SOIL COMPOSITION 



First, in comparison with the average composition of the earth's 

 crust, and as a good basis of comparison for all other soils, let us 

 consider the total nitrogen, phosphorus, and potassium in the 

 unmanured land on the Rothamsted Experiment Station at Har- 

 penden, England. In 2 million pounds (6f inches per acre) of the 

 surface soil where a four-year crop rotation of wheat, turnips, 

 barley, and clover (or beans) has been followed for 60 years, there 

 are found, in round numbers, 2500 pounds of nitrogen, 1000 pounds 

 of phosphorus, and 35,000 pounds of potassium. These are num- 

 bers worth keeping in mind. 



In Table 9 is given the composition of four different soils, of 

 which two (from Holland and Scotland) are extremely productive, 

 and the other two (from Germany and Maryland) are nonpro- 

 ductive soils from barren lands. 



The first is an analysis by Baumhauer of a fertile alluvial soil 

 near the Zuider Zee, and the second is Anderson's analysis of rich 

 wheat soil of Midlothian. 



The third analysis, by Johnson, is said to represent " the most 

 sterile soil in Bavaria," and the last, by Veitch, represents the 

 " barrens " of southern Maryland. 



TABLE 9. COMPOSITION OF SOILS 

 Pounds in 2 Million (per Acre about 6f Inches Deep) 



These analyses are given to show that the supply of plant food 

 in the soil is sometimes the great factor of difference between 

 productive and nonproductive land; but the fact should not be 

 overlooked that in other cases other factors may also be important 

 (as excess or deficiency of moisture, poor physical condition, 



