Note: Descriptions are shown in the official language in which they were submitted.
104S843
BAC~GROUND OF THE INVENTION
This invention relates to the foliar application
of zinc compounds in aqueous solution. More
particularly, the invention relates to an improved
foliar spray composition comprising a synergistic
combination of zinc nitrate, ammonium nitrate and urea
in aqueous solution.
The use of micronutrients as fertilizers is
experiencin~ increased use. The elements such as
~o zinc, manganese, boron, copper, molybdenum and iron
are fully as important as the primary nutrients,
nitrogen, phosphorus, and potassium, although the
former are used in much smaller quantities. Agronomic
tests in a large number of states have been concerned
with establishing where the need for micronutrients
exists, comparing sources and carriers and indicating
amounts that may be needed.
; It is now-known that plants growing on soils
having pH values over 7.0 usually suffer from lack of
zinc availability in the soil due to the presence of
various calcium compounds. Therefore, zinc is
usually supplied to the plants by foliar means.
Unfortunately, foliar application of zinc compositions
in accordance with prior procedures is not completely
satisfactory because of relatively low absorption
o~ the micronutrient by the leaves of the plant.
The best zinc composition previously found has been
zinc sulfate combined with a fertilizer solution
composed of ammonium nitrate and urea (The Pecan !-~
Quarterly, Vol. 7; No. 2, May 1973).
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1045843
SUMMARY OF THE INV~NTION
_ . _ _ . . . . _ .
The present invention provides a new zinc-
containing foliar spray composition and method of
using the same for increasing zinc absorption by leaves.
The instant foliar spray composition consists
essentially of about 0.5 to 4 parts by weight,
preferably 0.9 to 1.8 parts by weight, of zinc
nitrate; 2 to 5 parts by weight, preferably 4 to 5
parts by weight, of an aqueous fertilizer solution
comprising ammonium nitrate and urea, said fertilizer
solution containing at least 20 percent by weight
of urea and at least 20 percent by weight of ammonium
nitrate; and up to about 1,000 parts by weight of water.
It will be understood that the urea and ammonium
nitrate may be incorporated into the foliar spray
composition as solids, if desired. However, it is
convenient to add the ammonium nitrate and urea as
; a fertilizer solution because such solutions are
readily available. Preferred solutions are those
. .
normally used as soil fertilizers or in the production
of fertilizers, i.e., those solutions of pH 6-7
containing on a weight basis at least about 30 percent
each of ammonium nitrate and urea, at least about
15 percent of water, and up to 1 percent of free
ammonia. A commercial solu~ion made by Allied Chemical
Corporation is sold under the trademark URAN; a typical
solution contains about 45.1 percent ammonium
nitrate, 34.8 percent urea and 20.1 percent water.
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1045843
DESCRIPl'TON OF T~IE P~EFERRED EMBODIMENTS
The present invention is based on the discovery
of a synergistic effect in the absorp'iGn of zinc
ions by plant leaves, said synergism r~sulting from
the combination of certain critical proportions of
zinc nitrate, ammonium nitrate and urea in a relatively
dilute foliar spray. Preferably, the foliar spray
composition consists essentially of 0.9 to 1.~ parts
by weight of zinc nitrate; 2 to 5 parts by weight
of an aqueous fertilizer solution comprising ammonium
nitrate and urea, said fertilizer solution containing
at least about 30 percent by weight of urea, at least
about 30 percent by weight of ammonium nitrate, at
least about 15 percent of water, and up to 1 percent
of free ammonia; and about 1,000 parts by weight of
water.
In order to demonstrate the invention, the
following examples are given.
EXAMPLE l
Pecan trees suffering from severe zinc deficiency
are characterized by rosette and die-back. More
subtle symptoms, however, such as smaller than
average leaves, reduced yields and pronounced alternate
beaxing are more commonly experienced.
Zinc is not available to pecan roots in soil
high in calcium carbonate in quantities sufficlent
to insure normal pecan tree growth development.
Even though zinc may be abundant in calcareous
soils, trees may suffer;from lack of zinc because ~-
it is in the form of insoluble compounds such
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1045843
- as zinc carbonate. Therefore, zinc is usually
supplied by foliar means. Best application times
seem to be as buds are breaking, one week later,
two weeks later, and then at about three week
intervals until shoot elongation has ceased. The
best foliar spray previously found has been zinc sulfate
in the presence of an aqueous ammonium nitrate-
urea solution. This example shows that about twice
as much zinc is absorbed by leaves from an equivalent
amount of zinc in the form of zinc nitrate rather
~ than zinc sulfate of said prior procedure.
; The following table shows the zinc content of
pecan leaves from trees foliarly treated with various
rates of zinc sulfate or zinc nitrate plus a
concentrated fertilizer solution containlng 32 weight
percent total nitrogen composed of half ammonium
nitrate and half urea. Tests were carried out in
Texas in a pecan orchard in Brazos River flood plain.
TABLE I
Treatment
Pounds Material Per 1,000 Pounds of Water
Mean* Zinc
Zinc Zinc Urea-Ammonium Content of -
Sulfate Nitrate Nitrate Solution Leaf, (PPM)
28 a
2.4 0 0 454 d
2.4 0 5 734 e
0 1.8 0 275 bd
0 1.8 5 976 fg
0 3.6 0 976 fg
0 3.6 5 1062 g
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*Means followed by different letters are significantly
different 95 percent of the time.
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1 ~45843
Those skilled in the art will note that the
foliar spray composition containing zinc nitrate,
ammonium nitrate and urea gave significantly better
results at the 95% confidence level than the foliar
spray composition containing zinc sulfate, ammonium
nitrate and urea. Also, because of the relatively
high cost of zinc compounds, it will be clear to those
skilled in the art that the foliar spray composition
containing about 0.18% zinc nitrate plus ammonium
nitrate and urea is preferred over the compositions
containing 0.36% zinc.nitrate, although zinc absorption
was not significantly different.
~ rom these and other tests it was determined
that about 1.25 acres may be sprayed with about 500
gallons (about 4,200 pounds) of the preferred dilute
foliar spray with effective results.
EXAMPLE 2 .:
.The procedure of Example 1 was repeated except
that no zinc sulfate was used and the amounts of
zinc nitrate used was varied to determine the most
economical, effective treatments. Table II shows
results.
It should be noted that Example 1 tests were
conducted in 1972, whereas Example 2 tests were
conducted in 1973.
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~045~43
TAsLE II
Treatment
Pounds Material per 1,000 Pounds of Water
Mean* Zinc
Zinc Urea-Ammonium Content of
Nitrate Nitrate Solution Leaf,(PPM)
0 23 a
3.6 0 170 ef
3.6 5 271 g
1.8 0 68 cd
1.8 5 151 e **
, 0 9 0 37 ab
o.9 5 70 d **
0.45 0 38 ab
0.45 5 57 bd
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*Means followed by different letters are significantly
' different 95 percent of the time.
**Most economical, effective treatments.
In other tests, it was determined that the maximum
desirable concentration of the urea-ammonium nitrate
- solution in the foliar spray was about 5 pounds per
acre per application. Higher concentrations may
cause burning of the foliage, particularly in dry
climates. Also, attempts to eliminate urea or
ammonium nitrate from the formulation have led to
relatively poor results.
Also, the concentration of zinc nitrate is
preferably limited to less than 2 pounds per acre per
application. This applies to all regions, no ~ -
matter how many pounds of zinc have been used
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104S843
in the past. The present invention significantly
increases the zinc absorption, and as more zinc goes
in, the high rates of zinc application used in the
past can burn leaves.
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