• TABLE OF CONTENTS
HIDE
 Copyright
 Introduction
 Important consideration in the...
 Soil injection of iron chelate...
 Equipment
 Amount of chelate per tree
 Procedure
 Uniform distribution of chelate...
 Efficiency of the injection...
 Discussion
 Conclusions and recommendation...














Group Title: AREC-H research report - Agricultural Research and Education Center-Homestead ; SB-74-2
Title: The soil injection method of chelate application in calcereous soils of the Homestead area
CITATION PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00067830/00001
 Material Information
Title: The soil injection method of chelate application in calcereous soils of the Homestead area
Series Title: Homestead AREC research report
Physical Description: 4 leaves : ; 28 cm.
Language: English
Creator: Malo, Simâon E
Agricultural Research and Education Center, Homestead
Publisher: University of Florida, Agricultural Research and Education Center
Place of Publication: Homestead Fla.
Publication Date: 1974
 Subjects
Subject: Chelates -- Florida   ( lcsh )
Soils -- Nutrition -- Florida -- Miami-Dade County   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: S. E. Malo.
General Note: "February 15, 1974."
 Record Information
Bibliographic ID: UF00067830
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 72444193

Table of Contents
    Copyright
        Copyright
    Introduction
        Page 1
    Important consideration in the use of iron chelates
        Page 1
    Soil injection of iron chelates
        Page 2
    Equipment
        Page 2
    Amount of chelate per tree
        Page 2
    Procedure
        Page 3
    Uniform distribution of chelate treatments around a tree
        Page 3
    Efficiency of the injection method
        Page 3
    Discussion
        Page 4
    Conclusions and recommendations
        Page 4
Full Text





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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
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(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida





SHomestead AREC Research Report SB74-2 February 15, 1974

tTHE SOIL INJECTION METHOD OF CHELATE APPLICATION IN
S4AREOUS SOILS OF THE HOMESTEAD AREA

HUME LIBRARY
S. E. Malo
Associate Horticulturist
APR 1 1974 University of Florida
Inst tute of Food and Agricultural Sciences
Agri cultural Research and Education Center

S Ur'V. o Florida Homestead
i ....INTRODUCTION

Under the present fertilizer programs iron deficiency is perhaps the most critical
nutritional factor affecting orchards in the Homestead area. All other needed
elements can be supplied to trees without difficulty, particularly those constituting
the major ingredients of commercial fertilizers nitrogen (N), phosphorus (P), potas-
sium (K) and magnesium (Mg). Minor elements such as zinc (Zn), manganese (Mn) and
boron (B) are readily supplied to fruit trees if the grower is careful to include
them in his regular annual spray program. Most fruit crops cannot absorb iron
through the leaves, consequently it must be added to the soil to let the plant roots
take it up. Experience, but particularly research, has shown that very few iron
sources are effectively used by plants in calcareous soils when supplied in this
manner. The high pH of this soil inactivates all but a few iron sources by changing
them almost instantaneously from the soluble ferrous (Fe++) form to the insoluble and
therefore unavailable ferric (Fe--+) form. Many years of research into the nature of
iron chlorosis in the Homestead area has shown that, although a few chelates and
chelate combinations have the ability to supply iron to enable chlorotic trees to
. turn green, only one brings about the highest yield response needed to give a profit-
able return to the grower. This chelate is Sequestrene 138 (Ferric chelate of
Ethylenediamine (di(O-hydroxyphenylacetate, or HFe EDDHA for short).

Important considerations in the use of Iron chelates.

A. Sequestrene 138 and other chelates breakdown when exposed to sunlight and thus
should be applied in such a way as to protect them from direct exposure to sunlight.

B. To be effective chelates must be chemically stable in calcareous soils. Seques-
trene 138 remains chemically active longer than most other chelates, thus increasing
the chances of root absorption.

