by a high water table.




Soil pH

Current IFAS standardized recommendations call
for maintaining soil pH in the range of 6.0 to 6.5.
However, some vegetables, such as watermelon, will
perform normally at lower pH values as long as large
amounts of micronutrients are not present in the soil.
A common problem in Florida has been overliming,
resulting in high soil pH levels. Overliming and
resulting high soil pH can cause tie-up of
micronutrients and restrict their availability.to the









Table 3. Crop nutrient requirements for N, P, and K
for vegetables grown on irrigated marl soils.


Crop
Beans, bush
Beans, pole
Beans, lima
Beets
Broccoli
Cabbage
Carrots
Cauliflower
Celery
Chinese cabbage
Collards
Corn, sweet
Cucumber
Eggplant
Endive
Lettuce
Muskmelon
Mustard
Okra
Onions
Peas, English
Peas, southern
Pepper
Potato, Irish
Potato, sweet
Radish
Spinach
Squash, summer
Squash, winter
Strawberry
Tomato
Turnip
Watermelon


Footnotes:
1These amounts should be applied as fertilizer only to soils testing
"very low" in P and K. Use a soil test to determine precisely how
much fertilizer is needed.
2Make a supplemental sidedress application to unmulched crops of
30-0-20 Ib N-P205-K20/A after any rainfall that amounts to 2- to
3-inches in a 7-day period. Use a liquid-injection wheel or drip ir-
rigation to apply supplemental fertilizer to mulched crops. Sup-
plemental applications will probably not be needed on mulched crops
unless flooding occurs. Crops might respond to a sidedress-band
application of P during cool periods.
3For unmulched crops, apply all P and micronutrients before or at
planting. Increased efficiency of plant use of these nutrients might
be realized by banding these nutrients in the soil to the side of the
row. Apply 25% to 50% of the N and K at planting, or sidedress at
crop emergence. Apply the remainder of the N and K in 2 to 3 split
applications during the growing season.
4For mulched crops, apply 25% to 50% of the fertilizer broadcast
in the bed and the remainder in bands prior to installing the mulch.
sFor drip-irrigated crops apply all P and micronutrients, and 20%
to 40% of the N and K, in the bed. Apply the remaining N and K
through the drip system.


6Apply all fertilizer prior to or at planting.
7lncludes escarole and chicory.
slncludes head, leaf, and romaine.


Crop nutrient requirements1'2
N-P205-K20
Lb/A
45-60-60
70-100-100
60-80-80
60-80-80
90-80-100
90-80-100
90-80-100
90-80-100
90-80-100
90-80-100
90-80-100
80-70-80
80-60-90
80-70-100
80-70-80
80-70-80
90-80-100
80-70-80
80-70-100
80-70-100
50-70-70
50-70-70
80-70-100
60-120-120
40-80-80
45-60-60
80-70-80
45-60-60
45-60-60
90-120-120
120-160-160
80-70-80
90-80-100


Footnotes
3
3
3
3
3
3
3
3,4
3
3
3
3
3,4
3,4
3,7
3,8
4
3
3
3
3
3
3,4
3
3
6
3
3
3
4,5
3,4,5
3
3,4


crop. Overliming also can reduce the accuracy with
which a soil test can predict the fertilizer component
of the CNR.
It is important, however, not to allow soil pH to
drop below approximately 5.5 for most vegetable
production, especially where micronutrient levels in
the soil may be high due to a history of micronutrient
fertilizer and micronutrient-containing pesticide ap-
plications. When soil pH decreases in such soils, the
solubility of micronutrients can increase to levels
that may become toxic to plants.
Irrigation water from wells supplied by limestone
aquifers is an additional source of liming material
usually not considered in many liming programs. The
combination of routine additions of lime and use of
alkaline irrigation water has resulted in soil pH
values greater than 8.0 for many sandy soils in
southern Florida. To measure the liming effect of ir-
rigation, have a water sample analyzed for total
bicarbonates and carbonates, and the results con-
verted to pounds of calcium carbonate per acre an-
nually. Include this information in your decisions
concerning lime.
It should be evident that liming, fertilization, and
irrigation programs are closely related to each other.
An adjustment in one program will often influence
the other. To maximize overall production efficiency,
soil and water testing must be made a part of any
fertilizer management program.






Nutrient forms

Nitrogen can be supplied in both nitrate and am-
moniacal forms. Nitrate-nitrogen is generally the
preferred form for plant uptake in most situations,
but ammoniacal N can be absorbed by some plants
directly or after conversion td nitrate-N by soil
microbes. Since this rate of conversion is reduced in
cold, fumigated, or strongly acidic soils, it is recom-
mended that under such conditions 25% to 50% of
the N be supplied from nitrate sources. This ratio is
not as critical for unfumigated or warm soils. For
more information on nutrient sources, consult Ex-
tension Circular 225-C.










