PLANT-FOOD MATERIALS IN SOILS 



97 



Table 19. — Average Yields and Composition of Water Ex- 

 tracts of Four Good and Four Poor Soils 



Crop Yields per Acre 



Corn, bushels 



Potatoes, bushels 



Water soluble salts in pounds per acre of surface 

 four feet 



Nitrogen 



Phosphoric acid 



Potash 



Lime 



Magnesia 



Good Soils 



64.3 

 213.2 



82 



192 



319 



1422 



576 



A somewhat similar result was obtained with two soils 

 contained in large tanks from which drainage water was 

 collected, and that have been under experiment for a num- 

 ber of years. Each tank holds about three and one-half 

 tons of soil. In 1915 tanks filled with soils of different types 

 were planted to corn. The yields of grain and stalks com- 

 bined are given in Table 20 and also the number of pounds 

 to the acre of plant nutrients in drainage water collected 

 during seven months from the same soil types kept bare 

 of vegetation. As only a trace of phosphoric acid was found 

 in the drainage that ingredient is not included in the table. 



Table 20. — Yields of Crop and Plant-Food Material in 

 Drainage Water from Two Soil Types 



