2 

 marginally successful. Organic matter is the largest source of soil S 

 in most Florida soils, but the availability and dependability of this S 

 are difficult to determine. Soils which contain an argillic horizon 

 such as the Ultisols of northern Florida contain large quantities of 

 adsorbed S associated with the clay and minerals in this subsurface 

 horizon. This S may be an important source for crops, but the roots of 

 young seedlings must germinate and grow through 20 to 60 cm of leached, 

 sandy soil to reach it. Spodic horizons of flatwoods soils (Spodoscls"! 

 and subsurface horizons of Florida's sandy Entisols supply an unknown 

 amount of S to crops and are incapable of retaining much applied S. 



The atmosphere may be an important contributor to the S nutrition 

 of Florida crops. Sulfate-S in rainfall and the direct absorption of 

 SO through plant leaves may supply all of a plant's S needs in some 

 locations, but this source has not been evaluated in Florida. 



Because S is an essential component of certain amino acids, it is 

 an important consideration in assessing forage quality. Forages such 

 as bahiagrass ( Paspalum not a tu rn Flugge) and bermudagrass ( Cvnodon 

 dactylon L.) require high rates of N for optimum yields, but their 

 pre tain contents and quality remain quite low when compared to some 

 other grasses and legumes. Sulfur fertilization has been shown to 

 improve crop quality, and where large quantities of S have been 

 removed in successive cropping of these forages, yields may be in- 

 creased with S fertilization. 



Little research has been conducted with S as a plant nutrient in 

 Florida soils during the past 25 years. This dissertation will review 

 pertinent S research as it relates to soil fertility and crop nutri- 

 tion, and evaluate the current S fertility status of representative 