C. The chelate should be as soluble as possible so that it can spread itself better
by capillary action throughout the soil particles and come in contact with roots to
be absorbed immediately.

D. Studies in avocado groves show that the root system of chlorotic trees is rather
small, weak and generally confined to the area around the trunk. The abundance of
feeder roots of most avocado trees fluctuates in shallow Rockdale soils according to
the prevailing rainfall. It increases as the summer rains progress, reaching a peak
at the end of the rainy season in October. After October the root population decline
progressively, attaining their minimum spread during May or just before the beginning
of the rainy season. This appears to happen even if sprinkler irrigation is available
although to a lesser degree.

* E. It is commonly observed that the incidence of chlorosis oscillates throughout the
year and seems to coincide and be directly associated with periods of low root devel-
opment brought about by climatic and physiological factors, and also by grove prac-
tices. New growth in severely pruned trees, such as those which have been hedged and





SHomestead AREC Research Report SB74-2 February 15, 1974

tTHE SOIL INJECTION METHOD OF CHELATE APPLICATION IN
S4AREOUS SOILS OF THE HOMESTEAD AREA

HUME LIBRARY
S. E. Malo
Associate Horticulturist
APR 1 1974 University of Florida
Inst tute of Food and Agricultural Sciences
Agri cultural Research and Education Center

S Ur'V. o Florida Homestead
i ....INTRODUCTION

Under the present fertilizer programs iron deficiency is perhaps the most critical
nutritional factor affecting orchards in the Homestead area. All other needed
elements can be supplied to trees without difficulty, particularly those constituting
the major ingredients of commercial fertilizers nitrogen (N), phosphorus (P), potas-
sium (K) and magnesium (Mg). Minor elements such as zinc (Zn), manganese (Mn) and
boron (B) are readily supplied to fruit trees if the grower is careful to include
them in his regular annual spray program. Most fruit crops cannot absorb iron
through the leaves, consequently it must be added to the soil to let the plant roots
take it up. Experience, but particularly research, has shown that very few iron
sources are effectively used by plants in calcareous soils when supplied in this
manner. The high pH of this soil inactivates all but a few iron sources by changing
them almost instantaneously from the soluble ferrous (Fe++) form to the insoluble and
therefore unavailable ferric (Fe--+) form. Many years of research into the nature of
iron chlorosis in the Homestead area has shown that, although a few chelates and
chelate combinations have the ability to supply iron to enable chlorotic trees to
. turn green, only one brings about the highest yield response needed to give a profit-
able return to the grower. This chelate is Sequestrene 138 (Ferric chelate of
Ethylenediamine (di(O-hydroxyphenylacetate, or HFe EDDHA for short).

Important considerations in the use of Iron chelates.

A. Sequestrene 138 and other chelates breakdown when exposed to sunlight and thus
should be applied in such a way as to protect them from direct exposure to sunlight.

B. To be effective chelates must be chemically stable in calcareous soils. Seques-
trene 138 remains chemically active longer than most other chelates, thus increasing
the chances of root absorption.

C. The chelate should be as soluble as possible so that it can spread itself better
by capillary action throughout the soil particles and come in contact with roots to
be absorbed immediately.

D. Studies in avocado groves show that the root system of chlorotic trees is rather
small, weak and generally confined to the area around the trunk. The abundance of
feeder roots of most avocado trees fluctuates in shallow Rockdale soils according to
the prevailing rainfall. It increases as the summer rains progress, reaching a peak
at the end of the rainy season in October. After October the root population decline
progressively, attaining their minimum spread during May or just before the beginning
of the rainy season. This appears to happen even if sprinkler irrigation is available
although to a lesser degree.

