Summary of Soil Problems/So

Thu Jun 3 15:09:56 EST 1993

 The Boyce Thompson Institute
 Subject Summary of Soil Problems/Solutions               6/3/93     2:08 PM
Thanks to everyone who replied to my posting of yesterday.  Bad soil seems to
be a problem that strikes fear in the hearts of all plant biologists, and
understandably so.  In summary of some of the reccurent themes:
Fungus gnats might be the problem.
Plants might be able to sense the season, even when grown under 'constant'
conditions in rooms or chambers.  It is striking that Alan Slusarenko (in
Europe) experienced the same trouble at the same time as did my group in
Alternatively, the soil properties might change with the season.
If the soil is not working, go to the garden or farm store and buy a half dozen
other mixes and see which one does work.  (This is not an elegant solution, but
it might save some sweat and time)
When a new batch of soil arrives, test the lot to make certain that the plants
grow OK.

The edited responses follow:

Dear Rob, whatever it is we've got it too.  It started last year in early
summer and its back this year.  We've used different growing medium
preparations and
 it didn't make any difference - so if it is something in their preparation tha
ts season dependent it must affect many different types in europe and the US.
We don't see anthocyanosis and its mainly our Wei-0 and Ws thats affected and
its worse at high sowing density.  We've found no evidence for a causal
so we presume its a "disorder" rather than a "disease" and its presumeably
related to season. Plants do seem to grow better at some times of the year than
others though, even though they are kept in regulated growth chambers.  We've
seen it with tomatoes and I've heard about it with peas.  Maybe there is
something to Rupert Shelldrake's ideas afterall! Let me know if you come up
with a solution.  
Alan Slusarenko.

In my first few months at the University of Utah, I was having similar problems
with growing Arabidopsis.  My plants would germinate well, become erect, turn
green, but then stop growing.  Essentially, leaves never formed.  In reality,
however,  leaf development would occur, but at a very slow pace--about 2 months
to get 1-2 leaves.  I did not have the problem of variability within nor
between pots.  
	This problem was solved by changing the soil.  I had been using our standard
greenhouse soil mix that works well for everything (hundreds of species) in our
greenhouse (except Arabidopsis).  I do not know what is in this soil mix, but I
can easily find out if you wish.  Jennifer Normanly suggested to me that the
problem might be due to the soil (based on a similar problem they had in the
Fink lab), so I went to my local greenhouse store and bought every kind of soil
they sold.  For all soil mixes, the plants grew normally---not stunted.  Thus,
as Jennifer suggested, our standard greenhouse soil was causing the stunted
growth.  I never carried it further to determine whether the stunted growth was
due to lack of a nutrient or to the presence of a toxin.
	On top of the stunted growth was a second problem of the cotyledons (and
leaves, if any) turning purple (anthocyanin accumulation).  This apparantly was
related to the light because it only occured in plants grown in the greenhouse
and did not occur if plants grown under artifical light.  My feeling about this
was that there might be too much light in the greenhouse--normally not a
problem but became a problem because of the additional stress caused by the
soil mix.
	My only recommendation is that you try some other soil mixes.  The one I
settled on is called sunshine mix, extra fine grade.  It is expensive, but
works well.  Let me know if you need any more information.
Gary Drews
drews at

Rob, I have for a long time used the Metromix 350 without ever exper-
iencing a problem - except in addition to the $6/bag it costs $5/bag
to ship it to Arizona.  It is balanced to hold the pH at a desired
level for Arabidopsis.  Sometimes when we do transplants the plants
will initially accumulate some anthocyanins - give them a little water
at low pH and the symptoms go away.  In Randy Scholl's lab we used to
use only medium grade Vermiculite and water with Hoagland's.  This s
system is a little more work, and unless you put Magnesium rather than
Manganese in the minors, it produces extremely healthy plants. ken 

hi Rob. We have had episodes of bad soil which sound very similar to your
problems.  Most of the time, it was due to a certain lot number of soil
being bad (use Grace's Metromix 200).  For a while, we switched to using
soil from Farfed, but this proved to be a problem because that soil holds
too much moisture and promotes the growth of algae and mold on the surface
of the soil.  The best solution that I can suggest is keeping track of the
lot number and we actually do quality control when a new lot number of
soil comes in to make sure that the plants grow well.   This is time
consuming but worth while when you are dealing with important experiments...
We had limited success with trying to resue the seedlings using 1/4x Hoaglands
solution, but this will not help you when you are doing physiology.  
Good luck, jean greenberg

