15] 



SECTION V 

 SUMMARY AND CONCLUSIONS 



The experiments discussed in this study complement the S fer- 

 tility work done in the 1950' s by Bartlett, Neller, and others. Their 

 work pointed out that most Florida soils were low in available S, and 

 many crops, particularly legumes, would respond to S applications in 

 the field. Even though available soil S may be inadequate for many 

 crops in Florida soils, data from this study and recent studies of 

 atmospheric S showed that S from rainfall, direct absorption of S0 9 

 by the soil and plant leaves, and available soil S may be adequate for 

 low to moderate crop yields. Non-fertilizer sources of S account for 

 an estimated minimum of 21 kg/ha of plant-available S. With an average 

 of 15 to 39 kg of S applied in fertilizers per harvested hectare in 

 Florida, S deficiencies among field crops are unlikely. However, where 

 high-analysis fertilizers containing little or no S are used and high 

 yields are maintained, S deficiencies are likely to appear. 



The following are additional conclusions which may be made from 

 the experiments reported in this work: 



1. The surface 15 cm of most Florida soils contain less than 5 

 ppm of extractable sulfate S and are unable to provide ade- 

 quate S co a growing crop for more than 4 to 8 weeks without 

 additional sources of S. 



2. Total S in the surface horizons (0-15 cm) of Florida Spodo- 

 scls, Entisols, and Ultisols averaged 74 ppm and was highly 

 correlated with organic C (r=0.89) and total N (r=0.95). 



3. C:N:S ratios in the surface horizons of selected Florida 

 Spodosols, Entisols, and Ultisols averaged 150:6.4:1, 

 166:5.9:1, and 112:7.1:1, respectively. These ratios are 



