CHEMICAL COMPOSITION OF THE SOIL 



177 



usually deficient. Lime, as with other plant foods, also has an 

 influence. 



Examples of Interpretations of Soil Analyses. The following 

 examples are taken from Hilgard 1 . See accompanying table. 



Soils No. i and No. 2 are highly productive, and No. 3 is a 

 very good soil. There is a great difference in the chemical com- 

 position. No. i, however, is a heavy clay soil, while Nos. 2 and 

 3 are sands, and hence need to contain less plant food. Plant 

 roots can also exercise their functions to the depth of three or 

 four feet in them, while in soil No. i, the roots rarely reach below 

 12 or 15 inches. Soils No. 4 and 5, almost worthless, are deficient 

 in phosphoric acid, and No. 4 is also deficient in lime. In addi- 

 tion, these soils are underlaid by an almost pure sand at the depth 

 of 12 inches. These facts are sufficient explanation of their 

 character. 



PERCENTAGE COMPOSITION OF SOILS. 



Soils Nos. 6 to 10 exhibit the effect of lime on the character of 

 the soil ; soils 7 an d 9 being rich in lime, the others being poor 

 in this ingredient. Soils 7 and 9 are very productive. Soil 7 

 shows the effect of a large amount of lime in overcoming a 

 deficiency in phosphoric acid, soils 6, 8 and 10, with more phos- 

 1 Tenth U. S. Census. 



