91 



The area of each bar represents the total supply of S in that 

 horizon. The surface horizon (0-16 cm) of these soils contained a mean 

 total of 9 kg/ha of extractable S and 200 kg/ha of total S. The entire 

 profile to 100 cm contained only 36 kg/ha of extractable S. This would 

 probably be an adequate amount of S for a growing crop if roots were 

 able to penetrate and absorb S from the entire soil volume. However, 

 roots may not extend beyond the spodic horizon because of excess mois- 

 ture, poor aeration, physical compaction, and an unfavorable chemical 

 environment in this region. 



Both extractable and total S were significantly correlated with 

 organic C and total N in the surface horizons of these soils (Table 13). 

 Most of these soils contained less than 5% of clay-size particles 

 (Table 12), but where there was an increase in clay content, there was 

 a significant increase in soil S. Soil mineralogy was not studied on 

 a sufficient number of horizons to establish any reliable correlations 

 between dominant clay minerals and soil S. Clay-size quartz and 2:1 

 intergrade minerals dominated the mineralogy of the soil colloids. 



Organic C was also highly correlated (r = 0.91) with total S in 

 the subsurface horizons. Sodium pyrophosphate soluble Al was higher 

 in the spodic horizons and was highly correlated with total S (r = 

 0.86). The fact that Al was correlated with total S and not corre- 

 lated with extractable S may indicate that sulfate is selectively held 

 by Al in a non-exchangeable form in the spodic horizon. 

 7.2 ENTISOLS 



Florida Entisols had more extractable S within their profiles than 

 the Spodosols. Total S and extractable S were nearly uniform in all 

 horizons below the surface (Table 14, Fig. 8). These soils had an 



