124 



(1) y = a + bx 



(2) y = c 



where y represents relative yield and x represents S concentration in 

 the tissue: a, b, and c are constants. The value of x at the inter- 

 section of the two lines (_--<. = 0.12%) is predicted and is considered to 

 be the critical value. This value is within the critical range 

 reported by other workers for grasses (Table 6) . These plants were 

 harvested at 4-week intervals under uniform greenhouse conditions. 

 Therefore, the wide variability in S concentration due to type of tis- 

 sue and plant age was not a problem in this experiment. 



Nitrogen:sulfur ratios were also closely related to relative 

 yields (Fig. 12). Relative yields were calculated within each soil 

 series and harvest. The mean N:S ratio of the 100% yields was 16. 

 This is the value that Dijkshoorn et al. (1960) found for the N:S ratio 

 in protein of perennial ryegrass foliage, and other researchers have 

 confirmed to be an optimum value for the total N:S ratio in grasses 

 (Woodhouse, 1969; Cowling and Jones, 1971; Metson, 1973; Terman et al . , 

 1973) . There did not appear to be any differences in the critical S 

 concentration or the optimum N:S ratio due to soil series or horizon 

 sequence . 



9. SULFUR IN BAHIAGRASS AND BERMUDAGRASS 

 IN THE FIELD 



9.1 SULFUR IN BAHIAGRASS ON A MYAKKA FINE SAND 



The site of this experiment was adjacent to the site where the 



Myakka soil was collected for the previous experiment. However, 



responses to S by bahiagrass were noc as dramatic as the response to S 



by sorghum-sudangrass in the greenhouse. 



