55 



less nitrogen and one-fifth less phosphorus than virgin 

 soil of the same type on this farm. The yield during 

 the last eight years of the experiment has been 28 per 

 'cent, less than during the first eight years of the 24-year 

 period." 



In Saskatchewan six different soils which had been 

 under cultivation for a number of years were compared 

 to six virgin soils of the same type which adjoined or 

 surrounded the cropped land. This gives six com- 

 parisons of cropped and virgin land, showing the effect 

 of the present system of farming under actual field con- 

 ditions. The analyses reported were made by the De- 

 partment of Chemistry of the University of Saskatch- 

 ewan. 



TABLE XII. Losses in Plant-food elements in Saskatchewan Soils 

 through Present Methods of Soil Management. Pounds per 

 2,000,000 (0-6 2-3 inches.) 



Humus, the residual material from the decomposition 

 of organic matter in the soil, is rapidly dissipated when 

 humus-forming materials (organic matter) are not sup- 

 plied. Nitrogen in the soil is contained in the organic 

 matter and by decomposition of the latter is made avail- 