* E. It is commonly observed that the incidence of chlorosis oscillates throughout the
year and seems to coincide and be directly associated with periods of low root devel-
opment brought about by climatic and physiological factors, and also by grove prac-
tices. New growth in severely pruned trees, such as those which have been hedged and






topped, is often chlorotic and rather stunted for a few weeks after pruning. A
sudden drastic reduction in the foliage of a plant appears to have a direct effect
on the abundance of roots resulting in a proportionate decline in their number.
* Chlorosis also shows up during periods of stress, such as during the height of the
dry season in April and May, or after hurricanes or severe storms when root mortality
appears to be at its highest. Chlorosis is also evident after a heavy crop of fruit
when the tree appears drained of its vitality, apparently because most of its re-
serves are depleted.

Following the onset of the rainy season most chlorotic trees improve gradually, with
the possible exception of a few which were perhaps too far gone to make a normal re-
covery and that linger on for a long time recuperating slowly or dying. Such trees
should never have been allowed to degenerate this far because even with chelate
treatments will remain unproductive one or two-years and sometimes even three years.
At the height of the rainy season there is also some evidence of chlorosis. The rea-
son for this is not clear, but may be caused directly by leaching of soluble iron by
heavy rains from an already low supply.

Soil injection of iron chelates.

Most Fe chelates are readily soluble in water; however, Seq. 138 is a light, finely
divided powder which is very difficult to wet and dissolves only partially even with
good mechanical agitation. The conventional manner of applying Seq. 138 by drenching
it around the chlorotic plant is a slow, rather cumbersome method which is not
suitable for treating a sizeable number of trees in a grove. In search for a more
practical method, we have used a system of injecting the chelate solution into the
soil surrounding the root system of a plant. The consistently good results obtained
with this method, in comparison with other procedures for applying chelates warrants
recommending it to the grower.

Equipment.

The equipment necessary for the injection of chelates can be found in the shop of any
grower with the exception of a specially designed injector. The grower needs a
sprayer, with a tank capacity preferably of 400 or 500 gallons, which could deliver
liquid at 100 psi. One or both of the spray guns are replaced by the injector and
quick-acting valves located at the pump or as part of the injector assembly to control
the flow of liquid.

The injector consists of an 12" solid steel shank(1.0" hot rolled steel stock) in
which a 3/8" canal has been bored to within 2 inches of the pointed tip. This bore
is open to the outside with 4 countersunk evenly spaced outlets 3/16" in diameter
within 2" of the tip. Countersunk performations are less likely to become clogged by
debris or small rocks which cannot be dislodged by the pressure of the outflowing
liquid. The injector is connected to a 3-4 foot shank of 3/4" galvanized pipe by
either welding it or by threading it to a connector. The shank serves as the handle
of the tool and connects it to the hose of the sprayer. A further addition to the
injector assembly is a movable, round steel plate placed as a collar within 4-8" of
the tip. It serves the 3-fold purpose of deflecting liquid, controlling the depth
of the injection and offering a footrest to push down the injector into the soil.
Reliable pressure gauges and quick-acting valves are indispensable to measure accu-
rately the liquid injected.

Amount of chelate per tree.

Recommendations for the amount of Seq. 138 to be used for chlorotic trees have been
discussed in "Correction of iron chlorosis in Homestead, Rockdale soils" (see table
3). AREC, Research Report No. 3 by S. E. Malo. The actual amount needed depends on
the tree's size and condition. Knowing the calibration of the spray pump at a






topped, is often chlorotic and rather stunted for a few weeks after pruning. A
sudden drastic reduction in the foliage of a plant appears to have a direct effect
on the abundance of roots resulting in a proportionate decline in their number.
* Chlorosis also shows up during periods of stress, such as during the height of the
dry season in April and May, or after hurricanes or severe storms when root mortality
appears to be at its highest. Chlorosis is also evident after a heavy crop of fruit
when the tree appears drained of its vitality, apparently because most of its re-
serves are depleted.