Potential solutions (that you probably have already considered):
1) autoclave the soil 
2) don't overwater the plants (in the summer it is more humid so they don't dry
3) change soil mixes - we use 1:1:1 perlite, vermiculite, supersoil (potting
Hope you solve the problem,
Tom Jack
Meyerowitz' lab

In my experience it's easier to switch to a new mix than figure out
exactly what's wrong with the old one.  Many of us in the Dept. of
Plant Biology at Berkeley have found that Sunshine Mix works very well.
I've been getting it from a local hardware/garden store but it
can also be found in nursery supply catalogs like McCalif.
Eva Huala
UC Berkeley

Your message makes a bad nightmare come back to haunt me.  I had a similar prob
lem twice in the last 2 years.  The first instance was when a shipment of
generic potting mix was lacking fertilizer.  When we used a general purpose
fertilizer, (Peter's GP) the problem seemed to be resolved.  The second
instance was when we switched to Grace's Metromix 350.  Initial plantings
indicated that added
fertilizer had a minor effect on growth.  However, one month later, Arabidopsis
was germinating but not developing further except for high anthocyanin.  Some
 plants did grow normally, but in a seemingly random fashion except for an edge
 effect.  Once again, fertilizer overcame the problem.  Currently I routinely
sterilize the potting mix and wet the soil with a general fertilizer.  My guess
is that the problem is nutrient deficiencies, (perhaps mineral sequestration in
the peat), that can be overcome in part by the mineral content in the water and
water evaporation at the edges.  Best-o-luck.  
Jim Tokuhisa   Inst. Biol. Chem.  
Washington State University, Pullman, WA

  We have had much similar difficulty in our studies of mutant 
sweetclover.  It turns out that the culprit is a fungus fly which 
consumes the roots of the young plants.  Spraying with diazanon 
usually cures the problem.  On a couple of occasions when the 
infestation was extreme, we turned up the temperature in our chambers 
to 45 C for a week or so and then started over with new pots and soil.
 I hope that this helps
John Markwell
Dept. Biochemistry
Univ. Nebraska

Rob, I have experienced some of these similar problem with corn in a
soilless mix. While it was difficult to trace, I believe the problem was
in the water. You might look into a water analysis.
roger krueger

Hi Rob, 
Your problem sounds an awful lot like one we had last year.  We have always
used Metromix 200 (made by Grace).  Last year, our plants suddenly started
dying (or failing to thrive, anyway). We had our greenhouse manager (Tracy
Byford) call.  She found out that they had changed the chemical wetting agent
that they put in all their soilless mixes (although they wouldn't tell her what
the new agent was).  Since then, we have taken to putting soil in pots and
soaking  it
thoroughly before planting (I try to flush through at least 1 gallon of
water per flat).  If we are right about the problem, this seems to rinse
out any toxic chemicals in the soil.  Of course, if it is a seasonal
thing, we could have coincidentally started the rinsing at the same time
as the soil mix fixed itself.  So far, the problem has not recurred.  If
Grace has any other suggestions, please let us know (just in case). 
Good luck, Laura Conway.

Hi, I'm Lynne Reuber from the Ausubel lab.  We have experienced similar 
problems with individual lots of Metro-Mix and Fahfard potting soils.  We 
don't know what has caused these problems--we'd certainly be interested in what
you find out from anyone else.  Our solution has been to have the 
greenhouse manager test each lot of soil before setting it out for use
in the greenhouse--low tech, but at least we aren't losing any more plants.

Dear Rob,
 We too often use Redi-earth soil-less mix.  One major problem that we
encounter is infestation with fungus gnats.  The larvae love the mix, as well
as our former growing mix, which included soil and peat moss.  The symptoms are
exactly what you describe, and they can be quite devastating.  The tell-tale
sign, of course, is the presence of the insects themselves: adults are black,
about half the size of a mosquito, and fly around very well.  The larvae can
often be spotted under a microscope crawling in the soil.  I would not be
surprised if one larva could destroy the roots of most of the plants in a pot. 
If this is your problem, I have two suggestions: first, there is a
commercially-available bacteria that eat fungus gnat larvae.  It has been quite
a lifesaver for us, and we never plant without it.  Second, you can put fly
traps in the growing chambers in order to cut down on the adult population. 
We've also experimented with soil mixes that don't use peat moss and may also
help cut down on the population.  Let me know if you suspect that this is your
problem.  If it is, I can give you details about how we combat these pests.  

Mark Running
Meyerowitz Lab

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