CHAPTER XXVIII. 



MORE ABOUT FERTILIZERS. 



IN the past we believed that fertilizers acted 

 as plant foods and that the substances to be 

 applied must contain one or more of four 

 elements which are probably the most important 

 to the plant, namely: Nitrogen, phosphorus, 

 potassium and calcium. Several other elements 

 go to make up the plants; but these are con- 

 sidered most difficult for the plant to secure 

 from the soil and were therefore of the most 

 importance for the farmer. 



Trials, by experimental work with different 

 plants, soon showed that the forms of combina- 

 tion of these elements make a great difference. 

 For example, nitrogen is now appHed either in 

 the form of nitrate of soda and of potassiima, 

 which is called saltpetre, or in the form of sul- 

 phate of ammonia; or, it may be applied as or- 

 ganic matter in dried blood, tankage, hoof- and 

 horn-meal and even muck. 



Both the nitrate and sulphate forms are readily 

 dissolved, but the nitrate form is the one in 

 which plants take up their nitrogen, so that either 

 nitrate of soda or saltpetre is specially valuable 

 for forcing a quick growth. The effect may be 

 seen upon plants in a very few days after it is 



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