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  • From: Chris Reid <chriscreid AT yahoo.com>
  • To: market-farming AT lists.ibiblio.org
  • Subject: Re: [Market-farming] kaolin clay
  • Date: Thu, 14 Jan 2010 14:31:50 -0800 (PST)

Ben mentioned in his post about dipping plants in kaolin clay (presumably Surround) that Surround was all he found under the search term kaolin clay.
 
Surround of course is not cheap.  Since it may be tempting to look for kaolin clay in a cheaper format, just thought I would mention that in  Michael Phillips' book, The Apple Grower: A Guide for the Organic Orchardist, there is a pretty an extensive discussion about how to use kaolin clay in orchards, and he explicitly warns against using something other than Surround. 
 
I'm going to quote him here since I haven't had the experience myself, in case it is useful to somebody.  He says, " You might think it possible to save some money by purchasing pottery-grade kaolin instead of paying more than a dollar apound for the spray material labeled as Surround. Not so. The kaolin in Surround has been highly processed to achieve an extremely fine particle size that is absolutely relevant to its effectiveness.  The mined clay is pulverized, then put through a giant centrifuge, where an electromagnet pulls off iron, manganese, and other paramagnetic stains.  A whiter, more reflective material is the result."
 
Someone here on the market farming list commented on kaolin and its impact on photosynthesis -- and  to understand the effect, here again, whether one is using kaolin or specifically  Surround apparenly is an important distinction.  Continuing quoting Phillips," Bulk kaolin particles are large and flaky, completely coating the leaf and thus causing a drastic decrease in photosynthesis. ...Smaller Surround particles, on the other hand, allow leaf stomata to emerge through the clay coverage. 
 
[NOTE:  So, that seems to answer, at least for apples, another of Ben's questions about plugging the stomata.] Phillips says that photosynthesis is enhanced.
 
A few years back I read that in an Italian research project, lemon trees actually were less stressed when canopies  were coated with kaolin (not sure if Surround or not) --- in extreme heat, the canopy temperature was lower and plant processes were able to continue, whereas normally in intense heat, they shut down.
 
Moving this into the realm of documented/observed phenomena, in research Phillips mentions, apparently infrared photography was used to record and document the temperature difference between kaolin versus nonkaolin coated canopies. Kaolin WAS cooler.
 
If spraying the kaolin onto the plant, Phillips goes on to discuss the type of nozzle used, pressure used, and thickness of layer of Surround.  Apparently all affect whether one gets e.g.  a thick layer that falls off the underside of the leaf  (happed to some trees I take care of once) or a series of thinner layers that can be built up into a protective coat.  If dipping plants, then, it would seem that viscosity of the dip, number of dips, and dry time between dips all could have an impact on effectiveness of the method. 
 
OK folks, end of quoting what MAY BE relevant to vegetable growers. (PS:  If you grow apples, I do recommend the book.  I find it's written from a very hands-on perspective.)
 
Best regards,
 
Chris Reid
Stamford, CT




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