1922] WOODARD—SOIL FERTILITY 91 



experiments were conducted in Indiana and Kentucky on the fields 

 from which the soil samples were taken. 



Soil analysis 



Methods of sampling. — The soil samples from Michigan and 

 Ohio (nos. 1-9) were taken by Dr. William Crocker and those 

 from Wisconsin (nos. lo-ii) by Mr. E. H. Hall. The samples 

 were taken in the usual way by means of a soil auger. The samples 

 from Indiana and Kentucky were taken when the soil was very 

 wet, and as only the surface soil was sampled, it was believed that 

 more accurate sampling could be done by using a spade or shovel. 

 Some soil was removed to a depth of seven inches, leaving one side 

 of the hole vertical, then a thin shce of soil was cut with the spade 

 to the full depth of seven inches. A narrow strip of this extending 

 from top to bottom was removed for the sample. Three or four 

 such samples from different parts of the field were taken and mixed 

 to form a composite sample. The samples from Indiana were 

 taken by John Woodard, except no. 18, which was taken by Mr. 

 V. G. Mann, and those from Kentucky by John Woodard, except 

 nos. 32-34, which were taken by Mr. J. C. Gentry. All the soil 

 samples were air dried, sifted through a 2 mm. sieve, and thoroughly 

 mixed. 



Analytical methods. — Phosphorus was determined according 

 to the official magnesium nitrate method of the Official Agricultural 

 Chemists. A blank determination was run to determine the 

 possible presence of phosphorus in the chemicals, but no phos- 

 phorus was found. 



Sulphur was determined by a modification of the methods of 

 Shedd and of Brown and Kellogg. In preliminary work it was 

 found that higher results were obtained when the iron and aluminum 

 were removed. In soils low in sulphur the barium sulphate pre- 

 cipitated very slowly, so, at the suggestion of Dr. Frederick 

 KocH,^ 10 cc. of approximately N/io H2SO4 was added immedi- 

 ately before heating the solution and adding the barium chloride. 

 This sulphuric acid was measured in a burette, and exactly the 



' Unpublished work of Dr. Frederick Koch. 



