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i
FEB 7 -1962 |

7H eats ll
Deficiency
of Field and
Vegetable
Lrops in
the West

ne

U.S. DEPARTMENT OF AGRICULTURE LEAFLET No. 495

Zinc Deficiency of Field and
Vegetable Crops in the West

By FRANK G. Viets, Jr., Soil and Water Conservation Research Division,
Agricultural Research Service

All plants need zinc to develop and
fruit normally. The quantity of zinc
they demand is very small. A good
yield of a field or vegetable crop con-
tains from one-tenth to one-quarter
pound of zinc per acre. This means
that the zinc needs of such a crop
are met by a quantity amounting to
only one-hundredth of the same crop’s
requirement of phosphorus (as P20;)
and only one-thousandth of its require-
ment of nitrogen. Even so, too little
zinc is available in some agricultural
soils.

Zinc deficiency was identified in the
midthirties as causing failure of fruit
and nut trees to grow and produce
normally in many irrigated areas of
the West. More recently, it has been
recognized on field and vegetable crops
in both irrigated and dryland areas

of the West.
The Sensitive Crops

Some crop plants show striking
symptoms of zinc deficiency on land
where other crop plants show none.
The crops most frequently stunted and
reduced in yield by shortage of avail-
able zinc are corn, beans, castorbeans,
sorghums, cotton, onions, tomatoes,
hops, potatoes, and flax. Crops that
rarely show any symptoms of such
shortage are small grains, alfalfa,
clovers, mint, and grasses. Sugar beets
and some other crops are highly sensi-
tive to zinc deficiency in some areas
but only moderately sensitive elsewhere.

Crops sensitive to zinc deficiency
often show more acute symptoms of it
when grown after sugar beets than they
do when preceded by another crop.
Cold, wet spring weather frequently
intensifies their reaction.

The Deficient Soils

Zinc deficiency is more common
where surface soil has been partly or
entirely removed by erosion or by
leveling of land for irrigation. How-
ever, leveling does not always cause
zinc deficiency, and undisturbed soils
can be deficient in zinc. The deficiency
is frequent on old corral sites. Corn
has shown it on nonirrigated land in
eastern South Dakota and Nebraska,
but has not been reported to do so in
other nonirrigated areas of the West.

Zinc deficiency can occur in soils of
all textures, from sand to clay. In
Nebraska, it is more frequent in sandy
soils. The deficient soils are more likely
to be alkaline (that is, to have a pH
of at least 7) than to be acid, and are
likely to contain lime.

A soil can contain a normal quantity
of zinc and still be deficient in zinc
available to plants.

The deficiency may occur in spots
in a field or throughout a field.

Symptoms

In general, the stems and leaves of
zine-deficient plants fail to develop to
normal size, and some of the tissues

SN-339
Lima bean (Fordhook) leaves affected by zinc deficiency, in contrast with one
that is normal. The deficiency has caused yellowing between veins, rusty-brown
blotches, and, in the trifoliolate leaves, some stunting and a leathery texture.

SN-340
Zinc deficiency has stunted and yellowed the three soybean leaves at the left. At
the right, a normal soybean leaf in the same stage of growth.

3

SN-341

Zinc-deficiency symptoms on Red Mexican (U.I. 34) field beans. The yellowing and
deformity shown by the three old leaves at the left appear in milder form in the
younger leaf at the center. At-the right, a normal leaf. (Iron deficiency, also,

produces yellowing between the veins of Red Mexican field bean leaves, but it
affects the new leaves worse than the old and does not deform the leaves.)

SN-342

Sidearms of this hop branch show effects of zinc deficiency in their greatly
shortened internodes and greatly reduced leaf size. The yellowing between veins
of leaves on the branch is another effect of this deficiency.

4

between the leaf veins contain so little
chlorophyll that they turn yellow. This
yellowing, technically called chlorosis,
is usually worst on the lowest leaves
of the plant. The yellowed leaf tissues
may turn brown or gray and die pre-
maturely. A zinc-deficient area in a
bean field will have a yellowish-brown
color when viewed from a distance.

Varieties of some crop plants differ
in their ways of reacting to zinc short-
age. For example, Russet Burbank,
alone among all potato varieties grown
commercially in the West, shows a
conspicuous stunting of leaves of the
terminal growth and does not, like
other potatoes, show yellowing of leaf
tissues and stunting of lower leaves.
Varieties of field beans differ consider-
ably in their reactions.

Symptoms are often more common
and more severe at earlier than at later
stages of growth. A moderate zinc

deficiency, even though it delays matur-
ing of corn or bean plants and limits
their yields, may cause no symptoms
on new growth of the plants as the
root systems develop.

Symptoms of zinc deficiency re-
semble those of iron, manganese, or
magnesium deficiency. This deficiency
can occur together with any one or
two of the others named, or with all
of them.

Diagnosis

Make sure you diagnose any plant
abnormality correctly before you
attempt to control it. The symptoms
pictured in this leaflet are a good guide
to diagnosing zinc deficiency, but they
are not entirely reliable. Laboratory
tests for determining zinc content of
soil are not yet suitable for routine
use, and no quick tissue tests can be
recommended yet for field use.

