[Digestion] Digestion Digest, Vol 2, Issue 31

Anand Karve adkarve at gmail.com
Fri Oct 15 21:04:25 PDT 2010

Dear Ivo and AD workers,
there is a lot of misunderstanding about effect of organic material on crop
yield. The textbooks say that plants cannot absorb the minerals in the soil,
because they are insoluble in water, and therefore one has to apply water
soluble chemicals in the form of fertilizers or organic composts to a field.
The textbooks also explain that one needs a high population of microbes in
the soil for decomposing  the organic matter because it is the microbes
that make the minerals in the organic matter available to the plants. Both
the assumptions in the text books are wrong. Let me first of all point out
that water is a universal solvent, and that it dissolves all minerals in the
soil. Silica is present in the soil in the form of quartz, opal and various
silicate minerals. They are considered by the lay public to be insoluble in
water, but the capillary water in the soil contains from 5 to 15 p.p.m.
(parts per million or mg per litre of water) silica. That plants can take up
silica from the soil is dmonstrated by the fact that a single crop of wheat
or rice removes from the soil about 250 kg silica per ha. This is possible,
because the silica and all other minerals dissolved in the capillary water
in the soil, are in a dynamic equilibrium with the water. That means, that
molecules removed by plants from the soil solution, are replaced by new
ones contributed by the undissolved pool of minerals in the soil. Therefore,
in spite of the plants taking up the minerals from the
soil, the concentration of the minerals in the soil-water remains constant.
Once we accept the fact, that plants can take up minerals directly from the
soil, it can be shown that about 1 m thick layer of soil has enough minerals
in it to support agriculture without fertilizers for the next 25,000 years.
In semi-arid regions, farmers who depend solely on rainfall as the source of
water, never apply any fertilizers to their crops, because, if the rains
were to fail, they would lose all the money spent of fertilizers. In spite
of farming in this manner for thousands of years, they continue to get more
or less the same yield from their farms, year after year.

On Thu, Oct 14, 2010 at 6:18 AM, Ivo Oliveira <ivomdb at gmail.com> wrote:

> Hello,
> I've been reading a couple of documents about vermicompost and digester
> effluent aplication to different crops. For exemple: Vegetables (carrot,
> spinach, onions etc), Fruits and maize. For instance when applying digester
> effluent to vegetables 100 l per hectare (of a total 300 l mixed with water
> on a 1:3 ratio) should be added every 10 days. It seems quite small....
> However I found in other articles that you can apply raw digester effluent
> without dilution but doesn't say the amounts that should be added.
> Using Vermicompost the information seems more available but still not sure.
> For example I found that you can apply 120 g of vermicompost/ plant (crop)
> or 60 g or 10 g to vegetables.....
> So... the information available is some what diverse. I wonder if someone
> could share his knowledge when using digester effluent or vermicompost as an
> organic fertilizer.
> Thanks,
> Ivo Oliveira
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