RE: [compost_tea] Inclusion of clay in compost
>From Steve Diver on another list...
Selman Waksman wrote about clay addition to composts.
Ehrenfried Pfeiffer, an early compost pioneer in the US,
promoted clay additions to compost. More recently,
Siegfried Luebke in Austria developed the Controlled
Microbial Compost method, also based on clay additions.
Edwin Blosser with Midwest Biosystems in the USA
promotes Advanced Composting Systems based on
clay additions. CMC and ACS amount to a whole system
of "intensive" windrow managment to achieve humified
compost. Analysis via laboratory and microscopy show
consistene, good compost quality with humification of organic
matter.
Excerpts from "A Treatise on the Vital Role of Clay-Humus
Crumb Structure and Organo-Mineral Complexes in Soils"
on my web page.
"Among the important aspects of humus in the soil, the most
significant is its interaction with the clay constituents, which
give rise to clay-humus."
"In this respect two types of soil are frequently recognized:
in one the clay and humus particles are held together by
calcium ions, in the other iron (and possibly manganese and
aluminum) may replace calcium.
Tiulin classified the soil colloids into two groups:
The group I colloids of Tiulin comprise the clay-humus complex
which is held together by calcium ions. Agriculturally, it is
believed to be the most important type. This complex is largely
responsible for the favorable physical condistions found in
various soils and composts. The clay appears to have an
appreciable base-exchange capacity. The presence of calcium is
essential if only for ensuring the formation of the correct
type of humus.
"Increasing the amount of soil organic matter in this combination is
of great importance. The addition of clay to sandy soil may be as
important as the addition of organic matter itself."
"A certain quantity of stable manure or compost or mass of plant
residues can be converted into this type of complex only when it is
composted with a certain amount of clay before it is applied to the
soil."
Waksman, Selman. 1952. Soil Microbiology. John Wiley & Sons, New
York. p. 129-130.
There is relevant information on soil applied organic matter
vs composted organic matter in the two volume series
from Wallace Laboratories.... "Soil Conditioner and Amendment
Technologies".
There is a microscope method that is a great way to view
humification of soils and composts, used by Siegfried Luebke's
lab in Austria. Pike Agri-Lab in Maine put $30,000 into a
comparable microscope setup.
The Humus Colorimetric Test based on the sodium hydroxide
method was upgraded by Austrian soil scientists to handle
the high-end humified composts from CMC. It is now
being used by several labs in the US. Humification with
CMC compost was off the charts based on the humus
test in the old LaMotte Soil Test.
The Potential pH Test is simple, but interesting. From
"Controlled Microbial Composting and Humus Management:
Luebke Compost" on my web page.
"The potential pH test is a simple method for determining the exchange
capacity of a soil or compost sample. Indirectly, it is a measure of
biological
activity and degree of humification. This test is described by
Struchtemeyer
in Basic Properties of Forest Soils (5).
In brief, two samples are prepared. The first sample is diluted with
distilled
water. A pH reading of this sample will provide the actual pH. The second
sample is diluted with potassium chloride (.1 Molar KCl solution). A pH
reading of this latter sample provides the potential pH.
The degree to which potassium ions displace hydrogen ions on the soil
or compost colloids in solution will be reflected in the difference between
the actual and potential pH readings. This is an indication of the ion
buffering capacity, or the cation exchange capacity, of the sample.
When the pH readings are further apart, they are an indication of poor
exchange capacity. The aim is to achieve as little difference as possible;
less than 0.5 pH units for soils and 0.3 pH units for compost is ideal.
During the humification process, microbes are actively building
long-chain polymers of polysaccharides and other molecules.
Well-developed humus has numerous exchange sites and therefore
holds hydrogen ions more tightly. The actual pH and potential pH
readings will be close together and indicate a high degree of microbial
activity, humus structure, and surface area. Conversely, pH readings
with divergent numbers are an indicator of poor humus development."
Pfeiffer and Luebke use the terms "Breakdown and Buildup"
phases of composting. That is really a great way to understand
the composting process; the phases can be integrated with
temperature and pH curve charts to see how the process
changes with over time.
Steve Diver
ATTRA
Received on Fri Feb 04 2005 - 18:28:16 EST
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