Following the onset of the rainy season most chlorotic trees improve gradually, with
the possible exception of a few which were perhaps too far gone to make a normal re-
covery and that linger on for a long time recuperating slowly or dying. Such trees
should never have been allowed to degenerate this far because even with chelate
treatments will remain unproductive one or two-years and sometimes even three years.
At the height of the rainy season there is also some evidence of chlorosis. The rea-
son for this is not clear, but may be caused directly by leaching of soluble iron by
heavy rains from an already low supply.

Soil injection of iron chelates.

Most Fe chelates are readily soluble in water; however, Seq. 138 is a light, finely
divided powder which is very difficult to wet and dissolves only partially even with
good mechanical agitation. The conventional manner of applying Seq. 138 by drenching
it around the chlorotic plant is a slow, rather cumbersome method which is not
suitable for treating a sizeable number of trees in a grove. In search for a more
practical method, we have used a system of injecting the chelate solution into the
soil surrounding the root system of a plant. The consistently good results obtained
with this method, in comparison with other procedures for applying chelates warrants
recommending it to the grower.

Equipment.

The equipment necessary for the injection of chelates can be found in the shop of any
grower with the exception of a specially designed injector. The grower needs a
sprayer, with a tank capacity preferably of 400 or 500 gallons, which could deliver
liquid at 100 psi. One or both of the spray guns are replaced by the injector and
quick-acting valves located at the pump or as part of the injector assembly to control
the flow of liquid.

The injector consists of an 12" solid steel shank(1.0" hot rolled steel stock) in
which a 3/8" canal has been bored to within 2 inches of the pointed tip. This bore
is open to the outside with 4 countersunk evenly spaced outlets 3/16" in diameter
within 2" of the tip. Countersunk performations are less likely to become clogged by
debris or small rocks which cannot be dislodged by the pressure of the outflowing
liquid. The injector is connected to a 3-4 foot shank of 3/4" galvanized pipe by
either welding it or by threading it to a connector. The shank serves as the handle
of the tool and connects it to the hose of the sprayer. A further addition to the
injector assembly is a movable, round steel plate placed as a collar within 4-8" of
the tip. It serves the 3-fold purpose of deflecting liquid, controlling the depth
of the injection and offering a footrest to push down the injector into the soil.
Reliable pressure gauges and quick-acting valves are indispensable to measure accu-
rately the liquid injected.

Amount of chelate per tree.

Recommendations for the amount of Seq. 138 to be used for chlorotic trees have been
discussed in "Correction of iron chlorosis in Homestead, Rockdale soils" (see table
3). AREC, Research Report No. 3 by S. E. Malo. The actual amount needed depends on
the tree's size and condition. Knowing the calibration of the spray pump at a






topped, is often chlorotic and rather stunted for a few weeks after pruning. A
sudden drastic reduction in the foliage of a plant appears to have a direct effect
on the abundance of roots resulting in a proportionate decline in their number.
* Chlorosis also shows up during periods of stress, such as during the height of the
dry season in April and May, or after hurricanes or severe storms when root mortality
appears to be at its highest. Chlorosis is also evident after a heavy crop of fruit
when the tree appears drained of its vitality, apparently because most of its re-
serves are depleted.

Following the onset of the rainy season most chlorotic trees improve gradually, with
the possible exception of a few which were perhaps too far gone to make a normal re-
covery and that linger on for a long time recuperating slowly or dying. Such trees
should never have been allowed to degenerate this far because even with chelate
treatments will remain unproductive one or two-years and sometimes even three years.
At the height of the rainy season there is also some evidence of chlorosis. The rea-
son for this is not clear, but may be caused directly by leaching of soluble iron by
heavy rains from an already low supply.

Soil injection of iron chelates.

Most Fe chelates are readily soluble in water; however, Seq. 138 is a light, finely
divided powder which is very difficult to wet and dissolves only partially even with
good mechanical agitation. The conventional manner of applying Seq. 138 by drenching
it around the chlorotic plant is a slow, rather cumbersome method which is not
suitable for treating a sizeable number of trees in a grove. In search for a more
practical method, we have used a system of injecting the chelate solution into the
soil surrounding the root system of a plant. The consistently good results obtained
with this method, in comparison with other procedures for applying chelates warrants
recommending it to the grower.

