PROBLEM OF CROP PRODUCTION 375 



338. The Use of Manures. Land cropped continuously 

 to wheat for fifty-five years in England produced an 

 average yield of 12.9 bushels per acre, while in a nearby 

 field the wheat in a rotation that was heavily fertilized 

 gave an average of 35.5 bushels. 



In Illinois, as was stated previously, land continuously 

 cropped to corn for twenty-nine years produced an aver- 

 age of 27 bushels per acre, in a rotation of corn and oats, 

 46 bushels and in a rotation of corn, oats and clover, 58 

 bushels per acre. In the latter rotation when the land 

 was manured the yield was 81 bushels, and when man- 

 ured and given commercial fertilizers as well, the yield 

 was 96 bushels of shelled corn per acre. 



At the present time we cannot get such large increases 

 from the use of either manures or commercial fertilizers, 

 although we can and do get good returns from the intel- 

 ligent use of manure, even on our new soils. 



In this connection a definite statement regarding the 

 amount of the more important food elements in western 

 soils and the actual results of the application of manures 

 and fertilizers to them may not be out of place. 



In the surface 6 2/3 inches of the normal Saskatchewan 

 soils so far analyzed by the Department of Chemistry of 

 the Provincial University, the nitrogen supply ranges 

 from 3,000 to 14,000 pounds, the phosphorous from 1,000 

 to 3,000 pounds, and the potassium supply from 14,000 

 to 45,000 pound's. Assuming that the straw were all 

 returned to the land, the amount of these elements re- 

 moved' from the soil in the production of one bushel of 

 wheat would be 1 2-5 pounds of nitrogen, 1-5 pound of 

 phosphorus and about 1-5 of a pound of potassium. 



It is, therefore, apparent that if all of this plant food 

 could be utilized by crops without loss, there is enough 