BN-11895

“Fern leaf,” the foliage abnormality illustrated at the right, results from zinc
deficiency in just one of the potato varieties grown commercially in the West—
Russet Burbank. At the left, normal foliage of Russet Burbank. (In other western
potato varieties, the symptoms of zinc deficiency are yellowing between veins of
older leaves and stunting of leaves.)

BN-11891
The two castorbean leaves at the left were stunted by zinc deficiency. At right,
a normal leaf of the same age.

a LOTT AN

Onions grown on soil that does not provide them with enough zine are severely
stunted and have yellow, crooked tops. At left, normal onions of the same variety
and age.

BN-11892

6

If you suspect zinc deficiency, the
best way to confirm it is to apply a
zinc treatment. For a spray test, dis-
solve a teaspoonful of zinc sulfate in
a gallon of water and wet the foliage
of several dozen of the abnormal plants
with the solution. If zinc—and zinc
alone—has been deficient, the treated
plants should resume normal growth,
and new leaves and stems should show
no signs of deficiency.

Spraying is not an effective test
method for onions or Russet Burbank

potatoes. Where symptoms of zinc
deficiency have appeared on either of
these crops or have appeared in only
mild form on some other crop, zinc
treatment for testing purposes may be
applied to the soil before the next
spring planting. Mix zinc sulfate in
the soil at the rate of 2 ounces for
each 100 square feet, or apply it at
the same rate as a sidedressing at a
depth of about 3 inches, 3 inches to
the side of the row.

so as

BN-11893

Corn stunted and discolored by zinc deficiency. The earliest symptom on corn is
broad bands of light-colored stripes on the lower leaves. Margins, midribs, and
tips of the affected leaves stay green. These leaves die prematurely. (Iron defi-
ciency, also, produces striping on corn leaves, but it affects the upper leaves more

severely than the lower.)

How To Correct It

In an emergency, a foliage spray
containing zinc is the best means of
correcting zinc deficiency in plants
other than onions or Russet Burbank
potatoes. To make an effective spray,
dissolve 1 pound of zinc sulfate and
a cupful of household detergent in 50
gallons of water. Apply the solution
when the plants are small, using low-
pressure ground spraying equipment.
Wet the foliage thoroughly. One or
more repeat applications may be neces-
sary.

Applying zinc to the soil generally
gives better results than spraying it
on the foliage, and zinc thus applied
is available to plants for 4 or 5 years—
perhaps longer. Any zinc compound
that will dissolve in dilute hydrochloric
acid is satisfactory as a fertilizer
material to be applied to the soil. Such
compounds include zinc sulfate, zinc
oxide, zinc carbonate, and zinc am-
monium sulfite.

(The merits of chelated zinc —
organic compounds of zinc—as foliage
sprays or soil treatments for field or
vegetable crops have not offset the
higher cost.)

Zinc is held firmly in the soil. It
cannot be leached out by rain or by
irrigation water. Likewise, it cannot
be carried by soil water to the roots
of plants. Roots must grow to the zinc.
So zinc fertilizer. to serve its purpose,
must be mixed into the soil where
developing roots can come into contact
with it.

For nonsandy soil on which an
annual crop is to be seeded, the
recommended method of correcting
zinc deficiency is to incorporate 10
pounds of zinc per acre into the soil
by plowing it under, or drill it in a
band 2 inches below the seeding depth,
2 inches to the side of each seed row.
On sands, apply 3 to 5 pounds of zinc

Washington, D. C.

per acre in the same way. In fields
of perennial crops, such as hops, broad-
cast 20 to 30 pounds of zinc per acre
and mix it into the soil, or drill it in
a band at a depth of 10 inches, 1 foot
to each side of each row of plants.

Any of the zinc compounds recom-
mended for use as soil treatments can
be applied alone or used in a mixed
or liquid fertilizer. Zinc is more effec-
tive if banded with nitrogen fertilizer
than if banded alone. The zinc content
of a commercial mixed fertilizer is
printed on the bag. The availability
of zine used in a fertilizer mixture is
not reduced by phosphate. If you mix
zinc sulfate with dry nitrogen fertilizer,
spread the mixture immediately to
avoid caking.

Zinc applied to soil or as a foliage
spray at the rates recommended. here
will not injure crop plants.

How To Prevent It

Since the surface layer of a soil
usually contains most of the available
zinc, anything that guards the soil
against abnormal erosion helps to pre-
vent zinc deficiency. In addition, the
following practices help maintain an
adequate supply of available zinc in
the soil:

e In using phosphates as fertilizers,
take care not to apply them at rates
higher than those recommended. For
reasons not yet well established, too
heavy use of phosphates can cause zinc
deficiency in some soils.

e Encourage development of extensive
root systems by crop plants. Since
zinc cannot move in the soil, its avail-
ability to plants depends largely on
movement of plant roots to it. Exten-
sive root development is favored by
tillage practices that prevent compact-
ing of soil; by methods of water man-
agement that prevent waterlogging of
soil; and by crop rotations such as
those including clover or alfalfa.

Issued November, 1961

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