03 



Al was determined on samples from every soil and horizon. Sodium pyro- 

 phosphate extractable re and Al were determined only on the Myakka 

 soil (Jackson, 1969). 



A pH-buffer curve was determined on soil from the surface horizon 

 by adding increasing increments of CaO to given weights of soil. The 

 limed samples were moistened with demineralized water, mixed well, and 

 allowed to air dry. This was repeated three times during a two-week 

 period. At the end of 2 weeks, the soil pH was determined in a 1:1 

 soil:water ratio. The soil pH-buffer curves of the four soils are 

 shown in Fig. 5. 



A mixture of CaO and MgO (1.4:1 ratio) was added to raise the soil 

 pH of the surface horizons to near 7.0. Lime was mixed with the bulk 

 soil in a mechanical, cement mixer. The soil was moistened with dis- 

 tilled water, allowed to equilibrate in plastic bags for 1 week, air 

 dried, and screened again. A basic N, P, K, and micronutrient mix was 

 added to all surface soils (Table 8). Two rates of S, and 20 ppm S, 

 were applied as reagent-grade CaS0,>2H 0, and the soil was mixed 

 again. The S treatment was inadvertently omitted from the Lakeland 

 soil. The error was noticed after the first harvest of plants in the 



greenhouse, and the appropriate rate of S as CaSO • 2H was added in 



4 2 



solution. 



Polyvinyl chloride (PVC) pipe with a diameter of 15.2 cm (6 in.) 

 was cut into 5C-cm sections for use as containers for the bioassay. 

 The pipe was thoroughly cleaned and rinsed with distilled water. A 

 plastic bag, perforated at the bottom for drainage, was fitted over 

 the lower end of each pipe section. Each section was placed in a 

 20.3-cm (8 in.) plastic saucer for support and drainage. 