Table 4. Crop nutrient requirements for N, P, and K
for vegetables grown on irrigated Rockdale soils.


Crop
Beans, bush
Beans, pole
Beans, lima
Beets
Broccoli
Cabbage
Carrots
Cauliflower
Celery
Chinese cabbage
Collards
Corn, sweet
Cucumber
Eggplant
Endive
Lettuce
Muskmelon
Mustard
Okra
Onions
Peas, English
Peas, southern
Pepper
Potato, Irish
Potato, sweet
Radish
Spinach
Squash, summer
Squash, winter
Strawberry
Tomato
Turnip greens
Watermelon


Crop nutrient requirements1'2
N-P,20-K20
Lb/A
45-60-60
70-90-90
70-90-90

70-90-90
70-90-90

70-90-90
90-120-120
70-90-90
70-90-90
70-60-90
70-90-90
70-90-90
70-90-90
70-90-90
70-90-90
70-90-90
70-90-90
70-90-90
60-90-90
60-90-90
70-90-90

30-60-70

70-90-70
70-90-90
70-90-90
90-120-120
120-200-180
70-90-90
70-90-90


Footnotes
4
4
4
3
4,5,6,7
4,5
3
4,5,6,7
4
4
4
4
4,5
4,5,7
4,8
4,9
4,5
4
4
4
4
4
4,5,7
3
4
3
4
4
4
5,6,7
4,5,6,7
4
4,5


Footnotes:
1These amounts should be applied as fertilizer only to soils testing
"very low" in P and K. Use a soil test to determine precisely how
much fertilizer is needed.
2Make a supplemental application to unmulched crops of 30-0-20
Ib N-P20s-K20/A after any rainfall or excessive irrigation amounting
to 2 to 3 inches in a 7-day period. Use a liquid-injection wheel or
drip irrigation to apply supplemental fertilizer to mulched crops. Sup-
plemental applications will probably not be needed for mulched crops
unless flooding occurs. Crops might respond to a banded supplemen-
tal application of 30 Ib. P20s/A in cool periods.
3These crops not recommended for commercial production on
Rockdale soils.
4For unmulched crops, apply all P and micronutrients before or at
planting. These nutrients can be broadcast and incorporated in the
bed; however, increased efficiency in plant uptake of nutrients might
result from banding the fertilizer in the soil to the sides of the row.
Apply 25% to 50% of the N and K at planting, or sidedress at crop
emergence. Apply the remainder of the N and K in 2 to 3 split ap-
plications during the growing season.
sFor mulched crops, apply all fertilizer in the bed either broadcast
or 25% broadcast and the remainder banded in the soil to the sides
of the row prior to installing the mulch.


5


6For drip-irrigated crops, apply all P and micronutrients, and 20%
to 40% of the N and K, in the bed. Apply remaining N and K through
the drip system.
7When transplanting into cool soils, benefit might result from applica-
tion of starter-fertilizer solution with the transplant.
8Includes escarole and chicory.
91ncludes head, leaf, and romaine.



Phosphorus (P) can be supplied from several
sources, including normal and triple superphosphate,
diammonium phosphate, and monoammonium phos-
phate. All sources can be effective for plant nutri-
tion on sandy soil. However, on soils that test very
low in native micronutrient levels, diammonium
phosphate has been shown to reduce yields when
banded in large amounts in mixtures containing
micronutrients. Negative effects of diammonium
phosphate can be minimized by using diammonium
phosphate for only a portion of the P requirements
and by broadcasting this material in the bed.
Potassium can also be supplied from several
sources, including potassium chloride, potassium
sulfate, potassium nitrate, and potassium-magnesium
sulfate. If soil-test-predicted amounts of K fertilizer
are adhered to, there should be no concern about the
K source or its relative salt index.





Secondary nutrients

The secondary nutrients such as calcium (Ca),
magnesium (Mg), and sulfur (S) have not commonly
been a problem in Florida. Calcium usually occurs in
adequate supply for most vegetables when soil pH
is maintained at 5.5 or above. If the Mehlich-I soil
Ca index is above 250 ppm, it is unlikely that there
will be a response to added Ca. Maintaining correct
moisture levels in the soil by irrigation will aid in Ca
supply to the roots. Calcium is not mobile in the
plant; therefore, foliar sprays of Ca are not likely to
correct serious deficiencies. It is difficult to place
enough foliar-applied Ca at the growing point of the
plant on a timely basis.
Sulfur deficiencies have not been documented for
Florida vegetables. Sulfur deficiency would most
likely occur on deep, sandy soils low in organic mat-
ter, after leaching rains. If. S deficiency has been
diagnosed, it can be corrected by using S-containing
fertilizers such as magnesium sulfate, potassium
sulfate, normal superphosphate, or potassium-
magnesium sulfate. Using one of these materials in









