6. THE IDEAL SOIL. 



Illustrative material: Jars or boxes containing black garden 

 loam, clay, and sand. Mix a small proportion of sand with the 

 clay to make a clay loam. Mix a large proportion of sand with 

 the clay to make a sandy loam. Pour water on each kind of 

 soil, and have the pupils note how rapidly it soaks through in 

 each case and also the effect after it has dried. 



Soil a Reservoir for Water. We learned from Lesson 

 3 that plants transpire much water from their leaves, 

 water that has been taken up by their roots. The roots 

 must get from the soil as much water as they need or 

 the plants can not thrive. The soil receives its water 

 from rains and snows, and these fall at irregular intervals. 

 The ideal soil, therefore, must serve as a reservoir to 

 receive and hold enough of the rain and the snow water 

 to supply the needs of crops. 



Soil Must Be Porous We learned in Lesson 4 that 

 living cells require air as well as food. The live roots 

 of plants consist of living cells, not one of which can live 

 long without air. The ideal soil must, therefore, be 

 porous enough to admit all the air the roots require. 

 Rootlets will not grow in clumps or clods that are so 

 compact that air can not enter them. It seems strange 

 that the soil can supply the roots of plants with both water 

 and air at the same time. A soil in proper condition for 

 the rapid growth of roots may be compared to a wet 

 sponge with air circulating through its pores, while the 

 substance of the sponge contains much water. 



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