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Re: Fertilizer

Harold,

Do you know or does anyone in the group know why the addition of nitrogen,
be it feeding the plant via the ground or foliar feeding, brings on bug
problems.

I have noticed this the past couple of years and discussed it with other
local growers who have commented on the same problem.

It seems as soon as the plant has taken up nitrogen to a given level the
bugs are on your plant like white on rice!

Is there anyway are means to get around this problem and why do bugs pick
up on the nitrogen level in plants so quickly, it is almost as if it is a
pheromone?

Chris Andersen
Moraga, Calif.

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There are several different sources of N, P, and K used to make fertrilizer
formulations.  Generally for dry fertilizer materials, the P comes from
diammonium phosphate (DAP), and the K comes from potassium chloride (KCl). 
The N is supplied from the DAP as well.  Since DAP is 18-46-0 and KCl is
0-0-60 or 0-0-62, they are blended to make the formulation you want.  The
additional N may come from Urea (45-0-0) added to the mix, or ammonium
sulfate or some other N source.    For liquid fertilizers, other sources of
N, P or K may be used, depending on the solubility and on the desired use. 
 Urea-ammonium nitrate solution is often used as the N source and potassium
hydroxide (KOH) for the K source.  Phosphoric acid is the raw ingredient
for the P source.  It comes in different concentrations.  
For foliar applications, the materials used as N, P, K sources need to have
a low salt level to avoid injury to the leaves.  This usually means a
higher cost raw material.  But for small amounts used in gardens, this is
not a serious cost difference.  The garden and lawn fertilizers generally
have a lower analysis than fertilizers used for farm fields, so it takes
more material to get the same amount of nutrients.  This makes it easier to
get a uniform rate of application and reduces potential injury to the
plants.  These low analysis products are less practical for field
application because of the volume needed to provide adequate nutrients to
the crops.  Handling and transportation would be very expensive relative to
the more concentrated fertilizer materials.
If you would like more detail on this, feel free to send me an e-mail.
Harold Reetz
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