AN-20, ammonium thiosulfate, and mixtures of these two materials can be
used as N sources, while also providing ancillary weed control in broccoli,
cabbage, and cauliflower. The amount of N per
gallon of material, the rate at which it is applied, and the phytotoxicity of
the material determines the crops on which these can be used.
All of these materials, when applied at the proper time and manner have
the added benefit of
ancillary control of many small (less than 3 inches) broadleaf weeds such as
groundsel, pineapple
weed, shepherdspurse, mallow, pigweed, hairy nightshade, chickweed, and many
others. Poor or
no control is obtained on lambsquarters, purslane, henbit, black nightshade,
knotweed, sowthistle, malva goosefoot and grasses.
When using these N sources in foliar applications, follow
cautions listed. Severe crop
injury may occur if cautions are not observed.
General cautions for the use of nitrogen liquid fertilizer formulations
are:
- Apply only after the crop has at least two true leaves. Application
at between the 3rd and 4th
true leaf stages is least likely to cause crop injury.
- Do not apply within 4 days of a period of cool, cloudy or rainy
weather, or if free water is
present on the leaves.
- Discontinue application if spray droplets do not roll off or
"bead-up"
on the leaves. This
indicates a deficiency of adequate waxy cuticle, and may be a temporary
condition due to rapid
growth, cloudy or rainy weather, or more seriously, the lack of adaptability
of the variety.
- Do not apply within 4 days after a foliar pesticide has been applied,
or with any wetting agent.
- Use large nozzles to minimize misting and possible injury to the crop
growing point.
- Direct the spray to the base of the crop with wide, low nozzles, or
use crop shields whenever
this can be done while still obtaining complete coverage of the
weeds.
AN-20 fertilizer formulation:
This is a manufactured 20-0-0 formulation (containing 20% N) that may be
applied at 50 to 70
gal product/acre as a foliar spray. This formulation weighs 10.55
lb/gal and
contains 2.11 lb N/gal of product and would provide approximately 100 to
140 lb N/acre
(but some N is lost through volatilization). Do not irrigate for 48 hours
after application, but
irrigate then to move the fertilizer into the root zone.
When this treatment is used as an N source and timed to provide ancillary weed control,
subsequent N sidedressings should be
reduced by a portion of
the amount of N applied in the treatment.
To prevent crop injury, follow the cautions listed above.
Note: This formulation is different from a solution that could be
prepared by dissolving
ammonium nitrate in water. Such a solution would not have the same
concentration or effect on weeds.
Note: Mixtures of AN-20 and ammonium thiosulfate (usually 1:1) can
be
made which will reduce
the amount of N applied, provide some sulfur (compared to application
of AN-20 only, and
reducing the sulfur if only ammonium thiosulfate were to be used), and be as
effective as either
material alone. Application rates are still held at 50 to 70 gallons of the
mixture per acre.
Ammonium thiosulfate:
This is a manufactured 12-0-0-26 formulation (containing 12% N and 26%
sulfur) and weighs
9.33 lb/gal. It may be applied at 50 to 70 gal of product per
acre as a foliar spray.
This solution contains 1.12 lb N and 2.4 lb S/gal of
product and would
provide approximately 55 to 75 lb N/acre (some N may be lost through
volatilization). At the
application gallonage mentioned, about 150 to 168 lb S/acre are also applied.
Do not irrigate for
48 hours after application, but irrigate then to move the fertilizer into the
root zone.
When this treatment is used, subsequent N sidedressings should be
reduced proportionately.
To prevent crop injury, follow the cautions listed above.
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