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  • From: bob111higgins AT comcast.net
  • To: Market Farming <market-farming AT lists.ibiblio.org>
  • Cc: , market-farming AT lists.ibiblio.org, Barry Jackson <barry.jackson AT which.net>
  • Subject: Re: [Market-farming] RE: Market-farming ,Root Nematodes
  • Date: Sat, 17 Apr 2004 04:16:34 +0000

Barry,

Thanks for your information about deformed potatoes. (About 1/3 of my crop,
but mostly the longer season Kennebec and Green Mountain varieties; longer
growing season = more time for things to go wrong?)

I have also just come across a couple of pieces that talk about the stopping
and re-starting of growth as an explanation for this deformation, though my
sources talked about inconsistencies in watering and not about temperature.
Your idea about weeds adding to water stress is a good one, also. I had my
plants in an open field, no canopy, and no raised bed, but fairly shallow
trench, so temperature could have risen too high also in the summer heat. I
had to plant really late because of the hard spring rains. And I also suspect
some of the pest damage suggested by Bob Schuler. Though this is a long list
of conditions to control for, at least I have a better idea of what to do now.

Thanks!

Bob Higgins
Red Brick Farm
Hopewell Township, NJ
>
>
> > -----Original Message-----
> > From: market-farming-bounces AT lists.ibiblio.org
> > [mailto:market-farming-bounces AT lists.ibiblio.org]On Behalf Of
> > market-farming-request AT lists.ibiblio.org
> > Sent: Wednesday, April 14, 2004 2:58 PM
> > To: market-farming AT lists.ibiblio.org
> > Subject: Market-farming Digest,Root Nematodes
> >
> >
> > Send Market-farming mailing list submissions to
> > market-farming AT lists.ibiblio.org
>
> Hi,
> Bob Higgins wrote
> > "Last year, a large percentage of my potatoes came out gnarly and
> > deformed. This was in my new garden, first market garden, new
> > place we moved to. First I thought the potatoes looked like that
> > because I let the weeding go and they had to compete with lots of
> > strongly-rooted weeds -- maybe the weed roots wrapped around the taters.
>
> It struck me that this was very similar to my own problems last year where I
> was growing PCN susceptible potatoes (King Edwards) in 100% home made
> compost in raised beds 1ft deep to avoid the debilitating effects of our

> endemic eelworm. [This incidentally was on the west coast of the UK, much
> closer to Jersey than New Jersey]
>
> In trying to find out how/why my lumpy potatoes had become so deformed I
> unearthed the two leads below. I suspect if you do a Google search on
> "stressed potatoes" you will find many more.
> We had a fairly warm summer here but crucially in my deep raised beds the
> soil temperature would have been rather higher than was experienced in the
> normal soil plus the irregularity of my watering regime no doubt added an
> additional stress.
> I feel sure the tuberisation of my potatoes was halted by heat or moisture
> stress and, when cooler conditions came along, they simply started growing
> secondary potatoes from dormant eye sites of the original tubers.
> Perhaps in your case the vigorous weeds might have created a condition of
> moisture stress.
> Did you have a closed canopy?
>
> Best of luck for this year.
> Barry Jackson, Parkgate, Wirral UK.
>
> http://www.uga.edu/vegetable/potato.html

> This is a lengthy paper & I have paraphrased below what I think is the
> relevant bit.
> "The optimal temperature for tuberization is 55?F, the process actually
> decreases above 70?F and for certain cultivars, may stop altogether at 85?F.
> Higher temperatures may often induce knobbliness and secondary growth in the
> tubers. Maximum yields are usually obtained when the average growing
> temperature is kept between 60? and 65?F
>
> Irrigation before tuber initiation can adversely affect both the yield and
> the marketability. A consistent soil moisture of 60-70% of field capacity is
> crucial particularly during tuber development. Fluctuation in soil moisture
> content may well give rise to abnormalities in tuber formation."
>
> AND from
> http://www.plantpath.wisc.edu/wivegdis/2002%20veg%20dis%20updates/Potato%20C
> rop%20Update%20Number%205%2007-03-02.htm
>
> Potatoes are heat sensitive and Russet Burbank is one of the most heat
> sensitive varieties grown in the United States. Photosynthetic efficiency or

> net photosynthesis in potatoes rapidly declines as temperatures increase
> above 85? F. As a result the plant has less carbohydrate from photosynthesis
> to support growth and more importantly tuber development. When heat stress
> becomes severe or prolonged over extended periods of time, tubers will stop
> bulking altogether and may start to lose mass as starch is degraded to
> provide energy to maintain the stressed plant. Unfortunately, when
> conditions become favourable for active tuber growth again, potatoes do not
> simply start bulking the same tubers. Rather, potatoes will go through
> secondary set or initiate tuber growth at one location on the tuber. The end
> result is smaller potatoes or malformed tubers with irregular growth.
> Little can be done to manage heat stress in potatoes. Closed canopies are
> absolutely essential for managing the temperature of the hill.
>
>
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