108 



and total S definitely increased with depth in Ultisols , and this 

 increase is not related to organic matter. As previously noted, 

 organic S is important in spodic horizons, but this study did not 

 attempt to quantify the relative contribution of organic matter and 

 soil minerals to total S present. 



The surface horizons of all three orders of Florida soils had much 

 wider C:S ratios and narrower N:S ratios than was found in soils from 

 other areas (Table 1). The C:N:S relationship for the surface horizons 

 of Florida Ultisols (112:7.1:1) more closely resembles the findings of 

 Neptune et al. (1975) for six Brazilian surface soils (121:6.2:1) and 

 is similar to the findings of Nelson (1964) for 12 Mississippi soils 

 (114:9.1:1). 



The significance of differences in the C:N:S ratios of soils may 

 be related to the S supply to crops (Biederbeck, 1978) . Mineralization 

 of organic S has been found to increase as the C:N:S ratio decreases 

 (Bettany et al. , 1973, 1974; Kowalenko and Lowe, 1975). Bettany et 

 al. (19 79, 1980) found higher C:S and N:S ratios in humic acid and 

 humin fractions of soil organic matter than in the more labile fulvic 

 acid fractions. The humic acid A, humic acid B, and fulvic acid B 

 fractions had C:N:S ratios of 101:7.9:1, 95:8.8:1, and 37:5.6:1, 

 respectively, in undisturbed pasture soils and ratios of 127:8.7:1, 

 96:8.2:1, and 36:5.5:1, respectively, in cultivated soils. The humic 

 acid fraction also had a higher percentage of C-bonded S associated 

 with the more stable humin fractions. The present study did not in- 

 volve organic S fractionation so only speculation can be made. This 

 aspect of soil S and organic matter warrants closer study in future 

 research. 



