[Digestion] Digestate as fertilizer.

[Jean-Luc Sallustro]

Dear Anand,

I am really interested by this vision of sugar nutrient cycle.
Let me say first that even if I am from Europe, (you are right on this
point) my group is in Mauritius, and then involved with sugar cane
agronomy (or other Poacae)
Sure that cellulose is a kind of sugar ... but strongly polymerized, at
a point that the only bacterial strain enabling its degradation is
aerobic and particularly thermophilic.
Soils macro decomposers such as colemboles or worms alternatively or
complementary play a role within this decomposition stage of cellulose
and hemicellulosis.
What seems to me of utmost interest in your assessment is that sugar (I
assume you are considering raw sugar ?) provides for direct enhancement
of soil fertility (when bring with organic N) for the reason that this
immediately available energy positively stresses bacterial flora (but
which strains in particular ?) and then allows the production of mineral
nutrients to reach the plants depending on export demands (Poacae are C4
type and therefore strongly dependant from photocycles and water
availability).
The way different +/- polymerized sugars reach the soil is a well known
thing, but what's about humus role (even as thin it seems ... there is
always an upper layer of biomass on the 0 to 15 cm depth of soils), and
what is happening as an interaction between microbial activity in this
superior soil level, sugar solution (rain fed context) and other N
linked bacterial strains ?
My hypothesis was that there is a risk of demobilisation of these
endemic bacterial strains, maybe one can put the question like this
"when stopping "sugar feeding" what will happen with organic N, P and K
availability ?"
All the best
Jean-Luc

Le lundi 04 juillet 2011 à 12:11 +0800, Anand Karve a écrit :

> Dear Jean-Luc,
> feeding sugar to the soil microbes is done by the plants themselves.
> The water of guttation of sorghum and safflower contains sugar. All
> the plants that are infested by aphids also drop sugar on the ground
> below their canopy. The leaves that fall on the ground also contain a
> type of sugar (cellulose), In the case of many trees, one finds a
> carpet of fruits underneath their canopy. The fruits contain sugars.
> Chickpea (Cicer arietinum) leaves exude organic acids, which too fall
> on the ground to feed the soil microbes. In India, in the region where
> I live, literally thousands of farmers have taken up the practice of
> applying sugar to the field. For every hectare,they use a mixture of
> 25 kg sugar, 25 kg cattle dung and 25 litres cattle urine. It is
> applied once every three months. In an earlier experiment, I got the
> soil from a non-irrigated and non-fertilized field analysed
> consecutively for 5 years and found that in spite of growing crops on
> this soil, there was no change in the soil composition over this
> period. In India, the agricultural yield is positively correlated with
> the rainfall and not with any other factors like the sale of
> fertilizers, pesticides, hybrid seed, etc. Humus is a typical topic
> raised by European agricultural scientists. Nobody talks of it in
> India, most probably because our soils do not have the humus layer
> that European soils have.
> Yours
> A.D.Karve
> 
> On Sun, Jul 3, 2011 at 10:52 PM, Jean-Luc Sallustro
> <jean-luc.sallustro at eventure-international.com> wrote:
> > Dear A  D Karve
> >
> > For my understanding microbes have an important role in the soil at a stage
> > where endemic proto nutrient are made available for them within the humic
> > clay complex.
> > This deep stage of macro nutrient (organic NPK) evolution can be depleted
> > for many reasons such as K sustainable sequestration, unavailability of
> > macro nutrient, not enough water percolation (soil solubility) etc.
> > Don't you think that one of the risks of depletion in N chain can be the
> > demobilization of upper soil decomposers due to the fact that immedialty
> > avalible nutrient are provided (sugar)
> > Regards
> > J-L Sallustro
> >
> 
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