152 



considerably higher than those reported for soils in other 

 areas and may have important implications for organic 3 

 mineralization in these soils. 



4. Spodic horizons contained slightly less extractable and 

 total S than the surface (Al) horizons but considerably 

 more than the A2 horizons. This S did not contribute to 

 the S nutrition of sorghum-sudangrass in the greenhouse 

 and actually reduced yields whan included in a simulated 

 soil profile. 



5. Ultisols contained an average of 33 ppm of extractable S in 

 their argillic horizons. This value represented more than 

 40% of the total S. Adsorbed sulfate in the argillic 

 horizon in a Norfolk soil was sufficient to meet the needs 

 of a sorghum-sundangrass hybrid in the greenhouse for 16 

 weeks; adsorbed sulfate in the argillic horizon of an Orange- 

 burg soil from the same area was not sufficient to meet 



the S needs of the plant beyond 8 weeks. 



6. Entisols are uniformly low in adsorbed S in subsurface hori- 

 zons and contain an average of around 6 ppm of sulfate S. 

 Yields of a sorghum-sudangrass in a Lakeland fine sand were 

 significantly increased by S fertilization after 4 weeks of 

 growth in the greenhouse. Subsoil S contributed to the S 

 nutrition of the plants but not enough to increase yields. 



7. A critical concentration of total S in 4-week old sorghum- 

 sudangrass tops was 0.12%. The critical N:S ratio was 16. 



8. Yields of Pensacola bahiagrass on Myakka fine sand in the 

 field were not increased by S applications the first year. 

 The lowest rate of S, 10 kg/ha, significantly increased 

 total dry matter production the second year at a high rate 

 of N (400 kg/ha) . 



9. Yields of Coastcross I bermudagrass on Kendrick fine sand 



in the field were not increased by S fertilization the first 

 year. Significant yield increases were observed at the 10 

 and 20 kg/ha S rates the second year at the highest rate 

 of N (400 kg/ha). 



10. Spring S applications as gypsum increased the S concentra- 

 tion in the forage and S uptake at every harvest during 

 both years. 



11. Applying S in split applications during the season appar- 

 ently had no benefit over a single application in the 

 early spring. 



12. Spring S applications had no apparent effect on extractable 

 S in the soil profile in the fall. 



