Futral (1966) found that yields of cotton were not affected by S 

 application during the first 2 years of an experiment on a Norfolk 

 loamy sand from Georgia. This soil had extractable sulfate levels 

 within its profile similar to the Norfolk soil used in this study. By 

 the third year of the experiment, marked deficiency symptoms appeared 

 on the nc-S plots early in the season but disappeared as plant size 

 increased. By the fifth year, plants failed to recover from the S 

 deficiency, and there were highly significant yield increases where S 

 was applied. Cotton is a crop that is known to be sensitive to S de- 

 ficiencies (Lund and Murdock, 1978) . 



Subsoil S and the depth to this S in Ultisols may create compli- 

 cations in field experiments. This problem will be pointed out in the 

 section entitled "Sulfur in Bahiagrass and Bermudagrass. " 

 8.3 SULFUR CONCENTRATIONS AND N : S RATIOS 



The application of 20 ppm of S to these soils significantly in- 

 creased the S concentraions in the tissue, reduced the N:S ratios, and 

 resulted in increased S uptake by the plants in almost every series, 

 harvest, and horizon sequence (Tables 21, 22, 23, and 24). These data 

 indicated a close relationship between S concentration in the tissues 

 and dry matter yield of the plant. Relative yields were calculated 

 within each series and harvest and plotted against S concentration 

 (Fig. 11). A critical S concentration of 0.12% was identified for 

 sorghum-sudangrass tops using a segmented model and the non-linear 

 least squares method provided by SAS (Statistical Analysis System, 

 1979). Data fit a model described by two linear relationships: 



