REFERENCES 111 



SUGGESTIONS 



1. The study of the nature of soils can be made most interesting 

 and profitable, if the pupils are taken on a soil excursion. A spade 

 or soil auger should be taken along. Note which is the lighter in 

 color, the surface soil or the subsoil. Note, too, which contains the 

 greater amount of humus, and how far down the roots of different 

 plants extend. 



2. To show the action of capillary water, fill three lamp chimneys, 

 one with fine sand, another with clay, and the third with gravel. 

 Press down the soil somewhat with a stick. Tie cheesecloth over 

 the top of each chimney, and invert them in a shallow dish of water. 

 Note how rapidly the water rises in each. Explain the reason for 

 this difference. 



3. To show that soil contains air, throw a small handful into a 

 glass of water and watch the air bubbles rise. To measure the exact 

 amount of the soil air, fill a quart jar with the soil to be measured. 

 From another jar add water slowly until no more will be absorbed. 

 The water takes the place of the soil air. Find the per cent of soil air. 



4. To show that soil water contains plant food, take a glassful of 

 clear water from a ditch or pond and evaporate it for several days on 

 a fairly warm part of the stove. Do you notice a deposit on the side 

 of the glass ? What is it ? 



REFERENCES 



Fertility of the Soil. Roberts. 



Soils. Burkett. 



Soils and Crops of the Farm. Morrow and Hunt. 



The Fertility in Illinois Soils. Bulletin No. 123. 



Soils. Minnesota Bulletin No. 41. 



Humus in Its Relation to Soil Fertility. Year Book, 1895. 



The Storage and Use of Soil Moisture. Nebraska Bulletin No. 140. 



Farmers' Bulletins. Washington, D. C. 



245. Renovation of Worn-out Soils. 



524. Tile Drainage on the Farm. 