Table 5. List of University of Florida extension publi-
cations pertaining to crop production and fertilization.
Publication
Topic number Title of publication
Beans Circ. 100 Bean Production Guide
Broccoli Circ. 555 Broccoli and Cauliflower
Production in Florida
Cabbage Circ. 117 Cabbage Production Guide
for Florida
Cauliflower Circ. 555 Broccoli and Cautiflower
Production in Florida
Corn, sweet Circ. 99 Sweet Corn Production in
Florida
Cucumber Circ. 101 Cucumber Production Guide
for Florida
Eggplant Circ. 109 Eggplant Production Guide
Fertilization Circ. 225-C Commercial Vegetable
Fertilization Guide
Bull. 183-C Fertilizers and Fertilization
Lettuce Circ. 123 Lettuce and Endive
Production Guide
Muskmelon Circ. 122 Muskmelon Production
Guide for Florida
Okra Circ. 492 Okra in Florida
Onions Circ. 176 Onion Production Guide
Peas, Southern Circ. 478 The Southern Pea in Florida
Pepper Circ. 102 Pepper Production Guide for
Florida
Potato, Irish Circ. 118 Potato Production Guide
Potato, Sweet Circ. 551 Sweet Potatoes in Florida
Squash Circ. 103 Squash Production in Florida
Strawberry Circ. 142 Strawberry Production Guide
for Florida
Tomato Circ. 98 Tomato Production Guide for
Florida
Watermelon Circ. 96 Watermelon Production in
Florida


Micronutrients

It has been common practice in Florida vegetable
production to routinely apply a micronutrient
package. This practice has been justified in the past
on the basis that these nutrients were inexpensive,
and their application was viewed as insurance for
high yields. In addition, there has been little research
data and a lack of soil-test calibrations to guide
judicious application of micronutrient fertilizers.
Compounding the problem has been the vegetable
industry's use of micronutrient-containing pesticides
for disease control. Micronutrients, such as copper
(Cu), manganese (Mn), and zinc (Zn), from these
sources have tended to accumulate in the plow zone
of the soil.
This situation has forced some vegetable producers
to overtime in an effort to avoid micronutrient tox-
icities. Data have now been accumulated which per-
mit a more accurate assessment of micronutrient re-
quirements. Growers are encouraged to have a
calibrated micronutrient soil test conducted and to
refrain from shotgun micronutrient fertilizer applica-
tions. It is unlikely that micronutrient fertilizers will
be needed on old vegetable land, especially where
micronutrients are being applied regularly via recom-
mended pesticides. A micronutrient soil test every
2- to 3-years should help provide adequate
micronutrient levels for crop production.


the fertilizer blend at levels sufficient to supply 30
to 40 lb S/A should prevent S deficiencies. In many
areas of Florida, ample S will be supplied to vegetable
crops through the irrigation water because sulfur can
be present in the aquifer.
Magnesium deficiency may be a problem for
vegetable production; however, when the Mehlich-I
soil-test index for Mg is below 15 ppm, research has
shown that 30 lb Mg/A will satisfy the Mg CNR for
several years. If lime is also needed, Mg can be add-
ed by using dolomite as the liming material. If no lime
is needed, then the Mg requirement can be satisfied
through use of magnesium sulfate or potassium-
magnesium sulfate. Blending of the Mg source with
other fertilizer(s) to be applied to the soil is an ex-
cellent way of ensuring uniform application of Mg
to the soil.


Placement and timing

Because phosphorus (P) is considered immobile in
the soil, it should be placed in the bed and not on
the surface of the bed. Efficiency in P-fertilizer use
may be enhanced by reducing the amount of soil with
which the fertilizer is mixed. This statement is
especially true for the alkaline marl and Rockdale
soils of southern Florida. Banding or incorporating
P in the bed area are excellent methods of increas-
ing P efficiency.
In most situations, all P should be applied before
planting. Side-dressing of P in bands might be need-
ed on the marl or Rockdale soils during winter to in-
crease P availability to the slow-growing roots.
Nitrogen and, to a lesser extent, K can leach in san-
dy soils which are low in organic matter or clay con-
tent. Therefore, these nutrients should be applied to


6








unmulched crops in split applications to reduce
leaching losses and to reduce soluble-salt injury. For
muck soils, K can be broadcast at planting time with
the P.
Most micronutriefits are essentially immobile in soil
and should be managed like P. Foliar applications of
Mn, Fe, Cu, and Zn can be used to correct deficien-
cies which might occur on alkaline soils during cool
periods.




