i8 



CHEMICAL FERTILIZERS 



this must be put down to the basic slag, as it alone is respon- 

 sible. As phosphatic manures are hardly lost by drainage 

 to any appreciable extent, the phosphates are only removed 

 from the soil in the form of crops or stock. Smetham some 

 years ago gave an interesting account of the income and 

 expenditure of phosphates in the British Isles, and showed 

 that the country was not really gaining in phosphates, in 

 spite of the large applications that had been made, and it 

 follows that it is urgently necessary that phosphatic manure 

 should be pushed ahead very rapidly, so as to make allowance 

 for increased population and increased crop production. 

 When phosphatic manures are used at the rate of i cwt. 

 high-grade basic slag per acre per annum the soil is steadily 

 gaining in phosphates. 



TABLE 2. 



COMPARATIVE RESULTS OF DIFFERENT ELEMENTS OF PLANT FOOD ON 

 THE GROWTH OF BARLEY AT ROTHAMSTED. 



TABLE 3. 



COMPARATIVE RESULTS OF DIFFERENT ELEMENTS OF PLANT FOOD ON 

 THE GROWTH OF BARLEY AT ROTHAMSTED. 



Yield of straw (pounds per acre). 



