similar to C:N:S relationships reported earlier for soils in Australia 

 and New Zealand (Williams and Donald, 1957; Walker and Adams, 19 58; 

 Williams and Steinbergs, 1958). Nelson (1964a) found an average 

 organic C:N:S ratio of 114:9.1:1 in the surface horizons of 12 Missis- 

 sippi soils which had a wide range of organic matter contents. Organic 

 S was highly correlated with total S (r = 0.9 20) and organic C (r = 

 0.947) but not with soluble sulfate-S. The C:N:S ratio of Louisiana 

 soils was found to be 88:8.3:1 for surface horizons and 94:10:1 for 

 subsurface horizons (Bonner, 1973). Tabatabai and Bremner (1972b) also 

 found significant correlations between total S and organic C (r = 0.86) 

 and between total S and total N (r = 0.87) in Iowa soils. Total S 

 decreased with depth in the soil profile but remained significantly 

 correlated to organic C (r = 0.86) and total N (r = 0.92). 



The organic C:S ratio, like the N:S ratio, can be used to predict 

 S mineralization or immobilization by soil microorganisms. Massoumi 

 and Cornfield (1965) showed that the addition of cellulose to a soil 

 resulted in a decline in available sulfate levels as the microorganism 

 populations growing on the polysaccharide assimilate inorganic S. If 

 the organic matter contains less S than required for microbial pro- 

 liferation, immobilization will be dominant; if the element is in 

 excess, mineralization of S will result. Barrow (1960a) found that 

 mineralization of S from soil organic matter did not occur until 

 catabolism had lowered the C:S ratio to about 50:1. He also found 

 that immobilization of S occurred in soils during a 12-week decomposi- 

 tion period when the C:S ratio of the original organic material was 

 greater than 200:1 (Barrow, 1960b). Tabatabai and Bremner (1972b) 

 found that most Iowa soils immobilized S when incubated for 2 weeks, 



