1922] WOOD A RD— SOIL FERTILITY 93 



of hot 10 per cent BaCla solution added a drop at a time from a 

 pipette. The solution was boiled for ten minutes, placed on the 

 steam bath for two or three hours, and then removed and allowed 

 to stand over night. The barium sulphate precipitate was then 

 filtered off, washed with cold distilled water, transferred to a 

 weighed porcelain crucible, ignited to a dull red in a muffle furnace, 

 cooled in a desiccator, and weighed. Blanks were determined 

 using the same reagents and adding the same quality of the same 

 sulphuric acid that was used in the determination. 



The loss on ignition was determined on samples which had 

 been used for determining moisture. The moisture was deter- 

 mined by heating 10 gm. of air dry soil in the oven for five or six 

 hours. Part of the samples were heated to 100° C. in an ordinary 

 oven and part of them to 35° C. in a vacuum oven. After weighing 

 for the moisture determination, the sample was placed in the 

 muffle furnace, heated to a dull red for an hour, cooled in a desic- 

 cator, and weighed. The loss on ignition was calculated as percent- 

 age of oven dry soil. Table I gives the results of the analytical 

 work on all the soils analyzed. Phosphorus, sulphur, and volatile 

 matter (loss on ignition) are reported as percentage of oven dry 

 soil. 



Sulphur is present in the soil either in the form of sulphates of 

 calcium, magnesium, and iron, or in the form of organic matter. 

 All the sulphates are quite soluble and are not readily adsorbed, 

 so that they are leached out rapidly and only small amounts are 

 present in the soil. On the other hand, the organic sulphur is 

 insoluble and remains in the soil until oxidized to sulphates. One 

 would expect, therefore, some sort of relation between the sulphur 

 content of the soil and the volatile matter (loss on ignition), which 

 is a rough method of determining the organic matter. The data 

 in table I, however, indicate only a general relation, and that only 

 when samples from the same soil type or closely related soil types 

 are compared. The soil samples from Wisconsin are from the 

 same soil type, but differ in amount of organic matter. There is 

 also a difference in content of sulphur, and the higher sulphur con- 

 tent is found in the sample with the higher content of organic mat- 

 ter. This is true for both surface soil and subsoil. The Michigan 