Equipment.

The equipment necessary for the injection of chelates can be found in the shop of any
grower with the exception of a specially designed injector. The grower needs a
sprayer, with a tank capacity preferably of 400 or 500 gallons, which could deliver
liquid at 100 psi. One or both of the spray guns are replaced by the injector and
quick-acting valves located at the pump or as part of the injector assembly to control
the flow of liquid.

The injector consists of an 12" solid steel shank(1.0" hot rolled steel stock) in
which a 3/8" canal has been bored to within 2 inches of the pointed tip. This bore
is open to the outside with 4 countersunk evenly spaced outlets 3/16" in diameter
within 2" of the tip. Countersunk performations are less likely to become clogged by
debris or small rocks which cannot be dislodged by the pressure of the outflowing
liquid. The injector is connected to a 3-4 foot shank of 3/4" galvanized pipe by
either welding it or by threading it to a connector. The shank serves as the handle
of the tool and connects it to the hose of the sprayer. A further addition to the
injector assembly is a movable, round steel plate placed as a collar within 4-8" of
the tip. It serves the 3-fold purpose of deflecting liquid, controlling the depth
of the injection and offering a footrest to push down the injector into the soil.
Reliable pressure gauges and quick-acting valves are indispensable to measure accu-
rately the liquid injected.

Amount of chelate per tree.

Recommendations for the amount of Seq. 138 to be used for chlorotic trees have been
discussed in "Correction of iron chlorosis in Homestead, Rockdale soils" (see table
3). AREC, Research Report No. 3 by S. E. Malo. The actual amount needed depends on
the tree's size and condition. Knowing the calibration of the spray pump at a







predetermined psi (gallons/minute of liquid outflow) and the amount needed per tree,
we can calculate the total chelate necessary per tank. For example: If the injector
* delivers 5 gal/minute, a total of 2.0 minutes (120 seconds) would be required to in-
ject 10 gal/tree. Using 4 injections/tree, each receiving 2.5 gal, 30 seconds would
be required per injection. At this rate 500 gallons would treat 50 trees. If 4 oz
of chelate is needed for each tree,then 200 oz (or 12.5 lb) should be put in each
500 gal tank. If 8 injections/tree are necessary, 4 oz of chelate/tree would be ap-
plied by reducing the time per injection to 15 seconds.

Procedure.

The chelate is put in the spray tank and thoroughly agitated to obtain maximum dis-
solution. With materials, such as Seq. 138 which are difficult to wet, a small
amount of a wetting agent helps overcome the surface tension and shortens the time
for dissolution. Once the spray gun (or guns) is replaced by the injector and the
working pressure of the pump is lowered to 80-100 psi, the system is ready for cali-
bration. This is done, at a given pressure, by measuring the number of gallons per
minute collected in a container. The amount of output can be increased by increasing
the pressure or the time of delivery. When actually injecting the chelate solution
it is generally better to use smaller amounts of chelate and a large volume of water
than to use large amounts of chelate in a low gallonage. In our experience, 10-16
gal. of solution in several shots is adequate to wet a good portion of the roots of
a medium sized tree. Less than 10 gal. does not give enough distribution of the
chelate and the response drops considerably. On the other hand, more than 16 gal.
could be wasteful and unnecessary unless the tree is extremely large. The number of
injections per tree also varies with its size. Accordingly, for very small, young
trees (1-2 years old) only one injection is sufficient, increasing to 4 for trees
already in production (3-7 years old) but no more than 8 injections of 2 gal. each
(for a total of 16 gal.) for the largest trees in a grove. The first 4 injections
should be in the quadrants around the tree within 1l feet of the trunk (in the
trenched area if possible). If 8 injections are needed the other 4 should be placed
further out at 2k 3 feet from the trunk between and equidistant from the 4 closer
ones. The operation if accomplished by 2 men, one handling the injector, the other
driving the spraying equipment forward and controlling the amount of injection, if the
control valve is located at the tank. By positioning a control valve at the injector
assembly, 2 hoses could be used to treat two rows of trees simultaneously by a 3 man
crew.

