62 FUNDAMENTALS OF AGRICULTURE. 



vide a good drainage. Then make a foundation with 

 a layer of earth. On top of this place a layer of 

 leaves and manure, then a layer of earth, another layer 

 of leaves and manure, a layer of earth, etc. The top 

 of the compost should be covered with earth and 

 shaped to shed water. Keep the compost pile moist 

 so as not to lose nitrogen which will escape as am- 

 monia. The manure, leaves and any other fertilizing 

 material that may be used, will decay due to the action 

 of bacteria. The same changes will take place in a 

 compost as in the soil, when the compost is kept thor- 

 oughly moist. Before applying any of the compost 

 to the land mix it well. The earth is used in layers to 

 absorb the ammonia that is set free in the process of 

 decay of the organic materials. The amount of fer- 

 tilizing material obtained from a compost will be equal 

 to the amount of fertilizing material added to it, pro- 

 vided there is no loss; but the availability of the fer- 

 tilizing material will be greater. 



EXERCISE. Have the pupils bring some sand, clay and farm 

 manure to the classroom. Also four tomato cans. Mix some sand 

 and farm manure together and also mix some clay and farm manure. 

 Punch holes in the bottom of the tomato cans. Fill each can three- 

 quarters full of the following: i. Sand. 2. Mixed sand and farm 

 manure. 3. Mixed clay and farm manure. 4. Clay. Pour an equal 

 quantity of water in the four cans. Which soil holds the water the 

 longest? In which can does the water pass through the quickest? 

 How does the mixture of farm manure with the sand and the clay 

 help these soils? Record the time it takes for the water to begin 

 to pass through each can. 



SECTION XII. COMMERCIAL FERTILIZERS. 



Commercial fertilizers, sometimes called artificial 

 manures, are those which are manufactured and sold 

 on our markets to furnish food for the plant. 



The Essential Elements. The chief function of fer- 

 tilizers is to supply those elements which the crops 

 have taken away from the land and which are neces- 

 sary for producing profitable crops: namely, nitrogen, 



