THE ABSORPTION OF MINERAL ELEMENTS 



89 



The Composition op Ash of Some Agricultural Plants 



Because of the varying ash content and composition and the 

 different capacity of plants to feed upon slightly soluble soil 

 compounds, they naturally possess different requirements for soil 

 nutrients and require, therefore, different fertilizers. Potatoes, 

 for instance, need potash, and cereals need phosphorus. More- 

 over, in agricultural practice, various amounts of ash elements 

 are removed with the harvest, and, therefore, various crops 

 exhaust the soil to a different degree. The average quantities of 

 ash elements extracted from the soil by certain agricultural plants 

 are given in the following table, the figures indicating the number of 

 kilograms per hectare. 



The table shows that the highly cultivated crops, like potatoes 

 and legumes, exhaust the soil more than do the cereals and thus 