Uniform distribution of chelate treatments around a tree.

Iron chelate treatments should be well distributed around trees otherwise the greening
effect is not uniform throughout the foliage. This occurs because iron, being rela-
tively immobile within the plant, is not translocated from branches in one side to the
opposite. To be effective throughout the top all the roots around the tree must be
involved in the processes of absorption and transport of iron. Roots and their con-
necting xylem vessels in one side of the tree lead to and influence only that part of
the foliage connected to them.

Efficiency of the injection method.

Field comparisons have shown that 500 trees can be treated by the injection method in
24 man-hours compared to 72 man-hours for the drenching method (Table 1). The ef-
ficiency of the injection could even be shortened with capable men, well designed
* equipment and a ready supply of water.







predetermined psi (gallons/minute of liquid outflow) and the amount needed per tree,
we can calculate the total chelate necessary per tank. For example: If the injector
* delivers 5 gal/minute, a total of 2.0 minutes (120 seconds) would be required to in-
ject 10 gal/tree. Using 4 injections/tree, each receiving 2.5 gal, 30 seconds would
be required per injection. At this rate 500 gallons would treat 50 trees. If 4 oz
of chelate is needed for each tree,then 200 oz (or 12.5 lb) should be put in each
500 gal tank. If 8 injections/tree are necessary, 4 oz of chelate/tree would be ap-
plied by reducing the time per injection to 15 seconds.

Procedure.

The chelate is put in the spray tank and thoroughly agitated to obtain maximum dis-
solution. With materials, such as Seq. 138 which are difficult to wet, a small
amount of a wetting agent helps overcome the surface tension and shortens the time
for dissolution. Once the spray gun (or guns) is replaced by the injector and the
working pressure of the pump is lowered to 80-100 psi, the system is ready for cali-
bration. This is done, at a given pressure, by measuring the number of gallons per
minute collected in a container. The amount of output can be increased by increasing
the pressure or the time of delivery. When actually injecting the chelate solution
it is generally better to use smaller amounts of chelate and a large volume of water
than to use large amounts of chelate in a low gallonage. In our experience, 10-16
gal. of solution in several shots is adequate to wet a good portion of the roots of
a medium sized tree. Less than 10 gal. does not give enough distribution of the
chelate and the response drops considerably. On the other hand, more than 16 gal.
could be wasteful and unnecessary unless the tree is extremely large. The number of
injections per tree also varies with its size. Accordingly, for very small, young
trees (1-2 years old) only one injection is sufficient, increasing to 4 for trees
already in production (3-7 years old) but no more than 8 injections of 2 gal. each
(for a total of 16 gal.) for the largest trees in a grove. The first 4 injections
should be in the quadrants around the tree within 1l feet of the trunk (in the
trenched area if possible). If 8 injections are needed the other 4 should be placed
further out at 2k 3 feet from the trunk between and equidistant from the 4 closer
ones. The operation if accomplished by 2 men, one handling the injector, the other
driving the spraying equipment forward and controlling the amount of injection, if the
control valve is located at the tank. By positioning a control valve at the injector
assembly, 2 hoses could be used to treat two rows of trees simultaneously by a 3 man
crew.

Uniform distribution of chelate treatments around a tree.

Iron chelate treatments should be well distributed around trees otherwise the greening
effect is not uniform throughout the foliage. This occurs because iron, being rela-
tively immobile within the plant, is not translocated from branches in one side to the
opposite. To be effective throughout the top all the roots around the tree must be
involved in the processes of absorption and transport of iron. Roots and their con-
necting xylem vessels in one side of the tree lead to and influence only that part of
the foliage connected to them.

