One of the articles titled "Compost and Composting: Facts
and Myths" gets into composting vs soil application.
"Most people think that making compost is to create fertilizer.
Other people use composting to creat a potting soil. Ten other
reasons for so-called composting are...
1. to decrease the volume of waste, especially for going into
2. to decrease odors,
3. to kill pathogens and weed seeds,
4. to create more favorable carbon:nitrogen ratios so as to not
induce nitrogen deficiencies in crops,
5. to destroy natural toxins like tannins and allelopathic
6. to decrease levels of synthetic pesticides that may be in organic
waste by partial if not complete decomposition of them,
7. to provide a means for making iron and other micronutrients
available to plants,
8. to impart to soil a mechanism for retarding soil-borne diseases
9. to make a more convenient product for applying to
10.to provide a means for increasing the cation-exchange capacity
of the soil, the water-holding capacity of the soil, and to
decrease crusting and erosion or soil.
Additionally, many believe that composts help decrease the incidence
of plant diseases other than soil-borne."
"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."