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2.3 EVALUATING THE SULFUR REQUIREMENT OF CROPS 43 



2.3.1 Critical Concentrations 43 



2.3.2 N:S Ratios 43 



2.3.3 Sulfate Sulfur 48 



2.4 EVALUATING THE SULFUR FERTILITY STATUS OF SOILS ... 50 



2.4.1 Extraction Techniques 50 



2.4.1 Biological Techniques 55 



3. SULFUR FERTILITY STUDIES IN FLORIDA 57 



III. MATERIALS AND METHODS 62 



4. EXPERIMENTAL METHODS 62 



4.1 SULFUR DISTRIBUTION IN SELECTED FLORDIA SOILS .... 62 



4.2 A GREENHOUSE EVALUATION OF SUBSOIL SULFUR IN 



FOUR FLORIDA SOILS 62 



4.3 SULFUR IN BAHIAGRASS AND BERMUDAGRASS 70 



5. LABORATORY ANALYSES 72 



5.1 NITROGEN 72 



5.1.1 Total Nitrogen in Plant Tissue 72 



5.1.2 Total Nitrogen in Soils 73 



5.2 SULFUR 73 



5.2.1 Tissue Digestion for Total Sulfur 73 



5.2.2 Soil Extraction for Sulfate Sulfur 73 



5.2.3 A Comparison of Two Extraction Procedures 



for Soil Sulfur 74 



5.2.4 Estimation of Total Sulfur in Soils 76 



6. ANALYTICAL TECHNIQUES FOR DETERMINING SULFUR 32 



6.1 TURBIDIMETRY 84 



6.2 INDIRECT METHODS 84 



IV. RESULTS AND DISCUSSION 86 



7. SULFUR DISTRIBUTION IN SELECTED FLORIDA SOILS 86 



7.1 SPODOSOLS 86 



7.2 ENTISOLS 91 



7.3 ULTISOLS 97 



7.4 C:N:S RELATIONSHIPS 106 



- 8. A GREENHOUSE EVALUATION OF SUBSOIL SULFUR 109 



8.1 CHEMICAL AND MINERALOGICAL PROPERTIES OF 



SOILS STUDIES 109 



8.2 YIELDS 112 



8.2.1 Harvest i 112 



2 Harvests 2,3, and 4 117 



2.1 Myakka 117 



2.2 Lakeland 119 



2.3 Orangeburg and Norfolk 119 



8.2 

 8.2 

 8.2 

 8.2 



8.3 SULFUR CONCENTRATIONS AND N:S RATIOS II 



