THE SOIL 



47 



oils; in some types, particularly muck and peat, it is 

 requently lacking and must therefore be supplied if 

 aaximum yields are to be obtained. In normal soil, 

 Lowever, it is seldom lacking. Nitrogen and phosphorus 

 in the other hand are very frequently deficient, and 

 hey are, therefore, among the most common world-wide 

 oil problems. 



35. The Essential Elements in Saskatchewan Soils. — 

 ^n the table that follows is given the average content 

 [u Saskatchewan 

 soils of five es- 

 sential elements. 

 The figures re- 

 ported represent 

 the averages of 

 the analyses 

 oaade by the 

 Department of 

 Chemistry of the 

 University of 

 S askatchewan, 

 of 16 samples of 

 soil, 8 being vir- 

 gin prairie soils. 

 The plowed acre 

 taken to a depth 

 of 6, 2/3 inches 

 is taken to weigh 

 2,000,000 pounds, the analyses being computed on this 



basis. 



The second column of figures indicates the amounts 

 of these elements required to produce 30 bushels of wheat 

 including both grain and straw. Knowing the soil con- 



Fig. 19. — Pot Cultures. 



Showing the effect of the presence and ab- 

 sence of plant foods: N. nitrogen; P. phos- 

 phorus; K. potassium. Note that inoculated 

 clover grows normally without commercial nitro- 

 gen, the plants securing their supply from the 

 air Without inoculation or commercial nitrogen 

 the plants fail. — Courtesy Illinois Agricultural 

 Experimental Station. 



