117 

 slightly higher in all soils than values obtained in earlier analyses 

 (Tables 20 and 25) . These differences could have been caused by drying 

 of the soils or mineralization during incubation. In either case, ade- 

 quate S was present in all soils except the Myakka for optimum growth 

 during the first 4 weeks. No differences were observed due to subsoil 

 S in the first harvest. 

 8.2.2 Harvests 2, 3, and 4 

 8.2.2.1 Myakka 



The yield response to S in the Myakka soil was intensified in sub- 

 sequent harvests (Table 21). Ratoon crops in soil without added S 

 showed immediate symptoms of S deficiency in growth following the ini- 

 tial harvest. Leaves showed marked interveinal yellowing with some 

 reddening of stems and leaf edges. These symptoms were obvious through- 

 out the next 12 weeks of the experiment. Where S was omitted, dry 

 matter yields at the fourth harvest were only 24% of the initial yields. 



The presence of the spodic horizon within the profile signifi- 

 cantly reduced yields in the third and fourth harvests. The high acid- 

 ity and soluble Al in this horizon would be expected to inhibit root 

 penetration and proliferation into the unamended subsoil. Soil pH and 

 sodium pyrophosphate-soluble Al in the spodic horizon were comparable 

 to soil pH and citrate-dithionite soluble Al in the argillic horizons 

 of the Orangeburg and Norfolk soils. Citrate-dithionite soluble Fe in 

 the argillic horizons of the Ultisols was much higher in proportion to 

 the soluble Fe levels in the spodic horizon of the Myakka soil 

 (Table 19). A study of six other Myakka soils in Florida showed that 

 BaCl -TEA extractable acidity in the spodic horizons averaged 



