150 



approximately 21 mg/pot of S. This value should represent total avail- 

 able and mineralized S during the 16-week period of the experiment. 

 It would be equivalent to approximately 9 kg/ha of S in the top 15 cm 

 of soil in the field. This value was used in Fig. 17 but would probab- 

 ly be higher during an entire growing season under field conditions. 