Efficiency of the injection method.

Field comparisons have shown that 500 trees can be treated by the injection method in
24 man-hours compared to 72 man-hours for the drenching method (Table 1). The ef-
ficiency of the injection could even be shortened with capable men, well designed
* equipment and a ready supply of water.







predetermined psi (gallons/minute of liquid outflow) and the amount needed per tree,
we can calculate the total chelate necessary per tank. For example: If the injector
* delivers 5 gal/minute, a total of 2.0 minutes (120 seconds) would be required to in-
ject 10 gal/tree. Using 4 injections/tree, each receiving 2.5 gal, 30 seconds would
be required per injection. At this rate 500 gallons would treat 50 trees. If 4 oz
of chelate is needed for each tree,then 200 oz (or 12.5 lb) should be put in each
500 gal tank. If 8 injections/tree are necessary, 4 oz of chelate/tree would be ap-
plied by reducing the time per injection to 15 seconds.

Procedure.

The chelate is put in the spray tank and thoroughly agitated to obtain maximum dis-
solution. With materials, such as Seq. 138 which are difficult to wet, a small
amount of a wetting agent helps overcome the surface tension and shortens the time
for dissolution. Once the spray gun (or guns) is replaced by the injector and the
working pressure of the pump is lowered to 80-100 psi, the system is ready for cali-
bration. This is done, at a given pressure, by measuring the number of gallons per
minute collected in a container. The amount of output can be increased by increasing
the pressure or the time of delivery. When actually injecting the chelate solution
it is generally better to use smaller amounts of chelate and a large volume of water
than to use large amounts of chelate in a low gallonage. In our experience, 10-16
gal. of solution in several shots is adequate to wet a good portion of the roots of
a medium sized tree. Less than 10 gal. does not give enough distribution of the
chelate and the response drops considerably. On the other hand, more than 16 gal.
could be wasteful and unnecessary unless the tree is extremely large. The number of
injections per tree also varies with its size. Accordingly, for very small, young
trees (1-2 years old) only one injection is sufficient, increasing to 4 for trees
already in production (3-7 years old) but no more than 8 injections of 2 gal. each
(for a total of 16 gal.) for the largest trees in a grove. The first 4 injections
should be in the quadrants around the tree within 1l feet of the trunk (in the
trenched area if possible). If 8 injections are needed the other 4 should be placed
further out at 2k 3 feet from the trunk between and equidistant from the 4 closer
ones. The operation if accomplished by 2 men, one handling the injector, the other
driving the spraying equipment forward and controlling the amount of injection, if the
control valve is located at the tank. By positioning a control valve at the injector
assembly, 2 hoses could be used to treat two rows of trees simultaneously by a 3 man
crew.

Uniform distribution of chelate treatments around a tree.

Iron chelate treatments should be well distributed around trees otherwise the greening
effect is not uniform throughout the foliage. This occurs because iron, being rela-
tively immobile within the plant, is not translocated from branches in one side to the
opposite. To be effective throughout the top all the roots around the tree must be
involved in the processes of absorption and transport of iron. Roots and their con-
necting xylem vessels in one side of the tree lead to and influence only that part of
the foliage connected to them.

Efficiency of the injection method.

Field comparisons have shown that 500 trees can be treated by the injection method in
24 man-hours compared to 72 man-hours for the drenching method (Table 1). The ef-
ficiency of the injection could even be shortened with capable men, well designed
* equipment and a ready supply of water.









Table 1. Comparison between the time and men employed to
apply Fe-chelate to 7-year old avocados by drenching*
and by using the injection method.

Method No. trees No. men Hours Man-hours

Injection 500 2 12 24

Drenching 500 3 24 72


Dissolving chelates in either bucket or tanks, pouring
the solution around the tree and washing it down with
plenty of water.

