I'm in the San Joaquin valley. Our soil tends to be alkaline. Well, at the
elementary school, we have a Life Lab (hands on science w/garden plots). I
have a few teachers who want to grow potatoes.
My gardening book says that pototoes need acidic soil but not to use lime.
How else do I get the soil to move to the acidic side? We're about 7.5 to
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Plant in plenty of compost/manure. Potatoes are generally not fussy about
soil types, they're one of the easiest things to grow, always recommended
for the beginner and for children. Further to an earlier thread, I would
recommend chitting them before planting, i.e put them in boxes in the light
so they start to sprout. Kids will especially like this part of the process.
Isn't the San Joaquin valley in California? I don't know anything about
frost conditions there, but they should be planted out when there's not too
much danger of frost. Once they're showing, if a frost is forecast, bury the
tips with an inch or two of soil, and that will protect them.
Incidentally, I think it's great that you're getting the kids interested
from an early age, I'm not sure that many schools here in UK do much in that
Manure like Steve suggests is probably one of the best ways so long as it is
thoroughly decomposed. In any case, you wouldn't use lime to make the soil
more acid. Lime would make it even more basic than you are already. For
quick drops in pH, aluminum sulfate is usually recommended. Powdered sulfur
should drop it over the long run along with the added compost. Manure itself
would help buffer the pH and not really acidify the soil but maybe help
neutralize it on top of the other benefits supplied by the organic material
including moisture retention.
I hope the kids get a good crop.
I agree with all the comments and advice you give, except the use of
aluminium sulfate to lower pH. Aluminium salts have been linked with
health problems, in particular, increasing the development of Alzheimers
disease. My suggestion for lowering pH (beyond the excellent ones of
compost and powdered sulfur) is to add citric acid, which you might be
able to get in pharmacies or even ethnic food shops, or pine needles are
very acidic if I recall correctly. In terms of ease of finding and cost,
sulfur might be the best, but it is apparently easy to add too much and
end with very acidic soil.
I agree with you that aluminum has been implicated in the progression
(possible cause?) of Alzheimers disease but there is no proof or indication
that the aluminum comes from salts in the soil absorbed by plants. How many
people cook in aluminum cookware including high temp frying pans? How many
take megadoses of Maalox (magnesium aluminum hydroxide) for upset stomach?
8% of the earth's crust is aluminum. To be sure most of it is fairly inert
aluminum oxide but that still leaves plenty of room for other salts. You're
not going to escape aluminum most anywhere you go so I really don't think
the amount required to correct pH is going to add to your annual intake from
As I pointed out, it's really just a quick fix anyway. I live in an area of
pines and oaks and we have acidic soil. However, the pinestraw mulch lends
little to the acidity as it breaks down fairly quickly and doesn't affect
more than the upper 1/2". The pH is 4.9-5.0 yet 1/2 lb of lime over 100 sq
ft is enough to bring the pH up to 6.5. So I wouldn't recommend pinestraw to
change the pH. It might help maintain established acidity but not change it.
Best is the long term solution. Or simply to avoid crops that are that
sensitive to pH.
Yes, lime is to make soil alkaline. I think you should consider other
crops because the potatoes will be miserable. Changing the pH on the
fly is easier said than done and you may ruin the whole plot for a
while by applying too much sulfate. Onion, chard, beet, and just about
any brassica (broccoli, cabbage, collard, kale) will grow well in
alkaline conditions. Kale will give you something edible in six weeks
if the weather cooperates.
You still have to add a little organic matter and fertilizer to make
them happy. If you apply manure, it will provide both. In your
conditions, one of the best organic amendments are wood chips, that
will lower pH (they are acid), give you good mulch and good humus. You
have to add some nitrogen fertilizer (a single bag will be good for the
whole school garden).
On the other hand, wood chips are OK only if you plant little plants or
big seeds like squash. You cannot seed directly things like kale (many
small seeds) on wood chips until they have decomposed.
Make a Google search and you should find a few more crops that will be
happy above 7.0. I am guessing, for example, that lettuce, garlic,
beans, peas and tomatoes will manage with that soil. Various squashes
and cukes might be a little less happy but still manage. Potatoes are
really the only big no-no.
the plots are individual so no worries about ruining everything. I'll plant
4 x 20 of pototoes. Hopefully, the weather will cooperate.
It's too late to grow any of the cool season vegetables here. In fact, I've
had broccoli bolt already. I'm familiar with most veggies and flowers for
this area. I'm a master gardener which is offered thru UC Davis. Taught
life science and gardening for 4 years.
the pototoes are a special request so I'm doing it for 2 of the teachers.
For some bizarre reason, the current teacher knows nothing about
horticulture.... makes no sense but oh well
Have you looked at the potato growing information at the Santa Clara
County Master Gardeners website? They have a good way of growing
potatoes in a half-barrel where you can use packaged soil and not have
to worry about these issues. Also, potatoes can be prone to certain
plant diseases that can make the soil unsuitable for other crops later
(such as strawberries). Using a half-barrel should avoid that problem.
I suggest using their pile method--a half barrel with a wire cage over
the top that you keep heaping straw upon to create a higher and higher
stack throughout the growing season, that becomes rife with potatoes.
The wire cage keeps the straw from falling off--anyway the details are
at their website.
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