119 

 17.5 meq/lOOg with a base saturation of only 4% (Calhoun et al. , 1974: 

 Carlisle et al. , 1978) . 



8.2.2.2 Lakeland 



The sorghura-sudangrass also responded to S applications on the 

 Lakeland soil at the second harvest; S increased yields over 300% at 

 the third harvest. The yield difference due to horizon sequence was 

 significant at the 0.01 level of probability in the second harvest but 

 not significant in subsequent harvests. As previously mentioned, the 

 C horizons of Entisols are easily penetrated by plant roots. Roots 

 were well-distributed in soil from this horizon when the experiment was 

 terminated. The small quantity of available sulfate S present was 

 inadequate for optimum yields but sufficient to create a significant 

 difference in yield between horizon sequences. Sulfur uptake indicated 

 that this available S was equivalent to 0.5 to 1.1 mg/pot (or 0.08 to 

 0.17 ppm) . The turbidimetric method of determining S in the soil ex- 

 tracts was not sensitive enough to detect such subtle differences which 

 may or may not have been present in the soil. There were no signifi- 

 cant yield differences due to horizon sequence in the third and fourth 

 harvests and no S uptake differences; this indicated that available 

 subsoil S was rapidly depleted during the second 4 weeks of growth. 



8.2.2.3 Orangebarg and Norfolk 



Sulfur fertilization did not increase yields of plants growing in 

 the Orangeburg or Norfolk soils until the third harvest (Tables 22 and 

 23). In the Orangeburg soil, S fertilization increased the total dry 

 matter yields by 43% where no argillic horizon was present and by only 

 28% where the B horizon was included in the horizon sequence (Fig. 10). 

 In the Norfolk soil, these differences were 62% without the B horizon 



