72 

 Soil samples were taken at the end of each growing season from 

 each plot. Samples were taken at depths of to 15 cm and 15 to 30 cm. 

 Samples were also taken at greater profile depths from those plots 

 receiving and 40 kg/ha S. These samples were air dried and screened 

 through a 2-mm sieve. Sulfate S was extracted with a 0.01 M 

 Ca(H ? P0, )„*2HJ0 solution and determined either turbidimetrically 

 (Massoumi and Cornfield, 1963; Chaudry and Cornfield, 1966) or by 

 indirect barium (Ba) absorption spectroscopy (Hue and Adams, 1979). An 

 estimate of total S was made on samples from 1978. 



Stolon-root samples of bahiagrass were collected in the fall of 

 1979 from the and 40 kg/ha S plots at the Beef Research Unit. These 

 were carefully washed, rinsed three times with distilled water, dried, 

 weighed, and ground. Total N and S were determined on the tissue. 



5. LABORATORY ANALYSES 

 5.1 NITROGEN 

 5.1.1 Total Nitrogen in Plant Tissue 



Plant tissue for N determination was dried and ground twice to 

 pass a 1-mm screen. Digestion was in an aluminum digestion block simi- 

 lar to the one described by Gallaher et al . (1975). The reagents and 

 procedure were from Nelson and Sommers (1973). A 0.2 g sample of tis- 

 sue was weighed into pyrex tubes. A 1.1-g scoop of a K ? S0, -CuSO^Se 



salt-catalvst mixture and 4 ml of concentrated H_,SG, were added to each 



1 4 



sample. A small glass funnel was placed in the top of tubes to ensure 

 efficient refluxing of the sample. Samples were placed on a preheated 

 digestion block at 375 C and digested for 1.5 hours after the solution 

 cleared. The digested sample was cooled and quantitatively transferred 

 to micro-Kjeldahl flasks with demineralized water. Ammonium in the 



