Anderson, Warren B.

Gray, Carl

Thomas, Grant W.

Valentine, James A.

Welch, C. D.

Texas A&amp;M Repository

L-723Identifying and Correcting Iron DeficiencyIn Field CropsC. D. Welch, Carl Gray, James A. Valentine, Warren B. Anderson and Grant W. Thomas*Table 1. Deficiency symptoms on major field cropsAn inadequate supply of available~iron causesplants to turn yellow from a lack of chlorophyll intheir leaves. Although iron is not part of thechlorophyll molecule, it is required for chlorophyllformation. Iron deficiency symptoms generallyappear on younger -leaves. Although the symp-toms may vary in severity, Table 1 will serve asa guide for the identification of this problem.Re pectivel.'. E. -len ion oil chemists; area Extension soilchelni t; and assistant professor and professor, Departtnentof Soil and Crop Sciences, Texas A&M University.One of the simplest methods for confirmingiron deficiency is to apply a 1 to 2Y2 percent solu-tion of iron sulfate (copperas) on some chloroticCropGrainsorghum,corn,foragesorghumsandJohnson-grassOats(smallgrains)SoybeansCottonRiceDeficiency symptomsAppears on top leaves. Starts as yel-low stripes between veins and ex-tends to leaf tips. Young plants mayturn pale yellow o:1d under extremedeficiency may develop to bleachedwhite. Often appears only in spotsin fields. Plants tend to recover frommoderate deficiency.Leaf blades develop yellow stripesbetween green veins and continue toturn more yellow over the entire leafblade.Development of yellow tissue betweenveins of young leaves. Under severedeficiency, leaves become pale yellowto white.Pale green or yellow between veinsgiving a netted appearance and re-duced new growth.Yellow between leaf veins. Entire leafblade turns pale yellow.leaves. This solution may be prepared by dis-solving 1 tablespoonful of iron sulfate and Y2 tea-spoonful of detergent in 1 gallon of water. Applythe solution by spraying, dipping individual leavesin the solution or painting a portion of the chlo-rotic leaf. Green color should be more noticeablein 4 to 7 days, under favorable growing conditions,if the chlorosis is caused by iron deficiency. Youngor recently matured leaves should be used for thistest since old, severely chlorotic leaves tend to lackthe ability to form chlorophyll, even when suppliedwith iron.Iron Deficient RegionsIron deficiency has been reported in most re-gions of Texas. The extent of this problem isshown in Figure 1 and generally corresponds tothe distribution of alkaline soils. Iron deficiency~ Severe• ModerateIII SlightOVeryslightFigure 1. Degree of iron deficiency in land resourceareas.12.3Texas A&M University • Agricultural Extension Service • John E. Hutchison, Dir ctor • College Stationseldom is observed on crops growing in acid soils.Most soils contain considerable quantities of iron,but the availability is influenced by factors suchas pH and calcium level.Correcting Iron DeficiencyAttempts to correct iron deficiency by applyingacidifying materials to calcareous soils generallyhave not been successful or practical on a fieldbasis, because of the large amount of acidifyingmaterial required. For example, it would take 5tons of sulfuric acid per acre to neutralize 1 per-cent calcium carbonate in a 6Y2-inch layer of soil.Many iron-deficient soils contain as much as 10percent free calcium carbonate, which represents50 tons of sulfuric acid. If elemental sulfur wereused, it would require one-third that amount togive the equivalent acidifying effect. Products ofacidifying reactions may increase greatly the soilsalinity. Localized acidification through bandingor using pelleted sulfur has been successful in somesituations.Applying iron as a foliar spray is the most fav-orable method for correcting iron deficiency, eventhough repeat applications may be needed. Thelow cost of this method is one factor. Iron spraysare most effective when applied on young plants.Table 2. Sources and rates of ironType iron Amount per 50 Rate of solutioncompound gallons water per acrelIron sulfate(copperas) 10 lb. (2 1/ 2 %) 15 to 30Chelate 4 lb. (1%) 15 to 30lWet plants thoroughly.Up to three applications may be required at 10-day to 2-week intervals. Table 2 provides a gen-eral guide for treating iron deficient plants.Soil applications of iron compounds, eitheriron sulfate, chelates or similar formulations gen-erally have not given satisfactory results. If soilconditions are such that iron is in an unavailableform, added iron also appears to quickly becomeunavailable.Applications of 500 to 1,000 pounds per acreof ferric sulfate (not copperas) mixed in the soilhave improved production of rice in iron-deficientsoils.SummaryTo evaluate and correct deficiencies that ap-pear to be caused by iron, follow this guide:1. Identify the problem through deficiencysymptoms and treat chlorotic leaves with an ironsolution. Plant analyses are helpfUl sometimes,but are quite variable and difficult to interpret.2. If the problem justifies treatment, use foliarsprays containing 2Y2 percent iron sulfate or 1percent chelate.3. For soils showing extreme and chronic irondeficiency, it may be desirable to grow crops thathave a low susceptibility, or plan to spray affectedcrops as a regular practice.4. If a mixture of iron sulfate and zinc sulfateis used as a foliar spray, use a concentration of 1Y2percent iron sulfate and !4 percent zinc sulfate.5. If concentrated solutions of iron compoundsare used, be sure that they are diluted properly tothe desired concentration for the final solution.Cooperative Extension Work in Agriculture and Home Economics, Texas A&M University and the L"nited States Department ofAgriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, 1914, as amended, and June 30, 1914.5M-Il-67

Identifying and Correcting Iron Deficiency in Field Crops.

