R

PO2-

of the ester S into the culture medium. Sulfolipids, which represent another form of ester sulfate, have been reported for a limited number of bacteria. Algal sulfate esters also exist; the well-known algal compound, agar, is a sulfuric acid ester of a linear galactan. Other forms of organic S, such as phenyl sulfates and elemental S, have been found in a variety of soil organisms. Elemental S has been identified in the sporocarps of ectomycorrhizal fungi as well as in other self-inhibited and dormant structures. It is deposited by some of the bacteria capable of utilizing H2S as an electron donor during photosynthesis.

The C:S ratio in SOM is not as consistent as is the C:N ratio. Major differences are found due to type of parent material, leaching, and S inputs. A worldwide C:N:S ratio could be considered as 130:10:1. Agricultural and grassland soils average 90:8:1; luvisols and spodosols under forest conditions can range up to 200:12:1. Wide ratios are found in areas of low S supply, and fertilization with S or atmospheric deposition raises the soil S level.

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Organic Gardeners Composting

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