Discussion.

Injection of Seq. 138 requires a great deal of precision which is especially important
in view of the cost of the material. If not enough chelate is applied, the response
may be inadequate and not sufficient to produce a satisfactory return. If too much
is applied, a considerable loss could result when a large number of trees are treated
since the trees do not respond to the extra chelate applied. Greater precision can
be attained when the injection pressure does not exceed 100 psi and when relatively
dilute solutions of chelate are applied. When high pressures and concentrations are
used, the injection time must be quite short and a small error in timing will result
in a larger error in the amount of chelate applied.

SGenerally speaking, however, the speed of operation and the number of trees treated
in a day represents the only area where costs can be lowered since chemicals, equip-
ment and labor costs are relatively fixed.


CONCLUSIONS AND RECOMMENDATIONS

1. Iron chelates, to be effective in calcareous soils must persist in a chemically
unchanged form for periods of time sufficiently long to be absorbed by the roots
of chlorotic trees. Of all chelates tested to date in the Homestead area,
"Sequestrene 138" is the only one that meets these requirements best.

2. For maximum absorption the chelate has to come in contact with a maximum number
of roots in the shortest time possible after its application. Since Seq. 138 is
degraded by sunlight, surface applications may not perform as well as expected.

3. Soil injections close to the tree trunk places the chelate underground quickly in
an area where roots are likely to be most abundant resulting in a quick response
and efficient utilization of the chelate.

4. Chelate injections are well suited for trenched groves where the majority of roots
are confined to the trench. The performance of the chemical can be maximized by
placing it in the midst of this concentrated root network.

5. October is the month best suited for an annual chelate application. This is the
time at the end of the rainy season when root development is at a maximum. There-
after the root population decreases slowly reaching its lowest concentration some-
time in May.









Table 1. Comparison between the time and men employed to
apply Fe-chelate to 7-year old avocados by drenching*
and by using the injection method.

Method No. trees No. men Hours Man-hours

Injection 500 2 12 24

Drenching 500 3 24 72


Dissolving chelates in either bucket or tanks, pouring
the solution around the tree and washing it down with
plenty of water.

Discussion.

Injection of Seq. 138 requires a great deal of precision which is especially important
in view of the cost of the material. If not enough chelate is applied, the response
may be inadequate and not sufficient to produce a satisfactory return. If too much
is applied, a considerable loss could result when a large number of trees are treated
since the trees do not respond to the extra chelate applied. Greater precision can
be attained when the injection pressure does not exceed 100 psi and when relatively
dilute solutions of chelate are applied. When high pressures and concentrations are
used, the injection time must be quite short and a small error in timing will result
in a larger error in the amount of chelate applied.

SGenerally speaking, however, the speed of operation and the number of trees treated
in a day represents the only area where costs can be lowered since chemicals, equip-
ment and labor costs are relatively fixed.


CONCLUSIONS AND RECOMMENDATIONS

1. Iron chelates, to be effective in calcareous soils must persist in a chemically
unchanged form for periods of time sufficiently long to be absorbed by the roots
of chlorotic trees. Of all chelates tested to date in the Homestead area,
"Sequestrene 138" is the only one that meets these requirements best.

2. For maximum absorption the chelate has to come in contact with a maximum number
of roots in the shortest time possible after its application. Since Seq. 138 is
degraded by sunlight, surface applications may not perform as well as expected.

3. Soil injections close to the tree trunk places the chelate underground quickly in
an area where roots are likely to be most abundant resulting in a quick response
and efficient utilization of the chelate.

4. Chelate injections are well suited for trenched groves where the majority of roots
are confined to the trench. The performance of the chemical can be maximized by
placing it in the midst of this concentrated root network.

5. October is the month best suited for an annual chelate application. This is the
time at the end of the rainy season when root development is at a maximum. There-
after the root population decreases slowly reaching its lowest concentration some-
time in May.




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