io6 



AGRICULTURE 



Fillers in fertilizers. A full ton of the mixture is not 

 always needed to afford the desired amount of plant-food. 

 If a full ton having the given percentage composition is 

 wanted, add the necessary amount of some worthless mate- 

 rial, such as ground stone or cinders. Such worthless addi- 

 tions to fertilizers are called fillers. If manufacturers add 

 them it is for the purpose of making a fertilizer that they 

 can afford to sell at a low price. To avoid buying and 

 hauling useless filler, use only the highest grades of manu- 

 factured fertilizers. These are higher in price, but gener- 

 ally furnish nitrogen, phosphoric acid, and potash at a 

 lower cost per pound than do low-grade, cheap fertilizers. 

 In choosing fertilizers, select that one in which a pound of 

 plant-food costs the least. 



COMPOSITION OF FERTILIZERS 



EXERCISE. Copy in your notebook the two examples given in this 

 section and understand them so that you can work similar examples 

 on the blackboard, or for some farmer. 



NOTE TO THE TEACHER. If the sixth grade studies agriculture, this 

 section may be omitted. It should be required, together with the ad- 

 ditional problems, when the class in agriculture consists of the seventh 



