109 



8. A GREENHOUSE EVALUATION OF SUBSOIL SULFUR 



8.1 CHEMICAL AND MINERALOGICAL PROPERTIES 

 OF SOILS STUDIED 



The surface horizons of the four soils used in this study con- 

 tained more than 50% fine or very fine sand (0.05-0.25 mm) and were 

 classified as fine sands (Table 19) . The texture, citrate-soluble Al 

 and Fe, and the mineralogy of the clay fractions of the surface (A) 

 and argillic (B) horizons were similar in the Orangeburg and Norfolk 

 soils. The argillic horizons of these soils contained almost three 

 times as much citrate-soluble Al and almost seven times more Fe than 

 the C horizon of the Lakeland soil. Citrate-soluble Fe was very low 

 in the spodic horizon of the Myakka while Al was near that found in 

 the argillic horizons of the Ultisols. The previous study showed that 

 soluble Al and Fe were significantly correlated with extractable S and 

 total soil S in the surface horizons of Ultisols. 



The clay fraction and kaolinite and gibbsite in the clay fraction 

 increased with depth in the two Ultisols. The two horizons of the 

 Lakeland soil were relatively uniform. The most obvious change in the 

 mineralogy of the Myakka soil from the A to B horizon was the presence 

 of a 2:1 intergrade mineral in the spodic horizon. 



The surface horizons of all these soils contained near immeasur- 

 able quantities of extractable sulfate 3 (Table 20) . These levels 

 would be considered below the critical levels for most crops growing 

 on these soils (Table 7) . Only the Orangeburg and Norfolk series con- 

 tained significant quantities of extractable 5 in the subsurface hori- 

 zons. Total S was highest in the A horizon of the Myakka because of 



