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Re:Cult: trace elements, boron

  • To: Multiple recipients of list <iris-l@rt66.com>
  • Subject: Re:Cult: trace elements, boron
  • From: Linda Mann <lmann@icx.net>
  • Date: Thu, 12 Feb 1998 12:47:38 -0700 (MST)

The Entomology and Plant Pathology Extension referred me to the
Ornamental Horticulture Extension who referred me to the Plant and Soil
Sciences Department of the University of Tennessee who referred me to a
very nice soil chemist who talke with me at length about trace elements
(micronutrients), especially boron.

Brady's Nature and Property of Soils is now in the teenage editions
(14th or more) but is still THE introductory soils text.  

Dr (Essington? - not sure I got his name) said that a lot has been done
on micronutrients since the 70s, but he couldn't refer me to a
particular general text that would tell me much.  Instead he recommended
searching homepages of University Agricultural Departments where he says
many professors now post extensive lecture notes.  He says these sites
are generally not linked to ?whatever it is that gets you there with a
search engine.

As Bill Shear said earlier, boron is rarely in low enough quantities to
be deficient, but it can often be unavailable to the plants, hence the
need for adding boron.  Naturally occurring levels range from around 2
to nearly 300 ppm, with a typical amount being around 20 ppm.  Dr. E.
says that as a general rule of thumb for crop production, they recommend
adding boron if the pH is higher than 6.  He says that when it is added
in an available form, it will stay that way for a while before being
tied up in the soil where the plants can't get it.  He emphasized the
narrow range between needed and toxic amounts.

Usual sources of boron in crop production are prepared fertilizers.  For
home gardens and ornamentals, Miracle Gro is a good source (but some of
us need to watch out for the lush injury prone foliage that results from
the nitrogen in Miracle Gro).  Borax can also be used, but then you have
to figure the dose and dissolve it in water to be able to spread it. 
For my corn patch, the application was something like 1-2 lbs of borax
per acre, which is a teensy amount in small garden.

Soils in Oregon tend to be high in allophane clay, natures best kind of
clay for growing plants.  It is highly buffered, which means it is
resistant to changes in pH - add lime and pH goes up but doesn't stay up
long, add acid and it goes down, but won't stay down.  Dr. E. says boron
is naturally high in those soils and can become a toxicity problem in
irrigated sites.  I forgot to ask what the pH is, but from the above
discussion, I assume it is naturally below 6, but I bet not a lot lower.

Dr. E. also emphasized that there are nutrient interactions, that
fiddling with availability of boron may throw something else out of
whack, and that all varies with pH.

And last, there is some evidence from crop research that fungicides are
more effective in controlling foliar diseases when the sticker (that's
the stuff you mix with the fungicide to make it stick to the leaves
better) contains boron.  Dr. E. wasn't up on the research, so couldn't
tell me more.

I'm going to go check my bag of 6-12-12 from the Co-Op and see if it
says it contains trace elements.  I know that some brands do and some

Linda Mann east Tennessee USA

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