Texas A&M University

L-723
Identifying and Correcting Iron Deficiency
In Field Crops
C. D. Welch, Carl Gray, James A. Valentine, Warren B. Anderson and Grant W. Thomas*
Table 1. Deficiency symptoms on major field crops
An inadequate supply of available~iron causes
plants to turn yellow from a lack of chlorophyll in
their leaves. Although iron is not part of the
chlorophyll molecule, it is required for chlorophyll
formation. Iron deficiency symptoms generally
appear on younger -leaves. Although the symp-
toms may vary in severity, Table 1 will serve as
a guide for the identification of this problem.
Re pectivel.'. E. -len ion oil chemists; area Extension soil
chelni t; and assistant professor and professor, Departtnent
of Soil and Crop Sciences, Texas A&M University.
One of the simplest methods for confirming
iron deficiency is to apply a 1 to 2Y2 percent solu-
tion of iron sulfate (copperas) on some chlorotic
Crop
Grain
sorghum,
corn,
forage
sorghums
and
Johnson-
grass
Oats
(small
grains)
Soybeans
Cotton
Rice
Deficiency symptoms
Appears on top leaves. Starts as yel-
low stripes between veins and ex-
tends to leaf tips. Young plants may
turn pale yellow o:1d under extreme
deficiency may develop to bleached
white. Often appears only in spots
in fields. Plants tend to recover from
moderate deficiency.
Leaf blades develop yellow stripes
between green veins and continue to
turn more yellow over the entire leaf
blade.
Development of yellow tissue between
veins of young leaves. Under severe
deficiency, leaves become pale yellow
to white.
Pale green or yellow between veins
giving a netted appearance and re-
duced new growth.
Yellow between leaf veins. Entire leaf
blade turns pale yellow.
leaves. This solution may be prepared by dis-
solving 1 tablespoonful of iron sulfate and Y2 tea-
spoonful of detergent in 1 gallon of water. Apply
the solution by spraying, dipping individual leaves
in the solution or painting a portion of the chlo-
rotic leaf. Green color should be more noticeable
in 4 to 7 days, under favorable growing conditions,
if the chlorosis is caused by iron deficiency. Young
or recently matured leaves should be used for this
test since old, severely chlorotic leaves tend to lack
the ability to form chlorophyll, even when supplied
with iron.
Iron Deficient Regions
Iron deficiency has been reported in most re-
gions of Texas. The extent of this problem is
shown in Figure 1 and generally corresponds to
the distribution of alkaline soils. Iron deficiency
~ Severe
• Moderate
III Slight
OVery
slight
Figure 1. Degree of iron deficiency in land resource
areas.
12.3
Texas A&M University • Agricultural Extension Service • John E. Hutchison, Dir ctor • College Station
seldom is observed on crops growing in acid soils.
Most soils contain considerable quantities of iron,
but the availability is influenced by factors such
as pH and calcium level.
Correcting Iron Deficiency
Attempts to correct iron deficiency by applying
acidifying materials to calcareous soils generally
have not been successful or practical on a field
basis, because of the large amount of acidifying
material required. For example, it would take 5
tons of sulfuric acid per acre to neutralize 1 per-
cent calcium carbonate in a 6Y2-inch layer of soil.
Many iron-deficient soils contain as much as 10
percent free calcium carbonate, which represents
50 tons of sulfuric acid. If elemental sulfur were
used, it would require one-third that amount to
give the equivalent acidifying effect. Products of
acidifying reactions may increase greatly the soil
salinity. Localized acidification through banding
or using pelleted sulfur has been successful in some
situations.
Applying iron as a foliar spray is the most fav-
orable method for correcting iron deficiency, even
though repeat applications may be needed. The
low cost of this method is one factor. Iron sprays
are most effective when applied on young plants.
Table 2. Sources and rates of iron
Type iron Amount per 50 Rate of solution
compound gallons water per acrel
Iron sulfate
(copperas) 10 lb. (2 1/ 2 %) 15 to 30
Chelate 4 lb. (1%) 15 to 30
lWet plants thoroughly.
Up to three applications may be required at 10-
day to 2-week intervals. Table 2 provides a gen-
eral guide for treating iron deficient plants.
Soil applications of iron compounds, either
iron sulfate, chelates or similar formulations gen-
erally have not given satisfactory results. If soil
conditions are such that iron is in an unavailable
form, added iron also appears to quickly become
unavailable.
Applications of 500 to 1,000 pounds per acre
of ferric sulfate (not copperas) mixed in the soil
have improved production of rice in iron-deficient
soils.
Summary
To evaluate and correct deficiencies that ap-
pear to be caused by iron, follow this guide:
1. Identify the problem through deficiency
symptoms and treat chlorotic leaves with an iron
solution. Plant analyses are helpfUl sometimes,
but are quite variable and difficult to interpret.
2. If the problem justifies treatment, use foliar
sprays containing 2Y2 percent iron sulfate or 1
percent chelate.
3. For soils showing extreme and chronic iron
deficiency, it may be desirable to grow crops that
have a low susceptibility, or plan to spray affected
crops as a regular practice.
4. If a mixture of iron sulfate and zinc sulfate
is used as a foliar spray, use a concentration of 1Y2
percent iron sulfate and !4 percent zinc sulfate.
5. If concentrated solutions of iron compounds
are used, be sure that they are diluted properly to
the desired concentration for the final solution.
Cooperative Extension Work in Agriculture and Home Economics, Texas A&M University and the L"nited States Department of
Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, 1914, as amended, and June 30, 1914.
5M-Il-67


English

https://oaktrust.library.tamu.edu/bitstream/1969.1/164722/2/723/Leaf0723.pdf

Identifying and Correcting Iron Deficiency in Field Crops.

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Identifying and Correcting Iron Deficiency in Field Crops.

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Texas A&amp;M Repository

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