Liquid vs. dry fertilizer

Research in Florida has shown that there is no dif-
ference in response of crops to similar amounts of
nutrients when applied in either liquid or dry form.
Certain situations (use of drip irrigation or injection
wheel) require clear or true solutions. However,
sidedress applications of fertilizer can be made equal-
ly well with dry or liquid forms of nutrients.
The decision to use liquid or dry fertilizer sources
should depend largely on economics and on the type
of application equipment available. The cost per unit
of nutrient (e.g., dollars per ton of actual N) should
be used in any decision-making process.


Foliar fertilization


Foliar fertilization should be thought of as a last
resort for correcting a deficiency. The plant leaf is
structured in such a way that it naturally resists easy
infiltration by fertilizer salts. Foliar fertilization most
appropriately applies to micronutrients and not to
macronutrients such as N, P, and K. Research has
shown that foliar applications of N, P, and/or K are
not needed where proper soil-directed fertilizer pro-
grams are being followed. Leaves cannot absorb
enough of these nutrients (without burning the
leaves) to correct any significant deficiency. Any
benefit from macronutrient foliar sprays probably
results when nutrients are washed by rain or irriga-
tion water off of the leaf surface into the soil. The
nutrient then enters the plant via the plant roots.
Amounts of macronutrients recommended on the
label of most commercial foliar products are so
minuscule compared to nutrition derived from the
soil that benefit to the plant is highly unlikely. Ad-
ditionally, fertilizer should only be added if addi-


tional yield results, and research with foliar-nutrient
applications has not clearly documented a yield in-
crease for vegetables.
In certain situations, temporary deficiencies of Mn,
Fe, Cu, or Zn can be corrected by foliar application.
Examples include vegetable production in winter
months when soils are cool and roots cannot extract
adequate amounts of micronutrients, and in cases
where high pH (marl and Rockdale soils) fixes broad-
casted micronutrients into unavailable forms.
Micronutrients are so termed because small, or
micro, amounts are required to satisfy the CNR. Such
micro amounts may be supplied adequately through
foliar applications to correct a temporary deficiency.
Boron is highly immobile in the plant. To correct
boron deficiencies, small amounts of boron must be
applied frequently to the young tissue or buds.
Any micronutrient should be applied only when
a specific deficiency has been clearly diagnosed. Do
not make shotgun applications of micronutrients.
There is a fine line between adequate and toxic
amounts of these nutrients. Shotgun application of
micronutrients can actually reduce plant growth and
rob yields because of toxicity. Compounding the pro-
blem is the fact that the micronutrients will end up
in the soil where they can accumulate to levels which
may threaten crop production on that soil. An im-
portant part of any micronutrient program involves
careful calculations of all micronutrients being ap-
plied, from all sources.




Double-cropping

Successive cropping of existing mulched beds is a
good practice in order to make effective use of the
polyethylene mulch and fumigant. Double-cropping
also can make use of residual fertilizer in the beds.
If fertilizer-N applications and amounts were proper-
ly managed for the first crop, then there should be
negligible amounts of fertilizer-N remaining in the
beds. It is not a good practice to add extra fertilizer
to the beds when planting the first crop, thinking
that this fertilizer will aid growth of the second crop.
The extra fertilizer could contribute to soluble-salt
damage to the first crop, and might still be leached
from the root zone before the second crop is
established.
If double-cropping is to be practiced, then a drip-
irrigation system could be used to supply adequate
nutrition to each crop. In most cases, only N and K


7








may be needed for the second crop. Amounts of P
and micronutrients (if any) used for the first crop will
likely remain adequate for the second crop as well.
Soil testing of a sample taken from the bed away
from any fertilizer bands will help determine P or
micronutrient needs, assuming that these nutrients
were broadcast in the bed prior to planting the first
crop.
If N for the first crop was not applied jn excess of
the CNR, then the second crop should receive an
amount of N equal to its own CNR. Potassium re-
quirements of the second crop can be determined as
for P in cases where the K for the first crop was in-
corporated in the bed. Potassium requirements for
the second crop are more difficult to determine in
cases where K for the first crop was banded. A
moderate amount of residual K will probably remain
in the bed from the application to the first crop.
Therefore, K requirements for the second crop will
likely be slightly less than the CNR value for the
chosen crop.
Once the crop fertilizer requirements have been
ascertained, the needed nutrition may be applied
through the drip system. Where drip irrigation is not
being used, a liquid injection wheel can be used to
place fertilizer in the bed for the second crop.












































































Reprinted August 1990



COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, John T.
Woeste, director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the
May 8 and June 30, 1914 Acts of Congress; and is authorized to provide research, educational information and other services only to
individuals and institutions that function without regard to race, color, sex, age, handicap or national origin. Single copies of extension
publications (excluding 4-H and youth publications) are available free to Florida residents from county extension offices. Information on bulk
rates or copies for out-of-state purchasers is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of
Florida, Gainesville, Florida 32611. Before publicizing this publication, editors should contact this address to determine availability.




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