WHAT SOILS ARE BEST FOR AGRICULTURE? 239 



narrow spaces between the soil particles by capillary 

 action, and thus it is found in the soil not far from the 

 surface. 



The loose, porous structure of the soil allows a certain 

 amount of air to remain in the spaces. Plants breathe, 

 since they need the oxygen of the air just as much as we 

 do. And since the delicate roots of plants absorb air 

 as well as water, porosity of soil is very necessary for the 

 garden. 



Demonstration 3. What Types of Soil Favor Capillary Action? 



Materials. Lamp chimneys, four types of soil as in last experi- 

 ment, large shallow pan. 



Methods. Place equal amounts of different types of dry soil 

 in different chimneys. Pack the soil fairly tight. Set each chim- 



ney in a pan filled with water to a depth of an inch. Notice the 

 water rising in the different soils. In which soil does it rise fastest? 

 Highest? 



Conclusion. Which soil do you think is best adapted to carry 

 moisture? 



Effects of Cultivation on Soil. In order to keep the soil 

 from being packed too firm and hard, and thus prevent air 

 from passing into it readily, we cultivate, or break up, the 

 top layer of the soil either by hoeing, raking, and harrow- 

 ing, or by means of a cultivator. Cultivation crumbles 

 the soil and allows the plant roots to creep through it 

 more easily. It breaks up the soil particles so that water 

 can dissolve out the materials which the plants use for 



