64 

 involved four soil series, two horizon sequences nested within each 

 series, and two S rates within each horizon sequence. Each treatment 

 was replicated four times. Four soils which represented a Spodosol, an 

 Entisol, and two Ultisols were collected from unfertilized sites near 

 cultivated fields or improved pastures. The four soils and their loca- 

 tions are listed below: 



Series Pedon location 



Myakka fine sand Beef Research Unit, 



(Aerie Haplaquod, sandy Alachua Co. 



siliceous, hyperthermic) 



Lakeland fine sand 16 km SW of Williston, 



(Typic Quartzipsamment , Levy Co. 



thermic, coated) 



Orangeburg fine sand A.R.E.C., Quincy, 



(Typic Paleudult, fine-loamy, Gadsden Co. 

 siliceous, thermic) 



Norfolk fine sand A.R.E.C., Quincy, 



(Typic Paleudult, fine-loamy, Gadsden Co. 

 siliceous, thermic) 



Bulk samples of soil were collected from the surface to 20 cm 

 and from the upper to 20 cm of the argillic and spodic horizon of the 

 Orangeburg, Norfolk, and Myakka soils. Soil was collected from the sur- 

 face to 20 cm and from the upper to 20 cm of the C horizon in the 

 Lakeland soil. Soil from each location and profile depth was air dried 

 and screened twice through a 4-mm stainless steel screen and once 

 through a 2-mm screen. Samples were collected for mechanical, chemical, 

 and mineralogical analysis. 



Mechanical analysis was by the Bouyoucos (1962) hydrometer method. 

 The less than 2 urn clay-size fraction from each horizon was separated 

 and prepared for X-ray diffraction for mineral identification by the 

 method outlined bv Jackson (1969). Citrate-dithionite soluble Fe and 



