Re: composting vs. soil application of organic residues
Steve Groff (firstname.lastname@example.org)
Thu, 17 Sep 1998 23:59:55 -0400
> "For improvement of physical properties of soil, actual decomposition
> in the soil, rather than composting, is best because polysacharides
> are produced from carbon compounds that would otherwise be lost in
> composting. These natural water-soluble polymers do much to create
> and stabilize the soil aggregates to give good physical properties to
> soil. It may be better to use the carbon to synthesize
> polysaccharides than to burn a lot of it to make heat to sterilize
> the compost, unless sterilization is necessary like with sewage
> sludge. For the same reason, partially decomposed organic matter
> obtained in the first phase of composting may be better for soil
> improvement than would mature composts which function mostly as a
> soil amendment that dilutes the soil, decreases bulk density, and
> gives more pore space in the soil because of the wedges."
> >From the section titled "Some Erroneous Concepts About Compost":
> The notion:
> "Compost benefits the soil significantly more than the original
> composted materials"
> Wallace's Comment:
> "Although there are good reasons for composting, the idea can be
> wrong much of the time. Since 75 percent, more or less, of the
> organic carbon is lost in composting, little remains for real
> improvement of the soil structure. When possible, direct application
> avoids this problem. The value of organics for soil improvement
> comes mainly from carbohydrates. Carbohydrates are mostly lost in
> composting. Some users assume that the composting process results in
> the production of biostimulants; uncomposted materials applied to
> soil can result in the same."
> Wallace, Arthur and Garn A. Wallace. 1995. Compost and composting:
> facts and myths. p. 39-51. Soil Conditioner and Amendment
> Technologies, Volume 1. Wallace Laboratories, Los Angeles, CA.
> 335 pp.
> Thus, it seems Wallace's observations jives with Joel Gruver's
> findings that soil applied organic materials enhance soil aggregation
> via polysaccarides. This is certainly true with the addition of
> fresh green manures (or any other fresh organic matter), which
> are rapidly attacked by soil microbes. The glues and slimes
> released by the microbes during decomposition help to bind the
> soil particles together. This is a desirable process, and one of the
> reasons green manures are so widely used in organic crop production.
> Joel suggests the addition of clays or soils to compost piles to
> reduce Carbon loss. As an aside it is a common practice in
> several of the European-derived compost systems to add clay loam at
> 10% by volume to enhance formation of the clay-humus crumb.
> In thinking about this topic, it is probably helpful to look at
> organic agriculture as a type of humus management system. It is the
> integration of all the practices geared to enhancing soil quality and
> building the humus bank in the soil -- crop rotations, crop residues,
> mulch, cover crops, green manures, animal manures, composts,
> microbial inoculants, grazing, urine, tillage implement etc -- that
> make up the soil health picture.
> Steve Diver
I have observed, on my farm, that much of the above information is legitimate.
Soil aggregate stability is what I've noticed as one of the great improvements
resulting from leaving the residues on the soil surface to decompose. Doesn't
this information build a strong case for the benefits of no-till?
"New Generation Cropping Systems": the cutting edge of sustainable agriculture
Cedar Meadow Farm
679 Hilldale Rd
Holtwood PA 17532 USA
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